Semiconductor device and power conversion device

Abstract

To provide a technique which reduces a thermal stress generated in a resin insulation layer in a semiconductor device, and can obtain high long-term reliability.SOLUTION: A semiconductor device 202 includes: semiconductor elements 14; a heat spreader 16 where the semiconductor elements 14 are mounted on one main surface; a resin insulation layer 17 which is provided on the other main surface on a side opposite to the one main surface in the heat spreader 16; a copper foil 18 which is provided on a surface on a side opposite to the heat spreader 16 in the resin insulation layer 17, and is joined to a cooler 2; and a sealing resin 11 for sealing the semiconductor elements 14, the heat spreader 16, the resin insulation layer 17 and the copper foil 18, in a state in which the surface on a side opposite to the resin insulation layer 17 in the copper foil 18 is exposed. The resin insulation layer 17 and the copper foil 18 have the same contour shape, and corner parts of the resin insulation layer 17 and the copper foil 18 are formed in R chamfered shapes.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a semiconductor device and a power conversion device. [Background technology]

[0002] Patent Document 1 discloses a semiconductor device including a submodule and a cooler joined to the submodule with a solder joint material. A semiconductor element is mounted on the upper surface of a heat spreader. A copper plate is joined to the lower surface of the heat spreader via a resin insulating layer. The semiconductor element, the heat spreader, the resin insulating layer, and the copper plate are integrated with a thermosetting resin encapsulant to form a submodule. One surface of the cooler and the copper plate exposed from the bottom surface of the submodule are joined via a solder joint material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-111765 Summary of the Invention [Problem to be solved by the invention]

[0004] It is economical to use Cu, which has high thermal and electrical conductivity, as the main constituent material of the submodule, but Al, which has better workability than Cu, is mainly used as the constituent material of the cooler. In this case, there is a difference in the linear expansion coefficient between the submodule and the cooler. Cu is about 18 ppm / K and Al is about 23 ppm / K, and the operating temperature of a semiconductor device is high, such as 150°C or 175°C as the temperature of the semiconductor element from room temperature (or outside temperature), so the difference in linear expansion coefficient between the submodule and the cooler generates thermal stress in the solder joint material.

[0005] In the semiconductor device described in Patent Document 1, for example, epoxy resin mixed with a filler having insulating properties and high thermal conductivity, such as BN, Al2O3, or AlN, is used as the resin insulation layer of the submodule, but in order to obtain high thermal conductivity, the filler ratio needs to be increased to 80% or more. However, if the ratio of epoxy resin is reduced, the flexibility decreases and the resin insulation layer becomes brittle.

[0006] Due to the difference in linear expansion coefficient between the submodule and the heat sink, thermal stress is also transmitted to the resin insulating layer that is bonded to the copper plate due to an action-reaction relationship, and the resin insulating layer may be damaged due to the thermal stress. Therefore, in order to ensure high long-term reliability in semiconductor devices, it is necessary to reduce the thermal stress.

[0007] Therefore, an object of the present disclosure is to provide a technique capable of reducing thermal stress occurring in a resin insulating layer in a semiconductor device and achieving high long-term reliability. [Means for solving the problem]

[0008] The semiconductor device according to the present disclosure is a semiconductor device joined to a cooler, comprising: a semiconductor element; a heat spreader having the semiconductor element mounted on one main surface; a resin insulation layer provided on the other main surface of the heat spreader opposite the one main surface; a metal foil provided on the surface of the resin insulation layer opposite the heat spreader and joined to the cooler; and a sealing resin that seals the semiconductor element, the heat spreader, the resin insulation layer, and the metal foil with the surface of the metal foil opposite the resin insulation layer exposed, wherein the resin insulation layer and the metal foil have the same contour shape, and corners of the resin insulation layer and the metal foil are formed into a R-chamfered shape. Effect of the Invention

[0009] According to the present disclosure, it is possible to reduce the thermal stress occurring at the corners of the resin insulating layer, which is susceptible to damage, thereby achieving high long-term reliability in the semiconductor device. [Brief description of the drawings]

[0010] [Figure 1] 2 is a cross-sectional view showing a state in which the semiconductor device according to the first embodiment is joined to a cooler. FIG. [Diagram 2] FIG. 2 is a back view of the semiconductor device according to the first embodiment. [Diagram 3] 11 is a cross-sectional view showing a state in which a semiconductor device according to a second embodiment is joined to a cooler. FIG. [Figure 4] 11 is a cross-sectional view showing a state in which a semiconductor device according to a third embodiment is joined to a cooler. FIG. [Diagram 5] FIG. 13 is a back view of a semiconductor device according to a modified example of the third embodiment. [Figure 6] 13 is a cross-sectional view showing a state in which a semiconductor device according to a fourth embodiment is joined to a cooler. FIG. [Figure 7] 13 is a cross-sectional view showing a state in which a semiconductor device according to a fifth embodiment is joined to a cooler. FIG. [Figure 8] 13 is a cross-sectional view showing a state in which a semiconductor device according to a first modification of the fifth embodiment is joined to a cooler. FIG. [Figure 9] FIG. 13 is a back view showing an example of a semiconductor device according to a fifth embodiment. [Figure 10] FIG. 13 is a back view showing another example of the semiconductor device according to the fifth embodiment. [Figure 11] FIG. 13 is a back view showing still another example of the semiconductor device according to the fifth embodiment. [Figure 12] FIG. 13 is a block diagram showing a configuration of a power conversion system to which a power conversion device according to a sixth embodiment is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <Embodiment 1> <Configuration of Semiconductor Device> The first embodiment will be described below with reference to the drawings. Fig. 1 is a cross-sectional view showing a state in which a semiconductor device 202 according to the first embodiment is joined to a cooler 2. Fig. 2 is a rear view of the semiconductor device 202 according to the first embodiment.

