JP7170911B2 - Power semiconductor device and its manufacturing method - Google Patents

Description

The present disclosure relates to a power semiconductor device and its manufacturing method.

Japanese Patent Application Laid-Open No. 2014-11236 (Patent Document 1) includes a power semiconductor element such as an insulated gate bipolar transistor (IGBT), a DCB substrate, a heat dissipation base plate, an insert case, a bus bar, and lead wires. A power semiconductor device is disclosed. The DCB substrate is bonded to a heat dissipation base plate. A power semiconductor device is bonded to the DCB substrate. The insert case is joined to the base plate for heat dissipation and surrounds the power semiconductor element and the DCB substrate. A bus bar is provided in the insert case. The power semiconductor element is electrically connected to the busbar via lead wires. Specifically, one end of the lead wire is joined to the power semiconductor element using solder. The other end of the lead wire is joined to the busbar using solder.

JP 2014-11236 A

An object of the present disclosure is to improve the reliability of power semiconductor devices.

A power semiconductor device of the present disclosure includes a substrate, a first power semiconductor element, lead wiring, and plate-like terminals. The first power semiconductor element includes a first back electrode joined to the substrate and a first front electrode opposite to the first back electrode. The plate-shaped terminal includes a first terminal portion and a second terminal portion. The first terminal portion is joined to the first front electrode using a first conductive joining member. The second terminal portion is joined to the lead wire using a second conductive joining member. A first linear expansion coefficient difference between the first power semiconductor element and the first terminal portion is larger than a second linear expansion coefficient difference between the lead wire and the second terminal portion. The first terminal portion is thinner than the second terminal portion.

A method of manufacturing a power semiconductor device according to the present disclosure includes joining a first back electrode of a first power semiconductor element to a substrate, and connecting a plate-like terminal to the first power semiconductor element on the side opposite to the first back electrode. 1 bonding to the front surface electrode and the lead wiring. The plate-shaped terminal includes a first terminal portion and a second terminal portion. A first difference in coefficient of linear expansion between the first power semiconductor element and the first terminal portion is larger than a second difference in coefficient of linear expansion between the lead wire and the second terminal portion. The first terminal portion is thinner than the second terminal portion. While the first terminal portion is joined to the first front electrode using the first conductive joining member, the second terminal portion is joined to the lead wire using the second conductive joining member. When joining the first terminal portion to the first front surface electrode, the first conductive joining member is heated using the first heat source. The first heat source is controlled based on a first temperature of the first terminal portion measured using a first temperature sensor. When joining the second terminal portion to the lead wire, the second conductive joining member is heated using the second heat source. The second heat source is controlled based on a second temperature of the second terminal portion measured using a second temperature sensor.

Since the first terminal portion is thinner than the second terminal portion, thermal stress applied to the first conductive joining member can be reduced. The first conductive joining member is prevented from cracking and the first terminal portion is prevented from being separated from the first front surface electrode. Furthermore, the second terminal portion is thicker than the first terminal portion. The second terminal portion has a larger heat capacity than the first terminal portion. Therefore, the temperature rise of the second conductive joining member can be reduced. Degradation of the second conductive joining member is reduced. According to the power semiconductor device of the present disclosure, reliability of the power semiconductor device can be improved. According to the method of manufacturing a power semiconductor device of the present disclosure, a power semiconductor device with improved reliability can be obtained.

1 is a schematic cross-sectional view of a power semiconductor device according to Embodiment 1; FIG. 4 is a diagram showing a flowchart of a method for manufacturing a power semiconductor device according to Embodiment 1; FIG. 4 is a diagram showing a flowchart of step S4 of the method for manufacturing the power semiconductor device according to Embodiment 1; FIG. 1 is a schematic diagram showing a first example of a power semiconductor device manufacturing apparatus according to a first embodiment; FIG. 1 is a block diagram of a first example and a second example of a power semiconductor device manufacturing apparatus according to Embodiment 1; FIG. 4 is a schematic diagram showing a second example of the power semiconductor device manufacturing apparatus according to the first embodiment; FIG. 3 is a schematic cross-sectional view of a power semiconductor device according to Embodiment 2; FIG. 10 is a schematic cross-sectional view of a power semiconductor device according to Embodiment 3; FIG.

Embodiments of the present disclosure will be described below. In addition, the same reference numerals are given to the same configurations, and the description thereof will not be repeated.

Embodiment 1.
A power semiconductor device 1 according to a first embodiment will be described with reference to FIG. The power semiconductor device 1 mainly includes a substrate 10, a first power semiconductor element 20, lead wirings 41 and 41g, and plate-like terminals 50 and 50g. The power semiconductor device 1 may further include a terminal block 40 and a heat sink 30 . The power semiconductor device 1 may further include a second power semiconductor element 25 .

The substrate 10 includes an insulating layer 11 , a front conductor layer 12 and a back conductor layer 13 . The substrate 10 extends along a first direction (x direction) and a second direction (y direction) orthogonal to the first direction. A third direction (z direction) perpendicular to the first direction (x direction) and the second direction (y direction) is the thickness direction of the substrate 10 .

The insulating layer 11 is, for example, a ceramic layer such as aluminum nitride (AlN), silicon nitride _{( Si3N4} ) _, alumina ( _Al2O3 ), or an epoxy resin containing boron nitride (BN) filler. It is a resin layer. The insulating layer 11 preferably has electrical insulation and high thermal conductivity. The insulating layer 11 has a thickness of 0.3 mm or more and 1.0 mm, for example.

The front conductor layer 12 and the back conductor layer 13 are, for example, a copper (Cu) layer, an aluminum (Al) layer, or a laminate of Cu and Al. The front conductor layer 12 and the back conductor layer 13 each have a thickness of 0.2 mm or more, for example. Each of the front conductor layer 12 and the back conductor layer 13 may have a thickness of 0.3 mm or more. The front conductor layer 12 and the back conductor layer 13 each have a thickness of 1.0 mm or less, for example. Each of the front conductor layer 12 and the back conductor layer 13 may have a thickness of 0.6 mm or less. As the thickness of the front conductor layer 12 and the back conductor layer 13 increases, the heat dissipation performance of the front conductor layer 12 and the back conductor layer 13 increases. The thinner the front conductor layer 12 and the back conductor layer 13, the greater the difference in the linear expansion coefficient between the insulating layer 11 and the front conductor layer 12 and the linear expansion coefficient between the insulating layer 11 and the back conductor layer 13. Due to the difference, the thermal stress applied from the front conductor layer 12 and the back conductor layer 13 to the insulating layer 11 is reduced. The front surface of the front conductor layer 12 is the main surface 10 a of the substrate 10 .

The first power semiconductor element 20 and the second power semiconductor element 25 are arranged adjacent to each other in the first direction (x direction). In this embodiment, the first power semiconductor element 20 and the second power semiconductor element 25 are made of silicon (Si). The first power semiconductor element 20 and the second power semiconductor element 25 may be made of a semiconductor material having a larger bandgap than Si, such as silicon carbide (SiC), gallium nitride (GaN), or diamond. A semiconductor material having a bandgap larger than that of Si enables the first power semiconductor element 20 and the second power semiconductor element 25 to operate normally even at high temperatures, and enables miniaturization of the power semiconductor device 1. .

The first power semiconductor element 20 includes a first rear surface electrode 22 and a first front surface electrode 21 opposite to the first rear surface electrode 22 . The first back surface electrode 22 and the first front surface electrode 21 are separated from each other in the thickness direction (third direction (z direction)) of the first power semiconductor element 20 . Second power semiconductor element 25 includes a second back surface electrode 27 and a second front surface electrode 26 opposite to second back surface electrode 27 . The second back surface electrode 27 and the second front surface electrode 26 are separated from each other in the thickness direction (third direction (z direction)) of the second power semiconductor element 25 . The thickness direction (third direction (z direction)) of the first power semiconductor element 20 and the thickness direction (third direction (z direction)) of the second power semiconductor element 25 are normal to the main surface 10a of the substrate 10. parallel to the direction (third direction (z direction)).

In this embodiment, the first power semiconductor element 20 is an insulated gate bipolar transistor (IGBT), and the second power semiconductor element 25 is a freewheeling diode (FWD). The first front electrode 21 includes an emitter electrode (not shown) and a gate electrode (not shown), and the first back electrode 22 is a collector electrode. The second front electrode 26 is an anode electrode. The second back electrode 27 is a cathode electrode. The first power semiconductor device 20 and the second power semiconductor device 25 may be other power semiconductor devices such as metal oxide semiconductor field effect transistors (MOSFETs).

