Electric power conversion device

Abstract

To provide an electric power conversion device capable of increasing the degree of adhesion between a bus bar and a pattern of a substrate, in a structure for dissipating heat by using the bus bar capable of firmly fixing the substrate and the bus bar to a heat sink and thereby increasing the degree of adhesion between the bus bar and a conductive pattern.SOLUTION: An electric power conversion device includes a substrate 1 having an element 23 and a first conductive pattern 7 on a front surface and having a second conductive pattern 65 electrically connected to the first conductive pattern on a back surface. A bus bar 119 is installed on a back surface side of the substrate while kept in contact with the second conductive pattern. An insulating heat conductive sheet 121 is installed on a side opposite a substrate of the bus bar. A heat sink 111 is installed on a side opposite a substrate of the insulating heat conductive sheet. The substrate and the bus bar are fixed to the heat sink by an insulating fixing screw 125.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a power conversion device, and in particular to a power conversion device that employs a structure for dissipating heat through a conductive pattern, a bus bar, and a heat sink provided on a substrate, and that is devised to enable the substrate and bus bar to be firmly fixed to the heat sink, thereby increasing the degree of adhesion between the bus bar and the conductive pattern. [Background technology]

[0002] For example, in a power conversion device, power semiconductors are mounted on an aluminum or ceramic substrate in consideration of heat dissipation, but these aluminum or ceramic substrates are expensive.

[0003] Therefore, it has been proposed to adopt a heat dissipation structure using bus bars and an inexpensive printed circuit board. Examples of this type of structure are disclosed in Patent Document 1 and Patent Document 2.

[0004] The invention described in Patent Document 1 includes a circuit board with a semiconductor switch mounted on the surface of the circuit board. A bus bar is installed on the back side of the circuit board, and a part of the bus bar (a pin) is press-fitted into a drilled hole in the circuit board. A heat sink is installed below the bus bar with thermally conductive insulating foil interposed therebetween.

[0005] The heat generated by the semiconductor switch is dissipated through the bus bar pins, the bus bar, the thermally conductive insulating foil, and the heat sink.

[0006] In the case of the invention described in Patent Document 2, FETs are mounted on the surface of a control circuit board. A bus bar component plate is provided below the control circuit board, and bus bars are provided on this bus bar component plate. A heat dissipation member is provided below the bus bar component plate.

[0007] The heat generated in the FET is dissipated through the bus bar component plate, the bus bar, and the heat dissipation member. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-117805 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-031416 Summary of the Invention [Problem to be solved by the invention]

[0009] The above conventional configuration has the following problems. First, the board and bus bar are attached by simply soldering or pressure welding the heat conducting element provided on the bus bar to the board, which poses a problem of low mechanical strength. Furthermore, there are concerns that repeated heat generation will cause thermal shock, which can lead to thermal fatigue in the soldered joints, as well as deterioration in strength due to expansion and contraction. Furthermore, the bus bar is simply bonded to the heat sink via a thermally conductive insulating film, which causes a problem of low mechanical strength.

[0010] The present invention has been made in light of the above points, and its object is to provide a power conversion device that employs a structure in which heat is dissipated through conductive patterns, bus bars, and a heat sink provided on a substrate, and that can firmly fix the substrate and bus bars to the heat sink, thereby increasing the degree of adhesion between the bus bars and the conductive patterns. [Means for solving the problem]

