WO2023007546A1 - 電子装置及び電動パワーステアリング装置 - Google Patents
電子装置及び電動パワーステアリング装置 Download PDFInfo
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- WO2023007546A1 WO2023007546A1 PCT/JP2021/027530 JP2021027530W WO2023007546A1 WO 2023007546 A1 WO2023007546 A1 WO 2023007546A1 JP 2021027530 W JP2021027530 W JP 2021027530W WO 2023007546 A1 WO2023007546 A1 WO 2023007546A1
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- metal plate
- heat
- electronic device
- thermally conductive
- substrate
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- 229910052751 metal Inorganic materials 0.000 claims abstract description 216
- 239000002184 metal Substances 0.000 claims abstract description 216
- 239000000758 substrate Substances 0.000 claims abstract description 70
- 230000017525 heat dissipation Effects 0.000 claims abstract description 20
- 238000010438 heat treatment Methods 0.000 claims description 100
- 239000012212 insulator Substances 0.000 claims description 78
- 125000006850 spacer group Chemical group 0.000 claims description 18
- 239000000463 material Substances 0.000 claims description 17
- 230000005855 radiation Effects 0.000 claims description 16
- 229910000679 solder Inorganic materials 0.000 claims description 13
- 239000004519 grease Substances 0.000 claims description 6
- 239000000853 adhesive Substances 0.000 claims description 4
- 230000001070 adhesive effect Effects 0.000 claims description 4
- 238000005476 soldering Methods 0.000 claims description 4
- 239000004065 semiconductor Substances 0.000 description 32
- 238000000034 method Methods 0.000 description 17
- 230000004048 modification Effects 0.000 description 15
- 238000012986 modification Methods 0.000 description 15
- 230000000694 effects Effects 0.000 description 13
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 10
- 229910052802 copper Inorganic materials 0.000 description 10
- 239000010949 copper Substances 0.000 description 10
- 239000003990 capacitor Substances 0.000 description 8
- 238000004519 manufacturing process Methods 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
- 238000010292 electrical insulation Methods 0.000 description 3
- 239000007769 metal material Substances 0.000 description 3
- 230000008859 change Effects 0.000 description 2
- 239000011810 insulating material Substances 0.000 description 2
- 230000002250 progressing effect Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 230000005856 abnormality Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000009429 electrical wiring Methods 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 239000007779 soft material Substances 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
- H01L23/36—Selection of materials, or shaping, to facilitate cooling or heating, e.g. heatsinks
Definitions
- the present disclosure relates to electronic devices and electric power steering devices.
- Patent Document 1 describes a conventional electric power steering device.
- a conventional electronic device includes, for example, a substrate having a circuit pattern, a heat-generating element provided with a heat spreader and mounted on the substrate, a heat-conducting insulator that conducts heat generated from the heat-generating element, and a heat-dissipating material that dissipates heat to the outside of the electronic device. and a heat sink.
- FIG. 12 of Patent Document 1 shows a structure in which heat dissipation gel is filled between a heating element and a heat sink (corresponding to a frame in Patent Document 1).
- the miniaturization of heating elements such as power MOS-FETs is progressing. For this reason, the size of the package including the heating element is becoming smaller. As a result, the area of the heat spreader that dissipates the heat generated from the heating element is reduced. It cannot be expected to increase the thermal conductivity of the heat dissipation gel, and there is a limit to lowering the thermal resistance from the heating element to the heat sink.
- the thickness of the copper film formed on the inner walls of the through-holes is thin. , there is a limit to lowering the thermal resistance.
- An object of the present invention is to provide an electronic device and an electric power steering apparatus equipped with the electronic device.
- An electronic device includes a substrate having a circuit pattern, a heat generating element having a top heat radiation portion disposed on the substrate and located on the opposite side of the substrate, and a heat sink disposed on the top heat radiation portion.
- the electronic device it is possible to efficiently dissipate the heat generated from the heating element mounted on the substrate, and to provide an electronic device at a low price that does not hinder the miniaturization of the heating element.
- FIG. 1 is a cross-sectional view showing the configuration of an electronic device according to Embodiment 1;
- FIG. FIG. 4 is a cross-sectional view showing the configuration of the electronic device according to Embodiment 1 and showing a modification of the metal plate;
- FIG. 4 is a cross-sectional view showing the configuration of the electronic device according to Embodiment 1 and showing a modification of the metal plate;
- FIG. 8 is a plan view showing the configuration of an electronic device according to Embodiment 2;
- 4B is a cross-sectional view showing the configuration of the electronic device according to Embodiment 2, taken along line AA shown in FIG. 4A.
- FIG. 4B is a cross-sectional view showing the configuration of the electronic device according to Embodiment 2, taken along line BB shown in FIG.
- FIG. FIG. 10 is a plan view showing a modification of the electronic device according to the second embodiment
- 4D is a cross-sectional view showing a modification of the electronic device according to the second embodiment, taken along line CC shown in FIG. 4D.
- FIG. 4E is a cross-sectional view showing a modification of the electronic device according to Embodiment 2, and is an enlarged view showing D in FIG. 4E.
- FIG. 11 is a perspective view showing the configuration of an electronic device according to Embodiment 2
- FIG. 5B is a cross-sectional view showing the configuration of the electronic device according to the second embodiment, taken along line CC shown in FIG. 5A.
- FIG. 10 is a plan view showing a modification of the electronic device according to the second embodiment
- 4D is a cross-sectional view showing a modification of the electronic device according to the second embodiment, taken along line CC shown in FIG. 4D.
- FIG. 4E is a cross-sectional view showing a modification of the electronic device according to Embod
- FIG. 10 is a circuit block diagram showing the configuration of an electric power steering system including an electronic device according to Embodiment 3;
- FIG. 11 is an exploded view showing a plurality of components forming an electric power steering device including an electronic device according to Embodiment 3;
- FIG. 10 is a perspective view showing a board that constitutes an electric power steering device that includes an electronic device according to Embodiment 3;
- FIG. 8B is a perspective view showing a substrate constituting an electric power steering device including an electronic device according to Embodiment 3, and is an enlarged view showing a portion indicated by symbol D in FIG. 8A.
- FIG. 11 is an exploded view of a redundant electric power steering device according to Embodiment 4;
- thermal design Before describing the embodiments, the basics of thermal design will be described. 2. Description of the Related Art Along with the evolution of semiconductor processes, the miniaturization of heating elements such as power MOS-FETs is progressing. If a heating element having a performance equal to or higher than that of a current heating element is miniaturized, the mounting density of an electronic device using a part having the heating element will be improved, and the size of the electronic device will be reduced.
- a package for example, an FET package
- the area of a heat spreader that dissipates heat generated from the heating element also becomes smaller. Note that if the performance of the heating element does not change, the amount of heat generated from the heating element is the same.
- a heat dissipation structure in which heat-conducting insulating grease is interposed between a heat-generating component (heat-generating element) and a heat sink.
- the heat dissipation performance of the heat dissipation structure is determined by the thermal resistance from the heat generating component to the heat sink and the outside air.
- an FET heat generating element, heat generating component
- a heat conductive insulating member provided between the FET and the heat sink.
- a thermal resistance R ⁇ from an FET, which is a heat-generating component, to a heat sink can be expressed by the following equation.
- R ⁇ t/(S ⁇ ) [°C/W]
- t indicates the thickness [m] of the thermally conductive insulator.
- S indicates the area of the thermally conductive insulator (the area of the heat spreader) [m 2 ].
- ⁇ indicates the thermal conductivity [W/m ⁇ K] of the thermally conductive insulator. Note that the thermal resistance of the heat spreader is ignored here.
- a heat spreader is usually made of copper.
- the thermal conductivity of copper is approximately 400 W/m ⁇ K.
- the thermal conductivity of the thermally conductive insulator is usually several to 10 W/m ⁇ K. For this reason, the thermal conductivity of the thermally conductive insulator is orders of magnitude different from that of copper. For this reason, ignoring the thermal resistance of the heat spreader has negligible effect on the thermal resistance R ⁇ .
- the heat spreader of the FET is normally electrically connected to the internal electrodes of the FET.
- the heat spreader should be electrically isolated from the heat sink. Therefore, heat-conducting insulating grease, adhesives, sheets, etc. are generally used in order to obtain electrical insulation.
