Semiconductor Devices

Abstract

A semiconductor device (100) comprises: a power module (101) having a plurality of semiconductor elements; and a cooler (14) that has a cooling surface (20), and that is configured so that the power module (101) is thermally connected to the cooling surface (20) with a bonding material (15), which has a solder material, interposed therebetween. When viewed in a direction perpendicular to the cooling surface (20), the plurality of semiconductor elements are arranged at positions that do not overlap with each other. The cooling surface (20) has a recessed section (17), and when viewed in a direction perpendicular to the cooling surface (20), the recessed section (17) is disposed at a position that overlaps with a bonding material (15) provided between the cooling surface (20) and the power module (101) and does not overlap with the plurality of semiconductor elements.

Description

[Technical Field]

[0001] The present application relates to a semiconductor device. [Background technology]

[0002] In recent years, the capacity of semiconductor devices incorporating high-power semiconductor elements has been increasing. In these semiconductor devices with increased capacity, in order to pass a large current through the semiconductor elements, it is necessary to efficiently transfer the heat generated in the semiconductor elements to a cooler. Therefore, in these semiconductor devices with increased capacity, there is a demand for low thermal resistance in the bonding material that is provided between the semiconductor elements and the cooler and that connects the structural members.

[0003] The configuration of a semiconductor device that aims to reduce the thermal resistance of a bonding material containing a solder material has been disclosed (see, for example, Patent Document 1). In the configuration disclosed in Patent Document 1, a plating layer such as nickel plating or copper plating is provided on the surface of the power module that is bonded to the cooler, improving solder wettability, thereby improving the bonding reliability between the power module and the cooler and reducing the thermal resistance of the bonding material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6183556 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned Patent Document 1, a plating layer is provided on the joining surface of the power module, thereby improving solder wettability. For semiconductor devices with a plating layer, a solder joining method using formic acid reduction equipment or a vacuum solder joining method using a highly active flux is required. However, both methods cause variations in solder wettability in joining materials containing solder material. The resulting variations in solder wettability cause solder voids. In particular, when a plating layer is provided, gas is generated from organic components contained in the plating layer at the temperature at which the solder melts, and if the gas is not discharged to the outside, solder voids form. When solder voids form between a semiconductor element and a cooler, the cooling of the semiconductor element is hindered by the solder voids, increasing thermal resistance, and there is a concern that the quality of the semiconductor device may be reduced.

[0006] Therefore, an object of the present invention is to obtain a semiconductor device that improves the bonding quality of a bonding material containing a solder material and achieves low thermal resistance. [Means for solving the problem]

[0007] The semiconductor device disclosed in the present application comprises a power module having a plurality of semiconductor elements, and a cooler having a cooling surface, the power module being thermally connected to the cooling surface via a bonding material having a solder material, the plurality of semiconductor elements being arranged in positions where they do not overlap one another when viewed in a direction perpendicular to the cooling surface, the cooling surface having a recess, the recess being arranged in a position where it overlaps with the bonding material provided between the cooling surface and the power module and does not overlap with the plurality of semiconductor elements when viewed in the direction perpendicular to the cooling surface, a lower member being exposed in the recess, and the exposed portion of the lower member being the surface of the recess. The outer periphery of the gap between the cooling surface and the power module has a non-bonded region where no bonding material is provided, and when viewed in a direction perpendicular to the cooling surface, the recess extends from the region where the bonding material is provided to the non-bonded region, and the power module has a protrusion that protrudes toward the recess in the non-bonded region. do. [Effects of the Invention]

[0008] According to the semiconductor device disclosed in the present application, the semiconductor device comprises a power module having a plurality of semiconductor elements, and a cooler having a cooling surface, the power module being thermally connected to the cooling surface via a bonding material having a solder material, and when viewed in a direction perpendicular to the cooling surface, the plurality of semiconductor elements are arranged in positions where they do not overlap one another, the cooling surface has a recess, and the recess is arranged in a position where it overlaps with the bonding material provided between the cooling surface and the power module and does not overlap with the plurality of semiconductor elements. Therefore, when the power module and the cooler are joined with the bonding material, the recess serves as a path for discharging gas generated between the power module and the cooler to the outside, and the generation of voids remaining between the plurality of semiconductor elements and the cooler when the bonding material solidifies is suppressed, thereby improving the bonding quality of the bonding material and achieving low thermal resistance of the bonding material. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a plan view showing an outline of a semiconductor device according to a first embodiment. [Figure 2] 2 is a cross-sectional view of the semiconductor device taken along the line AA in FIG. 1. [Figure 3] FIG. 10 is a cross-sectional view showing an outline of another semiconductor device according to the first embodiment. [Figure 4] FIG. 10 is a cross-sectional view showing an outline of a semiconductor device according to a second embodiment. [Figure 5] FIG. 10 is a cross-sectional view showing an outline of a semiconductor device according to a third embodiment. [Figure 6] FIG. 10 is a plan view showing an outline of a semiconductor device according to a fourth embodiment. [Figure 7] FIG. 10 is a plan view showing an outline of a semiconductor device according to a fifth embodiment. [Figure 8] 8 is a cross-sectional view of the semiconductor device taken along the line BB in FIG. 7. [Figure 9] FIG. 13 is a plan view showing an outline of another semiconductor device according to the fifth embodiment. [Figure 10] FIG. 13 is a cross-sectional view showing an outline of a semiconductor device according to a sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a semiconductor device according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding members and parts are denoted by the same reference numerals.

[0011] Embodiment 1 Fig. 1 is a plan view showing an outline of a semiconductor device 100 according to a first embodiment, in which only the outer shape of a sealing resin 13 is shown, and Fig. 2 is a cross-sectional view of the semiconductor device 100 taken along the line AA in Fig. 1. The semiconductor device 100 is a device that converts, for example, an input current from DC to AC, or from AC to DC, or an input voltage to a different voltage.

