Double-sided cooling power module

Abstract

The present invention is a double-sided cooling power module comprising: a semiconductor element; and two insulating circuit boards that sandwich the semiconductor element, in which each of the two insulating circuit boards has: an insulating resin film; a circuit part provided on the semiconductor element side of the resin film; and a heat dissipation part provided on the opposite side of the resin film from the semiconductor element, the circuit part having: a wiring layer comprising a copper-containing metal provided on the surface of the resin film; and a protruding portion that protrudes from the wiring layer toward the semiconductor element and supports the semiconductor element, the heat dissipation portion having a copper-containing metal layer provided on the surface of the resin film. Thus, provided is a double-sided cooling power module in which damage such as cracking in a high-temperature environment can be suppressed, surface flatness can be easily controlled, structural problems such as molding voids can be suppressed, and reliability is high even at high temperatures.

Description

Technical Field

[0001] The present invention relates to a double-sided cooling power module. Background Art

[0002] In recent years, as semiconductor elements for power semiconductor modules (also simply referred to as "power modules"), semiconductor elements using wide bandgap semiconductors such as silicon carbide (SiC) and gallium nitride (GaN) (hereinafter, sometimes also referred to as "wide bandgap semiconductor elements") have attracted attention. Compared with existing semiconductor elements using silicon, wide bandgap semiconductor elements can operate in a high-temperature environment and have excellent characteristics such as low loss and high-speed operation. By using such wide bandgap semiconductor elements, it is possible to miniaturize and enhance the performance of power modules.

[0003] However, power modules generally have heat dissipation components such as heat sinks. Through this heat dissipation component, the heat generated in the semiconductor element is dissipated to the outside, and the operation of the power semiconductor module is stabilized.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: US Patent No. 9,390,996 Specification

[0007] Patent Document 2: US Patent Application Publication No. 2019 / 0341332 Specification

[0008] Patent Document 3: Chinese Patent No. 10,992,0785 Specification

[0009] Patent Document 4: US Patent No. 10,002,821 Specification Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] There have been proposed double-sided cooling (DSC: Dual side cooling) power modules (such as Patent Documents 1-4, etc.) for efficiently dissipating heat from the upper and lower main surfaces of a semiconductor device on which semiconductor elements are mounted. Figure 3 An example of a conventional double-sided cooling power module described in Patent Document 2 is shown. As Figure 3As shown, in the existing double-sided cooling power module 200, a semiconductor element 1 is held by insulating circuit boards 30A and 30B (sometimes also referred to as DBC: Direct Bonding Cupper) obtained by bonding conductors 32A, 33A, 32B, and 33B such as copper (Cu) foils to both sides of ceramic insulating substrates 31A and 31B. In addition, since the semiconductor element 1 is very thin (small), spacers 34 are used to adjust the installation position. The molding resin 18 is resin-sealed in the space, and in addition, a lead frame 17 serving as an external terminal is appropriately provided. In addition, on the surface of the insulating circuit boards 30A and 30B on the side where the semiconductor element 1 is mounted, a part of the conductor is removed by etching.

[0012] In the existing double-sided cooling using ceramic insulating substrates, a high cracking rate caused by the difference in the coefficient of thermal expansion (CTE) at high temperatures has become a problem. In addition, it is difficult to control the flatness of the surface due to the cumulative tolerance of the laminated material caused by the thickness change during curing at high temperatures. And molding voids are generated in the space between the patterns of conductors such as copper (Cu) foils, and there are also structural problems.

[0013] The present invention has been completed to solve the above problems, and its object is to provide a double-sided cooling power module with high reliability even at high temperatures.

[0014] Means for Solving the Problem

[0015] The present invention has been completed to achieve the above object, and provides a double-sided cooling power module having: a semiconductor element; and two insulating circuit boards that hold the semiconductor element, wherein each of the two insulating circuit boards has: an insulating resin film; a circuit portion provided on the semiconductor element side of the resin film; and a heat dissipation portion provided on the side of the resin film opposite to the semiconductor element, the circuit portion having: a wiring layer made of a copper-containing metal provided on the surface of the resin film; and a convex portion made of a copper-containing metal that projects from the wiring layer toward the semiconductor element side to support the semiconductor element, and the heat dissipation portion having a copper-containing metal layer provided on the surface of the resin film.