- high precision is required in the processing and assembly of the structure that forms the heat dissipation system (heat dissipation member, heat dissipation structure, heat dissipation path). .
- heat dissipation member heat dissipation member, heat dissipation structure, heat dissipation path.
- there is a limit to reducing the thickness t of the heat-conducting insulator and high processing accuracy is required.
- Method 2 The area S of the thermally conductive insulator is determined by the area of the heat spreader of the FET. Therefore, it is impossible to increase the area S. Furthermore, increasing the size of the FET package to increase the area of the heat spreader goes against the trend toward miniaturization of the FET package, which is unrealistic.
- Thermal conductivity of thermal conductive insulating grease, adhesives and sheets is usually several to 10 W/m ⁇ K.
- Thermally conductive insulators exist that have thermal conductivities higher than this figure, but such thermally conductive insulators are very expensive and not suitable for mass production designs.
- the thickness direction of the electronic device 1 (in other words, the thickness direction of the substrate 100) is defined as the Z direction, and the directions orthogonal to the Z direction are the X direction and the X direction.
- the Y direction Define the Y direction.
- thickness means the distance in the Z direction
- area means the area of a plane parallel to the X and Y directions.
- contact area means an area where two members are in contact with each other.
- the electronic device 1 includes a substrate 100, a heat generating element 200, a heat conducting member 300, a metal plate 400, a heat conducting insulator 500, and a heat sink 600.
- the substrate 100 is, for example, a known printed circuit board.
- a circuit pattern 100P is formed on the substrate 100 .
- a circuit pattern 100P is formed on one surface 100F (first surface, upper surface) of the substrate 100.
- One surface 100F of the substrate 100 shows a structure in which the plurality of members 200, 300, 400, 500, and 600 described above are laminated in order. In the following description, one surface 100F will be referred to as the first surface 100F.
- connection terminals 101 forming part of the circuit pattern 100P are formed on the first surface 100F of the substrate 100.
- the positions where the connection terminals 101 are formed on the first surface 100 ⁇ /b>F can be changed as appropriate according to the design of the electronic device 1 .
- the connection terminals 101 are formed at positions corresponding to the positions of the element terminals 203 of the heating element 200 .
- Members other than the plurality of members 200 , 300 , 400 , 500 , and 600 described above may be arranged on the substrate 100 .
- a control unit (a control circuit, an IC chip, or the like) that controls driving of the heating elements 200 may be mounted on the substrate 100 .
- the controller may be connected to the circuit pattern 100P of the substrate 100.
- FIG. A circuit pattern may also be formed on the other surface 100S of the substrate 100 (the second surface opposite to the first surface, the back surface). In the following description, the other surface 100S is called the second surface 100S.
- a heating element 200 is arranged on the substrate 100 .
- the heating element 200 is mounted on the first surface 100F of the substrate 100.
- the heating element 200 is, for example, a power MOS-FET.
- the heating element 200 can be called a power element.
- a power MOS-FET has a built-in FET chip. In the following description, the heating element may be referred to as power MOS-FET or FET.
- the heating element 200 has a drain electrode, a source electrode, and a gate electrode (control terminal).
- the heating element 200 includes an upper heat spreader 201 (upper heat radiation portion), a lower heat spreader 202 (substrate facing surface), and element terminals 203 .
- the upper heat spreader 201 faces the metal plate 400 .
- the top heat spreader 201 is located on the side opposite to the first surface 100F of the substrate 100 .
- the lower surface heat spreader 202 faces the first surface 100F of the substrate 100 .
- the element terminal 203 corresponds to the tip of the lead wire extending from the side surface of the heating element 200 .
- the positions of the element terminals 203 correspond to the positions of the connection terminals 101 of the substrate 100 .
- the element terminals 203 are soldered to the connection terminals 101 .
- An element terminal 203 is a terminal for controlling the heating element 200 .
- a control signal for controlling the heating element 200 is input to the heating element 200 through the circuit pattern 100P of the substrate 100, the connection terminal 101, and the element terminal 203.
- FIG. The entire heating element 200 is covered with resin. That is, the heating element 200 is packaged with resin.
- FIG. 1 shows a structure in which the heat generating element 200 includes the lower surface heat spreader 202, in the present embodiment, heat dissipation from the upper surface heat spreader 201 toward the metal plate 400 will be described.
- the heat conducting member 300 is arranged on the top heat spreader 201 .
- the heat conducting member 300 is provided between the upper heat spreader 201 and the metal plate 400 .
- the heat conducting member 300 thermally and mechanically couples the top heat spreader 201 and the metal plate 400 .
- the heat conducting member 300 is a thermal coupling member that joins the upper heat spreader 201 and the metal plate 400 together.
- a material of the heat conducting member 300 a material having a high heat conductivity is adopted, and for example, a metallic material such as solder or silver paste is used. Also, as the material of the heat conducting member 300, a material having electrical conductivity may be used.
- the thermal conductivity of the thermally conductive member 300 is greater than that of the thermally conductive insulator 500 .
- the thermal conductivity of the solder is approximately 50 W/m ⁇ K.
- the thickness of the solder can be freely set, and the thickness of the solder can be reduced. Therefore, the thermal resistance of solder can be reduced.
- a metal plate 400 is arranged on the top heat spreader 201 .
- a metal material having excellent thermal conductivity is used, such as copper.
- the thermal conductivity of copper is approximately 400 W/m ⁇ K.
- the thickness of the metal plate 400 is preferably within the range of 0.5 mm to 1.0 mm, for example. The thickness of metal plate 400 is not limited to this thickness range.
- the shape of the metal plate 400 is a flat plate.
- the metal plate 400 has a first metal surface 400F and a second metal surface 400S opposite to the first metal surface 400F.
- the first metal surface 400F is in contact with the thermally conductive insulator 500 .
- the second metal surface 400S is in contact with the heat conducting member 300.
- each of the first metal surface 400F and the second metal surface 400S is a flat surface.
- the thickness of metal plate 400 is set in view of the thermal conductivity of metal plate 400 .
- the metal plate 400 has the same potential as either the drain electrode or the source electrode of the heating element 200 . Therefore, if the metal plate 400 is electrically connected to the heat sink 600 , a short circuit will occur through the heat sink 600 . To avoid such shorts, it is necessary to electrically insulate the metal plate 400 from the heatsink 600 .
- the area of the metal plate 400 can be freely adjusted. For example, it is possible to make the area of the metal plate 400 larger than the area of the heating element 200 (the area of the upper surface heat spreader 201). It is also possible to increase the contact area of the thermally conductive insulator 500 with respect to the metal plate 400 .
- thermally conductive insulator 500 is placed on the metal plate 400 .
- a thermally conductive insulator 500 is filled between the metal plate 400 and the heat sink 600 .
- the thermally conductive insulator 500 is a member that conducts heat from the metal plate 400 to the heat sink 600 .
- the thermally conductive insulator 500 is a member that electrically insulates the metal plate 400 and the heat sink 600 from each other.
- a known material is used, such as thermally conductive grease or thermally conductive adhesive.
- the thermal conductivity of the thermally conductive insulator 500 is generally several to 10 W/m ⁇ K.
- the shape of the heat conductive insulator 500 can be freely set. Furthermore, the area of the thermally conductive insulator 500 can also be freely adjusted. For example, depending on the gap distance between the metal plate 400 and the heat sink 600, the thickness of the thermally conductive insulator 500 can be reduced.
- the contact area between the metal plate 400 and the thermally conductive insulator 500 is larger than the contact area between the heating element 200 and the thermally conductive member 300 .
- a heat sink 600 is disposed on the thermally conductive insulator 500 .
- the structure of the heat sink 600 for example, a known structure having a plurality of fins is adopted.
- a metal material having excellent thermal conductivity is used, such as copper or aluminum, for example.
- the heat diffused inside the metal plate 400 is transmitted to the heat sink 600 via the thermally conductive insulator 500 .
- the thermal resistance of the thermally conductive insulator 500 can be lowered by the thermal conductivity of the thermally conductive insulator 500 (approximately several to 10 W/m ⁇ K).
- 200 can be larger than the area of the top heat spreader 201 .
- the thermal resistance of the electronic device 1 can be reduced by the metal plate 400 .