[0012] <Semiconductor device 100> As shown in FIG. 2, the semiconductor device 100 includes a power module 101 having a plurality of semiconductor elements and a cooler 14. The cooler 14 has a cooling surface 20, and the power module 101 is thermally connected to the cooling surface 20 via a bonding material 15 having a solder material. In this manner, the power module 101 and the cooler 14 are bonded together to form the semiconductor device 100. Among the plurality of semiconductor elements, one of two adjacently arranged semiconductor elements is designated as a first semiconductor element, and the other is designated as a second semiconductor element. In this embodiment, as shown in FIG. 1, the power module 101 includes first semiconductor elements 1 and 2 and second semiconductor elements 5 and 6. In this manner, the first semiconductor element is formed from the two first semiconductor elements 1 and 2, and the second semiconductor element is formed from the two second semiconductor elements 5 and 6. However, the present invention is not limited to this, and each of the first semiconductor element and the second semiconductor element may be formed from a single semiconductor element.

[0013] <Power Module 101> The power module 101 includes first semiconductor elements 1 and 2, a first heat spreader 3, second semiconductor elements 5 and 6, a second heat spreader 7, an insulating material 11, a copper plate 12, and a sealing resin 13. The first semiconductor elements 1 and 2 are electrically connected to one side of the first heat spreader 3 by a chip bonding material (not shown). The second semiconductor elements 5 and 6 are electrically connected to one side of the second heat spreader 7 by a chip bonding material (not shown). The second heat spreader 7 is arranged on the same plane as the first heat spreader 3 with a gap therebetween. The chip bonding material may be, for example, solder or a sintered material made of Ag nanoparticles or Cu nanoparticles. As shown in FIG. 2, one side of the insulating material 11 is thermally connected to the other side of the first heat spreader 3 and the other side of the second heat spreader 7. One side of the copper plate 12 is thermally connected to the other side of the insulating material 11. The sealing resin 13 covers the first heat spreader 3, the second heat spreader 7, the first semiconductor elements 1 and 2, the second semiconductor elements 5 and 6, and the insulating material 11, with the other surface of the copper plate 12 exposed. Heat generated when the semiconductor elements are operating is transmitted in this order through the chip bonding material, the first heat spreader 3 and the second heat spreader 7, the insulating material 11, and the copper plate 12, and then through the bonding material 15 to the cooling surface 20, where it is dissipated from the cooler 14.

[0014] 1, a first semiconductor element 1 and a second semiconductor element 5 as switching elements, and a first semiconductor element 2 and a second semiconductor element 6 as rectifying elements are connected in anti-parallel to form two element pairs. The configuration of the power module 101 is not limited to this, and it is possible to mount a required number of first semiconductor elements and second semiconductor elements depending on the application of the semiconductor device 100.

[0015] The following describes the configuration of the lead frame of the connecting member in the power module 101. In this embodiment, the power module 101 has a first lead frame 4, a second lead frame 8, a third lead frame 9, and a fourth lead frame 10. The configuration of the lead frame is not limited to this, and when the number of mounted semiconductor elements changes as described above, the configuration of the lead frame may be changed according to the number of mounted semiconductor elements.

[0016] One end of the first lead frame 4 is electrically connected to one surface of the first heat spreader 3 by a lead bonding material (not shown), and the other end is exposed from the sealing resin 13. The second lead frame 8 electrically connects one surface of the first semiconductor elements 1 and 2 by a chip bonding material (not shown) and one surface of the second heat spreader 7 by a lead bonding material (not shown). The third lead frame 9 is electrically connected to one surface of the second semiconductor elements 5 and 6 by a chip bonding material (not shown), and the other end is exposed from the sealing resin 13. The fourth lead frame 10 is electrically connected to one surface of the second heat spreader 7 by a lead bonding material (not shown), and the other end is exposed from the sealing resin 13. The lead bonding material is composed of, for example, a bonding material containing a solder material to ensure electrical connection between the lead frame and the heat spreader. Bonding is not limited to using a lead bonding material, and metal bonding using ultrasonic waves or a laser may also be used.

[0017] The details of each component of the power module 101 will be described. The first semiconductor element 1 and the second semiconductor element 5 are power semiconductor elements, such as IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), which are power control semiconductor elements. In this embodiment, a switching element without a parasitic diode, such as an IGBT, is used, and a rectifying element, such as a freewheeling diode, is connected in parallel. However, the present invention is not limited to this. RC-IGBTs (Reverse Conducting IGBTs) in which a switching element and a freewheeling diode are integrated may also be used. Alternatively, a MOSFET may be used, with its parasitic diode used as the freewheeling diode. When an RC-IGBT or the like is used, each of the first semiconductor element and the second semiconductor element is formed of a single semiconductor element.

[0018] The first semiconductor elements 1 and 2 and the second semiconductor elements 5 and 6 are formed on semiconductor substrates made of materials such as silicon, silicon carbide (SiC), or gallium nitride (GaN), and wide bandgap semiconductor elements using materials such as silicon carbide, which have a wider bandgap than silicon, can be used. When wide bandgap semiconductor elements are used, the time change di / dt of current generated during switching can be made larger than that of elements made of silicon. Furthermore, wide bandgap semiconductor elements have low on-resistance, high allowable current density, low power loss, and low heat generation, allowing for a reduction in chip area. Because the chip area is reduced, the power module 101 can be made smaller.

[0019] The first heat spreader 3, the second heat spreader 7, the first lead frame 4, the second lead frame 8, the third lead frame 9, and the fourth lead frame 10 are made of metal materials with excellent electrical conductivity. Among metals with excellent electrical conductivity, copper is a particularly desirable material for these components in terms of electrical resistance, workability, cost, etc. Here, copper refers to pure copper or a copper alloy containing copper as its main component.

[0020] To prevent the thermal deformation force caused by the difference in linear expansion coefficients from becoming large, it is preferable to use a resin for the sealing resin 13 having a linear expansion coefficient close to that of the first heat spreader 3, the second heat spreader 7, the first lead frame 4, the second lead frame 8, the third lead frame 9, and the fourth lead frame 10. Therefore, since the linear expansion coefficient of pure copper is 16 ppm / K to 17 ppm / K, it is desirable that the linear expansion coefficient of the sealing resin 13 is also 15 ppm / K to 18 ppm / K. The sealing resin 13 is, for example, an inorganic filler contained in a thermosetting resin such as an epoxy resin.

