Semiconductor device and manufacturing method thereof

Abstract

Semiconductor device comprising: an insulating substrate (1); a semiconductor element (3) arranged on a first surface of the insulating substrate (1); a housing (51) connected to the insulation substrate (1) and configured to accommodate the semiconductor element (3) therein; and a resin (6) filled into the housing (51) to bury the semiconductor element (3), wherein, assuming that the thickness of the insulating substrate (1) is denoted by t1, the thickness of the resin (6) is denoted by t2, the linear expansion coefficient of the insulating substrate (1) is denoted by α1 and the linear expansion coefficient of the resin (6) is denoted by α2, the relationship therebetween t2 ≥ t1 and α2 ≥ α1 is satisfied, the housing (51) is provided with an overlapping portion which overlaps with an outer edge of the insulating substrate (1) in plan view, and an extension portion (53) which extends from the overlapping portion further outward than the outer edge of the insulating substrate (1), the semiconductor device further comprises a fixing member (52) configured to fix the extension portion (53) of the housing (51) to an external member (54) arranged outside the semiconductor device, a heat radiation grease (7) is arranged between the insulation substrate (1) and the external element (54) and the overlapping portion is provided with a stepped portion (511) to accommodate the outer edge of the insulation substrate (1), and the depth of the stepped portion (511) is greater than the sum of the thickness (t1) of the insulating substrate (1) and a thickness of the heat radiation grease (7) in a state in which the extension portion (53) of the housing (51) is fixed to the external member (54) by the fixing member (52), and the depth of the stepped portion (511) is smaller than the sum of the thickness (t1) of the insulating substrate (1) and a degree of distortion of the insulating substrate (1) in a state in which the outer edge of the insulating substrate (1) has not yet been pressed by the stepped portion (511) of the housing (51), and wherein, in the state where the extension portion (53) of the housing (51) is fixed to the external member (54) by the fixing member (52), a second surface of the insulation substrate (1) opposite to the first surface thereof is distorted into a convex shape.

Description

[0001] The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly relates to a semiconductor device having an insulating substrate on which a semiconductor element connected to an external element is disposed, and a manufacturing method thereof.

[0002] It is known that a semiconductor device has been conventionally used in a variety of aspects, such as power generation, power transmission, and efficient utilization and / or reproduction of energy. As such, a semiconductor device is configured to include an insulating substrate on which a semiconductor element is disposed, which is connected to a cooling element. Further, in such a semiconductor device, a package is disposed to house the semiconductor element therein, and the interior of the package may be filled with resin.

[0003] For example, to improve the productivity and reliability of such a semiconductor device, a direct molding sealing technique, which involves injecting an epoxy sealing resin with a filler dispersed therein into the package, is gaining popularity. However, in such a semiconductor device, how to ensure close contact between the insulation substrate and the heat sink is a problem.

[0004] For example, JP 2000-200865 A discloses a method which is carried out in such a manner that an insulating substrate is preliminarily distorted downward into a convex shape, the semiconductor elements are installed on the insulating substrate to form a module, and the module is fixed by screws to the cooling member with a kind of heat radiation grease which is evenly distributed between the insulating substrate and the cooling member to ensure the close contact.

[0005] Moreover, JP H08-236667 A discloses a method which is carried out in such a manner that an inner portion of the insulating substrate where the semiconductor elements arranged from an inner to an outer edge thereof are installed is pressed down to distort it into a convex shape, and the distorted insulating substrate is pressed against the cooling member to improve the close contact between the insulating substrate and the cooling member.

[0006] A semiconductor device, such as one equipped with a power semiconductor element operating under high voltage and / or large current, is required to have the functions of efficiently radiating Joule heat generated due to junction resistance and / or heat generated due to conversion loss to the outside. In a packaged semiconductor device (a type of semiconductor device configured with its semiconductor elements housed within a package), which is commonly used in industrial applications such as transportation equipment and / or factory automation equipment, a type of heat radiation grease is typically used to transfer heat from a lower surface of the insulating substrate to the cooling element.Therefore, how to sufficiently distribute the heat radiation grease or how to avoid the occurrence of air bubbles (voids) caused by air trapped in the heat radiation grease is important for long-term efficient heat radiation. To this end, it is important to control the distortion of the insulation substrate or a heat sink exposed from the bottom surface of the semiconductor device, and it is also necessary to consider the deformation of the package or the like that occurs when the heat sink is fixed with screws.

[0007] Furthermore, to seal and insulate the power semiconductor elements and wires inside the package for the purpose of improving reliability, the direct-encapsulation type sealing resin was applied as described above. The direct-encapsulation type sealing resin is a liquid resin obtained by dispersing a filler such as silicon oxide in an epoxy resin, and the liquid resin is heated to cure after being injected into the package. The use of such a direct-encapsulation type sealing resin can, for example, eliminate the need for a transfer mold.However, since the direct potting type sealing resin has a higher elastic modulus compared to gel, it causes a larger deformation in the semiconductor device due to curing shrinkage and consequently, it is necessary to adopt a new concept to control the amount of distortion of the insulation substrate described above.

[0008] In the technology described in JP 2000-200865 A, it is necessary to perform wire bonding for the purpose of chip bonding or wiring semiconductor elements such as a power semiconductor element to the distorted insulation substrate. Since it is difficult to stabilize the positioning and / or connection conditions in this case, the operability of such an operation is considered lower than that when a flat insulation substrate is used, and thus, it is considered a major factor reducing yield and productivity and / or product reliability. Moreover, when fixing the insulation substrate to the cooling element by screws, if the insulation substrate is fixed to the cooling element by screws too tightly at the fixing portion, the insulation substrate may reversely distort, thereby trapping air therein.