- the size of the metal plate 400 that is, the area of the metal plate 400 is set so that the region 200R including the heat generating elements 200 and the element terminals 203 and the metal plate 400 overlap when viewed from the Z direction.
- the thermal resistance of the electronic device 1 can be reduced without changing the packaging density of the electronic device 1 as a whole.
- the thermal resistance can be further reduced.
- FIGS. 2 and 3 the same members as in the electronic device 1 shown in FIG.
- the metal plate 400 has convex portions 401 .
- the convex portion 401 is a portion protruding from the second metal surface 400S toward the heating element 200.
- the height of the convex portion 401 that is, the distance from the second metal surface 400S to the end face 400T of the convex portion 401 in the Z direction can be adjusted as appropriate.
- An inclined surface 400I is formed between the second metal surface 400S and the end surface 400T. According to this configuration, it is possible not only to obtain the same effect as or similar to that of the electronic device 1 according to Embodiment 1 described above, but also to increase the distance between the substrate 100 and the second metal surface 400S of the metal plate 400, for example. effective when
- solder is used as the heat conducting member 300 . Therefore, the shape of the solder between the upper heat spreader 201 and the metal plate 400 can be freely adjusted.
- solder is formed between the end surface 400T of the convex portion 401 and the upper heat spreader 201 and between the inclined surface 400I and the upper heat spreader 201 .
- the exposed portion of the solder exposed in the space between the metal plate 400 and the heating element 200 is formed with a curved surface. That is, the solder is formed to have a fillet shape. Solder having a fillet shape can improve the reliability of bonding between top heat spreader 201 and metal plate 400 .
- Modification 1 of the metal plate differs from Embodiment 1 described above in the structure formed between heat sink 600 and metal plate 400 .
- a spacer 501 and a thermally conductive insulator 500 are arranged between the heat sink 600 and the metal plate 400 .
- a known insulating material is used as the material of the spacer 501 .
- Spacer 501 has strength necessary to maintain the gap formed between heat sink 600 and metal plate 400 .
- the spacer 501 is directly fixed to the surface of the heat sink 600 facing the metal plate 400 . After that, the heat sink 600 and the metal plate 400 are joined so as to sandwich the spacer 501 . Thereby, the gap between the metal plate 400 and the heat sink 600 is determined by the thickness of the spacer 501 . Further, the gap formed by the spacer 501 between the metal plate 400 and the heat sink 600 is filled with the thermally conductive insulator 500 .
- the spacer 501 can reliably form a gap to be filled with the thermally conductive insulator 500 . Furthermore, even when a soft material such as grease is used as the material of the thermally conductive insulator 500 , the gap formed by the spacer 501 can be filled with the thermally conductive insulator 500 .
- the position where the spacer 501 is formed is preferably, for example, the surrounding area surrounding the thermally conductive insulator 500 .
- the gaps surrounded by the spacers 501 in the X direction and the Y direction can be filled with the thermally conductive insulator 500 .
- the metal plate 400 has a convex portion 401, a concave portion 402, and an inclined surface 400I.
- the convex portion 401 is a portion protruding from the second metal surface 400S toward the heating element 200, similarly to the structure shown in FIG.
- the inclined surface 400I is formed between the second metal surface 400S and the end surface 400T, similar to the structure shown in FIG.
- the recessed portion 402 is a portion that is recessed from the first metal surface 400F toward the heating element 200. As shown in FIG. The depth of the recess 402, that is, the distance in the Z direction from the first metal surface 400F to the bottom surface 400R of the recess 402 can be adjusted as appropriate. As a method of forming the recess 402, there is a method of forming the recess 402 in the flat metal plate 400 shown in FIG. 1 using a known press working method or the like.
- Embodiment 2 In the first embodiment described above, the case where the electronic device 1 includes one heating element 200 has been described. In Embodiment 2, a case where an electronic device includes a plurality of heating elements will be described with reference to FIGS. 4A to 4C. 4A to 4C, the same members in the electronic device 1 shown in FIGS. 1 to 3 are denoted by the same reference numerals, and descriptions thereof are omitted or simplified.
- the electronic device 2 includes eight heat generating elements 200 functioning as power MOS-FETs and three shunt resistors 204 (heat generating components). Eight heating elements 200 and three shunt resistors 204 are provided on the substrate 100 .
- a shunt resistor is a heat-generating component that generates heat.
- heating elements 200 are arranged along the X direction.
- Two heating elements 200 are arranged along the Y direction.
- the top heat spreader 201 of each of the eight heating elements 200 functions as a drain electrode.
- the four heating elements 200 arranged in the X direction constitute one element group. That is, in the example shown in FIG. 4A, the electronic device 2 includes two element groups (first element group 200G1 and second element group 200G2).
- the first element group 200G1 is connected to four first metal plates 400A.
- the second element group 200G2 is connected to one second metal plate 400B.
- the first metal plate 400A and the second metal plate 400B are arranged in the Y direction and function as separate wiring from each other.
- the second element group 200G2 is arranged between the first element group 200G1 and the shunt resistor 204 in the Y direction.
- the four heating elements 200 (the plurality of first heating elements, the plurality of heating elements) forming the first element group 200G1 are connected to the four first metal plates 400A via the heat conducting members 300.
- Each of the four heat generating elements 200 has a top heat spreader 201 (first top heat radiation part, top heat radiation part) located on the opposite side of the substrate 100 .
- the four first metal plates 400A are arranged on the heat conducting member 300 and arranged along the direction in which the four heating elements 200 are arranged (X direction).
- the four first metal plates 400A are separated from each other.
- the upper heat spreader 201 is connected to each of the four first metal plates 400A via the heat conducting member 300.
- the upper surface heat spreader 201 of one heating element 200 is electrically connected to one first metal plate 400A via the heat conducting member 300.
- the top heat spreaders 201 of the four heating elements 200 are not electrically connected to each other. Therefore, the potentials of the four upper heat spreaders 201 of the four heating elements 200 are different from each other. That is, in the first element group 200G1, the upper heat spreaders 201 (drain electrodes) are electrically independent of each other.
- Each of the four heating elements 200 has a top heat spreader 201 (second top heat radiation part, top heat radiation part) located on the opposite side of the substrate 100 .
- the second metal plate 400B is arranged on the heat conducting member 300 and extends along the direction in which the four heating elements 200 are arranged (X direction).
- the second metal plate 400B electrically connects the four heating elements 200 to each other.
- the second metal plate 400B is electrically independent from the first metal plate 400A.
- the top heat spreader 201 is connected to one second metal plate 400B via the heat conducting member 300.
- the four upper heat spreaders 201 of the four heating elements 200 are electrically connected to one second metal plate 400B via the heat conducting member 300.
- the potentials of the four top heat spreaders 201 are the same.
- a second metal plate 400B shown in FIG. 4A is, for example, wiring corresponding to reference numeral 400a shown in a circuit block diagram shown in FIG. 6, which will be described later.
- Shunt resistor 204 has an electrode 204E.
- the electrode 204E of the shunt resistor 204 is joined to the circuit pattern 100P of the substrate 100 by soldering.
- a third metal plate 400C is provided between the position 204R where the electrode 204E is joined to the circuit pattern 100P and the thermally conductive insulator 500.
- the third metal plates 400C electrically connected to the three shunt resistors 204 are independent of each other. That is, the two third metal plates 400C are not electrically connected between the two shunt resistors 204 adjacent to each other.
- first element group 200G1 and the second element group 200G2 may be simply referred to as "element group 200G”.
- first metal plate 400A, the second metal plate 400B, and the third metal plate 400C may be simply referred to as "metal plates 400".
- first element group 200G1 may be referred to as an "upper element group 200G1”.
- the second element group 200G2 may be referred to as a "lower element group 200G2".
- the plurality of heating elements 200 forming the first element group 200G1 are connected to the plurality of first metal plates 400A. Furthermore, the plurality of heat generating elements 200 forming the second element group 200G2 are connected to one second metal plate 400B. This allows the first metal plate 400A and the second metal plate 400B to function as electrical wiring members. As a result, wiring density can be improved.
- the number of element groups (first element group 200G1, second element group 200G2) arranged in the Y direction is two, but the number of element groups is two or more.