[0011] In order to solve the above problem, the power conversion device according to claim 1 of the present invention is characterized in that it includes a substrate having an element and a first conductive pattern on its front surface and a second conductive pattern electrically connected to the first conductive pattern on its back surface, a bus bar is installed on the back surface of the substrate in contact with the second conductive pattern, an insulating thermally conductive sheet is installed on the opposite side of the bus bar to the substrate, a heat sink is installed on the opposite side of the insulating thermally conductive sheet to the substrate, and the substrate and the bus bar are fixed to the heat sink with insulating fixing screws. Furthermore, the power conversion device according to claim 2 is the power conversion device according to claim 1, characterized in that the substrate is fixed to the bus bar by a conductive fixing screw at a position different from the fixing position by the insulating fixing screw. Furthermore, the power conversion device according to claim 3 is characterized in that, in the power conversion device according to claim 1, external terminals are fixed to the heat sink with fixing screws, and the pass bar is integrally molded with the external terminals in advance. Furthermore, the power conversion device according to claim 4 is the power conversion device according to claim 1, characterized in that a base is protruding from the heat sink at the fixing position by the insulating fixing screw, and an insulating sheet is interposed between the bus bar and the base. Furthermore, the power converter according to claim 5 is the power converter according to claim 4, characterized in that the insulating sheet has a higher hardness than the insulating heat-conductive sheet. Furthermore, the power conversion device according to claim 6 is characterized in that in the power conversion device according to claim 1, the first conductive pattern and the second conductive pattern are electrically connected via a through-hole via. Furthermore, the power conversion device according to claim 7 is characterized in that, in the power conversion device according to claim 1, the elements are an upstream switching element and a downstream switching element electrically connected via the first conductive pattern. Furthermore, a power conversion device according to claim 8 is the power conversion device according to claim 7, characterized in that the first conductive pattern, the second conductive pattern and the bus bar are arranged in parallel to each other in an elongated shape, and multiple pairs of the upstream switching element and the downstream switching element are arranged along the longitudinal direction of the first conductive pattern. Furthermore, the power conversion device according to claim 9 is characterized in that, in the power conversion device according to claim 2, a convex portion is provided on the bus bar between the fastening position by the insulating fixing screw and the fastening position by the conductive fixing screw. Furthermore, the power conversion device according to claim 10 is characterized in that, in the power conversion device according to claim 2, recesses are formed in the bus bars at the fastening positions with the insulating fixing screws and the fastening positions with the conductive fixing screws. [Effects of the Invention]

