JP5914968B2 - Power module substrate with heat sink and manufacturing method thereof - Google Patents

Description

The present invention, high-current, relates Ruhi sink with a power module substrate and a manufacturing method thereof used in a semiconductor device for controlling the high voltage.

  As a conventional power module, an aluminum metal layer as a circuit layer is laminated on one surface of a ceramic substrate, and an electronic component such as a semiconductor chip is soldered on the circuit layer, and the other surface of the ceramic substrate. There is known a structure in which an aluminum metal layer serving as a heat dissipation layer is formed and a heat sink is joined to the metal layer.

As this type of power module, for example, a power module described in Patent Document 1 is known. In the power module described in Patent Document 1, comb-like heat radiation fins are formed on a metal member as a heat sink to be bonded to the ceramic substrate. Such radiating fins are formed by, for example, forging, casting, extrusion molding or the like of an aluminum alloy, and a plurality of radiating fins are erected uniformly over the entire surface of the metal member.
However, when the heat sink is manufactured by extrusion molding or the like, a large-scale apparatus is required, and the degree of freedom in design is small, for example, the metal member and the heat radiation fin must be formed of the same material.

Therefore, Patent Documents 2 and 3 propose heat sinks in which bar-shaped or plate-shaped heat radiation fins are caulked on the surface of a metal member, and power modules using such heat sinks are known.
In this case, the heat sink integrated by caulking the end portions of the radiating fins in the recesses provided in the metal member is formed, so that it can be formed at low cost. Moreover, the heat radiation fin can be erected at an arbitrary position of the metal member, and the metal member and the heat radiation fin can be formed of different metals.
Patent Document 4 discloses a heat sink that brazes a flat coil fin member to a fitting groove of a heat transfer substrate.

Japanese Patent Laid-Open No. 11-204700 JP 2006-310486 A JP 2002-26550 A JP 2010-27998 A

  However, in the heat sinks described in Patent Document 2 and Patent Document 3, since the end portions of the radiating fins are caulked and mechanically fixed to the recesses formed in the metal member, the adhesion of the caulking portions is poor, and the thermal resistance is low. It becomes large and the cooling performance tends to be low. Further, when corrosion occurs in the caulking portion, there is a problem that a hole is formed in the metal member and the coolant leaks from the heat sink. Moreover, in the heat sink of patent document 4, the fillet part between a heat-transfer board | substrate and a flat coil fin member had the subject at the point of the reduction of the further thermal resistance.

The present invention has been made in view of such circumstances, has a high degree of design freedom, can be easily manufactured, and has a heat module with a heat sink that uses a heat sink that can improve cooling performance, and its A manufacturing method is provided.

The present invention includes a heat sink, a substrate for a power module with a heat sink to the power module substrate is joined with a ceramic substrate, the heat sink, together with the recess of the multiple is formed on the metal member, the recess A raised portion formed by raising the surface of the metal member is formed so as to surround the concave portion, and a fin material partially fitted in the concave portion is brazed, and the metal member and the fin material A fillet portion between the metal member and the fin member is formed so as to include the raised portion, and a surface of the metal member opposite to the fin material is bonded to the power module substrate.

  As a result, the metal member and the fin material are joined without a gap by the brazing material, and the fillet portion between the metal member and the fin material can be formed long by the raised portion of the metal member. The thermal resistance between the metal member and the fin material can be reduced, and the cooling efficiency of the heat sink can be improved.

Further, Oite this onset bright, the fin material, may at least part of its surface, than the metal member is formed of a low corrosion potential material.
By forming the surface of the fin material with a material having a lower corrosion potential than that of the metal member, the material portion having the lower corrosion potential that constitutes the fin material is sacrificially corroded, and the corrosion of the metal member can be suppressed. Since the fin material corrodes before the metal member, the metal member can be prevented from pitting and leakage of the coolant to the power module substrate side can be prevented.

Furthermore, in the method for manufacturing a power module substrate with a heat sink of the present invention, a metal member in which a brazing material is bonded to the surface of the core material is formed with a plurality of concave portions in which the brazing material is arranged on the bottom surface by pressing, a peripheral portion of the concave portion by the processing of the concave portion, wherein after the ridge is formed by raised surface of the metallic member is formed to surround the recess, by fitting a portion of the full fin material in the recess, the metal By heating while pressing in the thickness direction in a state where a power module substrate having a ceramic substrate is laminated via a brazing material on a surface opposite to the fin material of the member, the metal member and the fin material The heat sink is formed by brazing , and the metal member is bonded to the power module substrate .