[0021] The insulating material 11 is required to have heat dissipation properties that allow it to transfer and dissipate heat generated when the first semiconductor elements 1 and 2 and the second semiconductor elements 5 and 6 are in operation to the cooler 14 while ensuring electrical insulation between the semiconductor elements and the copper plate 12. The insulating material 11 is, for example, a thermosetting resin filled with an inorganic filler that has high thermal conductivity and insulating properties, and bonds the first heat spreader 3 and the second heat spreader 7 to the copper plate 12 through a thermosetting reaction of the resin. Here, the insulating material 11 is made of a material that combines heat dissipation properties, insulating properties, and adhesive properties, and is configured to contain an inorganic powder filler such as highly thermally conductive ceramic particles in a thermosetting resin such as epoxy resin. Suitable inorganic fillers with high thermal conductivity include ceramic particles such as aluminum nitride, silicon nitride, boron nitride, aluminum oxide (alumina), silicon oxide (silica), magnesium oxide, zinc oxide, and titanium oxide. Any of these inorganic fillers may be used alone, or a mixture of two or more types may be used.

[0022] <Cooler 14> The cooler 14, which is thermally connected to the cooling surface 20 of the power module 101, is required to have high cooling performance. The cooler 14 includes multiple heat dissipation fins (not shown) to efficiently dissipate heat transferred from the power module 101. The heat dissipation fins are provided, for example, on the side of the cooler 14 opposite the power module 101. The cooler 14 may be either a liquid-cooled or air-cooled cooler. In this embodiment, the cooler 14 is configured as a flat metal heat sink, but this is not limited thereto. A liquid-cooled cooler having a flow path through which a cooling liquid flows may also be used. The cooler 14 is preferably formed from a material selected from the group consisting of copper, aluminum, and alloys of copper and aluminum. Aluminum or an aluminum alloy, which is an alloy containing aluminum, is particularly suitable as the material for the cooler 14 because it is lightweight and has excellent processability. Using aluminum or an aluminum alloy as the material for the cooler 14 can reduce the weight of the semiconductor device 100. Furthermore, productivity of the semiconductor device 100 can be improved.

[0023] The other surface of the copper plate 12 of the power module 101, which is exposed from the sealing resin 13, is thermally connected to the cooling surface 20 of the cooler 14 by a bonding material 15. In order to solder the power module 101 to the cooling surface 20 with high bonding quality using the bonding material 15, the cooling surface 20 of the cooler 14 must have high solder wettability. Therefore, the material of the cooler 14 is preferably copper, which has solder wettability. However, as described above, if the material of the main body of the cooler 14 is aluminum or an aluminum alloy, it is optimal to provide a plating layer 16, which has solder wettability, as the cooling surface 20 of the cooler 14, and to use copper as the material for the plating layer 16. Instead of directly providing the plating layer 16 on the aluminum or aluminum alloy, a nickel plating layer (not shown) may be applied as an undercoat plating layer to improve plating adhesion and surface solder wettability.

[0024] In this embodiment, the cooler 14 is made of aluminum or an aluminum alloy, and a plating layer 16 is provided on the power module 101 side of the cooler 14, as shown in Fig. 2. Therefore, the cooling surface 20 is the surface of the plating layer 16, which has solder wettability. That is, of the bonding surfaces at which the power module 101 and the cooler 14 are bonded by the bonding material 15, one bonding surface is the other surface of the copper plate 12, and the other bonding surface, or cooling surface 20, is the plating layer 16 provided on the surface of the cooler 14.

[0025] <Recess 17 of cooling surface 20> The recess 17 of the cooling surface 20, which is a key feature of the present application, will now be described. When viewed perpendicularly to the cooling surface 20, the first semiconductor elements 1 and 2 and the second semiconductor elements 5 and 6, which are multiple semiconductor elements, are arranged in positions where they do not overlap one another. The cooling surface 20 has a recess 17. When viewed perpendicularly to the cooling surface 20, the recess 17 is arranged in a position that overlaps with the bonding material 15 provided between the cooling surface 20 and the power module 101 but does not overlap with the first semiconductor elements 1 and 2 and the second semiconductor elements 5 and 6. The recess 17 penetrates the plating layer 16, exposing the member below the plating layer 16. The exposed member below has lower solder wettability than the plating layer 16. The exposed portion of the member below is the recess surface 18. In this embodiment, the exposed member below is aluminum or an aluminum alloy.

[0026] When the plating layer 16 is provided, gas is generated from the organic components contained in the plating layer 16 at the temperature at which the solder melts, and if the gas is not discharged to the outside, it becomes a solder void. If a solder void occurs between the semiconductor element and the cooler 14, the cooling of the semiconductor element is hindered by the solder void and the thermal resistance increases, resulting in a decrease in the quality of the semiconductor device 100. Such voids are not limited to those generated from the plating layer 16; if there is a gap between the bonding material 15 and another component when the bonding material 15 is melted, the gap may also be the cause of the void.

[0027] By providing the recess 17 at a position on the cooling surface 20 that does not overlap with the first semiconductor elements 1, 2 and the second semiconductor elements 5, 6, the recess 17 serves as a path for discharging gas generated between the power module 101 and the cooler 14 to the outside when the power module 101 and the cooler 14 are bonded with the bonding material 15. Therefore, even if solder voids are generated, the solder voids are discharged to the outside through the recess 17. Because the solder voids are discharged to the outside through the recess 17, the generation of voids remaining between the first semiconductor elements 1, 2 and the second semiconductor elements 5, 6 and the cooler 14 when the bonding material 15 solidifies can be suppressed. Because the generation of voids remaining between the first semiconductor elements 1, 2 and the second semiconductor elements 5, 6 and the cooler 14 is suppressed, the spaces between the first semiconductor elements 1, 2 and the second semiconductor elements 5, 6 and the cooler 14 are filled with the bonding material 15 and the plating layer 16, which improves the bonding quality of the bonding material 15 containing the solder material and reduces the thermal resistance of the bonding material 15. Furthermore, since the spaces between the first semiconductor elements 1, 2 and the second semiconductor elements 5, 6 and the cooler 14 are filled with the bonding material 15 and the plating layer 16, the heat generated in each semiconductor element can be efficiently transferred to the cooler 14.

