Semiconductor module

Abstract

A semiconductor module (1) is configured such that the surfaces of a core material (5) having a semiconductor element (3) sealed therein is covered with insulating members (7, 9). The semiconductor module (1) includes conductor patterns (11, 13) and recesses (71, 91). The conductor patterns (11, 13) are connected to electrodes (31, 33) of the semiconductor element (3), extend to the outside of the core material (5), and are covered with the insulating members (7, 9). The recesses (71, 91) are formed at sections where the conductor patterns (11, 13) of the insulating members (7, 9) are covered, at a depth such that at least some sections of the conductor patterns (11, 13) extending to the outside of the core material (5) are exposed to the surfaces of the insulating members (7, 9).

Description

Semiconductor Module

[0001] The present invention relates to a semiconductor module.

[0002] Patent Document 1 describes a configuration in which an electrode arranged on one side of a substrate of a semiconductor device is connected to an insulating substrate via a connecting member such as solder or sintered silver, and heat from the electrode is dissipated to a heat sink connected to the insulating member.

[0003] International Publication No. 2020 / 157963

[0004] It is important to maintain the appropriate thickness of the connecting members on the heat dissipation path. If the connecting members are thinner than the appropriate thickness, they will deteriorate faster during cycle testing of the semiconductor device, shortening their test life. If the connecting members are thicker than the appropriate thickness, their thermal resistance will increase and they will not be able to dissipate heat properly. Patent Document 1 only describes simply connecting the electrodes of the substrate and the insulating substrate with connecting members, but does not describe any measures for controlling the thickness of the connecting members.

[0005] An object of the present invention is to accurately control the thickness of a bonding material used for thermal bonding on a heat dissipation path from a semiconductor module to a heat sink.

[0006] A semiconductor module according to one aspect of the present invention that solves the above-mentioned problems is a semiconductor module in which the surface of a core material, inside which a semiconductor element is sealed, is covered with an insulating material. The semiconductor module includes a conductor pattern and a recess. The conductor pattern is connected to an electrode of the semiconductor element, extends outside the core material, and is covered with the insulating material. The recess is formed in the portion of the insulating material covering the conductor pattern, with a depth that exposes at least a portion of the portion of the conductor pattern extending outside the core material on the surface of the insulating material.

[0007] According to the present invention, it is possible to accurately control the thickness of the bonding material used for thermal bonding on the heat dissipation path from the semiconductor module to the heat sink.

[0008] FIG. 1 is a diagram showing the configuration of a semiconductor module according to a first embodiment of the present invention. FIG. 2 is a bottom view of the semiconductor module before a conductor is bonded to the first conductor pattern of FIG. 1. FIG. 3 is a plan view of the semiconductor module before a lead frame is bonded to the second conductor pattern of FIG. 1. FIG. 4 is a diagram showing the configuration of a semiconductor module according to a second embodiment of the present invention. FIG. 5 is a bottom view of the semiconductor module before a conductor is bonded to the first conductor pattern of FIG. 4. FIG. 6 is a plan view of the semiconductor module before a lead frame is bonded to the second conductor pattern of FIG. 4. FIG. 7 is a diagram showing the configuration of a semiconductor module according to a third embodiment of the present invention. FIG. 8 is a bottom view of the semiconductor module before a conductor is bonded to the first conductor pattern of FIG. 7.

[0009] Hereinafter, an embodiment of the present invention and its modifications will be described with reference to the drawings. In the description of the drawings, the same parts are given the same reference numerals and the description thereof will be omitted.

[0010] [First Embodiment] A semiconductor module 1 according to a first embodiment shown in FIG. 1 includes a semiconductor element 3, a core material 5, insulating members 7 and 9, and first and second conductor patterns 11 and 13. The semiconductor module 1 may be, for example, a power semiconductor module. When the semiconductor module 1 is a power semiconductor module, the semiconductor element 3 may be, for example, a power semiconductor element. The power semiconductor element may be, for example, a power switching element such as a metal oxide semiconductor field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT). The power semiconductor element may be, for example, a power rectifying semiconductor element such as a diode. The semiconductor module 1 may include multiple semiconductor elements 3 connected in series or in parallel. The multiple semiconductor elements 3 may be, for example, a power switching element and a power rectifying semiconductor element connected in anti-parallel. FIG. 1 illustrates a case in which the semiconductor module 1 includes a single semiconductor element 3. The semiconductor element 3 includes a first electrode 31 and a second electrode 33. The first electrode 31 and the second electrode 33 can be used, for example, as a cathode electrode and an anode electrode of the semiconductor element 3. The semiconductor element 3 may further have, for example, a control electrode (not shown) of a power switching element, an electrode (not shown) such as a diode for measuring the temperature or current of the semiconductor element 3, or the like.