- the number of rows of the plurality of first metal plates 400A arranged along the X direction may be two or more (the plurality of metal plates 400).
- the number of rows of second metal plates 400B extending in the X direction may be two or more (plurality of metal plates 400).
- the number of rows of metal plates is three or more, the two selected rows of metal plates correspond to the rows of the plurality of first metal plates 400A and the rows of the second metal plates 400B.
- the planar pattern of metal plate 400 (first metal plate 400A, second metal plate 400B, third metal plate 400C) can be designed to be wider and thicker than circuit pattern 100P formed on substrate 100. . Therefore, a large current can be applied to the metal plate 400 .
- the configuration of the metal plate 400 shown in FIGS. 4A to 4C is the same as the configuration described in the embodiment shown in FIGS. 1 to 3 above.
- the metal plate 400 When a large current is supplied to the metal plate 400, the metal plate 400 also generates heat due to the electrical resistance of the material forming the metal plate 400. However, since the metal plate 400 is thermally connected to the heat sink 600 via the thermally conductive insulator 500 , the heat generated from the metal plate 400 is sufficiently radiated from the heat sink 600 . Therefore, a large current can be supplied to the metal plate 400 without considering heat generation from the metal plate 400 .
- the metal plate 400 can be designed to be fine and thin. In this case, the electronic device 2 can be miniaturized, and the manufacturing cost of the electronic device 2 can be reduced.
- the insulating member 800 insulates a plurality of mutually independent first metal plates 400A, second metal plates 400B, and third metal plates 400C, and integrates them into one component.
- one component is composed of the plurality of first metal plates 400A, second metal plates 400B, third metal plates 400C, and insulating members 800 .
- a known material is used as an insulating material forming the insulating member 800 .
- the thickness of the heat-conducting insulator 500 is determined by the thickness of the insulating member 800 .
- the insulating member 800 can function as a spacer.
- the insulating member 800 determines the distance between the metal plate 400 and the heat sink 600 .
- the structure, material, and shape of the spacer are, for example, the same as the spacer 501 shown in FIG.
- the gap formed by the insulating member 800 is filled with the thermally conductive insulator 500 .
- the thermally conductive insulator 500 can be reliably arranged between the metal plate 400 and the heat sink 600 .
- the insulating member 800 can determine the thickness of the thermally conductive insulator 500 .
- the heating element 200 On the upper surface of the heating element 200, there are also parts that do not have a heat spreader, such as parts such as shunt resistors.
- parts such as shunt resistors.
- FIG. 4C the state where the shunt resistor 204 is mounted on the electronic device 2 is shown.
- a shunt resistor 204 is mounted on the first surface 100F of the substrate 100 .
- the shunt resistor 204 is a surface-mounted resistive element (heat generating component).
- the shunt resistor 204 has electrodes 204E provided on both sides of the shunt resistor 204 .
- the electrode 204E of the shunt resistor 204 is joined to the circuit pattern 100P of the substrate 100 by soldering. Heat generated by energizing the shunt resistor 204 is mainly radiated from the electrode 204E through the circuit pattern 100P.
- the thermal conductivity of the material forming the circuit pattern 100P and the substrate 100 is low, and the heat radiation efficiency is poor.
- a third metal plate 400C is soldered to a position 204R where the electrode 204E of the shunt resistor 204 is soldered to the circuit pattern 100P of the substrate 100.
- the electronic device 2 has the first metal plate 400A, the second metal plate 400B, and the third metal plate 400C.
- the thermal resistance can be reduced by increasing the area of the thermally conductive insulator 500 facing the heat sink 600 and the area of the metal plates 400A, 400B, and 400C.
- the circuit A third metal plate 400C may be soldered to the pattern 100P. As a result, heat can be dissipated from the heat sink 600 via the third metal plate 400C and the thermally conductive insulator 500, and thermal resistance can be reduced.
- the insulating member 800 insulates and fixes the metal plates 400A, 400B, and 400C from each other.
- the metal plates 400A, 400B, 400C and the insulating member 800 constitute one component.
- Dimension A shown in FIG. 5B indicates the thickness of the thermally conductive insulator 500 . As described above, the thinner the thickness (dimension A), the smaller the thermal resistance, and the better the heat dissipation performance.
- the thickness (dimension A) of the thermally conductive insulator 500 in consideration of the dimensional tolerances and assembly tolerances of the parts that make up the electronic device 2. However, if the dimensional tolerance and the assembly tolerance are made too small, the manufacturing cost of the electronic device 2 will increase.
- metal plates 400A, 400B, and 400C are formed by insert molding, for example, metal plates 400A, 400B, and 400C and insulating member 800 can be integrated using a single mold. . Therefore, it is relatively easy to reduce the tolerance of the thickness (dimension B) of the insulating member 800 at low cost.
- the fixing structure of the insulating member 800 to the heat sink 600 by fixing the insulating member 800 directly against the heat sink 600, for example, by adopting a fixing structure using screws 900, the heat conductive insulator 500 can be fixed. thickness can be reduced. As a result, it is possible to design and manufacture an electronic device 2 with low thermal resistance, low cost, and high heat dissipation performance.
- insulating member 800 may be provided with ribs 801 .
- Rib 801 is provided on end surface 800 ⁇ /b>F of insulating member 800 facing heat sink 600 .
- grooves 600 ⁇ /b>G are provided in heat sink 600 at positions corresponding to ribs 801 .
- a rib 801 is inserted into the groove 600G to fix the insulating member 800 and the heat sink 600 together. Therefore, even if the thickness (dimension B) of the insulating member 800 is small, by adopting the structure in which the ribs 801 are fitted in the grooves 600G, the size of the electronic device 2 in the Z direction does not increase, and the heat sink A positioning function when assembling the insulating member 800 to 600 can be realized.
- the electronic device 2 it is possible to obtain the same or similar effects as those of the electronic device 1 according to the first embodiment described above. Furthermore, even when the electronic device 2 includes a plurality of heating elements 200, the first metal plate 400A, the second metal plate 400B, and the third metal plate 400C can be integrated. Furthermore, by fixing the plurality of metal plates 400A, 400B, and 400C with the insulating member 800, the thickness of the thermally conductive insulator 500 can be set thin so as to be determined by the thickness of the insulating member 800. FIG. Thereby, a high heat dissipation structure can be achieved. By arranging other components such as a control circuit on the second surface 100S of the substrate 100, it is possible to realize a compact and low-cost electronic device 2. FIG.
- the heat generated from the circuit pattern 100P is also dissipated through the metal plate 400C, there is no need to use a copper substrate having a large thickness that allows a large current to pass through, and the cost of the electronic device 2 can be reduced. Further reduction is possible.
- an electronic device 2A As shown in FIGS. 4D to 4F, an electronic device 2A according to a modification of the second embodiment includes a heating element 250 functioning as a power MOS-FET in addition to the structure of the electronic device 2 shown in FIG. 4A.
- the heating element 250 has a structure similar to that of the heating element 200 shown in FIG.
- the bottom heat spreader 202 is the drain electrode or source electrode of the heating element 250 .
- the heating element 250 is arranged next to the rightmost shunt resistor 304 of the three shunt resistors 204 in the X direction.
- the electrode 304E of the right shunt resistor 304 is soldered to the circuit pattern 100P of the substrate 100 at the position 304R.
- the third metal plate 400C is soldered to this position 304R.
- a portion of the third metal plate 400C arranged at the position 304R is bent so as to form an S shape in a cross-sectional view.
- the bent third metal plate 400C is joined to the circuit pattern 100P at the position 304R. Thereby, the electrode 304E and the third metal plate 400C are connected via the position 304R.
- the lower surface heat spreader 202 of the heating element 250 is soldered to the circuit pattern 100P of the substrate 100 at the position 304S.
- the third metal plate 400C is soldered to this position 304S.
- a portion of the third metal plate 400C arranged at the position 304S is bent to form an S shape in cross-sectional view.
- the bent third metal plate 400C is joined to the circuit pattern 100P at the position 304S. Thereby, the lower surface heat spreader 202 and the third metal plate 400C are connected via the position 304S.