[0028] In this embodiment, the recess 17 is disposed between the first heat spreader 3 and the second heat spreader 7, as viewed in a direction perpendicular to the cooling surface 20, at a position that does not overlap with the first heat spreader 3 and the second heat spreader 7. With this configuration, there are no recesses 17 between the first heat spreader 3 and the second heat spreader 7 and the cooler 14. The spaces between the first heat spreader 3 and the second heat spreader 7 and the cooler 14 are filled with the bonding material 15 and the plating layer 16. This allows heat generated not only in the semiconductor elements but also in the lead frames and heat spreaders to be efficiently transferred to the cooler 14. The location of the recess 17 is not limited to this. The recess 17 may be disposed in another region as long as it does not impede heat transfer and does not overlap with the first semiconductor elements 1 and 2 and the second semiconductor elements 5 and 6. Even when the recess 17 is disposed in another region, it is possible to achieve low thermal resistance of the bonding material 15 and suppress solder voids.

[0029] In this embodiment, the exposed lower member is aluminum or an aluminum alloy, and has lower solder wettability than the plating layer 16. With this configuration, the bonding material 15 and the recess surface 18 are not bonded in the recess 17, so that a path for discharging gas to the outside can be reliably formed in the recess 17.

[0030] In this embodiment, the recess 17 is a groove that extends beyond the bonding material 15 provided between the cooling surface 20 and the power module 101 when viewed in a direction perpendicular to the cooling surface 20. With this configuration, the recess 17 has a portion that extends beyond the bonding material 15, making it possible to easily discharge gas to the outside. The arrangement of the recess 17 is not limited to a configuration in which it extends beyond the bonding material 15, but it may be arranged only inside the bonding material 15. When the recess 17 is arranged inside the bonding material 15, gas cannot be discharged to the outside, but it is possible to discharge gas to the recess 17. Furthermore, when the recess 17 is arranged only inside the bonding material 15, it is possible to prevent moisture, foreign matter, and the like from entering the interior of the semiconductor device 100 from the outside through the recess 17.

[0031] An example of a method for forming the recess 17 in the cooler 14 will be described. After applying the plating layer 16 to the entire cooler 14, the recess 17 can be formed by cutting and removing the portion of the plating layer 16 in the area where the recess 17 is to be formed. By forming the recess 17 in this manner, the recess 17 can be easily formed at low cost. In this embodiment, the recess 17 penetrates the plating layer 16, exposing the member below the plating layer 16. Using this formation method, the recess 17 can be easily formed, thereby improving the productivity of the semiconductor device 100. Note that the method for forming the recess 17 is not limited to this. A method of masking the area where the recess 17 is to be formed during the plating process and plating the area of ​​the cooler 14 excluding the area where the recess 17 is to be formed may also be used.

[0032] In this embodiment, the material of the cooler 14 is aluminum or an aluminum alloy, and the plating layer 16 is provided on the power module 101 side of the cooler 14, but this is not limited to this. The material of the cooler 14 may be copper or a copper alloy, and the plating layer 16 containing nickel or tin may be provided on the power module 101 side of the cooler 14.

[0033] Furthermore, when the cooler 14 is made of copper or a copper alloy, as shown in FIG. 3, the cooling surface 20 may be formed on the side of the power module 101 of the cooler 14, which is made of copper or a copper alloy, without providing the plating layer 16, and a recess 17 may be provided on this cooling surface 20. FIG. 3 is a cross-sectional view showing a schematic diagram of another semiconductor device 100 according to the first embodiment, taken at the same position as in FIG. 2. In this case, since the plating layer 16 is not provided, no gas is generated from the plating layer 16. However, if there is a gap between the bonding material 15 and another component when melting the bonding material 15, the gap may cause voids. Such voids can be evacuated to the outside through the recess 17. To ensure the formation of a void evacuating path in the recess 17, an aluminum layer may be formed on the recess surface 18 of the recess 17 by sputtering or the like.

[0034] As described above, the semiconductor device 100 according to the first embodiment includes a power module 101 having first semiconductor elements 1, 2 and second semiconductor elements 5, 6, and a cooler 14 having a cooling surface 20, the power module 101 being thermally connected to the cooling surface 20 via a bonding material 15 having a solder material, the first semiconductor elements 1, 2 and the second semiconductor elements 5, 6 being arranged in positions where they do not overlap each other when viewed in a direction perpendicular to the cooling surface 20, the cooling surface 20 having a recess 17 and overlapping with the bonding material 15 provided between the cooling surface 20 and the power module 101, Since the recess 17 is arranged at a position that does not overlap with the first semiconductor elements 1, 2 and the second semiconductor elements 5, 6, when the power module 101 and the cooler 14 are joined with the bonding material 15, the recess 17 serves as a path for discharging gas generated between the power module 101 and the cooler 14 to the outside, and the generation of voids remaining between the first semiconductor elements 1, 2 and the second semiconductor elements 5, 6 and the cooler 14 when the bonding material 15 solidifies is suppressed, thereby improving the bonding quality of the bonding material 15 and achieving low thermal resistance of the bonding material 15.