[0012] In FIG. 1, the X direction, the Y direction, and the Z direction are mutually orthogonal. The X direction, the Y direction, and the Z direction shown in the following figures are also mutually orthogonal. In the following, the direction including the X direction and the -X direction opposite to the X direction is also referred to as the "X-axis direction". In the following, the direction including the Y direction and the -Y direction opposite to the Y direction is also referred to as the "Y-axis direction". In the following, the direction including the Z direction and the -Z direction opposite to the Z direction is also referred to as the "Z-axis direction".

[0013] First, a description will be given of the overall structure of the semiconductor device 202 according to the embodiment 1. As shown in Fig. 1 and Fig. 2, the semiconductor device 202 includes a plurality of (e.g., eleven) lead frames 12, a plurality of (e.g., two) semiconductor elements 14, a heat spreader 16, a resin insulating layer 17, a copper foil 18, and a sealing resin 11.

[0014] A plurality of (eg, two) semiconductor elements 14 are mounted on one main surface (surface in the Z direction) of the heat spreader 16 with solder layers 15 interposed therebetween.

[0015] The semiconductor element 14 is an element that functions as, for example, a switching element or a rectifying element. The switching element may be, for example, an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), or other vertical semiconductor element. The rectifying element is a diode element. The number of semiconductor elements 14 is not limited to two, and may be three or more.

[0016] One end side of two of the multiple lead frames 12 is joined to the upper surfaces (surfaces in the Z direction) of the two semiconductor elements 14 via a solder layer 13. In addition, one end side of the remaining lead frame 12 is joined to one main surface (surface in the Z direction) of the heat spreader 16 via a solder layer (not shown).

[0017] A resin insulating layer 17 is provided on the other main surface (-Z direction surface) of the heat spreader 16. The other main surface of the heat spreader 16 is the surface opposite to one main surface of the heat spreader 16. In addition, a copper foil 18 is provided as a metal foil to be joined to the cooler 2 on the surface of the resin insulating layer 17 opposite to the heat spreader 16 (-Z direction surface).

[0018] The sealing resin 11 is, for example, an epoxy-based thermosetting resin. The sealing resin 11 seals the multiple lead frames 12, the multiple semiconductor elements 14, the heat spreader 16, the resin insulating layer 17, and the copper foil 18 with the surface of the copper foil 18 opposite to the resin insulating layer 17 (the surface in the -Z direction) exposed. In addition, the tip portions (the other end side) of the multiple lead frames 12 protrude from the sealing resin 11. The tip portions of two of the multiple lead frames 12 extend in the -X direction, and the tip portion of the remaining lead frame 12 extends in the X direction.

[0019] Next, the configuration of each part will be specifically described. For example, a copper strip having a thickness of about 0.3 mm to 4 mm is used as the heat spreader 16. It may be produced by punching a copper strip of a certain thickness, or a copper strip having a thin portion of 0.3 mm to 1.0 mm and a thick portion of 1.5 mm or more during rolling may be used. Alternatively, a member in which a thick metal member having a thickness of 1.0 mm to 4 mm and a thin strip having a thickness of about 0.3 mm to 1.0 mm are joined together may be used as the heat spreader 16.

[0020] The heat spreader 16 is bonded to the resin insulating layer 17. In this state, the end of the resin insulating layer 17 protrudes a certain length from the end of the heat spreader 16. With this configuration, the insulation distance from the heat spreader 16 to the copper foil 18 does not pass only through the side portion of the resin insulating layer 17, but passes through the adhesive interface formed by the sealing resin 11 and the end of the resin insulating layer 17 protruding by a certain length.

[0021] With this configuration, it is possible to improve insulation by ensuring a distance between the portion directly below (in the -Z direction) of heat spreader 16 to which an electric field is applied and the side portion of resin insulation layer 17. In addition, even if resin insulation layer 17 absorbs moisture, it is possible to lengthen the time until the portion directly below heat spreader 16 absorbs moisture, which has the advantage of improving insulation reliability.

[0022] As described above, the semiconductor element 14 has been described as being joined to the heat spreader 16 by soldering, but it may be joined to the heat spreader 16 by sintering instead of soldering. In addition, the main surface of the semiconductor element 14 opposite to the surface joined to the heat spreader 16 may be wired with Al wire bonds or Al alloy wire bonds, or another metal conductor may be joined by soldering or sintering.

[0023] By using sintering bonding to bond the semiconductor element 14 and the heat spreader 16, the melting point of the bonding material in the sealing resin 11 can be made higher than the melting point of the solder layer 3, which is the bonding material between the semiconductor device 202 and the cooler 2. This makes it possible to suppress melting of the bonding material in the semiconductor device 202 when bonding the semiconductor device 202 to the cooler 2.

