semiconductor devices

Abstract

A semiconductor device comprises a semiconductor element (1), a lead frame (30), a bridging member (51) and a sealing resin (7). The semiconductor element has a first electrode (14) exposed on one side and a second electrode (12) exposed on the opposite side of the one side. The lead frame includes a mounting portion (32) for mounting the semiconductor element and electrically connected to the first electrode, and a non-mounting portion (31) separated from the mounting portion. The bridging member is conductive and electrically connects the second electrode to the non-mounting portion. The sealing resin has electrical insulation properties and a thermal conductivity of 2.2W or more, and covers the semiconductor element, the lead frame and the bridging member with the opposite side (S11) of the mounting surface of the mounting portion exposed.

Description

[0001] Cross-references between related applications

[0002] This application is based on Japanese Patent Application No. 2019-128732 filed on July 10, 2019, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to semiconductor devices. Background Art

[0004] Patent Document 1 describes a semiconductor device as an example. The semiconductor device includes a heating element, a terminal electrically and thermally connected to one surface of the heating element and a first heat sink, a second heat sink electrically and thermally connected to the other surface of the heating element, and a sealing resin body that seals the components. Furthermore, the surface of the first heat sink opposite to the terminal is exposed from the sealing resin body. The surface of the second heat sink opposite to the heating element is exposed from the sealing resin body.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-138843 Summary of the Invention

[0008] In the semiconductor device described above, the first heat sink and the second heat sink are exposed from the sealing resin body as heat dissipation surfaces. Therefore, the semiconductor device needs to be further provided with an insulating member such as gel to ensure electrical insulation.

[0009] An object of the present invention is to provide a semiconductor device capable of ensuring both heat dissipation and electrical insulation.

[0010] A semiconductor device according to one embodiment of the present invention comprises a semiconductor element, a lead frame, a bridging member, and a sealing resin. The semiconductor element has a first electrode exposed on one surface and a second electrode exposed on the opposite surface. The lead frame includes a mounting portion for mounting the semiconductor element and electrically connected to the first electrode, and a non-mounting portion separate from the mounting portion. The bridging member is conductive and electrically connects the second electrode to the non-mounting portion. The sealing resin has electrical insulation properties and a thermal conductivity of 2.2 W or greater, and covers the semiconductor element, the lead frame, and the bridging member with the opposite surface of the mounting surface of the mounting portion exposed.

[0011] Thus, in the semiconductor device, the bridge member is covered with the sealing resin without being exposed, thereby ensuring electrical insulation. Furthermore, in the semiconductor device, the sealing resin has a thermal conductivity of 2.2 W or more, thereby ensuring heat dissipation. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a plan view showing a schematic structure of a semiconductor device according to an embodiment.

[0013] Figure 2 It is along Figure 1 Cross-sectional view of line II-II.

[0014] Figure 3 Graph showing heat dissipation characteristics of the semiconductor device according to the embodiment.

[0015] Figure 4 This is a cross-sectional view schematically showing the structure of a semiconductor device according to Modification 1.

[0016] Figure 5 It is a plan view showing a schematic structure of a semiconductor device according to Modification 2. DETAILED DESCRIPTION

[0017] Hereinafter, various embodiments for implementing the present invention will be described with reference to the accompanying drawings. In each embodiment, portions corresponding to those described in a previous embodiment may be assigned the same reference numerals, and duplicate descriptions may be omitted. In each embodiment, when only a portion of the structure is described, the remaining portions of the structure can be referred to and applied to the previously described embodiments. Furthermore, three mutually orthogonal directions will be denoted as the X, Y, and Z directions.

[0018] use Figure 1 、 Figure 2 、 Figure 3 , the semiconductor device 100 will be described. Figure 1 、 Figure 2 As shown, semiconductor device 100 includes two semiconductor elements 1 and 2, two lead frames 30 and 40, two connection pads 51 and 52, and sealing resin 7. In this embodiment, semiconductor device 100 including two semiconductor elements 1 and 2 is used. Accordingly, semiconductor device 100 includes two lead frames 30 and 40 and two connection pads 51 and 52. Furthermore, semiconductor device 100 includes two leads 61 and 62.

