JP2008226920A - Connection structure of power module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive connection structure of a power module capable of coping with an increase in power. <P>SOLUTION: The power module 10 has: a semiconductor chip 11 having an upper surface electrode 11 as a conductive member; a DBA substrate 23 having a conductive member (upper metal layer 23a); a heat sink 21; and the like. The power module 10 is stored at the opening of a resin case 53 mounted to a top board 50a in a vessel. In the resin case 53, a wiring member (electrode terminal layer 56) connected to external equipment is provided. Then a metal wiring board 31 is provided, wherein a base end section 31a is connected to the wiring member, and a tip section 31b is pressed against the conductive member of the power module 10 due to elastic deformation and is brought into contact to conduct electricity. The metal wiring board 31 allows a large current to flow with a large sectional area, and the manufacturing cost is small. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a connection structure of a power module on which a semiconductor power device is mounted.

  In recent years, modules using IGBTs or FETs have been used as power modules (semiconductor devices) equipped with switching elements for driving motors, such as electric vehicles, hybrid vehicles, and fuel cells. In particular, in-vehicle semiconductor devices require high power and small size.

In order to meet such demands, various proposals have been made for wiring members that connect the power module and external terminals. In Patent Document 1, a bundled wire, a stranded wire, and a braided wire are used as a connection conductor structure for electrically connecting a semiconductor chip incorporated in a package and an external device, instead of bonding a large number of aluminum wires. Therefore, it is possible to prevent the occurrence of damage such as peeling of the solder joints and chip cracking by absorbing the tensile stress caused by the thermal shrinkage that occurs in the solder connection process by the connection conductor while enabling the transmission of high power. Techniques to do this are disclosed.
JP 2004-319740 A

  As the power module becomes more and more powerful, it becomes difficult to form a single-wire bonding wire in a narrow region. However, the technique of Patent Document 1 can transmit a large amount of power compared to a single-wire bonding wire. it can. However, it is possible to prevent the bundled wires and the like from falling apart, and to make a structure for reliably passing a current through each wire complicated, resulting in an increase in manufacturing cost. For example, as shown in enlarged detail in FIG. 2 of the same publication, a terminal is provided at the connection portion between the connection conductor and the semiconductor chip in order to surely flow the current through each line. For example, it is necessary to make the terminal structure strong in order to allow current to flow through each line with certainty. However, if the terminal structure is strengthened, it is difficult to reduce the size of the entire structure, and there is a risk of peeling of the solder joints and chip cracking due to thermal cycling and stress during soldering, resulting in reduced reliability. There is a risk.

  An object of the present invention is to provide a power module connection structure that can transmit a large amount of power and is inexpensive to manufacture.

  The power module connection structure of the present invention includes a metal wiring board in which a base is connected to a wiring member connected to an external device, and a distal end is pressed against the conductive member by elastic deformation so as to be conductive.

  Thereby, the metal wiring board-conductive member is reliably conducted through the contact portion due to elastic deformation of the front end portion of the metal wiring board. And since it is not necessary to connect many wires, manufacturing cost is also cheap. In addition, it becomes easy to flow a large current through the metal wiring board, and it is possible to cope with an increase in power of the power module.

  By further including a solder member that joins the leading end portion of the metal wiring board and the conductive member, the reliability of the joining is improved.

  By further including an adhesive layer that fixes the tip of the metal wiring board and the conductive member to each other, the contact state between the tip of the elastic member and the conductive member can be more reliably maintained.

  Since the contact surface of the metal wiring board with the conductive member is ground, the metal wiring board and the conductive member come into strong contact.

  Since the convex portion is formed on the contact surface of the metal wiring board with the conductive member, a new surface where the natural oxide film is destroyed is exposed on the contact surface between the metal wiring board and the conductive member. Contact resistance with the member is reduced.

