Resin-sealed semiconductor device

Abstract

Provided is a resin-sealed semiconductor apparatus that has improved reliability and extended life.　This resin-sealed semiconductor apparatus is configured such that second bonding materials (41, 42) have a melting point higher than that of a first bonding material (10) made of a solder bonding material, one of bonding surfaces on which a power module (101) and a cooling device (11) are bonded by the first bonding material (10) corresponds to the other surface portion of a copper plate, and the other bonding surface is a surface portion of the cooling device (11) on the side of the power module, and said surface portion of the cooling device (11) on the side of the power module is formed of copper or a metal having a solder wettability equivalent to or better than that of copper.

Description

Technical Field

[0001] The present application relates to a resin-sealed semiconductor device.

Background Art

[0002] In semiconductor devices mounting power semiconductor elements, in recent years, there has been a trend towards increasing capacity. In order to pass a large current through a power semiconductor element, it is necessary to efficiently dissipate the heat generated in the semiconductor element. Therefore, efforts are being made to reduce the thermal resistance of the insulating member and the bonding member existing between the semiconductor element and a cooler such as a heat sink.

[0003] For example, the resin-sealed semiconductor device disclosed in Patent Document 1 uses a solder bonding material containing silver, copper, and bismuth as a module bonding material for bonding a power module including a semiconductor element and a cooler, so as to reduce the thermal resistance between the power module and the cooler. Further, Patent Document 1 discloses a technique of using a solder bonding material containing antimony as a chip-on bonding material for bonding a semiconductor element and a lead frame in a power module, so that the melting point of the chip-on bonding material is higher than that of the module bonding material, thereby preventing the chip-on bonding material from remelting when the power module and the cooler are bonded by the module bonding material.

[0004] Furthermore, in the conventional resin-sealed semiconductor device as described above, in order to improve the solder wettability with respect to the solder bonding material as the module bonding material, a resin-sealed semiconductor device has been proposed in which nickel plating is applied to the surface portion of the cooler on the side bonded to the power module.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the case of a resin-sealed semiconductor device in which nickel plating is applied to the surface portion on the side joined to the power module in the cooler in order to ensure solder wettability with respect to the solder joint material as the module joint material, it is necessary to perform the soldering operation using a formic acid reduction reflow facility or to perform the soldering operation using a flux having extremely high activity. However, no matter which of these soldering operations is performed, variations occur in the solder wettability with respect to the solder joint material as the module joint material among individual resin-sealed semiconductor devices. Therefore, there is a problem that voids are generated in the solder joint material, the thermal resistance increases, and the quality deteriorates, and the reliability of the resin-sealed semiconductor device decreases.

[0007] Further, when a solder joint material is used as the module joint material, there is a problem that since the solder joint material is fragile, cracks are generated in the solder joint material due to repeated temperature changes, and the life of the resin-sealed semiconductor device is reduced.

[0008] The present application discloses a technique for solving the above problems, and an object thereof is to provide a resin-sealed semiconductor device that realizes improved reliability and extended life.

Means for Solving the Problems

[0009] A resin-sealed semiconductor device including a power module and a cooler joined to the power module by a first joint material made of a solder joint material, wherein the power module includes a semiconductor element, a heat spreader on which the semiconductor element is mounted on one surface portion, a first lead frame serving as an input / output terminal joined to the heat spreader, a second lead frame serving as a main terminal joined to the semiconductor element via a second joint material, a copper plate having one surface portion joined via a resin insulating layer to the other surface portion of the heat spreader facing the one surface portion, A mold resin that covers the semiconductor element, the heat spreader, a part of the first lead frame, a part of the second lead frame, the resin insulating layer, and a part other than the other surface of the copper plate that faces the one surface thereof; Comprising: The second bonding material is made of a bonding material having a melting point higher than that of the first bonding material. Of the bonding surfaces where the power module and the cooler are bonded by the first bonding material, one bonding surface is the other surface of the copper plate, and the other bonding surface is the surface of the cooler on the power module side. The surface of the cooler on the power module side is made of copper or a copper plating layer or a tin plating layer, Formed by and, the cooler is formed of aluminum or an alloy containing aluminum, the copper plating layer or the tin plating layer is formed such that two opposite side portions thereof are present inside the planar outer shape of the mold resin, , comprising a plurality of the power modules juxtaposed planar on the surface portion of the cooler, the copper plating layer or the tin plating layer is continuously formed across the plurality of power modules, the copper plating layer or the tin plating layer is formed such that two other opposite side portions orthogonal to the two side portions are respectively present inside the planar outer shape of the mold resin of the corresponding power module, Characterized by this.