[0012] As described above, the power conversion device according to claim 1 of the present invention includes a substrate having elements and a first conductive pattern on its front surface and a second conductive pattern electrically connected to the first conductive pattern on its back surface, a bus bar mounted on the back surface of the substrate in contact with the second conductive pattern, an insulating thermally conductive sheet mounted on the opposite side of the bus bar to the substrate, a heat sink mounted on the opposite side of the insulating thermally conductive sheet, and the substrate and bus bar fixed to the heat sink with insulating fixing screws. Therefore, in a power conversion device that employs a structure in which heat is dissipated via the conductive pattern, bus bar, and heat sink provided on the substrate, the substrate and bus bar can be firmly fixed to the heat sink, thereby increasing the degree of adhesion between the bus bar and the conductive pattern. Furthermore, according to the power conversion device of claim 2, in the power conversion device of claim 1, the substrate is fixed to the bus bar by a conductive fixing screw at a position different from the fixing position by the insulating fixing screw, thereby further enhancing the integration of the substrate and the bus bar and increasing the degree of adhesion between the bus bar and the second conductive pattern of the substrate. According to a power conversion device of claim 3, in the power conversion device of claim 1, the external terminals are fixed to the heat sink with fixing screws, and the bus bars are integrally molded with the external terminals in advance, so that the substrate and the bus bars can be firmly fixed to the heat sink, thereby increasing the degree of adhesion between the bus bars and the second conductive pattern of the substrate. Furthermore, according to the power conversion device of claim 4, in the power conversion device of claim 1, a base is protruded from the heat sink at the fixing position by the insulating fixing screw, and an insulating sheet is interposed between the bus bar and the base, so that the board and bus bar can be firmly fixed to the heat sink. Furthermore, according to the power conversion device of claim 5, in the power conversion device of claim 4, the insulating sheet has a higher hardness than the insulating thermally conductive sheet, so that the substrate and bus bar can be more firmly fixed to the heat sink. Furthermore, according to the power conversion device of claim 6, in the power conversion device of claim 1, the first conductive pattern and the second conductive pattern are electrically connected via a through-hole via, so that the first conductive pattern and the second conductive pattern can be reliably electrically connected. Furthermore, according to the power conversion device of claim 7, in the power conversion device of claim 1, the elements are an upstream switching element and a downstream switching element that are electrically connected via the first conductive pattern. Even in this configuration, in a structure that dissipates heat via a conductive pattern, a bus bar, and a heat sink provided on a substrate, the substrate and the bus bar can be firmly fixed to the heat sink, thereby increasing the degree of adhesion between the bus bar and the conductive pattern. According to a power conversion device of claim 8, in the power conversion device of claim 7, the first conductive pattern, the second conductive pattern, and the bus bar are arranged in parallel to each other in an elongated shape, and the upstream switching elements and downstream switching elements are arranged in pairs along the longitudinal direction of the first conductive pattern. Even in this configuration, in a structure that dissipates heat via the conductive patterns, bus bar, and heat sink provided on a substrate, the substrate and bus bar can be firmly fixed to the heat sink, thereby increasing the degree of adhesion between the bus bar and the conductive patterns. Furthermore, according to the power conversion device of claim 9, in the power conversion device of claim 2, a convex portion is provided on the bus bar between the fastening position with the insulating fixing screw and the fastening position with the conductive fixing screw, thereby making the contact between the board and the bus bar strong. According to the power conversion device of claim 10, in the power conversion device of claim 2, recesses are formed in the bus bar at the fastening positions with the insulating fixing screws and the fastening positions with the conductive fixing screws, thereby making it possible to strengthen the contact between the board and the bus bar. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing a first embodiment of the present invention, and is a plan view showing the configuration of the surface of a substrate of a power converter. [Figure 2] FIG. 1 is a diagram showing a first embodiment of the present invention, and is a plan view showing the configuration of the rear surface of a substrate of a power conversion device. [Figure 3] 1 is a diagram showing a first embodiment of the present invention, and is a partial cross-sectional view of a power conversion device. [Figure 4] FIG. 5 is a partial cross-sectional view of a power conversion device for explaining a second embodiment of the present invention. [Figure 5] FIG. 4 is a diagram showing a second embodiment of the present invention, and is a partial cross-sectional view of a power conversion device. [Figure 6] FIG. 10 is a diagram showing a third embodiment of the present invention, and is a partial cross-sectional view of a power conversion device. DETAILED DESCRIPTION OF THE INVENTION

[0014] A first embodiment of the present invention will be described below with reference to Figures 1 to 3. Figure 1 is a plan view showing the configuration of the front surface of a substrate of a power conversion device according to this embodiment, Figure 2 is a plan view showing the configuration of the back surface of the same, and Figure 3 is a partial cross-sectional view of the power conversion device. First, there is the power board 1. This power board 1 is a four-layer printed circuit board (FR4: Flame Retardant Type 4) made of glass woven fabric made of glass fiber woven into a cloth-like material and impregnated with epoxy resin. On the surface of this power board 1, first conductive patterns 3, 5, and 7 of each phase of the motor (not shown) are provided.

[0015] A first substrate hole 9 is drilled at the upper end of the first conductive pattern 3 in Fig. 1, and a second substrate hole 11 is drilled at the lower end in Fig. 1. Similarly, the first conductive patterns 5 and 7 are also drilled with the first substrate hole 9 and second substrate hole 11, respectively.

[0016] Three upstream switching elements 21, 21, 21 and three downstream switching elements 23, 23, 23 are respectively arranged in pairs between the first substrate hole 9 and the second substrate hole 11 of the first conductive pattern 3. The upstream switching element 21 and the downstream switching element 23 of each pair are electrically connected via the first conductive pattern 3. Similarly, three upstream switching elements 21, 21, 21 and three downstream switching elements 23, 23, 23 are respectively arranged in pairs on the first conductive patterns 5 and 7.