  As a specific structure of the metal wiring board, in the natural state, it intersects the base or the intermediate part connected to the base, and in the attached state, it can be forcibly deformed so as to approach the position orthogonal to the base or the intermediate part. Since the tip end portion can be elastically deformed simply by fixing the base end portion with a bolt or the like, the connection structure is simplified.

  According to the power module connection structure of the present invention, it is possible to transmit a large amount of power and to provide an inexpensive power module connection structure.

(Embodiment 1)
1 is a cross-sectional view showing a structure of a power unit according to Embodiment 1. FIG. As shown in the figure, the power unit of this embodiment is configured by joining a power module 10 on a radiator 50. The radiator 50 includes a top plate 50a and a container 50b joined to the top plate 50a. The top plate 50a is provided with a number of rectangular through holes for incorporating the power module 10 therein. The top plate 50a and the container 50b constituting the radiator 50 are made of aluminum or an aluminum alloy, and can be manufactured by die casting, extrusion, forging, casting, machining, or the like. In a flow path 51 between the top plate 50a and the container 50b of the radiator 50, cooling water as a heat exchange medium flows in a direction orthogonal to the paper surface of FIG.

  In the assembly process of the present embodiment, after the power module 10 (power module) is mounted on the top plate 50a of the radiator 50, the top plate 50a is joined to the container 50b, but the top plate 50a, the container 50b, After joining, the power module 10 may be mounted. This joining may be performed by mechanical caulking or the like. Further, in the present embodiment, the radiator 50 is formed by individually forming the top plate 50a and the container 50b and then joining them together, but the top plate and the container may be integrally formed. In that case, the radiator can be formed, for example, by die casting using an integral type.

   The power module 10 includes, as main members, a semiconductor chip 11 on which a semiconductor element such as an IGBT is formed, and a DBA substrate 23 for electrically connecting the semiconductor element in the semiconductor chip 11 and an external member. . The DBA substrate 23 has a structure in which an upper metal layer 23a made of Al or an Al alloy, an ALN layer 23b that is an insulator, and a lower metal layer 23c made of Al or an Al alloy are laminated. The power module 10 includes an upper solder layer 14 that joins the upper metal layer 23a and the semiconductor chip 11, a heat sink 21 for releasing heat generated in the semiconductor chip 11 to the outside, and a lower metal layer 23c. A lower solder layer 26 for joining the heat sink 21 is provided. The upper metal layer 23a of the DBA substrate 23 is joined to and electrically connected to the back electrode (not shown) of the semiconductor chip 11 by the upper solder layer 14. That is, the upper metal layer 23a is a wiring of the power module 10 and is one of the conductive members.

  The heat sink member 21 includes a flat plate portion 21a and a fin portion 21b that protrudes from the flat plate portion 21a toward a region (flow path 51) through which cooling water that is a heat exchange medium flows and is exposed to the cooling water. Further, a groove surrounding the opening is formed in the top plate 50a, and an O-ring 25 is mounted in the groove. The flat plate portion 21 a of the heat sink member 21 presses the O-ring 25, and the flow path 51 is blocked from the external space by the O-ring 25. Thereby, the flow path 51 is sealed so that the cooling water does not leak to the outside.

  A resin case 53 is attached to the top plate 50 a by bolts 54, and the power module 10 is disposed in an opening of the resin case 53. The resin case 53 is formed with an electrode terminal layer 56 that is a wiring member connected to an external device. A leaf spring-like metal wiring board 31 is provided to connect the electrode terminal layer 56 and the conductive member of the power module 10. In the present embodiment, the conductive member of the power module 10 is the upper surface electrode 12 (see FIG. 2B) of the semiconductor chip 11 or the upper metal layer 23a (metal wiring) of the DBA substrate 23. However, the conductive member is not limited to these.