[0010] Also, the resin-sealed semiconductor device disclosed in the present application is An insulating substrate having the semiconductor element mounted on one surface; A first lead frame that serves as an input / output terminal joined to the insulating substrate; A second lead frame that serves as a main terminal joined to the semiconductor element via a second bonding material; A mold resin that covers the semiconductor element, a part other than the other surface of the insulating substrate that faces the one surface, a part of the first lead frame, and a part of the second lead frame; Comprising: The insulating substrate is composed of an insulating layer, an upper circuit provided on one surface of the insulating layer and mounting the semiconductor element, and a lower circuit provided on the other surface of the insulating layer facing the one surface. Of the upper circuit and the lower circuit, at least the other surface of the lower circuit that is located on the side opposite to the surface facing the insulating layer is made of copper. The other surface of the insulating substrate is constituted by the other surface of the lower circuit. The second bonding material is made of a bonding material having a melting point higher than that of the first bonding material. Of the bonding surfaces where the power module and the cooler are bonded by the first bonding material, one bonding surface is the other surface of the lower circuit on the insulating substrate, and the other bonding surface is the surface on the power module side of the cooler. The surface on the power module side of the cooler is made of copper, or a copper plating layer or a tin plating layer, formed by and, the cooler is formed of aluminum or an alloy containing aluminum, the copper plating layer or the tin plating layer is formed such that two opposite side portions thereof are present inside the planar outer shape of the mold resin, , comprising a plurality of the power modules juxtaposed planar on the surface portion of the cooler, the copper plating layer or the tin plating layer is continuously formed across the plurality of power modules, the copper plating layer or the tin plating layer is formed such that two other opposite side portions orthogonal to the two side portions are respectively present inside the planar outer shape of the mold resin of the corresponding power module, It is characterized by this.

Effect of the Invention

[0011] According to the resin-sealed semiconductor device disclosed in the present application, a resin-sealed semiconductor device that realizes improved reliability and extended lifespan can be obtained.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0013] Hereinafter, based on the drawings, the resin-sealed semiconductor devices according to Embodiment 1, Embodiment 2, and Embodiment 3 will be described. In each figure, the same reference numerals indicate the same or corresponding parts.

[0014] First, the resin-sealed semiconductor device that is the basis of the present application will be described. FIG. 4 is a cross-sectional view of the resin-sealed semiconductor device that is the basis of the present application. In FIG. 4, the resin-sealed semiconductor device 100 includes a power module 101 and a cooler 11. The power module 101 includes a semiconductor element 1 as a switching element, a semiconductor element 2 as a rectifying element, a copper heat spreader 3, a first copper lead frame 6 serving as an input / output terminal, a second copper lead frame 5 serving as a main terminal, a resin insulating layer 7, a copper plate 8, and a molding resin 9.

[0015] In the manufacture of the resin-sealed semiconductor device 100, the semiconductor element 1 and the semiconductor element 2 are bonded via a chip-under bonding material (not shown) on one surface portion of the heat spreader 3 by a die bonding process. Next, the first lead frame 6 is bonded to the surface portion of the end of the heat spreader 3 using a lead bonding material (not shown) by a first reflow process. Also, the second lead frame 5 is bonded to the active surfaces of the semiconductor element 2 and the semiconductor element 1 using chip-on bonding materials 41 and 42 as the second bonding material.

[0016] Next, in the transfer molding process, with the other surface of the heat spreader 3 facing one surface of the semiconductor elements 1 and 2, the heat spreader 3, a part of the first lead frame 6, a part of the second lead frame 5, the resin insulating layer 7, and the copper plate 8 encapsulated with the resin insulating layer 7 interposed therebetween, they are sealed with a molding resin 9. The other surface of the copper plate 8 facing one surface is exposed from the lower surface of the molding resin 9 of the power module 101.

[0017] Furthermore, in the second reflow process, the exposed surface of the copper plate 8 and the nickel plating layer 14 applied to one surface of the cooler 11 are joined by the module joining material 10 as the first joining material. Thereby, the power module 101 and the cooler 11 are integrally joined to form a resin-sealed semiconductor device. In order to improve the solder wettability with respect to the module joining material 10 and suppress solder voids, the joining surface between the power module 101 and the cooler 11 is made of a combination of copper and nickel plating, thereby improving the quality of soldering.

[0018] According to the resin-sealed semiconductor device described above, since the nickel plating layer 14 is applied to the surface of the cooler 11 on the side joined to the power module, the soldering operation using the module joining material 10 needs to be performed using a formic acid reduction reflow facility or using a flux with extremely high activity. However, no matter which of these soldering operations is performed, there is a variation in the solder wettability with respect to the module joining material 10 among the individual resin-sealed semiconductor devices 100. Therefore, voids may occur in the solder joining material constituting the module joining material 10, increasing the thermal resistance, and the quality of the resin-sealed semiconductor device 100 may deteriorate, and the reliability of the resin-sealed semiconductor device 100 may decrease.

[0019] In addition, since the solder joining material constituting the module joining material 10 is fragile, cracks may occur in the solder joining material due to repeated temperature changes, and the life of the resin-sealed semiconductor device 100 may decrease.

[0020] Embodiment 1. Next, a resin-sealed semiconductor device according to Embodiment 1 will be described. FIG. 1 is a cross-sectional view of the resin-sealed semiconductor device according to Embodiment 1. In FIG. 1, the resin-sealed semiconductor device 100 includes a power module 101 and a cooler 11. The power module 101 and the cooler 11 are joined by a module joining material 10 as a first joining material, as will be described later.

