Semiconductor module, method for manufacturing semiconductor module, and semiconductor device

Abstract

Provided are a highly reliable semiconductor module which includes a sealing material layer excellent in heat resistance and prevents, for example, peeling of the sealing material layer, a method for manufacturing the semiconductor module, and a semiconductor device. This semiconductor module comprises: a semiconductor element; and a sealing material layer that covers at least the semiconductor element and includes a low-elasticity core layer and a high-elasticity skin layer disposed on the outer peripheral surface of the core layer.

Description

Semiconductor Module, Method for Manufacturing Semiconductor Module, and Semiconductor Device

[0001] The present invention relates to a semiconductor module, a method for manufacturing a semiconductor module, and a semiconductor device.

[0002] Conventionally, epoxy resin molding materials have been widely used in the field of encapsulating materials for semiconductor elements such as transistors and ICs (Integrated Circuits). This is because epoxy resins have a balanced combination of electrical properties, moisture resistance, heat resistance, mechanical properties, and adhesion to inserted parts. With the miniaturization, weight reduction, and high performance of semiconductor devices in recent years, the density of semiconductor element or semiconductor module mounting has increased, and accordingly, heat generation in semiconductor devices has become remarkable. Also, the number of semiconductor devices operating at high temperatures has been increasing.

[0003] In particular, semiconductor modules equipped with power semiconductors for in-vehicle use and the like are expected to be exposed to high temperatures for a long time. For in-vehicle power modules, the mainstream method of encapsulation is to apply a method of encapsulation with a silicone gel called gel encapsulation in a case-type structure. However, from the viewpoints of improving mass productivity, vibration resistance, heat resistance temperature, etc., encapsulation by transfer molding using an epoxy resin molding material has been studied. In an insulated gate bipolar transistor (IGBT), which is a type of power semiconductor, the operating temperature is said to be about 175°C. Furthermore, in power semiconductors, the use of silicon carbide (SiC) devices with low power loss and excellent energy-saving performance is said to increase the operating temperature to 200°C or higher. Therefore, the encapsulating material used for semiconductor modules is required to have high heat resistance and a high glass transition temperature (Tg).

[0004] Patent Document 1 discloses that in a semiconductor module equipped with semiconductor elements such as IGBTs, heat generated during operation causes significant thermal stress due to the difference in thermal expansion coefficients between the semiconductor elements and the encapsulating material, resulting in cracks, delamination, etc., of the encapsulating material, particularly at the edges of the semiconductor elements. Patent Document 1 also discloses a method for manufacturing a semiconductor module, in which a buffer material is placed at the edges of the semiconductor elements, a wiring member is then connected to the upper electrodes of the semiconductor elements, and the semiconductor elements, buffer material, and wiring member are covered with an encapsulating material.

[0005] Patent No. 7157783

[0006] However, encapsulating materials with high Tg and excellent heat resistance have a problem in that, due to their high elasticity, internal stress accumulates due to the difference in thermal expansion coefficients between the encapsulating material layer and other components, making them prone to peeling of the encapsulating material layer and wire breakage, thus reducing the reliability of semiconductor modules and semiconductor devices equipped with semiconductor modules. Therefore, in view of these circumstances, the present disclosure aims to provide a highly reliable semiconductor module, a method for manufacturing a semiconductor module, and a semiconductor device that have a heat-resistant encapsulating material layer and prevent peeling of the encapsulating material layer.

[0007] Having achieved the above-mentioned objectives, this disclosure includes the following: <1> A semiconductor module comprising a semiconductor element and a encapsulating layer including at least a low-elasticity core layer covering the semiconductor element and a high-elasticity skin layer disposed on the outer peripheral surface of the core layer. <2> The semiconductor module according to <1>, wherein the skin layer in the encapsulating layer is disposed on the surface of the semiconductor element and as the outermost layer. <3> The semiconductor module according to <1> or <2>, comprising a wire connected to the semiconductor element, wherein the semiconductor element is in contact with the skin layer in the encapsulating layer, and the middle portion of the wire, excluding the connection portion with the semiconductor element, is embedded in the core layer in the encapsulating layer. <4> The semiconductor module according to <2> or <3>, wherein the thickness of the skin layer disposed on the surface of the semiconductor element is thinner than the thickness of the skin layer disposed as the outermost layer. <5> The semiconductor module according to any one of <1> to <4>, comprising an insulating heat dissipation circuit board on which the semiconductor element is mounted, wherein the insulating heat dissipation circuit board has a heat sink on the side opposite to the side on which the semiconductor element is mounted. <6> A semiconductor module according to any one of <1> to <5>, comprising an insulating heat dissipation circuit board on which the semiconductor element is mounted, wherein the insulating heat dissipation circuit board has heat sinks on both sides facing outward. <7> A semiconductor module according to any one of <1> to <6>, wherein the semiconductor element comprises a power semiconductor. <8> A semiconductor module according to any one of <1> to <7>, wherein the amount of inorganic filler contained in the first resin composition constituting the skin layer is greater than the amount of inorganic filler contained in the second resin composition constituting the core layer. <9> A method for manufacturing a semiconductor module, comprising the steps of: placing a semiconductor element in a cavity of a transfer molding apparatus; introducing a molten first resin composition into the cavity; then introducing a molten second resin composition into the cavity; and removing the semiconductor module according to any one of <1> to <8> from the cavity. <10> A method for manufacturing a semiconductor module according to <9>, wherein the skin layer containing the first resin composition is formed on the surface of the semiconductor element and on the inner surface of the cavity.<11> The method for manufacturing a semiconductor module according to <9> or <10>, wherein the first resin composition has lower fluidity compared to the second resin composition. <12> The method for manufacturing a semiconductor module according to <11>, wherein the flow distance measured as the length of the molded product when the first resin composition is molded using a spiral flow measuring mold compliant with EMMI-1-66 under conditions of mold temperature of 175°C, molding pressure of 7 MPa and curing time of 150 seconds is 0.9 times or less compared to the flow distance measured for the second resin composition. <13> The method for manufacturing a semiconductor module according to any one of <9> to <12>, wherein when the semiconductor element is placed in the cavity of a transfer molding apparatus, the heat sink in an insulating heat sink circuit board having the semiconductor element and the heat sink is brought into contact with a release film attached to the inner surface of the cavity. <14> A semiconductor device comprising the semiconductor module according to any one of <1> to <8>.

[0008] The semiconductor module and semiconductor device of this disclosure have a encapsulating layer that includes a low-elasticity core layer and a high-elasticity skin layer. As a result, the high-elasticity skin layer provides excellent heat resistance, and the low-elasticity core layer prevents peeling of the encapsulating layer, resulting in superior reliability. Furthermore, in the method for manufacturing the semiconductor module of this disclosure, a encapsulating layer including a low-elasticity core layer and a high-elasticity skin layer can be formed by sequentially introducing a first resin composition and a second resin composition into the cavity, respectively. According to the method for manufacturing the semiconductor module of this disclosure, a semiconductor module with excellent heat resistance due to the high-elasticity skin layer and peeling of the encapsulating layer due to the low-elasticity core layer can be manufactured, resulting in superior reliability.

[0009] Figure 1 is a cross-sectional view of a key part of one embodiment of the semiconductor module of the present disclosure. Figure 2 is a perspective view of one embodiment of the semiconductor module of the present disclosure. Figure 3 is a cross-sectional view of a key part of another embodiment of the semiconductor module of the present disclosure. Figure 4 is a cross-sectional view of a key part of a transfer molding apparatus applied to a method for manufacturing the semiconductor module of the present disclosure. Figure 5 is a cross-sectional view of a key part of a transfer molding apparatus applied to a method for manufacturing the semiconductor module of the present disclosure. Figure 6 is a cross-sectional view of a key part of an insulating heat dissipation circuit board placed in a cavity. This is a characteristic diagram showing the rubber strength measured for the first resin composition and the second resin composition. This is a photograph showing a cross-section of a molded body made using the first resin composition and the second resin composition. This is a schematic diagram showing the boundary between the skin layer and the core layer by line segments in a cross-section of a molded body made using the first resin composition and the second resin composition. This is a schematic diagram showing the boundary between each component by line segments in a cross-section of a key part of a semiconductor module made in the example. This is a characteristic diagram showing the relationship between the number of cycles and the rate of deterioration of thermal resistance, based on the results of a thermal test using the semiconductor module of the example and the semiconductor module of the comparative example. This shows the results of power cycle tests using the semiconductor module of the example and the semiconductor module of the comparative example, and is a characteristic diagram showing the relationship between the number of cycles and the voltage applied to the semiconductor module. This is a cross-sectional photograph of the main part of the double-sided cooled semiconductor module fabricated in the example.

[0010] The embodiments are described in detail below. However, this disclosure is not limited to the embodiments described below. In the embodiments described below, the components (including elemental steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit this disclosure.

[0011] In this disclosure, the term "process" includes not only processes that are independent of other processes, but also processes that cannot be clearly distinguished from other processes, provided that the purpose of the process is achieved. In this disclosure, numerical ranges indicated using "~" include the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages in this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Also, in a described numerical range, the upper or lower limit of that range may be replaced with the value shown in the example. In this disclosure, each component may contain multiple types of the corresponding substance. If multiple types of the substance corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple types of substances present in the composition, unless otherwise specified. In this disclosure, each component may contain multiple types of particles. If multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.