  2A and 2B are a cross-sectional view of a natural state before attachment of the metal wiring board and a connection structure after attachment, in order, in the first embodiment. As shown in FIG. 2 (a), the metal wiring board 31 is a flat plate bent at two locations, and is connected to a tip 31a that contacts the conductive member of the power module 10 and a wiring member connected to an external device. It has a base part 31b to be connected and an intermediate part 31c located between the tip part 31a and the base part 31b. And in the natural state before attachment, the front-end | tip part 31a is extended in the direction which cross | intersects the intermediate part 31c at the angle (alpha), and this angle (alpha) is set only the angle (beta) rather than the right angle. On the other hand, the base end portion 31b is bent substantially at a right angle from the intermediate portion 31c and extends substantially horizontally.

2B, the base 31b of the metal wiring board 31 is placed on the electrode terminal layer 56, and the tip 31a is placed on the conductive member of the power module 10 (in this figure, the semiconductor chip 11). The screws 32 are attached to the resin case 53 at a plurality of locations in contact with the upper surface electrode 12). Thereby, the front-end | tip part 31a of the metal wiring board 31 is bent to a substantially horizontal position, and is pressed on the upper surface electrode 12 (conductive member) of the semiconductor chip 11. In other words, the tip 31a of the metal wiring board 31 is bent upward from the natural state by an angle β and approaches a position orthogonal to the intermediate portion 31c, thereby causing a force to restore the natural state (downward biasing force). Due to this restoring force, the tip portion 31a and the upper surface electrode 12 are pressed against each other and come into contact with each other in a stable and conductive manner. FIG. 2B shows a connection state between the electrode terminal layer 56 and the upper surface electrode 12 of the semiconductor chip 11, but the electrode terminal layer 56 and the upper metal layer 23 a (conductive member of the power module) of the DBA substrate 23. The connecting portion (see FIG. 1) also has the same structure.
In order to cause elastic deformation only at the tip portion 31a as much as possible, the base portion 31b of the metal wiring board 31 can be made thicker than the tip portion, or a reinforcing plate can be provided along the base portion 31b.

According to the connection structure of the power module according to the present embodiment, the metal wiring board 31 whose tip 31a is a leaf spring is used to connect the conductive member of the power module 10 and the wiring member connected to the external device. As in the case of using a large number of bonding wires, no complicated work is required, and the manufacturing cost can be reduced. Further, since a large current can be passed through the metal wiring board 31, it is possible to easily cope with an increase in power of the power module 10. For example, the diameter of the bonding wire is about 0.4 mm (cross-sectional area is about 0.13 mm 2), but the thickness of the metal wiring board 31 is 0.5 mm to 1 mm and the width is 5 to 20 mm. Therefore, the current equivalent to several tens to hundreds of bonding wires can be flowed by one metal wiring board 31.
Therefore, the power module connection structure of the present embodiment can provide an inexpensive power module while accommodating the increase in power of the power module.

  The constituent material of the metal wiring board 31 of the present invention is not limited to Al or Al alloy of the present embodiment. For example, Cu or Cu alloy having a smaller electrical resistance may be used, but when compared with the same cross-sectional area, the biasing force generated by deformation is smaller in Al or Al alloy, so that the conductive member is pressed against the tip 31a. Is preferable in that it can be avoided reliably.

  The shape of the metal wiring board 31 of the present invention is not limited to the structure shown in FIG. For example, even if it is substantially flat in the natural state, the tip 31a of the metal wiring board 31 is pressed against the conductive member by a force that is deformed from the natural state in the attached state and attempts to restore the natural state. It only has to be. However, it is preferable that the conductive member of the distal end portion 31a is substantially planarly contacted in the attached state.

(Modification 1)
FIGS. 3A and 3B are a cross-sectional view in a natural state before attachment of a metal wiring board and a connection structure after attachment in Modification 1 of Embodiment 1, respectively. In this modification, the conductive member of the power module 10 is the upper metal layer 23 a of the DBA substrate 23. In FIG. 3B, the members indicated by the same reference numerals as those shown in FIG. 1 have the structure as described with reference to FIG.

