JP2005191502A - Electronic part cooling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the cooling performance of an electronic cooling device, and secure contact property between a cooling block and a heat slinger, to improve reliability. <P>SOLUTION: In the electronic part cooling device, comprising the heat slinger 9 attached to a power module having an insulating substrate 8 on which a heat build-up electronic component is mounted and the cooling block 2 that forcibly cools the heat build-up device 7 by mounting the heat slinger 9, the heat slinger 9 is of plate-like copper as the base material, and is of a three-layered composite metal, where a platy Ni-Fe alloy is bonded to both sides of the base material; a salient is each formed on the mounting region of the insulating substrate 8, on which the heat build-up electronic part of the base material and on the backside opposite thereto; the regions that surround the salients on both surfaces are formed of the Ni-Fe alloy, the regions are fitted into the salients on both surfaces or the region that surrounds the mounting region of the insulating substrate 8 on which the heat build-up electronic component of the base material is mounted; and the regions on the backside opposite thereto are formed of the Ni-Fe alloy. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cooling device for cooling a heat-generating electronic component such as an inverter device.

In a hybrid vehicle, an inverter device is used to supply DC power from a battery to a traveling motor or the like.
The inverter device includes semiconductor switching elements such as transistors, FETs, or IGBTs. These elements control large currents, and therefore consume large power and generate a lot of heat.
If this heat generation is not escaped efficiently, the life of the parts will be shortened, and there is a risk of destruction, so a structure that can easily dissipate heat and suppress temperature rise is required.

2. Description of the Related Art Conventionally, there has been provided a so-called liquid cooling type cooling structure in which heat generated from the semiconductor switching element is forcibly cooled with a cooling liquid to suppress a temperature rise.
FIG. 1 is a perspective view showing an example of an inverter device employing such a conventional liquid cooling system.
The power module 1 is mounted on the mounting surface 3 of the cooling block 2 by applying silicon grease, and is screwed and fixed to the cooling block 2 through bolts 4 in the hole positions provided at the four corners of the power module 1. . Silicon grease is applied between the lower surface of the power module 1 and the cooling block mounting surface 3 to improve the adhesion between them and reduce the thermal resistance.
In addition, narrow pitch corrugated fins 5 formed of aluminum are inserted into the cooling block 2 and sealed from both side surfaces of the cooling block 2 with aluminum plates, and cooling liquid pipes 6a and 6b for circulating the cooling liquid. It is brazed together to ensure liquid-tightness.
FIG. 2 is a cross-sectional view of the inverter device of FIG.
The power module 1 is configured by soldering an insulating substrate 8 on which a semiconductor switching element 7 is mounted to a metal heat radiating plate 9 and attaching a housing 10 surrounding the element to the heat radiating plate 9.
The insulating substrate 8 is configured by providing a metal layer such as copper or aluminum on both surfaces of an insulating layer formed of an insulating material such as ceramics (for example, aluminum nitride or silicon nitride). An electrode is formed.
An external connection terminal 11 is formed integrally with the housing 10, and the semiconductor switching element 7 is bonded to the metal electrode of the insulating substrate 8 or the external connection terminal 11 with an aluminum wire 12.

When the semiconductor switching element incorporated in the power module is a large-capacity chip exceeding several tens of A, heat generation during energization becomes significant, and bonding is caused by the difference in thermal expansion coefficient between the semiconductor chip and the insulating substrate or the heat sink. Stress is generated at the interface, and there is a risk of breaking by cracks or the like.
Accordingly, the insulating substrate and the heat radiating plate are selected to have a thermal expansion coefficient substantially equal to or close to that of the semiconductor chip. For example, since the thermal expansion coefficient of silicon, which is a constituent material of the semiconductor chip, is 3 ppm / ° C., an AlN substrate having a thermal expansion coefficient of 5 ppm / ° C. is selected as the insulating substrate. Moreover, as a heat sink, an Al-SiC composite board, a Cu-Mo composite board, a carbon composite board, etc. with a thermal expansion coefficient of 7-8 ppm / degrees C can be used.

As another example of the electronic component cooling device, the cooling block is provided with an opening, and the power module heat sink is fitted and integrated, and the lower surface of the heat sink is formed by a cooling medium circulating in the cooling block. A structure in which is directly cooled is proposed.
As an example of the structure of the cooling device described above, an elastic body such as a rubber sheet, an O-ring, and packing is sandwiched between a heat sink having an opening, and a heat sink on which heat-generating electronic components are mounted is directly joined and fixed with screws. Structure cooling structures have been proposed (see, for example, Patent Documents 1 to 3).
JP-A-9-121557 JP-A-9-207583 JP 2001-203487 A

As another example of an electronic component cooling device, a structure in which an insulating substrate on which a heat-generating electronic component is mounted is directly mounted on a cooling block having a hollow structure and cooled (see, for example, Patent Document 4). .
JP 2001-77260 A