[0012] <Semiconductor Module> The semiconductor module of this disclosure comprises a semiconductor element and a sealing layer that covers at least the semiconductor element and includes a low-elasticity core layer and a high-elasticity skin layer disposed on the outer surface of the core layer. That is, the semiconductor module of this disclosure has the characteristic that the core layer is less elastic than the skin layer (the skin layer is more elastic than the core layer). Here, the elasticity of the core layer and the skin layer can be evaluated, for example, based on the flexural modulus. In the semiconductor module of this disclosure, if the flexural modulus of the core layer is lower than the flexural modulus of the skin layer, then the core layer can be said to be less elastic than the skin layer. The difference between the flexural modulus of the core layer and the flexural modulus of the skin layer is not particularly limited, but can be 5 to 20 GPa, preferably 5 to 15 GPa, and more preferably 5 to 10 GPa. The flexural modulus is the value calculated by performing a three-point bending measurement based on JIS K7171 (2016). Furthermore, since the modulus of elasticity is temperature-dependent, as a supplementary indicator, Tg is preferably 180 to 220°C on the high-elasticity side and 125 to 215°C on the low-elasticity side, and more preferably 190 to 215°C on the high-elasticity side and 130 to 210°C on the low-elasticity side. The values ​​are those measured under thermomechanical analysis (TMA) with a heating condition of 5°C / min. In the semiconductor module of this disclosure, the high-elasticity skin layer provides excellent heat resistance, and the low-elasticity core layer prevents peeling of the encapsulating layer, resulting in excellent reliability. In the semiconductor module of this disclosure, the encapsulating layer has a multilayer structure of a skin layer and a core layer, achieving both improved heat resistance and improved reliability by preventing peeling of the encapsulating layer.

[0013] In the semiconductor module of this disclosure, the core layer can be protected by a highly elastic skin layer disposed on the outer surface of the encapsulating layer, thereby improving the overall structural strength of the semiconductor module. Furthermore, in the semiconductor module of this disclosure, since the skin layer disposed on the outer surface of the encapsulating layer is highly elastic, it can have excellent weather resistance, chemical resistance, abrasion resistance, etc. against the external environment, thereby improving surface quality.

[0014] Therefore, in the semiconductor module of this disclosure, it is preferable that the skin layer in the encapsulating material layer is arranged on the surface of the semiconductor element and as the outermost layer. In other words, it is preferable that the outermost layer in the semiconductor module of this disclosure is the skin layer. In the semiconductor module of this disclosure, when the skin layer in the encapsulating material layer is the outermost layer, as described above, it becomes possible to improve weather resistance, chemical resistance, abrasion resistance, etc., and to maintain aesthetic beauty for a long period of time.

[0015] Specific examples of the semiconductor module of this disclosure will be described below with reference to the drawings. However, the semiconductor module of this disclosure is not limited to the illustrated configuration. In the illustrated semiconductor module, the arrangement, number, and shape of each component can be arbitrarily changed.

[0016] As a specific example of the semiconductor module of this disclosure, as shown in Figure 1, it comprises a semiconductor element 1 and a sealing material layer 4 that covers at least the semiconductor element 1 and includes a low-elasticity core layer 2 and a high-elasticity skin layer 3 disposed on the outer periphery of the core layer 2. The semiconductor module of this example comprises an insulating heat dissipation circuit board 5 on which the semiconductor element 1 is mounted, a wire 6 (also called a bonding wire) connecting the semiconductor element 1 and the insulating heat dissipation circuit board 5, and a lead frame 7 to which the insulating heat dissipation circuit board 5 on which the semiconductor element 1 is mounted is attached. The semiconductor element 1 is mounted on the insulating heat dissipation circuit board 5 via a solder layer 8. The insulating heat dissipation circuit board 5 has a structure in which a conductive metal plate 9 and a heat sink 10 are laminated with an insulating layer 11 in between. The conductive metal plate 9 of the insulating heat dissipation circuit board 5 is attached to the lead frame 7 via a solder layer 12.

[0017] In the semiconductor module of this example, configured as described above, the highly elastic skin layer 3 provides excellent heat resistance, and the low elasticity core layer 2 prevents delamination of the encapsulating layer 4, resulting in superior reliability. In other words, in the semiconductor module of this example, even in high-temperature environments, if there is a difference in thermal expansion between the insulating heat dissipation circuit board 5, particularly the heat sink 10, and the skin layer 3, the core layer 2 can alleviate the stress, thus preventing delamination of the encapsulating layer 4, breakage of the wires 6, and other problems.

[0018] In the semiconductor module of this example, as shown in Figure 2, the heat sink 10 on the insulating heat dissipation circuit board 5 is exposed on one surface, the end 13 of the lead frame 7 protrudes from the side, and the skin layer 3 of the sealing material layer 4 is exposed on the surfaces other than the heat sink 10 and the end of the lead frame 7. In this way, the semiconductor module of this example can protect the core layer 2 with the highly elastic skin layer 3, thereby improving the overall structural strength of the semiconductor module, and also providing excellent weather resistance, chemical resistance, abrasion resistance, etc. against the external environment, thereby improving surface quality.

[0019] In the semiconductor module of this example, as shown in Figure 1, the semiconductor element 1 is in contact with the skin layer 3 of the encapsulating material layer 4, and the middle portion of the wire 6, excluding the connection portion with the semiconductor element 1, is embedded in the core layer 2 of the encapsulating material layer 4. By having the middle portion of the wire 6 inside the core layer 2 in this way, it is possible to prevent internal stress accumulated in the skin layer 3 from being applied to the middle portion of the wire 6, and thus prevent fracture of the middle portion of the wire 6. Here, the middle portion of the wire 6 is defined as the area between the connection portion of the wire 6 with the semiconductor element 1 and the connection portion of the wire 6 with the insulating heat dissipation circuit board 5, and more preferably the area 0 mm above the wire diameter at the connection portion of the wire 6 with the semiconductor element 1, preferably the area above half the wire diameter at the connection portion of the wire 6 with the semiconductor element 1, and more preferably the area above the connection portion between the insulating heat dissipation circuit board 5 and the wire 6, and it is preferable that the middle portion in this range is embedded in the core layer 2.

[0020] Furthermore, in the semiconductor module of this example, it is particularly preferable that the bent portion of the wire 6 is embedded within the core layer 2. By having the bent portion of the wire 6 within the core layer 2 in this way, it is possible to prevent internal stress accumulated in the skin layer 3 from being applied to the bent portion of the wire 6, thereby avoiding breakage at the bent portion of the wire 6. Here, the bent portion of the wire 6 may be defined as the range from the point with the smallest radius of curvature in the wire 6 connecting the semiconductor element 1 and the insulating heat dissipation circuit board 5 until the wire 6 becomes straight, or it may be defined as a predetermined length range from this center.

[0021] Furthermore, in the semiconductor module of this example, as shown in Figure 1, it is preferable that the thickness of the skin layer 3 disposed on the surface of the semiconductor element 1 is thinner than the thickness of the skin layer 3 disposed on the outermost layer of the semiconductor module. When the thickness of the highly elastic skin layer 3 in contact with the semiconductor element 1 is thin, the internal stress is relieved by the core layer 2 on the skin layer 3, which prevents peeling of the skin layer 3 and breakage of the wire 6 in the semiconductor element 1 portion. Here, the thickness of the skin layer 3 in contact with the semiconductor element 1 is preferably 0.8 or less, more preferably 0.6 or less, even more preferably 0.4 or less, and particularly preferably 0.2 or less, when the thickness of the skin layer 3 exposed to the outside in the sealing material layer 4 is taken as 1.

[0022] Furthermore, in the semiconductor module of this example, as shown in Figure 1, a heat sink 10 is provided on the side of the insulating heat dissipation circuit board 5 on which the semiconductor element 1 is mounted, opposite to the side on which the semiconductor element 1 is mounted. The semiconductor module is arranged so that a cooler (not shown) is in contact with the heat sink 10 under operating conditions. This reduces the effect of heat generation on the semiconductor element 1 and the effect of heat in high-temperature environments. Here, the insulating layer 11 in the insulating heat dissipation circuit board 5 is, for example, silicon nitride (Si ３ N ４ Examples include zirconia-doped alumina (ZDA), alumina, etc. The conductive metal plate 9 and heat sink 10 in the insulating heat dissipation circuit board 5 can be made of metal materials mainly composed of copper, aluminum, gold, silver, brass, etc.

[0023] Specifically, the insulating heat dissipation circuit board 5 is manufactured by bonding and integrating an insulating layer 11, a conductive metal plate 9, and a heat sink 10. At this time, the insulating layer 11, the conductive metal plate 9, and the heat sink 10 are bonded and integrated using either Active Metal Brazing (AMB) or Direct Copper Bonding (DCB). Depending on the bonding method, the insulating heat dissipation circuit board 5 may also be referred to as an AMB substrate or a DCB substrate. In particular, when an AMB substrate is used as the insulating heat dissipation circuit board 5, the AMB substrate has very high thermal conductivity, making it possible to efficiently dissipate the heat generated from the semiconductor element 1. Furthermore, in the AMB method, the use of an active metal strengthens the bond between the insulating layer 11, the conductive metal plate 9, and the heat sink 10, achieving high mechanical strength and thermal stability.