[0021] The power module 101 includes a semiconductor element 1 as a switching element, a semiconductor element 2 as a rectifying element, a heat spreader 3, a first lead frame 6, a second lead frame 5, a resin insulating layer 7 containing an inorganic filler in the resin, a copper plate 8, and a mold resin 9. The semiconductor element 1 as a switching element is joined to one surface portion of the heat spreader 3 by an under-chip joining material (not shown). The semiconductor element 2 as a rectifying element is joined to one surface portion of the heat spreader 3 by an under-chip joining material (not shown). The other surface portion of the heat spreader 3 facing the one surface portion is fixed to one surface portion of the copper plate 8 via the resin insulating layer 7.

[0022] The other surface portion of the copper plate 8 facing the one surface portion is exposed from the lower surface portion of the mold resin 9 of the power module 101 and is joined to a copper plating layer 12 as a surface plating layer applied to one surface portion of the cooler 11 by the module joining material 10. That is, of the joining surfaces where the power module 101 and the cooler 11 are joined by the module joining material 10 as a first joining material, one joining surface is the other surface portion of the copper plate 8, and the other joining surface is the copper plating layer 12 as a surface plating layer applied to the surface portion on the power module side of the cooler. In this way, the power module 101 and the cooler 11 are integrally joined, and the resin-sealed semiconductor device 100 is configured.

[0023] The first lead frame 6 is integrally joined to the surface portion of the end of the heat spreader 3 by a lead joining material (not shown). The lead joining material is composed of a solder joining material to ensure electrical continuity between the heat spreader 3 and the first lead frame 6. Note that instead of joining by the lead joining material, metal joining by ultrasonic waves or the like may be used. The second lead frame 5 is joined to the active surfaces of the semiconductor element 2 and the semiconductor element 1 by the on-chip joining materials 41 and 42 as the second joining materials.

[0024] The molding resin 9 encloses the aforementioned semiconductor element 1 and semiconductor element 2, the heat spreader 3, the under-chip joining material, a part of the first lead frame 6, the lead joining material, a part of the second lead frame 5, the on-chip joining materials 41 and 42, the resin insulating layer 7, and a part of the copper plate 8, and is configured to seal these from the outside.

[0025] In the resin-sealed semiconductor device according to the first embodiment configured as described above, the heat generated when the semiconductor element 1 and the semiconductor element 2 operate is dissipated to the cooler 11 through the under-chip joining material (not shown), the heat spreader 3, the resin insulating layer 7, the copper plate 8, the module joining material 10, the copper plating layer 12 as the surface plating layer, and the nickel plating layer 13 as the base plating layer.

[0026] The semiconductor element 1 in the power module 101 is composed of a semiconductor switching element such as an IGBT (Insulated Gate Biolar Transistor) or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The IGBT is an element that drives a large current through a load. The semiconductor element 1 and the semiconductor element 2 are preferably formed of, for example, silicon (Si), but are not limited to silicon. For example, it is more preferable if the semiconductor chips constituting the semiconductor element 1 and the semiconductor element 2 are formed of any material selected from the group consisting of silicon carbide (SiC), gallium nitride-based materials [for example, gallium nitride (GaN)], and diamond.

[0027] The semiconductor element 1 and the semiconductor element 2 are so-called wide-bandgap semiconductor materials having a wider bandgap than silicon. The semiconductor element 1 and the semiconductor element 2 formed using such a wide-bandgap semiconductor material can be applied to operations at high temperatures as compared with semiconductor elements using a silicon semiconductor material such as a MOSFET. The wide-bandgap semiconductor material is a semiconductor material suitable for passing a large current.

[0028] As described above, the second lead frame 5 serving as the main terminal is joined to the electrodes of the active surface as the surface portions of the semiconductor element 1 and the semiconductor element 2 via the on-chip bonding materials 41 and 42 as the second bonding materials made of a soldering material. A metal having good conductivity is used for the heat spreader 3, the first lead frame 6, and the second lead frame 5. Among the metals having good conductivity, a copper material is optimal in terms of electrical resistance, workability, cost, and the like. Here, the copper material refers to pure copper or a copper alloy having copper as a main component.

[0029] As described above, the entire power module 101 is encapsulated by a mold resin 9. It is preferable to use a resin having a coefficient of linear thermal expansion close to that of the heat spreader 3, the first lead frame 6, and the second lead frame 5 for the mold resin 9 so that the thermal deformation force caused by the mismatch of the coefficients of linear thermal expansion does not increase. Therefore, since the coefficient of linear thermal expansion of pure copper is 16 [ppm / K] to 17 [ppm / K], it is desirable that the coefficient of linear thermal expansion of the mold resin 9 is also 15 [ppm / K] to 18 [ppm / K].

[0030] The resin insulating layer 7 is required to have heat dissipation properties that transfer and dissipate the heat generated when the semiconductor element 1 and the semiconductor element 2 operate while ensuring electrical insulation. The resin insulating layer 7 is obtained by filling a thermosetting resin with an inorganic filler as an inorganic filler having high thermal conductivity and insulation properties, and adheres the heat spreader 3 and the copper plate 8 by the thermosetting reaction of the resin.