Furthermore, as another example of the electronic component cooling device, an opening is provided in the inverter case, and a heat sink on which a heat generating electronic component is mounted is fitted. A structure in which seams are joined and integrated by friction stir welding has been proposed (see, for example, Patent Document 5).
JP 2003-101277 A

As another example of the electronic component cooling apparatus, a composite metal in which plate-like copper is bonded to both surfaces of a plate-like Ni—Fe alloy may be used as a heat spreader material.
As a feature of this composite metal, copper having a thermal expansion coefficient of 17 ppm / ° C. is bonded to both surfaces of a Ni—Fe alloy having a very low thermal expansion coefficient of 2 ppm / ° C., thereby suppressing the thermal expansion coefficient of the composite metal to be small. At the same time, it is possible to diffuse heat in the surface direction.
Therefore, in applications where an insulating substrate on which a semiconductor chip is mounted is mounted on a heat sink, the difference between the thermal expansion coefficients of the heat sink and the insulating substrate can be set small, so there is no risk of cracking at the interface during the heat cycle. .
However, since copper with a very high thermal conductivity of 390 W / m · K is attached to both sides of a very small Ni—Fe alloy with a thermal conductivity of 15 W / m · K, Heat transfer is hindered and the thermal conductivity becomes very small.
As an example, in a copper- (Ni-Fe alloy) -copper composite metal, when the composition ratio of the three metals is set to 20% copper, Ni-Fe alloy 60%, and copper 20%, the thermal expansion coefficient is AlN. 7ppm / ° C, which is almost the same as the substrate, can be realized, but the heat conductivity in the plate surface parallel direction is 160W / m · K, the heat conductivity in the plate surface vertical direction is 20W / m · K, and the heat transfer coefficient in the vertical direction is extremely It will decline. Therefore, it is used as a heat spreader material for the purpose of diffusing transiently generated heat in the surface direction.

In the above electronic component cooling device, the insulating substrate on which the semiconductor switching element is mounted is soldered to a metal heat sink, and silicon grease is applied between the lower surface of the heat sink and the mounting surface of the cooling block. In the inverter device, the thermal conductivity of silicon grease is 1 W / m · K, which is two orders of magnitude smaller than that of a heat sink or an insulating substrate, and the thermal resistance at the silicon grease interface increases, so high heat dissipation performance cannot be expected.
Furthermore, as shown in FIG. 3, when the center part of the heat sink 9 is warped away from the cooling block mounting surface, the center part of the heat sink can be used as a cooling block even if the four corners of the power module are screwed. Since it does not adhere, heat is not transmitted to the cooling block 2 via the heat sink 9 and the temperature rises abnormally. Therefore, very high accuracy is required for the planar accuracy on the mounting surface of the heat sink and the cooling block in a state where the semiconductor switching element and the insulating substrate are mounted, which causes a labor and cost increase.

Furthermore, among the conventional cooling structures described above, an elastic body such as a rubber sheet, an O-ring, and packing is sandwiched between a heat sink having an opening, and a heat radiating plate mounted with heat-generating electronic components is joined and fixed with screws. In such a cooling structure, it is very important to maintain liquid tightness at the joint between the heat sink and the heat sink, and care must be taken not to cause leakage of the cooling liquid.
For example, in an Al—SiC composite plate and a Cu—Mo composite plate used as a heat sink, the thermal expansion coefficient is 7 to 8 ppm / ° C., whereas the metal material used as a heat sink having an opening is It is a low-cost and highly workable aluminum and has a very high thermal expansion coefficient of 24 ppm / ° C.
Assuming a power module mounted on a 30 to 50 kW class in-vehicle inverter device, the long side dimension of the power module base plate is about 20 cm. At the ambient temperature of −40 to + 85 ° C. required for inverter devices for in-vehicle use, it is necessary to cope with a temperature change of ΔT = 125 ° C., and heat sinks such as Al—SiC composite plates and Cu—Mo composite plates The power module has a dimensional change of 0.2 mm with respect to the long side dimension of 20 cm, whereas aluminum causes a dimensional change of 0.6 mm.
Therefore, a thermal expansion difference of 0.4 mm between the heat sink and the aluminum is generated, which gives stress to a rubber sheet or the like sandwiched between the heat sink and the heat sink.
Furthermore, in automotive applications where the temperature environment is severe, these stresses are applied as thermal history to the rubber sheet, O-ring, packing, and other elastic bodies that exist at the interface between the heat sink and the heat sink. There is also concern about the problem of deterioration.
In addition, among the conventional cooling structures described above, an opening is provided in the inverter case, and a heat sink on which heat-generating electronic components are mounted is fitted, and the joint between the projecting portion of the outer periphery of the heat sink and the inverter case Although a cooling structure that integrates and integrates friction stir welding has been proposed, it is necessary to perform friction stir welding after the inverter case and the heat sink fitting part are in close contact with each other without any gaps. This is required, resulting in increased processing time and cost.
Furthermore, friction stir welding is a method of joining materials by pressing a rotating tool against the joint and mixing the materials softened by frictional heat generated by the rotation with the rotating tool. A relatively large space is required to connect the inverter case, and high-difficult processing such as rotating the tool under certain conditions and softening and mixing the materials is necessary, ensuring a certain quality. difficult.
Moreover, when using a composite metal in which copper- (Ni-Fe alloy) -copper is joined as a heat sink, the use of an inverter device of several tens of kW class is large in the direction perpendicular to the plate surface of the heat sink during steady operation. Capacitive heat dissipation is required, and a copper- (Ni-Fe alloy) -copper composite metal having low thermal conductivity in the direction perpendicular to the plate surface is difficult to use.