  As shown in FIG. 3A, a convex portion 31d is provided on the lower surface of the tip portion 31a of the metal wiring board 31 according to this modification. Then, as shown in FIG. 3B, when the metal wiring board 31 made of Al or Al alloy is attached, the convex portion 31d of the tip 31a bites into the upper metal layer 23a made of Al or Al alloy, At the same time as the metal layer 23a is deformed, the convex portion 31d is crushed, so that the natural oxide film on both surfaces is destroyed and the new surface is exposed, and the contact resistance between them is reduced.

  In addition, it is also preferable to provide a finishing surface instead of the convex portion 31d shown in FIG. In this case, the ground-processed surface of the tip portion 31a of the metal wiring board 31 and the surface of the contact portion of the conductive member of the power module 10 are in strong contact.

(Modifications 2 and 3)
FIGS. 4A and 4B are diagrams showing the connection structure after the metal wiring board is attached in Modifications 2 and 3 of Embodiment 1 in order. In these modifications, the conductive member of the power module 10 is the upper surface electrode 12 of the semiconductor chip 11.

  As shown in FIG. 4A, in Modification 2, the tip 31a of the metal wiring board 31 and the conductive member (upper surface electrode 12) are joined to each other by a solder layer. The solder layer 34 improves the reliability of bonding (electrical connection) between the tip 31a and the conductive member (upper surface electrode 12).

  In the structure shown in FIG. 4A, the solder layer 34 is in contact only with the upper surface of the upper electrode 12 and the side surface of the tip portion 31a of the metal wiring board 31, but the solder layer 34 is in contact with the upper electrode 12 and the tip. A structure entering between the portions 31a can also be adopted. The bonding strength is further improved when the solder layer 34 is inserted between the upper surface electrode 12 and the tip 31a.

  As shown in FIG. 4B, in Modification 3, the tip 31a of the metal wiring board 31 and the conductive member (upper surface electrode 12) are fixed to each other by an adhesive layer 35 such as an epoxy resin. . By this adhesive layer 35, the contact state between the tip 31a and the conductive member (upper surface electrode 12) can be more reliably maintained.

(Embodiment 2)
FIGS. 5A and 5B are, in order, a cross-sectional view in a natural state before mounting a metal wiring board in Embodiment 2, and a diagram showing a wiring structure of a power module. In the present embodiment, the conductive member of the power module 10 is the upper surface electrode 12 of the semiconductor chip 11. In the present embodiment, parts other than the connection structure are provided with the same members as those in the first embodiment (see FIG. 1).

  As shown in FIG. 5A, in the present modification, in the natural state of the metal wiring board 31, the tip portion 31a and the intermediate portion 31c intersect at an angle α that is smaller than the right angle by β. And as shown in FIG.5 (b), when the metal wiring board 31 is attached, the front-end | tip part 31a will be bent upwards so that it may approach the position orthogonal to the intermediate part 31c (it is forcedly elastically deformed), The lower surface of the distal end portion 31a and the upper surface of the upper surface electrode 12 are in planar contact.

  In the present embodiment, contrary to the first embodiment, the wiring member (terminal electrode layer 56) connected to the external device is positioned below the conductive member (the upper surface electrode 12 of the semiconductor chip 11) of the power module. The same effect as in the first embodiment can be exhibited. Also in the present embodiment, the structures of the first to fourth modifications of the first embodiment can be adopted.

(Other embodiments)
FIG. 6 is a cross-sectional view showing a structural example in which the metal wiring board 31 is configured only by the tip portion 31a and the base portion 31b, unlike the first and second embodiments. As shown in the figure, the base end portion 31b is attached to a wiring member connected to an external device by a screw 32. When the surface 31L is connected to the conductive member of the power module 10, it is positioned on the L side in a natural state. On the other hand, when the surface 31R is connected to the conductive member of the power module 10, the tip 31a is positioned on the R side in a natural state. And when attached, the front-end | tip part 31a is forcibly elastically deformed so that it may approach the position orthogonal to the base 31b, and it contacts an electrically-conductive member.
This example shows a structure in which the conductive member of the power module 10 extends in the vertical direction. Conversely, when the conductive member of the power module 10 extends in the lateral direction, the tip end portion 31a extends in the lateral direction, and the structure in which FIG. 6 is rotated 90 ° clockwise or counterclockwise is adopted. become.
Even if the metal wiring board 31 has the structure shown in FIG. 6, the distal end portion 31 a exerts an action of pressing and contacting the conductive member by elastic deformation, so that the same effect as in the first embodiment can be exhibited. Moreover, the structure of the modifications 1-4 of Embodiment 1 can also be taken.