[0011] The core material 5 is formed in a flat plate shape from an insulating material such as glass epoxy resin, which is glass fiber impregnated with epoxy resin. The surface of the core material 5 has a first surface 51 and a second surface 53 facing each other, and a through hole 55 that penetrates between the first surface 51 and the second surface 53. The semiconductor element 3 is disposed inside the through hole 55 with the first electrode 31 facing the first surface 51 and the second electrode facing the second surface 53. The semiconductor element 3 is sealed inside the through hole 55 by an insulating sealing resin 4. The sealing resin 4 can be made of, for example, a nanocomposite insulating material.

[0012] The first conductor pattern 11 is arranged on the first surface 51 side of the core material 5. The first conductor pattern 11 has a connecting conductor 15. The connecting conductor 15 is electrically and thermally connected to the first electrode 31 of the semiconductor element 3 inside the through hole 55. The portion of the first conductor pattern 11 other than the connecting conductor 15 extends outward in the penetration direction of the through hole 55. The second conductor pattern 13 is arranged on the second surface 53 side of the core material 5. The second conductor pattern 13 has a connecting conductor 17. The connecting conductor 17 is electrically and thermally connected to the second electrode 33 of the semiconductor element 3 inside the through hole 55. The portion of the second conductor pattern 13 other than the connecting conductor 17 extends outward from the core material 5 in the penetration direction of the through hole 55. A portion of the second conductor pattern 13 extends outward from the opening of the through hole 55 and abuts against the second surface 53 of the core material 5.

[0013] The first and second conductor patterns 11, 13 may be made of a metal such as copper. The first and second conductor patterns 11, 13 may be formed by plating, for example. If the first and second conductor patterns 11, 13 are made of a metal different from that of the first electrodes 31 and second electrodes 33 electrically connected to the first and second conductor patterns 11, 13, the first and second conductor patterns 11, 13 may be plated with the same metal as the first electrodes 31 and second electrodes 33. The first electrodes 31 and second electrodes 33 may also be plated with the same metal as the first and second conductor patterns 11, 13. The connecting conductors 15, 17 of the first and second conductor patterns 11, 13 may be formed integrally with portions other than the connecting conductors 15, 17 of the first and second conductor patterns 11, 13. The connecting conductors 15, 17 may be formed as vias or through holes formed in the sealing resin 4 by metal plating and electrically and thermally connected to the first and second conductor patterns 11, 13. The connecting conductors 15, 17 may be connected to the entire first electrode 31 and the entire second electrode 33 by full-surface plating, or may be electrically connected individually to each of the first electrode 31 and the second electrode 33 by solder, wax, etc.

[0014] The insulating members 7 and 9 are used for interlayer insulation and are formed on the first surface 51 and the second surface 53, respectively, of the core material 5 in which the semiconductor element 3 is sealed. The first and second conductor patterns 11 and 13 on the first surface 51 and the second surface 53 are covered by the insulating members 7 and 9. The insulating members 7 and 9 may be made of, for example, the same material as the sealing resin 4, or a different material from the sealing resin 4. Recesses 71 and 91 are formed in the insulating members 7 and 9, respectively. The recesses 71 and 91 can be formed in the insulating members 7 and 9 by, for example, laser irradiation or drill cutting. The recess 71 is formed in a portion of the insulating member 7 that covers the first conductor pattern 11. The recess 91 is formed in a portion of the insulating member 9 that covers a portion of the second conductor pattern 13 that extends beyond the opening of the through hole 55. The recesses 71 and 91 are formed to a depth that reaches the first and second conductor patterns 11 and 13 from the surfaces of the insulating members 7 and 9. As shown in Figures 2 and 3, the recesses 71, 91 expose at least a portion of the portions of the first and second conductor patterns 11, 13 covered with the insulating members 7, 9 to the surfaces of the insulating members 7, 9. The openings 73, 93 of the recesses 71, 91 formed in the insulating members 7, 9 have a shape that does not include any right-angled or acute-angled interior corners. Figures 2 and 3 show the case where the openings 73, 93 are octagonal, with the four corners of a quadrangle chamfered. When the openings 73, 93 are octagonal, all of the eight interior angles of the openings 73, 93 are greater than right angles.

[0015] 1, the semiconductor module 1 of this embodiment has insulating members 7 and 9, recesses 71 and 91, and first and second conductor patterns 11 and 13 on each of a first surface 51 side and a second surface 53 side that face each other across the semiconductor element 3 of the core material 5. The semiconductor module 1 may have, on only one of the first surface 51 side and the second surface 53 side, an insulating member, a recess in the insulating member, and a conductor pattern at least a part of which is exposed on the surface of the insulating member by the recess.