[0009] In the technology disclosed in JP H08-236667 A, although the cancellation of the linear expansion difference between the insulating substrate and a metallic heat radiation member serving as a base was considered, the influence of the insulating sealing resin was not particularly considered. Therefore, it is difficult to distort the insulating substrate into a convex shape and maintain the shape stability. In other words, it is difficult to reliably increase the close contact of the insulating substrate with the heat radiation member, and furthermore, productivity and / or yield in the manufacturing process of a semiconductor device may be adversely affected.

[0010] DE 10 2008 023 711 A1 describes a semiconductor module in which a first metal foil is bonded to the lower surface of an insulating plate, a second metal foil is bonded to the upper surface of the insulating plate, and semiconductor devices are bonded to the second metal foil. A resin casing surrounds the first metal foil, the insulating plate, the second metal foil, and semiconductor devices on the side above the lower surface of the first metal foil, and epoxy resin is packed into the space between the inner surface of the resin casing and the outer peripheral surface of the first metal foil and the outer surfaces of the insulating plate, the second metal foil, and the semiconductor devices. By means of the lower surface of the metal foil and the epoxy resin exposed by the resin casing, a flat surface is formed that can be brought into close contact with a cooling element. The insulating substrate is formed of Al2O3.The thickness of the epoxy resin is greater than that of the substrate, and its coefficient of linear expansion is approximately 15 ppm / K, which is larger than that of Al2O3.

[0011] A similar semiconductor module is disclosed in DE 39 15 707 A1.

[0012] US 2003 / 0 094 682 A1 discloses a semiconductor module in which an insulating substrate is held in a stepped portion between a heat sink and a flange mounted thereon. In one embodiment, the insulating substrate is bent such that its edge protrudes away from the heat sink.

[0013] JP 2011 - 187 711 A also describes a semiconductor module in which an insulating substrate is held in a stepped portion between a heat sink and a flange mounted thereon. The depth of the stepped portion is smaller than the thickness of the insulating substrate.

[0014] Therefore, an object of the present invention is to provide a semiconductor device that can be obtained by stably distorting an insulating substrate into a convex shape with high reliability while ensuring close contact between a cooling member and the insulating substrate, and a manufacturing method thereof.

[0015] According to the invention, this object is achieved by a semiconductor device according to claim 1 or by a manufacturing method according to claim 4.

[0016] Advantageous further developments of the invention emerge from the dependent claims.

[0017] Further features and advantages of the invention will become apparent from the description of embodiments of the invention with reference to the figures. The figures show: Fig. 1 is a schematic cross-sectional view illustrating a semiconductor device according to a first embodiment of the present invention, Fig. 2 a plan view of the Fig. 1 shown semiconductor device, Fig. 3 a flow chart showing a manufacturing process of the Fig. 1, Fig. 4 is a schematic sectional view for explaining a manufacturing method of the Fig. 3 shown semiconductor device, Fig. 5 is a schematic sectional view for explaining a manufacturing method of the Fig. 3 shown semiconductor device, Fig. 6 is a schematic sectional view for explaining a manufacturing method of the Fig. 3 shown semiconductor device, Fig. 7 is a schematic sectional view showing a modified example of the Fig. 1, Fig. 8 is a schematic sectional view showing a modified example of the Fig. 1, Fig. 9 is a schematic cross-sectional view illustrating a semiconductor device according to a second embodiment of the present invention, and Fig. 10 is a schematic cross-sectional view showing a modified example of the Fig. 9 represents the semiconductor device shown.

[0018] Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that in the following drawings, the same or corresponding parts are assigned the same reference numerals, and their descriptions will not be repeated. (First embodiment)

[0019] Fig. 1 is a schematic cross-sectional view illustrating a semiconductor device according to a first embodiment of the present invention. Fig. 2 is a plan view of the Fig. 1. For clarity in description, the direct molding type sealing resin (a type of sealing resin formed by direct molding may be simply referred to as a sealing resin hereinafter, if appropriate) is not shown in the drawings. (Structure of the semiconductor device)

[0020] With reference to Fig. 1 and Fig. 2, a resin semiconductor device mainly includes an insulating substrate 1 (hereinafter referred to as substrate 1 when appropriate), a power semiconductor element 3 serving as a semiconductor element, a package 51, and a direct-molding type sealing resin 6 (hereinafter referred to as sealing resin 6 when appropriate) serving as a resin filled in the package 51. The semiconductor device further includes a screw 52 serving as a fastening member for fastening the package 51 to a cooling device 54 serving as a cooling member, which is one example of an external member arranged outside the semiconductor device. Assuming that the thickness of the insulating substrate 1 is denoted by t1, the thickness of the resin 6 is denoted by t2, the linear expansion coefficient of the insulating substrate 1 is denoted by α1, and the linear expansion coefficient of the resin 6 is denoted by α2, the relationship therebetween satisfies t2 ≥ t1 and α2 ≥ α1.A second surface of the insulation substrate 1 opposite to a first surface thereof on which the power semiconductor element 3 is arranged is distorted into a convex shape.