The present invention solves the above problem, and a heat sink attached to a power module having an insulating substrate on which a heat-generating electronic component is mounted,
In an electronic component cooling device comprising a cooling block for forcibly cooling an exothermic electronic component by placing the heat sink,
The heat sink is a three-layer composite metal in which plate-like copper is used as a base material, and a plate-like Ni—Fe alloy is bonded to both surfaces of the base material,
Protruding portions are formed on the mounting region of the insulating substrate on which the heat-generating electronic components of the base material are mounted, and on the opposite back surface region,
An electronic component cooling apparatus characterized in that a region surrounding the convex portions on both sides is formed of a Ni-Fe alloy, and the region is fitted to the convex portions on both sides (FIG. 5).

A heat sink attached to a power module having an insulating substrate on which heat-generating electronic components are mounted;
In an electronic component cooling device comprising a cooling block for forcibly cooling an exothermic electronic component by placing the heat sink,
The heat sink is a three-layer composite metal in which a plate-like copper is used as a base material, and a plate-like Ni—Fe alloy is bonded to both surfaces of the base material,
An electronic component cooling device characterized in that a region surrounding an attachment region of an insulating substrate on which a heat-generating electronic component of the base material is mounted and a back surface region facing each other are formed of a Ni-Fe alloy (FIG. 10). ).

  Furthermore, the electronic component cooling device is characterized in that the shape of the region surrounded by the Ni—Fe alloy is substantially the same on both surfaces of the base material and has the same thickness.

  And the thermal expansion coefficient of the said heat sink is 3-8 ppm / degrees C, It is an electronic component cooling device characterized by the above-mentioned.

  The cooling block includes a cooling medium flow path, and has an opening joined to a region surrounding the Ni—Fe alloy of the heat radiating plate, and the heat radiating plate is joined to and integrated with the opening. A part of the surface of the electronic component is exposed in the flow path and directly cooled with a cooling medium (FIG. 12).

  Further, the radiator plate has fins on the back surface opposite to the mounting region of the insulating substrate on which the heat-generating electronic components are mounted, and the fins are integrated with the cooling block opening. The electronic component cooling device is characterized.

  And it is an electronic component cooling device characterized by brazing the joining of the cooling block and the heat sink.

  The electronic component cooling apparatus is characterized in that an O-ring or a flat packing is interposed between the cooling block and the heat radiating plate (FIG. 8).

  Further, the cooling block is made of copper as a base material, and a three-layer composite metal in which Ni—Fe alloy is bonded to both surfaces of the base material, or a Ni—Fe alloy as a base material, and copper is added to both surfaces of the base material It is an electronic component cooling device comprising three layers of joined composite metals.

  The electronic component cooling apparatus is characterized in that the Ni-Fe alloy is Invar (Ni 36%, Fe 64%) or 42 alloy (Ni 42%, Fe 58%).

  Moreover, it is an electronic component cooling device characterized by using a Kovar alloy (Ni-Co-Fe alloy) instead of the Ni-Fe alloy.

Furthermore, it is an electronic component cooling device using aluminum instead of the above copper.
By using the above-described configuration, it is possible to provide an electronic component cooling device that is reduced in cost and weight.

As described above, the heat sink is a three-layer composite metal having a plate-like copper or aluminum as a base material, and a plate-like Ni—Fe alloy or a Kovar alloy bonded to both surfaces of the base material. A mounting region of the insulating substrate on which the heat-generating electronic components of the material are mounted, a convex portion is formed on the opposite back surface, and a region surrounding the convex portion on both sides is formed of a Ni-Fe alloy or a Kovar alloy, The region is fitted to the convex portions on both sides, or the region surrounding the mounting region of the insulating substrate on which the heat-generating electronic component of the base material is mounted, and the opposite back surface is Ni-Fe alloy or Kovar. By forming it with an alloy, heat dissipation of large capacity is possible in the direction perpendicular to the plate surface of the heat sink using the characteristics of copper with high thermal conductivity, and the thermal expansion coefficient of the heat sink is the copper of the intermediate layer. Or Ni- e-alloy or Kovar-based alloy is bonded, so it can be suppressed to 3-8 ppm / ° C. and highly reliable electronic components without causing stress at the interface with the insulating substrate mounted on the heat sink A cooling device can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 is a perspective view of an electronic component cooling apparatus according to an embodiment of the present invention.
An insulating substrate 8 on which a semiconductor switching element 7 is mounted is mounted on a heat sink 9 and, like FIG. 1, a housing surrounding the semiconductor is attached to the heat sink and used as a power module mounted on a cooling block. The Here, in order to clarify the structure of the heat dissipation plate, the housing portion is omitted.
The insulating substrate 8 on which the semiconductor switching element 7 is mounted is mounted on the heat sink 9 by soldering.
Further, silicon grease is applied between the lower surface of the heat radiating plate 9 and the mounting surface 3 of the cooling block 2 to improve the adhesion between them, and the heat radiating plate 9 is screwed to the cooling block 2 with bolts 4. Fixed.
Then, a coolant such as coolant or pure water is supplied from one cold liquid pipe 6a of the cooling block 2 and circulated through the flow path in the cooling block, and then discharged from the other liquid cold pipe 6b. The heat generated in the semiconductor switching element 7 in the module is transmitted to the coolant flowing in the cooling block through the insulating substrate 8, the heat radiating plate 9, and silicon grease, and the power module is forcibly cooled.