[0017] In this embodiment, n-channel silicon metal oxide semiconductor field effect transistors (Si-MOSFETs) are used as the upstream switching element 21 and the downstream switching element 23. The upstream switching element 21 and the downstream switching element 23 are arranged so that the source terminal of the upstream switching element 21 and the drain terminal of the downstream switching element 23 face each other.

[0018] First conductive patterns 31, 33 of power supply lines are provided on the surface of the power board 1. First board holes 35 and second board holes 37 are drilled in these first conductive patterns 31, 33, respectively. In addition, other conductive patterns 41, 43, 45, and 47 are provided.

[0019] Looking at the back surface of the power board 1, as shown in Fig. 2, second conductive patterns 61, 63, and 65 for each phase of the motor are provided. A first board hole 67 and a second board hole 69 are drilled in the second conductive pattern 61. Similarly, a first board hole 67 and a second board hole 69 are drilled in the second conductive patterns 63 and 65, respectively. The second conductive patterns 61, 63, and 65 extend to the ends of the power board 1, as shown in Fig. 2.

[0020] Second conductive patterns 71 and 73 of power lines are provided on the back surface of the power board 1. First board holes 75 and second board holes 77 are drilled in these second conductive patterns 71 and 73, respectively. The second conductive patterns 71 and 73 extend to the ends of the power board 1, as shown in FIG.

[0021] The first conductive patterns 3, 5, and 7 on the front surface correspond to the second conductive patterns 61, 63, and 65 on the back surface, and similarly, the first conductive patterns 31 and 33 on the front surface correspond to the second conductive patterns 71 and 73 on the back surface.

[0022] Through-hole vias 101 are provided at appropriate locations on the power board 1, electrically connecting the front and back sides of the power board 1. Specifically, the first conductive patterns 3, 5, and 7 on the front side are electrically connected to the second conductive patterns 61, 63, and 65 on the back side via the through-hole vias 101. Also, the first conductive patterns 31 and 33 on the front side are electrically connected to the second conductive patterns 71 and 73 on the back side via the through-hole vias 101.

[0023] As shown in FIG. 3 , the power board 1 having the above configuration is placed on a heat sink 111. A resin external terminal 113 is fixed on the heat sink 111 with a fixing screw 115. A base 117 is protruded from an appropriate position on the heat sink 111. A bus bar 119 is placed on the heat sink 111 with an insulating thermally conductive sheet 121 interposed therebetween. An insulating sheet 123 is interposed between the bus bar 119 and the base 117. The bus bar 119 and the external terminal 113 are integrally molded in advance. The bus bar 119 has a long, thin plate shape, and five bus bars 119 corresponding to the second conductive patterns 61, 63, 65 and the second conductive patterns 71, 73 protrude from the external terminal 113 in a comb-teeth shape. Each bus bar 119 is pressure-welded to the two conductive patterns 61, 63, 65 and the second conductive patterns 71, 73.

[0024] The power board 1 already described is placed on the bus bar 119. Insulating fixing screws 125 are passed through the second board holes 11, 37 and the second board holes 69, 77 and are screwed to the base 117. Furthermore, conductive fixing screws 127 are passed through the first board holes 9, 35 and the first board holes 67, 75 and are screwed to the bus bar 119.

[0025] A control board (not shown) is provided separately from the power board 1, and various electronic components are mounted on this control board to control the upstream switching elements 21 and downstream switching elements 23. The control board is disposed above the power board 1 at a distance and fixed to the heat sink 111.

[0026] The operation of the above configuration will now be described. First, the electrical connections will be described. The upstream switching element 21 and downstream switching element 23 mounted on the surface are electrically connected via first conductive patterns 3, 5, and 7.

[0027] Furthermore, the first conductive patterns 3, 5, 7 on the front surface and the second conductive patterns 61, 63, 65 on the back surface are electrically connected via through-hole vias 101, 101, 101, respectively. Furthermore, the first conductive patterns 31, 33 on the front surface and the second conductive patterns 71, 73 on the back surface are electrically connected via through-hole vias 101, 101, respectively.