[0021] The dimensions of the insulation substrate 1 are, for example, 70 mm in the vertical direction × 70 mm in the horizontal direction × 3 mm in thickness. The insulation substrate 1 has a multilayer structure in which an epoxy insulation layer 12 and a copper wiring 11 are formed on a copper base 13. The linear expansion coefficient of the insulation substrate 1 of such a multilayer structure can be determined by allocating the linear expansion coefficients of materials of each layer according to volume ratios, or can actually be determined by experiments. The power semiconductor element 3 is arranged on one surface, namely, a first surface of the insulation substrate 1.As an example of the power semiconductor element 3, an IGBT dimensioned at 15 mm in the vertical direction × 15 mm in the horizontal direction × 0.3 mm in thickness or a diode dimensioned at 12 mm in the vertical direction × 15 mm in the horizontal direction × 0.3 mm in thickness may be given.

[0022] The power semiconductor element 3 is die-bonded to a copper wiring 11 on the insulation substrate 1 using solder (for example, Sn-Ag-Cu solder with a melting point of 217°C). The power semiconductor element 3 forms an electrical circuit between an external signal terminal 42 and an external main terminal 43 of the package 51 through a wiring 41 (for example, an aluminum wire with φ 0.4 mm on the main circuit side) formed by wire bonding. An opening is formed in the external main terminal 43, and a nut 44 is arranged at the bottom of the opening.In the present embodiment, the casing 51 may be any casing formed of resin, for example, in a rectangular shape in plan view, and more specifically, formed of polyphenylene sulfide (PPS) into a frame body having a rectangular shape sized 120 mm in the vertical direction × 80 mm in the horizontal direction × 20 mm in height. The casing 51 is arranged to surround the outer periphery of the insulation substrate 1. A sleeve portion 53 is formed on the outer periphery of the casing 51, projecting outward.

[0023] The direct-molding type sealing resin 6 for sealing and insulating the power semiconductor element 3 and the wiring 41 is injected into a region surrounded by the case 51 and the insulation substrate 1 (a region inside the case 51). The direct-molding type sealing resin 6 can be obtained by dispersing a silicon dioxide filler in the epoxy resin. The sleeve portion 53 of the case 51 is provided with a through hole for inserting a screw 52 therein. The case 51 is fixed to the cooling device 54 by a screw 52.The cooling device 54 may be any cooling device, for example, sized 120 mm in the vertical direction × 80 mm in the horizontal direction × 20 mm in height, and configured to include a flat upper surface in contact with the insulating substrate 1 and a plurality of fins protruding from a lower surface in a direction away from the flat upper surface in contact with the insulating substrate 1. Any materials can be used as the material for the cooling device 54, and among them, aluminum is preferred (particularly, it is cast from aluminum). Heat radiation grease 7 is supplied between the insulating substrate 1 and the cooling device 54. The heat radiation grease 7 can be obtained, for example, by dispersing a silica filler in silicone resin.

[0024] The second surface of the insulating substrate 1, facing the cooling device 54, is distorted into a convex shape. A stepped portion 511 for supporting the outer edge of the insulating substrate 1 is formed at a base part of the inner periphery of the casing 51. As the outer edge is pressed against the cooling device 54 by the stepped portion 511, the second surface of the insulating substrate 1 is distorted into a convex shape, enabling close contact between the insulating substrate 1 and the cooling device 54. (Manufacturing method of the semiconductor device)

[0025] Fig. 3 is a flow chart showing a manufacturing process of the Fig. 1 and Fig. 2. Fig. 4 to 6 are schematic cross-sectional views for explaining the Fig. 3. The manufacturing method of the semiconductor device will be described below with reference to Fig. 3 to 6.

[0026] First, a preparation step (S10) is carried out, which Fig. 3. In particular, as shown in Fig. As shown in Fig. 4, first, a power semiconductor element 3 is placed on a copper wiring 11 of the insulation substrate 1 with a solder 31 interposed therebetween, and they are heated to perform die bonding. Next, after the case 51 is arranged to surround the outer periphery of the insulation substrate 1, a main circuit and a signal circuit are each formed by die bonding an aluminum wire serving as a wiring 41. The insulation substrate is substantially flat at this stage.

[0027] Next, a resin sealing step (S20) is carried out, which Fig. 3. In particular, as shown in Fig. 5, the direct-molding type sealing resin 6 is injected into the package 51 at room temperature. Then, a heating treatment is performed in an oven serving as a heater at 150°C for three hours to cure the direct-molding type sealing resin 6. During the heating treatment, due to the curing shrinkage of the direct-molding type sealing resin 6 (for example, shrinkage of about 5 volume%) and a difference between the thermal expansion coefficient (linear expansion coefficient) of the direct-molding type sealing resin 6 and the thermal expansion coefficient (linear expansion coefficient) of the insulating substrate 1, the insulating substrate 1 distorts convexly downward (for example, to a distortion amount of about 0.1 mm).In the present embodiment, the linear expansion coefficient of the insulating substrate 1 may be, for example, 16 ppm / K, and the linear expansion coefficient of the direct-molding type sealing resin 6 may be, for example, 18 ppm / K.

[0028] Finally, an assembly step (S30) is carried out in Fig. 3. In particular, as shown in Fig. As shown in Fig. 6, a heat radiation grease 7 is applied to a central part of the flat upper surface of the cooling device 54, and, as indicated by an arrow, a screw 52 is inserted into the through hole in the sleeve portion 53 of the housing 51 to fix the housing. In the present embodiment, the depth of the stepped portion 511 for receiving a part (the outer edge) of the insulating substrate 1 in the housing 51 is set to be smaller than the sum (for example, 3.1 mm) of the thickness t1 of the insulating substrate 1 (for example, 3 mm) and the distortion amount of the insulating substrate (for example, 0.1 mm). For example, the depth of the stepped portion 511 may be set to 3.0 mm.