Fig.5 (a) is a perspective view of the heat sink 9 used for the said electronic component cooling device, FIG.5 (b) is the sectional drawing. The heat sink 9 is composed of a composite metal in which three metals are joined in the order of Ni-Fe alloy, copper, and Ni-Fe alloy. On one surface of copper 13 of the intermediate layer, a Ni-Fe alloy 14 in which a mounting region of an insulating substrate on which a heat-generating electronic component is mounted is formed as a convex portion and a hole portion is formed to fit into the convex portion. Is inlaid and clad (described later).
As described above, as a means for producing a clad metal for fitting three metals, for example, a method in which three kinds of metals are joined by cold welding and then subjected to an annealing operation (quenching), or 3 Examples include a method of brazing and joining various types of metals, a thermocompression bonding method, and the like.

FIG. 6 is a diagram showing a molding process in which a plurality of metals are combined by cold pressure welding, and after three metal materials are cold pressure welded and joined by a roller 15, pressure welding is performed by annealing (quenching). Each metal can be fused and integrated between the metal interfaces.
In addition, when joining a plurality of metals by the brazing method, a phosphor copper brazing material is used as a brazing material, and the brazing material is placed in a state where it is sandwiched between the joining surfaces of copper and a Ni—Fe alloy, and then in a vacuum. By performing brazing by heating to 790 to 820 ° C., three kinds of metals can be joined.
Furthermore, when brazing is performed at a relatively low temperature, the copper 13 and the Ni—Fe alloy 14 are preliminarily plated with Ni, and then the Sn—Ag solder is sandwiched between the joint surfaces, and then in a vacuum. By heating to about 220 ° C and brazing, the Ni plating applied to the base material and Sn-Ag solder react to form Ni ₃ Sn ₄ on the joint surface, and the remelting temperature is 795 ° C. A composite metal plate set high can be manufactured.

The in-lay process is a technique for cladding a necessary material on a necessary portion of a base material that is a base material, and is an overlay that covers the entire surface of the base material that is the base material. It is different from processing.
In the inlay process, as shown in FIG. 5, a part of the base material as a base material is formed into a convex shape, and another material is clad around the convex portion. The material to be clad may be a material that has been punched out by press molding, or may be an individual material divided by the dotted line portion of the Ni-Fe alloy 14 in FIG. By inlaying with a material having a low coefficient of thermal expansion, a composite metal having high thermal conductivity can be realized while suppressing the coefficient of thermal expansion of the heat sink.
As an example, when a semiconductor chip having a thermal expansion coefficient of 3 ppm / ° C. is mounted on an insulating substrate having a thermal expansion coefficient of 5 ppm / ° C., the thermal expansion coefficient of the heat sink mounted by soldering the insulating substrate is about 7 ppm / It is preferable to set the temperature in the vicinity of ° C.
Here, when a composite metal obtained by joining three metals in the order of Ni—Fe alloy, copper, and Ni—Fe alloy is used as the heat sink, the thickness of the Ni—Fe alloy of the first layer is t1, the copper of the second layer is made of The thickness is t2, the thickness of the Ni—Fe alloy of the third layer is t3, the longitudinal elastic modulus of the Ni—Fe alloy is E1 (= E3), the thermal expansion coefficient is α1 (= α3), and the longitudinal elastic modulus of copper is E2. When the thermal expansion coefficient is α2, the thermal expansion coefficient α of the entire composite metal is expressed by the following equation (1).

It is represented by Here, when the Ni-Fe alloys of the first layer and the third layer are made of the same material and have the same thickness, E3 = E1, α3 = α1, t3 = t1 are substituted, and E3 and α3 are deleted. 2 is obtained.