[0024] The semiconductor module of this disclosure may be any of the following: an RFID module, a sensor module, a power module, etc. In particular, it is preferable that the semiconductor element in the semiconductor module of this disclosure is a power semiconductor. In this case, the semiconductor module of this disclosure is a power module equipped with a power semiconductor. A power semiconductor is a semiconductor element that handles large currents, and for example, means a semiconductor element with a rated current of 0.8A or more, 1.0A or more, 1.2A or more, or 1.5A or more. The power semiconductor may be either a diode or a switching device. Examples of switching devices mainly include IGBTs (insulated gate bipolar transistors) and MOSFETs (metal oxide field-effect transistors). Furthermore, the power semiconductor may use silicon carbide as a substrate.

[0025] Furthermore, specific examples of the semiconductor module of this disclosure are not limited to those shown in Figures 1 and 2, but also include those shown in Figure 3, in which the heat sinks 10A and 10B on the insulating heat dissipation circuit board 5 are exposed on both sides. The semiconductor module of this disclosure shown in Figure 3 also comprises a semiconductor element 1 and a sealing material layer 4 that covers at least the semiconductor element 1 and includes a low-elasticity core layer 2 and a high-elasticity skin layer 3 disposed on the outer periphery of the core layer 2. In the semiconductor module of this example, the insulating heat dissipation circuit board 5 on which the semiconductor element 1 is mounted is equipped with heat sinks 10A and 10B, and the semiconductor element 1 etc. are sandwiched between the heat sinks 10A and 10B.

[0026] The semiconductor module shown in Figure 3 has heat sinks 10A and 10B exposed on both sides, resulting in excellent heat dissipation capabilities (double-sided cooling). This allows for a uniform temperature distribution in the region sandwiched between the heat sinks 10A and 10B, enabling stable operation.

[0027] <Method for Manufacturing Semiconductor Modules> The method for manufacturing a semiconductor module according to the present disclosure includes the steps of: placing a semiconductor element in the cavity of a transfer molding apparatus; introducing a molten first resin composition into the cavity; then introducing a molten second resin composition into the cavity; and removing a semiconductor module from the cavity, comprising a sealing layer including a low-elasticity core layer containing the second resin composition and covering at least the semiconductor element, and a highly elastic skin layer containing the first resin composition disposed on the outer circumferential surface of the core layer. According to the method for manufacturing a semiconductor module according to the present disclosure, a semiconductor module with excellent heat resistance due to the highly elastic skin layer and peeling of the sealing layer due to the low-elasticity core layer can be prevented, thereby enabling the manufacture of a highly reliable semiconductor module. In the method for manufacturing a semiconductor module according to the present disclosure, a sealing layer with a multilayer structure of a skin layer and a core layer can be formed in the cavity, enabling the manufacture of a semiconductor module that achieves both improved heat resistance and improved reliability by preventing peeling of the sealing layer.

[0028] Hereinafter, a specific example of the semiconductor module manufacturing method of this disclosure will be described with reference to the drawings. While the main parts of the transfer molding apparatus used in the semiconductor module manufacturing method of this disclosure are shown, the transfer molding apparatus used in the semiconductor module manufacturing method of this disclosure is not limited to the illustrated configuration. In the illustrated transfer molding apparatus, the arrangement, number, and shape of each component can be arbitrarily changed.

[0029] A specific example of the semiconductor module manufacturing method of this disclosure is an embodiment using the transfer molding apparatus shown in Figure 4. Figure 4 shows the main parts of the transfer molding apparatus, including a plunger mechanism for melting tablet-shaped resin material and extruding it into a cavity (not shown). As shown in Figure 4, the transfer molding apparatus comprises a movable mold 20 and a fixed mold 21 located above the movable mold 20. The transfer molding apparatus also comprises a tablet loading section 22 for loading tablet-shaped resin material formed in the movable mold 20, and a plunger 23 for extruding the tablet-shaped resin material loaded in the tablet loading section 22. The transfer molding apparatus in this example has a cavity (not shown) formed by the fixed mold 21 and the movable mold 20. In the plunger mechanism shown in Figure 4, a gate leading to the cavity is formed when the fixed mold 21 is in close proximity to the movable mold 20.

[0030] Although not shown in the figures, the transfer molding apparatus includes a drive device for driving the plunger 23 in the vertical direction, a drive device for driving the fixed mold 21 in the direction of moving toward and away from the movable mold 20, and a control device for controlling these drive devices. Also, although not shown in the figures, the transfer molding apparatus includes a temperature control device for adjusting the temperatures of the movable mold 20 and the fixed mold 21. The inside of the tablet loading section 22 formed in the movable mold 20 can be adjusted to a predetermined temperature by this temperature control device.

[0031] As shown in Figure 4, the transfer molding apparatus configured as described above loads the first tablet 24 and the second tablet 25 into the tablet loading section 22. Here, the first tablet 24 and the second tablet 25 are formed from the first resin composition and the second resin composition described above, respectively. That is, the first tablet 24, formed from the first resin composition, and the second tablet 25, formed from the second resin composition, are loaded into the tablet loading section 22. Although not shown, semiconductor elements are placed in the cavity formed by the movable mold 20 and the fixed mold 21. For example, when manufacturing the semiconductor module shown in Figure 1, an insulating heat dissipation circuit board 5 equipped with semiconductor elements 1 and wires 6, and a lead frame 7 to which the insulating heat dissipation circuit board 5 is attached are placed in the cavity so that the heat sink 10 is in contact with the fixed mold 21. The end portion 13 of the lead frame 7 is located outside the cavity.

[0032] Next, as shown in Figure 5, the temperature inside the tablet loading section 22 is set to a temperature at which the first tablet 24 and the second tablet 25 melt. With the first tablet 24 and the second tablet 25 melted, the plunger 23 is pushed up to sequentially introduce the molten first tablet 24 and the second tablet 25 into the cavity. Here, the first resin composition forming the first tablet 24 has lower fluidity than the second resin composition forming the second tablet 25. Therefore, by introducing the molten first tablet 24 and the second tablet 25 into the cavity in this order, a sealing layer 4 including a low-elasticity core layer 2 and a high-elasticity skin layer 3 arranged on the outer circumferential surface of the core layer 2 can be formed, as shown in Figure 1. In other words, in the semiconductor module manufacturing method of this disclosure, the skin layer containing the first resin composition can be formed on the surface of the semiconductor element 1 and on the inner surface of the cavity. The fluidity of the resin can be defined by the spiral flow value. In this disclosure, the spiral flow value is defined as the flow distance measured as the length of the molded product when the first resin composition and the second resin composition are molded using a spiral flow measurement mold compliant with EMMI-1-66 under the conditions of a mold temperature of 175°C, a molding pressure of 7 MPa, and a curing time of 150 seconds.

[0033] In particular, in the semiconductor module manufacturing method of this disclosure, the thickness of the core layer 2 and the skin layer 3 can be adjusted in accordance with the volume of the first tablet 24 and the second tablet 25 introduced into the cavity. For example, if the first tablet 24 and the second tablet 25 introduced into the cavity have the same volume, ideally, when the thickness of the core layer 2 is 1, the thickness of the skin layer 3 arranged above and below the core layer 2 will be 0.5. Also, if the ratio of the first tablet 24 and the second tablet 25 introduced into the cavity is 1:3 (first tablet 24: second tablet 25), ideally, when the thickness of the core layer 2 is 1, the thickness of the skin layer 3 arranged above and below the core layer 2 will be approximately 0.17. In the transfer molding apparatus of this example, the volume ratio of the first tablet 24 and the second tablet 25 can be appropriately adjusted by the number of tablets loaded into the tablet loading section 22.

[0034] The fluidity of a resin varies depending on the type of resin, but even with resins of the same fluidity, it can be appropriately controlled by the type, shape, and amount of additives such as inorganic fillers. For example, the greater the amount of inorganic filler, the lower the fluidity. Therefore, for example, by making the amount of inorganic filler added to the first resin composition greater than the amount of inorganic filler added to the second resin composition, the fluidity of the first resin composition can be made lower than that of the second resin composition.

[0035] Specifically, for example, if all other conditions (such as the type of resin) are the same, a 1% increase or decrease in the amount of inorganic filler added will increase or decrease the spiral flow value by approximately 10 cm. Note that the fluidity of the resin is not limited to the inorganic filler; it can also be controlled by the type, shape, and amount of plasticizers, surfactants, thickeners, curing agents, pigments, colorants, etc. For plasticizers, fluidity increases with increasing addition to improve the flexibility of the resin. For surfactants, fluidity increases with increasing addition to improve the interaction between the inorganic filler and the resin and improve the dispersibility of the inorganic filler. For thickeners, excessive addition will decrease fluidity because they increase viscosity. For curing agents, fluidity can be reduced because they affect the curing speed and final mechanical properties of the resin. Pigments and colorants, similar to inorganic fillers, affect the fluidity of the resin as their addition amount increases. Furthermore, the fluidity of the resin can be varied through the interactions of these additives.

[0036] Furthermore, with respect to particulate additives such as inorganic fillers added to the resin, the smaller the average particle size, the lower the fluidity. Therefore, for example, by making the average particle size of the inorganic filler added to the first resin composition smaller than the average particle size of the inorganic filler added to the second resin composition, the fluidity of the first resin composition can be made lower than that of the second resin composition. It should be noted that the fluidity of the resin can also be adjusted by the average particle size of pigments or colorants, not just inorganic fillers.

[0037] Specifically, the spiral flow value defined above for the first resin composition is preferably 0.9 times or less, more preferably 0.85 times or less, and even more preferably 0.8 times or less, as a ratio to the spiral flow value measured for the second resin composition. By comparing the spiral flow value of the first resin composition with the spiral flow value of the second resin composition and setting it within the above range, a sealing layer 4 having a multilayer structure of a skin layer 3 containing the first resin composition and a core layer 2 containing the second resin composition can be reliably formed.