The first back electrode 22 of the first power semiconductor element 20 is joined to the front surface conductor layer 12 of the substrate 10 using a conductive joining member 23 . A second back electrode 27 of the second power semiconductor element 25 is joined to the front surface conductor layer 12 of the substrate 10 using a conductive joining member 28 . The conductive joint member 23 and the conductive joint member 28 are made of, for example, solder such as lead-free solder, silver (Ag), copper (Cu), or copper-tin (CuSn) alloy. The conductive joint member 23 and the conductive joint member 28 have a melting point of, for example, 250° C. or higher. The conductive joint member 23 and the conductive joint member 28 may have a melting point of 300° C. or higher.

The conductive joint member 23 and the conductive joint member 28 may be made of metal fine particle sintered body such as silver fine particle sintered body, copper fine particle sintered body or CuSn fine particle sintered body. Microparticles, as used herein, refer to particles having a diameter of 100 μm or less. Microparticles may be particles having a diameter of 10 μm or less, or may be nanoparticles. A metal fine particle sintered body is obtained by sintering a paste in which metal fine particles are dispersed, utilizing the phenomenon that the metal fine particles are sintered at a temperature lower than the melting point of the metal that constitutes the fine particles. The metal fine particle sintered body thus obtained has the melting point of the metal forming the fine particles, which is higher than that of solder. The metal fine particle sintered body enables the first power semiconductor element 20 and the second power semiconductor element 25 to operate normally even at high temperatures. The metal fine particle sintered body improves the reliability of the power semiconductor device 1 and enables miniaturization of the power semiconductor device 1 .

A first metallization layer (not shown) suitable for diffusion bonding with the first conductive bonding member 55 may be provided on the first front surface electrode 21 . A second metallization layer (not shown) suitable for diffusion bonding with the third conductive bonding member 56 may be provided on the second front electrode 26 . When the first conductive joint member 55 and the third conductive joint member 56 are solder, the first metallized layer and the second metallized layer are, for example, a gold (Au) layer and a nickel (Ni) layer from the outermost surface side. are laminated. The Au layer prevents oxidation of the outermost surfaces of the first front electrode 21 and the second front electrode 26 and improves wettability with solder. The Ni layer prevents solder from diffusing to the first front electrode 21 and the second front electrode 26 . The thickness of the Ni layer is determined in consideration of the mode of heat application during soldering and the maximum temperature during operation of the first power semiconductor element 20 and the second power semiconductor element 25 . The Ni layer has a thickness of, for example, 1.5 μm or more and 5.0 μm or less. The Ni layer is formed by sputtering or plating, for example.

The lead wiring 41 and the plate-like terminal 50 electrically connect the first power semiconductor element 20 and the second power semiconductor element 25 to members outside the power semiconductor device 1 . A current or voltage is supplied from a member outside the power semiconductor device 1 to the first power semiconductor element 20 and the second power semiconductor element 25 through the lead wiring 41 and the plate-like terminal 50, or the first power Power is supplied from the semiconductor element 20 and the second power semiconductor element 25 to members outside the power semiconductor device 1 . A member outside the power semiconductor device 1 is, for example, a motor, and the power semiconductor device 1 is, for example, an inverter that drives the motor. When driving the motor, a current of several hundred amperes flows through the lead wire 41 and the plate-like terminal 50 .

The lead-out wiring 41 and the plate-like terminal 50 are each formed of copper (Cu), a copper-tungsten (CuW) alloy, or a laminate composed of a Cu layer/Invar (Fe-36% Ni alloy) layer/Cu layer. It is In this embodiment, the lead wire 41 and the plate-like terminal 50 are made of the same material. The lead wiring 41 and the plate-like terminal 50 may be made of different materials.

The lead wire 41 mainly extends in the second direction (y direction), and the longitudinal direction of the lead wire 41 is the second direction (y direction). The plate-like terminal 50 mainly extends in a first direction (x-direction) intersecting with the lead wiring 41, and the longitudinal direction of the plate-like terminal 50 is the first direction (x-direction).

Plate-like terminal 50 includes a first terminal portion 51 and a second terminal portion 52 . The plate-like terminal 50 may further include a third terminal portion 53 connecting the first terminal portion 51 and the second terminal portion 52 . In this embodiment, the first terminal portion 51, the second terminal portion 52, and the third terminal portion 53 are made of the same material, and the plate-like terminal 50 is constructed as a single component. The plate-shaped terminal 50 configured as a single component has a first terminal portion 51, a second terminal portion 52, and a third terminal portion 53 which are separate components, and the first terminal portion 51 and the second terminal portion 51 are separated from each other. Compared to the plate-like terminal 50 formed by connecting the second terminal part 52 and the third terminal part 53 together, for example by soldering or welding, while the parts 52 are connected to each other by soldering or welding, for example. Reliable.

The plate-like terminal 50 may be composed of a plurality of parts. For example, the first terminal portion 51, the second terminal portion 52, and the third terminal portion 53 are separate parts, and the first terminal portion 51 and the second terminal portion 52 are connected to each other, for example, by soldering or welding. Together, the second terminal portion 52 and the third terminal portion 53 may be connected together, for example, by soldering or welding. Therefore, even if the plate-like terminal 50 has a complicated shape such as a crank shape in plan view from the thickness direction (third direction (z direction)) of the substrate 10, the plate-like terminal 50 is It can be formed with relatively high yield and relatively low cost. When the first terminal portion 51, the second terminal portion 52, and the third terminal portion 53 are separate parts, the first terminal portion 51, the second terminal portion 52, and the third terminal portion 53 are made of the same material. , or may be made of different materials.

The first terminal portion 51 extends in the first direction (x direction), and the longitudinal direction of the first terminal portion 51 is the first direction (x direction). The first terminal portion 51 extends along the major surface 10 a of the substrate 10 . The second terminal portion 52 extends in the first direction (x direction), and the longitudinal direction of the second terminal portion 52 is the first direction (x direction). The second terminal portion 52 extends along the major surface 10 a of the substrate 10 . The third terminal portion 53 extends in the third direction (z direction), and the longitudinal direction of the third terminal portion 53 is the third direction (z direction). The third terminal portion 53 extends along the thickness direction (third direction (z direction)) of the first power semiconductor element 20 . The distance between the first terminal portion 51 and the main surface 10a of the substrate 10 in the thickness direction (third direction (z direction)) of the first power semiconductor element 20 is the thickness direction of the first power semiconductor element 20 ( shorter than the distance between the second terminal portion 52 and the principal surface 10a of the substrate 10 in the third direction (z direction).

The first terminal portion 51 is thinner than the second terminal portion 52 . Specifically, the ratio of the first thickness t ₁ of the first terminal portion 51 to the second thickness t ₂ of the second terminal portion 52 is 0.75 or less. This ratio may be 0.60 or less. The ratio of the first thickness t ₁ of the first terminal portion 51 to the second thickness t ₂ of the second terminal portion 52 is 0.10 or more. This ratio may be greater than or equal to 0.20. The third terminal portion 53 is thinner than the second terminal portion 52 . Specifically, the ratio of the _third thickness t3 of the third terminal portion 53 to the _second thickness t2 of the second terminal portion 52 is 0.75 or less. This ratio may be 0.60 or less. The ratio of the _third thickness t3 of the third terminal portion 53 to the _second thickness t2 of the second terminal portion 52 is 0.10 or more. This ratio may be greater than or equal to 0.20.

The first thickness t ₁ of the first terminal portion 51 is 0.60 mm or less. The first thickness t ₁ may be 0.50 mm or less. The first thickness t ₁ of the first terminal portion 51 is, for example, 0.15 mm or more. The first thickness t ₁ may be 0.20 mm or more. The second thickness t ₂ of the second terminal portion 52 is, for example, 0.80 mm or more. The _second thickness t2 may be 1.0 mm or more. The second thickness t ₂ of the second terminal portion 52 is, for example, 1.50 mm or less. The second thickness t ₂ of the second terminal portion 52 may be 1.35 mm or less. A third thickness t ₃ of the third terminal portion 53 is, for example, 0.60 mm or less. The _third thickness t3 may be 0.50mm or less. A third thickness t ₃ of the third terminal portion 53 is, for example, 0.15 mm or more. The _third thickness t3 may be 0.20 mm or more. The third thickness t ₃ of the third terminal portion 53 may be equal to the first thickness t ₁ of the first terminal portion 51 .

A first linear expansion coefficient difference between the first power semiconductor element 20 and the first terminal portion 51 is larger than a second linear expansion coefficient difference between the lead wire 41 and the second terminal portion 52 . A third linear expansion coefficient difference between the second power semiconductor element 25 and the first terminal portion 51 is larger than a second linear expansion coefficient difference between the lead wire 41 and the second terminal portion 52 .