[0019] However, the present invention is not limited thereto, and it is sufficient as long as at least one semiconductor element is provided. In addition, the semiconductor device 100 only needs to include the same number of lead frames and the same number of connection pads as the number of semiconductor elements.

[0020] In addition, Figure 1 In the figure, the figure is simplified, and a part of the sealing resin 7 is omitted to make each component easier to understand. Figure 1The portion of the sealing resin 7 covering the two semiconductor elements 1 and 2 , the two lead frames 30 and 40 , the two connection pieces 51 and 52 , and the two leads 61 and 62 is omitted.

[0021] As an example, semiconductor elements 1 and 2 employ metal oxide semiconductor field effect transistors (MOSFETs). However, the present invention is not limited thereto, and insulated gate bipolar transistors (IGBTs) and the like may also be employed as semiconductor elements 1 and 2. Furthermore, as an example of semiconductor elements 1 and 2, reverse conduction (RC)-IGBTs, which integrate an IGBT and a diode, may also be employed. Furthermore, semiconductor elements 1 and 2 may employ, for example, elements primarily composed of Si or elements primarily composed of SiC.

[0022] The first semiconductor element 1 includes a first substrate 11, a first drain electrode 14 exposed on one surface of the first substrate 11, and a first source electrode 12 and a first gate electrode 13 exposed on the opposite surface of the first substrate 11. The first drain electrode 14 is formed over substantially the entire area of ​​one surface of the first substrate 11. On the other hand, the first source electrode 12 and the first gate electrode 13 are partially formed on the opposite surface of the first substrate 11.

[0023] The first substrate 11 is, for example, rectangular in the XY plane and has thickness in the Z direction. In this embodiment, as an example, a first substrate 11 is employed in which the Y direction is the longer direction and the X direction is the shorter direction.

[0024] The semiconductor element 1 may also be formed with a temperature sensor, a current sensor, etc. In this case, the semiconductor element 1 has a pad electrically connected to the temperature sensor and the current sensor formed on the same surface as the first source electrode 12 and the first gate electrode 13. Furthermore, the pad is arranged, for example, in the X direction along with the first gate electrode 13.

[0025] The second semiconductor element 2 includes a second substrate 21, a second drain electrode exposed on one surface of the second substrate 21, and a second source electrode 22 and a second gate electrode 23 exposed on the opposite surface of the second substrate 21. The second semiconductor element 2 has the same structure as the first semiconductor element 1. Therefore, the description of the first semiconductor element 1 can be referred to for the second semiconductor element 2.

[0026] The first semiconductor element 1 and the second semiconductor element 2 correspond to semiconductor elements. The first drain electrode 14 and the second drain electrode correspond to first electrodes. The first source electrode 12 and the second source electrode 22 correspond to second electrodes.

[0027] The first lead frame 30 includes a first source terminal 31, a first drain terminal 32, and a first signal terminal 33. The first lead frame 30 can be constructed primarily from a conductive metal material such as Cu, Fe, or an alloy thereof. The first source terminal 31, the first drain terminal 32, and the first signal terminal 33 are separated from each other.

[0028] The first semiconductor element 1 is mounted on the mounting surface S12 at the first drain terminal 32. Specifically, the first drain terminal 32 is a portion where the first semiconductor element 1 is mounted and electrically connected to the first drain electrode 14. The first drain terminal 32 is electrically connected to the first drain electrode 14 via a conductive connecting member such as solder. Thus, the first semiconductor element 1 is mounted on the first drain terminal 32 by electrically connecting the first drain electrode 14 and the first drain terminal 32 via the conductive connecting member. In this embodiment, solder is used as the conductive connecting member.

[0029] The opposite surface S11 of the first drain terminal 32, which is opposite to the mounting surface S12, is exposed from the sealing resin 7, as will be described later. Therefore, in addition to functioning as electrical wiring, the first drain terminal 32 also functions as a heat sink for dissipating heat generated by the first semiconductor element 1. Therefore, the opposite surface S11 can also be considered a heat dissipation surface. The mounting surface S12 and the opposite surface S11 can be, for example, flat surfaces.

[0030] The first drain terminal 32 corresponds to a mounting portion. The first drain terminal 32 may also be called an island.

