WO2025243406A1 - Power conversion device - Google Patents

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

The present invention relates to a power conversion device.

High-voltage power conversion devices use double-sided cooling. In such power conversion devices, the semiconductor package mounted on the printed circuit board may crack due to temperature cycles at the solder joints that connect the package to the printed circuit board. For this reason, 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 protrusions are provided at the tips of the outer leads of the solder joints to provide space for insulation and heat dissipation on a printed circuit board without through holes, and the semiconductor device is mounted on the surface of the printed circuit board.

Japanese Patent Application Publication No. 3-225944

The technology described in Patent Document 1 does not include a structure for thickening and maintaining a consistent solder thickness at the solder joints, which means that the weight of the semiconductor package can cause the terminals to sink into the solder, potentially thinning the solder joints. As a result, the stress and strain on the solder joints caused by both sides of the semiconductor package being connected to the heat sink increases, creating the problem of not being able to ensure product reliability.

The power conversion device comprises 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, the external terminals having 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.

It is possible to provide a power conversion device with improved reliability.

1 is a cross-sectional view showing a configuration of a power conversion device according to a first embodiment of the present invention; FIG. 10 is a cross-sectional view showing the configuration of a power conversion device according to a second embodiment of the present invention. First modified example and second modified example FIG. 10 is a cross-sectional view showing the configuration of a power conversion device according to a third embodiment of the present invention. Third to fifth modified examples Sixth Modification Seventh Modification

Embodiments of the present invention will be described below with reference to the drawings. The following description and drawings are examples for explaining the present invention, and have been omitted or simplified as appropriate for clarity of explanation. The present invention can also be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

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.

(One embodiment and overall configuration)
(Figure 1)
In the power conversion device, the semiconductor package 1 has a semiconductor element (not shown) and external terminals 6. 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. 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.

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 the wiring board 9, which has 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 called the solder connection portion 7. Note that such a connection material is not limited to solder; sintered material, hybrid material of metal and resin, etc. may also be used. The wiring board 9 may also be a substrate with thermal vias.

The semiconductor package 1 has one side opposite 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 the heat sink 2 via the 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 Figure 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.

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).

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 serves as the bonding material, the abutment portions 5 occupy only a portion of the bonding area of the solder connection portion 7. This prevents the solder thickness of the solder connection portion 7 from becoming thin when pressure is applied from the heat sink 2 to the semiconductor package 1, and by easing stress strain in the solder connection portion 7, crack propagation can be suppressed. In other words, the abutment portions 5 can regulate the thickness of the solder material in the solder connection portion 7.

If the wiring board 9 has thermal vias that penetrate from the top to the bottom of the board and transfer heat in the thickness direction, multiple thermal vias are formed on the wiring board 9. These 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.

Furthermore, the surface of the wiring board 9 opposite 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 thermally conductive material such as a silicone resin containing a thermally conductive filler or a heat dissipation sheet.

The wiring board 9 incorporates multiple wiring layers, including positive wiring, negative wiring, and AC wiring (not shown) that form the inverter circuit, as well as gate wiring for controlling the operation of the semiconductor package. In the wiring board 9, the positive wiring, negative wiring, and AC wiring that form the main circuit can use thick copper wiring exceeding 100 μm in thickness to allow for the passage of large currents.

The semiconductor element built into the semiconductor package 1 is a field-effect transistor made of SiC, a wide bandgap semiconductor. However, other semiconductor elements, such as an IGBT made of Si, may also be used.

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

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 is possible to regulate the thickness of the connecting material, such as solder. The butt portion 5 may also be formed, for example, by embossing the external terminal 6 from the surface opposite the wiring board 9 toward the wiring board 9. The butt portion 5 is not limited to a columnar protrusion, and may also be tapered, hemispherical, or other shapes. One external terminal 6 may have multiple butt portions 5.