As an example, when Invar (36Ni—Fe alloy) is used for the Ni—Fe alloy, α1 = 1.5 ppm / ° C., α2 = 17 ppm / ° C., E1 = 130 GPa, E2 = 119 GPa, and α = 7 ppm / ° C. T1 / t2 = 1.14 for determining the thickness of the Ni—Fe alloy and copper based on this numerical value.
However, since the Ni—Fe alloy is inlayed and the center part is hollow, the coefficient of thermal expansion will be slightly larger than 7 ppm / ° C., and the Ni—Fe alloy will be thicker than the above calculated value. It is necessary to adjust the thermal expansion coefficient by setting to.
In addition, when the shape of the two Ni-Fe alloys bonded to both sides of copper, which is the intermediate layer, is significantly different, there is a difference in the thermal expansion coefficient in the vicinity of the bonding interface. There is a concern to do. Therefore, it is desirable that the shapes and thicknesses of the two Ni—Fe alloys joined by inlaying on both sides of copper are substantially the same.

In the first embodiment, the structure in which the power module is screwed and fixed to the cooling block in a state where the silicone grease is applied to the cooling block mounting surface to improve the adhesion is shown. A structure in which the heat dissipation is further improved will be described.
FIG. 7 shows another embodiment of the present invention. An insulating substrate 8 on which a semiconductor switching element 7 is mounted is mounted on a heat sink 9. As in FIG. 1, a housing surrounding the semiconductor is usually attached to a heat sink and used as a power module. However, in order to clarify the structure of the heat sink, the housing portion is omitted.

As in FIG. 5, the heat sink 9 is clad by inlaying a Ni—Fe alloy on both surfaces of copper as an intermediate layer, and further has a structure in which the heat sink fins 5 are joined to the lower surface side of the heat sink 9. taking it. The radiating fin 5 is integrated by brazing a corrugated fin in the vicinity of the semiconductor switching element portion mounted on the radiating plate. The cooling block 2 includes a flow path for cooling liquid, and a U-shaped liquid passage having a concave cross section is formed so as to match the fin shape integrated with the heat sink.
And the fin side of the heat sink 9 of the power module is fitted to the U-shaped liquid passage side of the cooling block 2, and the peripheral portion 16 is brazed to form an integrated structure in which liquid tightness is ensured. Furthermore, by fixing the four corners of the heat radiating plate 9 with the cooling block 2 and the bolts 4, the reliability of liquid tightness is further improved.

The brazing of the radiating fins 5 to the heat radiating plate 9 and the brazing of the radiating plate 9 and the cooling block 2 may be performed by one time brazing or separately.
When performing brazing once, the heat sink 9 and the cooling block 2 are preliminarily plated with Ni and then superposed with Sn—Ag solder sandwiched between the joint surfaces, and the temperature is increased to about 220 ° C. in a vacuum. By heating and brazing, the Ni plating applied to the base material and Sn-Ag solder react to form Ni ₃ Sn ₄ on the joint surface, so that the remelting temperature is set to a very high value of 795 ° C. Can do.
Therefore, after that, when soldering and mounting the insulating substrate 8 on the heat sink 9 at 220 ° C., the fin joints of the heat sink and the solder at the joints of the heat sink and the cooling block are not melted again, and the bonding is maintained. Can be used in the state.
Moreover, when joining a heat sink and a heat sink and a heat sink and a cooling block in two steps, a phosphorous copper solder is put between the heat sink and the heat sink, and heated to 790 to 820 ° C. in a vacuum. After brazing the radiator plate and the radiator fins, the solder plate and the cooling block are overlapped with the Sn-Ag solder sandwiched between them and heated to about 220 ° C. in a vacuum to be brazed. It is possible to perform the bonding while maintaining the reliability without remelting the bonding surface. (Furthermore, when the three layers of the metal constituting the heat radiating plate 9 are joined by brazing, it can be carried out together with the brazing of the radiating fins 5.)

Further, as shown in FIG. 8, when the cooling block 2 and the heat sink 9 are fitted, an O-ring 17 or a flat packing is sandwiched between the peripheral portion 16, and the four corners of the heat sink 9 of the power module are formed using bolts 4. It is also possible to ensure liquid-tightness by screwing and fixing to the cooling block 2.
However, in this case, it is necessary to secure the reliability by making the screw tightening interval as short as possible and applying sufficient pressure to the O-ring or the flat packing.
Further, a coolant such as coolant or pure water is supplied from one cold liquid pipe 6a of the cooling block, circulated through the flow path in the cooling block, and then discharged from the other liquid cold pipe 6b. The heat generated in the semiconductor switching element 7 can be absorbed by the coolant flowing in the cooling block through the insulating substrate 8 and the heat radiating plate 9 to be exhausted.

In the electronic component cooling apparatus shown in FIGS. 7 and 8, only the insulating substrate and the fin-integrated heat sink are provided between the semiconductor switching element and the coolant, and the silicon grease of Example 1 does not exist. Furthermore, since the heat radiating plate and the cooling fin are integrated, the mounting surface portion of the cooling block existing between the heat radiating plate and the cooling fin in Example 1 is removed, and the thermal resistance therebetween is reduced. .
In particular, the effect of reducing the thermal resistance is greatly reduced by eliminating the application of silicon grease. For example, when 300 W of heat is radiated directly from a semiconductor switching element portion mounted on an insulating substrate having a length of 3 cm and a width of 3 cm, silicon ΔT due to thermal resistance in the grease portion can be reduced to about 16 ° C.
Furthermore, the slight heat sink of the heat sink does not reduce the adhesion between the heat sink and the cooling block mounting surface, and the heat dissipation capability can be stably exhibited.

