JP6361532B2 - Manufacturing method of power module substrate with heat sink - Google Patents

Description

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

  Generally, a metal plate that forms a circuit layer is bonded to one surface of a ceramic substrate that is an insulating substrate, and a heat radiating plate is bonded to the power module via a metal plate that forms a heat radiating layer. A power module substrate with a heat sink is used, and a semiconductor chip such as a power element is mounted on a circuit layer of the power module substrate with a heat sink via a solder material to manufacture a power module.

  In such a power module, the warpage caused by the difference in linear expansion coefficient between the ceramic substrate of the power module substrate and the heat radiating plate is generated, thereby obstructing the adhesion to the cooler and the like and reducing the heat radiation performance. Is an issue. Conventionally, one power module substrate joined to one heat sink has been used. However, in order to be able to handle a plurality of power module substrates as a single unit, a plurality of heat radiator substrates are used. However, even in this case, warpage occurring in the power module substrate with a heat sink is a problem.

  In this regard, in Patent Document 1, as a countermeasure against warpage, a jig having a concave R surface is brought into contact with a heat radiating plate (heat radiator) for each power module substrate (metal-ceramic bonding substrate), and A jig having a convex R surface is brought into contact with a circuit layer (metal circuit board) and pressed with a jig having a plurality of concave R surfaces and a jig having a plurality of convex R surfaces. It describes that one heat sink and a plurality of power module substrates are joined.

JP 2013-197246 A

  However, in the power module substrate with a heat sink manufactured by the method described in Patent Document 1, the surface of the circuit layer and the surface of the heat sink are respectively pressed by a plurality of R surfaces provided on the jig. However, the other portions are pressurized by a plane provided on the jig, so that the surface of the heat radiating plate is deformed into a wavy state. For this reason, even if it is possible to reduce the overall warpage, when the power module substrate with a heat sink is fastened to a cooler or the like, there is a gap between the waved surface of the heat sink and the surface of the cooler. Therefore, there is a concern that the heat dissipation performance is lowered.

  The present invention has been made in view of such circumstances, and it is possible to reduce the warpage generated in the power module substrate with a heat dissipation plate obtained by joining a plurality of power module substrates to a single heat dissipation plate. It aims at providing the manufacturing method of the board | substrate for power modules with a heat sink which can maintain favorably.

  The present invention provides a power module substrate in which a circuit layer is disposed on one surface of a ceramic substrate and a heat dissipation layer is disposed on the other surface of the ceramic substrate. A method for manufacturing a power module substrate with a heat sink that is joined by opening a plurality of layers, wherein each power module substrate is stacked and placed on the heat sink, and heated while pressing in the stacking direction. A brazing step of brazing the power module substrate and the heat dissipation plate, wherein the brazing step includes an upper pressure plate disposed on the circuit layer side and a lower pressure plate disposed on the heat dissipation plate side. The laminated body is pressed by sandwiching the laminated body between a pair of pressure plates composed of a pressure plate, and the upper pressure plate has a small spherical convex surface that presses the surface of the circuit layer, and the small spherical convex surface. Big curvature half A large spherical convex surface that presses the heat radiating plate, and the lower pressure plate is a small sphere formed with a radius of curvature corresponding to the small spherical convex surface at a position facing the small spherical convex surface. A concave warp having a concave surface and a large spherical concave surface formed with a radius of curvature corresponding to the large spherical convex surface at a position facing the convex surface of the large spherical surface, and the circuit layer side as a whole on the laminate. Pressurize in a state where