- one electrode 304E of the right shunt resistor 304 and the lower surface heat spreader 202 of the heating element 250 are electrically connected via the circuit pattern 100P and the third metal plate 400C. Therefore, electrode 304E and bottom heat spreader 202 have the same potential. Furthermore, both the right shunt resistor 304 and the heating element 250 are heat generating components, and the heat generated from these components is dissipated to the heat sink 600 via the third metal plate 400C and the thermally conductive insulator 500. be. Further, heat generated from the circuit pattern 100P is also dissipated to the heat sink 600 via the third metal plate 400C and the thermally conductive insulator 500. FIG.
- the electronic device 2A it is possible to obtain the same or similar effects as those of the electronic device 2 according to the second embodiment described above.
- heat generated from the right shunt resistor 304, the heating element 250, and the circuit pattern 100P can be dissipated to the heat sink 600 by the third metal plate 400C. Therefore, there is no need to use a copper substrate having a large thickness that allows a large amount of current to flow, and the price of the electronic device 2A can be further reduced.
- Embodiment 3 In Embodiments 1 and 2, the case where the electronic device 1 includes one heating element 200 and the case where the electronic devices 2 and 2A include a plurality of heating elements 200 have been described. In Embodiment 3, a case where an electronic device having a plurality of heating elements is applied to an electric power steering system will be described.
- FIGS. 6 to 8B the same members in the configuration shown in FIGS. 1 to 5B are denoted by the same reference numerals, and descriptions thereof are omitted or simplified.
- the wirings (reference numerals 400a, 400b, 400c, and 400d) indicated by thick lines correspond to wirings through which a large current flows.
- Components included in the wiring paths indicated by the wirings 400a, 400b, 400c, and 400d are heat-generating components (heat-generating elements 200).
- the electric power steering device 3 is a developed view of the motor and controller that constitute the electric power steering device 3 .
- 8A and 8B are perspective views showing a substrate portion that constitutes the electric power steering device 3.
- the electric power steering device 3 includes a control device 3C, a speed reduction device (not shown), an electric motor 5, a torque sensor 8, and a battery 9. Further, the electric power steering device 3 includes a power connector 16 and a vehicle-side signal connector 17 .
- the control device 3C controls driving of the electric motor 5.
- a speed reducer (not shown) reduces the rotational speed of the electric motor 5 .
- the electric motor 5 outputs auxiliary torque to the steering wheel of the vehicle.
- the electric motor 5 is a three-phase brushless motor.
- the electric motor 5 comprises a rotor 18 and a stator 19 with a UVW armature winding.
- a torque sensor 8 detects the steering torque of the steering wheel.
- the battery 9 supplies the electric motor 5 with current for driving the electric motor 5 .
- Power connector 16 electrically connects battery 9 and control device 3C.
- the vehicle-side signal connector 17 electrically connects the torque sensor 8 and other control terminals to the control device 3C.
- the control device 3C includes capacitors 15a and 15b, shunt resistors 208U, 208V and 208W, semiconductor switching elements 206U, 206V, 206W, 207U, 207V and 207W, semiconductor switching elements 209U, 209V and 209W, and a coil 14a. , and semiconductor switching elements 205a and 205b. Further, the control device 3C includes a rotation sensor 6, a microcomputer 10, a drive circuit 11, and a substrate 100.
- the capacitors 15 a and 15 b are large-capacity capacitors for absorbing the ripple component of the motor current IM flowing through the electric motor 5 .
- Capacitors 15a and 15b are, for example, ripple capacitors.
- Shunt resistors 208U, 208V, 208W detect motor current IM. Note that the shunt resistors 208U, 208V, and 208W may be referred to as the shunt resistor 208 in the following description.
- a semiconductor switching element that constitutes the control device 3C is the heating element 200 (eg, FET) described above.
- Semiconductor switching elements 206U, 206V, 206W, 207U, 207V, and 207W form a three-phase bridge circuit. This semiconductor switching element switches the motor current IM according to the magnitude and direction of the assist torque.
- semiconductor switching elements 206U, 206V, and 206W may be referred to as semiconductor switching elements 206.
- Semiconductor switching elements 207U, 207V, and 207W may be referred to as semiconductor switching elements 207 in some cases.
- Semiconductor switching elements 209U, 209V, and 209W constitute a motor relay.
- This motor relay is a switch for turning on/off the motor current IM supplied from the bridge circuit to the electric motor 5 .
- Semiconductor switching elements 205a and 205b constitute a power relay. This power relay functions as a switch for turning on/off the battery current IB supplied from the battery 9 to the bridge circuit.
- semiconductor switching elements 209U, 209V, and 209W may be referred to as semiconductor switching elements 209 in the following description.
- the coil 14a prevents electromagnetic noise generated during the switching operation of the semiconductor switching elements 206 and 207 from leaking to the outside and becoming radio noise.
- the rotation sensor 6 is a rotational position sensor that detects the rotational position of the rotor 18 .
- the microcomputer 10 calculates the assist torque based on the steering torque signal output from the torque sensor 8.
- the microcomputer 10 performs feedback control based on the motor current IM flowing through the electric motor 5 and the rotational position of the rotor of the electric motor 5 detected by the rotation sensor 6 .
- the microcomputer 10 calculates a current corresponding to the assist torque.
- the microcomputer 10 has functions such as an AD converter and a PWM timer circuit. Furthermore, the microcomputer 10 has a well-known self-diagnostic function, and constantly self-diagnoses whether the system of the electric power steering device 3 is operating normally. When the microcomputer 10 detects an abnormality, the microcomputer 10 cuts off the supply of the motor current IM.
- the steering torque output from the torque sensor 8 is input to the microcomputer 10 . Furthermore, information on the rotational position of the rotor of the electric motor 5 is input to the microcomputer 10 from the rotation sensor 6 .
- the microcomputer 10 also receives a traveling speed signal, which is one of vehicle signals, from a vehicle signal connector 17 . Motor current IM is fed back to microcomputer 10 through shunt resistor 208 . Based on these information and signals, the microcomputer 10 generates a power steering rotation direction command and a current control amount corresponding to an assist torque.
- a drive signal is input to the drive circuit 11 .
- the drive circuit 11 outputs drive signals for controlling the operations of the semiconductor switching elements 206 and 207 based on commands output from the microcomputer 10 .
- the drive circuit 11 When a rotation direction command and a current control amount are input to the drive circuit 11, the drive circuit 11 generates a PWM drive signal.
- the drive circuit 11 applies PWM drive signals to the semiconductor switching elements 206 and 207 .
- electric current supplied from the battery 9 flows to the electric motor 5 through the power connector 16, the coil 14a, and the semiconductor switching elements 205a and 205b.
- a required amount of assist torque is output in a required direction.
- the motor current IM detected through the shunt resistor 208 and current detection means is fed back to the microcomputer 10 .
- control is performed so that the motor current IM sent from the microcomputer 10 to the drive circuit 11 matches the motor current IM.
- the motor current IM includes a ripple component due to the switching operation of the semiconductor switching elements 206 and 207 during PWM driving, but the motor current IM is controlled so as to be smoothed by the large-capacity capacitors 15a and 15b.
- substrate 100 carries shunt resistor 208, microcomputer 10, and drive circuit 11. FIG.
- a power section 3P shown in FIG. 6 is mounted on the substrate 100.
- FIG. Specifically, as shown in FIGS. 8A and 8B, on the substrate 100, the coil 14a (EMI noise filter) shown in FIG. A portion composed of a shunt resistor 208, capacitors 15a and 15b, and a semiconductor switching element 209 is mounted.
- EMI noise filter EMI noise filter
- the substrate 100 having such a configuration has a structure for dissipating heat from the metal plates 400 (400A, 400B, 400C) to the heat sink 600 via the heat conductive insulator 500, as described in the first and second embodiments. 8A and 8B, illustration of the thermally conductive insulator 500 and the heat sink 600 is omitted.
- the semiconductor switching element (FET, heating element 200) employed in the structure shown in FIGS. 8A and 8B has a top heat spreader 201.
- FIG. The top electrode of the semiconductor switching element is the drain electrode.
- no member is arranged in a region 100R located in the upper right portion of the first surface 100F of the substrate 100.
- no members are arranged on the second surface 100S of the substrate 100 either. That is, the region 100R and the second surface 100S are empty spaces.
- the power supply circuit 13 the microcomputer 10, the drive circuit 11, the input circuit 12, the rotation sensor 6, and various interfaces associated with the control circuit can be mounted.