[0016] According to such a double-sided cooling power module, breakage such as cracking in a high-temperature environment can be suppressed, the flatness of the surface can be easily controlled, and structural problems such as molding voids can also be suppressed, and the reliability is high even at high temperatures.

[0017] At this time, it may be that the copper-containing metal of the wiring layer and the copper-containing metal of the convex portion in the circuit portion are made of different materials.

[0018] Therefore, it can be considered that by making the coefficient of thermal expansion of the wiring layer different from that of the convex portion, higher reliability can be achieved even at high temperatures.

[0019] At this time, it can be considered that the insulating circuit board has a filling material including a molding resin, a solder resist, a resin filler, or a glass epoxy resin on the wiring layer where the convex portion is not provided in the circuit portion. This is achieved by filling, coating, etc. of the filling material to fill the wiring layer where the convex portion is not provided, and making the upper end surface of the convex portion exposed.

[0020] As a result, the reliability at high temperatures becomes higher.

[0021] At this time, it can be considered that the insulating circuit board has a window portion around the convex portion of the circuit portion. The window portion penetrates the wiring layer to the surface of the resin film, and the window portion has a filling material.

[0022] As a result, improvement in mold flow and track void can be achieved.

[0023] At this time, it can be considered that the thickness of the resin film of the insulating circuit board is set to 40 μm or more and less than 160 μm.

[0024] As a result, the heat dissipation characteristics are more excellent.

[0025] Advantages of the Invention

[0026] As described above, according to the double-sided cooling power module of the present invention, breakage such as cracking in a high-temperature environment can be suppressed, the flatness of the surface can be easily controlled, and structural problems such as molding voids can also be suppressed. Even at high temperatures, the reliability is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a diagram (cross-section) showing an example of the double-sided cooling power module of the present invention.

[0028] Figure 2 It shows in Figure 1 A diagram (cross-section) in which the upper insulating circuit board 10A is omitted, and a top view of the lower insulating circuit board 10B in a state where resin filling is not performed and semiconductor elements are not mounted.

[0029] Figure 3 It is a diagram (cross-section) showing an example of a conventional double-sided cooling power module.

[0030] Figure 4 It is a diagram showing the results obtained by evaluating and comparing the heat dissipation effects of a conventional double-sided cooling power module using a ceramic substrate and the double-sided cooling power module of the present invention through simulation.

[0031] Figure 5 is a diagram showing an evaluation and comparison of the dimensions (particularly thickness) of an existing double-sided cooling power module using a ceramic substrate and the double-sided cooling power module of the present invention.

[0032] Figure 6 is a diagram showing a comparison of the assembly processes (schematic) of an existing double-sided cooling power module using a ceramic substrate and the double-sided cooling power module of the present invention.

[0033] Figure 7 is a diagram showing the simulation results for thermal characteristics.

[0034] Figure 8 is a diagram showing a comparison between the double-sided cooling power module of the present invention and the prior art. DETAILED DESCRIPTION

[0035] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0036] As described above, there is a need for a double-sided cooling power module with high reliability even at high temperatures.

[0037] The inventors of the present invention have repeatedly conducted in-depth studies on the above problems, and as a result, it has been found that by a double-sided cooling power module, it is possible to suppress breakages such as cracking in a high-temperature environment, easily control the flatness of the surface, and also suppress structural problems such as molding voids, and the reliability is high even at high temperatures, thus completing the present invention. The double-sided cooling power module has: a semiconductor element; and two insulating circuit boards that sandwich the semiconductor element, wherein each of the two insulating circuit boards has: an insulating resin film; a circuit portion provided on the semiconductor element side of the resin film; and a heat dissipation portion provided on the side of the resin film opposite to the semiconductor element. The circuit portion has: a wiring layer made of a copper-containing metal provided on the surface of the resin film; and a convex portion made of a copper-containing metal that protrudes from the wiring layer toward the semiconductor element side to support the semiconductor element. The heat dissipation portion has a copper-containing metal layer provided on the surface of the resin film.

[0038] Hereinafter, an explanation will be given with reference to the drawings.