[0031] The power module 101 is joined to a copper plating layer 12 as a surface plating layer of a cooler 11 having heat dissipation fins (not shown) by a module joining material 10 as a first joining material in order to dissipate the heat generated during the operation of the semiconductor element 1 and the semiconductor element 2. As the cooler 11 that requires higher cooling performance, either a water-cooled or air-cooled cooler may be used. The cooler 11 is preferably formed of any material selected from the group consisting of copper, aluminum, and alloys of copper or aluminum. Among them, as the material of the cooler 11, aluminum or an alloy containing aluminum, which is lightweight and has excellent workability, is suitable.

[0032] In addition, in order to solder the power module 101 with the module bonding material 10, high solder wettability is required for the bonding portion of the cooler 11. Therefore, it is desirable that the material of the main body of the cooler 11 be copper. However, when the material of the main body of the cooler 11 is aluminum or an alloy containing aluminum, it is optimal that the surface plating layer be a copper plating layer 12. Instead of directly performing copper plating on aluminum or an alloy containing aluminum, it is optimal to apply a nickel plating layer 13 as an under-plating layer in order to improve plating adhesion and surface solder wettability.

[0033] As described above, a nickel plating layer 13 as an under-plating layer and a copper plating layer 12 as a surface plating layer are provided on one surface portion of the cooler 11, and a plurality of heat radiation fins (not shown) are provided on the other surface portion which is the surface portion of the cooler 11 on the anti-power module side. Note that, in the first embodiment, the cooler 11 is constituted by a flat metal heat sink, but it may be a liquid-cooled cooler having, for example, a flow path through which a coolant flows inside.

[0034] Next, a method for manufacturing a resin-sealed semiconductor device according to the first embodiment will be described. First, in the die bonding process, a semiconductor element 1 as a switching element and a semiconductor element 2 as a rectifying element are bonded to one surface portion of the heat spreader 3 with a space therebetween via a chip under-bonding material (not shown). The semiconductor element 1 as a switching element is formed of, for example, silicon, and a semiconductor chip on which an IGBT is mounted is used. The semiconductor element 2 as a rectifying element is formed of, for example, silicon, and a semiconductor chip on which a diode is mounted is used.

[0035] The chip under-bonding material is preferably any bonding material selected from the group consisting of a solder bonding material, a sinterable filler mainly composed of silver, a brazing material mainly composed of silver, a material in which copper is dispersed in tin, a gold-tin mainly composed of gold, and a gold-based alloy such as gold-germanium. These bonding materials are bonding materials having high thermal conductivity and electrical conductivity.

[0036] Next, in the first reflow process, the first lead frame 6 serving as an input / output terminal is joined to the end face portion of the heat spreader 3 using a lead bonding material (not shown). Also, the second lead frame 5 serving as a main terminal is joined to the active surface of the semiconductor element 1 as a switching element using an on-chip bonding material 42, and is joined to the active surface of the semiconductor element 2 as a rectifying element using an on-chip bonding material 41.

[0037] For the connection between the heat spreader 3 and the first lead frame 6, a lead bonding material (not shown) made of a solder bonding material is used, but other bonding methods such as ultrasonic bonding and welding may also be used. For the bonding between the semiconductor element 1 and the semiconductor element 2 and the second lead frame 5, a solder bonding material made of a ribbon solder with a constant thickness is used as the on-chip bonding materials 41 and 42.

[0038] The lead bonding material (not shown), the on-chip bonding material 41, and the on-chip bonding material 42 need to use a solder bonding material having a melting point higher than that of the module bonding material 10 so as not to remelt even at the temperature of the second reflow process in which the power module 101 is soldered by the module bonding material 10. A solder bonding material having a melting point with a solidus line containing antimony of about 240 [°C] is optimal. Note that the on-chip bonding material 41 and the on-chip bonding material 42 may be a solder bonding material containing other physical property values or a bonding material such as sintered silver as long as they do not remelt even at the temperature of the second reflow process.

[0039] Next, in the transfer molding process, the semiconductor element 1, the semiconductor element 2, the heat spreader 3, the under-chip bonding material, a part of the first lead frame 6, the lead bonding material, a part of the second lead frame 5, the on-chip bonding materials 41 and 42 as the second bonding materials, the resin insulating layer 7, and the periphery of a part of the copper plate 8 are sealed with a mold resin 9 made of a thermosetting resin. At this time, the copper plate 8 is molded such that the face portion on the side opposite to the resin insulating layer 7 is exposed from the mold resin 9.

[0040] Here, the resin insulating layer 7 is composed of a material having heat dissipation properties, insulation properties, and adhesiveness, and has a configuration in which inorganic powder fillers such as ceramic particles with high thermal conductivity are contained in a thermosetting resin such as an epoxy resin. As the inorganic filler with high thermal conductivity, ceramic particles such as aluminum nitride, silicon nitride, boron nitride, aluminum oxide (alumina), silicon oxide (silica), magnesium oxide, zinc oxide, and titanium oxide are suitable. Note that any one of these inorganic fillers may be used alone, or a plurality of types may be mixed and used.