The first power semiconductor element 20 and the second power semiconductor element 25 arranged adjacent to each other are both joined to one plate-like terminal 50 . Therefore, the wiring inductance can be reduced, and the surge voltage applied to the first power semiconductor element 20 and the second power semiconductor element 25 can be reduced. Also, the joining of the plate-like terminal 50 and the first power semiconductor element 20 and the joining of the plate-like terminal 50 and the second power semiconductor element 25 can be performed in one step. Productivity of the power semiconductor device 1 is improved.

Specifically, the first terminal portion 51 is joined to the first front electrode 21 using a first conductive joining member 55 . The second terminal portion 52 is joined to the lead wire 41 using a second conductive joining member 57 . The first terminal portion 51 is joined to the second front electrode 26 using a third conductive joining member 56 .

The second conductive joining member 57 may be made of the same material as the first conductive joining member 55 and the third conductive joining member 56, or may be made of a material different from that of the first conductive joining member 55 and the third conductive joining member 56. may be formed. The first conductive joint member 55, the second conductive joint member 57, and the third conductive joint member 56 are made of, for example, solder such as lead-free solder, silver (Ag), copper (Cu), or copper-tin (CuSn) alloy. It is The first conductive joining member 55, the second conductive joining member 57 and the third conductive joining member 56 have a melting point of 250° C. or higher. The first conductive joining member 55, the second conductive joining member 57, and the third conductive joining member 56 may have a melting point of 300° C. or higher.

Specifically, the first conductive joining member 55 is a first solder containing Sn as its main component. The first solder has a higher 0.2% proof stress than Sn. The first solder is, for example, Sn--Cu solder or Sn--Sb solder. The second conductive joining member 57 is a second solder containing Sn as its main component. The second solder has a higher thermal conductivity than Sn. The second solder is, for example, Sn—Au solder or Sn—Ag solder. The third conductive joint member 56 is made of a third solder containing Sn as its main component. The third solder has a higher 0.2% proof stress than Sn. The third solder is, for example, Sn--Cu solder or Sn--Sb solder. The first conductive joining member 55 and the third conductive joining member 56 have a 0.2% yield strength higher than that of the second conductive joining member 57 . The second conductive joining member 57 has higher thermal conductivity than the first conductive joining member 55 and the third conductive joining member 56 .

The first conductive joining member 55, the second conductive joining member 57, and the third conductive joining member 56 are formed of metal fine particle sintered bodies such as silver fine particle sintered bodies, copper fine particle sintered bodies, or CuSn fine particle sintered bodies. may A metal fine particle sintered body is obtained by sintering a paste in which metal fine particles are dispersed, utilizing the phenomenon that the metal fine particles are sintered at a temperature lower than the melting point of the metal that constitutes the fine particles. The metal fine particle sintered body thus obtained has the melting point of the metal forming the fine particles, which is higher than that of solder. The metal fine particle sintered body enables the first power semiconductor element 20 and the second power semiconductor element 25 to operate normally even at high temperatures. The metal fine particle sintered body improves the reliability of the power semiconductor device 1 and enables miniaturization of the power semiconductor device 1 .

The terminal block 40 is made of a heat-resistant insulating resin such as polyphenylene sulfide (PPS) or liquid crystal polymer (LCP). The thermal conductivity of the terminal block 40 is lower than the thermal conductivity of the lead wiring 41 and lower than the thermal conductivity of the plate-like terminal 50 . The thermal conductivity of the terminal block 40 is smaller than the thermal conductivity of the first power semiconductor element 20 and smaller than the thermal conductivity of the second power semiconductor element 25 . The thermal conductivity of the terminal block 40 is, for example, 1.0 W/mK or less. A portion of the lead wiring 41 is embedded in the terminal block 40 . The rest of the lead wiring 41 is exposed from the terminal block 40 . The second terminal portion 52 of the plate-shaped terminal 50 is joined to the portion of the lead wire 41 exposed from the terminal block 40 using a second conductive joining member 57 .

The lead-out wiring 41g is configured similarly to the lead-out wiring 41. As shown in FIG. The lead wire 41g extends in the second direction (y direction), and the longitudinal direction of the lead wire 41g is the second direction (y direction). A part of the lead wiring 41g is embedded in the terminal block 40 . The rest of the lead wiring 41 g is exposed from the terminal block 40 . The lead wiring 41g is electrically insulated from the lead wiring 41 by the insulating resin forming the terminal block 40 .

The plate-like terminal 50 g is configured in the same manner as the plate-like terminal 50 . The plate-like terminal 50g mainly extends in a first direction (x-direction) intersecting with the lead wiring 41g, and the longitudinal direction of the plate-like terminal 50g is the first direction (x-direction). One end of the plate-like terminal 50g is connected to the portion of the lead wire 41g exposed from the terminal block 40 via a conductive joint member (not shown). The other end of the plate-like terminal 50g is connected to the front conductor layer 12 of the substrate 10 via a conductive joint member (not shown).

The heat sink 30 dissipates the heat generated by the first power semiconductor element 20 and the second power semiconductor element 25 to the outside of the power semiconductor device 1 . The heat sink 30 is made of a material having high thermal conductivity, such as copper (Cu) or aluminum (Al). When applying the power semiconductor device 1 to an automobile, the heat sink 30 is preferably made of Al in order to reduce the weight of the automobile and improve fuel efficiency.

The heat sink 30 includes a top plate 31 , a plurality of heat radiation fins 32 and a jacket 33 . A flow path 36 for a coolant 37 is formed between the top plate 31 and the jacket 33 . The plurality of radiation fins 32 are attached to the back surface of the top plate 31 that defines a part of the flow path 36 and are arranged inside the flow path 36 . The top plate 31 and the jacket 33 are provided with an inlet 34 and an outlet 35 of the channel 36 . The coolant 37 is, for example, water. Coolant 37 flows from a radiator (not shown) to inlet 34 of channel 36 . Coolant 37 flows through channel 36 and out of outlet 35 of channel 36 to the radiator. A coolant 37 circulates through the radiator and heat sink 30 .

In order to prevent coolant 37 from leaking out of heat sink 30, top plate 31 is attached to jacket 33 in a liquid-tight manner. In a first example, a rubber O-ring may be interposed between the top plate 31 and the jacket 33 and the top plate 31 and the jacket 33 may be screwed together. In a second example, a sealing material may be applied between the top plate 31 and the jacket 33 and the top plate 31 and the jacket 33 may be screwed together. In a third example, the top plate 31 and jacket 33 may be brazed together. In a fourth example, the top plate 31 and jacket 33 may be friction stir welded together.

Substrate 10 is attached to heat sink 30 . Specifically, the back conductor layer 13 of the substrate 10 is attached to the top plate 31 of the heat sink 30 using the bonding member 14 . The joining member 14 is, for example, aluminum silicon (AlSi) brazing material or solder containing Sn as a main component. When Sn-based solder is used as the bonding member 14 and the heat sink 30 is made of Al, the heat sink 30 is provided with a plating layer (for example, a Ni-plated layer or a Sn-plated layer) that can form an alloy with the Sn-based solder. may be applied in advance to Since this plating layer is easily alloyed with Sn-based solder, it facilitates bonding of Sn-based solder and the heat sink 30 made of Al. This plated layer has a thickness of, for example, 2 μm or more and 10 μm or less, and achieves good solder wettability and high bonding reliability.

For example, when the heat sink 30 is made of Al, the linear expansion coefficient of the heat sink 30 is given by the linear expansion coefficient of Al (23 ppm/K). The substrate 10 has an insulating layer 11 formed of Si ₃ N ₄ having a thickness of 0.32 mm, a front conductor layer 12 formed of a Cu plate having a thickness of 0.50 mm, When the backside conductor layer 13 is formed of a Cu plate having a thickness of 0.50 mm, the coefficient of linear expansion of the substrate 10 is about 7 ppm/K or more and about 8 ppm/K or less. Therefore, the difference in coefficient of linear expansion between the substrate 10 and the heat sink 30 increases. When the linear expansion coefficient difference between the substrate 10 and the heat sink 30 is large, it is preferable to use a bonding member having a high 0.2% proof stress as the bonding member 14 . A joint member having a large 0.2% proof stress can reduce the crack growth rate (amount of crack growth per load cycle) of the joint member 14 .

Terminal block 40 is attached to heat sink 30 . Specifically, the terminal block 40 is attached to the top plate 31 of the heat sink 30 using a silicone adhesive or screws.

A method for manufacturing the power semiconductor device 1 according to the present embodiment will be described with reference to FIGS.
As shown in FIG. 2, the method for manufacturing the power semiconductor device 1 of the present embodiment includes bonding the first power semiconductor element 20 and the second power semiconductor element 25 onto the substrate 10 (S1). Specifically, the conductive bonding member 23 is used to bond the first rear surface electrode 22 of the first power semiconductor element 20 to the front surface conductor layer 12 of the substrate 10 . A conductive bonding member 28 is used to bond the second back electrode 27 of the second power semiconductor element 25 to the front conductor layer 12 of the substrate 10 .