[0028] Furthermore, the second conductive patterns 61, 63, 65 and the second conductive patterns 71, 73 are electrically connected to a bus bar 119, and are electrically connected via this bus bar 119 to other devices (not shown). Furthermore, the electrical connection between the front side, rear side, and bus bar 119 is also ensured by conductive fixing screws 127 .

[0029] Next, heat dissipation will be described. On the front surface side of the power board 1, heat is generated mainly in the upstream switching elements 21 and downstream switching elements 23, and this heat is transferred to the bus bar 119 via the electrical connection route already explained, and from there to the heat sink 111 via the insulating heat conductive sheet 121, from where it is dissipated. The heat is also dissipated to the device side (not shown) via the bus bar 119.

[0030] According to the configuration of this embodiment, the following effects can be achieved. First, the heat generated on the surface of the power board 1 mainly from the upstream switching element 21 and the downstream switching element 23 can be effectively dissipated through the first conductive patterns 3, 5, 7, the through-hole vias 101, 101, 101, the second conductive patterns 61, 63, 65, the bus bar 119, the insulating thermally conductive sheet 121, and the heat sink 111. In addition, heat generated on the surface of the power board 1 can be effectively dissipated via the first conductive patterns 31, 33, the through-hole vias 101, 101, the second conductive patterns 71, 73, the bus bar 119, the insulating thermally conductive sheet 121, and the heat sink 111. Furthermore, heat can be effectively dissipated via the other conductive patterns 41, 43, 45, and 47. Furthermore, power board 1 and bus bar 119 are fixed to base 117 of heat sink 111 with insulating fixing screws 125 via insulating sheet 121, and power board 1 and bus bar 119 are fixed to base 117 with conductive fixing screws 127. Furthermore, bus bar 119 is integrally molded with external terminal 113 in advance, and external terminal 113 is fixed to heat sink 111 with fixing screws 115. Therefore, power board 1 and bus bar 119 can be firmly fixed to heat sink 111. This ensures strong adhesion between bus bar 119 and second conductive patterns 61, 63, 65 and second conductive patterns 71, 73.

[0031] Next, a second embodiment of the present invention will be described with reference to Figures 4 and 5. Figure 4 is a diagram illustrating a state in which power board 1 and bus bar 119 are fixed to base 117 via insulating sheet 123 by insulating fixing screws 125, and power board 1 and bus bar 119 are also fixed by conductive fixing screws 127. In this state, tightening insulating fixing screws 125 and conductive fixing screws 127 may cause bus bar 119 to become recessed between insulating fixing screws 125 and conductive fixing screws 127, which may weaken the contact between power board 1 and bus bar 119.

[0032] Therefore, in the case of the second embodiment, as shown in FIG. 5 , a protrusion 201 is provided on the surface of bus bar 119 facing power board 1, so that even if bus bar 119 between insulating fixing screw 125 and conductive fixing screw 127 becomes recessed, protrusion 201 firmly maintains contact between power board 1 and bus bar 119.

[0033] The protrusion 201 is formed by, for example, pressing, and is positioned at a position corresponding to a through-hole via (indicated by reference numeral 101 in FIG. 3). The other configurations are the same as those of the first embodiment, and the same parts in the drawings are denoted by the same reference numerals and their explanations are omitted.

[0034] According to the above configuration, it is possible to achieve the same effects as in the first embodiment, and also to make the contact between the power board 1 and the bus bar 119 stronger.

[0035] Next, a third embodiment of the present invention will be described with reference to Fig. 6. In this embodiment, the fastening portions of insulating fixing screw 125 and conductive fixing screw 127 are recessed portions 203, 205. With this configuration, even if bus bar 119 between insulating fixing screw 125 and conductive fixing screw 127 is recessed, protrusion 201 firmly maintains contact between power board 1 and bus bar 119.