[0024] When soldering is used to join the semiconductor element 14 and the heat spreader 16, two types of solder with different melting points must be used between the semiconductor device 202 and the cooler 2, and between the semiconductor element 14 and the heat spreader 16. In this case, the difference in melting points between the two types of solder must be set to at least 20K in order to reduce the investment costs for production facilities and the proportion of products that are discarded as defective.

[0025] When sinter bonding is used in the semiconductor device 202, it goes without saying that the melting temperature after sintering must be higher than the melting temperature of the bonding material between the semiconductor device 202 and the cooler 2. For example, a sinter bonding material using Ag nanoparticles, a hybrid sinter bonding material in which Ag nanoparticles are mixed with microparticles, or a sinter bonding material in which Cu nanoparticles are mixed, various bonding materials aimed at increasing the melting point are commercially available, so an economically appropriate one can be selected.

[0026] As described above, the sealing resin 11 is, for example, an epoxy-based thermosetting resin. The sealing resin 11 may be molded by transfer molding, or may be molded by combining with a thermoplastic resin by injection molding. However, since the thermoplastic resin has almost no adhesive strength to the semiconductor element 14, it is preferable to encapsulate the semiconductor element 14 with a resin having adhesive properties. For example, by using an epoxy-based thermosetting resin or potting with polyimide, it is possible to ensure an adhesive encapsulation state for the semiconductor element 14. By sealing the periphery of the semiconductor element 14 with a hardening resin, the period until the insulation characteristics are deteriorated due to the intrusion of moisture can be extended to an appropriate level for the use of the product.

[0027] It is preferable to use a material with a linear expansion coefficient close to that of the heat spreader 16 and the cooler 2 as the sealing resin 11. When the same type of material is used for the heat spreader 16 and the cooler 2, it is preferable to use a material with a linear expansion coefficient similar to that of both of them as the sealing resin 11. However, it is effective to suppress the occurrence of thermal stress by setting the total amount of change caused by the curing shrinkage of the resin during thermal curing and the amount of change caused by the temperature difference from the thermal curing temperature to room temperature to a value close to the amount of change of the heat spreader 16 and the cooler 2. When the heat spreader 16 and the cooler 2 are made of materials with different linear expansion coefficients, the thermal stress can be dramatically reduced by setting the total amount of curing shrinkage and the amount of shrinkage caused by the linear expansion coefficient to be the amount of shrinkage between the heat spreader 16 and the cooler 2. This allows the guarantee period of the long-term reliability of the product to be extended.

[0028] Next, the shapes of the resin insulating layer 17 and the copper foil 18, which are characteristic of the semiconductor device 202 according to the first embodiment, will be described.

[0029] 1 and 2, the resin insulation layer 17 and the copper foil 18 have the same contour shape. Specifically, the resin insulation layer 17 and the copper foil 18 have the same rectangular shape when viewed from the Z-axis direction, and are the same size. Therefore, the side surfaces (surfaces in the X-axis direction and the Y-axis direction) of the resin insulation layer 17 and the copper foil 18 have no steps. Note that the contour shapes of the resin insulation layer 17 and the copper foil 18 being the same does not only mean that they are completely the same, but also includes cases where there are slight differences due to manufacturing errors, etc.

[0030] Making the contour shapes of resin insulation layer 17 and copper foil 18 the same can be achieved by first forming a composite of copper foil and resin insulation layer by adopting a gap-controlled resin coating process for rolled copper foil, and then punching out the copper foil and resin insulation layer by press processing.

[0031] 2, the resin insulation layer 17 and the copper foil 18 are formed in a rectangular shape. Furthermore, the four corners of the resin insulation layer 17 and the copper foil 18 are formed in a rounded chamfered shape. That is, the four corners of the resin insulation layer 17 are formed with rounded chamfered portions (not shown), and the four corners of the copper foil 18 are formed with rounded chamfered portions 18a.

[0032] The resin insulating layer 17 and the copper foil 18 are formed to have a contour shape that is, for example, 2 mm larger on each side than the contour shape of the heat spreader 16. In other words, the resin insulating layer 17 and the copper foil 18 protrude from the heat spreader 16. Damage caused by the press processing when forming the resin insulating layer 17 and the copper foil 18 remains on the periphery of both, so that the withstand voltage characteristics of the periphery are lower than those of the other parts. By protruding the resin insulating layer 17 and the copper foil 18 from the heat spreader 16, it is possible to prevent the electric field generated in the resin insulating layer 17 due to the potential difference between the part that is charged when the semiconductor device 202 is operated and the cooler 2 that is directly connected to the earth potential or the negative potential of the inverter from passing through the periphery of the resin insulating layer 17 and the copper foil 18. This ensures the insulation of the product.

[0033] However, since the thermal stress generated by soldering the copper foil 18 and the cooler 2 and the difference in the linear expansion coefficient between the semiconductor device 202 and the cooler 2 is greatest at the corners of the copper foil 18, the corners of the resin insulation layer 17 are most susceptible to damage.

[0034] In contrast, in the first embodiment, the corners of the resin insulating layer 17 and the copper foil 18 are formed in a rounded chamfered shape. The dimensions of the rounded chamfered portion of the resin insulating layer 17 may be approximately the same as the dimensional difference of the resin insulating layer 17 with respect to the heat spreader 16. For example, if the resin insulating layer 17 protrudes 2 mm on one side, a rounded radius of 2 mm can be used to ensure a uniform minimum clearance with respect to the peripheral portion where damage caused by press processing remains, thereby ensuring heat dissipation and long-term reliability without impairing insulation. The dimensions of the rounded chamfered portion 18a of the copper foil 18 are also the same as those of the resin insulating layer 17.

