Power conversion device

Abstract

This power conversion device is provided with: a semiconductor package having a semiconductor element and an external terminal electrically connected to the semiconductor element; a wiring board having a wiring layer electrically connected to the external terminal via a solder material; and a pressing member for pressing the semiconductor package in the thickness direction of the wiring board. The external terminal has an abutting part that, in the semiconductor package, protrudes from the surface on the wiring board side toward the wiring board. The abutting part abuts on a surface of the wiring board.

Description

Power Conversion Device

[0001] The present invention relates to a power conversion device.

[0002] High-voltage power converters employ double-sided cooling. In such power converters, the semiconductor package mounted on a printed circuit board may experience cracks due to temperature cycles at the solder joints between the package and the printed circuit board. Therefore, it is necessary to ensure the reliability of the device. For example, Patent Document 1 below discloses a configuration for improving device reliability, in which a protrusion is provided at the tip of an outer lead at a solder joint to provide a space for insulation and heat dissipation on a printed circuit board without through holes, and a semiconductor device is mounted on the surface of the printed circuit board.

[0003] Japanese Patent Application Publication No. 3-225944

[0004] The technology described in Patent Document 1 does not provide a structure for thickening and maintaining a constant solder thickness at the solder joints, so the terminals may sink into the solder due to the weight of the semiconductor package, potentially thinning the solder joints. As a result, stress strain at the solder joints caused by connecting both sides of the semiconductor package to the heat sink increases, creating a problem of not being able to ensure product reliability.

[0005] The power conversion device comprises a semiconductor package having a semiconductor element and an external terminal electrically connected to the semiconductor element, a wiring board having a wiring layer electrically connected to the external terminal via a solder material, and a pressing member that presses the semiconductor package in the thickness direction of the wiring board, wherein the external terminal has a butting portion that protrudes from the surface of the semiconductor package facing the wiring board toward the wiring board, and the butting portion abuts against the surface of the wiring board.

[0006] A power conversion device with improved reliability can be provided.

[0007] Cross-sectional view showing the configuration of a power conversion device according to a first embodiment of the present invention. Cross-sectional view showing the configuration of a power conversion device according to a second embodiment of the present invention. First and second modifications. Cross-sectional view showing the configuration of a power conversion device according to a third embodiment of the present invention. Third to fifth modifications. Sixth modification. Seventh modification.

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and some omissions and simplifications have been made as appropriate for clarity of explanation. The present invention can be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

[0009] In order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0010] (One embodiment and overall configuration) (FIG. 1) In a power conversion device, a semiconductor package 1 has a semiconductor element (not shown) and external terminals 6. Furthermore, the semiconductor package 1 has heat dissipation surfaces 3a, which are surfaces of conductor plates (not shown) on the top and bottom surfaces in the stacking direction and are exposed from the sealing resin that molds and seals the semiconductor package 1. One of the heat dissipation surfaces 3a of the semiconductor package 1 is a connection surface for electrically connecting to a wiring layer of a wiring board 9. This connection surface and the surface of the wiring board 9 are electrically connected by solder. Furthermore, the external terminals 6, which are provided facing outward from the semiconductor package 1, have abutment portions 5 that protrude toward the surface of the wiring board 9.

[0011] In the semiconductor package 1, the external terminals 6 are electrically connected to the semiconductor element. The external terminals 6 are electrically connected to the surface (electrode surface) of a wiring board 9 having a wiring layer via a solder material. The portion where the external terminals 6 and the wiring board 9 are connected to each other with the solder material is referred to as a solder connection portion 7. Note that such a connecting material is not limited to solder, and a sintered material, a hybrid material of metal and resin, or the like may also be used. The wiring board 9 may also be a board with thermal vias.