[0016] A conductor 21 serving as a joining target is joined to the first conductor pattern 11 by a joining material 19. A lead frame 25 serving as a joining target is joined to the second conductor pattern 13 by a joining material 23. A conductor having a different form from the lead frame 25, such as a wire or ribbon, may be joined to the second conductor pattern 13 as a joining target. The conductor 21 is thermally connected to the first conductor pattern 11 for heat dissipation from the semiconductor element 3. When a conductor such as a lead frame (not shown) is electrically connected to the conductor 21 to provide a wiring path for the semiconductor element 3 on the first surface 51 side of the core material 5, the conductor 21 is also electrically connected to the first conductor pattern 11. The conductor 21 may be made of a metal such as copper, aluminum, or a copper-molybdenum alloy, or may be made of a metal integrated with an insulator such as ceramic or resin. By thermally connecting a cooler or the like (not shown) to the conductor 21, a heat dissipation path for the semiconductor element 3 can be formed on the first surface 51 side of the core material 5. The lead frame 25 is electrically connected to the second conductor pattern 13 to support the semiconductor element 3 and electrically connect the semiconductor module 1 to external wiring (not shown). The lead frame 25 may be made of, for example, copper, aluminum, or a clad material of copper and another metal. One end of the lead frame 25 is electrically connected to the second electrode 33 of the semiconductor element 3, and the other end of the lead frame 25 protrudes outside the insulating member 9 and is exposed on the surface of the insulating member 9. The other end of the lead frame 25 may be connected to an object to which power is supplied from a power conversion device using the semiconductor module 1. The object to which power is supplied may include, for example, a load that consumes the supplied power, such as a smoothing capacitor of a rectifier circuit, a battery, a motor, or a reactor. The lead frame 25 may have a plated surface. A cooler or the like (not shown) may be thermally connected to the lead frame 25 via an insulator to form an additional heat dissipation path for the semiconductor element 3 on the second surface 53 of the core material 5.

[0017] The bonding materials 19, 23 may be, for example, solder or brazing filler, or may be a paste material such as copper or silver for sinter bonding. In this embodiment, a case where solder is used as the bonding materials 19, 23 will be described. The first and second conductor patterns 11, 13, the conductor 21, and the lead frame 25 can be soldered by, for example, reflow soldering. During reflow soldering, solder paste having a cross-sectional area smaller than the opening of the recesses 71, 91 and a height greater than the depth of the recesses 71, 91 is placed in the recesses 71, 91 of the insulating members 7, 9. After the solder paste is placed, the solder paste is heated while pressing the conductor 21 and the lead frame 25 toward the insulating members 7, 9. The thickness of the bonding material 19 between the first conductor pattern 11 and the conductor 21 and the thickness of the bonding material 23 between the second conductor pattern 13 and the lead frame 25 are controlled by the depth of the recesses 71, 91 of the insulating members 7, 9. The lead frame 25 may have a through hole (not shown) that discharges excess bonding material 23 that exceeds the volume of the recess 91 to the outside of the recess 91 when the lead frame 25 is pressed against the insulating member 9. A structure similar to this through hole may be provided in the conductor 21.

[0018] As shown in FIGS. 2 and 3 , second positioning portions 75 and 95 are formed around the openings 73 and 93 of the recesses 71 and 91 of the insulating members 7 and 9, respectively. The outer sides of the second positioning portions 75 and 95 are higher in the depth direction of the recesses 71 and 91 than the inner sides of the second positioning portions 75 and 95, where the openings 73 and 93 of the recesses 71 and 91 are located. The second positioning portions 75 and 95 have positioning walls formed by a step between the outer and inner sides. The positioning walls exist on at least two parallel sides and one side intersecting these two sides. During reflow, at least three sides of the conductor 21 abut against the positioning walls of the second positioning portions 75 of the insulating member 7, and at least three sides of the lead frame 25 abut against the positioning walls of the second positioning portions 95 of the insulating member 9. The conductor 21 is positioned relative to the first conductor pattern 11 in a direction along the surface of the insulating member 7 by abutting against the second positioning portions 75. The lead frame 25 is positioned relative to the second conductor pattern 13 in a direction along the surface of the insulating member 9 by abutting against the second positioning portions 95. Portions of the surfaces of the insulating members 7, 9 that are inside the second positioning portions 75, 95 form first positioning portions 77, 97. As shown in FIG. 1 , during reflow, the conductor 21 and lead frame 25, which are pressed toward the insulating members 7, 9, abut against the first positioning portions 77, 97. The conductor 21 is positioned relative to the first conductor pattern 11 in the depth direction of the recess 71 by abutting against the first positioning portions 77. The lead frame 25 is positioned relative to the second conductor pattern 13 in the depth direction of the recess 91 by abutting against the first positioning portions 97.

