JP5949817B2 - Power module substrate manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a power module substrate.

In general, a power module for supplying power is a semiconductor element that generates a relatively large amount of heat. As this power module substrate, for example, a ceramic substrate made of AlN, Al ₂ O ₃ , Si ₃ N ₄ , SiC, or the like, on which a metal plate such as an aluminum plate is bonded via a brazing material is used. It is done. One of the metal plates bonded to the ceramic substrate is formed with a circuit having a desired pattern by a subsequent etching process to form a circuit layer, and an electronic component (power element such as a semiconductor chip) is mounted thereon. In addition, a heat sink is bonded to the other (circuit layer) of the metal plate bonded to the ceramic substrate.

  In a power module in which an electronic component and a heat sink are joined, heat generated from the electronic component is dissipated by the heat sink. Conventionally, in a power module, the circuit layer and the heat dissipation layer are generally formed of the same plate material. However, in recent years, in order to relieve the thermal stress generated in the ceramic substrate due to the thermal expansion and contraction of the heat dissipation layer, the heat dissipation layer It has been studied to form a thick wall with a buffer function.

  When the thickness of the circuit layer and the thickness of the heat dissipation layer are different, a warp with the thin-walled side (circuit layer side) convex occurs through the heat treatment for brazing (see Patent Document 1). For this reason, the problem of inhibiting the subsequent attachment to a heat sink arises. In addition to the heat applied during manufacturing such as brazing, the same warp occurs in the environment of use as long as it is used for a long time at a relatively high temperature of, for example, 50 ° C.

JP 2002-252433 A

  When joining the power module substrate and the heat sink, a method is adopted in which the power module substrate is placed on the heat sink top plate and the heat sink top plate and the power module substrate heat dissipation layer are brazed. it can. In this case, if the power module substrate is greatly warped, the mounting of the heat sink is hindered as described above. However, even when the power module substrate is flat, the heat sink and the power module are used when brazing to the heat sink. There is a problem that it is likely to be displaced before the substrate is fixed.

  This invention is made | formed in view of such a situation, and it aims at providing the manufacturing method of the board | substrate for power modules which can join a heat sink easily and reliably.

  The power module substrate manufactured by the method of the present invention is a power module substrate in which a circuit layer metal plate and a heat dissipation layer metal plate are laminated and bonded to both surfaces of a ceramic substrate, respectively, The circuit layer metal plate side is warped so as to be convex, and the amount of warpage is 0.1% or more and 0.3% or less in the thickness direction with respect to the length of the long side direction of the power module substrate. It is a size. According to this power module substrate, since it has a warped shape of an appropriate size that does not obstruct the mounting of the heat sink, it is stably placed on the top plate of the heat sink, and the heat sink is securely bonded.

In order to manufacture such a power module substrate, the present invention provides a circuit layer made of an aluminum plate having a purity of 99.99% by mass or more by interposing an Al-SI brazing material on both sides of the ceramic substrate. A laminated body formed by laminating metal plates for heat dissipation layers made of an aluminum plate having a purity higher than that of a metal plate for circuit layers and a metal plate for circuit layers of 99.0% by mass or more, and stacking a plurality of sets of the laminated bodies And pressurizing in the laminating direction while heating in a heated state to join the ceramic substrate and each metal plate in each laminate, and in the brazing step, the laminate includes the circuit The metal plates for the layers or the metal plates for the heat dissipation layer are stacked so as to face each other, and the amount of warpage is 0.1% or more and 0.3% or less in the thickness direction with respect to the length in the long side direction. A method for manufacturing a power module substrate of manufacturing the module substrate.

  According to this method for manufacturing a power module substrate, a thermal stress is generated in each member by heating at the time of joining, and a power module substrate with a small warp that the metal layer side for a circuit layer having a small thickness is convex is manufactured. That is, when the metal plates for circuit layers or the metal plates for heat dissipation layer are stacked so as to be adjacent to each other via a cushion sheet, the direction of stress causing warping is reversed between adjacent laminates, and vice versa. Part of the stresses in the direction cancel each other, and as a result, the amount of warpage can be reduced as compared with a case where all of the stacked bodies are stacked in the same direction. As a result, a power module substrate having an appropriate warp shape that is stable when placed on the top plate of the heat sink without obstructing the mounting of the heat sink is manufactured. In addition, in order to make the pressure transmission between each laminated body uniform between the metal plate for circuit layers and the metal plate for heat dissipation layers, it is a carbon plate, a graphite plate, or these laminated plates which have elasticity and heat resistance. A cushion sheet composed of the above may be sandwiched.