[0041] Furthermore, the resin insulating layer 7 based on a resin material also has a function as an adhesive. Therefore, during the thermosetting of the mold resin 9, the resin insulating layer 7 adheres the heat spreader 3 and the copper plate 8 so that they are in close contact with each other. For this reason, it is not necessary to apply an adhesive to one surface portion and the other surface portion of the resin insulating layer 7. Since the adhesive causes an increase in thermal resistance, by not applying this adhesive to one surface portion and the other surface portion of the resin insulating layer 7, an increase in the thermal resistance between the resin insulating layer 7, the heat spreader 3, and thus the copper plate 8, and the mold resin 9 can be suppressed, and a power module with high heat dissipation performance can be obtained.

[0042] Since it is not necessary for the mold resin 9 to have high thermal conductivity, among silicon oxides (silica) that have good fluidity when contained in a thermosetting resin such as an epoxy resin and are easy to adjust the coefficient of linear expansion, fused silica is optimal. Since the resin-sealed semiconductor device 100 uses a large amount of copper material, by matching the coefficient of linear expansion of the mold resin 9 to that of copper, that is, making the coefficient of linear expansion of the mold resin 9 the same as or approximate to that of copper, stress reduction inside the resin-sealed semiconductor device 100 can be achieved. Therefore, the amount of the inorganic filler is adjusted so that the coefficient of linear expansion of the mold resin 9 is between 15 [ppm / K] and 18 [ppm / K]. This has the effect of improving the reliability against temperature cycles.

[0043] Next, in the second reflow process, the power module 101 and the cooler 11 are joined using the module joining material 10 as the first joining material. In solder reflow, it is necessary to heat the power module 101 and the cooler 11 to the temperature range at which the module joining material 10 is melted. At this time, the solder joining material used in the power module 101 may also melt. If the solder joining material melts, cracks may occur in the mold resin 9 due to the volume expansion from solid to liquid. Therefore, it is necessary to provide a difference in melting point between the joining materials such as the solder joining material used inside the power module 101 and the module joining material 10 used to join the cooler 11 and the power module.

[0044] As the on-chip joining materials 41 and 42 and the lead joining material (not shown) used inside the power module 101, a solder joining material with a liquidus line of approximately 240 [°C] of high-melting-point solder containing antimony in tin is used. As the module joining material 10, a solder joining material with a liquidus line of 210 [°C] of low-melting-point solder containing silver, copper, bismuth, and indium in tin is used. In this case, the difference in melting point between the on-chip joining materials 41 and 42, the lead joining material (not shown), and the module joining material 10 is approximately 30 [°C]. Therefore, a sufficient difference in melting point can be provided between the on-chip joining materials 41 and 42, the lead joining material, and the module joining material 10, and re-melting of the solder joining material inside the power module 101 can be prevented.

[0045] The low-melting-point solder containing silver, copper, bismuth, and indium in tin has a lower liquidus line temperature and higher strength than the low-melting-point solder containing silver, copper, and bismuth in tin. By adjusting the content ratios of bismuth and indium, the generation rate of voids can also be reduced, so there is an effect of further improving the reliability against temperature cycles.

[0046] In addition, since the low-melting-point solder has inferior solder wettability compared to general solder, the joining surfaces are made of metals with good solder wettability, and a flux for improving solder wettability is essential. Since copper is a metal with extremely good solder wettability, among the joining surfaces where the power module 101 and the cooler 11 are joined by the module joining material 10 as the first joining material, one joining surface is the other surface portion of the copper plate 8, and the other joining surface is the surface portion on the power module side of the cooler 11. The surface portion on the power module side of the cooler 11 is formed of copper or a metal having solder wettability equal to or better than that of copper. Thereby, solder wettability can be improved, and a small resin-sealed semiconductor device with low thermal resistance, high quality, and high reliability can be provided. Instead of the copper plating layer 12, a metal plating layer having solder wettability equal to or better than that of copper, such as a tin plating layer, may be used.

[0047] The copper plating layer 12 as the surface plating layer and the nickel plating layer 13 as the underlayer plating layer are applied to a region having a dimension equal to or larger than the outer diameter dimension of the power module 101 in the surface portion on the power module side of the cooler 11. Therefore, the power module 101 is joined within that region without protruding from the region where the copper plating layer 12 as the surface plating layer and the nickel plating layer 13 as the underlayer plating layer are applied.

[0048] Embodiment 2. Next, a resin-sealed semiconductor device according to Embodiment 2 will be described. FIG. 2 is a cross-sectional view of the resin-sealed semiconductor device according to Embodiment 2, and FIG. 3 is a plan view of the resin-sealed semiconductor device according to Embodiment 2. FIG. 3 shows a state in which three resin-sealed semiconductor devices 100 corresponding to each of the three phases applied to the three-phase power conversion device are arranged side by side in a plane. The difference from the resin-sealed semiconductor device according to Embodiment 1 is only the size of the region where the copper plating layer 12 as the surface plating layer and the nickel plating layer 13 as the underlayer plating layer are applied.

[0049] In FIGS. 2 and 3, the copper plating layer 12 as the surface plating layer and the nickel plating layer 13 as the base plating layer are formed in a planar outer shape of the same dimension, and are formed larger than the planar outer shape of the module bonding material 10 as the first bonding material. In the region of the cooler 11 where the copper plating layer 12 and the nickel plating layer 13 are not provided, aluminum, which is the material constituting the cooler 11, is exposed.