[0039] [Double-sided Cooling Power Module]

[0040] First, with reference to the attached Figure 1 , the double-sided cooling power module of the present invention will be described. As Figure 1As shown, the double-sided cooling power module 100 of the present invention has: a semiconductor element 1; and two insulating circuit boards 10A and 10B that sandwich the semiconductor element 1. Each of the two insulating circuit boards 10A and 10B has: insulating resin films 11A and 11B; circuit portions 12A and 12B provided on the semiconductor element side of the resin films 11A and 11B; and heat dissipation portions 13A and 13B provided on the side of the resin films 11A and 11B opposite to the semiconductor element. Each of the circuit portions 12A and 12B has: wiring layers 14A and 14B made of a copper-containing metal provided on the surface of the resin film; and convex portions 15A and 15B made of a copper-containing metal that project from the wiring layers 14A and 14B toward the semiconductor element 1 side to support the semiconductor element 1. The heat dissipation portions 13A and 13B have copper-containing metal layers 16A and 16B provided on the surface of the resin film. In addition, lead terminals 17 for external electrical connection and a molding resin 18 for resin-sealing the space are appropriately provided.

[0041] (Insulating Circuit Board)

[0042] Next, the details of the insulating circuit board will be described. The two insulating circuit boards 10A and 10B sandwich the semiconductor element 1. Each insulating circuit board has: resin films 11A and 11B; circuit portions 12A and 12B provided on the semiconductor element side of the resin film; and heat dissipation portions 13A and 13B provided on the side of the resin film opposite to the semiconductor element.

[0043] The resin film of the present invention is not particularly limited as long as it is an insulating material, and for example, PET (polyethylene terephthalate), polyimide, polycarbonate, polyacrylate, etc. can be used. In order to improve the high-temperature characteristics, as the film, a film preferably mixed with fillers such as silica, alumina, and zirconia is used. The film can interfere with stress more effectively than ceramics.

[0044] Both the wiring layers 14A and 14B and the convex portions 15A and 15B are made of a copper-containing metal, and they can be the same, but different materials are preferred. If they are different materials, the coefficient of thermal expansion of the wiring layer and the convex portion can be made different, and even at high temperatures, higher reliability can be achieved. For example, the copper-containing metal of the wiring layer can be set to high-purity copper (OFC), and the copper-containing metal of the convex portion can be set to a copper alloy. Examples of the copper alloy include C194, C7025, EFTEC 64T, Alloy 42, etc.

[0045] On the wiring layers 14A and 14B of the circuit parts 12A and 12B where the convex parts 15A and 15B are not provided, it is preferable to have the filling materials 20A and 20B containing molding resin, solder resist, resin filler, or glass epoxy resin. Thereby, the reliability at high temperatures becomes higher.

[0046] In addition, window parts 19A and 19B can be provided around the convex parts 15A and 15B of the circuit parts 12A and 12B. The window parts 19A and 19B penetrate the wiring layers 14A and 14B to the surfaces of the resin films 11A and 11B, and the filling materials 20A and 20B are provided in the window parts 19A and 19B. Thereby, improvement of the mold flow and the track void can be achieved.

[0047] The heat dissipation parts 13A and 13B have copper-containing metal layers 16A and 16B. The wiring layers 14A and 14B, the convex parts 15A and 15B of the circuit parts 12A and 12B, and the copper-containing metal layers 16A and 16B of the heat dissipation parts 13A and 13B are all layers made of copper-containing metal, but the compositions, forms, etc. of these metals can be the same or different.

[0048] In addition, Figure 1 it is described that the structures of the two insulating circuit boards 10A and 10B are symmetric structures, but the patterns of the circuit parts, the wiring layers, the convex parts, and the metal compositions of the copper-containing metal layers of the heat dissipation parts of the two insulating circuit boards can be the same or different.

[0049] Figure 2 It shows a diagram (cross-section) of omitting the upper insulating circuit board 10A in Figure 1 , and a top view of the lower insulating circuit board 10B in a state where resin filling is not performed and semiconductor elements are not mounted. In Figure 2 , in the left figure, for the sake of explanation, the upper insulating circuit board in the double-sided cooling power module is not described. Figure 2 The right figure of Figure 2 is a top view of the lower insulating circuit board observed from above in a state where the semiconductor element 1 is not mounted and the filling material 20B is not filled in the left figure. As

[0050] shown, it is preferable to provide a window part 19B around the convex part 15B. The window part 19B penetrates the wiring layer 14B to the surface of the resin film 11B. In addition, the formation of the convex part and the window part can be performed by etching the copper-containing metal layer. Moreover, when the etched area is filled with an adhesive or a resin material, the influence of the difference in the thermal expansion coefficient of the copper-containing metal layer can be reduced. The mismatch in the thermal expansion coefficient between the convex part and the semiconductor element is reduced, and the crack of the semiconductor element is improved. In addition, by filling an adhesive or a resin material (filling material) between the convex parts 15B and in the window parts 19B and having the filling material in the window parts, improvement of the mold flow and the track void can be achieved.