Second Embodiment
(Figure 2)
The wiring board 9 has a substrate opening 9a for mounting the semiconductor package 1 on the wiring board 9. When the semiconductor package 1 is mounted on the wiring board 9 having the substrate 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.

Heat sinks 2 are arranged on both sides of the semiconductor package 1, with heat dissipation members 3, which are thermally conductive members, interposed between them. 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.

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, and 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 member 3.

Furthermore, with this configuration, the weight of the semiconductor package 1 itself can cause the solder connection 7 to become thinner, but by providing the external terminals 6 with abutment sections 5 that protrude from the surface of the wiring board 9, it is possible to ensure that the solder thickness of the solder connection sections 7 remains at a certain level, improving the reliability of the power conversion device.

(First Modification, Second Modification)
(Figure 3)
Fig. 2(a) shows a first modified example of the power conversion device of the present invention, and Fig. 2(b) shows a second modified example. Note that the modified example shown in Fig. 3 applies the wiring board 9 having the board opening 9a explained in Fig. 2, but it can also be applied to the wiring board 9 not provided with the board opening 9a of Fig. 1.

In the configuration shown in Figures 1 and 2, the butt portion 5 is formed inside the solder material of the solder connection portion 7, which means that the solder material is interposed between the tip of the butt portion 5 and the surface of the wiring board 9, causing the solder material to become locally thin in that area, potentially reducing 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 outside it. This prevents the solder thickness of the solder connection portion 7 from becoming locally thin, and allows the solder connection portion 7 to have a thick, consistent thickness, improving reliability.

In the first modified example shown in Figure 3(a), the abutment portion 5 is formed outside the solder material and is located 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 perform visual inspection of the solder connection portion 7.

In addition, in the second modified example shown in Figure 3(b), the abutment portion 5 is formed outside the solder material and is located at a position farther away from the solder connection portion 7 in the planar direction relative to the semiconductor package 1. By locating the abutment portion 5 at a position farther away from the semiconductor package 1 than the installation position of the solder material in this way, 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 reducing variation in the thickness direction of the semiconductor package 1.

(Third embodiment)
(Figure 4)
The wiring board 9 has through holes 13 electrically connected to the wiring layer. The abutment portions 5 provided on the external terminals 6 abut against the opening edges 13a of the through holes 13 provided in the wiring board 9. The external terminals 6 also have protrusions 5a that protrude into the through holes 13 from the abutting portions where the abutment portions 5 abut against the opening edges of the through holes 13.

The protrusion 5a is joined to the inner periphery of the through-hole 13 by solder. The connection between the protrusion 5a and the inner periphery of the through-hole 13 is called the solder connection 7. As a result, in addition to the solder connection 7 on the surface of the wiring board 9, a solder connection 7 is also provided within the through-hole 13, increasing the bonding area of the solder connection 7 and further improving the reliability of the device.

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, improving reliability. Note that while the configuration shown in Figure 4 applies to a wiring board 9 with the openings 9a described in Figure 2, it can also be applied to a wiring board 9 without the board openings 9a of Figure 1.

(Third to fifth modified examples)
(Figure 5)
5( a ) shows a third modified example, FIG. 5( b ) shows a fourth modified example, and FIG. 5( c ) shows a fifth modified example. As shown in FIG. 5( a ), the butt portion 5 of the external terminal 6 may only partially abut against the opening edge 13 a of the through-hole 13. In this case, the solder connection portion 7 may be integrated with the portion provided between the external terminal 6 and the surface of the wiring board 9 and the portion provided inside the through-hole 13. 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 5 a may be configured to protrude from the external terminal 6 into the through-hole 13 rather than protruding from the butt portion 5. In this case, the solder connection portion 7 may be integrated with the portion provided between the external terminal 6 and the surface of the wiring board 9 and the portion provided inside the through-hole 13.

(Sixth Modification)
(Figure 6)
The wiring substrate 9 may have a plurality of substrate openings 9 a. The semiconductor package 1 is mounted in each of the plurality of substrate openings 9 a. 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.