When using copper with a smaller coefficient of thermal expansion than aluminum as a cooling block with a U-shaped liquid passage and using it for a small inverter of 10-20 kW class, the long side dimension of the power module heat sink should be within 10 cm. It will fit. Therefore, the difference in thermal expansion between the heat sink and the cooling block can be suppressed to 0.1 mm with respect to a temperature change of ΔT = 125 ° C. required for in-vehicle use, and the adhesion between the cooling block and the heat sink can be reduced. Without being reduced, it can be used stably over a long period of time.
However, for inverter applications exceeding 50 kW, the size of the heat sink and cooling block of the power module also increases, and stress is applied to the fitting part due to the difference in thermal expansion coefficient depending on the material used in the heat sink and cooling block. There is a risk of giving.
Therefore, as shown in the cross-sectional view of FIG. 9, a composite metal plate in which three metals of the same (Ni—Fe alloy) -copper- (Ni—Fe alloy) as the heat radiating plate are joined is used to form a concave cross section with a mold. After pressing, using a cooling block in which a U-shaped liquid passage is formed by brazing a threshold plate that forms a cooling liquid passage at the center, and the above-described composite metal plate with radiating fins is fitted here, The heat sink and the periphery of the cooling block are brazed or fixed in a liquid-tight manner with an O-ring and flat packing in between.
With the above configuration, the thermal expansion coefficients of the heat radiating plate and the cooling block fitting portion can be made substantially the same, and can be used stably for a long period of time in in-vehicle applications without causing stress at the interface.
As for the composite metal plate used for the cooling block, a composite metal plate having a coefficient of thermal expansion of about 7 ppm / ° C is used by joining three metal materials of copper- (Ni-Fe alloy) -copper. Even in such a case, the thermal expansion coefficients of the heat radiating plate and the cooling block fitting portion can be made the same, and it can be used stably without causing stress at the interface.

In Examples 1 and 2, as the power module heatsink, copper as an intermediate layer with convex portions on the insulating substrate mounting region on which the heat-generating electronic components are mounted and the opposite back surface region, The inlay process which joins the Ni-Fe alloy made into the fitting shape was performed, and the clad composite metal substrate was used.
However, another embodiment of the structure in which the cost required for the inlay treatment of the Ni—Fe alloy is reduced, the thickness of copper as the intermediate layer is further reduced, and the heat dissipation is improved by reducing the thermal resistance is as follows. Explained.

In the heat radiation plate shown in FIG. 10, the Ni-Fe alloy 14 clad on both sides of the copper 13 as an intermediate layer is punched in advance by pressing the mounting region portion of the insulating substrate on which heat-generating electronic components are mounted. Processing.
The intermediate layer copper 13 uses a flat plate material. The copper plate 13 that is the intermediate layer and the upper and lower Ni—Fe alloys 14 are welded together by performing an annealing operation after three metal materials are joined by cold pressure welding in the same manner as in the heat dissipation plate of Example 1. Each metal is fused between the metal interfaces, or three metal materials are brazed and integrated.
As a result, the both sides of the heat radiating plate have a cavity (concave) structure in which the copper plate is exposed with a step corresponding to the mounting region of the insulating substrate.

FIG. 11 is a perspective view of an electronic component cooling device configured using the heat sink shown in FIG. 10, and FIG. 12 is a cross-sectional view thereof.
A corrugated fin is brazed and integrated with the lower surface side cavity of the heat sink 9 in advance.
An insulating substrate 8 on which the semiconductor switching element 7 is mounted is soldered and mounted on the cavity portion on the upper surface side of the heat sink 9.
The cooling block 2 is provided with a cooling liquid flow path, and is formed with a U-shaped liquid passage having a concave cross section so as to coincide with the fin shape integrated with the heat radiating plate 9. It is configured to form a liquid passage for the coolant flow path by fitting with the fin side and brazing the peripheral portion 17 or by liquid tight integration with an O-ring and a flat packing interposed therebetween.
About the thickness of each layer at the time of clad | ingling the Ni-Fe alloy of the both sides of the copper plate which is an intermediate | middle layer, it can calculate using Formula 2 similarly to Example 1,2.
However, since the central part of the Ni—Fe alloy to be clad is in the hollowed out state, the thermal expansion coefficient will be slightly larger than 7 ppm / ° C., and the Ni—Fe alloy is set to be thicker than the above calculated value. It is necessary to adjust the thermal expansion coefficient.
Further, brazing of the heat radiating plate 9, the heat radiating fins 5, and the cooling block 2 can be performed by the same method as in the second embodiment.
In Example 2 shown in FIG. 7, the thickness of the copper including the thickness of the layer to which the Ni—Fe alloy is inlayed is necessary, but in the example of FIG. 12, the Ni—Fe alloy is clad. No copper thickness is required for the layer thickness.
Therefore, as compared with Examples 1 and 2, it is possible to reduce the thermal resistance by the thickness of the copper plate.