[0035] Here, the thickness of the copper foil 18 is 0.1 mm to 0.3 mm. With this thickness, the material can be supplied in roll form, and processing and material costs are economical. As the metal foil, other metals such as Al may be used instead of the copper foil 18. However, it is preferable that the metal foil has high thermal conductivity and excellent handling properties.

[0036] The resin insulating layer 17 is composed of a matrix material and a filler. For example, epoxy resin mixed with BN filler is used as the matrix material. BN has a thermal conductivity of about 60 W / mK to 90 W / mK, has good electrical conductivity, and is chemically stable. Al2O3, AlN, or the like may be used as the filler. However, it is preferable that the material does not decompose due to moisture absorption, and that a surface protective film is provided.

[0037] The filler content is preferably about 50% to 95%. The higher the content, the higher the thermal conductivity, but if the filler content is too high, there are problems such as voids easily forming in the mixture and strength decreasing. The inventors of the present application have confirmed that within the above range, a resin insulating layer 17 without problems in terms of long-term reliability can be obtained.

[0038] It is preferable to apply a primer treatment to the filler. The adhesiveness of the resin insulating layer 17 to the matrix material is improved, and the mechanical strength can be improved. In addition, by mixing fillers that have been previously aggregated into a spherical shape, the heat transfer coefficient between the fillers can be improved, and the thermal conductivity of the entire resin insulating layer 17 can be increased. According to Paschen's law, if there are defects such as voids of about 4 μm to 100 μm in the resin insulating layer 17, partial discharge occurs at 1000 V or less, so even if there are defects, it is preferable to make them 4 μm or less. Such a state can be easily achieved by applying the resin insulating layer 17 to the copper foil 18 and then applying a pressure of 5 MPa or more at a temperature at which the epoxy resin softens. It is known that air exceeds the critical point of the triple point at 3.5 MPa or more, so it cannot maintain the volume of the gas and shrinks to the same volume as the liquid. According to Paschen's law, the pores that invade when the matrix material and the filler are mixed and kneaded can obtain high insulation such that discharge does not occur at several thousand V or less.

[0039] The cooler 2 is made of Al or Cu, which has good thermal conductivity, and is surface-coated with Ni plating, which is corrosion-resistant and has solder wettability. When Al is used, the inner surface of the refrigerant circuit of the cooler 2 may not be plated, and a coating that provides solder wettability may be applied to the soldering surface. When Cu is used, the inner surface of the refrigerant circuit of the cooler 2 may be Ni-plated. This makes it possible to suppress dissolution of Cu ions into the refrigerant, and to cool the refrigerant in combination with an Al heat exchanger (such as a radiator, not shown).

[0040] <Effects> As described above, the semiconductor device 202 according to the first embodiment includes the semiconductor element 14, the heat spreader 16 having the semiconductor element 14 mounted on one main surface thereof, the resin insulating layer 17 provided on the other main surface opposite to the one main surface of the heat spreader 16, the copper foil 18 provided on the surface of the resin insulating layer 17 opposite to the heat spreader 16 and bonded to the cooler 2, and the sealing resin 11 sealing the semiconductor element 14, the heat spreader 16, the resin insulating layer 17, and the copper foil 18 with the surface of the copper foil 18 opposite to the resin insulating layer 17 exposed. The resin insulating layer 17 and the copper foil 18 have the same contour shape, and the corners of the resin insulating layer 17 and the copper foil 18 are formed into a rounded chamfered shape.

[0041] Therefore, the thermal stress occurring at the corners of resin insulating layer 17, which is susceptible to damage, can be reduced, and high long-term reliability can be obtained in semiconductor device 202.

[0042] <Embodiment 2> Next, a semiconductor device 202 according to the second embodiment will be described. Fig. 3 is a cross-sectional view showing a state in which the semiconductor device 202 according to the second embodiment is joined to a cooler 2. In the second embodiment, the same components as those described in the first embodiment are denoted by the same reference numerals and the description thereof will be omitted.

[0043] As shown in Fig. 3, in the second embodiment, the size of the copper foil 18 is different from that in the first embodiment. Specifically, the copper foil 18 is formed larger than the resin insulating layer 17 and protrudes beyond the resin insulating layer 17. In other words, the resin insulating layer 17 is disposed on the inner side of the copper foil 18. Such a structure can be manufactured by the following method.

[0044] First, a roll of copper foil is sent out, and a printing mask is used to fix a resin insulation layer to the copper foil so that it protrudes beyond the peripheral edge of the heat spreader 16. The composite of the copper foil and the resin insulation layer is once wound into a roll after, for example, a drying process, and then the copper foil is punched out using a press die that does not come into contact with the resin insulation layer. With this method, it is possible to form the resin insulation layer 17 larger than the heat spreader 16, and the copper foil 18 larger than the resin insulation layer 17.

[0045] Next, a description will be given of the effect of the semiconductor device 202 according to the second embodiment. The thermal stress caused by soldering the copper foil 18 and the cooler 2 and the difference in linear expansion coefficient between the semiconductor device 202 and the cooler 2 is maximum at the corners of the copper foil 18, so that the corners of the resin insulating layer 17 are most likely to be damaged.

