JP5532601B2 - Power module substrate and manufacturing method thereof - Google Patents

Description

  The present invention relates to a method for manufacturing a power module substrate used in a semiconductor device that controls a large current and a high voltage.

In general, a power module for supplying power among semiconductor elements has a relatively high calorific value. As this power module substrate, for example, as shown in Patent Document 1, AlN, Al ₂ O ₃ , Si ₃ N _4. A metal plate such as an aluminum plate joined to a ceramic substrate made of SiC or the like via a brazing material such as an Al-Si type is used. Such a circuit board can be manufactured, for example, as shown in Patent Document 2, by bonding a metal plate previously punched into a circuit pattern to a ceramic substrate using a brazing material. This circuit board is a power module in which electronic components (power elements such as semiconductor chips) are mounted on the surface of a circuit pattern via a solder material.

The metal plate and the ceramic substrate can be joined by pressurizing in the stacking direction in a high temperature state with a brazing material interposed, as shown in Patent Document 3, for example.
JP 2004-356502 A JP 2008-108957 A JP-A-10-158073

  When the ceramic substrate and the metal plate are bonded as described above, if the amount of the brazing material is insufficient, a portion where the brazing material is insufficient between the metal plate and the ceramic substrate is generated, or the bonded portion is caused by warping of the ceramic substrate. There is a possibility that problems such as peeling and circuit layer peeling will occur. Further, the brazing material does not adhere to the entire surface of the metal plate, and there is a possibility that the metal plate cannot be reliably bonded to the ceramic substrate. Furthermore, if bonding is not sufficient, peeling may occur under temperature cycle conditions that repeat temperature changes.

  On the other hand, if a sufficient amount of brazing material is used, the excess of the molten brazing material adheres to the surface of the metal plate via the ceramic substrate and the side of the metal plate, alters this surface, and adheres to the circuit pattern. There is a problem that the adhesiveness of the bonding wire of the electronic component is impaired.

  Therefore, the amount of brazing material is set appropriately and the laminated ceramic substrate and metal plate are pressed uniformly so that the ceramic substrate and the metal plate can be reliably bonded without adhering the brazing material to the circuit pattern surface. However, it is difficult to uniformly pressurize a metal plate formed in a complicated circuit pattern. Furthermore, it is difficult to precisely form the flatness, parallelism, thickness of each ceramic substrate and metal plate, etc., for pressing the ceramic substrate and the metal plate. There was a problem that the adhesion of the brazing material could not be completely eliminated.

  The present invention has been made in view of such circumstances, and provides a power module substrate capable of reliably joining a metal plate and a ceramic substrate and preventing adhesion of a brazing material to a circuit surface and a method for manufacturing the same. For the purpose.

The power module substrate of the present invention has a ceramic substrate and a metal layer made of Al brazed to the ceramic substrate with a brazing material made of an Al—Si based alloy to form a circuit pattern. A metal plate and a buffer porous layer made of the same material of the metal plate and joined between the metal plates, and the surplus brazing material is provided near the surface and end face of the buffer porous layer. Minutes are absorbed and retained.

The present invention is also a method for manufacturing the power module substrate , comprising a first metal plate and a second metal plate, and a buffering porous layer made of the same material of these metal plates and sandwiched between the metal plates. And a first brazing material layer disposed between at least one of the buffer porous layer and the first metal plate or between the buffer porous layer and the second metal plate, and A metal lamination step of forming a metal laminate having a second brazing filler metal layer disposed on the outer surface of the second metal plate; and the ceramic substrate and the metal so as to bring the second brazing filler metal layer into contact with the ceramic substrate. Layered laminates and heating them while pressing them in the thickness direction, thereby joining the metal plates of the metal laminate and the buffering porous layer, and the second metal plate, Bonding the ceramic substrate to the front And a bonding step of bonding the metal layer to the ceramic substrate.

  According to this invention, the surplus of the brazing material that joins the metal layer and the ceramic substrate is absorbed by the buffer porous layer by capillary action when spreading from the ceramic substrate side to the circuit pattern side due to surface tension. Therefore, it does not reach the circuit pattern surface of the metal plate. In addition, since the buffer porous layer is disposed between the metal plates, even if the thickness of the metal layer and the ceramic substrate and the flatness of the pressure plate vary, the pressure between the metal layer and the ceramic substrate can be made uniform. can do. Therefore, it is possible to obtain a power module substrate in which the metal plate and the ceramic substrate are securely bonded to each other, and adhesion of the brazing material to the circuit surface is prevented.

In this method of manufacturing a power module substrate, in the metal lamination step, between the buffer porous layer and the first metal plate or between the buffer porous layer and the second metal plate. Further, it is preferable to dispose a third brazing material layer.
In this case, even if there is little surplus of the brazing material which joins a metal layer and a ceramic substrate, each layer can be brazed reliably.

  According to the power module substrate and the method of manufacturing the same of the present invention, it is possible to obtain a power module substrate in which the metal plate and the ceramic substrate are securely bonded and the brazing material is prevented from adhering to the circuit surface.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a power module 10 in which a power module substrate according to the present invention is used. The power module 10 includes a power module substrate 20 having a circuit pattern P formed on the surface, an electronic component 11 such as a semiconductor chip mounted on the surface of the power module substrate 20, and a back surface of the power module substrate 20. And a cooler 13 to be joined.