- the electric power steering device 3 includes a plurality of semiconductor switching elements that are heat generating elements. Heat can be radiated to the outside of the electric power steering device 3 .
- FIG. 9 is an exploded view of a motor and a controller that constitute a redundant electric power steering device 3A assuming a complete duplex system.
- FIG. 9 shows an example of a redundant electric power steering system.
- the same members in the configuration shown in FIGS. 1 to 8B are denoted by the same reference numerals, and the description thereof will be omitted or simplified.
- the redundant electric power steering device 3A has a circuit configuration including two circuit block diagrams shown in FIG. That is, the redundant electric power steering device 3A has two circuits.
- the redundant electric power steering system 3A almost all the parts constituting the electric power steering system 3 according to the third embodiment are required in two systems. Therefore, the mounting area in which components are mounted on the substrate 100 is expanded.
- the redundant electric power steering device 3A the heat generated from the semiconductor switching elements passes through the metal plate 400 (400A, 400B, 400C), the thermally conductive insulator 500, and the heat sink 600 to the redundant electric power steering device 3A. Heat can be dissipated to the outside of 3A. As a result, an increase in the area or volume of the substrate 100 due to an increase in the number of parts can be minimized. Further, the redundant electric power steering device 3A can be downsized without sacrificing heat radiation performance, and a low-cost redundant electric power steering device 3A can be achieved.
- Power supply relays (semiconductor switching elements) 206, 206U , 206V, 206W...semiconductor switching elements 207, 207U, 207V, 207W...semiconductor switching elements 208, 208U, 208V, 208W...shunt resistors 209, 209U, 209V, 209W...semiconductor switching elements 300...heat conduction member 304...right shunt Resistor 400...metal plate 400a...wiring 400A...first metal plate 400b...wiring 400B...second metal plate 400C...third metal plate 400c, 400d...wiring 400F...first metal surface 400R...bottom 400S...second metal surface 400I...
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Abstract
Description
実施の形態を説明する前に、熱設計の基本的な事項について述べる。
半導体プロセスの進化に伴って、パワーMOS-FETに代表されるような発熱素子の小型化が進んでいる。現在の発熱素子が備える性能と同等以上の性能を有する発熱素子が小型化すると、発熱素子を備えた部品を使用した電子装置の実装密度が向上し、電子装置の小型化が図れる。
一例として、ヒートスプレッダを上面に備えるFET(発熱素子、発熱部品)と、FETが実装された基板と、ヒートシンクと、FETとヒートシンクとの間に設けられた熱伝導絶縁部材とを備えた構造において、FETがヒートシンクに放熱する場合を考察する。
RΘ=t/(S×λ) [℃/W]
ここで、“t”は、熱伝導絶縁体の厚さ[m]を示す。
“S”は、熱伝導絶縁体の面積(ヒートスプレッダの面積)[m2]を示す。
“λ”は、熱伝導絶縁体の熱伝導率[W/m・K]を示す。
なお、ここでは、ヒートスプレッダの熱抵抗は無視している。
ヒートスプレッダは、通常、銅で形成されている。銅の熱伝導率は、およそ400W/m・Kである。熱伝導絶縁体の熱伝導率は、通常、数~10W/m・K程度である。このため、熱伝導絶縁体の熱伝導率は、銅の熱伝導率とは桁が異なる。この理由から、ヒートスプレッダの熱抵抗を無視しても、熱抵抗RΘへの影響は無視できる。
(手法1)熱伝導絶縁体の厚さtを小さくする。
(手法2)熱伝導絶縁体の面積Sを大きくする。
(手法3)熱伝導絶縁体の熱伝導率λを大きくする。
次に、上記3つの手法の各々について検討する。
FETのヒートスプレッダは、通常、FETの内部電極と電気的に導通している。ヒートスプレッダは、ヒートシンクとは電気的に絶縁されている必要がある。従って、電気絶縁性を得るために、一般的に、熱伝導絶縁グリス、接着剤、シート等が使用される。電気絶縁性を確保しながら熱伝導絶縁体の厚さtを小さくするには、放熱系(放熱部材、放熱構造、放熱経路)を形成する構造物の加工及び組み立てにおいて、高い精度が要求される。さらに、熱伝導絶縁体の厚さtを小さくするには、限界があるだけでなく、高い加工精度が求められる。
熱伝導絶縁体の面積Sは、FETのヒートスプレッダの面積で決まる。このため、面積Sを大きくすることは不可能である。さらに、FETパッケージを大きくしてヒートスプレッダの面積も大きくすることは、FETパッケージの小型化に逆行することになり、非現実的である。
熱伝導絶縁グリス、接着剤およびシートの熱伝導率は、通常、数~10W/m・K程度である。この数値よりも高い熱伝導率を有する熱伝導絶縁体は存在するが、そのような熱伝導絶縁体は非常に高価であり、量産設計には向かない。
次に、実施の形態1に係る電子装置1について、図1を参照しながら説明する。
後述する実施の形態1~4及び変形例の説明では、電子装置1の厚さ方向(換言すると、基板100の厚さ方向)をZ方向と定義し、Z方向に直交する方向をX方向及びY方向と定義する。
また、後述する各部材の寸法に関し、「厚さ」とは、Z方向における距離を意味し、「面積」とは、X方向及びY方向に平行な面の面積を意味する。
また、「接触面積」とは、2つの部材が接触する面積を意味する。
基板100は、例えば、公知のプリント基板である。基板100上には、回路パターン100Pが形成されている。図1に示す例では、基板100の一方の面100F(第1面、上面)上に、回路パターン100Pが形成されている。基板100の一方の面100Fには、上述した複数の部材200、300、400、500、600が順に積層された構造が示されている。以下の説明では、一方の面100Fを第1面100Fと称する。
発熱素子200は、基板100上に配置されている。発熱素子200は、基板100の第1面100Fに実装されている。発熱素子200は、例えば、パワーMOS-FETである。また、発熱素子200は、パワー素子と称することができる。パワーMOS-FETには、FETチップが内蔵されている。以下の説明においては、発熱素子をパワーMOS-FET、或いは、FETと称する場合がある。発熱素子200は、ドレイン電極、ソース電極、及びゲート電極(制御端子)を有する。