[0046] In contrast, the semiconductor device 202 according to the second embodiment includes a semiconductor element 14, a heat spreader 16 having the semiconductor element 14 mounted on one main surface thereof, a resin insulating layer 17 provided on the other main surface of the heat spreader 16 opposite the one main surface thereof, a copper foil 18 provided on the surface of the resin insulating layer 17 opposite the heat spreader 16 and joined to the cooler 2, and a sealing resin 11 that seals the semiconductor element 14, the heat spreader 16, the resin insulating layer 17, and the copper foil 18 with the surface of the copper foil 18 opposite the resin insulating layer 17 exposed. The copper foil 18 protrudes beyond the resin insulating layer 17.

[0047] Therefore, the thermal stress generated in the resin insulating layer 17 can be made smaller than when the copper foil 18 and the resin insulating layer 17 are the same size, and the thermal stress generated in the easily damaged corners of the resin insulating layer 17 can be reduced, thereby achieving high long-term reliability in the semiconductor device 202.

[0048] Also, a fillet can be formed so that the contour shape of the solder layer 3 between the semiconductor device 202 and the cooler 2 is larger than the contour shape of the copper foil 18. In this case, the thermal cross-sectional area passing through the solder layer 3 is larger than when the copper foil 18 and the resin insulating layer 17 are the same size, so that the thermal resistance passing through the solder layer 3 from the semiconductor device 202 to the cooler 2 can be reduced. In other words, the heat dissipation of the semiconductor device 202 is improved by the amount that the copper foil 18 is made larger than the resin insulating layer 17. In this way, in the second embodiment, since the copper foil 18 is larger than the resin insulating layer 17, it is possible to improve the insulation and also improve the heat dissipation.

[0049] <Embodiment 3> Next, a semiconductor device 202 according to a third embodiment will be described. Fig. 4 is a cross-sectional view showing a state in which the semiconductor device 202 according to the third embodiment is joined to a cooler 2. In the third embodiment, the same components as those described in the first and second embodiments are denoted by the same reference numerals and the description thereof will be omitted.

[0050] 4, in the third embodiment, unlike the first embodiment, the outer periphery of the surface of the copper foil 18 opposite to the resin insulating layer 17 is covered with the sealing resin 11. In other words, the peripheral portion of the resin insulating layer 17 and the side surfaces of the resin insulating layer 17 and the copper foil 18 cut by the press working are completely covered with the sealing resin 11.

[0051] Fig. 5 is a back view of a semiconductor device 202 according to a modification of the third embodiment. As shown in Fig. 5, the entire outer periphery of the surface of the copper foil 18 opposite to the resin insulating layer 17 is not covered with the sealing resin 11, but at least the four corners (four corners) of the resin insulating layer 17 where the most stress is concentrated need to be covered with the sealing resin 11. In other words, it is sufficient that at least the four corners of the surface of the copper foil 18 opposite to the resin insulating layer 17 are covered with the sealing resin 11.

[0052] As described above, the semiconductor device 202 according to the third embodiment includes the semiconductor element 14, the heat spreader 16 having the semiconductor element 14 mounted on one main surface thereof, the resin insulating layer 17 provided on the other main surface opposite the one main surface of the heat spreader 16, the copper foil 18 provided on the surface of the resin insulating layer 17 opposite the heat spreader 16 and bonded to the cooler 2, and the sealing resin 11 that seals the semiconductor element 14, the heat spreader 16, the resin insulating layer 17, and the copper foil 18 with the surface of the copper foil 18 opposite the resin insulating layer 17 exposed. The outer periphery of the surface of the copper foil 18 opposite the resin insulating layer 17 is covered with the sealing resin 11.

[0053] Therefore, the thermal stress occurring at the corners of resin insulating layer 17, which is susceptible to damage, can be reduced, and high long-term reliability can be obtained in semiconductor device 202.

[0054] Furthermore, at least the four corners of the surface of the copper foil 18 opposite to the resin insulating layer 17 are covered with the sealing resin 11. In this case as well, the semiconductor device 202 can achieve high long-term reliability.

[0055] <Fourth embodiment> Next, a semiconductor device 202 according to a fourth embodiment will be described. Fig. 6 is a cross-sectional view showing a state in which the semiconductor device 202 according to the fourth embodiment is joined to a cooler 2. In the fourth embodiment, the same components as those described in the first to third embodiments are denoted by the same reference numerals and description thereof will be omitted.

[0056] In the third embodiment, the portions of the sealing resin 11 covering at least the four corners of the copper foil 18 on the side opposite the resin insulating layer 17 were not in contact with the cooler 2. In contrast, as shown in Fig. 6, in the fourth embodiment, compared to the third embodiment, the portions of the sealing resin 11 covering at least the four corners of the copper foil 18 on the side opposite the resin insulating layer 17 are in contact with the cooler 2. Therefore, by having these portions in contact with the cooler 2, the minimum thickness of the solder layer 3 can be ensured.

[0057] As described above, in the semiconductor device 202 according to the fourth embodiment, the portions of the sealing resin 11 covering at least the four corners of the surface of the copper foil 18 opposite to the resin insulating layer 17 are in contact with the cooler 2. Therefore, the minimum thickness of the solder layer 3 can be ensured, and the thermal stress generated in the solder layer 3 can be reduced. This improves the durability of the solder layer 3. In other words, the thermal stress generated in the resin insulating layer 17 and the solder layer 3 can be reduced, and the durability of the semiconductor device 202 can be dramatically improved.