[0050] The copper plating layer 12 and the nickel plating layer 13 are formed in a rectangular shape, for example, a rectangular shape, and are formed such that two opposing side portions 121 and 122 thereof are present inside the planar outer shape of the mold resin 9. Further, three power modules 101 juxtaposed in a plane are joined to the surface of the cooler 11, and the copper plating layer 12 and the nickel plating layer 13 are continuously formed across the three power modules 101. The copper plating layer 12 is formed such that two other side portions 123 and 124 opposing orthogonally to the two side portions 121 and 122 are present inside the planar outer shape of the mold resin 9 of the corresponding power module 101, respectively.

[0051] In the second reflow process of joining the power module 101 and the cooler 11 with the module bonding material 10, since a flux for promoting solder wettability is used, solder balls are generated due to the activator or gas of the flux. If this solder ball scatters on the surface of the cooler 11 and the scattering destination is a location where solder wettability is imparted, the solder ball will melt and adhere to the surface of the cooler 11 as a conductive foreign substance, and the insulation may deteriorate. However, since aluminum has no solder wettability, even if a solder ball adheres, it can be easily removed by washing.

[0052] In a general resin-sealed semiconductor device, for the power module 101, in order to achieve layout efficiency as an inverter and reduce inductance, for example, three power modules 101 corresponding to each phase of a three-phase system are arranged in parallel in a planar manner close to the surface of the cooler 11. Therefore, the size of the copper plating layer 12 as the surface plating layer is set to be large enough to connect adjacent power modules 101 rather than being divided for each power module 101, which can suppress the plating cost.

[0053] Although there is a possibility that solder balls adhere and melt between adjacent power modules 101, since the side surfaces of the power module 101 from which the first lead frame 6 is led out and the side surfaces of the power module 101 from which the second lead frame 5 is led out are different side surfaces, it does not affect the insulation.

[0054] As a method of partially plating the surface of the cooler 11, after plating the entire cooler 11 with a plating layer, it is low-cost to cut and remove the areas other than the copper plating layer 12 which is the surface plating layer. However, a method of masking the non-plating areas during plating and performing partial plating may also be used.

[0055] Embodiment 3. Next, the resin-sealed semiconductor device according to Embodiment 3 will be described. FIG. 5 is a cross-sectional view of the resin-sealed semiconductor device according to Embodiment 3. The resin-sealed semiconductor device according to the embodiment 3 differs from the resin-sealed semiconductor device according to the aforementioned Embodiment 1 only in the internal insulation structure of the power module 101. Instead of the heat spreader 3, resin insulation layer 7, and copper plate 8 in FIG. 1 of Embodiment 1, in Embodiment 3 shown in FIG. 5, an upper circuit 15, a ceramic insulation layer 16, and a lower circuit 17 are provided.

[0056] In FIG. 5, the resin-sealed semiconductor device 100 includes a power module 101 and a cooler 11. The power module 101 and the cooler 11 are joined by a module joining material 10 as a first joining material.

[0057] The power module 101 includes a semiconductor element 1 as a switching element, a semiconductor element 2 as a rectifying element, an upper circuit 15, a ceramic insulating layer 16, a lower circuit 17, a first lead frame 6, a second lead frame 5, and a mold resin 9. The upper circuit 15, the ceramic insulating layer 16, and the lower circuit 17 constitute an insulating substrate 50. The upper circuit 15 and the lower circuit 17 are made of, for example, copper. Note that, of the upper circuit 15 and the lower circuit 17, the other surface portion located on the opposite side to one surface portion of the lower circuit 17 facing the ceramic insulating layer 16 may be made of copper.

[0058] Generally, in an insulating substrate, a conductor such as a copper plate on which a semiconductor element is mounted is referred to as an upper circuit, and a conductor such as a copper plate on which a semiconductor element is not mounted is referred to as a lower circuit. Here, in FIG. 5, the upper circuit 15 constituting the insulating substrate 50 mounts a semiconductor element 1 as a switching element and a semiconductor element 2 as a rectifying element, and is constituted by, for example, a single copper plate without pattern division. Also, the lower circuit 17 constituting the insulating substrate 50 does not mount a semiconductor element and is constituted by, for example, a single copper plate without pattern division.

[0059] The semiconductor element 1 as a switching element is joined to one surface portion of the insulating substrate 50 by an under-chip joining material (not shown). The semiconductor element 2 as a rectifying element is joined to one surface portion of the insulating substrate 50 by an under-chip joining material (not shown).

[0060] The molding resin 9 encapsulates the aforementioned semiconductor element 1 and semiconductor element 2, the upper circuit 15, the ceramic insulating layer 16, the under-chip bonding material, a part of the first lead frame 6, the lead bonding material, a part of the second lead frame 5, the on-chip bonding materials 41 and 42, and a part of the lower circuit 17, and is configured to seal these from the outside.