[0029] Since the sleeve portion 53 is arranged further outward than the outer periphery of the insulation substrate 1, the outer periphery of the insulation substrate 1 can be pressed against the cooling side 54 by tightening the screw 52. Therefore, it is possible to adjust the amount of distortion of the insulation substrate 1 from 0.1 mm to almost flat while holding the insulation substrate 1 so that it is convexly distorted downward (towards the cooling device 54 side). In this way, it is possible to Fig. 1 and Fig. 2 to obtain the semiconductor device shown.

[0030] Fig. 7 is a schematic sectional view showing a modified example of the Fig. 1. As shown in Fig. 7, in order to prevent the direct-molding type sealing resin 6 from leaking, applying an adhesive 17 to a contact portion between the insulation substrate 1 and the housing 51 may also be effective. Fig. 7, the semiconductor device is basically the same structure as that shown in Fig. 1, but differs in that the adhesive 17 is applied to the contact portion between the case 51 and the insulating substrate 1. The adhesive 17 is applied in a ring shape along the outer edge of the insulating substrate 1. Applying the adhesive 17 ensures that the case 51 and the outer edge of the insulating substrate 1 are firmly bonded to each other, while reducing the likelihood of sealing resin 6 leaking from the bonding portions between the case 51 and the insulating substrate 1 in the resin sealing step (S20) described above.

[0031] The direct-molding type sealing resin 6 used in the present embodiment has a thermal expansion coefficient (linear expansion coefficient) larger than that of the insulating substrate 1. In the case where the curing shrinkage is sufficiently large, the direct-molding type sealing resin 6 having a thermal expansion coefficient (linear expansion coefficient) equal to or much larger than that of the insulating substrate 1 is also effective.

[0032] Fig. 8 is a schematic sectional view showing a modified example of the Fig. 1. With reference to Fig. 8, the semiconductor device is basically the same structure as that shown in Fig. 1, but differs from the semiconductor device shown in Fig. 1 is that the stepped portion 511 of the housing 51 has a different depth and is elastically deformed in this housing 51 in the present embodiment. In particular, the stepped portion 511 of the housing 51 in the Fig. 8 is configured to have a depth of 3.0 mm. In the mounting step (S30), it is therefore possible to restrain the insulating substrate 1 using the elastic deformation of the housing 51 caused by tightening the screw 52. In this way, it is possible to achieve the same effects as those shown in Fig. 1, and even if the amount of distortion of the insulating substrate 1 varies slightly, it is still possible to stably fix the insulating substrate 1 using the elastic deformation. (Second embodiment)

[0033] Fig. 9 is a schematic cross-sectional view illustrating a semiconductor device according to a second embodiment of the present invention. (Structure of the semiconductor device)

[0034] The semiconductor device according to the second embodiment is basically the same structure as that shown in Fig. 1, but differs from the semiconductor device shown in Fig. 1 is that the portion for fixing the housing 51 and the insulating substrate 1 via the screw 52 is different in configuration. In other words, the housing 51 includes a sleeve portion 53 serving as an overlapping portion that overlaps with the outer edge of the insulating substrate 1 in plan view. The outer edge of the insulating substrate 1 extends under the sleeve portion 53. To describe it in another way, while the stepped portion 511 in the semiconductor device of Fig. 1 is formed within the inner circumference of the sleeve portion 53, the stepped portion 511 is in the semiconductor device shown in Fig. 9, is formed as part of the sleeve portion 53. A through hole is formed to penetrate the sleeve portion 53 and the outer edge of the insulating substrate 1. The screw 52, ​​which serves as a fastening member, is inserted into the through hole and tightened to fix the sleeve portion 53 and the outer edge of the insulating substrate 1 to the cooling device 54.

[0035] The insulation substrate 1 may, for example, be 110 mm in the vertical direction × 70 mm in the horizontal direction × 3 mm in thickness. Similar to the insulation substrate 1 shown in Fig. As shown in FIG. 1, the insulating substrate 1 according to the second embodiment has a multilayer structure in which an epoxy insulating layer 12 and a copper wiring 11 are formed on a copper base 13. The power semiconductor element 3 is disposed on one surface, namely, a first surface, of the insulating substrate 1. As an example of the power semiconductor element 3, it is possible to use the same device as the power semiconductor element 3 in the first embodiment.

[0036] Similar to Fig. In the semiconductor device shown in Figure 1, the power semiconductor element 3 is die-bonded to the copper wiring 11 of the insulation substrate 1 by soldering. The power semiconductor element 3 forms an electrical circuit between the external signal terminal 42 and the external main terminal 43 of the package 51 through the wiring 41 formed by wire bonding.

[0037] Similar to the one in Fig. In the semiconductor device shown in Figure 1, the direct-molding type sealing resin 6 for sealing and insulating the power semiconductor element 3 and the wiring 41 is injected into a region surrounded by the case 51 and the insulation substrate 1 (a region inside the case 51). The sleeve portion 53 of the case 51 is provided with a through-hole for inserting the screw 52 therein. A through-hole 14 is formed in the insulation substrate 1 at a position corresponding to the through-hole. The case 51 and the insulation substrate 1 are fixed to the cooling device 54 by the screw 52. The shape and material of the cooling device 54 may be the same as those shown in Figure 1. Fig. 1. Heat radiation grease 7 is supplied between the insulation substrate 1 and the cooling device 54. Similar to that in the Fig. 1, the heat radiation grease 7 can be obtained, for example, by dispersing a silicon dioxide filler in silicone resin.