[0058] Although not shown, the signal terminals, which are the tips of the lead frames 12 in the semiconductor device 202, are inserted into through holes in one drive board, so the mounting accuracy of the semiconductor device 202 with respect to the cooler 2 is important. Since the inclination of the semiconductor device 202 with respect to the cooler 2 can be suppressed and the height position of the semiconductor device 202 can be made more uniform, the accuracy of the tip positions of the signal terminals (positions inserted into the through holes) is improved, and the insertability of the signal terminals is improved.

[0059] <Embodiment 5> Next, the semiconductor device 202 according to the fifth embodiment will be described. FIG. 7 is a cross-sectional view showing a state in which the semiconductor device 202 according to the fifth embodiment is joined to the cooler 2. FIG. 8 is a cross-sectional view showing a state in which the semiconductor device 202 according to the first modified example of the fifth embodiment is joined to the cooler 2. FIG. 9 is a back view showing an example of the semiconductor device 202 according to the fifth embodiment. FIG. 10 is a back view showing another example of the semiconductor device 202 according to the fifth embodiment. FIG. 11 is a back view showing yet another example of the semiconductor device 202 according to the fifth embodiment. In the fifth embodiment, the same components as those described in the first to fourth embodiments are denoted by the same reference numerals and description thereof will be omitted.

[0060] 7, in the fifth embodiment, unlike the first embodiment, a convex portion 19 capable of fitting with a concave portion 21 formed in the cooler 2 is formed in the sealing resin 11. Specifically, the convex portion 19 is formed around the R-chamfered portion 18a of the copper foil 18 in the sealing resin 11, and protrudes downward (in the -Z direction) from the lower end (the end in the -Z direction) of the sealing resin 11. In addition, the concave portion 21 is formed on the upper surface (the surface in the Z direction) of the cooler 2. This structure can improve the mounting accuracy (surface direction, height direction) of the semiconductor device 202 on the cooler 2.

[0061] Alternatively, as shown in FIG. 8, the convex portion may be composed of a first convex portion 19a capable of contacting the upper surface (surface in the Z direction) of the cooler 2, and a second convex portion 19b capable of fitting into the concave portion 21.

[0062] Furthermore, it is sufficient that the protrusions 19 are formed in at least two locations, and for example, they are formed in the locations shown in Figures 9 to 11. In Figure 11, the protrusions 19 are formed on the side surface of the lower end portion (portion in the -Z direction) of the sealing resin 11. Note that the number of protrusions 19 is not limited to two, and may be formed in three or more locations.

[0063] As described above, in the semiconductor device 202 according to the fifth embodiment, the sealing resin 11 is formed with the convex portion 19 that can be fitted into the concave portion 21 formed in the cooler 2.

[0064] Therefore, the mounting accuracy (surface direction, height direction) of the semiconductor device 202 on the cooler 2 can be improved.

[0065] 8, by forming the protrusions in two stages, it is possible to realize high accuracy in the planar direction and high accuracy in the height direction. That is, it is possible to improve the accuracy of the height position of the solder layer 3 in the first protrusion 19a, and to improve the mounting accuracy in the planar direction in the second protrusion 19b. This is a remarkable effect when mounting multiple semiconductor devices 202 on one cooler 2.

[0066] In addition, by fitting the convex portion 19 into the concave portion 21, the need for positioning jigs in the assembly process and the need for processes such as correcting the position of the signal terminals after soldering are eliminated, further contributing to improved productivity.

[0067] <Modifications of the First to Fifth Embodiments> In each embodiment, the semiconductor element 14 may be a general element using a silicon wafer as a base material, but may be made of a so-called wide band gap semiconductor material having a wider band gap than silicon, such as silicon carbide (SiC), gallium nitride (GaN)-based material, or diamond. When the semiconductor element 14 is made of a wide band gap semiconductor material and high temperature operation is enabled in the semiconductor element 14, a remarkable effect can be obtained. This is particularly suitable for a semiconductor element made of silicon carbide.

[0068] In addition, both the switching element and the rectifying element may be made of a wide band gap semiconductor material, or either one of the elements may be made of a wide band gap semiconductor material.

[0069] In each embodiment, a diagram showing one semiconductor device 202 joined to a cooler 2 has been used for explanation, but the configuration of each embodiment can also be applied when multiple (2, 3, 6, or 24, etc.) semiconductor devices 202 are joined to one cooler 2.

[0070] In addition, in each embodiment, the cooler 2 having pins as heat dissipation parts has been described as an example, but the above-mentioned effects can also be achieved with a cooler 2 that is a flat metal base plate without a heat dissipation part. The above-mentioned effects can also be achieved with a cooler 2 having a heat dissipation part of another shape instead of a pin.

[0071] <Sixth embodiment> In this embodiment, the semiconductor device 202 according to the above-mentioned embodiments 1 to 5 is applied to a power conversion device. Although the application of the semiconductor device 202 according to the embodiments 1 to 5 is not limited to a specific power conversion device, a case where the semiconductor device 202 according to the embodiments 1 to 5 is applied to a three-phase inverter will be described below as embodiment 6.