[0061] On the other surface of the lower circuit 17 of the insulating substrate 50, which is located on the side opposite to the one surface facing the ceramic insulating layer 16 as the insulating layer, is exposed from the lower surface of the molding resin 9 of the power module 101, and is joined by the module bonding material 10 to the copper plating layer 12 as the surface plating layer applied to one surface of the cooler 11. That is, among the bonding surfaces where the power module 101 and the cooler 11 are joined by the module bonding material 10 as the first bonding material, one bonding surface is the other surface of the copper-made lower circuit 17, and the other bonding surface is the copper plating layer 12 as the surface plating layer applied to the surface of the cooler on the power module side. In this way, the power module 101 and the cooler 11 are integrally joined, and the resin-sealed semiconductor device 100 is configured.

[0062] The first lead frame 6 is integrally joined to the surface of the end of the insulating substrate 50 by a lead bonding material (not shown). The lead bonding material is composed of a solder bonding material in order to ensure electrical conductivity between the insulating substrate 50 and the first lead frame 6. Note that instead of joining by the lead bonding material, metal bonding by ultrasonic waves or the like may be used. The second lead frame 5 is joined to the active surfaces of the semiconductor element 2 and the semiconductor element 1 by the on-chip bonding materials 41 and 42 as the second bonding materials.

[0063] In the resin-sealed semiconductor device according to Embodiment 3 configured as described above, when the semiconductor element 1 and the semiconductor element 2 operate, the heat generated is dissipated to the cooler 11 through an under-chip bonding material (not shown), the upper circuit 15 in the insulating substrate 50, the ceramic insulating layer 16 in the insulating substrate, the lower circuit 17 in the insulating substrate 50, the module bonding material 10, the copper plating layer 12 as a surface plating layer, and the nickel plating layer 13 as an underlayer plating layer.

[0064] In the manufacture of the resin-sealed semiconductor device 100, an upper circuit 15 made of copper with a thickness of about 1 [mm] is brazed to the surface of the ceramic insulating layer 16 of silicon nitride or aluminum nitride, and a lower circuit 17 made of copper with a thickness of about 1 [mm] is brazed to the back surface of the ceramic insulating layer 16. On one surface portion of the insulating substrate 50 thus configured, the semiconductor element 1 and the semiconductor element 2 are joined via an under-chip bonding material (not shown) by a die bonding process.

[0065] Next, in the first reflow process, the first lead frame 6 is joined to the surface portion of the end of the upper circuit 15 in the insulating substrate 50 using a lead bonding material (not shown). Also, the second lead frame 5 is joined to the active surfaces of the semiconductor element 2 and the semiconductor element 1 using the chip-on bonding materials 41 and 42 as the second bonding material.

[0066] Next, in the transfer molding process, the semiconductor element 1 and the semiconductor element 2, the upper circuit 15, the ceramic insulating layer 16, a part of the lower circuit 17, a part of the first lead frame 6, and a part of the second lead frame 5 are encapsulated and sealed with the molding resin 9. The other surface portion facing one surface portion of the insulating substrate 50 is constituted by the back surface of the copper lower circuit 17. The back surface of the lower circuit 17 constituting the other surface portion of the insulating substrate 50 is exposed from the lower surface portion of the molding resin 9 of the power module 101.

[0067] Similar to the resin insulating layer 7 in Embodiment 1, the ceramic insulating layer 16 is required to have heat dissipation properties that can transfer and dissipate the heat generated when the semiconductor element 1 and the semiconductor element 2 operate to the cooler 11 while ensuring electrical insulation. The ceramic insulating layer 16 is a sintered body having high thermal conductivity and insulation properties, and has a thermal conductivity more than 10 times that of the resin insulating layer 7 in Embodiment 1. Even when the thicknesses of the upper circuit 15 and the lower circuit 17 are reduced to about half of the thickness of the heat spreader 3 shown in FIG. 1 in Embodiment 1, the heat dissipation performance of the heat generated when the semiconductor element 1 and the semiconductor element 2 operate can be improved, and the low thermal resistance and miniaturization of the power module 101 can be realized.

[0068] In addition, in order to solder-join the power module 101 with the module joining material 10, high solder wettability is required at the joining portion of the cooler 11. Therefore, it is desirable that the material of the main body of the cooler 11 be copper. However, when the material of the main body of the cooler 11 is aluminum or an alloy containing aluminum, it is most optimal that the surface plating layer be a copper plating layer 12. Instead of directly performing copper plating on aluminum or an alloy containing aluminum, it is most optimal to apply a nickel plating layer 13 as an undercoat plating layer in order to improve plating adhesion and surface solder wettability.

[0069] As described above, a nickel plating layer 13 as an undercoat plating layer and a copper plating layer 12 as a surface plating layer are provided on one surface portion of the cooler 11, and a plurality of heat dissipation fins (not shown) are provided on the other surface portion of the cooler 11, which is the surface portion on the anti-power module side of the cooler 11. Note that the cooler 11 may be, for example, a liquid-cooled cooler having a flow path for passing a coolant inside.

[0070] Currently, on the front and back surfaces of the ceramic insulating layer 16, the upper circuit 15 and the lower circuit 17 are brazed, but they do not necessarily need to be integrated and may be joined in the transfer molding process. Further, the ceramic insulating layer 16 may be composed of only ceramics, or may be composed of a composite of ceramics and resin or the like as long as it is a material that can satisfy electrical insulation and heat dissipation properties.