  The electronic component 11 is bonded onto the circuit pattern P of the power module substrate 20 by a solder material 12 such as Sn—Ag—Cu, Zn—Al, or Pb—Sn, and is made of aluminum with respect to the circuit terminal portion. They are connected by bonding wires (not shown). A plating film 14 such as nickel plating is formed on the surface of the circuit pattern P.

  The cooler 13 is formed by extrusion molding of an aluminum alloy, and a large number of flow paths 13a are formed along the length direction for circulating cooling water. The cooler 13 and the power module substrate 20 are joined by brazing, soldering, bolts or the like.

  In this way, the power module 10 is manufactured by joining the cooler 13, soldering the electronic component 11, wire bonding, and the like to the power module substrate 20.

Next, a method for manufacturing the power module substrate 20 will be described. The power module substrate 20 is formed by laminating a metal laminate 30 to be the metal layer 24 and the ceramic substrate 22 (metal lamination step), and heating them at a high temperature to join the metal layer 24 and the ceramic substrate 22 ( Manufacturing process).
Here, in this embodiment, the ceramic substrate 22 is formed using AlN (aluminum nitride) as a base material. The ceramic substrate 22 may be made of, for example, a nitride ceramic such as AlN or Si ₃ N ₄ (silicon nitride), or an oxide ceramic such as Al ₂ O ₃ (alumina).

First, the metal laminated body 30 arrange | positioned on the ceramic substrate 22 is formed (metal lamination process).
As shown in FIG. 2, the metal laminate 30 includes a first metal plate 31 and a second metal plate 32, a buffering porous layer 33 disposed between the metal plates 31 and 32, and the buffering porous material. A first brazing material layer 34 disposed between the layer 33 and the first metal plate 31; a second brazing material layer 35 disposed on the outer surface of the second metal plate 32; a buffering porous layer 33; And a third brazing filler metal layer 36 disposed between the two metal plates 32.
The circuit layer metal laminate 30 bonded to the surface of the ceramic substrate 22 is formed in the shape of the circuit pattern P of the power module 10, and the metal for the heat dissipation layer bonded to the back surface of the ceramic substrate 22. The laminated body 30 is also formed in a necessary size and shape, but detailed illustration of the shape is omitted here.

The first metal plate 31, the second metal plate 32, and the buffer porous layer 33 are formed of Al in this embodiment, but may be formed of, for example, an aluminum alloy. The buffering porous layer 33 is a sintered sheet material manufactured by sintering Al powder.
The brazing material used for each brazing material layer 34, 35, 36 is an Al—Si based alloy in this embodiment. For example, Al—Ge based, Al—Cu based, Al—Mg based, Al—Mn based, etc. An alloy of

Next, as shown in FIG. 2, the metal laminate 30 and the ceramic substrate 22 are laminated so that the second brazing material layer 35 is brought into contact with the ceramic substrate 22, and these are heated while being pressed in the thickness direction. Then, the metal layer 24 is bonded to the ceramic substrate 22 (bonding step).
In this joining step, a plurality of laminates in which the metal laminates 30 are arranged on both surfaces of the ceramic substrate 22 are arranged in the plane direction and arranged between the pair of pressure plates 40. The pressure plate 40 is made of carbon and is urged toward each other by means such as a spring.

  When the metal laminate 30 is pressed in the thickness direction between the pressure plates 40, the buffer porous layer 33 can be deformed. Variations in the thickness of the metal laminate 30 and the ceramic substrate 22 and the flatness of the pressure plate 40 are absorbed by the deformation of the buffer porous layer 33, so that the pressure applied to the metal laminate 30 is uniform. Become.

  The first brazing material layer 34 and the third brazing material layer 36 between the first metal plate 31 and the second metal plate 32 are melted by being pressurized and heated between the pressure plates 40, and the buffer porous layer 33. The first metal plate 31, the buffering porous layer 33 and the second metal plate 32 are brazed. A sufficient amount of the first brazing material layer 34 and the third brazing material layer 36 is used for this brazing. For this reason, the excess brazing filler metal of the first brazing filler metal layer 34 and the third brazing filler metal layer 36 is absorbed into the buffering porous layer 33 by capillarity, and on both surfaces of the buffering porous layer 33 as shown in FIG. A solid Al layer 33a is formed.

  Further, the second brazing material layer 35 in contact with the ceramic substrate 22 is melted to braze the ceramic substrate 22 and the second metal plate 32. Since the second brazing material layer 35 is used in an amount sufficient for this brazing, the surplus brazing material 35 a is pushed out from between the ceramic substrate 22 and the second metal plate 32. At this time, since the second metal plate 32 has higher wettability to the molten brazing material than the ceramic substrate 22, the surplus brazing material 35a has a sufficient amount when the second metal plate 32 is sufficiently large. It flows along the end face of the first electrode, reaches the buffer porous layer 33, and is absorbed therein by capillary action.