[0038] Furthermore, specifically, the spiral flow value defined above for the first resin composition should be lower than the value measured for the second resin composition, but it is preferable that it be 115 cm or less, more preferably 110 cm or less, and even more preferably 105 cm or less. However, the spiral flow value defined above for the first resin composition is preferable to be 90 cm or more, more preferably 95 cm or more, and even more preferably 100 cm or more, in addition to satisfying the condition that it is lower than the value measured for the second resin composition. By setting the spiral flow value of the first resin composition lower than the spiral flow value of the second resin composition and within the above range, a sealing layer 4 having a multilayer structure of a skin layer 3 containing the first resin composition and a core layer 2 containing the second resin composition can be reliably formed.

[0039] Furthermore, more specifically, the spiral flow value defined above for the second resin composition should be higher than the value measured for the first resin composition, but preferably it is 105 cm or more, more preferably 110 cm or more, and even more preferably 115 cm or more. However, the spiral flow value defined above for the second resin composition should satisfy the condition that it is higher than the value measured for the first resin composition, and preferably be 160 cm or less, more preferably 155 cm or less, and even more preferably 150 cm or less. By making the spiral flow value of the second resin composition higher than the spiral flow value of the first resin composition and within the above range, a sealing layer 4 having a multilayer structure of a skin layer 3 containing the first resin composition and a core layer 2 containing the second resin composition can be reliably formed.

[0040] Furthermore, specifically, the difference between the value of the spiral flow defined as above for the first resin composition and the value measured for the second resin composition (the value of the spiral flow of the first resin composition - the value of the spiral flow of the second resin composition) is preferably, for example, 5 cm or more, more preferably 10 cm or more, and still more preferably 15 cm or more. By setting the difference between the value of the spiral flow of the first resin composition and the value of the spiral flow of the second resin composition within the above range, the sealing material layer 4 having a multilayer structure of the skin layer 3 containing the first resin composition and the core layer 2 containing the second resin composition can be surely formed. However, the difference is preferably 60 cm or less, more preferably 50 cm or less, and still more preferably 40 cm or less.

[0041] Next, in the method for manufacturing a semiconductor module of the present disclosure, after the first resin composition and the second resin composition are introduced into the cavity, it is preferable to maintain them at a predetermined temperature and for a predetermined time and then take out the semiconductor module. This step is called so-called post mold cure (PMC), and the curing of the resin constituting the sealing material layer 4 can be accelerated to optimize the physical properties of the material. For example, this step can be set at a temperature of 140°C to 200°C, preferably at a temperature of 150°C to 190°C, and more preferably at a temperature of 145°C to 175°C. Also, this step can be set at 30 minutes to 10 hours, preferably at 1 hour to 8 hours, and more preferably at 3 hours to 6 hours.

[0042] Next, in the method for manufacturing a semiconductor module of the present disclosure, the semiconductor module is taken out from within the cavity. At this time, in the transfer molding apparatus, the fixed mold 21 is separated from the movable mold 20, and the semiconductor module is pushed out from the movable mold 20 by a protruding pin (not shown) to be demolded. As described above, a semiconductor module as shown in FIG. 1 can be manufactured.

[0043] Also, regarding the semiconductor module shown in FIG. 3, the manufacturing method of the semiconductor module shown in FIG. 1 described above can be applied. In particular, when manufacturing the semiconductor module shown in FIG. 3, an insulating heat dissipation circuit board 5 including a semiconductor element 1 and a wire 6 and a lead frame 7 to which the insulating heat dissipation circuit board 5 is attached are disposed in a cavity formed by a fixed mold 21 and a movable mold 20 so that the heat dissipation plate 10A contacts the fixed mold 21. Note that thereby, the heat dissipation plate 10B in the insulating heat dissipation circuit board 5 will be located on the movable mold 20 side. In this state, the semiconductor module shown in FIG. 3 can be manufactured by the transfer molding described above.

[0044] At this time, it is preferable to attach a so-called release film to the surface of the cavity in the movable mold 20. That is, in this case, the heat dissipation plate 10B in the insulating heat dissipation circuit board 5 having the heat dissipation plate 10B is brought into contact with the release film attached to the inner surface of the cavity. The release film is not particularly limited, and those used in conventional film-assisted molding (FAM: Film Assisted Molding) can be used. As a method of attaching the release film to the movable mold 20, a vacuum adsorption method can be applied. Also in this case, the movable mold 20 is separated from the fixed mold 21, and the semiconductor module is pushed out from the movable mold 20 by a protruding pin (not shown) to be脱模. By using the release film, it is possible to prevent the skin layer 3 from wrapping around the surface of the heat dissipation plate 10B that is exposed to the outside. Further, by using the release film, it is possible to prevent the heat dissipation plate 10B from being damaged when the semiconductor module is脱模 from the movable mold 20 by the protruding pin.

[0045] Furthermore, when manufacturing the semiconductor module shown in Figure 3, it is preferable to increase the area of ​​the opening through which the molten first tablet 24 and second tablet 25 are introduced into the cavity. Specifically, as shown in Figure 6, molten resin is introduced into the cavity formed by the movable mold 20 and the fixed mold 21 through an opening (width W, height H) formed by the heat sink 10A and heat sink 10B and the pillar 14 connecting these heat sinks 10A and heat sink 10B. More specifically, the area of ​​the opening calculated from the width W and height H is, for example, 66 mm². ２ Preferably, it should be 100 mm or more. ２ It is more preferable to have a minimum of 150 mm. ２ It is even more preferable to have a minimum of 200 mm. ２ It is even more preferable to do the above.

[0046] <Semiconductor Devices> The semiconductor devices of this disclosure are devices equipped with the semiconductor modules of this disclosure described above. In particular, the semiconductor devices of this disclosure are preferably semiconductor devices having a power module as a specific example of the semiconductor modules of this disclosure. Examples of such semiconductor devices include electric vehicles, renewable energy systems, industrial equipment, etc. Other examples of semiconductor devices include smartphones, computers, televisions, home appliances, etc.

[0047] As described above, the semiconductor device of this disclosure has excellent heat resistance due to its highly elastic skin layer and prevents peeling of the encapsulating layer due to its low-elasticity core layer, resulting in a highly reliable semiconductor module. In other words, as described above, the semiconductor device of this disclosure has a semiconductor module that achieves both improved heat resistance by using a multilayer structure of a skin layer and a core layer for the encapsulating layer, and improved reliability by preventing peeling of the encapsulating layer. Therefore, the semiconductor device of this disclosure has extremely high reliability in high-temperature environments.

[0048] Furthermore, the semiconductor device of this disclosure includes a semiconductor module in which the core layer is protected by a highly elastic skin layer disposed on the outer surface of the encapsulating material layer. As a result, the structural strength of the semiconductor module is improved, and stable operation can be achieved. In addition, because the skin layer disposed on the outer surface of the encapsulating material layer in the semiconductor module of this disclosure is highly elastic, it can have excellent weather resistance, chemical resistance, and abrasion resistance to the external environment, improving surface quality and achieving a longer lifespan.

[0049] <Resin Composition for Sealing Material> Hereinafter, the first resin composition constituting the skin layer and the second resin composition constituting the core layer will be collectively referred to as the resin composition for sealing material. The resin composition for sealing material according to this disclosure contains a thermosetting resin, a curing agent, and an inorganic filler, and may optionally contain various additives such as curing accelerators, colorants, coupling agents, ion exchangers, mold release agents, flame retardants, and stress relaxants. In addition to these additives, the resin composition for sealing material may optionally contain various additives such as ultraviolet absorbers that are well known in the art.

[0050] (Thermosetting resins) The types of thermosetting resins are not particularly limited and include epoxy resins, phenolic resins, thiol resins, urea resins, melamine resins, urethane resins, silicone resins, maleimide resins, unsaturated polyester resins, etc. In this disclosure, resins that exhibit both thermoplastic and thermosetting properties, such as acrylic resins containing epoxy groups, are included in "thermosetting resins." Thermosetting resins may be solid or liquid at room temperature and pressure (for example, 25°C and atmospheric pressure), but are preferably solid. Thermosetting resins may be used individually or in combination of two or more types.