[0038] The second surface of the insulating substrate 1, facing the cooling device 54, is distorted into a convex shape. The stepped portion 511 for supporting the outer edge of the insulating substrate 1 is formed at a base part of the sleeve portion 53 located on the inner periphery of the housing 51. As the outer edge is pressed against the cooling device 54 by the stepped portion 511, the second surface of the insulating substrate 1 is distorted into a convex shape, enabling close contact between the insulating substrate 1 and the cooling device 54.

[0039] The depth of the stepped portion 511 for receiving the outer edge of the insulating substrate 1 in the casing 51 is set to be smaller than the sum (for example, 3.1 mm) of the thickness t1 of the insulating substrate 1 (for example, 3 mm) and the amount of distortion of the insulating substrate 1 (for example, 0.1 mm). For example, in the present embodiment, the depth of the stepped portion 511 can be set to 3.0 mm. In this way, it is possible to set the amount of distortion of the insulating substrate 1 from 0.1 mm to substantially zero (almost flat) while holding the insulating substrate 1 so as to be convexly distorted downward (toward the cooling device 54 side).

[0040] The Fig. 9 can produce the same effects as the semiconductor device shown in Fig. 1 is obtained, and by fixing the entire case 51 via a screw inserted into the through hole 14 of the insulating substrate 1, it is possible to stably fix the insulating substrate 1 not only in the thickness direction but also in the vertical and horizontal directions.

[0041] In addition, a protrusion 15 (for example, 0.1 mm in height) is formed on the surface of the insulating substrate 1 in contact with the cooling device 54 at a position outside the through-hole 14. The formation of the protrusion 15 prevents the portion of the insulating substrate 1 around the screw from being reversely distorted (that is, distorted in the opposite direction to the direction in which the central portion of the insulating substrate 1 is distorted into a convex shape toward the power semiconductor element 3) due to the close contact with the cooling device 54. (Manufacturing method of the semiconductor device)

[0042] Although the size and / or shape of the insulation substrate 1 and the housing 51 to be manufactured are different from those used for the Fig. 1, the manufacturing process of the semiconductor device shown in Fig. 9 is basically the same as the manufacturing process of the semiconductor device shown in Fig. 1 shown semiconductor device.

[0043] Although the insulating substrate 1 in each of the embodiments described above includes a copper base 13, the same effect can be obtained as long as the insulating substrate 1 includes a metal plate superior in heat radiation, such as aluminum, as the base. Furthermore, the same effect can be obtained when a ceramic substrate having a base made of materials such as alumina, aluminum nitride, or silicon nitride is used as the insulating substrate 1. In the case where the power semiconductor element 3 to be used radiates a small amount of heat, the same effect can also be obtained when an epoxy glass substrate is used as the insulating substrate 1. Furthermore, the same effect can be obtained by attaching any of these insulating substrates 1 to a heat sink made of copper or aluminum.

[0044] Although aluminum wire bonding is used as the wiring 41 in each of the above-described embodiments, the same effect can be obtained by using copper wire bonding or aluminum tape bonding as the wire 41. Furthermore, the same effect can be obtained by soldering or bonding by ultrasonic waves a busbar-shaped terminal obtained by extending the external terminal of the package 51 onto the surface of the power semiconductor element 3 to the power semiconductor element 3.

[0045] Although in each of the above-described embodiments, a casing made of polyphenylene sulfide (PPS) is used as the casing 51, the same effect can be obtained if the casing 51 is made of a resin material or a liquid crystal polymer superior in heat resistance, such as polybutylene terephthalate (PBT), nylon 6 (PA 6), polyethylene terephthalate (PET), or a mixture of PET and PBT. Further, the external main terminal 43 is configured as a terminal fixed by a nut 44 disposed at a lower part of the external main terminal, and another terminal configured in an alternative manner is applicable. For example, the same effect can be obtained if a straight terminal directly welded to a cable is used as the external main terminal 43.

[0046] Although in each of the above-described embodiments, liquid heat radiation grease 7 is applied by coating to the central part of the cooling device 54, heat radiation grease 7 may be supplied to a desired position by another method. For example, the same effect can be obtained by supplying heat radiation grease 7 to the cooling device 54 by printing or via a dispenser in a desired pattern. Furthermore, the same effect can also be obtained by a process such that a plate-shaped heat radiation plate, which thermally softens when subjected to heating, is interposed between the cooling device 54 and the insulating substrate 1, and a thermal softening treatment is performed thereafter.

[0047] Fig. 10 is a schematic sectional view showing a modified example of the Fig. 9. As shown in Fig. 10, in order to prevent the direct-molding type sealing resin 6 from leaking, applying an adhesive 27 to a contact portion between the insulation substrate 1 and the housing 51 may also be effective. Fig. 10, the semiconductor device is basically the same structure as that shown in Fig. 9, but differs in that adhesive 27 is applied to the contact portion between the case 51 and the insulating substrate 1. The adhesive 27 is applied annularly along the outer edge of the insulating substrate 1 within the through-hole 14 provided in the insulating substrate 1. The application of the adhesive 27 ensures that the case 51 and the outer edge of the insulating substrate 1 are firmly bonded to each other, while reducing the likelihood of the sealing resin 6 leaking from the bonding portions between the case 51 and the insulating substrate 1 in the resin sealing step (S20) described above.