When using a power module with a heat sink (power module), the surface of the heat sink is flat without causing warpage as a whole from the viewpoint of maintaining good adhesion between the power module substrate with a heat sink and the cooler. Although it is desirable to maintain, even if warpage occurs, it is more convex than the concave warp (convex warp on the circuit layer side) with respect to the cooler side in terms of maintaining adhesion. It is desirable that the shape be warped.
In this regard, in the power module substrate of the present invention, at the time of joining the heat sink and the power module substrate, the portion where each power module substrate is laminated on these laminates is referred to as the small convex surface of the upper pressure plate. While sandwiching between the small spherical concave surface of the lower pressure plate, the other part is sandwiched between the large spherical convex surface of the upper pressure plate and the large spherical concave surface of the lower pressure plate. That is, at each position of the small spherical convex surface and the small spherical concave surface, the large spherical convex surface and the large spherical concave surface, the laminated body is caused to have a concave warp with the circuit layer side in the stacking direction as the upper side, and the brazing material is melted. By cooling after holding for a predetermined time at a temperature higher than or equal to the temperature to be released, it is possible to reduce both the warpage caused by the power module substrate and the warpage caused by the heat sink after releasing the pressurization state in the stacking direction. Thus, a power module substrate with a heat sink can be obtained in a state where the surface of the heat sink is flat or in a state where the circuit layer is on the upper side and warps in a concave shape.
That is, in the power module substrate with a heat sink manufactured in this way, a plurality of power module substrates are joined to one heat sink without causing a complicated warp. In addition, even when the circuit layer is warped concavely with the circuit layer as the upper side, the amount of warpage can be reduced. Therefore, since the adhesiveness with a cooler etc. can be maintained favorable, heat dissipation performance can be maintained favorable.

  In the method for manufacturing a power module substrate with a heat sink according to the present invention, a boundary between the small spherical convex surface and the large spherical convex surface of the upper pressure plate is separated, and the small spherical convex surface and the large spherical convex surface are relative to each other. It is good to be provided so that movement is possible.

  By providing the small spherical convex surface and the large spherical convex surface of the upper pressure plate so that they can move relative to each other, the portion where each power module substrate is laminated on the laminate of the heat dissipation plate and the power module substrate is a small spherical convex surface. And the small spherical concave surface can be individually inserted between the large spherical convex surface and the large spherical concave surface, and the pressing force can be loaded separately. it can. Therefore, the laminated body can be uniformly pressed without causing variation in the pressing force at the positions of the small spherical convex surface and the small spherical concave surface, the large spherical convex surface and the large spherical concave surface. The warp that occurs can be reliably reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the curvature which arises in the power module substrate with a heat sink which joined the board | substrate for several power modules to one heat sink can be reduced, and contact | adherence with a cooler etc. and a power module substrate with a heat sink Therefore, the adhesion between the power module substrate with a heat radiating plate and the cooler can be maintained well, and the heat radiating performance can be kept good.

It is sectional drawing which shows the power module using the board | substrate for power modules with a heat sink. It is sectional drawing explaining the manufacturing method of the board | substrate for power modules with a heat sink which concerns on this invention, (a) is before joining of a board | substrate for power modules and a heat sink, (b) shows the state after joining. It is a side view explaining the jig | tool used for the manufacturing method of the board | substrate for power modules with a heat sink which concerns on this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a power module substrate 100 with a heat sink manufactured by the method for manufacturing a power module substrate with a heat sink according to the present invention includes a plurality (two in the illustrated example) of power module substrates 10 and these. The power module substrate 10 is joined to a single heat sink 20. And power module 100A is manufactured by mounting semiconductor elements 60, such as a semiconductor chip, on the surface of power module substrate 100 with a heat sink.

  In the manufacturing process of the power module substrate 100 with a heat sink, first, as shown in FIG. 2A, the power module substrate 10 is manufactured, and the power module substrate 10 and the heat sink 20 are brazed. Then, a power module substrate 100 with a heat sink as shown in FIG.

As shown in FIG. 1, each power module substrate 10 includes a ceramic substrate 11, a circuit layer 12, and a heat dissipation layer 13. The circuit layer 12 is bonded to one surface of the ceramic substrate 11, and the ceramics The heat dissipation layer 13 is bonded to the other surface of the substrate 11.
The first ceramic substrate 11 constituting the power module substrate 10 is made of nitride ceramics such as AlN (aluminum nitride) and Si ₃ N ₄ (silicon nitride), or oxide such as Al ₂ O ₃ (alumina). Ceramics can be used, and the thickness is set in the range of 0.2 mm to 1.5 mm.