[0051] The thermosetting resin preferably contains an epoxy resin. The type of epoxy resin is not particularly limited as long as it has two or more epoxy groups in one molecule. Specifically, these include: novolac-type epoxy resins (phenol novolac-type epoxy resins, orthocresol novolac-type epoxy resins, etc.) obtained by condensing or co-condensing a novolac resin obtained by condensing or co-condensing a novolac resin obtained by phenol compounds selected from the group consisting of phenol compounds such as phenol, cresol, xylenol, resorcinol, catechol, bisphenol A, bisphenol F, and naphthol compounds such as α-naphthol, β-naphthol, and dihydroxynaphthalene under an acidic catalyst; triphenylmethane-type epoxy resins obtained by condensing or co-condensing a triphenylmethane-type phenol resin obtained by condensing or co-condensing the above phenol compound with an aromatic aldehyde compound such as benzaldehyde and salicylaldehyde under an acidic catalyst; and co-phenylmethane-type epoxy resins obtained by epoxidizing a novolac resin obtained by co-condensing the above phenol compound and naphthol compound with an aldehyde compound under an acidic catalyst. Polymerized epoxy resins; diphenylmethane-type epoxy resins, which are diglycidyl ethers of bisphenol A, bisphenol F, etc.; biphenylaralkyl-type epoxy resins or biphenyl-type epoxy resins, which are diglycidyl ethers of alkyl-substituted or unsubstituted biphenols; stilbene-type epoxy resins, which are diglycidyl ethers of stilbene-based phenol compounds; sulfur atom-containing epoxy resins, which are diglycidyl ethers of bisphenol S, etc.; epoxy resins, which are glycidyl ethers of alcohols such as butanediol, polyethylene glycol, and polypropylene glycol; glycidyl ester-type epoxy resins, which are glycidyl esters of polycarboxylic acid compounds such as phthalic acid, isophthalic acid, and tetrahydrophthalic acid; glycidylamine-type epoxy resins, in which the active hydrogen bonded to the nitrogen atom of aniline, diaminodiphenylmethane, isocyanuric acid, etc., is substituted with a glycidyl group; dicyclopentadiene-type epoxy resins, which are epoxidized from a co-condensation resin of dicyclopentadiene and a phenol compound;Alicyclic epoxy resins such as vinylcyclohexene diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and 2-(3,4-epoxy)cyclohexyl-5,5-spiro(3,4-epoxy)cyclohexane-m-dioxane, in which the olefin bonds within the molecule are epoxidized; paraxylylene-modified epoxy resins, which are glycidyl ethers of paraxylylene-modified phenol resins; metaxylylene-modified epoxy resins, which are glycidyl ethers of metaxylylene-modified phenol resins; terpene-modified epoxy resins, which are glycidyl ethers of terpene-modified phenol resins; and dicyclopentadiene-modified epoxy resins, which are glycidyl ethers of dicyclopentadiene-modified phenol resins. Examples of epoxy resins include cyclopentadiene-modified epoxy resins, which are glycidyl ethers of cyclopentadiene-modified phenolic resins; polycyclic aromatic ring-modified epoxy resins, which are glycidyl ethers of polycyclic aromatic ring-modified phenolic resins; naphthalene-type epoxy resins, which are glycidyl ethers of naphthalene ring-containing phenolic resins; halogenated phenol novolac-type epoxy resins; hydroquinone-type epoxy resins; trimethylolpropane-type epoxy resins; linear aliphatic epoxy resins obtained by oxidizing olefin bonds with peracids such as peracetic acid; aralkyl-type epoxy resins, which are epoxidized aralkyl-type phenolic resins such as phenol aralkyl resins and naphthol aralkyl resins; and crystalline thioether-type crystalline epoxy resins containing thioether groups. Furthermore, epoxides of silicone resins and aminophenol-type epoxy resins, which are glycidyl ethers of aminophenols, can also be cited as epoxy resins. These epoxy resins may be used individually or in combination of two or more types.

[0052] Among the epoxy resins mentioned above, epoxy resins selected from the group consisting of biphenylaralkyl epoxy resins, thioether-type crystalline epoxy resins, biphenyl-type epoxy resins, stilbene-type epoxy resins, diphenylmethane-type epoxy resins, sulfur atom-containing epoxy resins, novolac-type epoxy resins, dicyclopentadiene-type epoxy resins, triphenylmethane-type epoxy resins, copolymer-type epoxy resins, and aralkyl-type epoxy resins (these are referred to as "specific epoxy resins") from the viewpoint of balancing heat resistance and fluidity. Specific epoxy resins may be used individually or in combination of two or more types.

[0053] (Curing agent) The type of curing agent is not particularly limited, as long as it is a compound that undergoes a curing reaction with the thermosetting resin used in combination. For example, curing agents used in combination with epoxy resins include phenolic curing agents, amine curing agents, acid anhydride curing agents, polymercaptan curing agents, polyaminoamide curing agents, isocyanate curing agents, and blocked isocyanate curing agents. One type of curing agent may be used alone, or two or more types may be used in combination. The curing agent may be solid or liquid at room temperature and pressure (for example, 25°C and atmospheric pressure), but it is preferable that it be solid. When the thermosetting resin is an epoxy resin, a phenolic curing agent or an amine curing agent is preferred from the viewpoint of heat resistance.

[0054] Examples of phenolic curing agents include phenolic resins and polyhydric phenolic compounds having two or more phenolic hydroxyl groups in one molecule. Specifically, these include polyhydric phenolic compounds such as resorcinol, catechol, bisphenol A, bisphenol F, and substituted or unsubstituted biphenols; novolac-type phenolic resins obtained by condensing or co-condensing at least one phenolic compound selected from the group consisting of phenolic compounds such as phenol, cresol, xylenol, resorcinol, catechol, bisphenol A, bisphenol F, phenylphenol, aminophenol, and naphthol compounds such as α-naphthol, β-naphthol, and dihydroxynaphthalene with an aldehyde compound such as formaldehyde, acetaldehyde, or propionaldehyde under an acidic catalyst; and phenolic aralkyl resins and naphthol aralkyl resins synthesized from the above phenolic compounds with dimethoxyparaxylene, bis(methoxymethyl)biphenyl, etc. Examples include aralkyl-type phenolic resins such as alkyl resins; paraxylylene and / or metaxylylene-modified phenolic resins; paraxylene-modified phenolic resins; melamine-modified phenolic resins; terpene-modified phenolic resins; dicyclopentadiene-type phenolic resins and dicyclopentadiene-type naphthol resins synthesized by copolymerization of the above phenolic compounds with dicyclopentadiene; cyclopentadiene-modified phenolic resins; polycyclic aromatic ring-modified phenolic resins; biphenyl-type phenolic resins; biphenylaralkyl-type phenolic resins; triphenylmethane-type phenolic resins obtained by condensation or co-condensation of the above phenolic compounds with aromatic aldehyde compounds such as benzaldehyde and salicylaldehyde under an acidic catalyst; and phenolic resins obtained by copolymerizing two or more of these. Furthermore, monovalent phenolic compounds having one phenolic hydroxyl group in one molecule can also be used as phenolic curing agents. These phenolic curing agents may be used individually or in combination of two or more types.

[0055] Among phenolic curing agents, at least one selected from the group consisting of paraxylene-modified phenolic resin, biphenylaralkyl-type phenolic resin, aralkyl-type phenolic resin, dicyclopentadiene-type phenolic resin, triphenylmethane-type phenolic resin, copolymerized phenolic resin of triphenylmethane-type phenolic resin and aralkyl-type phenolic resin, and novolac-type phenolic resin (these are referred to as "specific phenolic curing agents") is preferred from the viewpoint of heat resistance. Specific phenolic curing agents may be used individually or in combination of two or more types.

[0056] (Curing accelerator) The type of curing accelerator is not particularly limited and can be selected according to the type of curable resin, the desired properties of the thermosetting resin, etc.

[0057] From the viewpoint of curability and fluidity, it is preferable that the curing accelerator contains a phosphonium compound. Specifically, phosphonium compounds include triphenylphosphine, diphenyl(p-tolyl)phosphine, tris(alkylphenyl)phosphine, tris(alkoxyphenyl)phosphine, tris(alkyl・alkoxyphenyl)phosphine, tris(dialkylphenyl)phosphine, tris(trialkylphenyl)phosphine, tris(tetraalkylphenyl)phosphine, tris(dialkoxyphenyl)phosphine, tris(trialkoxyphenyl)phosphine, and tris(tetraalkoxyphenyl)phosphine. It has intramolecular polarization formed by adding π-bonded compounds such as quinone compounds like maleic anhydride, 1,4-benzoquinone, 2,5-tholquinone, 1,4-naphthoquinone, 2,3-dimethylbenzoquinone, 2,6-dimethylbenzoquinone, 2,3-dimethoxy-5-methyl-1,4-benzoquinone, 2,3-dimethoxy-1,4-benzoquinone, phenyl-1,4-benzoquinone, and diazophenylmethane to tertiary phosphines such as sphing, trialkylphosphines, dialkylarylphosphines, and alkyldiarylphosphines. Compounds that do this; tertiary phosphine and 4-bromophenol, 3-bromophenol, 2-bromophenol, 4-chlorophenol, 3-chlorophenol, 2-chlorophenol, 4-iodidephenol, 3-iodidephenol, 2-iodidephenol, 4-bromo-2-methylphenol, 4-bromo-3-methylphenol, 4-bromo-2,6-dimethylphenol, 4-bromo-3,5-dimethylphenol, 4-bromo-2,6-di-tert-butylphenol, 4-chloro-1-naphthol, 1-bromo-2-na Examples include compounds having intramolecular polarization obtained by reacting halogenated phenol compounds such as phthol, 6-bromo-2-naphthol, and 4-bromo-4'-hydroxybiphenyl with a dehalogenation step; salts of tetrasubstituted phosphoniums such as tetraphenylphosphonium and tetrasubstituted borates such as tetra-p-tolylborate; salts of tetrasubstituted phosphoniums with anions obtained by removing a proton from a phenol compound; and salts of tetrasubstituted phosphoniums with anions obtained by removing a proton from a carboxylic acid compound.