As shown in FIG. 2, the method for manufacturing power semiconductor device 1 of the present embodiment includes attaching terminal block 40 to heat sink 30 (S2). Specifically, for example, the terminal block 40 is attached to the top plate 31 of the heat sink 30 using a silicone adhesive or screws. Parts of the lead wires 41 and 41g are embedded in the terminal block 40 . The rest of the lead wires 41 and 41g are exposed from the terminal block 40. As shown in FIG.

As shown in FIG. 2, the method for manufacturing power semiconductor device 1 of the present embodiment includes bonding substrate 10 to heat sink 30 (S3). Specifically, the bonding member 14 is used to attach the back conductor layer 13 of the substrate 10 to the heat sink 30 . The joining member 14 is, for example, aluminum silicon (AlSi) brazing material or solder containing Sn as a main component.

As shown in FIG. 2, in the method of manufacturing the power semiconductor device 1 of the present embodiment, the plate-like terminal 50 is joined to the first power semiconductor element 20, the second power semiconductor element 25 and the lead wiring 41 ( S4).

Specifically, as shown in FIG. 3, the first conductive joining member 55, the second conductive joining member 57, and the third conductive joining member 56 are respectively attached to the first front surface of the first power semiconductor element 20. It is placed on the electrode 21, on the portion of the lead wire 41 exposed from the terminal block 40, and on the second front surface electrode 26 of the second power semiconductor element 25 (S41). The first conductive joint member 55, the second conductive joint member 57, and the third conductive joint member 56 may use bulk solder material such as bar solder, plate solder, or sheet solder. By using a bulk solder material, the amount of solder can be precisely adjusted. The bulk solder material may be a fluxless solder material. By using a fluxless solder material, there is no need for a cleaning process for flux residue after soldering.

Then, the plate-like terminal 50 is placed on the first conductive joint member 55, the second conductive joint member 57 and the third conductive joint member 56 (S42).

Specifically, the plate-shaped terminal 50 includes a first terminal portion 51 and a second terminal portion 52 . The plate-like terminal 50 may further include a third terminal portion 53 connecting the first terminal portion 51 and the second terminal portion 52 . The first terminal portion 51 is thinner than the second terminal portion 52 . The third terminal portion 53 is thinner than the second terminal portion 52 . The plate-shaped terminal 50 is obtained, for example, by the following steps. A conductive metal plate having a uniform thickness is provided. Portions of the conductive metal plate corresponding to the first terminal portion 51 and the third terminal portion 53 are selectively etched. Then, the conductive metal plate is pressed. Thus, the plate-like terminal 50 including the first terminal portion 51, the second terminal portion 52 and the third terminal portion 53 is obtained.

The first terminal portion 51 rests on the first conductive joint member 55 and the third conductive joint member 56 . The second terminal portion 52 rests on the second conductive joining member 57 . The difference in the first coefficient of linear expansion between the first power semiconductor element 20 and the first terminal portion 51 is greater than the difference in the second coefficient of linear expansion between the lead wire 41 and the second terminal portion 52. . The difference in the third coefficient of linear expansion between the second power semiconductor element 25 and the first terminal portion 51 is greater than the difference in the second coefficient of linear expansion between the lead wire 41 and the second terminal portion 52. .

Then, the first conductive joint member 55, the second conductive joint member 57 and the third conductive joint member 56 are heated (S43). By heating the first terminal portion 51, the first conductive joining member 55 and the third conductive joining member 56 are heated, and by heating the second terminal portion 52, the second conductive joining member 57 is heated. may Specifically, the second conductive joining member 57 (or the second terminal portion 52) is heated while the first conductive joining member 55 and the third conductive joining member 56 (or the first terminal portion 51) are heated. More specifically, the first conductive joining member 55 and the third conductive joining member 56 (or The heating of the first terminal portion 51) is performed independently of the heating of the second conductive joining member 57 (or the second terminal portion 52).

The first conductive joint member 55, the second conductive joint member 57, and the third conductive joint member 56 are, for example, lead-free solder. Specifically, the first conductive joining member 55 is a first solder containing Sn as a main component. The first solder has a higher 0.2% proof stress than Sn. The first solder is, for example, Sn--Cu solder or Sn--Sb solder. The second conductive joining member 57 is a second solder containing Sn as its main component. The second solder has a higher thermal conductivity than Sn. The second solder is, for example, Sn—Au solder or Sn—Ag solder. The third conductive joining member 56 is a third solder containing Sn as its main component. The third solder has a higher 0.2% proof stress than Sn. The third solder is, for example, Sn--Cu solder or Sn--Sb solder. The first conductive joint member 55 and the third conductive joint member 56 each have a 0.2% yield strength higher than that of the second conductive joint member 57 . The second conductive joining member 57 has higher thermal conductivity than each of the first conductive joining member 55 and the third conductive joining member 56 .

When the first conductive joining member 55, the second conductive joining member 57 and the third conductive joining member 56 are solder such as lead-free solder, the first conductive joining member 55, the second conductive joining member 57 and the third conductive joining member The member 56 is, for example, a radiant heat system using infrared rays emitted from an infrared light source such as a halogen lamp (see FIGS. 4 and 5), or a heat transfer system using a heat block (see FIGS. 5 and 6). is heated by When the emissivity of the plate-like terminal 50 is 0.3 or more, the first conductive joining member 55, the second conductive joining member 57 and the third conductive joining member 56 ( The first terminal portion 51 and the second terminal portion 52) are heated. When the emissivity of the plate-like terminal 50 is less than 0.3, the first conductive joining member 55, the second conductive joining member 57 and the third conductive joining member 56 are connected by a heat transfer method (see FIGS. 5 and 6). (The first terminal portion 51 and the second terminal portion 52) are heated.

In a first example, the first conductive joining member 55, the second conductive joining member 57 and the third conductive joining member 56 are heated using the first heating device 60 shown in FIGS. The first heating device 60 includes a first heat source 61 , a second heat source 62 , a first temperature sensor 63 , a second temperature sensor 64 and a controller 65 .

The first heat source 61 is, for example, a first infrared heater. The second heat source 62 is, for example, a second infrared heater. The first heat source 61 heats the first terminal portion 51 of the plate-shaped terminal 50 to heat the first conductive joining member 55 and the third conductive joining member 56 . The second heat source 62 heats the second terminal portion 52 of the plate-like terminal 50 to heat the second conductive joining member 57 .

The first temperature sensor 63 is a first radiation thermometer. The second temperature sensor 64 is a second radiation thermometer. The first temperature sensor 63 is separated from the plate-like terminal 50 . The first temperature sensor 63 measures the first temperature of the first terminal portion 51 of the plate-like terminal 50 . The first temperature sensor 63 indirectly measures the temperature of the first conductive joint member 55 and the temperature of the third conductive joint member 56 . The second temperature sensor 64 is separated from the plate-shaped terminal 50 . A second temperature sensor 64 measures a second temperature of the second terminal portion 52 of the plate-like terminal 50 . The second temperature sensor 64 indirectly measures the temperature of the second conductive joining member 57 . Since the emissivity of the plate-shaped terminal 50 is 0.3 or higher, the first temperature of the first terminal portion 51 and the second temperature of the second terminal portion 52 are measured using the first radiation thermometer and the second radiation thermometer. 2 temperature can be measured accurately.

The controller 65 is communicably connected to the first heat source 61, the second heat source 62, the first temperature sensor 63, and the second temperature sensor 64. As shown in FIG. The controller 65 controls the first heat source 61 based on the first temperature of the first terminal portion 51 measured using the first temperature sensor 63 . The controller 65 controls the second heat source 62 based on the second temperature of the second terminal portion 52 measured using the second temperature sensor 64 .

When the first terminal portion 51 is joined to the first front electrode 21 , the first terminal portion 51 is heated using the first heat source 61 and the first conductive joining member 55 contacts the first terminal portion 51 . and the third conductive joining member 56 are heated. The first heat source 61 is controlled based on the first temperature of the first terminal portion 51 measured using the first temperature sensor 63 . When joining the second terminal portion 52 to the lead wire 41 , the second terminal portion 52 is heated using the second heat source 62 , and the second conductive joining member 57 in contact with the second terminal portion 52 is heated. Second heat source 62 is controlled based on a second temperature of second terminal portion 52 measured using second temperature sensor 64 .

In a second example, the first conductive joining member 55, the second conductive joining member 57 and the third conductive joining member 56 are heated using the second heating device 60b shown in FIGS. The second heating device 60b includes a first heat source 61b, a second heat source 62b, a first temperature sensor 63b, a second temperature sensor 64b, and a controller 65.