The circuit layer 12 is formed by bonding a pure aluminum or aluminum alloy metal plate to the first ceramic substrate 11. In the present embodiment, for example, a metal plate having a thickness of 0.1 mm to 1.5 mm made of aluminum having a purity of 99.99 mass% or more (so-called 4N aluminum) is used.
The heat dissipation layer 13 is formed by bonding a pure aluminum or aluminum alloy metal plate to the first ceramic substrate 11. In the present embodiment, for example, a metal plate made of aluminum (4N aluminum) having a purity of 99.99% by mass or more and having a thickness set within a range of 0.1 mm to 2.0 mm is used. It is formed by brazing to the first ceramic substrate 11.

  The heat sink 20 is for radiating the heat of the power module 110, and is made of, for example, an aluminum alloy (A3003, A6063 alloy, etc.). In this embodiment, the thickness of the A6063 alloy is 1.0 mm to 20 mm. It is formed in a flat plate shape set within the range. In addition, the shape of the heat sink 20 is not specifically limited, For example, it can also form in the box shape through which cooling media, such as water, distribute | circulate.

And the semiconductor element 60 is soldered to the surface of each circuit layer 12 of this power module substrate 100 with a heat sink, and it becomes the power module 110.
Various semiconductors such as IGBTs (Insulated Gate Bipolar Transistors), MOSFETs (Metal Oxide Field Effect Transistors), FWDs (Free Wheeling Diodes) 60, etc. are selected according to the required functions. The solder material for joining the semiconductor element 60 is, for example, a Sn—Sb, Sn—Ag, Sn—Cu, Sn—In, or Sn—Ag—Cu solder material (so-called lead-free solder material). It is said.

Next, a method for manufacturing the power module substrate 100 with a heat sink having such a configuration will be described.
First, as shown in FIG. 2A, a power module substrate 10 and a heat sink 20 are prepared.
For example, the power module substrate 10 is formed by laminating a metal plate to be the circuit layer 12 on one surface of the ceramic substrate 11 via a brazing material, and on the other surface of the ceramic substrate 11 via a brazing material 13. The layers are formed by brazing and bonding each layer by laminating metal plates to be heated and heating them to a bonding temperature in a vacuum atmosphere in a state where these are pressed in the laminating direction.
The brazing material for joining these layers may be used in the form of an Al—Si based alloy foil. In addition, the applied pressure at the time of brazing joining is, for example, 0.1 MPa to 4.3 MPa, the joining temperature is 610 ° C. to 650 ° C., and the heating time is 1 minute to 60 minutes.

  And in order to join the board | substrate 10 for power modules comprised in this way to the heat sink 20, the laminated body S which arranged the two board | substrates 10 for power modules on the upper surface of the heat sink 20 via the brazing material, For example, the jig 110 shown in FIG. 3 is pressed in the stacking direction.

  The jig 110 includes a base plate 111, guide posts 112 that are vertically attached to the four corners of the upper surface of the base plate 111, and a pressing plate that is supported by the guide posts 112 so as to be movable up and down at the upper ends of the guide posts 112. 113, and a pair of pressure plates 120A and 120B sandwiching the laminate S between the base plate 111 and the pressure plate 113 are disposed. Further, a fastening member 114 is fastened to a screw portion cut at the upper end of the guide post 112, and a cushion sheet 115 is disposed between the pressure plate 120A and the pressure plate 113, and the pair of pressure plates 120A and 120B are used. The pressing force is adjusted by tightening the fastening member 113.

  Each of the pair of pressure plates 120A and 120B is formed by laminating a carbon plate on the surface of a stainless steel material, and the upper side plate disposed on the circuit layer 12 side of the laminate S of the power module substrate 10 and the heat radiating plate 20. It consists of a pressure plate 120A and a lower pressure plate 120B disposed on the heat radiating plate 20 side. The upper pressure plate 120A includes a small spherical convex surface 21s that presses the surface of the circuit layer 12, and a large spherical convex surface 22s that is formed with a larger radius of curvature than the small spherical convex surface 21s and presses the heat dissipation plate 20. It is said. On the other hand, the lower pressure plate 120B has a small spherical concave surface 23s formed with a radius of curvature corresponding to the small spherical convex surface 21s at a position facing the small spherical convex surface 21s, and a large sphere at a position facing the large spherical convex surface 22s. A large spherical concave surface 24s formed with a radius of curvature corresponding to the convex surface 22s is used.