[0058] The thermosetting resin composition may contain curing accelerators other than phosphonium compounds. Other curing accelerators besides phosphonium compounds include, specifically, diazabicycloalkenes such as 1,5-diazabicyclo[4.3.0]nonene-5 (DBN) and 1,8-diazabicyclo[5.4.0]undecene-7 (DBU), cyclic amidine compounds such as 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, and 2-heptadecylimidazole; derivatives of the cyclic amidine compounds; phenol novolac salts of the cyclic amidine compounds or their derivatives; and quinone compounds such as maleic anhydride, 1,4-benzoquinone, 2,5-toluquinone, 1,4-naphthoquinone, 2,3-dimethylbenzoquinone, 2,6-dimethylbenzoquinone, 2,3-dimethoxy-5-methyl-1,4-benzoquinone, 2,3-dimethoxy-1,4-benzoquinone, and phenyl-1,4-benzoquinone. Examples include compounds having intramolecular polarization formed by adding compounds with π bonds, such as diazophenylmethane; cyclic amidinium compounds such as tetraphenylborate salt of DBU, tetraphenylborate salt of DBN, tetraphenylborate salt of 2-ethyl-4-methylimidazole, and tetraphenylborate salt of N-methylmorpholine; tertiary amine compounds such as pyridine, triethylamine, triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, and tris(dimethylaminomethyl)phenol; derivatives of the aforementioned tertiary amine compounds; and ammonium salt compounds such as tetra-n-butylammonium acetate, tetra-n-butylammonium phosphate, tetraethylammonium acetate, tetra-n-hexylammonium benzoate, and tetrapropylammonium hydroxide.

[0059] (Inorganic Fillers) The type of inorganic filler is not particularly limited. Specifically, examples include silica such as spherical silica and crystalline silica, glass, alumina, calcium carbonate, zirconium silicate, calcium silicate, silicon nitride, aluminum nitride, boron nitride, beryllia, zirconia, zircon, fossterite, steatite, spinel, mullite, titania, talc, clay, and mica. Inorganic fillers with flame retardant properties may also be used. Examples of inorganic fillers with flame retardant properties include aluminum hydroxide, magnesium hydroxide, composite metal hydroxides such as magnesium and zinc hydroxide, and zinc borate. Among these, spherical silica is preferred from the viewpoint of reducing the coefficient of thermal expansion, and alumina is preferred from the viewpoint of high thermal conductivity. One type of inorganic filler may be used alone, or two or more types may be used in combination. Examples of inorganic filler states include powder, beads formed from spherical powder, and fibers.

[0060] The inorganic filler content is not particularly limited. From the viewpoint of fluidity and strength, it is preferably 30% to 90% by volume of the total resin composition for the encapsulant, more preferably 35% to 85% by volume, and even more preferably 40% to 80% by volume. When the inorganic filler content is 30% by volume or more of the resin composition for the encapsulant, the properties of the cured product, such as the coefficient of thermal expansion, thermal conductivity, and elastic modulus, tend to improve further. When the inorganic filler content is 90% by volume or less of the total resin composition for the encapsulant, the increase in viscosity of the resin composition for the encapsulant is suppressed, fluidity improves further, and moldability tends to be better.

[0061] The average particle size of the inorganic filler is not particularly limited. For example, the volume average particle size is preferably 0.2 μm to 50 μm, and more preferably 0.5 μm to 30 μm. When the volume average particle size is 0.2 μm or more, the increase in viscosity of the thermosetting resin composition tends to be further suppressed. When the volume average particle size is 50 μm or less, the ability to fill narrow gaps tends to be further improved. The volume average particle size of the inorganic filler refers to the value measured as the volume average particle size (D50) using a laser diffraction scattering particle size distribution analyzer.

[0062] The volume-average particle size of inorganic fillers in cured materials can be measured by known methods. For example, inorganic fillers can be extracted from the cured material using an organic solvent, nitric acid, aqua regia, etc., and thoroughly dispersed using an ultrasonic disperser or the like to prepare a dispersion. Using this dispersion, the volume-average particle size of the inorganic fillers can be measured from the volume-based particle size distribution measured by a laser diffraction scattering particle size distribution analyzer. Alternatively, the volume-average particle size of the inorganic fillers can be measured from the volume-based particle size distribution obtained by embedding the cured material in a transparent epoxy resin or the like, polishing the resulting cross-section, and observing it with a scanning electron microscope. Furthermore, it can also be measured by continuously observing the two-dimensional cross-section of the cured material using a FIB (Focused Ion Beam SEM) or the like and performing three-dimensional structural analysis.

[0063] From the viewpoint of the fluidity of the resin composition for sealing materials, the particle shape of the inorganic filler is preferably spherical rather than angular, and the particle size distribution of the inorganic filler is preferably widely distributed.

[0064] (Coupling Agent) If the resin composition for sealing materials contains an inorganic filler, a coupling agent may be included to improve the adhesion between the resin component and the inorganic filler. The type of coupling agent is not particularly limited, and known coupling agents can be used. Examples of coupling agents include silane coupling agents and titanium coupling agents. One type of coupling agent may be used alone, or two or more types may be used in combination.

[0065] Examples of silane coupling agents include epoxy-based silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and glycidoxyoctyltrimethoxysilane; amine-based silane coupling agents such as 3-aminopropyltriethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane, 3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane; mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane; and 3-ureidopropyltriethoxysilane, octenyltrimethoxysilane, and methacryloxyoctyltrimethoxysilane.

[0066] Examples of titanium coupling agents include isopropyl triisostearoyl titanate, isopropyl tris(dioctyl pyrophosphate) titanate, isopropyl tri(N-aminoethyl-aminoethyl) titanate, tetraoctyl bis(ditridecyl phosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl)bis(ditridecyl phosphite) titanate, bis(dioctyl pyrophosphate) oxyacetate titanate, bis(dioctyl pyrophosphate) ethylene titanate, isopropyl trioctanoyl titanate, isopropyl dimethacrylate isostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl isostearoyl diacrylic titanate, isopropyl tri(dioctyl phosphate) titanate, isopropyl tricumylphenyl titanate, and tetraisopropyl bis(dioctyl phosphite) titanate.

[0067] When the resin composition for sealing materials contains a coupling agent, the content of the coupling agent is preferably 0.001 to 10 parts by mass, more preferably 0.01 to 8 parts by mass, and even more preferably 0.05 to 5 parts by mass, per 100 parts by mass of the inorganic filler, from the viewpoint of adhesion at the interface between the thermosetting resin and the inorganic filler.

[0068] (Ion Exchanger) The resin composition for encapsulating materials may contain an ion exchanger. In particular, it is preferable to include an ion exchanger from the viewpoint of improving the moisture resistance and high-temperature storage characteristics of electronic components. The ion exchanger is not particularly limited, and conventionally known ones can be used. Specifically, examples include hydrotalcite compounds and hydrated oxides of at least one element selected from the group consisting of magnesium, aluminum, titanium, zirconium, and bismuth. One type of ion exchanger may be used alone, or two or more types may be used in combination.

[0069] If the resin composition for sealing materials contains an ion exchanger, the amount is not particularly limited as long as it is sufficient to capture ions such as halogen ions. For example, it is preferably 0.1 to 30 parts by mass, and more preferably 1 to 15 parts by mass, per 100 parts by mass of the resin component.

[0070] (Release Agent) The resin composition for sealing materials may contain a release agent from the viewpoint of obtaining good release properties from the mold during molding. The release agent is not particularly limited, and conventionally known ones can be used. Specifically, examples include carnauba wax, higher fatty acids such as montanic acid and stearic acid, higher fatty acid metal salts, ester waxes such as montanic acid esters, and polyolefin waxes such as polyethylene oxide and non-oxidized polyethylene. One type of release agent may be used alone, or two or more types may be used in combination.

[0071] When the resin composition for sealing materials contains a release agent, the amount is preferably 0.01 to 15 parts by mass, and more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the resin component. When the amount of release agent is 0.01 parts by mass or more per 100 parts by mass of the resin component, sufficient release properties tend to be obtained. When the amount of release agent is 15 parts by mass or less per 100 parts by mass of the resin component, better adhesion tends to be obtained.

[0072] (Flame retardant) The resin composition for sealing materials may contain a flame retardant. The flame retardant is not particularly limited, and conventionally known ones can be used. Specifically, examples include organic or inorganic compounds containing halogen atoms, antimony atoms, nitrogen atoms, or phosphorus atoms, metal hydroxides, etc. One type of flame retardant may be used alone, or two or more types may be used in combination.

[0073] If the resin composition for sealing material contains a flame retardant, the amount is not particularly limited as long as it is sufficient to obtain the desired flame retardant effect. For example, it is preferably 1 to 300 parts by mass, and more preferably 2 to 150 parts by mass, per 100 parts by mass of the resin component.

[0074] (Colorants) The resin composition for sealing materials may further contain colorants. Examples of known colorants include carbon black, organic dyes, organic pigments, titanium dioxide, red lead, and red iron oxide. The amount of colorant can be appropriately selected depending on the purpose. One type of colorant may be used alone, or two or more types may be used in combination.

[0075] (Stress Relief Agents) The resin composition for sealing materials may contain stress relief agents such as silicone oil and silicone rubber particles. Including stress relief agents can further reduce warping deformation and the occurrence of package cracks in semiconductor packages. Examples of stress relief agents include commonly used and known stress relief agents (flexible agents). Specifically, these include thermoplastic elastomers such as silicone-based, styrene-based, olefin-based, urethane-based, polyester-based, polyether-based, polyamide-based, and polybutadiene-based; rubber particles such as NR (natural rubber), NBR (acrylonitrile-butadiene rubber), acrylic rubber, urethane rubber, and silicone powder; methyl methacrylate-styrene-butadiene copolymer (MBS), methyl methacrylate-silicone copolymer, methyl methacrylate-butyl acrylate copolymer, indene-containing copolymers of indenes such as indene and alkylindene and styrenes such as styrene and alkylstyrene and phenols, with aromatic olefins such as coumarone as other constituent monomers; and epoxy-modified silicone resins. One type of stress relief agent may be used alone, or two or more types may be used in combination.