The first heat source 61b is, for example, a first heat block. The second heat source 62b is, for example, a second heat block. The first heat source 61 b heats the first terminal portion 51 of the plate-shaped terminal 50 to heat the first conductive joining member 55 and the third conductive joining member 56 . The second heat source 62 b heats the second terminal portion 52 of the plate-like terminal 50 to heat the second conductive joining member 57 .

The first temperature sensor 63b is a first contact thermometer. The second temperature sensor 64b is a second contact thermometer. The first temperature sensor 63 b contacts the first terminal portion 51 of the plate-shaped terminal 50 to measure the first temperature of the first terminal portion 51 . The first temperature sensor 63b indirectly measures the temperature of the first conductive joint member 55 and the temperature of the third conductive joint member 56 . The second temperature sensor 64b contacts the second terminal portion 52 of the plate-shaped terminal 50 to measure the second temperature of the second terminal portion 52 . The second temperature sensor 64b indirectly measures the temperature of the second conductive joining member 57. As shown in FIG. Since the first contact thermometer contacts the first terminal portion 51 and the second contact thermometer contacts the second terminal portion 52, the emissivity of the plate-like terminal 50 is less than 0.3. Also, the first temperature of the first terminal portion 51 and the second temperature of the second terminal portion 52 can be accurately measured using the first contact thermometer and the second contact thermometer.

The controller 65 is communicably connected to the first heat source 61b, the second heat source 62b, the first temperature sensor 63b, and the second temperature sensor 64b. The controller 65 controls the first heat source 61b based on the first temperature of the first terminal portion 51 measured using the first temperature sensor 63b. The controller 65 controls the second heat source 62b based on the second temperature of the second terminal portion 52 measured using the second temperature sensor 64b.

When the first terminal portion 51 is joined to the first front electrode 21, the first terminal portion 51 is heated using the first heat source 61b, and the first conductive joining member 55 is brought into contact with the first terminal portion 51. and the third conductive joining member 56 are heated. The first heat source 61b is controlled based on the first temperature of the first terminal portion 51 measured using the first temperature sensor 63b. When the second terminal portion 52 is joined to the lead wire 41, the second terminal portion 52 is heated using the second heat source 62b, and the second conductive joining member 57 in contact with the second terminal portion 52 is heated. The second heat source 62b is controlled based on a second temperature of the second terminal portion 52 measured using a second temperature sensor 64b.

Then, the first conductive joint member 55, the second conductive joint member 57 and the third conductive joint member 56 are cooled (S44). While the first terminal portion 51 is joined to the first front surface electrode 21 and the second front surface electrode 26 using the first conductive joining member 55 and the third conductive joining member 56, the second terminal portion 52 is joined to the lead wire 41 using a second conductive joining member 57 . Thus, the plate-like terminal 50 is joined to the first front surface electrode 21 of the first power semiconductor element 20 , the second front surface electrode 26 of the second power semiconductor element 25 , and the lead wire 41 .

Note that when the plate-like terminal 50 is joined to the first power semiconductor element 20, the second power semiconductor element 25, and the lead wire 41 (S4), the plate-like terminal 50g is connected to the front conductor layer 12 and the lead wire 41g. is spliced to A method of joining the plate-like terminal 50g to the front conductor layer 12 and the lead wire 41g is a method of joining the plate-like terminal 50 to the first power semiconductor element 20, the second power semiconductor element 25 and the lead wire 41. It is the same.

The operation of this embodiment will be described.
In the present embodiment, the first linear expansion coefficient difference between the first power semiconductor element 20 and the first terminal portion 51 is the second linear expansion coefficient difference between the lead wire 41 and the second terminal portion 52. Greater than the difference. A third linear expansion coefficient difference between the second power semiconductor element 25 and the first terminal portion 51 is larger than a second linear expansion coefficient difference between the lead wire 41 and the second terminal portion 52 . For example, the first power semiconductor element 20 and the second power semiconductor element 25 are mainly made of Si (linear expansion coefficient of 2.5 ppm/K), and the plate-like terminal 50 and the lead wire 41 are made of Cu (linear expansion coefficient of 2.5 ppm/K). coefficient 16.8 ppm/K), the first linear expansion coefficient difference and the third linear expansion coefficient difference are each 14.3 ppm/K, while the second linear expansion coefficient difference is is zero. Therefore, the thermal stress applied to the first conductive bonding member 55 is greater than the thermal stress applied to the second conductive bonding member 57 . The thermal stress applied to the third conductive bonding member 56 is greater than the thermal stress applied to the second conductive bonding member 57 . During use of the power semiconductor device 1 , a large thermal stress is repeatedly applied to the first conductive joint member 55 and the third conductive joint member 56 .

This thermal stress causes cracks to occur and propagate in the first conductive joint member 55 and the third conductive joint member 56, and the cross-sectional areas of the first conductive joint member 55 and the third conductive joint member 56 are reduced. Let In this specification, the cross-sectional area of the conductive joint member means the area of the conductive joint member in the cross section parallel to the main surface 10 a of the substrate 10 . As the cross-sectional area of the first conductive joining member 55 and the cross-sectional area of the third conductive joining member 56 decrease, the electrical resistance of the first conductive joining member 55 and the electrical resistance of the third conductive joining member 56 increase, and the first conductive Joule heat generated in the joint member 55 and the third conductive joint member 56 increases. The thermal stress applied to the first conductive joint member 55 and the third conductive joint member 56 is further increased. The crack may further develop in the first conductive joint member 55 and the third conductive joint member 56, and the first conductive joint member 55 and the third conductive joint member 56 may be torn completely. When the first conductive joint member 55 and the third conductive joint member 56 are completely torn, a high potential difference is generated between the first front surface electrode 21 of the first power semiconductor element 20 and the lead wire 41, 1 An arc discharge occurs between the front electrode 21 and the lead wire 41 . A high potential difference occurs between the second front electrode 26 of the second power semiconductor element 25 and the lead wire 41, and arc discharge occurs between the second front electrode 26 and the lead wire 41. do. Power semiconductor device 1 breaks down.

However, the first terminal portion 51 is thinner than the second terminal portion 52 . Therefore, the thermal stress applied to the first conductive joining member 55 and the third conductive joining member 56 can be reduced. The occurrence of cracks in the first conductive joining member 55 and the third conductive joining member 56, and the separation of the first terminal portion 51 from the first front surface electrode 21 and the second front surface electrode 26. is prevented.

Also, the heat generated by the first power semiconductor element 20 and the second power semiconductor element 25 is transferred to the second conductive joining member 57 via the plate-like terminal 50 . Therefore, the temperature of the second conductive joining member 57 rises. In addition, the second conductive joint member 57 is in contact with the lead wire 41, and part of the lead wire 41 is embedded in the terminal block 40 made of insulating resin. Therefore, the temperature of the second conductive joining member 57 tends to rise. When the temperature of the second conductive joint member 57 rises, the second conductive joint member 57 deteriorates. For example, when the temperature of the second conductive joint member 57 rises, the crystal grains contained in the second conductive joint member 57 may become large, causing metal fatigue in the second conductive joint member 57 . In this embodiment, the second terminal portion 52 is thicker than the first terminal portion 51 . The second terminal portion 52 has a larger heat capacity than the first terminal portion 51 . Therefore, the temperature rise of the second conductive joining member 57 can be reduced. Deterioration of the second conductive joint member 57 is reduced.

Effects of the power semiconductor device 1 of the present embodiment and the method of manufacturing the same will be described.
A power semiconductor device 1 according to the present embodiment includes a substrate 10 , a first power semiconductor element 20 , lead wirings 41 and plate-like terminals 50 . The first power semiconductor element 20 includes a first rear surface electrode 22 joined to the substrate 10 and a first front surface electrode 21 opposite to the first rear surface electrode 22 . Plate-like terminal 50 includes a first terminal portion 51 and a second terminal portion 52 . The first terminal portion 51 is joined to the first front electrode 21 using a first conductive joining member 55 . The second terminal portion 52 is joined to the lead wire 41 using a second conductive joining member 57 . A first linear expansion coefficient difference between the first power semiconductor element 20 and the first terminal portion 51 is larger than a second linear expansion coefficient difference between the lead wire 41 and the second terminal portion 52 . The first terminal portion 51 is thinner than the second terminal portion 52 .

A first linear expansion coefficient difference between the first power semiconductor element 20 and the first terminal portion 51 is larger than a second linear expansion coefficient difference between the lead wire 41 and the second terminal portion 52 . Therefore, the thermal stress applied to the first conductive bonding member 55 is greater than the thermal stress applied to the second conductive bonding member 57 . However, the first terminal portion 51 is thinner than the second terminal portion 52 . Therefore, the thermal stress applied to the first conductive joining member 55 can be reduced. Cracking of the first conductive joining member 55 and separation of the first terminal portion 51 from the first front electrode 21 are prevented. Furthermore, the second terminal portion 52 is thicker than the first terminal portion 51 . The second terminal portion 52 has a larger heat capacity than the first terminal portion 51 . Therefore, the temperature rise of the second conductive joint member 57 is reduced, and deterioration of the second conductive joint member 57 is reduced. The reliability of the power semiconductor device 1 can be improved.