換言すると、上面ヒートスプレッダ201は、基板100の第1面100Fとは反対側に位置する。
図1に示す例では、発熱素子200が下面ヒートスプレッダ202を備える構造が示されているが、本実施の形態では、上面ヒートスプレッダ201から金属板400に向かう放熱について説明する。
熱伝導部材300は、上面ヒートスプレッダ201上に配置されている。熱伝導部材300は、上面ヒートスプレッダ201と金属板400との間に設けられている。熱伝導部材300は、上面ヒートスプレッダ201と金属板400とを熱的及び機械的に結合する。つまり、熱伝導部材300は、上面ヒートスプレッダ201と金属板400とを接合する熱結合部材である。熱伝導部材300の材料としては、熱伝導率が高い材料が採用され、例えば、半田、銀ペースト等の金属系材料が用いられる。また、熱伝導部材300の材料としては、電気伝導性を有する材料が用いられてもよい。
例えば、熱伝導部材300として半田を用いる場合、半田の熱伝導率は、約50W/m・Kである。さらに、半田の厚さは自由に設定することが可能であり、半田の厚さを薄くすることができる。このため、半田の熱抵抗を小さくすることができる。
金属板400は、上面ヒートスプレッダ201上に配置されている。
金属板400を構成する材料としては、熱伝導性に優れた金属材料が用いられ、例えば、銅等が採用される。金属板400として銅を用いる場合、銅の熱伝導率は、約400W/m・Kである。金属板400の厚さは、例えば、0.5mm~1.0mmの範囲内であることが好ましい。金属板400の厚さは、この厚さの範囲に限定されない。
金属板400は、第1金属面400Fと、第1金属面400Fとは反対の面である第2金属面400Sとを有する。第1金属面400Fは、熱伝導絶縁体500と接触している。第2金属面400Sは、熱伝導部材300と接触している。
金属板400の形状は平板であるため、第1金属面400F及び第2金属面400Sの各々は、平坦面である。
金属板400の厚さは、金属板400の熱伝導性を鑑みて設定される。
熱伝導絶縁体500は、金属板400上に配置されている。熱伝導絶縁体500は、金属板400とヒートシンク600との間に充填されている。
熱伝導絶縁体500は、金属板400からヒートシンク600への熱を伝導させる部材である。さらに、熱伝導絶縁体500は、金属板400とヒートシンク600とを電気的に絶縁する部材である。熱伝導絶縁体としては、公知の材料が用いられ、例えば、熱伝導グリス又は熱伝導接着剤が用いられる。熱伝導絶縁体500の熱伝導率は、一般的に、数~10W/m・K程度である。
ヒートシンク600は、熱伝導絶縁体500上に配置されている。ヒートシンク600の構造としては、例えば、複数のフィンを備えた公知の構造が採用される。ヒートシンク600を構成する材料としては、熱伝導性に優れた金属材料が用いられ、例えば、銅やアルミニウム等が採用される。
次に、電子装置1における作用効果を説明する。
基板100から発熱素子200への制御信号の供給に伴って、発熱素子200は、発熱する。発熱素子200から発生する熱は、熱伝導部材300を通じて、上面ヒートスプレッダ201から金属板400に伝わる。金属板400は、高い熱伝導率を有するため、金属板400に伝わった熱は、まず、X方向及びY方向に拡散する。
図2に示すように、金属板400は、凸部401を有する。
凸部401は、第2金属面400Sから発熱素子200に向けて突出した部位である。
凸部401の高さ、つまり、Z方向における第2金属面400Sから凸部401の端面400Tまでの距離は、適宜、調整可能である。第2金属面400Sと端面400Tとの間には、傾斜面400Iが形成されている。
この構成によれば、上述した実施の形態1に係る電子装置1と同様又は類似の効果が得られるだけでなく、例えば、基板100と金属板400の第2金属面400Sとの距離を大きくする場合に有効である。
具体的に、ヒートシンク600と金属板400との間には、スペーサ501と、熱伝導絶縁体500とが配置されている。スペーサ501の材料としては、公知の絶縁材料が用いられる。スペーサ501は、ヒートシンク600と金属板400との間に形成される隙間を維持するために必要な強度を有する。
図3に示すように、金属板400は、凸部401と、凹部402と、傾斜面400Iとを有する。
凸部401は、図2に示す構造と同様に、第2金属面400Sから発熱素子200に向けて突出した部位である。傾斜面400Iは、図2に示す構造と同様に、第2金属面400Sと端面400Tとの間に形成されている。
凹部402の形成方法としては、公知のプレス加工法等を用いて、図1に示す平板の金属板400に凹部402を形成する方法が挙げられる。
さらに、凹部402に熱伝導絶縁体500を充填することができるため、金属板400とヒートシンク600との接続信頼性を向上させることができる。
上述した実施の形態1では、電子装置1が1つの発熱素子200を備える場合について説明した。実施の形態2では、図4A~図4Cを参照し、電子装置が複数の発熱素子を備える場合について説明する。
図4A~図4Cにおいて、図1~図3に示す電子装置1における同一部材には同一符号を付して、その説明は省略または簡略化する。
8つの発熱素子200の各々の上面ヒートスプレッダ201は、ドレイン電極として機能する。
第1素子グループ200G1を構成する4つの発熱素子200(複数の第1発熱素子、複数の発熱素子)は、熱伝導部材300を介して、4つの第1金属板400Aに接続されている。4つの発熱素子200各々は、基板100とは反対側に位置する上面ヒートスプレッダ201(第1上面放熱部、上面放熱部)を有する。4つの第1金属板400Aは、熱伝導部材300上に配置され、4つの発熱素子200の配列方向(X方向)に沿って配置されている。4つの第1金属板400Aは、互いに分離している。
第1素子グループ200G1において、上面ヒートスプレッダ201は、熱伝導部材300を介して、4つの第1金属板400Aの各々に接続されている。つまり、1つの発熱素子200の上面ヒートスプレッダ201は、熱伝導部材300を介して、1つの第1金属板400Aと電気的に接続されている。4つの第1金属板400Aは、互いに電気的に独立しているため、4つの発熱素子200の上面ヒートスプレッダ201は、互いに導通していない。したがって、4つの発熱素子200の4つの上面ヒートスプレッダ201の電位は、互いに異なる。つまり、第1素子グループ200G1においては、上面ヒートスプレッダ201(ドレイン電極)は、電位的に互いに独立している。
第2素子グループ200G2を構成する4つの発熱素子200(複数の第2発熱素子、複数の発熱素子)は、熱伝導部材300を介して、1つの第2金属板400Bに接続されている。4つの発熱素子200各々は、基板100とは反対側に位置する上面ヒートスプレッダ201(第2上面放熱部、上面放熱部)を有する。第2金属板400Bは、熱伝導部材300上に配置され、4つ発熱素子200の配列方向(X方向)に沿って延在している。第2金属板400Bは、4つ発熱素子200を互いに導通させている。第2金属板400Bは、第1金属板400Aから電気的に独立している。
図4Aに示す第2金属板400Bは、例えば、後述する図6に示す回路ブロック図に示す符号400aに相当する配線である。
シャント抵抗器204は、電極204Eを有する。シャント抵抗器204の電極204Eは、半田付けにより基板100の回路パターン100Pに接合されている。電極204Eが回路パターン100Pに接合された位置204Rと、熱伝導絶縁体500との間には、第3金属板400Cが設けられている。
図4Aに示すように、3つのシャント抵抗器204に電気的に接続されている第3金属板400Cは、互いに独立している。つまり、互いに隣り合う2つのシャント抵抗器204の間において、2つの第3金属板400Cは、電気的に接続されていない。
換言すると、X方向に沿って配置された複数の第1金属板400Aの列の数は、2つ以上であってもよい(複数の金属板400)。また、X方向に延在する第2金属板400Bの列の数も、2つ以上であってもよい(複数の金属板400)。金属板の列の数が3つ以上である場合、選択される2つの金属板の列が、複数の第1金属板400Aの列、及び、第2金属板400Bの列に対応する。
具体的に、位置204Rに配置された第3金属板400Cの部分は、断面視においてS字形状を形成するように折り曲げられている。折り曲げられた第3金属板400Cは、位置204Rにおいて回路パターン100Pに接合されている。これにより、シャント抵抗器204や回路パターン100Pから発生した熱は、電極204Eの位置204R、第3金属板400C、及び熱伝導絶縁体500を介して、ヒートシンク600から放熱される。
なお、図5A及び図5Bでは、基板100及び発熱素子は省略されている。
絶縁部材800は、金属板400A、400B、400Cを互いに絶縁し、固定している。金属板400A、400B、400C、及び絶縁部材800によって、1つの部品が構成されている。図5Bに示す寸法Aは、熱伝導絶縁体500の厚さを示している。上述したとおり、この厚さ(寸法A)が薄いほど、熱抵抗を小さくすることができ、放熱性能を向上させることができる。
リブ801を備える絶縁部材800を用いる構造においては、リブ801に対応する位置に、ヒートシンク600に溝600Gが設けられている。
次に、電子装置2における作用効果を説明する。