[0076] (Physical Properties of Resin Compositions for Sealing Materials) -Glass Transition Temperature (Tg)- For the glass transition temperatures of the first and second resin compositions, it is preferable that the first resin composition has a higher glass transition temperature than the second resin composition. The glass transition temperature is determined by thermomechanical analysis (TMA) under a heating condition of 5°C / min. The glass transition temperature of the first resin composition can be 180°C to 220°C, preferably 190°C to 215°C, and more preferably 195°C to 210°C, satisfying the condition that it is higher than the glass transition temperature of the second resin composition. The glass transition temperature of the second resin composition can be 125°C to 215°C, preferably 130°C to 210°C, and more preferably 135°C to 205°C, satisfying the condition that it is lower than the glass transition temperature of the first resin composition. By setting the glass transition temperatures of the first and second resin compositions within this range, it is possible to reliably form a sealing layer having a multilayer structure consisting of a skin layer containing the first resin composition and a core layer containing the second resin composition.

[0077] -Gelation Time- The gelation times of the first and second resin compositions are preferably about the same. The gelation time is measured at 175°C in accordance with JIS K 6910. The difference between the gelation time of the first resin composition and the gelation time of the second resin composition can be within 8 seconds, preferably within 6 seconds, and more preferably within 4 seconds. By setting the difference between the gelation times of the first and second resin compositions within this range, a sealing layer having a multilayer structure of a skin layer containing the first resin composition and a core layer containing the second resin composition can be reliably formed. Furthermore, the gelation times of the first and second resin compositions can be 40 to 80 seconds, preferably 50 to 70 seconds, and more preferably 55 to 60 seconds. By setting the gelation times of the first resin composition and the second resin composition within this range, a sealing layer having a multilayer structure consisting of a skin layer containing the first resin composition and a core layer containing the second resin composition can be reliably formed.

[0078] -Coefficient of Thermal Expansion- For the thermal expansion coefficients of the first and second resin compositions, it is preferable that the thermal expansion coefficient α1, measured under the condition that the temperature range can be approximated by a straight line at a temperature lower than the inflection point, and the thermal expansion coefficient α2, measured under the condition that the temperature range can be approximated by a straight line at a temperature higher than the inflection point, are both higher for the first resin composition than for the second resin composition. Both thermal expansion coefficients α1 and α2 were measured using thermomechanical analysis (TMA) at a heating rate of 3°C / min and a measurement temperature range of 0 to 250°C, and the slope of a straight line from 0°C to 30°C was used.

[0079] The thermal expansion coefficient α1 of the first resin composition can be 10 ppm / °C to 20 ppm / °C, preferably 12 ppm / °C to 18 ppm / °C, and more preferably 12 ppm / °C to 15 ppm / °C. The thermal expansion coefficient α2 of the first resin composition can be 45 ppm / °C to 75 ppm / °C, preferably 50 ppm / °C to 70 ppm / °C, and more preferably 55 ppm / °C to 65 ppm / °C. The thermal expansion coefficient α1 of the second resin composition can be 5 ppm / °C to 15 ppm / °C, preferably 7 ppm / °C to 12 ppm / °C, and more preferably 8 ppm / °C to 10 ppm / °C. Furthermore, the thermal expansion coefficient α2 of the second resin composition can be 25 ppm / °C to 55 ppm / °C, preferably 30 ppm / °C to 50 ppm / °C, and more preferably 35 ppm / °C to 45 ppm / °C. By setting the thermal expansion coefficients (α1 and α2) of the first and second resin compositions within this range, a sealing layer having a multilayer structure of a skin layer containing the first resin composition and a core layer containing the second resin composition can be reliably formed.

[0080] - Flexural Modulus - For the flexural modulus of the first and second resin compositions, it is preferable that the first resin composition has a lower flexural modulus than the second resin composition, both at room temperature (25°C) and under high-temperature conditions (260°C). These flexural moduli are values ​​calculated by performing a three-point bending measurement based on JIS K7171 (2016).

[0081] The flexural modulus of the first resin composition at room temperature (25°C) can be 10 GPa to 40 GPa, preferably 15 GPa to 35 GPa, and more preferably 20 GPa to 30 GPa. The flexural modulus of the first resin composition at 260°C can be 1.0 GPa to 5.0 GPa, preferably 1.2 GPa to 3.0 GPa, and more preferably 1.5 GPa to 2.5 GPa. The flexural modulus of the second resin composition at room temperature (25°C) can be 5 GPa to 30 GPa, preferably 10 GPa to 25 GPa, and more preferably 15 GPa to 20 GPa. The flexural modulus of the second resin composition at 260°C can be 1.0 GPa to 4.0 GPa, preferably 1.2 GPa to 2.5 GPa, and more preferably 1.5 GPa to 2.0 GPa.

[0082] The embodiments of this disclosure will be described in detail below with reference to examples, but the technical scope of this disclosure is not limited to these examples.

[0083] [First and Second Resin Compositions] The first and second resin compositions were prepared by mixing each component to achieve the composition shown in Table 1 and performing roll kneading under the conditions of a kneading temperature of 70 to 100°C and a kneading time of 5 to 10 minutes. Note that the values ​​in Table 1 are in parts by mass, except for the filler volume % values ​​for the inorganic filler.

[0084]

[0085] [Evaluation of Resin Compositions] Test pieces were prepared using the first and second resin compositions having the above compositions, and their characteristics were evaluated for each of the following items. The resin composition temperature (TMC temperature, °C), mold temperature (up / down, °C), molding speed (mm / s), molding pressure (MPa), and post-mold cure (PMC) conditions were set as shown in Table 2, and test pieces were prepared from the first and second resin compositions, respectively.

[0086]

[0087] - Spiral flow: The spiral flow value was defined as the flow distance measured as the length of the molded product when the first and second resin compositions were molded using a spiral flow measurement mold compliant with EMMI-1-66 under the conditions of a mold temperature of 175°C, a molding pressure of 7 MPa, and a curing time of 150 seconds.

[0088] - Glass transition temperature (Tg): The glass transition temperature was measured using thermomechanical analysis (TMA) with a heating rate of 5°C / min using a TA4000SA manufactured by TA Instruments Inc.

[0089] - Gelation Time: The gelation time at 175°C was measured in accordance with JIS K 6910. Specifically, 0.5 g of the resin composition was dropped onto a hot plate at 175°C and stirred with a spatula to prevent it from spreading too much. After dropping, the viscosity of the curable composition increased, and the time until the resin composition was cut without stringing when the spatula was lifted was defined as the gelation time.

[0090] - Thermal expansion coefficient: The resin composition was heated and molded into a cylindrical shape with a diameter of 8 mm and a length of 20 mm at 150°C for 2 hours. The cured product was then measured using TMA (thermomechanical analysis, TA4000SA, TA Instruments Co., Ltd.) at a heating rate of 3°C / min and a measurement temperature range of 0 to 250°C. The slope of the straight line from 0°C to 30°C was defined as the thermal expansion coefficient. The thermal expansion coefficient measured under the condition that the temperature range approximated by a straight line at a lower temperature than the inflection point is called α1, and the thermal expansion coefficient measured under the condition that the temperature range approximated by a straight line at a higher temperature than the inflection point is called α2.

[0091] ・Flexural modulus (room temperature 25°C, 260°C) The flexural modulus (GPa) was determined at room temperature (25°C) and under high-temperature conditions (260°C). The flexural modulus of the test specimen was calculated by performing a three-point bending measurement based on JIS K7171 (2016).

[0092] The rubber strength was evaluated at temperatures of 23.5°C, 70°C, 150°C, or 200°C. After maintaining each temperature in a constant temperature bath for 3 hours, the rubber strength was measured using a hardness tester: Type D (measured on the resin side) (N=4).

[0093] Table 3 shows the results of measurements for the glass transition temperature, spiral flow, gelation time, flexural modulus, and thermal expansion coefficient. Figure 7 shows the results of measurements for the rubber strength.

[0094]

[0095] From these results, it was found that the first resin composition had low fluidity, a high Tg, and high elasticity, while the second resin composition had high fluidity and low elasticity.

[0096] [Two-color molding] A molded body having a multilayer structure of a skin layer containing a first resin composition and a core layer containing a second resin composition was manufactured as follows. First, tablets were prepared for the first resin composition and the second resin composition, respectively. The tablets of the first resin composition and the tablets of the second resin composition were set in a transfer molding apparatus in a volume ratio of 1:1 to produce a molded body of 6 cm × 6 cm × 0.6 cm (length × width × height). The mold temperature was set to 200°C, the molding speed to 2 mm / s, the molding pressure to 14 MPa, and the post-mold cure (PMC) conditions to 150°C for 5 hours.

[0097] Figure 8 shows cross-sectional photographs of the obtained molded body divided into three sections parallel to the resin flow direction, and Figure 9 shows a schematic diagram indicating the boundary between the first resin composition and the second resin composition with line segments for the cross-sections shown in Figure 8. In addition, the thickness of the first resin composition layer (skin layer) and the second resin composition layer (core layer) was measured at three locations in the longitudinal direction of each cross-section shown in Figure 9 (1-1 to 9-3 in Figure 9). The thickness of each part is shown in Table 4.