Furthermore, multiple switching elements that make up each arm can be used in parallel, allowing for large currents to flow. Furthermore, integrating multiple semiconductor packages 1 on a single wiring board 9 also contributes to the miniaturization of the entire device. Note that the power conversion device of the present invention is not limited to one with only one wiring board 9, and multiple wiring boards 9 may be used.

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 board 9, the load on each semiconductor package 1 is reduced, improving the reliability of the power conversion device.

(Seventh Modification)
(Figure 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 suppress variations in the thickness of the solder connections 7, thereby improving the reliability of the power conversion device.

The above-described embodiment of the present invention provides the following advantages.

(1) The power conversion device comprises 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, where 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. By doing so, it is possible to provide a power conversion device with improved reliability.

(2) The abutment portion 5 is located outside the solder material in the planar direction. This allows the thickness of the solder connection portion 7 to be thick and consistent, improving reliability.

(3) The abutment portion 5 is located closer to the semiconductor package 1 than the solder material in the planar direction. This makes it easier to perform visual inspection of the solder connection portion 7.

(4) The abutment portion 5 is located at a position farther away from the solder material than the semiconductor package 1 in the planar direction. This reduces variations in the thickness of the semiconductor package 1.

(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.

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

(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.

(8) A semiconductor package 1 is provided for each of the multiple board openings 9a. This reduces the load on each semiconductor package 1, improving reliability.

(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, improving reliability.

Note that the present invention is not limited to the above-described embodiments, and various modifications and other configurations can be combined without departing from the spirit of the invention. Furthermore, the present invention is not limited to those that include all of the configurations described in the above embodiments, and also includes those in which some of the configurations are omitted.

REFERENCE SIGNS LIST 1 Semiconductor package 2 Heat sink 3 Heat dissipation member 3a Heat dissipation surface 4 Fixing screw 5 Abutment portion 5a Protrusion 6 External terminal 7 Solder connection portion 9 Wiring board 9a Board opening 11 Second abutment portion 12 Bent portion 13 Through hole 13a Opening edge

Claims (9)

a semiconductor package having a semiconductor element and external terminals electrically connected to the semiconductor element;
a wiring substrate having a wiring layer electrically connected to the external terminals via a solder material;
a pressing member that presses the semiconductor package in a thickness direction of the wiring substrate,
the external terminals have abutment portions that protrude from the surface of the semiconductor package facing the wiring board toward the wiring board,
The abutting portion abuts against a surface of the wiring board. The power conversion device according to claim 1,
The power conversion device, wherein the abutting portion is provided outside the solder material in a planar direction. The power conversion device according to claim 2,
The abutting portion is provided closer to the semiconductor package than the solder material in the planar direction. The power conversion device according to claim 2,
The power conversion device, wherein the abutment portion is provided at a position farther away from the solder material with respect to the semiconductor package in the planar direction. The power conversion device according to claim 1,
the wiring substrate has a through hole electrically connected to the wiring layer,
the abutting portion abuts against an opening edge of the through hole,
The external terminal has a protrusion electrically connected to an inner periphery of the through hole. The power conversion device according to claim 1,
the wiring substrate has a substrate opening for mounting the semiconductor package;
the semiconductor package is exposed on the wiring board on a side opposite to a side connected to the external terminals,
The pressing member is thermally connected to both surfaces of the semiconductor package in the thickness direction via a thermally conductive member. The power conversion device according to claim 1,
the pressing member is thermally connected to one surface of the semiconductor package via a first thermal conductive member;
The other surface of the semiconductor package is thermally connected to the surface of the wiring board via a second thermal conductive member. 7. The power conversion device according to claim 6,
The semiconductor package is provided in each of the plurality of substrate openings. The power conversion device according to claim 1,
The power conversion device, wherein the wiring board has a second abutment portion that protrudes from a surface of the wiring board toward the external terminal.