[0012] The semiconductor package 1 has one side opposite to the side where the external terminals 6 are connected to the wiring board 9, and the other side is exposed as a heat dissipation surface 3a. This heat dissipation surface 3a is thermally connected to a heat sink 2 via a heat dissipation member 3. The heat sink 2 is a cooling member that dissipates heat from the semiconductor package 1, but also functions as a pressing member that presses the semiconductor package 1 in the thickness direction of the wiring board 9. In Fig. 1, the heat sinks 2 are provided on both sides of the semiconductor package 1 in the thickness direction of the wiring board 9, and the upper and lower heat sinks 2 are fastened to each other with fixing screws 4, so that the semiconductor package 1 is pressed from both sides by the heat sinks 2.

[0013] The heat sink 2 is thermally connected to one side of the semiconductor package 1 via a heat dissipation member 3 (first thermal conductive member). The other side of the semiconductor package 1 is thermally connected to the surface of the wiring board 9 via a solder connection portion 7 (second thermal conductive member).

[0014] The external terminals 6 have abutment portions 5 that protrude from the surface of the semiconductor package 1 facing the wiring board 9 toward the wiring board 9. The abutment portions 5 abut against the surface of the wiring board 9. Note that, because it is necessary to leave an area for the solder material, which is the bonding material, to bond, the abutment portions 5 occupy only a portion of the bonding area of ​​the solder connection portions 7. This prevents the solder thickness of the solder connection portions 7 from becoming thin when pressure is applied from the heat sink 2 to the semiconductor package 1, and alleviates stress strain in the solder connection portions 7, thereby suppressing crack propagation. In other words, the abutment portions 5 can regulate the thickness of the solder material in the solder connection portions 7.

[0015] In the case where the wiring board 9 has thermal vias formed therein that penetrate from the top surface to the bottom surface of the board and transfer heat in the thickness direction, a plurality of such thermal vias are formed in the wiring board 9. The thermal vias are formed in an area that overlaps at least with the heat dissipation surface 3a on the bottom surface of the semiconductor package 1 in the thickness direction.

[0016] The surface of the wiring board 9 opposite to the surface connected to the semiconductor package 1 is thermally connected to the heat sink 2 via a heat dissipation member 3. Such a heat dissipation member 3 is made of a heat conductive material such as a silicone resin containing a thermally conductive filler or a heat dissipation sheet.

[0017] The wiring board 9 incorporates multiple wiring layers, such as positive wiring, negative wiring, and AC wiring (not shown) for configuring an inverter circuit, and gate wiring for controlling the driving of the semiconductor package. In the wiring board 9, the positive wiring, negative wiring, and AC wiring that configure the main circuit can use thick copper wiring exceeding 100 μm in thickness in order to pass a large current.

[0018] A field effect transistor made of SiC, which is a wide bandgap semiconductor, is used as the semiconductor element built into the semiconductor package 1. However, other semiconductor elements such as an IGBT made of Si may also be used as this semiconductor element.

[0019] In this embodiment, the semiconductor package 1 has a double-sided cooling structure in which heat dissipation surfaces 3a are formed on both sides thereof, but the present invention may also be applied to a semiconductor package 1 with single-sided cooling.

[0020] The butt portion 5 is a convex portion of the external terminal 6 that protrudes from the surface facing the wiring board 9, but this shape may be other shapes as long as it can regulate the thickness of the connecting material such as solder. Furthermore, the butt portion 5 may be formed, for example, by embossing the external terminal 6 from the surface opposite the wiring board 9 toward the wiring board 9. Furthermore, the butt portion 5 is not limited to a columnar protrusion, and may be tapered, hemispherical, or other shapes. Furthermore, multiple butt portions 5 may be provided for one external terminal 6.

[0021] Second Embodiment (FIG. 2) The wiring board 9 has a board opening 9a for mounting the semiconductor package 1 on the wiring board 9. By mounting the semiconductor package 1 on the wiring board 9 having the board opening 9a, the semiconductor package 1 is exposed on the side of the wiring board 9 opposite to the side where the external terminals 6 and the wiring board 9 are connected.