A ratio of the first thickness t ₁ of the first terminal portion 51 to the second thickness t ₂ of the second terminal portion 52 is 0.10 or more and 0.75 or less. Since this ratio is 0.75 or less, the thermal stress applied to the first conductive joining member 55 can be reduced. Since this ratio is 0.10 or more, heat generation of the first terminal portion 51 due to the electrical resistance of the first terminal portion 51 can be reduced. A rise in temperature of the first conductive joint member 55 can be reduced, and deterioration of the first conductive joint member 55 is reduced. The reliability of the power semiconductor device 1 can be improved.

In power semiconductor device 1 of the present embodiment, first thickness t ₁ of first terminal portion 51 is 0.15 mm or more and 0.60 mm or less. A second thickness t ₂ of the second terminal portion 52 is 0.80 mm or more and 1.50 mm or less.

Since the first thickness t ₁ of the first terminal portion 51 is 0.60 mm or less, the thermal stress applied to the first conductive joining member 55 can be reduced. Cracking of the first conductive joining member 55 and separation of the first terminal portion 51 from the first front electrode 21 are prevented. Since the first thickness t ₁ of the first terminal portion 51 is 0.15 mm or more, heat generation of the first terminal portion 51 due to electrical resistance of the first terminal portion 51 can be reduced. A rise in temperature of the first conductive joint member 55 can be reduced, and deterioration of the first conductive joint member 55 is reduced. Since the second thickness t ₂ of the second terminal portion 52 is 0.80 mm or more, the temperature rise of the second conductive joint member 57 can be reduced, and deterioration of the second conductive joint member 57 can be reduced. . Since the second thickness t ₂ of the second terminal portion 52 is 1.50 mm or less, the mechanical strain applied from the second terminal portion 52 to the second conductive joining member 57 can be reduced. The reliability of the power semiconductor device 1 can be improved.

In the power semiconductor device 1 of the present embodiment, the first conductive joining member 55 is made of a fine metal particle sintered body. In general, sintered metal fine particles have a high melting point of the metal that constitutes the fine particles. Therefore, even if the first power semiconductor element 20 operates at a high temperature, deterioration of the first conductive joining member 55 is reduced. The reliability of the power semiconductor device 1 can be improved.

In power semiconductor device 1 of the present embodiment, first conductive joining member 55 is first solder containing Sn as a main component. The first solder has a higher 0.2% proof stress than Sn. The second conductive joining member 57 is a second solder containing Sn as its main component. The second solder has a higher thermal conductivity than Sn.

The first conductive joint member 55 has a 0.2% yield strength higher than that of the second conductive joint member 57 . Therefore, the first conductive joining member 55 is prevented from cracking and the first terminal portion 51 is prevented from being separated from the first front surface electrode 21 . The second conductive joining member 57 has higher thermal conductivity than the first conductive joining member 55 . Therefore, the temperature rise of the second conductive joining member 57 can be reduced, and deterioration of the second conductive joining member 57 can be reduced. The reliability of the power semiconductor device 1 can be improved.

Furthermore, the first conductive joint member 55 and the second conductive joint member 57 are common in that they are solder containing Sn as a main component. Therefore, the bonding between the first terminal portion 51 and the first front surface electrode 21 using the first conductive bonding member 55 and the connection between the second terminal portion 52 and the lead wiring 41 using the second conductive bonding member 57 Bonds can be formed in the same process. The power semiconductor device 1 has a configuration capable of improving the productivity of the power semiconductor device 1 .

In power semiconductor device 1 of the present embodiment, lead wire 41 further includes a third terminal portion 53 that connects first terminal portion 51 and second terminal portion 52 . The third terminal portion 53 extends along the thickness direction (third direction (z direction)) of the first power semiconductor element 20 in which the first rear surface electrode 22 and the first front surface electrode 21 are separated from each other. extended.

Therefore, the height of the first front surface electrode 21 in the thickness direction (the third direction (z direction)) of the first power semiconductor element 20 is different from the height of the lead wiring 41 , so that the plate-like terminal The mechanical stress applied from 50 to the first conductive joining member 55 and the second conductive joining member 57 is reduced. The occurrence of cracks in the first conductive joint member 55 and the second conductive joint member 57, the separation of the first terminal portion 51 from the first front surface electrode 21, and the second terminal portion 52 being lead wiring. Detachment from 41 is prevented. The reliability of the power semiconductor device 1 can be improved.

The power semiconductor device 1 of the present embodiment further includes a terminal block 40 made of insulating resin. A part of the lead wiring 41 is embedded in the terminal block 40 . The second terminal portion 52 is joined to the portion of the lead wire 41 exposed from the terminal block 40 using a second conductive joining member 57 . The thermal conductivity of the terminal block 40 is lower than the thermal conductivity of the lead wiring 41 and lower than the thermal conductivity of the plate-like terminal 50 .

A portion of the lead wiring 41 is embedded in the terminal block 40 having relatively low thermal conductivity. Therefore, the temperature of the second conductive joining member 57 joined to the lead wire 41 is likely to rise. However, the second terminal portion 52 is thicker than the first terminal portion 51 . Therefore, the temperature rise of the second conductive joining member 57 can be reduced, and deterioration of the second conductive joining member 57 can be reduced. The reliability of the power semiconductor device 1 can be improved.

Power semiconductor device 1 of the present embodiment further includes a second power semiconductor element 25 . The second power semiconductor element 25 includes a second back electrode 27 joined to the substrate 10 and a second front electrode 26 opposite to the second back electrode 27 . The first terminal portion 51 is joined to the second front electrode 26 using a third conductive joining member 56 . A third linear expansion coefficient difference between the second power semiconductor element 25 and the first terminal portion 51 is larger than a second linear expansion coefficient difference between the lead wire 41 and the second terminal portion 52 .

A third linear expansion coefficient difference between the second power semiconductor element 25 and the first terminal portion 51 is larger than a second linear expansion coefficient difference between the lead wire 41 and the second terminal portion 52 . Therefore, the thermal stress applied to the third conductive bonding member 56 is greater than the thermal stress applied to the second conductive bonding member 57 . However, the first terminal portion 51 is thinner than the second terminal portion 52 . Therefore, the thermal stress applied to the third conductive joining member 56 can be reduced. The occurrence of cracks in the third conductive joining member 56 and the separation of the first terminal portion 51 from the second front electrode 26 are prevented. The reliability of the power semiconductor device 1 can be improved.

Furthermore, both the first power semiconductor element 20 and the second power semiconductor element 25 are joined to one plate-like terminal 50 . Therefore, the wiring inductance can be reduced, and the surge voltage applied to the first power semiconductor element 20 and the second power semiconductor element 25 can be reduced. Also, the joining of the plate-like terminal 50 and the first power semiconductor element 20 and the joining of the plate-like terminal 50 and the second power semiconductor element 25 can be performed in one step. The power semiconductor device 1 has a structure capable of improving productivity of the power semiconductor device 1 .

The method for manufacturing the power semiconductor device 1 of the present embodiment includes joining the first back electrode 22 of the first power semiconductor element 20 to the substrate 10 (S1), and connecting the plate-like terminal 50 to the first back electrode 22. is joined to the first front surface electrode 21 and the lead wire 41 of the first power semiconductor element 20 on the opposite side (S4). Plate-like terminal 50 includes a first terminal portion 51 and a second terminal portion 52 . The difference in the first coefficient of linear expansion between the first power semiconductor element 20 and the first terminal portion 51 is greater than the difference in the second coefficient of linear expansion between the lead wire 41 and the second terminal portion 52. . The first terminal portion 51 is thinner than the second terminal portion 52 .

While the first terminal portion 51 is joined to the first front electrode 21 using the first conductive joining member 55, the second terminal portion 52 is joined to the lead wire 41 using the second conductive joining member 57. . When joining the first terminal portion 51 to the first front surface electrode 21, the first conductive joining member 55 is heated using the first heat sources 61 and 61b. The first heat sources 61, 61b are controlled based on the first temperature of the first terminal portion 51 measured using the first temperature sensors 63, 63b. When joining the second terminal portion 52 to the lead wire 41, the second conductive joining member 57 is heated using the second heat sources 62, 62b. The second heat source 62, 62b is controlled based on a second temperature of the second terminal portion 52, which is measured using a second temperature sensor 64, 64b.