[0050] AsFigure 2 There are no particular limitations on the arrangement and shape of the wiring layer 14B, convex portion 15B, and window portion 19B made of copper-containing metal provided on the surface of the resin film in the circuit portion shown in the left figure.

[0051] The adhesive and resin material (filling material) may contain fillers such as Al 2 O 3 , BN, AIN, etc., molding resin, photosensitive solder resist (PSR), resin filler, or flame retardant type 4 (FR4), solder mask, mold compound, epoxy resin, etc. It is particularly preferred to contain molding resin, photosensitive solder resist, resin filler, or flame retardant type 4.

[0052] (Semiconductor element)

[0053] The semiconductor element 1 mounted on the double-sided cooling power module of the present invention is not particularly limited as long as it is a power semiconductor element. For example, a wide-bandgap semiconductor element can be used, and such a wide-bandgap semiconductor element uses a wide-bandgap semiconductor such as silicon carbide (SiC) or gallium nitride (GaN). Such a semiconductor element is provided on the convex portion of the circuit portion via an adhesive layer 21 such as solder paste or Ag paste.

[0054] As described above, as the insulating circuit board, an insulating resin film is used instead of the existing ceramic substrate and spacer, whereby the high-temperature reliability is improved, and in addition, the operation becomes easier. In particular, the generation of cracks at high temperatures, which is a problem in the existing ceramic substrate, can be suppressed. And since there is no need to use a spacer when mounting the semiconductor element, the cumulative tolerance of the materials becomes smaller, so the flatness management is excellent compared with the existing double-sided cooling module. Moreover, the material cost can be reduced and the assembly process can be simplified.

[0055] Next, the heat dissipation effect and evaluation results of the double-sided cooling power module of the present invention will be described. Figure 4 It is a diagram showing the results obtained by evaluating and comparing the heat dissipation effects of an existing double-sided cooling power module using a ceramic substrate and the double-sided cooling power module of the present invention through simulation. In this evaluation, for the existing double-sided cooling power module using a ceramic substrate and the double-sided cooling power module of the present invention using a resin film, a water-cooling jacket is installed for cooling, and the temperature characteristics when it becomes a high-temperature state are simulated and compared. In Figure 4 In the attached drawing showing the simulation results of the temperature distribution, the temperature levels near the center of the upper about 1 / 3 area are compared by the shade of color. As Figure 4As shown, it can be seen that the temperature rise of the double-sided cooling power module of the present invention is suppressed to a relatively low level (lighter color), and the heat dissipation effect is high.

[0056] The double-sided cooling power module of the present invention does not use a spacer when mounting semiconductor elements as in the case of using an existing ceramic substrate. Therefore, in the double-sided cooling power module of the present invention, the semiconductor element is directly mounted on the insulating circuit board, and the heat dissipation effect is higher compared to the case of using a spacer. In this way, the thermal cycle reliability is higher when using a resin film compared to when using a ceramic substrate.

[0057] In addition, in an existing double-sided cooling power module, it is impossible to make the thickness of the layer made of a copper-containing metal in the circuit part and the heat dissipation part thicker than the thickness of the ceramic substrate. The reason is that when the thickness of the layer made of a copper-containing metal is thicker than the thickness of the ceramic, cracks in the ceramic are likely to occur. On the other hand, the resin film can make the thickness of the layer made of a copper-containing metal in the circuit part and the heat dissipation part thicker. Thereby, heat dissipation can be further promoted, the power can be increased, and the generation of cracks can be more effectively suppressed.