  In each of the above embodiments, the DBA substrate 23 is disposed in the power module 10, but instead of the DBA substrate 23, a single layer wiring made of Cu or Cu alloy, Al or Al alloy, or the like may be provided. .

  The heat exchange medium for exchanging heat with the heat sink member 24 is preferably a liquid such as fluorinate or water in consideration of cooling ability and cost. However, it may be a gas such as helium, argon, nitrogen or air.

  In the above embodiment, a structure in which a large number of power modules 10 are attached to the top plate 50a is adopted. However, a large number of semiconductor chips may be mounted on a single heat sink member 24 that also serves as a top plate.

The structure of the embodiment of the present invention disclosed above is merely an example, and the scope of the present invention is not limited to the scope of these descriptions. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

  The connection structure of the power module of the present invention can be used for various devices equipped with MOSFET, IGBT, diode, JFET and the like.

2 is a cross-sectional view showing a structure of a power unit according to Embodiment 1. FIG. (A), (b) is a figure which shows the cross-sectional view of the natural state before attachment of the metal wiring board in Embodiment 1, and the connection structure after attachment in order. (A), (b) is sectional drawing of the natural state before attachment of the metal wiring board in the modification 1 of Embodiment 1, and the figure which shows the connection structure after attachment in order. (A), (b) is a figure which shows the connection structure after the attachment of the metal wiring board in the modification 2, 3 of Embodiment 1 in order. (A), (b) is a figure which shows the cross-sectional view of the natural state before attachment of the metal wiring board in Embodiment 2, and the wiring structure of a power module in order. It is sectional drawing which shows the structural example by which the metal wiring board was comprised only by the front-end | tip part and the base.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Power module 11 Semiconductor chip 12 Upper surface electrode 14 Upper layer solder layer 21 Heat sink member 21a Flat plate part 21b Fin part 23 DBA substrate 23a Upper metal layer 23b AlN layer 23c Lower metal layer 25 O-ring 26 Lower layer solder layer 31 Metal wiring board 31a Tip part 31b Base end portion 31c Intermediate portion 31d Convex portion 31R, 31L Surface 32 Screw 50 Radiator 50a Top plate 50b Container 51 Flow path 53 Resin case 56 Electrode terminal layer

Claims (6)

A power module connection structure for electrically connecting a conductive member connected to a part of the power module and a wiring member connected to an external device,
A connection structure for a power module, comprising a metal wiring board having a base connected to the wiring member and a distal end pressed against the conductive member by elastic deformation so as to be conductive. In the connection structure of the power module according to claim 1,
A connection structure for a power module, further comprising a solder member that joins the tip of the metal wiring board and the conductive member to each other. In the connection structure of the power module according to claim 1,
A connection structure for a power module, further comprising an adhesive layer that fixes the tip of the metal wiring board and the conductive member to each other. In the connection structure of the power module in any one of Claims 1-3,
The connection structure of the power module, wherein the contact surface of the metal wiring board with the conductive member is ground. In the connection structure of the power module in any one of Claims 1-3,
A connection structure of a power module, wherein a convex portion is provided on a contact surface of the metal wiring board with the conductive member. In the connection structure of the power module in any one of Claims 1-5,
In the natural state, the tip portion intersects the base portion or an intermediate portion connected to the base portion, and in the attached state, the tip portion is forcibly deformed so as to approach a position orthogonal to the base portion or the intermediate portion. Connection structure.

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