[0019] The semiconductor module 1 can be manufactured, for example, by the following steps (a) to (e). In step (a), a semiconductor element 3 is placed inside a through hole 55 in a core material 5, and the periphery of the semiconductor element 3 in the through hole 55 is sealed with a sealing resin 4. Holes are formed in the sealing resin 4 that has sealed the through hole 55 to form the connection conductors 15, 17 of the first and second conductor patterns 11, 13. The holes can be formed, for example, by laser irradiation or drill cutting. The connection conductors 15, 17 are formed in the formed holes by metal plating or the like, and then the portions of the first and second conductor patterns 11, 13 other than the connection conductors 15, 17 are formed. In step (b), insulating members 7, 9 are formed on the first and second surfaces 51, 53 of the core material 5 with the semiconductor element 3 sealed therein, from above the first and second conductor patterns 11, 13. The thicknesses of the insulating members 7, 9 formed on the first surface 51 and the second surface 53 are set to a thickness necessary to control the thickness of the bonding materials 23, 25 based on the depth of recesses 71, 91 formed in the insulating members 7, 9 in a later step. In step (c), the recesses 71, 91 and the second positioning portions 75, 95 are formed on the surfaces of the insulating members 7, 9, for example, by laser irradiation or drill cutting. In step (d), the solder paste placed in the recesses 71, 91 is used to reflow soldering to bond the first conductor pattern 11 and the conductor 21 with the bonding material 19, and to bond the second conductor pattern 13 and the lead frame 25 with the bonding material 23. During reflow soldering, the second positioning portion 75 positions the conductor 21 relative to the first conductor pattern 11, and the second positioning portion 95 positions the lead frame 25 relative to the second conductor pattern 13. Pressurizing the positioned conductor 21 and lead frame 25 and heating the solder paste causes the molten solder to wet and spread, filling the recesses 71, 91 blocked by the conductor 21 and lead frame 25. Before step (d), a resist material may be formed on the surfaces of the insulating members 7, 9. This resist material helps to prevent the reflowed molten solder from unnecessarily wetting and spreading from the recesses 71, 91 onto the surfaces of the insulating members 7, 9. In step (e), the reflowed molten solder is cooled and solidified, completing the bonding of the first conductor pattern 11 and conductor 21 by the bonding material 19 and the bonding of the second conductor pattern 13 and lead frame 25 by the bonding material 23.

[0020] 1 to 3, the outside of the core material 5 in the direction along the first surface 51 and the second surface 53 may be sealed with resin. The outside of the conductor 21 in the direction along the first surface 51 and the second surface 53 may further be sealed with resin. The semiconductor module 1 in which the conductor 21 and the lead frame 25 are joined may be housed in a case (not shown) to which terminals (not shown) that are electrically connected to at least one of the conductor 21 and the lead frame 25 may be fixed. When the semiconductor module 1 is housed in a case, the inside of the case may be filled with resin, and the outside of the core material 5 and the conductor 21 may be sealed with the filled resin.

[0021] In the semiconductor module 1 of this embodiment, the portions of the first and second conductor patterns 11 and 13 extending outside the core material 5 are bonded to the bonding targets on the surfaces of the insulating members 7 and 9 by bonding materials 19 and 23 disposed in the recesses 71 and 91 of the insulating members 7 and 9. The thickness of the bonding materials 19 and 23 in the depth direction of the recesses 71 and 91 is controlled by the depth of the recesses 71 and 91. When cycle tests such as a power cycle test and a temperature cycle test are performed, the semiconductor module 1 repeatedly expands and compresses, and thermal stress is applied to the bonding materials 19 and 23 due to differences in the thermal contraction rates of the materials constituting the semiconductor module 1. If the bonding materials 19 and 23 are thinner than appropriate, their durability against thermal stress decreases, shortening their cycle life. If the bonding materials 19 and 23 are thicker than appropriate, the thermal resistance of the bonding materials 19 and 23 increases unnecessarily, reducing the heat dissipation performance of the semiconductor module 1. In this embodiment, the thickness of the bonding materials 19, 23 used to bond the first and second conductor patterns 11, 13 to the conductor 21 and the lead frame 25 on the heat dissipation path from the semiconductor element 3 of the semiconductor module 1 to the heat sink can be controlled with precision.

[0022] In this embodiment, the openings 73, 93 of the recesses 71, 91 are octagonal, and all eight interior angles of the openings 73, 93 are greater than a right angle. Because the openings 73, 93 have a shape that does not have any corners where the interior angles are right angles or acute angles, stress concentration is prevented from occurring in the bonding materials 19, 23 filled and solidified in the recesses 71, 91 near the corners of the openings 73, 93. During a cycle test of the semiconductor module 1, thermal stress applied to the bonding materials 19, 23 is prevented from concentrating at specific locations, thereby preventing a shortened cycle test life of the bonding materials 19, 23.

[0023] In this embodiment, the semiconductor module 1 has recesses 71, 91 on the first surface 51 side and the second surface 53 side of the core material 5 that expose the insulating members 7, 9, the first and second conductor patterns 11, 13, and at least a portion of the first and second conductor patterns 11, 13. The recesses 71, 91 are formed on the first surface 51 side and the second surface 53 side of the core material 5, respectively, and on the first surface 51 side of the core material 5, the first conductor pattern 11 extending outside the core material 5 is joined to the conductor 21 by a bonding material 19. On the second surface 53 side of the core material 5, the second conductor pattern 13 extending outside the core material 5 is joined to the lead frame 25 by a bonding material 23. When the first and second conductor patterns 11, 13 are joined to the conductor 21 and the lead frame 25 on the first surface 51 side and the second surface 53 side of the core material 5, the thickness of the joining materials 19, 23 can be precisely controlled on each surface 51, 53 side.