[0098]

[0099] The results shown in Figures 8 and 9 and Table 4 clearly demonstrate that a encapsulating layer having a multilayer structure consisting of a skin layer containing the first resin composition and a core layer containing the second resin composition can be formed using the first and second resin compositions.

[0100] [Semiconductor Module] Next, the semiconductor module of the example was fabricated using the first resin composition and the second resin composition. In this example, Cu / Si ３ N ４An AMB substrate with thickness / Cu = t0.3 / t0.32 / t0.3, an IGBT (Si-IGBT, insulated gate bipolar transistor) with a silicon substrate, and an aluminum wire connecting the AMB substrate and the Si-IGBT were mounted on a lead frame, and a sealing layer including a skin layer and a core layer was fabricated using a transfer molding apparatus with a first resin composition and a second resin composition. The mold temperature in the transfer molding apparatus was set to 200°C, the molding speed to 2 mm / s, the molding pressure to 14 MPa, and the post-mold cure (PMC) conditions to 175°C for 5 hours.

[0101] Figure 10 shows a schematic diagram illustrating the boundaries of each component with line segments in a photograph of a cross-section of the fabricated semiconductor module. The schematic diagram in Figure 10 shows a encapsulating layer having a multilayer structure of a core layer 2 and a skin layer 3. As shown in Figure 10, the semiconductor element 1 (Si-IGBT) and the insulating heat dissipation circuit board 5 (AMB substrate) are in contact with the skin layer 3, and the intermediate portion of the wire 6, excluding the connection portion with the semiconductor element 1, particularly the bent portion of the wire 6, is embedded within the core layer 2.

[0102] Furthermore, in order to compare it with the semiconductor module of the example, a comparative semiconductor module was fabricated in the same manner as the semiconductor module of the example, except that the encapsulating layer was made using the first resin composition instead of the second resin composition.

[0103] [Thermal Test] Thermal tests were performed on the semiconductor modules of the example and the comparative example. The temperature cycling conditions for the thermal test were a maximum temperature of 150°C and a minimum temperature of -40°C (ΔTj = 190°C), a transition time of 11 minutes, and a holding time of 10 minutes. The thermal resistance was measured in each cycle, and the thermal resistance degradation rate was calculated. The thermal resistance degradation rate indicates the rate of decrease in thermal resistance after a predetermined number of cycles, with the thermal resistance before the thermal test as the baseline. The thermal resistance was evaluated under the following conditions: gate voltage of 15V, cooling temperature (inlet) of 65°C using a 50% coolant, cooling flow rate of 5 L / min, heating current of 100 A, delay of 30 seconds, and heating of 30 seconds.

[0104] Figure 11 shows the results of thermal tests on the semiconductor module of the example and the semiconductor module of the comparative example. As shown in Figure 11, it was clear that the thermal resistance degradation rate of the semiconductor module of the example was extremely low compared to the semiconductor module of the comparative example. Specifically, the thermal resistance degradation rate of the semiconductor module of the example was less than 1 / 3 of that of the semiconductor module of the comparative example after 1000 cycles.

[0105] [Power Cycle Test] Power cycle tests were performed on the semiconductor modules of the example and the comparative example. This power cycle test was conducted in accordance with AQG-324, and the voltage (temperature) applied to the semiconductor module during the test was monitored. Semiconductor modules have a proportional relationship between voltage and temperature (K-factor, with an accuracy of ±0.01V for voltage), and by monitoring the voltage, it is possible to monitor abnormal heat generation of the semiconductor module during the test. The standard defines a failure as a temperature increase of 5% or more above the test temperature. In the power cycle test, a failure is defined as a broken wire. The conditions for the power cycle test (constant current) are shown in Table 5.

[0106]

[0107] The results of the power cycle test are shown in Figure 12. As shown in Figure 12, the semiconductor module of the example required more than twice as many cycles before failure compared to the semiconductor module of the comparative example. It was clear that the semiconductor module of the example had a longer lifespan than the semiconductor module of the comparative example.

[0108] [Film Thickness Control] Furthermore, as shown in Figures 8, 9 and Table 4, it was revealed that a encapsulating layer having a multilayer structure of a skin layer containing the first resin composition and a core layer containing the second resin composition can be formed using the first resin composition and the second resin composition. We then verified whether the film thickness of the skin layer and the core layer could be controlled by adjusting the amount of the first resin composition and the second resin composition used.

[0109] In this example, molded articles were produced according to the method described in the [Two-Color Molding] section above, using the first resin composition and the second resin composition in a volume ratio of 50:50 and in a volume ratio of 25:75, respectively. The obtained molded articles were divided in the direction of resin flow, and the thicknesses of the first resin composition layer (skin layer) and the second resin composition layer (core layer) were measured at approximately four positions (positions 1 to 4) from the front in the direction of flow. The thicknesses of the skin layer and core layer at each position are shown in Table 6.

[0110]

[0111] As shown in Table 6, it was found that the film thickness of the skin layer and core layer can be controlled by adjusting the amounts of the first resin composition and the second resin composition used.

[0112] [Double-Sided Cooled Semiconductor Module] Furthermore, in this example, a double-sided cooled semiconductor module, as schematically shown in Figure 3, was fabricated, that is, a semiconductor module with heat sinks on both sides. In this example, three types of insulated heat dissipation circuit boards were prepared, with a distance of 6 mm between the pair of heat sinks and a pillar, and opening widths of 11 mm, 26 mm, or 34 mm. Then, using the method and conditions described in [Two-Color Molding] above, semiconductor modules were fabricated for each of the three types of insulated heat dissipation circuit boards using a transfer molding apparatus.

[0113] As a result, a larger opening area allowed for the successful fabrication of a multilayer structure consisting of a skin layer containing the first resin composition and a core layer containing the second resin composition. Figure 13 shows a cross-sectional photograph of the fabricated double-sided cooled semiconductor module, cut parallel to the resin flow direction. Note that a line segment has been added to the cross-sectional photograph in Figure 13 at the boundary between the first resin composition and the second resin composition. As shown in Figure 13, a double-sided cooled semiconductor module with a pair of heat sinks facing outwards was successfully fabricated.

[0114] The disclosure of International Application No. PCT / JP2025 / 004017, filed on 6 February 2025, is incorporated herein by reference in its entirety. Furthermore, all documents, patent applications, and technical standards described herein are incorporated by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

[0115] 1...Semiconductor element, 2...Core layer, 3...Skin layer, 4...Sealing material layer, 5...Insulating heat dissipation circuit board, 6...Wire, 7...Lead frame, 8...Solder layer, 9...Conductive metal plate, 10...Heat sink, 11...Insulating layer, 12...Solder layer, 13...Edge

Claims

1. A semiconductor module comprising: a semiconductor element; and a sealing layer that covers at least the semiconductor element and includes a low-elasticity core layer and a high-elasticity skin layer disposed on the outer surface of the core layer.

2. The semiconductor module according to claim 1, wherein the skin layer in the sealing material layer is arranged on the surface of the semiconductor element and as the outermost layer.

3. The semiconductor module according to claim 1, comprising a wire connected to the semiconductor element, wherein the semiconductor element is in contact with the skin layer in the encapsulating material layer, and the portion of the wire excluding the connection portion with the semiconductor element is embedded in the core layer in the encapsulating material layer.

4. The semiconductor module according to claim 2, wherein the thickness of the skin layer disposed on the surface of the semiconductor element is thinner than the thickness of the outermost skin layer.

5. The semiconductor module according to claim 1, comprising an insulating heat dissipation circuit board on which the semiconductor element is mounted, wherein the insulating heat dissipation circuit board has a heat sink on the side opposite to the side on which the semiconductor element is mounted.

6. The semiconductor module according to claim 1, comprising an insulating heat dissipation circuit board on which the semiconductor element is mounted, wherein the insulating heat dissipation circuit board is provided with heat sinks on both sides facing outward.

7. The semiconductor module according to claim 1, wherein the semiconductor element comprises a power semiconductor.

8. The semiconductor module according to claim 1, wherein the amount of inorganic filler contained in the first resin composition constituting the skin layer is greater than the amount of inorganic filler contained in the second resin composition constituting the core layer.

9. A method for manufacturing a semiconductor module, comprising the steps of: placing a semiconductor element in the cavity of a transfer molding apparatus; introducing a molten first resin composition into the cavity; then introducing a molten second resin composition into the cavity; and removing the semiconductor module according to any one of claims 1 to 8 from the cavity.

10. The method for manufacturing a semiconductor module according to claim 9, wherein the skin layer containing the first resin composition is formed on the surface of the semiconductor element and on the inner surface of the cavity.

11. The method for manufacturing a semiconductor module according to claim 9, wherein the first resin composition has lower fluidity compared to the second resin composition.

12. The method for manufacturing a semiconductor module according to claim 11, wherein the flow distance measured as the length of a molded product when the first resin composition is molded using a spiral flow measurement mold compliant with EMMI-1-66 under conditions of a mold temperature of 175°C, a molding pressure of 7 MPa, and a curing time of 150 seconds is 0.9 times or less compared to the flow distance measured for the second resin composition.

13. The method for manufacturing a semiconductor module according to claim 9, wherein when arranging the semiconductor element in the cavity of a transfer molding apparatus, the heat sink in an insulating heat dissipation circuit board having the semiconductor element and the heat sink is brought into contact with a release film attached to the inner surface of the cavity.

14. A semiconductor device comprising a semiconductor module according to any one of claims 1 to 8.

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