[0072] FIG. 12 is a block diagram showing a configuration of a power conversion system to which a power conversion device according to the sixth embodiment is applied. As shown in FIG.

[0073] The power conversion system shown in Fig. 12 is composed of a power source 100, a power conversion device 200, and a load 300. The power source 100 is a DC power source and supplies DC power to the power conversion device 200. The power source 100 can be composed of various things, for example, a DC system, a solar cell, or a storage battery, or it may be composed of a rectifier circuit connected to an AC system or an AC / DC converter. The power source 100 may also be composed of a DC / DC converter that converts DC power output from a DC system into a predetermined power.

[0074] The power conversion device 200 is a three-phase inverter connected between the power source 100 and the load 300, converts DC power supplied from the power source 100 into AC power, and supplies the AC power to the load 300. As shown in Fig. 12, the power conversion device 200 includes a main conversion circuit 201 that converts DC power into AC power and outputs it, and a control circuit 203 that outputs a control signal for controlling the main conversion circuit 201 to the main conversion circuit 201.

[0075] The load 300 is a three-phase motor driven by AC power supplied from the power conversion device 200. The load 300 is not limited to a specific use, but is a motor mounted on various electric devices, and is used as, for example, a motor for a hybrid car, an electric car, a railroad car, an elevator, or an air conditioner.

[0076] The power conversion device 200 will be described in detail below. The main conversion circuit 201 includes switching elements (not shown) and free wheel diodes (not shown), and converts DC power supplied from the power source 100 into AC power by switching the switching elements, and supplies the AC power to the load 300. There are various specific circuit configurations of the main conversion circuit 201, but the main conversion circuit 201 according to this embodiment is a two-level three-phase full bridge circuit, and can be configured with six switching elements and six free wheel diodes connected in reverse parallel to each switching element. The semiconductor device 202 according to any one of the above-mentioned embodiments 1 to 5 is applied to at least one of the switching elements and free wheel diodes of the main conversion circuit 201. Two switching elements of the six switching elements are connected in series to configure upper and lower arms, and each upper and lower arm configures each phase (U phase, V phase, W phase) of the full bridge circuit. The output terminals of each upper and lower arm, i.e., the three output terminals of the main conversion circuit 201, are connected to the load 300.

[0077] The main conversion circuit 201 also includes a drive circuit (not shown) for driving each switching element, but the drive circuit may be built in the semiconductor device 202, or the semiconductor device 202 may include a drive circuit separately. The drive circuit generates drive signals for driving the switching elements of the main conversion circuit 201 and supplies them to the control electrodes of the switching elements of the main conversion circuit 201. Specifically, in accordance with a control signal from a control circuit 203 (described later), the drive circuit outputs to the control electrodes of each switching element a drive signal for turning the switching element on and a drive signal for turning the switching element off. When maintaining a switching element in the on state, the drive signal is a voltage signal (on signal) equal to or higher than the threshold voltage of the switching element, and when maintaining a switching element in the off state, the drive signal is a voltage signal (off signal) equal to or lower than the threshold voltage of the switching element.

[0078] The control circuit 203 controls the switching elements of the main conversion circuit 201 so that a desired power is supplied to the load 300. Specifically, the control circuit 203 calculates the time (on time) for each switching element of the main conversion circuit 201 to be in the on state based on the power to be supplied to the load 300. For example, the main conversion circuit 201 can be controlled by PWM control that modulates the on time of the switching elements according to the voltage to be output. Then, a control command (control signal) is output to a drive circuit provided in the main conversion circuit 201 so that an on signal is output to a switching element that should be in the on state at each time point, and an off signal is output to a switching element that should be in the off state. The drive circuit outputs an on signal or an off signal as a drive signal to the control electrode of each switching element according to this control signal.

[0079] In the power conversion device according to the present embodiment, the semiconductor device 202 according to any one of the first to fifth embodiments is applied as the switching element and free wheel diode of the main conversion circuit 201, and therefore high long-term reliability can be achieved.

[0080] In the present embodiment, an example in which the semiconductor device 202 according to the first to fifth embodiments is applied to a two-level three-phase inverter has been described, but the application of the semiconductor device 202 according to the first to fifth embodiments is not limited to this, and the semiconductor device 202 can be applied to various power conversion devices. In the present embodiment, the two-level power conversion device is described, but the semiconductor device 202 according to the first to fifth embodiments may be applied to a three-level or multi-level power conversion device, and when power is supplied to a single-phase load, the semiconductor device 202 according to the first to fifth embodiments may be applied to a single-phase inverter. Furthermore, when power is supplied to a DC load or the like, the semiconductor device 202 according to the first to fifth embodiments can also be applied to a DC / DC converter or an AC / DC converter.

[0081] In addition, the power conversion device to which the semiconductor device 202 according to any one of the first to fifth embodiments is applied is not limited to the case where the load described above is an electric motor, but can also be used, for example, as a power supply device for an electric discharge machine, a laser processing machine, an induction heating cooker, or a non-contact power supply system, and can also be used as a power conditioner for a solar power generation system, a power storage system, or the like.

[0082] It should be noted that the embodiments can be freely combined, and each embodiment can be modified or omitted as appropriate.

[0083] Various aspects of the present disclosure are summarized below as appendices.