In FIG. 10, the Ni—Fe alloy bonded to both surfaces of copper, which is the intermediate layer of the power module heat sink, is stamped by press molding all the mounting region portions of three insulating substrates. However, it is desirable that the Ni—Fe alloy joined from both sides of the copper be joined with the area to be punched out and cut as small as possible in order to suppress the thermal expansion of the intermediate layer copper.
Therefore, by optimizing the wiring pattern on the upper surface side of the insulating substrate and setting the insulating substrate on which the semiconductor switching element is mounted as small as possible, a more reliable electronic component cooling device can be provided.
FIG. 13 shows a case where the semiconductor switching elements 7 corresponding to the upper, lower, and U arms of the three-phase inverter are mounted on six insulating substrates.
In FIG. 13, the Ni—Fe alloy joined from both sides of copper is stamped by stamping all six locations. On the upper surface side of the heat sink 9, the insulating substrate 8 on which the semiconductor switching element 7 shown in FIG. 14 is mounted is soldered and mounted on six cavity (concave) portions. Further, small-shaped radiating fins 5 shown in FIG. 15 are brazed to the lower surface side cavity portion of the radiating plate 9.
As shown in FIG. 16, the cooling block 2 is provided with a coolant flow path, and a U-shaped liquid passage having a concave cross section is formed so as to match the fin shape integrated with the heat sink 9. It is fitted to the fin side of the heat radiating plate 9, and the peripheral portion 17 is brazed, or the liquid is integrated liquid-tightly with an O-ring and a flat packing in between. The structure forms a path.
Therefore, compared with Examples 1-3, since the punching part of the Ni-Fe alloy joined from both sides of copper is set small, the thermal expansion of copper in the intermediate layer can be suppressed more stably. And the reliability can be further improved.

In the electronic component cooling apparatus shown in FIGS. 7 to 9, 11, 12, and 16, a metal plate is pressed into a concave cross section with a die, and then a U-shaped brazing plate is formed by brazing a threshold plate that forms a cooling liquid path at the center. Although the cooling block in which the liquid passage is formed is used, as shown in FIG. 17, a hollow port is provided in the cooling liquid circulation path of the inverter housing 18 and is fitted to the fin side of the heat sink 9, so that the peripheral portion 16 A structure in which a liquid path for a coolant flow path is formed by screw-tightening with an O-ring 17 or a flat packing interposed therebetween and being liquid-tightly integrated is also possible.
When the size of the inverter housing is large, the heat capacity of the housing is large, the power required for brazing increases, and the amount that can be processed at once in the furnace decreases, so the mass productivity is reduced. The O-ring or flat packing is more practical.

As the Ni-Fe alloy, invar (Ni 36%, Fe 64%) or 42 alloy (Ni 42%, Fe 58%) is a typical metal material. For example, 42 alloy is used as a semiconductor lead frame and has a large distribution volume, so it is inexpensive and easily available.
Therefore, since it is not a noble metal like the molybdenum conventionally used for the Cu-Mo composite board, a heat sink can be manufactured at an inexpensive material cost. Both Invar and 42 alloy have a thermal expansion coefficient as small as 1.5 to 5 ppm / ° C., and are optimal as Ni—Fe alloys to be joined from both sides of copper.

  Moreover, it can replace with a Ni-Fe alloy and can also use a Kovar-type alloy (Ni-Co-Fe-type alloy). Kovar-based alloys are mainly composed of Ni, Co, and Fe, and their thermal expansion coefficient is about 4.5 ppm / ° C, which is the same or slightly larger than Invar and 42 alloy, but the temperature range where low thermal expansion can be obtained is extremely high. It has features that can be taken widely.

Furthermore, aluminum can be used instead of copper clad on the heat sink. Aluminum has a large coefficient of thermal expansion of 24 ppm / ° C compared to copper, but its elastic modulus is small, so it absorbs and relaxes the stress acting between the Ni-Fe alloys joined from both sides and improves heat cycle resistance. It is a rich material.
Moreover, since it is lightweight and low-cost compared with copper, and it is excellent in workability, it can be used effectively.

Further, values that can be set as the thermal expansion coefficient of the heat sink are 3 ppm / ° C. which is the same thermal expansion coefficient as that of the semiconductor chip on the side where the thermal expansion coefficient is small, and Cu—Mo on the side where the thermal expansion coefficient is large. A composite plate of 7 ppm / ° C. and an Al—SiC composite plate of 8 ppm / ° C. (for in-vehicle use requiring use in a wide temperature range of −40 to + 85 ° C.) are required. Therefore, the thermal expansion coefficient of the heat sink is preferably 3 to 8 ppm / ° C.
Further, a ceramic substrate (aluminum nitride or silicon nitride) that is provided with a metal layer such as copper or aluminum on both surfaces thereof can be used.
And, an insulating substrate with a heat sink directly formed with an insulating layer of aluminum nitride or silicon nitride by sputtering, plasma spraying, etc. can be used, and a semiconductor switching element is mounted by forming a wiring pattern on it You can also