[0031] The first source terminal 31 is electrically connected to the first source electrode 12 via the first connection piece 51. Thus, the first source terminal 31 is electrically connected to the first semiconductor element 1 (first source electrode 12) via the first connection piece 51 without mounting the first semiconductor element 1.

[0032] The first connecting piece 51 can be constructed primarily from a conductive material, such as a metal material such as Cu, Fe, or an alloy thereof. The first connecting piece 51 includes a first element-facing portion 51a that faces the first source electrode 12, a first terminal-facing portion 51b that corresponds to the first source terminal 31, and a first connecting portion 51c that connects the first element-facing portion 51a and the first terminal-facing portion 51b. The first element-facing portion 51a, the first terminal-facing portion 51b, and the first connecting portion 51c are integrally formed.

[0033] The first element-facing portion 51a is electrically connected to the first source electrode 12 via solder. Similarly, the first terminal-facing portion 51b is electrically connected to the first source terminal 31 via solder. In this manner, the first semiconductor element 1 electrically connects the first source electrode 12 to the first source terminal 31 via the first connection piece 51.

[0034] In this embodiment, as an example, a first connection piece 51 is used that is rectangular in the XY plane and has a thickness in the Z direction. In addition, in this embodiment, as an example, a first connection piece 51 is used in which the first connecting portion 51c faces the end of the first semiconductor element 1 and the first drain terminal 32. Furthermore, in this embodiment, as Figure 2 As shown, the first connection piece 51 is used in which the thickness of the first connection portion 51c is thinner than that of the first element facing portion 51a.

[0035] Thus, the semiconductor device 100 can easily ensure the insulation distance between the first drain terminal 32 and the first connecting piece 51. Furthermore, compared to a case where the first element-facing portion 51a has the same thickness as the first connecting portion 51c, the semiconductor device 100 can increase the heat capacity of the first semiconductor element 1, thereby improving heat dissipation.

[0036] The first source terminal 31 corresponds to the non-mounting portion. The first connection piece 51 corresponds to the bridge member.

[0037] The first signal terminal 33 is electrically connected to the first gate electrode 13 via the first lead 61. Thus, the first signal terminal 33 is not mounted on the first semiconductor element 1 but is electrically connected to the first semiconductor element 1 (first gate electrode 13) via the first lead 61.

[0038] In this embodiment, a plurality of first signal terminals 33 are formed. Thus, one first signal terminal 33 is electrically connected to the first gate electrode 13. Furthermore, the other first signal terminals 33 are electrically connected to pads electrically connected to the temperature sensor and the current sensor via the first lead 61.

[0039] Furthermore, in the first leadframe 30, the surface of the first source terminal 31 connected to the first terminal-facing portion 51b and the surface of the first signal terminal 33 connected to the first lead 61 are coplanar with the mounting surface S12 of the first drain terminal 32. In other words, the surface of the first source terminal 31 connected to the first terminal-facing portion 51b and the surface of the first signal terminal 33 connected to the first lead 61 can be said to be formed on an XY plane passing through the mounting surface S12. Similarly, the surface opposite to the surface of the first source terminal 31 connected to the first terminal-facing portion 51b and the surface opposite to the surface of the first signal terminal 33 connected to the first lead 61 are coplanar with the opposite surface S11 of the first drain terminal 32.

[0040] Therefore, the opposite surface S11 , the surface opposite to the surface connected to the first terminal opposing portion 51 b of the first source terminal 31 , and the surface opposite to the surface connected to the first lead 61 of the first signal terminal 33 may be collectively referred to as the opposite surface S11 .

[0041] Furthermore, the second lead frame 40 has a mounting surface and an opposite surface, similar to the first lead frame 30 . Therefore, hereinafter, portions described as the opposite surface S11 unless otherwise specified represent the opposite surfaces S11 of the first and second lead frames 30 and 40 .

[0042] The second lead frame 40 includes a second source terminal 41, a second drain terminal 42, and a second signal terminal 43. The second lead frame 40 has the same structure as the first lead frame 30. Therefore, for the second lead frame 40, the description of the first lead frame 30 can be referred to.