[0024] In the present embodiment, when the conductor 21 and the lead frame 25 are joined to the first and second conductor patterns 11 and 13 with the bonding materials 19 and 23, the conductor 21 and the lead frame 25 abut against the first positioning portions 77 and 97 of the insulating members 7 and 9. The conductor 21 and the lead frame 25 abutting against the first positioning portions 77 and 97 are positioned in the depth direction of the recesses 71 and 91 with respect to the first and second conductor patterns 11 and 13. By positioning the conductor 21 and the lead frame 25 in the depth direction of the recesses 71 and 91, it is possible to prevent the accuracy of the thickness of the bonding materials 19 and 23 from decreasing due to misalignment of the conductor 21 and the lead frame 25.

[0025] In the present embodiment, when the conductor 21 and the lead frame 25 are joined to the first and second conductor patterns 11 and 13 with the bonding materials 19 and 23, the conductor 21 and the lead frame 25 abut against the second positioning portions 75 and 95 of the insulating members 7 and 9. The conductor 21 and the lead frame 25 abutting against the second positioning portions 75 and 95 are positioned relative to the first and second conductor patterns 11 and 13 in a direction along the surfaces of the insulating members 7 and 9. Positioning the conductor 21 and the lead frame 25 in a direction along the surfaces of the insulating members 7 and 9 can prevent problems related to the conductor 21 and the lead frame 25 from occurring due to misalignment of the conductor 21 and the lead frame 25. Specifically, for example, it can prevent an increase in the electrical resistance and thermal resistance of the bonding materials 19 and 23 connected to the conductor 21 and the lead frame 25, and prevent short-circuiting between the first and second conductor patterns 11 and 13 and the conductor 21 and the lead frame 25 at points other than the joint locations.

[0026] Second Embodiment A semiconductor module 1-1 of a second embodiment shown in FIG. 4 differs from the semiconductor module 1 of the first embodiment shown in FIG. 1 in that a thickness adjustment portion 99 is formed outside the second positioning portion 95 of the insulating member 9 in the depth direction of the recess 91. In this embodiment, the thickness adjustment portion 99 is formed over the entire outside of the second positioning portion 95. The thickness adjustment portion 99 can be formed on the surface of the insulating member 9 together with the recess 91 and the second positioning portion 95, for example, by laser irradiation or drill cutting in step (c) of the manufacturing procedure for the semiconductor module 1 described in the first embodiment. The portion of the insulating member 9 where the thickness adjustment portion 99 is formed is larger than the first and second positioning portions 97, 95 of the insulating member 9 and accounts for the majority of the insulating member 9. Due to the formation of the thickness adjustment portion 99, the thickness of the recess 91 of the insulating member 9 in the depth direction is the same as the thickness of the recess 71 of the majority of the insulating member 7, excluding the second positioning portion 75, in the depth direction of the recess 71. As shown in FIGS. 5 and 6 , in the second embodiment, the opening 73 of the recess 71 has a circular or elliptical shape. Similar to the octagonal shape of the openings 73 and 93 in the first embodiment, the circular or elliptical shape has no right or acute interior corners. As shown in FIG. 5 , the insulating member 7 further includes a recess 79 that bulges outward from the opening 73 in a direction along the surface of the insulating member 7 and communicates with the recess 71. The recess 79 can be formed, for example, by laser irradiation or drilling. The recess 79 may be communicated with the recess 71 over the entire depth of the recess 71, or may be communicated with only a portion of the depth of the recess 71. The recess 79 may be formed from the surface of the insulating member 7 so as to constitute a portion of the opening 73, or may be formed only on the deeper side of the recess 71 in the depth direction than the opening 73.

[0027] In the second embodiment, most of the insulating members 7, 9 have the same thickness in the depth direction of each recess 71, 91, so that the same magnitude of internal stress is generated in most of the insulating members 7, 9. The magnitude of the stresses applied by the insulating members 7, 9 to the first surface 51 and the second surface 53 of the core material 5 is balanced, so that warping of the core material 5 due to the difference in stress applied to each surface 51, 53 can be suppressed.

[0028] In the second embodiment, the openings 73, 93 also have a shape that does not include any right or acute interior corners, which prevents the occurrence of areas where stress concentrates near the openings 73, 93 of the solidified bonding materials 19, 23 in the recesses 71, 91. During cycle tests such as a power cycle test and a temperature cycle test of the semiconductor module 1-1, it is possible to prevent the cycle test life of the bonding materials 19, 23 from being shortened due to the areas where stress concentrates in the bonding materials 19, 23 in the recesses 71, 91.