  At this time, a uniform pressure is applied to the metal laminate 30 due to the deformation of the buffer porous layer 33. Therefore, each surplus brazing material in the molten state flows out uniformly without concentrating on a specific portion between the metal plates 31, 32, the buffer porous layer 33 and the ceramic substrate 22. Therefore, surplus brazing material that cannot be absorbed by the buffer porous layer 33 does not ooze out to the surface of the first metal plate 31.

  As described above, the power module substrate 20 shown in FIG. 4 is manufactured by performing the metal lamination step and the joining step. In the power module substrate 20, the metal layer 24 includes two metal plates 31 and 32, and a buffering porous layer 33 bonded between the metal plates 31 and 32. The surplus portion of the brazing material used for joining the layers in the metal layer 30 is absorbed and held near the surface and end face of the buffer porous layer 33, thereby forming a solid layer 33a. When the amount of surplus brazing material is small, a porous portion 33 b that does not absorb and hold the brazing material is formed at the center of the buffering porous layer 33.

  In order to prevent the surplus brazing material from oozing out on the surface of the circuit pattern P, it is necessary that the absorption holding capacity of the buffer porous layer 33 is sufficient with respect to the amount of the surplus brazing material. Moreover, if the porous part 33b exists, the impact resistance of the power module substrate 20 can be improved. Therefore, the amount of the brazing material in each brazing material layer 34, 35, 36 is surely absorbed by the buffering porous layer 33 according to the absorption holding capacity of the buffering porous layer 33, and is used for the power module. It is appropriately set according to the performance required for the substrate 20.

  As described above, according to the present invention, the metal layer 24 includes the buffering porous layer 33 that can be deformed in accordance with the absorption and pressure of the excess brazing material. The pressure applied to the surface becomes uniform in the surface direction, and it is possible to prevent a large amount of surplus brazing material from being generated locally, and to retain the surplus brazing material in the buffer porous layer 33 (that is, the metal layer 24). . Therefore, the leaked surplus brazing material can be efficiently absorbed by the entire buffer porous layer 33, and adhesion of the brazing material to the circuit surface of the circuit pattern P can be prevented. Further, since the pressure in the thickness direction applied to the metal layer 24 can be made uniform in the surface direction, a plurality of power module substrates 20 can be arranged in the surface direction and brazed. Therefore, the power module substrate 20 can be efficiently mass-produced without increasing the size of the joining device including the pressure plate 40 in the thickness direction.

  In addition, this invention is not limited to the thing of the structure of the said embodiment, In a detailed structure, it is possible to add a various change in the range which does not deviate from the meaning of this invention. For example, in the above embodiment, the buffer porous layer is made of a sintered sheet material. However, for example, a powder sintered material, a mesh material knitted with a wire material, a non-woven fabric, etc. can be deformed with respect to the joining pressure and absorbed and held in the molten brazing material Any material can be used.

It is sectional drawing which shows the example of whole structure of the power module manufactured using the board | substrate for power modules which concerns on this invention. It is sectional drawing which shows the process of joining a metal layer (metal laminated body) to a ceramic substrate in the manufacturing method of the board | substrate for power modules which concerns on this invention. It is sectional drawing which shows the state by which an excess brazing material is absorbed by the buffering porous layer. It is sectional drawing which shows the board | substrate for power modules which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Power module 11 Electronic component 12 Solder material 13 Cooler 13a Flow path 14 Plating film 20 Power module substrate 22 Ceramic substrate 24 Metal layer 30 Metal laminate 31 First metal plate 32 Second metal plate 33 Buffering porous layer 33a Solid layer 34 First brazing material layer 35 Second brazing material layer 35a Excess brazing material 36 Third brazing material layer 40 Pressure plate P Circuit pattern

Claims (3)

A ceramic substrate and a metal layer made of Al brazed to the ceramic substrate with a brazing material made of an Al-Si alloy to form a circuit pattern;
The metal layer includes two metal plates and a buffer porous layer made of a homogeneous material of the metal plates and bonded between the metal plates,
The power module substrate, wherein a surplus of the brazing material is absorbed and held near the surface and end face of the buffer porous layer. A method for manufacturing a power module substrate according to claim 1,
A first metal plate and a second metal plate, a buffer porous layer made of the same material of these metal plates and sandwiched between the metal plates, and between the buffer porous layer and the first metal plate or A first brazing filler metal layer disposed on at least one of the buffer porous layer and the second metal plate; and a second brazing filler metal layer disposed on the outer surface of the second metal plate. A metal lamination step of forming a metal laminate,
By laminating the ceramic substrate and the metal layer laminate so that the second brazing material layer is in contact with the ceramic substrate, and heating them while pressurizing them in the thickness direction, each of the metal laminates A bonding step of bonding the metal plate and the buffering porous layer, bonding the second metal plate and the ceramic substrate, and bonding the metal layer to the ceramic substrate. A method for manufacturing a power module substrate.   In the metal lamination step, a third brazing material layer is further arranged between the buffer porous layer and the first metal plate or the other between the buffer porous layer and the second metal plate. The manufacturing method of the board | substrate for power modules of Claim 2 characterized by the above-mentioned.

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