[0043] The second connection piece 52 includes a second element facing portion 52a, a second terminal facing portion 52b, and a second connecting portion 52c. The second connection piece 52 has the same structure as the first connection piece 51. Therefore, the description of the first connection piece 51 can be referred to for the second connection piece 52.

[0044] The second lead 62 has the same structure as the first lead 61. Therefore, for the second lead 62, the description of the first lead 61 can be referred to.

[0045] Sealing resin 7 is composed of an electrically insulating resin and a filler having a higher thermal conductivity than the electrically insulating resin. Specifically, sealing resin 7 has the filler embedded in the electrically insulating resin. The electrically insulating resin can be, for example, an epoxy resin. Meanwhile, the filler can be inorganic particles such as alumina. Sealing resin 7 is formed, for example, by injection molding using a metal mold.

[0046] The sealing resin 7 integrally covers the semiconductor elements 1, 2, the lead frames 30, 40, the connecting pieces 51, 52 and the leads 61, 62. The sealing resin 7 can be said to be in contact with and seal these. Figure 1 The semiconductor elements 1 and 2, the lead frames 30 and 40, the connection pieces 51 and 52, and the leads 61 and 62 shown in the figure are sealed with a sealing resin 7. The sealing resin 7 has a rectangular shape in the XY plane.

[0047] Sealing resin 7 such as Figure 2 As shown, the first surface S1 and the second surface S2 opposite to the first surface S1 are provided. The first surface S1 and the second surface S2 can be, for example, flat surfaces. Furthermore, the first surface S1 and the second surface S2 can be said to be formed along the XY plane.

[0048] Sealing resin 7 such as Figure 2 As shown, the semiconductor elements 1 and 2, the lead frames 30 and 40, the connecting pieces 51 and 52, and the leads 61 and 62 are covered with the opposite surface S11 of the drain terminals 32 and 42 being exposed. The entire area of ​​the opposite surface S11 of the lead frames 30 and 40 is exposed from the sealing resin 7. The first surface S1 is formed to be coplanar with the opposite surface S11.

[0049] The sealing resin 7 has electrical insulation properties and a thermal conductivity of 2.2 W or higher. The thermal conductivity of the sealing resin 7 can be adjusted by adjusting the amount and material of the filler. Therefore, the surface resin portion 71 described below is made of a material that has electrical insulation properties and a thermal conductivity of 2.2 W or higher.

[0050] Sealing resin 7 covers the entire area of ​​connecting tabs 51 and 52, excluding the connection locations with lead frames 30 and 40. Thus, sealing resin 7 is partially formed on connecting tabs 51 and 52. Specifically, sealing resin 7 includes a surface resin portion 71 formed on connecting tabs 51 and 52. Semiconductor device 100 includes surface resin portion 71 to prevent connecting tabs 51 and 52 from protruding from sealing resin 7. The presence of surface resin portion 71 ensures electrical insulation between connecting tabs 51 and 52.

[0051] The surface resin portion 71 is formed on the surface of the connecting sheets 51 and 52 opposite the semiconductor elements 1 and 2. Furthermore, the surface resin portion 71 is formed over the entire surface of the connecting sheets 51 and 52 opposite the semiconductor elements 1 and 2. Thus, the second surface S2 and the surface of the connecting sheets 51 and 52 opposite the surface facing the semiconductor elements 1 and 2 are located at different positions in the Z direction. Furthermore, the surface of the connecting sheets 51 and 52 facing the semiconductor elements 1 and 2 is the surface facing the source electrodes 12 and 22.

[0052] Surface resin portion 71 has a thickness at least twice the filler particle size. This allows sealing resin 7 to be formed as a surface resin portion 71 containing the filler. In other words, sealing resin 7 can maintain electrical insulation while maintaining thermal conductivity due to the filler. In other words, sealing resin 7 ensures both heat dissipation and electrical insulation.

[0053] When the thickness of surface resin portion 71 is approximately the same as the filler particle size, sealing resin 7 can be said to form a single resin layer on connecting sheets 51, 52. Sealing resin 7 can also be said to include surface resin portion 71 having a thickness that is at least one time the filler particle size.