When the concave portion is formed in the metal member by press working, the material flows and a raised portion is formed at the peripheral portion of the concave portion. Since the brazing material is bonded to the metal member, the brazing material is also disposed on the bottom surface of the recess. When a part of the fin material is fitted into the recess and pressed and heated, the molten brazing material interposed between the bottom of the recess and the fin material is pushed out and flows into the gap between the recess and the fin material, and the metal The brazing material on the surface of the member is also drawn by the surface tension and filled in the gap. Further, the brazing material rises on the surface of the fin material at the joint portion between the metal member and the fin material and is guided by the raised portion of the concave portion, so that a fillet portion can be formed.
Moreover, in the formation of the concave portion on the metal member by press working, the concave portion can be formed only in the portion arranged directly under the power module substrate, and the degree of freedom in designing the fin material arrangement is high. A simple heat sink can be manufactured.

In this case, during brazing of the metal member and the fin material constituting the heat sink, it is possible to simultaneously bond the substrate metal member and the power module, to produce a power module substrate with a heat sink in a single heating Is possible, and the work efficiency is excellent.

  According to the present invention, the metal member and the fin material can be joined without a gap and by a joining portion having a long fillet portion, so that the cooling performance can be improved.

It is a longitudinal cross-sectional view of the board | substrate for power modules with a heat sink of embodiment of this invention. It is a principal part enlarged view of a heat sink. It is a figure explaining the metal member which comprises a heat sink, (a) is the clad material before a process, (b) is a longitudinal cross-sectional view, (c) is a front view. It is a figure explaining the manufacturing method of a heat sink. It is a principal part enlarged view of the heat sink using the fin material by the clad material of the coating | covering material with a low corrosion potential. It is a principal part enlarged view of the heat sink formed only with the coating | coated material with a low corrosion potential only at the front-end | tip part of a fin material.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a power module 1 manufactured according to the present invention. The power module 1 of FIG. 1 includes a power module substrate 3 having a ceramic substrate 2 made of ceramics, an electronic component 4 such as a semiconductor chip mounted on the surface of the power module substrate 3, and a power module substrate. 3 and a heat sink 5 joined to 3.

  In the power module substrate 3, metal layers 6 and 7 are laminated on both surfaces of the ceramic substrate 2, one of the metal layers 6 becomes a circuit layer, and the electronic component 4 is bonded to the surface thereof. The other metal layer 7 is a heat radiating layer, and the heat sink 5 is attached to the surface thereof.

The ceramic substrate 2 is formed of, for example, nitride ceramics such as AlN (aluminum nitride) and Si ₃ N ₄ (silicon nitride), or oxide ceramics such as Al ₂ O ₃ (alumina).
Both metal layers 6 and 7 are made of aluminum having a purity of 99.90% by mass or more. According to JIS standards, 1N90 (purity 99.90% by mass or more: so-called 3N aluminum) or 1N99 (purity 99.99% by mass). Above: so-called 4N aluminum) can be used.

The individual dimensions of the ceramic substrate 2 and the two metal layers 6 and 7 with respect to the planar size and thickness are not particularly limited, but one side of both metal layers 6 and 7 is formed in a substantially square shape of about 250 mm. The ceramic substrate 2 is formed in a rectangular shape slightly larger than both metal layers 6 and 7. The thickness of the ceramic substrate 2 is, for example, 635 μm, and the thicknesses of both metal layers 6 and 7 are 600 μm.
Further, both metal layers 6 and 7 are bonded to the ceramic substrate 2 by punching them into a desired outer shape by pressing, or after joining a flat plate to the ceramic substrate 2, the desired layers are etched by etching. Either of the methods can be adopted.

  Further, the ceramic substrate 2 and the metal layers 6 and 7 serving as the circuit layer and the heat dissipation layer are made of brazing material such as Al—Si, Al—Ge, Al—Cu, Al—Mg, or Al—Mn It is brazed.

  For joining the metal layer 6 and the electronic component 4, a solder material such as Sn—Cu, Sn—Ag, Sn—Ag—Cu, Zn—Al, or Pb—Sn is used. Reference numeral 8 in the figure indicates the solder joint layer. The electronic component 4 and the terminal portion of the metal layer 6 are connected by a bonding wire (not shown) made of aluminum or the like.