[0035] When a power module 101 has a first heat spreader 3 to which first semiconductor elements 1, 2 are electrically connected on one side and arranged on the same plane as the first heat spreader 3 at a distance from each other, and a second heat spreader 7 to which second semiconductor elements 5, 6 are electrically connected on one side, and a recess 17 is arranged between the first heat spreader 3 and the second heat spreader 7 in a position that does not overlap with the first heat spreader 3 and the second heat spreader 7 when viewed in a direction perpendicular to the cooling surface 20, no recess 17 is provided between the first heat spreader 3 and the second heat spreader 7 and the cooler 14, and therefore heat generated not only in each semiconductor element but also in each lead frame and each heat spreader can be efficiently transferred to the cooler 14.

[0036] When the cooling surface 20 is the surface of the plating layer 16 that is solder wettable, and the recess 17 penetrates the plating layer 16, exposing the component below the plating layer 16, the power module 101 can be solder-joined to the cooler 14 with high joining quality, and the recess 17 can be easily formed at low cost.

[0037] If the exposed lower member has lower solder wettability than the plating layer 16, the bonding material 15 and the recess surface 18 are not bonded in the recess 17, so that a path for discharging gas to the outside can be reliably formed in the recess 17. Furthermore, if the exposed lower member is aluminum or an aluminum alloy, the weight of the semiconductor device 100 can be reduced, and the productivity of the semiconductor device 100 can be improved.

[0038] When the recess 17 is a groove that extends beyond the bonding material 15 provided between the cooling surface 20 and the power module 101 when viewed in a direction perpendicular to the cooling surface 20, the recess 17 has a portion that extends beyond the bonding material 15, so that gas can be easily discharged to the outside.

[0039] Embodiment 2 A semiconductor device 100 according to embodiment 2 will be described. Fig. 4 is a cross-sectional view showing an outline of the semiconductor device 100 according to embodiment 2, taken along the same line as in Fig. 2. In the semiconductor device 100 according to embodiment 2, the cross-sectional shape of the recess 17 is different from that of embodiment 1.

[0040] The recess 17 is also formed in the exposed lower member. The recess surface 18 of the recess 17 is provided closer to the cooler 14 than the portion of the plating layer 16 on the cooler 14 side. By configuring in this manner, the cross-sectional area of ​​the recess 17 can be made larger than the cross-sectional area of ​​the recess 17 shown in the first embodiment. Because the cross-sectional area of ​​the recess 17 is larger, gas generated when the power module 101 and the cooler 14 are joined by the bonding material 15 can be more efficiently discharged to the outside.

[0041] In this embodiment, the cross-sectional shape of the recess 17 is rectangular, but the cross-sectional shape of the recess 17 is not limited to rectangular. Since the recess 17 only needs to function as a path for discharging gas generated between the power module 101 and the cooler 14 to the outside, the cross-sectional shape of the recess 17 may be V-shaped or U-shaped.

[0042] An example of a method for forming the recess 17 in the cooler 14 will be described. After applying the plating layer 16 to the entire cooler 14, the recess 17 can be formed by cutting and removing the plating layer 16 and the cooler 14 in the area where the recess 17 is to be formed. By forming the recess 17 in this manner, the recess 17 can be formed easily and at low cost. Note that the method for forming the recess 17 is not limited to this. It is also possible to use a method in which a groove that will become the recess 17 is previously formed in the part of the cooler 14 where the recess 17 is to be formed, the part of the groove that will form the recess 17 is masked during the plating process, and the part of the cooler 14 excluding the part where the recess 17 is to be formed is plated.

[0043] Embodiment 3 A semiconductor device 100 according to a third embodiment will be described. Fig. 5 is a cross-sectional view showing an outline of the semiconductor device 100 according to the third embodiment, taken along the same line as in Fig. 2. The semiconductor device 100 according to the third embodiment has a configuration in which a power module 101 is provided with a recess 19 on the module side.

[0044] The surface of the power module 101 on the bonding material 15 side has a module-side recess 19. When viewed in a direction perpendicular to the cooling surface 20, the module-side recess 19 is arranged at a position that overlaps with the bonding material 15 provided between the cooling surface 20 and the power module 101 but does not overlap with the multiple semiconductor elements. In this embodiment, the module-side recess 19 is arranged between the first semiconductor elements 1 and 2 and the second semiconductor elements 5 and 6.

[0045] The recess 19 on the module side is a path for discharging to the outside gas generated when the power module 101 and the cooler 14 are bonded together with the bonding material 15. With this configuration, it is possible to provide an additional path for discharging gas to the outside in addition to the recess 17. Since an additional path for discharging gas to the outside is formed, it is possible to more efficiently discharge to the outside gas generated when the power module 101 and the cooler 14 are bonded together compared to the first embodiment.

[0046] In this embodiment, the module-side recess 19 is provided on the power module 101 side of the recess 17, but the arrangement of the module-side recess 19 is not limited to this. If necessary, the module-side recess 19 may be arranged in a different position. The number of module-side recess 19 is also not limited to one, and multiple module-side recesses 19 may be provided.

[0047] In this embodiment, the cross-sectional shape of the recess 19 on the module side is rectangular, but the cross-sectional shape of the recess 19 on the module side is not limited to rectangular. The cross-sectional shape of the recess 19 on the module side may be V-shaped or U-shaped, as long as it functions as a path for discharging gas generated between the power module 101 and the cooler 14 to the outside.

[0048] In this embodiment, an example is shown in which the module-side recess 19 is provided in the semiconductor device 100 shown in embodiment 1, but this is not limited to this, and the module-side recess 19 may also be provided in the semiconductor device 100 shown in embodiment 2.

[0049] Embodiment 4 A semiconductor device 100 according to a fourth embodiment will be described. Fig. 6 is a plan view showing an outline of the semiconductor device 100 according to the fourth embodiment, showing only the outline of the sealing resin 13 and omitting the lead frame. The semiconductor device 100 according to the fourth embodiment has a configuration in which a plurality of semiconductor elements and a plurality of recesses are provided.

[0050] In this embodiment, the power module 101 has a configuration known as a 6-in-1 power module. In Fig. 6, first semiconductor elements 1a, 1b, and 1c are arranged on a first heat spreader 3 on the upper side at intervals in the horizontal direction of the first heat spreader 3, and second semiconductor elements 5a, 5b, and 5c are provided on second heat spreaders 7a, 7b, and 7c on the lower side. The first semiconductor elements 1a, 1b, and 1c are provided near the center of each of the three sections obtained by dividing the first heat spreader 3 horizontally.