[0048] The direct-molding type sealing resin 6 used in the present embodiment has a thermal expansion coefficient (linear expansion coefficient) larger than that of the insulating substrate 1. In the case where the curing shrinkage is sufficiently large, the direct-molding type sealing resin 6 having a thermal expansion coefficient (linear expansion coefficient) equal to or much larger than that of the insulating substrate 1 is also effective.

[0049] Hereinafter, the characteristic features of the present invention will be described, and some may be duplicated with those described in the above-mentioned embodiments.

[0050] The semiconductor device according to the first embodiment of the present invention includes the insulation substrate 1, a semiconductor element (power semiconductor element 3) arranged on a first surface of the insulation substrate 1, a case 51 connected to the insulation substrate 1 and configured to accommodate the semiconductor element therein, and a resin (direct molding type sealing resin 6) filled in the case 51 to bury the semiconductor element.In the semiconductor device, assuming that the thickness of the insulating substrate 1 is denoted by t1, the thickness of the resin (direct molding type sealing resin 6) is denoted by t2, the linear expansion coefficient of the insulating substrate 1 is denoted by α1, and the linear expansion coefficient of the resin is denoted by α2, the relationship therebetween satisfies t2 ≥ t1 and α2 ≥ α1, and a second surface of the insulating substrate 1 is distorted into a convex shape.

[0051] Therefore, due to the difference between the linear expansion coefficient of the direct-molding type sealing resin 6 to be filled for sealing and the linear expansion coefficient of the insulating substrate 1, it is possible to perform a process to solidify the resin filled in the case 51 to distort the second surface of the insulating substrate 1 into a convex shape. Therefore, before the resin filling step, it is possible to keep the insulating substrate 1 flat. Therefore, wire bonding for bonding or wiring the power semiconductor element 3 to the insulating substrate 1 can be performed on the flat insulating substrate 1 before the resin filling step. This makes it possible to improve the efficiency of operations such asTo improve bonding of the semiconductor element and reduce the probability of occurrence of defective products, and consequently it is possible to obtain semiconductor devices with high reliability.

[0052] Further, since the second surface of the insulating substrate is distorted into the convex shape by the filling and solidification of the resin, for example, when a cooling member (cooling device 54) is bonded to the second surface of the insulating substrate 1 opposite to the first surface thereof, it is possible to prevent voids from being generated between the cooling member and the second surface of the insulating substrate (for example, a central portion of the second surface).

[0053] Furthermore, it is possible to control the coefficient of linear expansion and the thickness of both the resin and the insulation substrate, which makes it possible to control both the distortion direction and the distortion amount of the insulation substrate with perfect reproducibility.

[0054] As in Fig. 1, in the semiconductor device described above, the housing 51 may be provided with an overlapping portion (the portion in the housing 51 of Fig. 1, where the stepped portion 511 is formed) that overlaps with the outer edge of the insulating substrate 1 in plan view, and an extension portion (sleeve portion 53) that extends from the overlapping portion further outward than the outer edge of the insulating substrate 1. The semiconductor device may further include a fastening member (screw 52) configured to fasten the extension portion of the case 51 to a cooling member (cooling device 54) serving as an external member arranged outside the semiconductor device. The stepped portion 511 may be formed in the overlapping portion to accommodate the outer edge of the insulating substrate 1.The depth of the stepped portion 511 may be set smaller than the sum of the thickness t1 of the insulating substrate 1 and the amount of distortion of the insulating substrate 1 in a state where the outer edge of the insulating substrate 1 has not yet been pressed by the stepped portion 511 of the housing 51.

[0055] Consequently, since the outer edge of the insulating substrate 1 is pressed by the stepped portion 511 of the housing 51, the insulating substrate 1 can be securely held by the stepped portion 511 while accurately controlling the amount of distortion of the insulating substrate 1.

[0056] As in Fig. 8, in the semiconductor device described above, the case 51 can be elastically deformed when it is fixed to the external member (cooling device 54) using a fixing member (screw 52) in a state where the outer edge of the insulating substrate 1 is inserted between the overlapping portion and the external member.

[0057] Consequently, even if the amount of distortion of the insulation substrate 1 before the outer edge of the insulation substrate 1 is pressed by the case 51 is larger, the larger amount of distortion of the insulation substrate 1 due to the elastic deformation of the case 51 can be canceled, making it possible to tightly fix the insulation substrate 1 to the external member (cooling device 54).

[0058] As in Fig. 9, in the semiconductor device described above, the housing 51 may be provided with an overlapping portion (the portion where the stepped portion 511 is formed as shown in Fig. 9) which overlaps with the outer edge of the insulating substrate 1 in plan view. A through-hole (the through-hole in the housing 51 and the through-hole 14 in the insulating substrate 1, as shown in Fig. 9) may be formed to penetrate the overlapping portion of the housing 51 and the outer edge of the insulating substrate 1. The semiconductor device may further include a fastening member (screw 52) inserted into the through-hole to fix the outer edge of the insulating substrate 1 and the overlapping portion to an external member (cooling device 54) arranged outside the semiconductor device.

[0059] Consequently, the insulation substrate 1 can be closely fixed to the external member (cooling device 54) together with the housing 51 by the fixing member (screw 52).