On the other hand, the heat sink 5 is formed by fixing a plurality of fin materials 55 to the metal member 50.
As shown in FIG. 3, the metal member 50 is a clad material formed by adhering a brazing material 52 to both surfaces of a core material 51 of an aluminum plate before the fin material 55 is joined. Is formed of aluminum having a purity of 99% by mass (so-called 2N aluminum) or less. For example, aluminum of 3000 series alloy in JIS standard is used. The brazing material 52 is made of Al—Si, Al—Si—Mg, or the like. The thickness of the core material 51 is, for example, 900 μm, the thickness of the brazing material 52 on both sides is 50 μm, and the metal member 50 is formed with a thickness of 1 mm.

Further, as shown in FIG. 3, a plurality of concave portions 53 to which the fin material 55 is fixed are formed on one side of the metal member 50 by pressing, and the peripheral portion of the concave portion 53 is made of a material at the time of pressing. Is formed so as to surround the concave portion 53.
Here, the height of the raised portion 54 is desirably 50 μm or more in order to form a long joint portion between the fin member 55 and the metal member 50 by the fillet portion, and the brazing material surely crawls up the raised portion 54. The thickness is preferably 150 μm or less.
The fin material 55 is formed in a pin shape that fits into the concave portion 55 of the metal member 50. For example, the fin member 55 is formed to have a diameter of 1 mm and a height of 8 to 10 mm by cutting a wire member into a certain length. The surface of the member 50 is fixed vertically at a pitch of about 3 mm. Further, at least a part of the surface of the fin material 55 is formed of a material having a lower corrosion potential than that of the metal member 50 (core material 51). In the example shown in FIGS. 1 to 4, the entire fin material 55 is formed of a 7000 series alloy that is aluminum having a purity of 99% by mass or less as a material having a lower corrosion potential than the metal member 50.
In addition, at least a part of the surface of the fin material can be formed of aluminum of 4000 series alloy as a material having a lower corrosion potential than that of the metal member 50 with respect to the metal member 50 made of 3000 series alloy aluminum.

Next, a method for manufacturing the power module substrate with a heat sink configured as described above will be described.
First, as shown in FIG. 3A, a clad material formed by bonding a brazing material 52 to both surfaces of a core material 51 of an aluminum plate is prepared. A plurality of recesses 53 are formed by pressing the punch 9 by pressing the clad material. As shown in FIG. 3B, a bulge 54 is formed at the peripheral edge of these recesses 53 formed by pressing during pressing. In order to reliably form the raised portion 54, coining may be performed using a convex portion corresponding to the concave portion 53 and an upper mold in which a concave portion corresponding to the raised portion 54 is formed on the peripheral edge portion of the convex portion. desirable.
Here, the brazing material 52 is arranged not only on the surface of the metal member 50 but also on the bottom surface of the recess 53.

Next, as shown in FIG. 4, the fin material 55 to which the flux 56 is applied is partially fitted in each of the recesses 53 provided on one side of the metal member 50 in this manner, and the metal member On the opposite surface of 50, the power module substrate 3 in which metal layers are bonded to both surfaces of the ceramic substrate 2 in advance is held in a laminated state. In this holding state, while pressing them at 0.5 × 10 ^{5 to} 5 × 10 ⁵ Pa in the thickness direction, for example, by heating in a vacuum at a brazing temperature of 610 ° C. for several minutes, The fin members 55 are brazed, and the metal member 50 and the metal layer 7 of the power module substrate 3 are brazed.
In this case, by partially fitting the fin material 55 to the recess 53 and pressurizing and heating, the molten brazing material 52 interposed between the bottom surface of the recess 53 and the fin material 55 is pushed out, and the recess 53 And the brazing material 52 on the surface of the metal member 50 are drawn by the surface tension and filled in the gap. Further, the brazing material 52 rises on the surface of the fin material 55 at the joint portion between the metal member 50 and the fin material 55 by being guided by the raised portion 54 of the recess 53, and a fillet portion 57 as shown in FIG. 2 is formed. .

As a result, the metal member 50 and the fin material 55 are joined together without any gap by the brazing material 52, and the joint portion can be formed long by the fillet portion 57 between the metal member 50 and the fin material 55. The thermal resistance between the metal member 50 and the fin material 55 can be reduced, and the cooling efficiency of the heat sink 5 can be improved.
In addition, since the metal member 50 and the fin material 55 constituting the heat sink 5 can be brazed at the same time, the metal member 50 and the metal layer 7 constituting the power module substrate 3 can be joined at the same time. It is possible to manufacture a power module substrate with a heat sink, and the work efficiency is excellent.
Specifically, a recess 53 is formed on one surface of a metal member 50 in which a brazing material 52 is clad on a core material 51, and a fin material 55 is fitted into the recess 53. Next, a metal layer 7, an Al—Si brazing foil (not shown), a ceramic substrate 2, an Al—Si brazing foil (not shown), and a metal layer 6 are sequentially laminated on the other surface, and this laminate is laminated in the thickness direction. Were simultaneously bonded by heating at 600 to 650 ° C. for about 1 hour in a vacuum while being pressurized at 0.5 × 10 ^{5 to} 5 × 10 ⁵ Pa.