[0071] Although various exemplary embodiments and examples are described in this application, the various features, aspects, and functions described in one or more of the embodiments are not limited to the application of a specific embodiment, but are applicable to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are envisioned within the scope of the technology disclosed in this application. For example, it includes the case of deforming, adding, or omitting at least one component, and further, the case of extracting at least one component and combining it with the components of other embodiments.

Description of Reference Numerals

[0072] 100 Resin-encapsulated semiconductor device, 101 Power module, 1, 2 Semiconductor elements, 3 Heat spreader, 41, 42 Chip-on bonding material, 5 Second lead frame, 6 First lead frame, 7 Resin insulating layer, 8 Copper plate, 9 Mold resin, 10 Module bonding material, 11 Cooler, 12 Copper plating layer, 13, 14 Nickel plating layer, 15 Upper circuit, 16 Ceramic insulating layer, 17 Lower circuit, 50 Insulating substrate

Claims

1. A resin-sealed semiconductor device comprising a power module and a cooler joined to the power module by a first joining material made of a soldering material, The power module includes a semiconductor element, a heat spreader on which the semiconductor element is mounted on one surface portion, a first lead frame serving as an input / output terminal joined to the heat spreader, a second lead frame serving as a main terminal joined to the semiconductor element via a second joining material, a copper plate having one surface portion joined via a resin insulating layer to the other surface portion of the heat spreader facing the one surface portion, a molding resin that covers the semiconductor element, the heat spreader, a part of the first lead frame, a part of the second lead frame, the resin insulating layer, and a portion other than the other surface portion of the copper plate facing the one surface portion, and is provided with The second joining material is made of a joining material having a melting point higher than that of the first joining material, Of the joining surfaces where the power module and the cooler are joined by the first joining material, one joining surface is the other surface portion of the copper plate, and the other joining surface is the surface portion on the power module side of the cooler, The surface portion on the power module side of the cooler is formed of copper, or a copper plating layer, or a tin plating layer, The cooler is formed of aluminum or an alloy containing aluminum, The copper plating layer or the tin plating layer is formed such that two opposite side portions thereof are present inside the planar outer shape of the molding resin, The cooler includes a plurality of the power modules juxtaposed in a planar manner, The copper plating layer or the tin plating layer is continuously formed across the plurality of power modules, The copper plating layer or the tin plating layer is formed such that the other two sides facing each other orthogonally to the two sides are each present inside the planar outer shape of the mold resin of the corresponding power module. A resin-sealed semiconductor device characterized by this.

2. A resin-sealed semiconductor device including a power module and a cooler joined to the power module by a first joining material made of a soldering material, The power module includes a semiconductor element, an insulating substrate on which the semiconductor element is mounted on one surface portion, a first lead frame serving as an input / output terminal joined to the insulating substrate, a second lead frame serving as a main terminal joined to the semiconductor element via a second joining material, a mold resin covering the semiconductor element, a portion other than the other surface portion of the insulating substrate facing the one surface portion, a part of the first lead frame, and a part of the second lead frame, and is provided with The insulating substrate is composed of an insulating layer, an upper circuit provided on one surface portion of the insulating layer on which the semiconductor element is mounted, and a lower circuit provided on the other surface portion of the insulating layer facing the one surface portion. Among the upper circuit and the lower circuit, at least the other surface portion of the lower circuit located on the opposite side with respect to one surface portion facing the insulating layer is made of copper. The other surface portion of the insulating substrate is composed of the other surface portion of the lower circuit. The second joining material is made of a joining material having a melting point higher than the melting point of the first joining material. Among the joining surfaces where the power module and the cooler are joined by the first joining material, one joining surface is the other surface portion of the lower circuit in the insulating substrate, and the other joining surface is the surface portion on the power module side of the cooler. The surface portion on the power module side in the cooler is formed of copper, or a copper plating layer, or a tin plating layer. The cooler is formed of aluminum or an alloy containing aluminum. The copper plating layer or the tin plating layer is formed such that two opposite side portions thereof are present inside the planar outer shape of the mold resin. The cooler includes a plurality of the power modules juxtaposed in a plane on the surface portion of the cooler. The copper plating layer or the tin plating layer is continuously formed across the plurality of power modules. The copper plating layer or the tin plating layer is formed such that two other opposite side portions orthogonal to the two side portions are present inside the planar outer shape of the mold resin of the corresponding power module, respectively. A resin-sealed semiconductor device, characterized in that.

3. The cooler is formed of copper. The surface portion on the power module side in the cooler is formed of the copper forming the cooler. The resin-sealed semiconductor device according to claim 1 or claim 2, characterized in that.

4. The copper plating layer or the tin plating layer is applied to the surface portion on the power module side of the cooler via a nickel plating layer. The resin-sealed semiconductor device according to claim 1 or claim 2, characterized in that.

5. The first bonding material contains at least bismuth and indium. The resin-sealed semiconductor device according to claim 1 or claim 2, characterized in that.

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