[0084] (Appendix 1) A semiconductor device joined to a cooler, A semiconductor element; a heat spreader having the semiconductor element mounted on one main surface; a resin insulating layer provided on the other main surface of the heat spreader opposite to the one main surface; a metal foil provided on a surface of the resin insulation layer opposite to the heat spreader and joined to the cooler; a sealing resin that seals the semiconductor element, the heat spreader, the resin insulating layer, and the metal foil in a state where a surface of the metal foil opposite to the resin insulating layer is exposed; The resin insulation layer and the metal foil have the same contour shape, The semiconductor device, wherein corners of the resin insulating layer and the metal foil are formed into a rounded chamfered shape.

[0085] (Appendix 2) A semiconductor device joined to a cooler, A semiconductor element; a heat spreader having the semiconductor element mounted on one main surface; a resin insulating layer provided on the other main surface of the heat spreader opposite to the one main surface; a metal foil provided on a surface of the resin insulation layer opposite to the heat spreader and joined to the cooler; a sealing resin that seals the semiconductor element, the heat spreader, the resin insulating layer, and the metal foil in a state where a surface of the metal foil opposite to the resin insulating layer is exposed; The metal foil protrudes beyond the resin insulating layer.

[0086] (Appendix 3) A semiconductor device joined to a cooler, A semiconductor element; a heat spreader having the semiconductor element mounted on one main surface; a resin insulating layer provided on the other main surface of the heat spreader opposite to the one main surface; a metal foil provided on a surface of the resin insulation layer opposite to the heat spreader and joined to the cooler; a sealing resin that seals the semiconductor element, the heat spreader, the resin insulating layer, and the metal foil in a state where a surface of the metal foil opposite to the resin insulating layer is exposed; the outer periphery of the surface of the metal foil opposite to the resin insulating layer is covered with the sealing resin.

[0087] (Appendix 4) 4. The semiconductor device according to claim 3, wherein at least four corners of the surface of the metal foil opposite to the resin insulating layer are covered with the sealing resin.

[0088] (Appendix 5) 5. The semiconductor device according to claim 4, wherein the portion of the sealing resin covering at least four corners of the surface of the metal foil opposite to the resin insulating layer contacts the cooler.

[0089] (Appendix 6) 6. The semiconductor device according to claim 1, wherein the sealing resin has a protrusion that can be fitted into a recess that is formed in the cooler.

[0090] (Appendix 7) A main conversion circuit having the semiconductor device according to any one of Supplementary Note 1 to Supplementary Note 6, which converts input power and outputs the converted power; a control circuit that outputs a control signal for controlling the main conversion circuit to the main conversion circuit; A power conversion device comprising: [Explanation of symbols]

[0091] 2 cooler, 11 sealing resin, 14 semiconductor element, 16 heat spreader, 17 resin insulating layer, 18 copper foil, 18a R-chamfered portion, 19 convex portion, 19a first convex portion, 19b second convex portion, 21 concave portion, 200 power conversion device, 201 main conversion circuit, 202 semiconductor device, 203 control circuit.

Claims

1. A semiconductor device joined to a cooler, A semiconductor element; a heat spreader having the semiconductor element mounted on one main surface; a resin insulating layer provided on the other main surface of the heat spreader opposite to the one main surface; a metal foil provided on a surface of the resin insulation layer opposite to the heat spreader and joined to the cooler; a sealing resin that seals the semiconductor element, the heat spreader, the resin insulating layer, and the metal foil in a state where a surface of the metal foil opposite to the resin insulating layer is exposed; The resin insulation layer and the metal foil have the same contour shape, the resin insulating layer and the metal foil have corners that are rounded and chamfered.

2. A semiconductor device joined to a cooler, A semiconductor element; a heat spreader having the semiconductor element mounted on one main surface; a resin insulating layer provided on the other main surface of the heat spreader opposite to the one main surface; a metal foil provided on a surface of the resin insulation layer opposite to the heat spreader and joined to the cooler; a sealing resin that seals the semiconductor element, the heat spreader, the resin insulating layer, and the metal foil in a state where a surface of the metal foil opposite to the resin insulating layer is exposed; The metal foil protrudes beyond the resin insulating layer.

3. A semiconductor device joined to a cooler, A semiconductor element; a heat spreader having the semiconductor element mounted on one main surface; a resin insulating layer provided on the other main surface of the heat spreader opposite to the one main surface; a metal foil provided on a surface of the resin insulation layer opposite to the heat spreader and joined to the cooler; a sealing resin that seals the semiconductor element, the heat spreader, the resin insulating layer, and the metal foil in a state where a surface of the metal foil opposite to the resin insulating layer is exposed; the outer periphery of the surface of the metal foil opposite to the resin insulating layer is covered with the sealing resin.

4. The semiconductor device according to claim 3 , wherein at least four corners of the surface of said metal foil opposite to said resin insulating layer are covered with said sealing resin.

5. The semiconductor device according to claim 4 , wherein the sealing resin covers at least four corners of the surface of the metal foil opposite to the resin insulating layer, and the sealing resin contacts the cooler.

6. The semiconductor device according to claim 1 , wherein the sealing resin has a protrusion that can be fitted into a recess formed in the cooler.

7. A main conversion circuit having the semiconductor device according to any one of claims 1 to 5, which converts input power and outputs the converted power; a control circuit that outputs a control signal for controlling the main conversion circuit to the main conversion circuit; A power conversion device comprising:

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