[0051] The arrangement of the recesses will be described. When viewed in a direction perpendicular to the cooling surface 20, the recess 17 is disposed between the first heat spreader 3 and the second heat spreaders 7a, 7b, and 7c, at a position not overlapping with the first heat spreader 3 and the second heat spreaders 7a, 7b, and 7c. When viewed in a direction perpendicular to the cooling surface 20, the recess 17a is disposed between the second heat spreaders 7a and 7b, at a position not overlapping with the second heat spreaders 7a and 7b. When viewed in a direction perpendicular to the cooling surface 20, the recess 17b is disposed between the second heat spreaders 7b and 7c, at a position not overlapping with the second heat spreaders 7b and 7c. When viewed in a direction perpendicular to the cooling surface 20, the recess 17c is disposed between the first semiconductor elements 1a and 1b, at a position not overlapping with the first semiconductor elements 1a and 1b. When viewed in a direction perpendicular to the cooling surface 20, the recess 17d is disposed between the first semiconductor elements 1b and 1c at a position that does not overlap with the first semiconductor elements 1b and 1c.

[0052] In this embodiment, recesses are provided not only between the semiconductor elements and between the heat spreaders, but also between the semiconductor elements that are not between the heat spreaders. In this way, when the semiconductor elements are arranged with a large gap between them, by providing recesses also between the semiconductor elements that are not between the heat spreaders, gas generated when the power module 101 and the cooler 14 are joined by the bonding material 15 can be more efficiently discharged to the outside.

[0053] 6, and may be arranged differently as long as it overlaps with the bonding material 15 provided between the cooling surface 20 and the power module 101 and does not overlap with the multiple semiconductor elements when viewed in a direction perpendicular to the cooling surface 20. Even if the arrangement is different, it is possible to achieve low thermal resistance of the bonding material 15 and suppression of solder voids.

[0054] In this embodiment, the recesses 17, 17a, 17b, 17c, and 17d extend beyond the bonding material 15 provided between the cooling surface 20 and the power module 101 when viewed in a direction perpendicular to the cooling surface 20. , 17a, 17b, 17c, 17d The arrangement of the recesses 17, 17a, 17b, 17c, and 17d is not limited to a configuration in which they extend outward from the bonding material 15, and they may be arranged only inside the bonding material 15. When the recesses 17, 17a, 17b, 17c, and 17d are arranged inside the bonding material 15, gas cannot be discharged to the outside, but it is possible to discharge gas into the recesses 17, 17a, 17b, 17c, and 17d. Furthermore, when the recesses 17, 17a, 17b, 17c, and 17d are arranged only inside the bonding material 15, it is possible to prevent moisture, foreign matter, and the like from entering the interior of the semiconductor device 100 from the outside through the recesses 17, 17a, 17b, 17c, and 17d.

[0055] Embodiment 5. A semiconductor device 100 according to the fifth embodiment will be described. Fig. 7 is a plan view showing an outline of the semiconductor device 100 according to the fifth embodiment, and Fig. 8 is a cross-sectional view of the semiconductor device 100 taken along the line BB in Fig. 7. In the semiconductor device 100 according to the fifth embodiment, a power module 101 has a protrusion 21.

[0056] In this embodiment, as shown in FIG. 7 , a non-bonding region 23, which is a region where no bonding material 15 is provided, is provided on the outer periphery of the gap between the cooling surface 20 and the power module 101. When viewed in a direction perpendicular to the cooling surface 20, the recess 17 extends from the region where the bonding material 15 is provided to the non-bonding region 23. In this embodiment, the recess 17 is also provided in a portion of the cooling surface 20 that does not overlap with the power module 101 when viewed in a direction perpendicular to the cooling surface 20. The power module 101 has a protrusion 21 that protrudes toward the recess 17 in the non-bonding region 23. In this embodiment, one protrusion 21 is provided in each of the two non-bonding regions 23 facing the recess 17. Multiple protrusions 21 may be provided in each of the non-bonding regions 23.

[0057] As shown in FIG. 8 , the protrusion 21 is a portion of the sealing resin 13 that seals the components constituting the power module 101, protruding toward the recess 17. The protrusion 21 is fabricated simultaneously when sealing the components constituting the power module 101. The fabrication method of the protrusion 21 is not limited thereto. For example, a component made of a metal material may be sealed together with the components constituting the power module 101, and the portion protruding from the sealing resin 13 may be used as the protrusion 21. Alternatively, a component that serves as the protrusion 21 may be attached to the non-bonding region 23 of the sealing resin 13 facing the recess 17. If the protrusion 21 is made of a metal with high solder wettability and is provided adjacent to the bonding material 15, the metal and solder will wet after gas is exhausted, thereby preventing foreign matter such as water from entering the recess 17. Note that fabricating the protrusion 21 from the sealing resin 13 simultaneously when sealing the components constituting the power module 101 eliminates the need for a separate component that serves as the protrusion 21, thereby improving the productivity of the semiconductor device 100. Therefore, it is desirable to form the protrusion 21 from the sealing resin 13 .

[0058] By providing the protrusion 21 in this manner, it is possible to maintain the function of efficiently discharging to the outside the gas generated when the power module 101 and the cooler 14 are bonded by the bonding material 15, while suppressing the intrusion of cleaning liquid between the power module 101 and the recess 17 in the cleaning process after bonding. By suppressing the intrusion of cleaning liquid, it is possible to prevent the cleaning liquid from spraying out from between the power module 101 and the recess 17 during the subsequent drying process and adhering to the surface of the power module 101. Since the adhesion of cleaning liquid to the surface of the power module 101 is suppressed, it is possible to improve the insulation properties of the creeping surface of the power module 101.