[0029] In the second embodiment, in a reflow process for joining the first conductor pattern 11 and the conductor 21 with the bonding material 19 in the recess 71, when the conductor 21 is pressed toward the insulating member 7, excess bonding material 19 that exceeds the volume of the recess 71 and cannot be accommodated in the recess 71 flows into the relief portion 79. Because the excess bonding material 19 flows into the relief portion 79, it is possible to prevent the excess bonding material 19 from overflowing from the opening 73 of the recess 71 and increasing the thickness of the bonding material 19 in the depth direction of the recess 71 beyond the expected thickness.

[0030] 7 , a through hole 57 is added to the core material 5. The second conductor pattern 13 is integrally formed with a connection conductor 14 that passes through the through hole 57 from the second surface 53 side to the first surface 51 side, and a third conductor pattern 16 that is arranged on the first surface 51 side of the core material 5 and continues to the connection conductor 14. The third conductor pattern 16 extends outward in the penetration direction of the through hole 57. The third conductor pattern 16 has a thickness greater than that of the first conductor pattern 11 in the penetration direction of the through holes 55, 57. The first conductor pattern 11 and the third conductor pattern 16 on the first surface 51 side of the core material 5 are covered with an insulating member 7.

[0031] In the third embodiment, the insulating member 7 has a recess 72 in addition to the recess 71. The recess 72 can be formed in the insulating member 7 by, for example, laser irradiation or drill cutting. The recess 72 is formed in a portion of the insulating member 7 covering the third conductor pattern 16, with a depth that reaches the third conductor pattern 16 from the surface of the insulating member 7. The third conductor pattern 16 has a different thickness in the penetration direction of the through holes 55 and 57 from the first conductor pattern 11, which is disposed on the first surface 51 of the core material 5, like the third conductor pattern 16. As shown in FIG. 8 , the recess 72 exposes at least a portion of the portion of the third conductor pattern 16 covered by the insulating member 7 to the surface of the insulating member 7. The opening 74 of the recess 72 formed in the insulating member 7 has a shape that does not include any right or acute interior corners. FIG. 8 shows a case where the opening 74 is octagonal. All eight interior angles of the octagonal opening 74 are greater than a right angle.

[0032] As shown in FIG. 7 , a conductor 22, which is a joining target, is connected to the third conductor pattern 16 by a bonding material 20. The conductor 22 is thermally connected to the third conductor pattern 16 to dissipate heat from the second electrode 33 of the semiconductor element 3. Like the conductor 21, the conductor 22 may be made of metal, or may be made of an insulator and a metal integrated together. A cooler (not shown) thermally connected to the conductor 21 can also be thermally connected to the conductor 22. The bonding material 20 may be the same as the bonding materials 19 and 23, for example. In this embodiment, solder is used as the bonding material 20, and the third conductor pattern 16 and the conductor 22 are soldered by reflow. During reflow, a solder paste having a cross-sectional area smaller than the opening of the recess 72 and a height greater than the depth of the recess 72 is placed in the recess 72. After the solder paste is placed, the solder paste is heated while pressing the conductor 22 toward the insulating member 7. The thickness of the bonding material 20 between the third conductor pattern 16 and the conductor 22 is controlled by the depth of the recess 72 in the insulating member 7. The conductor 22 may have a through hole (not shown) that discharges excess bonding material 20 that exceeds the volume of the recess 72 to the outside of the recess 72 when the conductor 22 is pressed against the insulating member 7.

[0033] As shown in FIG. 8 , a second positioning portion 76 is formed around the opening 74 of the insulating member 7, separating the area so as not to overlap with the second positioning portion 75. The outer side of the second positioning portion 76 is one step higher in the depth direction of the recess 72 than the inner side of the second positioning portion 76 where the opening 74 of the recess 72 is located. The second positioning portion 76 has positioning walls formed by a step between the outer side and the inner side. The positioning walls exist on at least two parallel sides and one side intersecting these two sides. During reflow, at least two sides of the conductor 22 abut against the positioning walls of the second positioning portion 76, and the conductor 21 is positioned relative to the third conductor pattern 16 in a direction along the surface of the insulating member 7. The portion of the surface of the insulating member 7 inside the second positioning portion 76 constitutes a first positioning portion 78. As shown in FIG. 7 , during reflow, the conductor 22 pressed toward the insulating member 7 abuts against the first positioning portion 78. The conductor 22 is positioned in the depth direction of the recess 72 relative to the third conductor pattern 16 by contacting the first positioning portion 78 .