[0060] The manufacturing method of a semiconductor device according to an embodiment of the present invention includes a step (the preparation step (S10)) of disposing a semiconductor element (power semiconductor element 3) on a first surface of the insulation substrate 1 and preparing the case 51 that is bonded to the insulation substrate 1 and configured to accommodate the semiconductor element therein, and a step (the resin sealing step (S20)) of filling a resin (direct molding type sealing resin 6) into the case 51 to bury the semiconductor element (power semiconductor element 3) therein.Assuming that the thickness of the insulating substrate 1 is denoted by t1, the thickness of the resin is denoted by t2, the linear expansion coefficient of the insulating substrate 1 is denoted by α1, and the linear expansion coefficient of the resin is denoted by α2, the relationship therebetween satisfies t2 ≥ t1 and α2 ≥ α1, and after the resin filling step (S20), a second surface of the insulating substrate 1 opposite to the first surface thereof is distorted into a convex shape. Furthermore, in the preparation step (S10), it is preferable that the insulating substrate 1 has a smaller amount of distortion (preferably, has a flat shape) than the amount of distortion after the resin filling step.

[0061] Therefore, due to the difference between the linear expansion coefficient of the resin to be filled (direct-molding type sealing resin 6) for sealing and the linear expansion coefficient of the insulating substrate 1, it is possible to perform the step of filling the resin into the case 51 (S20) to distort the second surface of the insulating substrate 1 into a convex shape. Therefore, in the preparation step (S10) before the resin filling step, it is possible to keep the insulating substrate 1 flat. Therefore, all the processes (including the wire bonding process for bonding or wiring the semiconductor element 3 to the insulating substrate 1, and the like) in the preparation step (S10) can be performed on the flat insulating substrate 1.Thereby, it is possible to improve the efficiency of operations in the preparation step (S10) and reduce the probability of occurrence of defective products, and consequently, it is possible to obtain semiconductor devices with high reliability.

[0062] Further, since the second surface of the insulating substrate 1 is distorted into a convex shape by the resin filling step (S20), it is possible to prevent voids from being generated between the cooling member (cooling device 54) and the second surface of the insulating substrate 1 (for example, a central portion of the second surface).

[0063] Furthermore, it is possible to control the linear expansion coefficient and the thickness of both the resin and the insulating substrate 1, which makes it possible to control both the distortion direction and the distortion amount of the insulating substrate 1 with perfect reproducibility.

[0064] The manufacturing method of the semiconductor device may further include a step (the mounting step (S30)) of connecting the second surface of the insulation substrate 1 opposite to the first surface thereof to an external member (cooling device 54 serving as an example of a cooling member) arranged outside the semiconductor device after the resin filling step (S20). In the manufacturing method of the semiconductor device, the housing 51 may be provided with an overlapping portion (the portion shown in Fig. 1, where the stepped portion 511 is formed) that overlaps with the outer edge of the insulating substrate 1 in plan view, and an extension portion (sleeve portion 53) that extends from the overlapping portion farther outward than the outer edge of the insulating substrate 1. The stepped portion 511 may be provided in the overlapping portion to accommodate the outer edge of the insulating substrate 1. The depth of the stepped portion 511 may be set smaller than the sum of the thickness t1 of the insulating substrate 1 and the amount of distortion of the insulating substrate 1 in a state where the outer edge of the insulating substrate 1 has not yet been pressed by the stepped portion 511 of the casing 51. In the connecting step (S30), the extension portion of the housing 51 can be fixed to the external member (cooling device 54) using a fixing member (screw 52).

[0065] Consequently, in the joining step (S30), since the outer edge of the insulating substrate 1 is pressed by the stepped portion 511 of the housing 51, the insulating substrate 1 can be securely held by the stepped portion 511, while accurately controlling the amount of distortion of the insulating substrate 1.

[0066] In the manufacturing process of the semiconductor device, the case 51 can be elastically deformed in the bonding step (S30) when it is fixed to the external member (cooling device 54) using the fixing member (screw 52) in a state where the outer edge of the insulating substrate 1 is inserted between the overlapping portion and the external member (cooling device 54).

[0067] Even if the amount of distortion of the insulating substrate 1 becomes larger in the resin filling step (S20), the larger amount of distortion of the insulating substrate 1 can be canceled due to the elastic deformation of the case 51, making it possible to tightly fix the insulating substrate 1 to the external member.

[0068] The manufacturing method of a semiconductor device may further include a step (assembly step (S30)) of connecting the second surface of the insulation substrate 1 opposite to the first surface thereof to an external member (cooling device 54 serving as an example of the cooling member) arranged outside the semiconductor device after the resin filling step (S20). In the manufacturing method of the semiconductor device, the package 51 may be provided with an overlapping portion (the portion as shown in Fig. 9, in which the stepped portion 511 is formed) which overlaps with the outer edge of the insulating substrate 1 in plan view. A through hole (the through hole in the housing 51 and the through hole 14 in the insulating substrate 1 as shown in Fig. 9) may be formed to penetrate the overlapping portion of the housing 51 and the outer edge of the insulating substrate 1. In the joining step (S30), the fastening member (screw 52) may be inserted into the through hole to fix the overlapping portion and the outer edge of the insulating substrate to the external member.

[0069] Consequently, the insulation substrate 1 can be closely fixed to the external member (cooling device 54) together with the housing 51 by the fixing member (screw 52) in the joining step (S30).