[0022] Heat sinks 2 are disposed on both sides of the semiconductor package 1, with heat dissipation members 3, which are thermally conductive members, interposed therebetween. The heat dissipation members 3 may be made of, for example, silicone resin containing a thermally conductive filler. Alternatively, a sheet-like thermally conductive member may be used instead.

[0023] The heat sink 2 is, for example, a refrigerant flow path through which a refrigerant flows, and is a pressing member that presses the semiconductor package 1 from both sides in the thickness direction of the wiring board 9. The heat sink 2 is fastened to each other with fixing screws 4, and is fixed so that it is pressed against the heat dissipation surfaces 3a provided on both sides of the semiconductor package 1. As a result, the heat dissipation surfaces 3a on both sides of the semiconductor package 1 and the heat sink 2 are thermally connected, so that heat generated from the semiconductor package 1 is dissipated to the heat sink 2 via the heat dissipation surfaces of the semiconductor package 1 and the heat dissipation members 3.

[0024] Furthermore, in such a configuration, the weight of the semiconductor package 1 itself can cause the thickness of the solder connection portion 7 to become thin, but by providing the external terminal 6 with a butt portion 5 that protrudes from the surface of the wiring board 9, the solder thickness of the solder connection portion 7 can be ensured to be at least a certain level, thereby improving the reliability of the power conversion device.

[0025] (First Modification, Second Modification) (Fig. 3) Fig. 2(a) shows a first modification of the power conversion device of the present invention, and Fig. 2(b) shows a second modification. Note that the modification shown in Fig. 3 applies the wiring board 9 having the board opening 9a described in Fig. 2, but it can also be applied to the wiring board 9 of Fig. 1 that does not have the board opening 9a.

[0026] 1 and 2, the butt portion 5 is formed inside the solder material of the solder connection portion 7, so that the solder material is interposed between the tip of the butt portion 5 and the surface of the wiring board 9, which may result in a partial thinning of the solder material in that area and a loss of reliability. However, in the modified examples shown in Figures 3(a) and 3(b), the butt portion 5 is not formed inside the solder material in the planar direction, but is formed outside it. This prevents the solder thickness of the solder connection portion 7 from being partially thin, and allows the thickness of the solder connection portion 7 to be kept thick and constant, improving reliability.

[0027] 3A, the abutment portion 5 is formed outside the solder material and is provided closer to the semiconductor package 1 than the solder connection portion 7. This exposes the solder connection portion 7 on the tip side of the terminal, making it easier to inspect the appearance of the solder connection portion 7.

[0028] 3B, the abutment portion 5 is formed outside the solder material and is provided at a position farther away from the solder connection portion 7 in the planar direction relative to the semiconductor package 1. By providing the abutment portion 5 at a position farther away from the semiconductor package 1 than the installation position of the solder material, the abutment portion 5 can be made to stand on its own on the surface of the wiring board 9 regardless of the solder position or solder thickness, thereby suppressing variations in the thickness direction of the semiconductor package 1.

[0029] Third Embodiment (FIG. 4) A wiring board 9 has through holes 13 electrically connected to wiring layers. Abutment portions 5 provided on external terminals 6 abut against opening edges 13a of through holes 13 provided in the wiring board 9. Furthermore, external terminals 6 have protrusions 5a that protrude into the through holes 13 from the abutting portions where the opening edges of the through holes 13 abut against the abutment portions 5.

[0030] Protrusion 5a is joined by solder to the inner periphery of through hole 13. The connection between protrusion 5a and the inner periphery of through hole 13 is called solder connection 7. This provides solder connection 7 not only on the surface of wiring board 9 but also within through hole 13, thereby increasing the joint area of ​​solder connection 7 and further improving the reliability of the device.