[0034] When manufacturing the semiconductor module 1-2 of the third embodiment, for example, in step (a) of the manufacturing procedure for the semiconductor module 1 described in the first embodiment, the through hole 57 of the core material 5 is sealed with the sealing resin 4. In step (a), a hole for forming the connecting conductor 14 is formed in the sealing resin 4 sealing the through hole 57, for example, by laser irradiation or drilling. The connecting conductor 14 is formed in the hole formed in the sealing resin 4 for the through hole 57 by metal plating or the like, and further, a portion of the third conductor pattern 16 is formed. In step (b), an insulating member 7 is formed on the first surface 51 of the core material 5, from above the first and third conductor patterns 11 and 16. The insulating member 7 has a thickness that takes into consideration the thickness of the bonding material 20 being controlled by the depth of a recess 72 formed in the insulating member 7 in a later step. In step (c), the recess 72 and the first positioning portion 78 are formed on the surface of the insulating member 7, for example, by laser irradiation or drilling. In step (d), the solder paste placed in the recess 72 is used to reflow and bond the third conductor pattern 16 and the conductor 22 with the bonding material 20. During reflow, the second positioning portion 76 positions the conductor 22 relative to the third conductor pattern 16 in a direction along the surface of the insulating member 7. Pressurization of the positioned conductor 22 and heating of the solder paste causes the molten solder to wet and spread, filling the recess 72 blocked by the conductor 22.

[0035] In this embodiment, the third conductor pattern 16 is bonded to the conductor 22 by the bonding material 20. The thickness of the bonding material 20 in the depth direction of the recess 72 is controlled by the depth of the recess 72. The thickness of the bonding material 20 used to bond the third conductor pattern 16 to the conductor 22 can be controlled with precision along the heat dissipation path from the second electrode 33 of the semiconductor element 3 of the semiconductor module 1-2 to the heat sink. The opening 74 of the recess 72 is octagonal, and all eight interior angles of the opening 74 are greater than a right angle. This prevents stress from concentrating in areas near the corners of the opening 74 in the bonding material 20 that has been filled and solidified in the recess 72. This prevents stress generated during a cycle test of the semiconductor module 1-2 from concentrating in specific areas of the bonding material 20, thereby preventing a shortened cycle test life of the bonding material 20.

[0036] In the present embodiment, when the conductor 22 is bonded to the third conductor pattern 16 with the bonding material 20, the conductor 22 abuts against the first positioning portion 78 and the second positioning portion 76 of the insulating member 7. The conductor 22 abutting against the first positioning portion 78 is positioned relative to the third conductor pattern 16 in the depth direction of the recess 72, and the conductor 22 abutting against the second positioning portion 76 is positioned relative to the third conductor pattern 16 in a direction along the surface of the insulating member 7. Positioning the conductor 22 in the depth direction of the recess 72 can prevent a decrease in the accuracy of the thickness of the bonding material 20 due to misalignment of the conductor 22 or a malfunction related to the conductor 22 due to misalignment of the conductor 22. Malfunctions of the conductor 22 include, for example, an increase in the electrical resistance or thermal resistance of the conductor 22, and a short circuit between the third conductor pattern 16 and the conductor 22.

[0037] In this embodiment, the thicknesses of the first and third conductor patterns 11 and 16 are different on the first surface 51 side of the core material 5 in the penetration direction of the through holes 55 and 57. Recesses 71 and 72, which are formed to a depth from the surface of the insulating member 7 to reach the first and third conductor patterns 11 and 16, respectively, have different depths corresponding to the thicknesses of the first and third conductor patterns 11 and 16, respectively. Conductors 21 and 22 are bonded to the first and third conductor patterns 11 and 16, respectively, by bonding materials 19 and 20. The thicknesses of the bonding materials 19 and 20 are controlled by the recesses 71 and 72 to a thickness corresponding to the first conductor pattern 11 and a thickness corresponding to the third conductor pattern 16 for each bonding material 19 and 20. The thicknesses of the bonding materials 19 and 20 in the depth direction of the recesses 71 and 72 can be controlled individually for each of the first and third conductor patterns 11 and 16 to which the conductors 21 and 22 are bonded by the bonding materials 19 and 20.

[0038] [Modifications] In the above embodiment, the outer sides of the second positioning portions 75, 76, 95 are one step higher than the inner sides in the depth direction of the recesses 71, 72, 91, but the heights of the inner and outer sides of the second positioning portions 75, 76, 95 may be reversed. In this case, the conductors 21, 22 and the lead frame 25 are positioned by abutting the outer sides of the second positioning portions 75, 76, 95 against a positioning wall formed by a step between the outer sides of the second positioning portions 75, 76, 95. The second positioning portions 75, 76, 95 can be realized by any known configuration, such as by the above-mentioned step, or by recesses or protrusions that can engage with protrusions or recesses of the conductors 21, 22 and the lead frame 25.