  In other words, the concave warpage with the circuit layer 12 side on the upper side is sandwiched between the power module substrate 10 and the heat radiating plate 20 of the laminate S between the opposing small spherical convex surface 21s and the small spherical concave surface 23s. It can be pressed into the generated state. On the other hand, the circuit layer 12 is sandwiched between the large spherical convex surface 22s and the large spherical concave surface 24s facing each other with a portion other than the laminated portion of the power module substrate 10 and the heat radiating plate 20 of the laminated body S (only the heat radiating plate 20). It can be pressed in a state in which a concave warp with the side as the upper side is generated. Therefore, by sandwiching the laminate S between the upper pressure plate 120A and the lower pressure plate 120B, as shown in FIG. 3, the laminate S as a whole has a concave warp with the circuit layer 12 side as the upper side. It is held in the let state.

  Further, the small spherical convex surface 21s and the large spherical convex surface 22s of the upper pressure plate 120A are separated from each other at the boundary, and the small spherical convex surface 21s and the large spherical convex surface 22s are provided so as to be relatively movable in the vertical direction. It has been. Specifically, as shown in FIG. 3, by providing an insertion hole 121h through which the board pressing portion 122 with the small spherical convex surface 21s can be inserted into the heat sink pressing portion 121 with the large spherical convex surface 22s. The heat radiating plate pressing portion 121 and the substrate pressing portion 122 are provided so as to be relatively movable. Correspondingly, the cushion sheet 115 disposed between the upper pressure plate 120A and the pressing plate 113 is also provided separately at the boundary between the heat radiation plate pressing portion 121 and the substrate pressing portion 122. The plate pressing part 121 and the substrate pressing part 122 can be pressed individually.

  As a result, in the laminated body S of the heat sink 20 and the power module substrate 10, the portion where each power module substrate 10 is laminated is sandwiched and pressed between the small spherical convex surface 21s and the small spherical concave surface 23s. The pressure can be applied, and the other parts can be individually sandwiched between the large spherical convex surface 22s and the large spherical concave surface 24s to apply the pressing force. Accordingly, it is possible to uniformly pressurize the laminate S without causing variations in the pressing force at the positions of the small spherical convex surface 21s and the small spherical concave surface 23s, the large spherical convex surface 22s, and the large spherical concave surface 24s.

  The small spherical convex surface 21s and the small spherical concave surface 23s are preferably formed with the same radius of curvature, and the radius of curvature R1 is not less than 350 mm and not more than 550 mm. Also, the large spherical convex surface 22s and the large spherical concave surface 24s are preferably formed with the same curvature radius, and the curvature radius R2 is set to 600 mm or more and 1000 mm or less. Thus, since the radius of curvature R2 has a radius of curvature larger than the radius of curvature R1, as shown in FIG. 3, the large spherical convex surface 22s and the large spherical concave surface 24s are the small spherical convex surface 21s and the small spherical concave surface. The curved surface is gentler than 23s.

  And in the manufacturing method of the board | substrate for power modules with a heat sink of this embodiment, by setting the laminated body S of the board | substrate 10 for power modules and the heat sink 20 to the jig | tool 110, it is with a heat sink at the time of manufacture. Warpage generated in the power module substrate 100 can be suppressed.

Specifically, first, a single heat sink 20 is placed on the lower pressure plate 120B disposed on the lower side of the jig 110, and Al—Si is spaced apart in the surface direction of the heat sink 20. A plurality of power module substrates 10 are stacked and placed via a brazing filler metal foil (not shown). Then, the lower pressure plate 120B and the upper pressure plate are obtained by bringing the upper pressure plate 120A into contact with the circuit layer 12 side of the laminate S of the heat radiation plate 20 and the power module substrate 10 and tightening the fastening member 114. The laminated body S is sandwiched between 120A. At this time, the laminated body S of the heat sink 20 and each power module substrate 10 is pressed in the thickness direction (lamination direction) by the pair of pressure plates 120A and 120B, so that each power module in the laminated body S is provided. The portion where the substrate 10 and the heat sink 20 are stacked is sandwiched between the small spherical convex surface 21s and the small spherical concave surface 23s, and the other portion (the portion of the heat sink 20 only) is the large spherical convex surface 22s. By being sandwiched between the spherical concave surfaces 24 s, the concave warp with the circuit layer 12 side in the stacking direction on the upper side is generated at each position. And the laminated body S is heated in this pressurization state, and the thermal radiation layer 13 and the thermal radiation board 20 of the board | substrate 10 for power modules are joined by brazing.
In the present embodiment, the brazing is performed using an Al-10% Si brazing material, in a vacuum atmosphere under a load of 0.1 MPa to 3 MPa and a heating temperature of 580 ° C. to 620 ° C. Done.