[0058] Figure 5 It is a diagram showing an evaluation and comparison of the dimensions (especially thickness) of an existing double-sided cooling power module using a ceramic substrate and the double-sided cooling power module of the present invention. The evaluation was carried out on the premise that the components common to both, such as semiconductor elements (Die: bare chips), are equivalent components. Since each layer has manufacturing tolerances, as the number of layers increases, the overall thickness becomes larger and the cumulative tolerance also increases. As Figure 5 shown, in the existing double-sided cooling power module, the deviation of the overall thickness of the package occurs in the range of about 0.24 to 0.26 mm. When such a deviation occurs in the part of multiple semiconductor elements, the overall thickness of the power module also deviates, and the flatness deteriorates. In contrast, in the double-sided cooling power module of the present invention, the overall thickness of the package is about 0.22 mm. From this, it can be seen that in the double-sided cooling power module of the present invention, since the number of materials to be managed is smaller, the dimensional accuracy is improved, and the management of the overall thickness and flatness becomes easier. As a result, no gap can be formed between the power module and a radiator such as a water jacket, the contact property is improved, and an improvement in thermal performance can be expected.

[0059] Figure 6This is a diagram showing a comparison (schematic) of the assembly processes of an existing double-sided cooling power module using a ceramic substrate and the double-sided cooling power module of the present invention. In the assembly process of the double-sided cooling power module of the present invention, the process of mounting semiconductor elements on the spacer can be omitted. Therefore, compared with the existing method, the assembly process can be simplified. Moreover, by reducing the cost associated with the usage amount of the spacer and adhesives (such as solder, epoxy resin, silver paste, etc.) and simplifying the process, the UPH (Unit Per Hour: the total number of mounted components that can be executed per hour) can be increased.

[0060] Next, the results of the simulation for thermal characteristics will be described. Figure 7 This is a diagram showing the simulation results for thermal characteristics. The junction temperature when using a ceramic substrate (existing example) is set as the reference value, and the film thickness of the resin film is set as a parameter in the simulation. Figure 7 It can be seen that when the film thickness of the resin film is set in the range less than 160 μm to exhibit better performance at high temperatures, the heat dissipation characteristics are more excellent and more stable, and the junction temperature can be reduced compared with the past. In addition, from the viewpoints of the size of the filler contained in the film, the strength of the film, and the stability in order to improve the high-temperature characteristics, the film thickness of the resin film is preferably set to 40 μm or more.

[0061] The advantages of the double-sided cooling power module of the present invention described above are compared with the prior art and summarized as Figure 8 . Figure 8 The "Type #1" of Figure 3 is an existing double-sided cooling power module described using Figure 8 and is described in, for example, Patent Document 2.

[0062] In addition, the present invention is not limited to the above-described embodiments. The above-described embodiments are merely illustrative, and technical solutions having substantially the same structure as the technical concept described in the claims of the present invention and exhibiting the same effects are all included in the technical scope of the present invention.

Claims

1. A double-sided cooling power module having: a semiconductor element; and two insulating circuit boards that sandwich the semiconductor element, Characterized in that, Each of the two insulating circuit boards has: an insulating resin film; a circuit portion provided on the semiconductor element side of the resin film; and a heat dissipation portion provided on the side of the resin film opposite to the semiconductor element, The circuit portion has: a wiring layer made of a copper-containing metal provided on the surface of the resin film; and a convex portion made of a copper-containing metal that projects from the wiring layer toward the semiconductor element side to support the semiconductor element, The heat dissipation portion has a copper-containing metal layer provided on the surface of the resin film.

2. The double-sided cooling power module according to claim 1, Characterized in that, The copper-containing metal of the wiring layer and the copper-containing metal of the convex portion in the circuit portion are made of different materials.

3. The double-sided cooling power module according to claim 1 or 2, Characterized in that, The insulating circuit board has a filling material including a molding resin, a solder resist, a resin filler, or a glass epoxy resin on the wiring layer of the circuit portion where the convex portion is not provided.

4. The double-sided cooling power module according to any one of claims 1 to 3, Characterized in that, The insulating circuit board has a window portion around the convex portion of the circuit portion, the window portion penetrates the wiring layer to the surface of the resin film, and a filling material is provided in the window portion.

5. The double-sided cooling power module according to any one of claims 1 to 4, Characterized in that, The thickness of the resin film of the insulating circuit board is 40 μm or more and less than 160 μm.

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