It is a perspective view of the conventional electronic component cooling device. It is sectional drawing of the electronic component cooling device of FIG. It is a figure for demonstrating one of the problems of a conventional structure. 1 is a perspective view of an electronic component cooling device according to an embodiment of the present invention. It is a figure which shows the structure of the heat sink of FIG. 4, (a) is a perspective view, (b) is sectional drawing. It is a figure which shows the assembly process of a heat sink. It is a perspective view of an electronic component cooling device according to another embodiment of the present invention. It is a perspective view of an electronic component cooling device according to another embodiment of the present invention. It is sectional drawing of the electronic component cooling device by other Examples of this invention. It is a figure which shows the other structure of a heat sink, (a) is a perspective view, (b) is sectional drawing. It is a perspective view of the electronic component cooling device using the heat sink of FIG. It is sectional drawing of the electronic component cooling structure of FIG. It is a perspective view which shows the other structure of a heat sink. It is a perspective view of the state which mounted the insulating substrate in the heat sink of FIG. It is a perspective view from the bottom face side of the state which mounted the radiation fin on the heat sink of FIG. It is a perspective view of the electronic component cooling device using the heat sink of FIG. It is sectional drawing of the electronic component cooling device by other Examples of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power module 2 Cooling block 3 Cooling block mounting surface 4 Bolt 5 Radiation fins 6a and 6b Cold liquid pipe 7 Semiconductor switching element 8 Insulating substrate 9 Heat sink 10 Housing 11 External connection terminal 12 Aluminum wire 13 Copper plate 14 Ni-Fe alloy plate 15 Roller 16 Cooling block peripheral part 17 O-ring 18 Inverter housing

Claims (12)

A heat sink attached to a power module having an insulating substrate on which heat-generating electronic components are mounted;
In an electronic component cooling device comprising a cooling block for forcibly cooling an exothermic electronic component by placing the heat sink,
The heat sink is a three-layer composite metal in which a plate-like copper is used as a base material, and a plate-like Ni—Fe alloy is bonded to both surfaces of the base material,
Protruding portions are formed on the mounting region of the insulating substrate on which the heat-generating electronic components of the base material are mounted, and on the opposite back surface region,
An electronic component cooling apparatus characterized in that a region surrounding the convex portions on both sides is formed of a Ni-Fe alloy, and the region is fitted to the convex portions on both sides. A heat sink attached to a power module having an insulating substrate on which heat-generating electronic components are mounted;
In an electronic component cooling device comprising a cooling block for forcibly cooling an exothermic electronic component by placing the heat sink,
The heat sink is a three-layer composite metal in which a plate-like copper is used as a base material, and a plate-like Ni—Fe alloy is bonded to both surfaces of the base material,
An electronic component cooling apparatus characterized in that a region surrounding an attachment region of an insulating substrate on which a heat-generating electronic component of the base material is mounted and a back region opposite to each other are formed of a Ni-Fe alloy.   3. The electronic component cooling apparatus according to claim 1, wherein the shape of the region surrounded by the Ni—Fe alloy according to claim 1 or 2 is substantially the same and has the same thickness on both surfaces of the substrate.   The electronic component cooling apparatus according to claim 1 or 2, wherein the heat dissipation coefficient of the heat radiating plate according to claim 1 or 3 is 3 to 8 ppm / ° C.   The cooling block according to claim 1 or 2, comprising a cooling medium flow path, and having an opening joined to a back surface opposite to an attachment region of the insulating substrate on which the electronic component is mounted. An electronic component cooling device characterized in that a heat sink is joined and integrated, a part of the surface of the heat sink is exposed in the flow path, and is directly cooled by a cooling medium.   The heat sink according to claim 5 has fins on the back surface opposite to the mounting area of the insulating substrate on which the heat-generating electronic components are mounted, and the fins are integrated with the openings of the cooling block. An electronic component cooling device.   An electronic component cooling apparatus characterized in that the cooling block according to claim 1 or 2 and the heat sink are brazed.   An electronic component cooling apparatus comprising an O-ring or a flat packing interposed between the cooling block according to claim 1 and the heat sink.   The cooling block according to claim 1 or 2, wherein the base material is a three-layer composite metal having a base material of copper and a Ni-Fe alloy bonded to both sides of the base material, or a base material of a Ni-Fe alloy. An electronic component cooling device comprising a three-layer composite metal in which copper is bonded to both surfaces of a material.   10. The electronic component cooling apparatus according to claim 1, wherein the Ni-Fe alloy is Invar (Ni 36%, Fe 64%) or 42 alloy (Ni 42%, Fe 58%).   An electronic component cooling apparatus using a Kovar-based alloy (Ni-Co-Fe-based alloy) instead of the Ni-Fe alloy according to claim 1, 2, or 9.   An electronic component cooling apparatus using aluminum instead of the copper according to claim 1, claim 2, or claim 9.

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