A first linear expansion coefficient difference between the first power semiconductor element 20 and the first terminal portion 51 is larger than a second linear expansion coefficient difference between the lead wire 41 and the second terminal portion 52 . Therefore, the thermal stress applied to the first conductive bonding member 55 is greater than the thermal stress applied to the second conductive bonding member 57 . However, the first terminal portion 51 is thinner than the second terminal portion 52 . Therefore, the thermal stress applied to the first conductive joining member 55 can be reduced. Cracking of the first conductive joining member 55 and separation of the first terminal portion 51 from the first front electrode 21 are prevented. Furthermore, the second terminal portion 52 is thicker than the first terminal portion 51 . The second terminal portion 52 has a larger heat capacity than the first terminal portion 51 . Therefore, the temperature rise of the second conductive joining member 57 can be reduced, and deterioration of the second conductive joining member 57 can be reduced. According to the method for manufacturing power semiconductor device 1 of the present embodiment, power semiconductor device 1 with improved reliability can be obtained.

The second terminal portion 52 is thicker than the first terminal portion 51 . The second heat capacity of the second terminal portion 52 is greater than the first heat capacity of the first terminal portion 51 . When the first terminal portion 51 and the second terminal portion 52 are heated, the temperature of the second terminal portion 52 is less likely to rise than the temperature of the first terminal portion 51 . Therefore, the connection between the lead wire 41 and the second terminal portion 52 using the second conductive connection member 57 may become defective. However, in the method for manufacturing the power semiconductor device 1 of the present embodiment, the first conductive joining member 55 in contact with the first terminal portion 51 is heated using the first heat sources 61 and 61b, and the second terminal portion 52 is heated. is heated using second heat sources 62, 62b different from the first heat sources 61, 61b. Furthermore, the first heat sources 61, 61b are controlled based on the first temperature of the first terminal portion 51 measured using the first temperature sensors 63, 63b, while the second heat sources 62, 62b are controlled by: The control is based on the second temperature of the second terminal portion 52 measured using a second temperature sensor 64, 64b separate from the first temperature sensor 63, 63b.

Thus, in the method for manufacturing power semiconductor device 1 of the present embodiment, the second temperature of second terminal portion 52 is measured independently of the first temperature of first terminal portion 51, and the second temperature is measured independently of the first temperature of first terminal portion 51. Terminal portion 52 is heated independently of first terminal portion 51 . Therefore, even if the second terminal portion 52 is thicker than the first terminal portion 51, the first conductive joining member 55 in contact with the first terminal portion 51 and the second conductive joining member 57 in contact with the second terminal portion 52 are separated from each other. can be properly heated. The first front electrode 21 and the first terminal portion 51 are satisfactorily joined together using the first conductive joining member 55 , and the lead wiring 41 and the second terminal portion 52 are joined together by the second conductive joining member 57 . are well bonded to each other using According to the method for manufacturing power semiconductor device 1 of the present embodiment, power semiconductor device 1 with improved reliability can be obtained.

In the method of manufacturing the power semiconductor device 1 of the present embodiment, the first conductive joining member 55 is the first solder containing Sn as its main component. The first solder has a higher 0.2% proof stress than Sn. The second conductive joining member 57 is a second solder containing Sn as its main component. The second solder has a higher thermal conductivity than Sn.

The first conductive joint member 55 has a 0.2% yield strength higher than that of the second conductive joint member 57 . Therefore, the first conductive joining member 55 is prevented from cracking and the first terminal portion 51 is prevented from being separated from the first front surface electrode 21 . Also, the second conductive joint member 57 has a higher thermal conductivity than the first conductive joint member 55 . Therefore, the temperature rise of the second conductive joining member 57 can be reduced, and deterioration of the second conductive joining member 57 can be reduced. According to the method for manufacturing power semiconductor device 1 of the present embodiment, power semiconductor device 1 with improved reliability can be obtained.

Furthermore, the first conductive joint member 55 and the second conductive joint member 57 are common in that they are solder containing Sn as a main component. Therefore, the bonding between the first terminal portion 51 and the first front surface electrode 21 using the first conductive bonding member 55 and the connection between the second terminal portion 52 and the lead wiring 41 using the second conductive bonding member 57 Bonds can be formed in the same process. According to the method for manufacturing power semiconductor device 1 of the present embodiment, power semiconductor device 1 can be obtained with improved productivity.

Embodiment 2.
A power semiconductor device 1b according to the second embodiment will be described with reference to FIG. A power semiconductor device 1b of the present embodiment has a configuration similar to that of the power semiconductor device 1 of the first embodiment, but differs mainly in the following points.

The second terminal portion 52b is a folded portion of the conductive metal plate forming the plate-like terminal 50b. The second terminal portion 52b is formed, for example, by folding a conductive metal plate having a uniform thickness one or more times. The second terminal portion 52b may be formed by folding a conductive metal plate having a uniform thickness two or more times.

The method of manufacturing the power semiconductor device 1b of the present embodiment includes the same steps as the method of manufacturing the power semiconductor device 1 of the first embodiment, but differs in the manufacturing step of the plate-like terminal 50b. In the present embodiment, plate-like terminal 50b is obtained, for example, by the following steps. A conductive metal plate having a uniform thickness is provided. A plate-shaped terminal 50b including a first terminal portion 51, a second terminal portion 52b and a third terminal portion 53 is obtained by pressing a conductive metal plate. The second terminal portion 52b is formed by folding the conductive metal plate one or more times.

In addition to the effects of the power semiconductor device 1 and its manufacturing method of the first embodiment, the power semiconductor device 1b and its manufacturing method of the present embodiment have the following effects.

In the power semiconductor device 1b and the manufacturing method thereof according to the present embodiment, the second terminal portion 52b is a folded portion of the conductive metal plate forming the plate-like terminal 50b. A step of partially thinning the thickness of the conductive metal plate forming the plate-like terminal 50b is not required. Further, in the present embodiment, it is sufficient to prepare a conductive metal plate thinner than that in the first embodiment as the conductive metal plate forming the plate-like terminal 50b. Therefore, the cost of the plate-like terminal 50b is reduced. The cost of the power semiconductor device 1b can be reduced.

Embodiment 3.
A power semiconductor device 1c according to the third embodiment will be described with reference to FIG. A power semiconductor device 1c of the present embodiment has a configuration similar to that of the power semiconductor device 1 of the first embodiment, but differs mainly in the following points.

In the power semiconductor device 1c, a spring portion 54 is provided in the third terminal portion 53. As shown in FIG. The spring portion 54 is formed by bending a conductive metal plate forming the plate-like terminal 50c. The spring portion 54 is obtained, for example, by pressing a conductive metal plate.

The method of manufacturing the power semiconductor device 1c of the present embodiment includes the same steps as the method of manufacturing the power semiconductor device 1 of the first embodiment, but differs mainly in the following two points.

First, the plate-like terminal 50c is obtained by the following steps. A conductive metal plate having a uniform thickness is provided. A plate-like terminal 50c including a first terminal portion 51, a second terminal portion 52 and a third terminal portion 53 is obtained by pressing a conductive metal plate. A spring portion 54 is formed on the third terminal portion 53 . The spring portion 54 is formed by bending a conductive metal plate.

Second, when the plate-like terminal 50c is joined to the first power semiconductor element 20, the second power semiconductor element 25, and the lead wiring 41 (S4), the plate-like terminal 50c is connected to the first front electrode 21, Inclination with respect to the second front surface electrode 26 and the lead wiring 41 is more reliably prevented.

The first terminal portion 51 is thinner than the second terminal portion 52 . Therefore, the center of gravity of the plate-shaped terminal 50 c is located proximal to the second terminal portion 52 and distal to the first terminal portion 51 . That is, the center of gravity of the plate-like terminal 50 c is located proximal to the second conductive joint member 57 and distant from the first conductive joint member 55 and the third conductive joint member 56 . When the plate-shaped terminal 50c is joined to the first power semiconductor element 20, the second power semiconductor element 25 and the lead wiring 41 (S4), the first conductive joining member 55, the second conductive joining member 57 and the third conductive joining member By heating the member 56, the first conductive bonding member 55, the second conductive bonding member 57, and the third conductive bonding member 56 become liquid phase. When the first conductive bonding member 55, the second conductive bonding member 57 and the third conductive bonding member 56 are in the liquid phase, the thickness of the first conductive bonding member 55, the second The thickness of the conductive joint member 57 and the thickness of the third conductive joint member 56 can vary.

Specifically, while the thickness of the second conductive joint proximate to the center of gravity of the plate-like terminal 50c is reduced, the thickness of the first conductive joint farther from the center of gravity of the plate-like terminal 50c and the thickness of the plate-like terminal 50c are reduced. The thickness of the third conductive joint distal to the center of gravity of terminal 50c may increase. The plate-like terminal 50 c may be inclined with respect to the first front electrode 21 , the second front electrode 26 and the lead wire 41 .