  Next, the joined body of the power module substrate 10 and the heat radiating plate 20 is cooled to room temperature (25 ° C.) in a state where the joined body is attached to the jig 110, that is, in a state where deformation is caused. In this case, the joined body of the power module substrate 10 and the heat radiating plate 20 is pressed in the thickness direction by the jig 112, and is restrained in a state in which deformation as a concave warp is generated as a whole. For this reason, the shape of the joined body of the power module substrate 10 and the heat radiating plate 20 due to cooling does not seem to change, but it is pressurized against stress and can be deformed as warpage during cooling. As a result of being constrained in the absence, plastic deformation occurs.

In the power module substrate 100 with a heat sink manufactured in this way, both the warp caused by the power module substrate 10 and the warp caused by the heat sink 20 can be reduced. Even when the surface is flat, or as shown in FIG. 2B, the warp amount is reduced even in a state where the circuit layer 12 side is on the upper side and warped in a concave shape, and the warp generated during manufacturing is reduced.
Thus, in the power module substrate with a heat sink manufactured by the manufacturing method of the present embodiment, although a plurality of power module substrates 10 are joined to one heat sink 20, The amount of warpage can be reduced without causing a complicated warp and even when the circuit layer 12 warps in a concave shape with the circuit layer 12 as the upper side. Therefore, since the adhesiveness with a cooler etc. can be maintained favorable, heat dissipation performance can be maintained favorable.

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-described embodiment, the case where two power module substrates 10 are bonded to one heat sink 20 has been described. However, the power module substrate 10 bonded on the heat sink 20 has 2 It may be more than one.

DESCRIPTION OF SYMBOLS 10 Power module substrate 11 Ceramic substrate 12 Circuit layer 13 Heat radiation layer 20 Heat radiation plate 21s Small spherical convex surface 22s Large spherical convex surface 23s Small spherical concave surface 24s Large spherical concave surface 60 Semiconductor element 100 Power module substrate with heat sink 100A Power module 110 Jig 111 Base plate 112 Guide post 113 Press plate 114 Fastening member 115 Cushion sheet 120A Upper pressure plate 120B Lower pressure plate 121 Heat radiation plate pressing portion 121h Insertion hole 122 Substrate pressing portion S Laminate

Claims (2)

A plurality of power module substrates, each having a circuit layer disposed on one surface of a ceramic substrate and a heat radiation layer disposed on the other surface of the ceramic substrate, are spaced apart in a plane direction on a single heat radiation plate. A method for manufacturing a power module substrate with a heat sink to be joined,
It has a brazing step of brazing the power module substrate and the heat sink by heating a laminate in which each power module substrate is placed on the heat sink while being pressed in the stacking direction. ,
In the brazing step, the laminate is sandwiched between a pair of pressure plates composed of an upper pressure plate disposed on the circuit layer side and a lower pressure plate disposed on the heat dissipation plate side. Pressing
The upper pressure plate has a small spherical convex surface that presses the circuit layer surface, and a large spherical convex surface that is formed with a larger radius of curvature than the small spherical convex surface and presses the heat dissipation plate,
The lower pressure plate corresponds to the large spherical convex surface at a position facing the small spherical convex surface, a small spherical concave surface formed with a radius of curvature corresponding to the small spherical convex surface, and a position facing the large spherical convex surface. A large spherical concave surface formed with a radius of curvature;
A substrate for a power module with a heat sink that pressurizes the laminated body in a state where a concave warp with the circuit layer side as an upper side is generated as a whole.   The heat dissipation according to claim 1, wherein a boundary between the small spherical convex surface and the large spherical convex surface of the upper pressure plate is separated, and the small spherical convex surface and the large spherical convex surface are provided so as to be relatively movable. Manufacturing method of board | substrate for power modules with board.

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