[0059] In FIG. 7, the protrusion 21 is disposed in the center of the non-bonding region 23 in the direction in which the recess 17 extends, but the location of the protrusion 21 is not limited to the center of the non-bonding region 23. As shown in FIG. 9, the protrusion 21 may be disposed at the outer edge of the non-bonding region 23. FIG. 9 is a plan view showing an outline of another semiconductor device 100 according to the fifth embodiment. With this configuration, the area into which the cleaning liquid can penetrate can be reduced, thereby further improving the insulation performance on the creeping surface of the power module 101. Note that the closer the protrusion 21 is disposed to the outer edge of the non-bonding region 23, the greater the effect of reducing the area into which the cleaning liquid can penetrate.

[0060] In this embodiment, as shown in FIG. 8 , the height of the protrusion 21 is greater than the depth of the recess 17, and a gap is provided between the protrusion 21 and the inner surface of the recess 17. FIG. 8 shows the cross-sectional shapes of the protrusion 21 and the recess 17. While simply providing the protrusion 21 can prevent the cleaning liquid from entering between the power module 101 and the recess 17, the effect of preventing the cleaning liquid from entering can be further enhanced if the height of the protrusion 21 is greater than the depth of the recess 17 and a gap is provided between the protrusion 21 and the inner surface of the recess 17. Specifically, if the dimension between the top 21 a of the protrusion 21 and the bottom 22 of the recess is less than 0.22 mm, moisture can enter but is not discharged to the outside, thereby improving insulation. If the dimension between the top 21 a of the protrusion 21 and the bottom 22 of the recess is 0.08 mm or less, moisture can be prevented from entering, thereby achieving a greater effect in improving insulation.

[0061] 8, the vertical cross section of the protrusion 21 is rectangular, but the shape of the vertical cross section of the protrusion 21 is not limited to a rectangle. The vertical cross section of the protrusion 21 may have, for example, a V-shape or a U-shape, as long as it maintains the function of serving as a path for discharging gas generated between the power module 101 and the cooler 14 to the outside and has the function of preventing the intrusion of a cleaning liquid from the outside.

[0062] In this embodiment, as shown in Fig. 7, the cross-sectional shape of the protrusion 21 is circular, but the cross-sectional shape of the protrusion 21 is not limited to circular. The cross-sectional shape of the protrusion 21 may be, for example, a square or hexagon, as long as it maintains its function as a path for discharging gas generated between the power module 101 and the cooler 14 to the outside and has the function of suppressing the intrusion of a cleaning liquid from the outside. Note that when the top 21a of the protrusion 21 is disposed inside the recess 17, the smaller the cross-sectional shape of the protrusion 21 that reduces the gap between the side wall of the recess 17 and the side wall of the protrusion 21, the greater the effect of suppressing the intrusion of a cleaning liquid.

[0063] Embodiment 6 A semiconductor device 100 according to a sixth embodiment will be described. Fig. 10 is a cross-sectional view showing an outline of the semiconductor device 100 according to the sixth embodiment, taken at the same position as in Fig. 8. The semiconductor device 100 according to the sixth embodiment has a configuration in which the position of the top 21a of the protrusion 21 is defined.

[0064] The top 21a of the protrusion 21 is disposed inside the recess 17, and a gap is provided between the protrusion 21 and the inner surface of the recess 17. With this configuration, the distance between the top 21a of the protrusion 21 and the bottom 22 of the recess can be reduced. Because the distance between the top 21a of the protrusion 21 and the bottom 22 of the recess is reduced, the effect of suppressing the intrusion of the cleaning liquid can be further enhanced while maintaining the function of the passage for discharging gas generated between the power module 101 and the cooler 14 to the outside. Because the effect of suppressing the intrusion of the cleaning liquid is further enhanced, the insulation of the creeping surface of the power module 101 can be further improved.

[0065] In this embodiment, as in the fifth embodiment, the height of the protrusion 21 is greater than the depth of the recess 17, and a gap is provided between the protrusion 21 and the inner surface of the recess 17, so that the same effect as in the fifth embodiment is achieved. In addition, in this embodiment, the shape of the vertical cross section of the protrusion 21 is rectangular, but the shape of the vertical cross section of the protrusion 21 is not limited to a rectangle. The shape of the vertical cross section of the protrusion 21 may be, for example, a V-shape or a U-shape.

[0066] Furthermore, while the present application describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are conceivable within the scope of the technology disclosed in the present specification, including, for example, cases where at least one component is modified, added, or omitted, and cases where at least one component is extracted and combined with components of another embodiment.

[0067] Various aspects of the present disclosure are summarized below as appendices.