[0031] Furthermore, the external terminals 6 have bent portions 12 between the solder connection portions 7 and the semiconductor package 1. This reduces the stress applied to the solder connection portions 7, thereby improving reliability. Note that the configuration shown in Fig. 4 applies to the wiring board 9 having the openings 9a described in Fig. 2, but it can also be applied to the wiring board 9 in Fig. 1 that does not have the board openings 9a.

[0032] (Third to Fifth Modifications) (FIG. 5) FIG. 5(a) shows a third modification, FIG. 5(b) shows a fourth modification, and FIG. 5(c) shows a fifth modification. As shown in FIG. 5(a), the abutting portion 5 of the external terminal 6 may only partially abut against the opening edge 13a of the through-hole 13. In this case, the portion of the solder connection portion 7 provided between the external terminal 6 and the surface of the wiring board 9 and the portion provided inside the through-hole 13 may be integrated. Also, as shown in FIG. 5(b), the external terminal 6 may be configured without the bent portion 12. Also, as shown in FIG. 4(c), the protrusion 5a may not protrude from the abutting portion 5, but may protrude from the external terminal 6 into the through-hole 13. In this case, the portion of the solder connection portion 7 provided between the external terminal 6 and the surface of the wiring board 9 and the portion provided inside the through-hole 13 may be integrated.

[0033] (Sixth Modification) (FIG. 6) The wiring substrate 9 may have a plurality of substrate openings 9a. A semiconductor package 1 is mounted in each of the plurality of substrate openings 9a. This configuration is applied when a plurality of semiconductor packages 1 are mounted corresponding to the switching elements that configure each arm of a three-phase inverter circuit.

[0034] Furthermore, since multiple switching elements constituting each arm can be used in parallel, a large current can be passed through. Also, by integrating multiple semiconductor packages 1 on one wiring board 9, it contributes to the miniaturization of the entire device. Note that the power conversion device of the present invention is not limited to one having only one wiring board 9, and multiple wiring boards 9 may be used.

[0035] Even with this configuration, by providing the abutment portions 5 on the external terminals 6, it is possible to reduce variations in the thickness of the solder connection portions 7 for each semiconductor package 1. Furthermore, by reducing variations in the placement of the semiconductor packages 1, it is possible to reduce variations in the spacing between the semiconductor packages 1 and the heat sink 2, and thus variations in heat dissipation performance. Furthermore, by mounting multiple semiconductor packages 1 in the in-plane direction of the wiring substrate 9, the load on each semiconductor package 1 is reduced, improving the reliability of the power conversion device.

[0036] (Seventh Modification) (FIG. 7) The wiring board 9 has second abutment portions 11 that protrude from the surface of the wiring board 9 toward the external terminals 6. In this way, the abutment portions 5 that protrude from the external terminals 6 toward the wiring board 9 and the abutment portions 5 that protrude from the wiring board 9 toward the external terminals 6 can further reduce variations in the thickness of the solder connections 7, thereby improving the reliability of the power conversion device.

[0037] According to the embodiment of the present invention described above, the following advantageous effects are achieved.

[0038] (1) The power conversion device includes a semiconductor package 1 having a semiconductor element and external terminals 6 electrically connected to the semiconductor element, a wiring board 9 having a wiring layer electrically connected to the external terminals 6 via a solder material, and a pressing member 2 that presses the semiconductor package 1 in the thickness direction of the wiring board 9, and the external terminals 6 have abutment portions 5 that protrude from the surface of the semiconductor package 1 facing the wiring board 9 toward the wiring board 9, and the abutment portions 5 abut against the surface of the wiring board 9. In this way, a power conversion device with improved reliability can be provided.

[0039] (2) The abutment portion 5 is provided outside the solder material in the planar direction. This allows the thickness of the solder connection portion 7 to be thick and uniform, thereby improving reliability.

[0040] (3) The abutment portion 5 is provided closer to the semiconductor package 1 than the solder material in the planar direction. This makes it easier to inspect the appearance of the solder connection portion 7.