  In the heat sink 5 described above, since the fin material 55 is formed of a material having a lower corrosion potential than the metal member 50, the material portion having the low corrosion potential that constitutes the fin material 55 is sacrificially corroded. Thus, the corrosion of the metal member 50 can be suppressed, and the fin material 55 is corroded before the metal member 50, thereby preventing pitting corrosion of the metal member 50, and the power module substrate 3 side of the coolant. Leakage can be prevented.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, the fin material may be provided on the entire surface of the metal part, but may be provided only on a portion disposed immediately below the metal member of the power module substrate.
Moreover, in the said embodiment, although the metal component was made into the clad material which bonded the brazing material on both surfaces of the core material, you may use the clad material which bonded the brazing material only to the single side | surface side in which a recessed part is formed. In this case, the metal member and the power module substrate may be joined via a brazing material foil.
Furthermore, the shape of the fin material is not limited to a pin shape (bar shape), and can correspond to a plate shape. In this case, as shown in FIG. 5, the fin material 70 is composed of a core material 71 (for example, aluminum of 3000 series alloy) made of the same material as the metal member 51 and a coating material 72 (for example, a corrosion potential lower than that of the core material 71). , 7000 series alloy aluminum) may be formed into a prismatic or plate shape, or only the tip of the fin material 80 is formed with a coating material 82 having a low corrosion potential, as shown in FIG. It is good also as a structure.

Further, the bonding between the ceramic substrate and the metal layer constituting the power module substrate is not limited to brazing but may be diffusion bonding or the like.
In the above embodiment, the power module substrate having the ceramic substrate and the heat sink are separately formed and then bonded together. However, the laminated body in which the metal layer is laminated on the ceramic substrate, and the heat dissipation thereof. It is good also as a structure which laminates | stacks the metal member which comprises a heat sink on a layer, and manufactures the board | substrate for power modules with a heat sink by heating once.
Moreover, in the said embodiment, although the board | substrate for power modules demonstrated as the structure by which the metal layer was laminated | stacked on both surfaces of the ceramic substrate, it was set as the structure which attaches a heat sink to the heat radiating layer of the metal layer, but provided the heat radiating layer. Alternatively, the back surface of the ceramic substrate and the heat sink may be directly joined.

DESCRIPTION OF SYMBOLS 1 Power module 2 Ceramic substrate 3 Power module substrate 4 Electronic component 5 Heat sink 6,7 Metal layer 8 Solder joint layer 9 Punch 50 Metal member 51,71 Core material 52 Brazing material 53 Concave part 54 Protrusion part 55,70,80 Fin material 56 Flux 57 Fillet 72,82 Covering material

Claims (3)

A power module substrate with a heat sink formed by bonding a heat sink and a power module substrate having a ceramic substrate,
The heat sink with the recess of the multiple is formed on the metal member, the periphery of the recess, the raised portion formed by raised surface of the metal member is formed so as to surround the recess, a portion in the recess The fin material fitted is brazed, and a fillet portion between the metal member and the fin material is formed including the raised portion,
A power module substrate with a heat sink, wherein a surface of the metal member opposite to the fin member is bonded to the power module substrate.   2. The power module substrate with a heat sink according to claim 1, wherein at least a part of a surface of the fin material is made of a material having a lower corrosion potential than the metal member.   A plurality of recesses in which the brazing material is disposed on the bottom surface is formed by pressing on a metal member having a brazing material bonded to the surface of the core material, and at the periphery of the recess by processing the recesses, A power module having a raised portion having a raised surface so as to surround the concave portion, and then partially fitting a fin material into the concave portion, and having a ceramic substrate on the surface of the metal member opposite to the fin material The metal member and the fin material are brazed to form a heat sink by heating while pressing in the thickness direction in a state where the substrate is laminated via the brazing material, and the metal member is used as the power module A method for manufacturing a power module substrate with a heat sink, characterized in that the substrate is bonded to a substrate.

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