[0054] The thickness of the surface resin portion 71 is preferably 0.2 mm to 0.6 mm. The thickness of the surface resin portion 71 is the thickness in the Z direction. The thickness of the surface resin portion 71 can be adjusted by the size of the cavity (hole) of the mold.

[0055] Therefore, it can be expected that the thickness of the surface resin portion 71 will vary depending on the shape and thickness tolerance of the connecting pieces 51 and 52, the tolerance of the solder formed on both sides of the semiconductor elements 1 and 2, and the thickness tolerance of the lead frames 30 and 40. The inventors studied the thickness of the surface resin portion 71 in consideration of these tolerances and the process capabilities when molding the sealing resin 7. As a result, it was found that the thickness of the surface resin portion 71 is preferably 0.4 mm ± 0.2 mm. That is, by making the thickness of the surface resin portion 71 0.4 mm ± 0.2 mm, the semiconductor device 100 can easily form the surface resin portion 71 containing the filler, thereby ensuring heat dissipation and electrical insulation.

[0056] In addition, in this embodiment, Figure 2 As shown, lead frames 30 and 40 are formed with a portion recessed from the opposite surface S11. Therefore, the sealing resin 7 is also formed between the lead frames 30 and 40 and the first surface S1. However, the present invention is not limited to this.

[0057] As described above, semiconductor device 100 ensures electrical insulation because it covers connecting pads 51 and 52 with sealing resin 7 without exposing them. Furthermore, because the thermal conductivity of sealing resin 7 is set to 2.2W or higher, semiconductor device 100 also ensures heat dissipation. Specifically, semiconductor device 100 ensures both electrical insulation and heat dissipation without applying electrically insulating thermal gel or the like to connecting pads 51 and 52. In other words, semiconductor device 100 alone ensures both electrical insulation and heat dissipation. Therefore, it is not necessary to ensure electrical insulation and heat dissipation at the user's end, such as at the point of delivery.

[0058] Furthermore, if Figure 3 As shown, the heat dissipation characteristics of the semiconductor device 100 and a semiconductor device of a comparative example (hereinafter referred to as the comparative example) were compared through simulation. Figure 3 In the figure, the horizontal axis represents the gel thickness [mm], and the vertical axis represents the thermal resistance [°C / W]. This simulation was performed with the temperature of the gel surface fixed. The gel is an electrically insulating heat dissipating gel.

[0059] The comparative example has a structure in which a semiconductor device with a double-sided heat dissipation structure is insulated with gel. That is, the comparative example has an electrically insulating heat dissipation gel with a thermal conductivity of 3W applied to the heat sink.

[0060] Furthermore, the thermal resistance represents the thermal resistance of the surface resin portion 71 or the gel. That is, the thermal resistance of semiconductor device 100 represents the thermal resistance of the surface resin portion 71 provided on the connection sheets 51 and 52. Furthermore, if a gel is provided on the surface resin portion 71, the thermal resistance of semiconductor device 100 represents the thermal resistance of the surface resin portion 71 and the gel.

[0061] The curve represented by the diamond (◇) points is a curve showing the heat dissipation characteristics of the comparative example. The curve represented by the triangle (△) points is a curve showing the heat dissipation characteristics of the semiconductor device 100 when the thermal conductivity of the sealing resin 7 is 3W and the thickness of the surface resin portion 71 is 0.5mm. The curve represented by the circle (○) points is a curve showing the heat dissipation characteristics of the semiconductor device 100 when the thermal conductivity of the sealing resin 7 is 2.2W and the thickness of the surface resin portion 71 is 0.6mm. The curve represented by the square (□) points is a curve showing the heat dissipation characteristics of the semiconductor device 100 when the thermal conductivity of the sealing resin 7 is 1W and the thickness of the surface resin portion 71 is 0.5mm.

[0062] The semiconductor device 100 of this embodiment does not have a gel. Therefore, the thermal resistance of the semiconductor device 100 is the value when the gel thickness is 0 mm. In addition, as described above, the semiconductor device 100 has a thermal conductivity of the sealing resin 7 of 2.2 W or more as a preferred example.