[0068] (Appendix 1) a power module having a plurality of semiconductor elements; a cooler having a cooling surface, the power module being thermally connected to the cooling surface via a bonding material having a solder material; When viewed in a direction perpendicular to the cooling surface, the semiconductor elements are arranged so as not to overlap one another, the cooling surface has a recess; The semiconductor device has a recess arranged at a position that overlaps with the bonding material provided between the cooling surface and the power module and does not overlap with the plurality of semiconductor elements when viewed in a direction perpendicular to the cooling surface. (Appendix 2) one of the two adjacently arranged semiconductor elements is a first semiconductor element and the other is a second semiconductor element; The power module comprises: the first semiconductor element; a first heat spreader having one surface to which the first semiconductor element is electrically connected; the second semiconductor element; a second heat spreader arranged on the same plane as the first heat spreader with a gap therebetween, the second semiconductor element being electrically connected to one surface of the second heat spreader; an insulating material in which the other surface of the first heat spreader and the other surface of the second heat spreader are thermally connected to one surface; a copper plate whose other surface is thermally connected to one surface of the insulating material; a sealing resin covering the first heat spreader, the second heat spreader, the first semiconductor element, the second semiconductor element, and the insulating material with the other surface of the copper plate exposed; 2. The semiconductor device according to claim 1, wherein the recess is positioned between the first heat spreader and the second heat spreader at a position that does not overlap with the first heat spreader and the second heat spreader when viewed in a direction perpendicular to the cooling surface. (Appendix 3) the cooling surface is a surface of a plating layer having solder wettability; 3. The semiconductor device according to claim 1, wherein the recess penetrates the plating layer and exposes a member below the plating layer. (Appendix 4) 4. The semiconductor device according to claim 3, wherein the exposed lower member has lower solder wettability than the plating layer. (Appendix 5) 5. The semiconductor device according to claim 4, wherein the exposed lower member is aluminum or an aluminum alloy. (Appendix 6) 6. The semiconductor device according to claim 3, wherein the recess is also formed in the exposed lower member. (Appendix 7) 7. The semiconductor device according to any one of claims 1 to 6, wherein the recess is a groove that extends beyond the bonding material provided between the cooling surface and the power module when viewed in a direction perpendicular to the cooling surface. (Appendix 8) a surface of the power module on the bonding material side has a module-side recess; 8. The semiconductor device according to claim 1, wherein the recess on the module side is arranged at a position that overlaps with the bonding material provided between the cooling surface and the power module but does not overlap with the plurality of semiconductor elements, when viewed in a direction perpendicular to the cooling surface. (Appendix 9) a non-bonding region, which is a region where the bonding material is not provided, is provided at an outer periphery of the gap between the cooling surface and the power module; When viewed in a direction perpendicular to the cooling surface, the recess extends from the region where the bonding material is provided to the non-bonded region, 8. The semiconductor device according to claim 1, wherein the power module has a protrusion that protrudes toward the recess in the non-bonding region. (Appendix 10) 10. The semiconductor device according to claim 9, wherein the height of the protrusion is greater than the depth of the recess, and a gap is provided between the protrusion and an inner surface of the recess. (Appendix 11) 10. The semiconductor device according to claim 9, wherein the top of the protrusion is disposed inside the recess, and a gap is provided between the protrusion and an inner surface of the recess. (Appendix 12) 12. The semiconductor device according to claim 9, wherein the protrusion is disposed at an outer end of the non-bonding region. [Explanation of symbols]

[0069] 1, 1a, 1b, 1c, 2 First semiconductor element, 3 First heat spreader, 4 First lead frame, 5, 5a, 5b, 5c, 6 Second semiconductor element, 7, 7a, 7b, 7c Second heat spreader, 8 Second lead frame, 9 Third lead frame, 10 Fourth lead frame, 11 Insulating material, 12 Copper plate, 13 Sealing resin, 14 Cooler, 15 Bonding material, 16 Plating layer, 17, 17a, 17b, 17c, 17d Recess, 18 Recess surface, 19 Recess on module side, 20 Cooling surface, 21 Protruding portion, 21a Top portion, 22 Recess bottom portion, 23 Non-bonding area, 100 Semiconductor device, 101 Power module

Claims

1. a power module having a plurality of semiconductor elements; a cooler having a cooling surface, the power module being thermally connected to the cooling surface via a bonding material having a solder material; When viewed in a direction perpendicular to the cooling surface, the semiconductor elements are arranged so as not to overlap one another, the cooling surface has a recess; the recess is disposed at a position that overlaps with the bonding material provided between the cooling surface and the power module but does not overlap with the plurality of semiconductor elements, as viewed in a direction perpendicular to the cooling surface; In the recess, the lower member is exposed, the exposed portion of the lower member is a recessed surface, a non-bonding region, which is a region where the bonding material is not provided, is provided at an outer periphery of the gap between the cooling surface and the power module; When viewed in a direction perpendicular to the cooling surface, the recess extends from the region where the bonding material is provided to the non-bonded region, The power module is a semiconductor device having a protrusion that protrudes toward the recess in the non-bonded region.

2. one of the two adjacently arranged semiconductor elements is a first semiconductor element and the other is a second semiconductor element; The power module comprises: the first semiconductor element; a first heat spreader having one surface to which the first semiconductor element is electrically connected; the second semiconductor element; a second heat spreader arranged on the same plane as the first heat spreader with a gap therebetween, the second semiconductor element being electrically connected to one surface of the second heat spreader; an insulating material in which the other surface of the first heat spreader and the other surface of the second heat spreader are thermally connected to one surface; a copper plate whose other surface is thermally connected to one surface of the insulating material; a sealing resin covering the first heat spreader, the second heat spreader, the first semiconductor element, the second semiconductor element, and the insulating material with the other surface of the copper plate exposed; 2. The semiconductor device according to claim 1, wherein the recess is positioned between the first heat spreader and the second heat spreader at a position that does not overlap with the first heat spreader and the second heat spreader when viewed in a direction perpendicular to the cooling surface.

3. the cooling surface is a surface of a plating layer having solder wettability; 3. The semiconductor device according to claim 1, wherein the recess penetrates the plating layer, exposing a member below the plating layer.

4. The semiconductor device according to claim 3 , wherein the exposed lower member has lower solder wettability than the plating layer.

5. 5. The semiconductor device according to claim 4, wherein the exposed lower member is made of aluminum or an aluminum alloy.

6. 4. The semiconductor device according to claim 3, wherein the recess is also formed in the exposed lower member.

7. 3. The semiconductor device according to claim 1, wherein the recess is a groove extending beyond the bonding material provided between the cooling surface and the power module when viewed in a direction perpendicular to the cooling surface.

8. a surface of the power module on the bonding material side has a module-side recess; 3. The semiconductor device according to claim 1, wherein the recess on the module side is arranged at a position that overlaps with the bonding material provided between the cooling surface and the power module and does not overlap with the plurality of semiconductor elements when viewed in a direction perpendicular to the cooling surface.

9. 2. The semiconductor device according to claim 1, wherein the height of the protrusion is greater than the depth of the recess, and a gap is provided between the protrusion and an inner side surface of the recess.

10. 2. The semiconductor device according to claim 1, wherein the top of the protrusion is disposed inside the recess, and a gap is provided between the protrusion and an inner side surface of the recess.

11. The semiconductor device according to claim 1 , wherein the protrusion is disposed at an outer end of the non-bonding region.

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