[0070] Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be considered as limiting, the scope of the present invention being interpreted by the terms of the appended claims.

Claims

[1] Semiconductor device comprising: an insulating substrate (1); a semiconductor element (3) arranged on a first surface of the insulating substrate (1); a housing (51) connected to the insulation substrate (1) and configured to accommodate the semiconductor element (3) therein; and a resin (6) filled into the housing (51) to bury the semiconductor element (3), wherein, assuming that the thickness of the insulating substrate (1) is denoted by t1, the thickness of the resin (6) is denoted by t2, the linear expansion coefficient of the insulating substrate (1) is denoted by α1 and the linear expansion coefficient of the resin (6) is denoted by α2, the relationship therebetween t2 ≥ t1 and α2 ≥ α1 is satisfied, the housing (51) is provided with an overlapping portion which overlaps with an outer edge of the insulating substrate (1) in plan view, and an extension portion (53) which extends from the overlapping portion further outward than the outer edge of the insulating substrate (1), the semiconductor device further comprises a fixing member (52) configured to fix the extension portion (53) of the housing (51) to an external member (54) arranged outside the semiconductor device, a heat radiation grease (7) is arranged between the insulation substrate (1) and the external element (54) and the overlapping portion is provided with a stepped portion (511) to accommodate the outer edge of the insulation substrate (1), and the depth of the stepped portion (511) is greater than the sum of the thickness (t1) of the insulating substrate (1) and a thickness of the heat radiation grease (7) in a state in which the extension portion (53) of the housing (51) is fixed to the external member (54) by the fixing member (52), and the depth of the stepped portion (511) is smaller than the sum of the thickness (t1) of the insulating substrate (1) and a degree of distortion of the insulating substrate (1) in a state in which the outer edge of the insulating substrate (1) has not yet been pressed by the stepped portion (511) of the housing (51), and wherein, in the state where the extension portion (53) of the housing (51) is fixed to the external member (54) by the fixing member (52), a second surface of the insulation substrate (1) opposite to the first surface thereof is distorted into a convex shape. [2] The semiconductor device according to claim 1, wherein the package (51) is elastically deformed when it is fixed to the external member using the fixing member (52) in a state where the outer edge of the insulating substrate (1) is inserted between the overlapping portion and the external member. [3] A semiconductor device according to claim 1 or 2, wherein the heat radiation grease (7) has an overlapping area which overlaps with the stepped portion (511) in plan view, and a thickness of the heat radiation grease (7) in the overlapping region is greater than a thickness of the heat radiation grease (7) in a central region of the insulation substrate (1). [4] A method of manufacturing a semiconductor device, comprising: a step (S10) of arranging a semiconductor element (3) on a first surface of an insulating substrate (1) and preparing a housing (51) connected to the insulating substrate (1) and configured to accommodate the semiconductor element (3) therein; and a step (S20) of filling a resin (6) into the housing (51) to bury the semiconductor element (3) therein, wherein, assuming that the thickness of the insulating substrate (1) is denoted by t1, the thickness of the resin (6) is denoted by t2, the linear expansion coefficient of the insulating substrate (1) is denoted by α1 and the linear expansion coefficient of the resin (6) is denoted by α2, the relationship therebetween satisfies t2 ≥ t1 and α2 ≥ α1, and after the step (S20) of filling the resin (6), a second surface of the insulation substrate (1) opposite to the first surface thereof is distorted into a convex shape, wherein the manufacturing process further comprises: a step (S30) of connecting the second surface of the insulation substrate (1) opposite to the first surface thereof to an external member (54) arranged outside the semiconductor device after the step (S20) of filling the resin (6), wherein a heat radiation grease (7) is arranged between the insulation substrate (1) and the external element (54), in the preparation step (S10), the housing (51) is provided with an overlapping portion which overlaps with an outer edge of the insulating substrate (1) in plan view, and an extension portion (53) which extends from the overlapping portion further outward than the outer edge of the insulating substrate (1), wherein the overlapping portion is provided with a stepped portion (511) to accommodate the outer edge of the insulating substrate (1), the depth of the stepped portion (511) is greater than the sum of the thickness (t1) of the insulation substrate (1) and a thickness of the heat radiation grease (7) in a state in which the outer edge of the insulation substrate (1) is pressed by the stepped portion (511) of the housing (51), and the depth of the stepped portion (511) is smaller than the sum of the thickness (t1) of the insulation substrate (1) and a degree of distortion of the insulation substrate (1) in a state in which the outer edge of the insulation substrate (1) has not yet been pressed by the stepped portion (511) of the housing (51), and in the connecting step (S30), the extension portion (53) of the housing (51) is fixed to the external element (54) using a fixing element (52), wherein in a state where the extension portion (53) of the housing (51) is fixed to the external member (54) by the fixing member (52), the second surface of the insulation substrate (1) is distorted into a convex shape. [5] A manufacturing method of a semiconductor device according to claim 4, wherein in the bonding step (S30), the case (51) is elastically deformed when being fixed to the external member using the fixing member (52) in a state where the outer edge of the insulating substrate (1) is interposed between the overlapping portion and the external member. [6] A manufacturing method of a semiconductor device according to claim 4 or 5, wherein the heat radiation grease (7) has an overlapping area which overlaps with the stepped portion (511) in plan view, and a thickness of the heat radiation grease (7) in the overlapping region is greater than a thickness of the heat radiation grease (7) in a central region of the insulation substrate (1).

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