[0039] In the above embodiment, the case where one semiconductor element 3 is encapsulated inside the core material 5 has been described. However, the present invention is also applicable to the case where two or more semiconductor elements 3 are encapsulated inside the core material 5. For example, when two or more semiconductor elements 3 are electrically connected by the first conductor pattern 11 on the first surface 51 side of the core material 5, the first conductor pattern 11 is formed to a size that covers all of the two or more semiconductor elements 3. The recess 71 of the insulating member 7 can be formed, for example, so that the portion of the first conductor pattern 11 that covers all of the semiconductor elements 3 is exposed on the surface. When some electrodes of the semiconductor element 3 are separated from the first electrode 31 or the second electrode 33 and the separated electrodes are connected to a dedicated conductive pattern, a recess that exposes at least a portion of the dedicated conductive pattern on the surface is newly provided in the insulating members 7 and 9. By applying the same shape as the recesses 71, 72, and 91 to the opening of this recess, the same effect as in the above embodiment can be obtained for a bonding material that bonds a bonding object to a dedicated conductive pattern.

[0040] In the above embodiment, for example, unevenness may occur in the joint portions of the first, second, and third conductor patterns 11, 13, and 16 due to "sink marks" that occur during the formation of the first, second, and third conductor patterns 11, 13, and 16. Even in this case, by controlling the thickness of the bonding materials 19, 20, and 23 based on the depth of the corresponding recesses 71, 72, and 91, it is possible to form bonding materials 19, 20, and 23 with a thickness that adheres closely to the entire surface of the joint portions of the first, second, and third conductor patterns 11, 13, and 16 that have unevenness.

[0041] In the above embodiments, the semiconductor modules 1, 1-1, and 1-2 have a dedicated core material 5 that functions as a core material encapsulating the semiconductor element 3 therein. The semiconductor module does not need to have a dedicated core material, and an element other than the core material that constitutes the semiconductor module may also function as a core material encapsulating the semiconductor element therein. In the above embodiments, the second positioning portions 75, 76, and 95 have positioning walls against which at least three sides of the conductor 21 and lead frame 25, which are the bonding targets of the first, second, and third conductor patterns 11, 13, and 16, abut. The second positioning portions 75, 76, and 95 may be configured so that one side or multiple sides other than the three sides of the bonding targets abut against the positioning walls, thereby positioning the bonding targets in a direction along the surfaces of the insulating members 7 and 9.

[0042] The above-described embodiment is merely an example of the present invention, and therefore the present invention is not limited to the above-described embodiment, and various modifications can be made to the design and other aspects of the present invention without departing from the technical concept of the present invention.

[0043] REFERENCE SIGNS LIST 1, 1-1, 1-2 Semiconductor module 3 Semiconductor element 5 Core material 7, 9 Insulating member 11 First conductor pattern 13 Second conductor pattern 16 Third conductor pattern 19, 20, 23 Bonding material 21, 22 Conductor (bonding object) 25 Lead frame (bonding object) 51 First surface (surface of core material) 53 Second surface (surface of core material) 71, 72, 91 Recess 73, 74, 93 Opening 75, 76, 95 Second positioning portion 77, 78, 97 First positioning portion 79 Relief portion

Claims

1. A semiconductor module in which the surface of a core material inside which a semiconductor element is sealed is covered with an insulating material, comprising: a conductor pattern connected to an electrode of the semiconductor element, extending outside the core material and covered with the insulating material; and a recess formed in the part of the insulating material covering the conductor pattern, with a depth that exposes at least a part of the part of the conductor pattern extending outside the core material on the surface of the insulating material.

2. The semiconductor module according to claim 1, wherein the recess has an opening in the insulating member, and the opening has a shape that does not have any right or acute interior corners.

3. A semiconductor module as described in claim 1 or 2, wherein the surface of the core material has a first surface and a second surface that face each other across the semiconductor element, and the insulating member, the conductor pattern, and the recess are provided on each of the first surface side and the second surface side of the core material.

4. The semiconductor module according to claim 3, wherein the insulating member on the first surface side and the insulating member on the second surface side have the same thickness in the depth direction of the recess formed therein.

5. A semiconductor module according to any one of claims 1 to 4, wherein the insulating member has a first positioning portion, and the object to be joined to the portion of the conductor pattern exposed on the surface of the insulating member by the recess abuts against the first positioning portion and is positioned in the depth direction of the recess relative to the conductor pattern.

6. A semiconductor module according to any one of claims 1 to 5, wherein the insulating member has a second positioning portion, and the object to be joined to the portion of the conductor pattern exposed on the surface of the insulating member by the recess abuts against the second positioning portion and is positioned relative to the conductor pattern in a direction along the surface of the insulating member.

7. A semiconductor module according to any one of claims 1 to 6, wherein the recess has an opening in the insulating member, and further comprises a relief portion formed in the insulating member that bulges outward from the opening in a direction along the surface and communicates with the recess.

8. A semiconductor module according to any one of claims 1 to 7, wherein a plurality of the conductor patterns are covered with one of the insulating members, and a plurality of the recesses having depths corresponding to the respective conductor patterns are formed in one of the insulating members.

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