[0036] According to the above configuration, it is possible to achieve the same effects as in the first embodiment, and also to make the contact between the power board 1 and the bus bar 119 stronger.

[0037] The present invention is not limited to the first to third embodiments. First, in the first to third embodiments, a silicon metal oxide semiconductor field effect transistor (Si-MOSFET) has been described as an example of an element mounted on the surface of a power substrate, but the element is not limited to this and may be another element. Furthermore, the number and arrangement of silicon metal oxide semiconductor field effect transistors (Si-MOSFETs) are merely examples, and various cases are envisaged. [Industrial Applicability]

[0038] The present invention relates to a power conversion device, and in particular to a power conversion device that employs a structure for dissipating heat through a conductive pattern, a bus bar, and a heat sink provided on a substrate, and that is devised to enable the substrate and the bus bar to be firmly fixed to the heat sink, thereby increasing the degree of adhesion between the bus bar and the conductive pattern, and is suitable for power conversion devices mounted on various vehicles, for example. [Explanation of symbols]

[0039] 1 Power Board 3 First conductive pattern 5. First conductive pattern 7 First conductive pattern 21 Si-MOSFET 23 Si-MOSFET 31 First conductive pattern 33 First conductive pattern 41 Conductive Pattern 43 Conductive Pattern 45 Conductive Pattern 47 Conductive Pattern 61 Second conductive pattern 63 Second conductive pattern 65 Second conductive pattern 71 Second conductive pattern 73 Second conductive pattern 111 Heatsink 113 External terminal 115 fixing screw 117 Pedestal 121 Insulating heat conductive sheet 123 Insulating Sheet 125 Insulated fixing screw 127 Conductive fixing screw

Claims

1. a substrate having an element and a first conductive pattern on a front surface and a second conductive pattern electrically connected to the first conductive pattern on a rear surface; A bus bar is installed on the back side of the board. An insulating heat conductive sheet is placed on the opposite side of the bus bar from the substrate, A heat sink is placed on the opposite side of the insulating thermally conductive sheet from the substrate. The power conversion device is characterized in that the substrate and the bus bar are fixed to the heat sink by insulating fixing screws.

2. 2. The power conversion device according to claim 1, The power conversion device is characterized in that the substrate is fixed to the bus bar by conductive fixing screws at positions different from the positions where the substrate is fixed by the insulating fixing screws.

3. 2. The power conversion device according to claim 1, The external terminals are fixed to the heat sink with fixing screws. The power conversion device is characterized in that the bus bar is integrally molded with the external terminal in advance.

4. 2. The power conversion device according to claim 1, a pedestal protruding from the heat sink at a position where the insulating fixing screw is fixed; The power conversion device is characterized in that an insulating sheet is interposed between the bus bar and the base.

5. 5. The power conversion device according to claim 4, The power conversion device is characterized in that the insulating sheet has a higher hardness than the insulating heat-conductive sheet.

6. 2. The power conversion device according to claim 1, A power conversion device, characterized in that the first conductive pattern and the second conductive pattern are electrically connected via through-holes.

7. 2. The power conversion device according to claim 1, The power conversion device is characterized in that the elements are an upstream switching element and a downstream switching element electrically connected via the first conductive pattern.

8. 8. The power conversion device according to claim 7, the first conductive pattern, the second conductive pattern, and the bus bar are disposed in parallel to each other in an elongated shape, The power conversion device is characterized in that a plurality of pairs of the upstream switching element and the downstream switching element are arranged along the longitudinal direction of the first conductive pattern.

9. 3. The power conversion device according to claim 2, a protrusion is provided on the bus bar between the fastening position with the insulating fastening screw and the fastening position with the conductive fastening screw.

10. 3. The power conversion device according to claim 2, The power conversion device is characterized in that recesses are formed in the bus bars at the fastening positions with the insulating fastening screws and at the fastening positions with the conductive fastening screws.

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