[0041] (4) The abutment portion 5 is provided at a position farther away from the solder material in the planar direction than the semiconductor package 1. This makes it possible to reduce variations in the thickness direction of the semiconductor package 1.

[0042] (5) The wiring board 9 has a through hole 13 electrically connected to the wiring layer, the abutment portion 5 abuts against the opening edge 13a of the through hole 13, and the external terminal 6 has a protrusion 5a electrically connected to the inner periphery of the through hole 13. This increases the bonding area of ​​the solder connection portion 7, improving reliability.

[0043] (6) The wiring board 9 has a board opening 9a for mounting the semiconductor package 1, the semiconductor package 1 being exposed on the side of the wiring board 9 opposite to the side connected to the external terminals 6, and the pressing member 2 is thermally connected to both sides of the semiconductor package 1 in the thickness direction via the heat conduction member 3. In this way, the abutment portion 5 can ensure that the thickness of the solder connection portion 7 is at least a certain level, improving reliability.

[0044] (7) The pressing member 2 is thermally connected to one side of the semiconductor package 1 via the first thermal conductive member 3, and the other side of the semiconductor package 1 is thermally connected to the surface of the wiring board 9 via the second thermal conductive member. This reduces the thermal stress on the solder connection 7, improving reliability.

[0045] (8) The semiconductor package 1 is provided for each of the plurality of board openings 9a. This reduces the load on each semiconductor package 1, improving reliability.

[0046] (9) The wiring board 9 has a second abutment portion 11 that protrudes from the surface of the wiring board 9 toward the external terminal 6. This ensures that the thickness of the solder connection portion 7 is at least a certain level, thereby improving reliability.

[0047] The present invention is not limited to the above-described embodiments, and various modifications and combinations of other configurations are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to those having all of the configurations described in the above-described embodiments, and includes those in which some of the configurations are omitted.

[0048] REFERENCE SIGNS LIST 1 semiconductor package 2 heat sink 3 heat dissipation member 3a heat dissipation surface 4 fixing screw 5 butt portion 5a protrusion 6 external terminal 7 solder connection portion 9 wiring board 9a board opening 11 second butt portion 12 bent portion 13 through hole 13a opening edge

Claims

1. A power conversion device comprising: a semiconductor package having a semiconductor element and external terminals electrically connected to the semiconductor element; a wiring board having a wiring layer electrically connected to the external terminals via a solder material; and a pressing member that presses the semiconductor package in the thickness direction of the wiring board, wherein the external terminals have abutment portions that protrude from the surface of the semiconductor package facing the wiring board toward the wiring board, and the abutment portions abut against the surface of the wiring board.

2. A power converter according to claim 1, wherein the abutting portion is provided outside the solder material in the planar direction.

3. A power converter according to claim 2, wherein the abutting portion is provided closer to the semiconductor package than the solder material in the planar direction.

4. A power conversion device according to claim 2, wherein the abutting portion is provided at a position farther from the solder material than the semiconductor package in the planar direction.

5. A power conversion device according to claim 1, wherein the wiring board has a through-hole electrically connected to the wiring layer, the abutment portion abuts against the opening edge of the through-hole, and the external terminal has a protrusion electrically connected to the inner periphery of the through-hole.

6. A power conversion device according to claim 1, wherein the wiring board has a board opening for mounting the semiconductor package, the semiconductor package is exposed on the wiring board on the side opposite to the side connected to the external terminal, and the pressing member is thermally connected to both sides of the semiconductor package in the thickness direction via a heat conductive member.

7. A power conversion device according to claim 1, wherein the pressing member is thermally connected to one side of the semiconductor package via a first heat conducting member, and the other side of the semiconductor package is thermally connected to the surface of the wiring board via a second heat conducting member.

8. A power conversion device according to claim 6, wherein the semiconductor package is provided for each of the plurality of substrate openings.

9. A power conversion device according to claim 1, wherein the wiring board has a second abutment portion that protrudes from the surface of the wiring board toward the external terminal.

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