[0063] It can be seen from this that the thermal resistance of the semiconductor device 100 is as follows: Figure 3 As shown by the curves of the circular and triangular points in the figure, it is approximately less than 8°C / W. Therefore, it can be seen that by setting the thermal conductivity of the sealing resin 7 to 2.2W or greater, the semiconductor device 100 can achieve a thermal resistance comparable to or lower than that of the comparative example. In other words, by setting the thermal conductivity of the sealing resin 7 to 2.2W or greater, the semiconductor device 100 can achieve heat dissipation comparable to or higher than that of the comparative example. Furthermore, by setting the thermal conductivity of the sealing resin 7 to 2.2W or greater and the thickness of the surface resin portion 71 to 0.6mm or less, the semiconductor device 100 can achieve heat dissipation comparable to or higher than that of the comparative example.

[0064] The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments and can be variously modified within the scope of the present invention. Below, as other aspects of the present invention, Modifications 1 and 2 are described. The above embodiments and Modifications 1 and 2 can also be implemented individually, but can also be implemented in appropriate combinations. The present invention is not limited to the combinations shown in the embodiments and can be implemented in various combinations.

[0065] (Variation 1)

[0066] The semiconductor device 100 may also be Figure 4As shown, the semiconductor device 100 is mounted on a printed board 200 and attached to the motor 300 via gel 400. The printed board 200 has conductive wiring and pads formed on a substrate made of, for example, an electrically insulating resin. The first source terminal 31, first drain terminal 32, and first signal terminal 33 of the semiconductor device 100 are electrically connected to the pads of the printed board 200 via a conductive member such as solder.

[0067] The motor 300 includes, for example, a rotor and a stator, and a housing for housing the rotor and the stator. The semiconductor device 100 is mounted on the housing of the motor 300, for example.

[0068] Motor 300 can be a motor driven by semiconductor elements 1 and 2 of semiconductor device 100. In this case, semiconductor elements 1 and 2 serve as switching elements of an inverter that drives motor 300. In this embodiment, motor 300 is used as an example of an object on which semiconductor device 100 is mounted. However, the present invention is not limited to this. Semiconductor device 100 may also be mounted on a load (mounted object) driven by semiconductor elements 1 and 2 as drive elements.

[0069] Gel 400 is provided on second surface S2. Gel 400 can be any of the aforementioned gels. However, semiconductor device 100 alone has electrical insulation properties. Therefore, semiconductor device 100 does not need to use gel 400 to ensure electrical insulation from motor 300. Consequently, gel 400 can be made thinner than the gel used in the comparative example.

[0070] Of course, the semiconductor device 100 can achieve the same effects as those of the above-described embodiment. In addition, the semiconductor device 100 may include a printed board 200 , a motor 300 , and a gel 400 .

[0071] (Variation 2)

[0072] like Figure 5 As shown, the arrangement of semiconductor elements 1 and 2 in semiconductor device 110 differs from that in semiconductor device 100. In semiconductor device 110, first semiconductor elements 1 and second semiconductor elements 2 are arranged alternately. Specifically, in semiconductor device 110, second source terminal 41 is arranged adjacent to first signal terminal 33, and second signal terminal 43 is arranged adjacent to first source terminal 31. Semiconductor device 110 can achieve the same effects as semiconductor device 100.

Claims

1. A semiconductor device, characterized in that: have: A semiconductor element (1, 2) having a first electrode (14) exposed on one side and a second electrode (12, 22) exposed on the opposite side of the first side; A lead frame (30, 40) includes a mounting portion (32, 42) for mounting the semiconductor element and electrically connected to the first electrode, and a non-mounting portion (31, 41) separated from the mounting portion; Conductive bridge components (51, 52) electrically connect the second electrode and the non-mounting portion; and The sealing resin (7) has electrical insulation properties and a thermal conductivity of 2.2W or more, and covers the semiconductor element, the lead frame, and the bridge member in a state where the opposite surface (S11) of the mounting surface (S12) of the mounting portion is exposed; The sealing resin includes an electrically insulating resin and a filler having a higher thermal conductivity than the electrically insulating resin as constituent materials, and has a surface resin portion (71) formed on the bridge member, the surface resin portion having a gel on its surface and being mounted on the motor housing via the gel; The surface layer resin portion has a thickness of 0.2 mm to 0.6 mm, and is provided so that the bridge member is not exposed from the sealing resin.

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