  In this method for manufacturing a power module substrate, it is preferable that the number of the stacked bodies stacked in the brazing step is an even number. The number of stacked layers is preferably 2 or more and 36 or less, more preferably 12. Note that the number of stacked layers is preferably an even number in order to balance the stress that causes warpage between adjacent stacked bodies. When the number of laminated layers exceeds 36, it is not preferable because there is a possibility of collapse during pressurization.

In the method for manufacturing a power module substrate, the brazing step is preferably performed under conditions of a pressure of 24 × 10 ⁴ Pa to 59 × 10 ⁴ Pa and a temperature of 640 ° C. to 655 ° C. By brazing under such conditions, the warpage amount of the power module substrate is 0.1% or more and 0.3% or less in the thickness direction with respect to the length in the long side direction, for example, in the long side direction. It can be controlled to an appropriate size of 30 μm or more and 90 μm or less in the thickness direction with respect to the length of 28 mm. If the pressure in the brazing process is too large, the metal plate is likely to be deformed or cracked, and if it is too small, the warpage increases and there is a risk of poor bonding. Further, if the temperature in the brazing process is too high, breakage tends to occur, and if it is too low, brazing may be insufficient.

  ADVANTAGE OF THE INVENTION According to this invention, the board | substrate for power modules which can join a heat sink easily and reliably can be provided.

It is sectional drawing which shows the power module manufactured using the board | substrate for power modules which concerns on this invention. It is a side view which shows the board | substrate for power modules which concerns on this invention. It is a side view which shows the manufacturing method of the board | substrate for power modules concerning this invention.

  Hereinafter, embodiments of a power module substrate and a method for manufacturing the same according to the present invention will be described. A power module 100 shown in FIG. 1 is bonded to the power module substrate 10 according to the present invention, an electronic component 20 such as a semiconductor chip mounted on the surface of the power module substrate 10, and the back surface of the power module substrate 10. And the heat sink 30. The heat sink 30 is formed by extrusion molding of an aluminum alloy, and a large number of flow paths 30a are formed along the length direction for circulating cooling water.

  The power module substrate 10 has a circuit layer metal plate 12 and a heat dissipation layer metal plate 13 laminated on both sides of a ceramic substrate 11 in the thickness direction, respectively, and has a lower melting point than Al (preferably an Al-SI system). It is joined by brazing material. For example, the thickness of each member is set to 0.635 mm for the ceramic substrate 11, 0.6 mm for the metal plate 12 for the circuit layer, and 1.2 mm for the metal plate 13 for the heat dissipation layer.

The ceramic substrate 11 is made of AlN, Si ₃ N ₄ , Al ₂ O ₃ or the like having a thickness of 0.5 mm to 1.0 mm.

  The circuit layer metal plate 12 is made of an aluminum alloy plate (preferably a 4N—Al plate) having a thickness of 0.1 mm to 1.1 mm. In the power module 100, the circuit layer metal plate 12 is formed into a predetermined circuit pattern by etching or the like, and the electronic component 20 is joined thereto by a solder material or the like.

  The heat radiation layer metal plate 13 is made of a pure aluminum plate having a thickness of 0.1 mm or more and 5.0 mm or less and a purity of 99.0 wt% or more, which is thicker than the circuit layer metal plate 12. In the power module 100, the heat sink 30 is joined to the heat radiating layer metal plate 13 by brazing or the like.

  As shown in FIG. 2, the power module substrate 10 in which the metal plates 12 and 13 are bonded to the ceramic substrate 11 is warped so that the circuit layer metal plate 12 side is convex. The warpage amount C is 0.1% or more and 0.3% or less in the thickness direction with respect to the length of the power module substrate 10 in the long side direction (the length of one side when the plane is square). (For example, the size in the thickness direction is 30 μm or more and 90 μm or less with respect to the length L = 28 mm in the long side direction). Note that FIG. 2 greatly exaggerates the warpage amount C with respect to the length L so that the shape characteristics of the power module substrate 10 become clear.