Then, the first conductive bonding member 55 and the third conductive bonding member 56 extend in the thickness direction (the third direction (z direction)) of the first power semiconductor element 20, and the cross-sectional area of the first conductive bonding member 55 and the third conductive bonding member 56 extend. The cross-sectional area of the tri-conductive joining member 56 is reduced. The bonding strength of the first conductive bonding member 55 and the bonding strength of the third conductive bonding member 56 after cooling the first conductive bonding member 55 and the third conductive bonding member 56 may become insufficient. In addition, the thickness of the second conductive joint member 57 after cooling the second conductive joint member 57 becomes extremely thin, and a large mechanical strain may be applied to the second conductive joint member 57 from the plate-like terminal 50c. be.

However, the spring portion 54 formed in the third terminal portion 53 allows the first terminal portion 51 and the second terminal portion 52 to independently move in the thickness direction (third direction (z direction)) of the first power semiconductor element 20 . allow you to move to Therefore, even if the center of gravity of the plate-like terminal 50c is biased toward the second terminal portion 52, the first conductive bonding member 55, the second conductive bonding member 57, and the third conductive bonding member 56 are heated and turned into a liquid phase. At this time, the plate-like terminal 50 c is prevented from tilting with respect to the first front electrode 21 , the second front electrode 26 and the lead wire 41 . In the spring portion 54, the cross-sectional area of the first conductive bonding member 55 and the cross-sectional area of the third conductive bonding member 56 are reduced, and the bonding strength of the first conductive bonding member 55 and the bonding strength of the third conductive bonding member 56 are increased. can be reliably prevented from decreasing. The spring portion 54 can reliably prevent a large mechanical strain from being applied to the second conductive joint member 57 .

The power semiconductor device 1c of the present embodiment and its manufacturing method have the same effect as the power semiconductor device 1 of Embodiment 1 and its manufacturing method, but differ mainly in the following points.

In the power semiconductor device and the manufacturing method thereof according to the present embodiment, the third terminal portion 53 is provided with the spring portion 54 formed by bending the conductive metal plate forming the plate-like terminal 50c.

In the spring portion 54, the cross-sectional area of the first conductive bonding member 55 and the cross-sectional area of the third conductive bonding member 56 are reduced, and the bonding strength of the first conductive bonding member 55 and the bonding strength of the third conductive bonding member 56 are increased. can be reliably prevented from decreasing. The spring portion 54 can reliably prevent a large mechanical strain from being applied to the second conductive joint member 57 . The reliability of the power semiconductor device 1c can be improved.

Embodiments 1 to 3 disclosed this time should be considered as examples in all respects and not restrictive. As long as there is no contradiction, at least two of Embodiments 1 to 3 disclosed this time may be combined. The scope of the present disclosure is indicated by the scope of claims rather than the above description, and is intended to include all changes within the meaning and scope of equivalence to the scope of claims.

Reference Signs List 1, 1b, 1c power semiconductor device 10 substrate 10a main surface 11 insulating layer 12 front conductor layer 13 back conductor layer 14 joining member 20 first power semiconductor element 21 first front Surface electrode 22 First back surface electrode 23, 28 Conductive joint member 25 Second power semiconductor element 26 Second front surface electrode 27 Second back surface electrode 30 Heat sink 31 Top plate 32 Radiation fin 33 jacket, 34 inlet, 35 outlet, 36 flow path, 37 refrigerant, 40 terminal block, 41, 41g lead wiring, 50, 50b, 50c, 50g plate-shaped terminal, 51 first terminal portion, 52, 52b second terminal portion, 53 third terminal portion, 54 spring portion, 55 first conductive joint member, 56 third conductive joint member, 57 second conductive joint member, 60 first heating device, 60b second heating device, 61, 61b first heat source, 62, 62b second heat source, 63, 63b first temperature sensor, 64, 64b second temperature sensor, 65 controller.

Claims (15)

a substrate;
a first power semiconductor element including a first back electrode joined to the substrate and a first front electrode opposite to the first back electrode;
lead-out wiring,
A power semiconductor device comprising a plate-like terminal including a first terminal portion and a second terminal portion,
The first terminal portion is joined to the first front electrode using a first conductive joining member,
The second terminal portion is joined to the lead wire using a second conductive joining member,
a first linear expansion coefficient difference between the first power semiconductor element and the first terminal portion is larger than a second linear expansion coefficient difference between the lead wire and the second terminal portion;
The power semiconductor device, wherein the first terminal portion is thinner than the second terminal portion. 2. The power semiconductor device according to claim 1, wherein a ratio of the first thickness of said first terminal portion to the second thickness of said second terminal portion is 0.10 or more and 0.75 or less. the first thickness of the first terminal portion is 0.15 mm or more and 0.60 mm or less;
2. The power semiconductor device according to claim 1, wherein said second terminal portion has a second thickness of 0.80 mm or more and 1.50 mm or less. 4. The power semiconductor device according to any one of claims 1 to 3, wherein said first conductive joining member is made of a sintered metal fine particle. The first conductive joining member is a first solder containing Sn as a main component, and the first solder has a higher 0.2% proof stress than Sn,
4. The second conductive joining member is a second solder containing Sn as a main component, and the second solder has a higher thermal conductivity than Sn. The power semiconductor device according to . The first solder is Sn—Cu solder or Sn—Sb solder,
6. The power semiconductor device according to claim 5, wherein said second solder is Sn-Au solder or Sn-Ag solder. The plate-shaped terminal further includes a third terminal portion connecting the first terminal portion and the second terminal portion,
2. The third terminal portion extends along the thickness direction of the first power semiconductor element in which the first back electrode and the first front electrode are separated from each other. 7. The power semiconductor device according to any one of claims 6 to 7. 8. The power semiconductor device according to claim 7, wherein said third terminal portion is provided with a spring portion formed by bending a conductive metal plate forming said plate-like terminal. 8. The power semiconductor device according to claim 1, wherein said second terminal portion is a folded portion of a conductive metal plate forming said plate-like terminal. Equipped with an insulating resin terminal block,
A part of the lead wiring is embedded in the terminal block,
the second terminal portion is joined to a portion of the lead wiring exposed from the terminal block using the second conductive joining member;
The power according to any one of claims 1 to 9, wherein the thermal conductivity of the terminal block is smaller than the thermal conductivity of the lead wiring and smaller than the thermal conductivity of the plate-like terminal. semiconductor device. further comprising a second power semiconductor element including a second back electrode bonded to the substrate and a second front electrode opposite to the second back electrode;
The first terminal portion is joined to the second front electrode using a third conductive joining member,
a third linear expansion coefficient difference between the second power semiconductor element and the first terminal portion is larger than the second linear expansion coefficient difference between the lead wire and the second terminal portion; The power semiconductor device according to any one of claims 1 to 10. bonding the first back electrode of the first power semiconductor element to the substrate;
joining a plate-like terminal to the first front surface electrode and lead wiring of the first power semiconductor element on the side opposite to the first back electrode;
The plate-shaped terminal includes a first terminal portion and a second terminal portion,
A first difference in coefficient of linear expansion between the first power semiconductor element and the first terminal portion is larger than a second difference in coefficient of linear expansion between the lead wire and the second terminal portion. ,
The first terminal portion is thinner than the second terminal portion,
While the first terminal portion is joined to the first front surface electrode using a first conductive joining member, the second terminal portion is joined to the lead wire using a second conductive joining member,
When joining the first terminal portion to the first front electrode, the first conductive joining member is heated using a first heat source, and the first heat source is measured using a first temperature sensor. controlled based on the first temperature of the first terminal portion,
When the second terminal portion is joined to the lead wire, the second conductive joining member is heated using a second heat source, and the second heat source is the second terminal measured using a second temperature sensor. A method of manufacturing a power semiconductor device controlled based on a second temperature of the part. The first conductive joining member is a first solder containing Sn as a main component, and the first solder has a higher 0.2% proof stress than Sn,
13. The method of manufacturing a power semiconductor device according to claim 12, wherein said second conductive joining member is a second solder containing Sn as a main component, said second solder having a higher thermal conductivity than Sn. . The first solder is Sn—Cu solder or Sn—Sb solder,
14. The method of manufacturing a power semiconductor device according to claim 13, wherein said second solder is Sn-Au solder or Sn-Ag solder. The plate-shaped terminal further includes a third terminal portion connecting the first terminal portion and the second terminal portion,
the third terminal portion extends along the thickness direction of the first power semiconductor element in which the first back surface electrode and the first front surface electrode are separated from each other;
The power semiconductor according to any one of claims 12 to 14, wherein the third terminal portion is provided with a spring portion formed by bending a conductive metal plate that constitutes the plate-like terminal. Method of manufacturing the device.

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