  As shown in FIG. 2, the power module substrate 10 has a slight warping shape, so that the power module substrate 10 is stably disposed on the heat sink 30, and the warpage amount is large enough to prevent the bonding to the heat sink 30. Therefore, the heat sink 30 can be joined accurately and accurately.

  A method for manufacturing the power module substrate 10 having such a warped shape will be described. The power module substrate 10 is a laminate formed by laminating a metal plate 12 for a circuit layer and a metal plate 13 for a heat dissipation layer thicker than the metal plate 12 for a circuit layer with a brazing material interposed between both surfaces of the ceramic substrate 11. A brazing step of joining the ceramic substrate 11 and the metal plates 12 and 13 in the laminate 10A by forming 10A and applying pressure in the lamination direction while heating in a state where a plurality of sets of laminates 10A are stacked. Have.

In this brazing step, the laminated body 10A is stacked such that the circuit layer metal plates 12 or the heat dissipation layer metal plates 13 face each other as shown in FIG. The manufacturing conditions in the brazing process are preferably set as follows.
Pressure (load): 24.5 × 10 ⁴ Pa or more and 58.8 × 10 ⁴ Pa or less Temperature: 640 ° C. or more and 655 ° C. or less Number of layers of the laminate 10A: 2 or more, 36 or less, preferably even number, particularly preferably 12

  A cushion sheet P is disposed between the stacked laminates 10A. As the cushion sheet P, for example, a heat-resistant carbon plate or graphite plate, or a laminated plate thereof can be used.

  Then, in a state where these laminates 10A are alternately laminated, heating and brazing while applying pressure as shown by arrows in FIG. 3, the thickness direction with respect to the length L = 28 mm in the long side direction The power module substrate 10 having a warpage amount C of 30 μm or more and 90 μm or less (that is, a warpage amount C in the thickness direction with respect to the length L in the long side direction is 0.1% or more and 0.3% or less) is manufactured. can do.

  As the metal plates 12 and 13 having different thicknesses are thermally expanded and contracted to be brazed, a thermal stress is generated. As shown in FIG. A convex shape is formed on the plate 12 side. However, the amount of warpage can be reduced by alternately laminating and brazing the laminated body 10A.

  For example, when brazing in the state where the front and back of a plurality of laminated bodies 10A are laminated in the same manner as in the past, the manufactured power module substrate has a warpage amount of 150 μm with respect to a length of 28 mm in the long side direction. became. On the other hand, when brazed in a state where the front and back of the laminate 10A are alternately laminated as described above, the manufactured power module substrate 10 has a warpage amount with respect to a length of 28 mm in the long side direction. It could be reduced to 30 μm.

As described above, according to the present invention, it is possible to provide a power module substrate capable of easily and reliably joining a heat sink.
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.

DESCRIPTION OF SYMBOLS 10 Power module substrate 10A Laminate body 11 Ceramic substrate 12 Circuit layer metal plate 13 Heat radiation layer metal plate 20 Electronic component 30 Heat sink 30a Flow path 100 Power module C Warpage amount L Long side length P Cushion sheet

Claims (3)

A metal plate for a circuit layer made of an aluminum plate having a purity of 99.99% by mass or more by interposing an Al—SI brazing material on both sides of the ceramic substrate, and a purity higher than that of the metal plate for a circuit layer is 99.0 % by mass. % In each laminate by forming a laminate formed by laminating metal plates for heat dissipation layers composed of aluminum plates of at least%, and pressing in the stacking direction while heating in a state where a plurality of sets of the laminates are stacked. Having a brazing step of joining the ceramic substrate and each metal plate;
In the brazing step, the laminated body is stacked such that the metal plates for circuit layers or the metal plates for heat dissipation layer face each other, and the amount of warpage is in the thickness direction with respect to the length in the long side direction. A power module substrate manufacturing method, characterized by manufacturing a power module substrate of 0.1% to 0.3%.   The method for manufacturing a power module substrate according to claim 1, wherein the number of the stacked bodies stacked in the brazing step is an even number. 3. The power module substrate according to claim 1, wherein the brazing step is performed under conditions of a pressure of 24 × 10 ⁴ Pa to 59 × 10 ⁴ Pa and a temperature of 640 ° C. to 655 ° C. ^4. Method.

Images