電子装置2によれば、上述した実施の形態1に係る電子装置1と同様又は類似の作用効果を得ることができる。さらに、電子装置2が複数の発熱素子200を備えた場合でも、第1金属板400A、第2金属板400B、及び第3金属板400Cを一体化することができる。さらに、複数の金属板400A、400B、400Cを絶縁部材800で固定することで、熱伝導絶縁体500の厚さを絶縁部材800の厚さで決まるように薄く設定することができる。これにより、高放熱構造を達成することができる。基板100の第2面100S上に他の制御回路等の部品を配置することで、小型かつ低価格な電子装置2を実現することができる。
次に、図4D~図4Fを参照し、上述した実施の形態2の変形例について説明する。実施の形態2の変形例は、第3金属板300Cの接続構造の点で、実施の形態2と相違している。図4D~図4Fにおいて、図1~図3に示す電子装置1及び図4A~図4Cに示す電子装置2における同一部材には同一符号を付して、その説明は省略または簡略化する。
発熱素子250は、図1に示す発熱素子200と同様の構造を有しており、下面ヒートスプレッダ202を備えている。下面ヒートスプレッダ202は、発熱素子250のドレイン電極又はソース電極である。発熱素子250は、X方向において、3つのシャント抵抗器204のうちの最も右側に位置する右側シャント抵抗器304の隣に配置されている。
第3金属板400Cは、回路パターン100Pを介して、右側シャント抵抗器304の一方の電極304Eと発熱素子250の下面ヒートスプレッダ202とを接続している。図4E及び図4Fに示すように、第3金属板400Cは、熱伝導絶縁体500を介して、ヒートシンク600に接続されている。第3金属板400Cは、上述した金属板400と同様の材料で形成されている。
次に、電極304Eと第3金属板400Cとの接続構造、及び、下面ヒートスプレッダ202と第3金属板400Cとの接続構造について、以下に具体的に説明する。
さらに、右側シャント抵抗器304及び発熱素子250の両部品は、発熱部品であり、これらの部品から発生した熱は、第3金属板400C及び熱伝導絶縁体500を介して、ヒートシンク600に放熱される。また、回路パターン100Pから発生する熱も第3金属板400C及び熱伝導絶縁体500を介して、ヒートシンク600に放熱される。
実施の形態1及び2では、電子装置1が1つの発熱素子200を備える場合、及び、電子装置2、2Aが複数の発熱素子200を備える場合について説明した。実施の形態3では、複数の発熱素子を備えた電子装置が電動パワーステアリング装置に適用された場合について説明する。
図6~図8Bにおいて、図1~図5Bに示す構成における同一部材には同一符号を付して、その説明は省略または簡略化する。
図7に示すように、電動パワーステアリング装置3は、電動パワーステアリング装置3を構成するモータ及びコントローラの展開図である。図8A及び図8Bは、電動パワーステアリング装置3を構成する基板部を示す斜視図である。
さらに、制御装置3Cは、回転センサ6と、マイクロコンピュータ10と、駆動回路11と、基板100とを備えている。
コンデンサ15a、15bは、電動モータ5に流れるモータ電流IMのリップル成分を吸収するための大容量のコンデンサである。コンデンサ15a、15bは、例えば、リップルコンデンサである。
シャント抵抗器208U、208V、208Wは、モータ電流IMを検出する。
なお、以下の説明では、シャント抵抗器208U、208V、208Wをシャント抵抗器208と称する場合がある。
制御装置3Cを構成する半導体スイッチング素子は、上述した発熱素子200(例えば、FET)である。
半導体スイッチング素子206U、206V、206W、207U、207V、207Wは、3相のブリッジ回路を構成する。この半導体スイッチング素子は、補助トルクの大きさ及び方向に応じてモータ電流IMを切り替える。
半導体スイッチング素子205a、205bは、電源リレーを構成する。この電源リレーは、バッテリ9からブリッジ回路に供給されるバッテリ電流IBを通電・遮断するスイッチとして機能する。
なお、以下の説明では、半導体スイッチング素子209U、209V、209Wを半導体スイッチング素子209と称する場合がある。
コイル14aは、半導体スイッチング素子206、207のスイッチング動作時に発生する電磁ノイズが外部へ流出してラジオノイズになることを防止する。
回転センサ6は、回転子18の回転位置を検出する回転位置センサである。
マイクロコンピュータ10は、トルクセンサ8から出力される操舵トルク信号に基づいて、補助トルクを演算する。マイクロコンピュータ10は、電動モータ5に流れるモータ電流IM及び回転センサ6で検出された電動モータ5の回転子の回転位置に基づいてフィードバック制御を行う。マイクロコンピュータ10は、補助トルクに相当する電流を演算する。
駆動回路11は、マイクロコンピュータ10から出力された指令に基づき、半導体スイッチング素子206、207の作動を制御する駆動信号を出力する。
実施の形態1、2で述べたように、基板100上には複数の発熱素子200が実装されている。さらに、基板100は、シャント抵抗器208、マイクロコンピュータ10、及び駆動回路11を搭載する。
具体的に、図8A及び図8Bに示すように、基板100上には、図6に示すコイル14a(EMIノイズフィルタ)、電源リレー205a、205b、インバータ部の半導体スイッチング素子206、207、電流検出用のシャント抵抗器208、コンデンサ15a、15b、及び半導体スイッチング素子209で構成されている部分が実装されている。
次に、電動パワーステアリング装置3における作用効果を説明する。
電動パワーステアリング装置3によれば、上述した電子装置1、2、2Aと同様又は類似の作用効果を得ることができる。電動パワーステアリング装置3は、発熱素子である複数の半導体スイッチング素子を備えるが、金属板400(400A、400B、400C)、熱伝導絶縁体500、及びヒートシンク600を介して、半導体スイッチング素子から発生する熱を電動パワーステアリング装置3の外部に放熱することができる。
図9は、完全2重系を想定した冗長電動パワーステアリング装置3Aを構成するモータ及びコントローラの展開図である。
これに対し、冗長電動パワーステアリング装置3Aにおいて、半導体スイッチング素子から発生する熱は、金属板400(400A、400B、400C)、熱伝導絶縁体500、及びヒートシンク600を介して、冗長電動パワーステアリング装置3Aの外部に放熱することができる。これによって、部品点数の増加に伴う基板100の面積あるいは体積の増大を最小限に止めることができる。さらに、放熱性能を犠牲にせず、冗長電動パワーステアリング装置3Aを小型化することができ、かつ、低価格な冗長電動パワーステアリング装置3Aを達成できる。
Claims (14)
- 回路パターンを有する基板と、
前記基板上に配置され、前記基板とは反対側に位置する上面放熱部を有する発熱素子と、
前記上面放熱部上に配置された熱伝導部材と、
前記熱伝導部材上に配置された金属板と、
前記金属板上に配置された熱伝導絶縁体と、
前記熱伝導絶縁体上に配置されたヒートシンクと、
を備える電子装置。 - 前記熱伝導部材の熱伝導率は、前記熱伝導絶縁体の熱伝導率より大きい、
請求項1に記載の電子装置。 - 前記金属板と前記熱伝導絶縁体が接する面積は、前記発熱素子と前記熱伝導部材が接する面積より大きい、
請求項1に記載の電子装置。 - 前記熱伝導部材は、前記上面放熱部と前記金属板との間に設けられており、
前記熱伝導部材の材料は、半田である、
請求項1に記載の電子装置。 - 前記熱伝導絶縁体は、前記金属板と前記ヒートシンクとの間に設けられており、
前記熱伝導絶縁体の材料は、熱伝導グリス又は熱伝導接着剤である、
請求項1に記載の電子装置。 - 前記金属板と前記ヒートシンクとの間の隙間を決定するスペーサを備え、
前記スペーサで決定された前記金属板と前記ヒートシンクとの間の隙間に、前記熱伝導絶縁体が充填されている、
請求項1に記載の電子装置。 - 各々が、前記基板とは反対側に位置する上面放熱部を有し、かつ、前記発熱素子に対応する、複数の発熱素子と、
前記熱伝導部材上に配置され、前記複数の発熱素子の配列方向に沿って配置され、互いに分離した複数の第1金属板と、
を備え、
前記上面放熱部は、前記熱伝導部材を介して、前記複数の第1金属板の各々に接続されている、
請求項1に記載の電子装置。 - 各々が、前記基板とは反対側に位置する上面放熱部を有し、かつ、前記発熱素子に対応する、複数の発熱素子と、
前記熱伝導部材上に配置され、前記複数の発熱素子の配列方向に沿って延在し、前記複数の発熱素子を互いに導通させる第2金属板と、
を備え、
前記上面放熱部は、前記熱伝導部材を介して、前記第2金属板に接続されている、
請求項1に記載の電子装置。 - 半田付けにより前記回路パターンに接合されている電極を有する発熱部品と、
前記電極が前記回路パターンにより接合された位置と、前記熱伝導絶縁体との間に設けられた第3金属板と、
を備える、
請求項1から請求項8のいずれか一項に記載の電子装置。 - 前記第3金属板は、半田付けにより前記回路パターンに接合されている、
請求項9に記載の電子装置。 - 前記熱伝導部材上に配置された第1金属板と、
前記熱伝導部材上に配置され、かつ、前記第1金属板から電気的に独立した第2金属板と、
前記第1金属板、前記第2金属板、及び前記第3金属板を絶縁する絶縁部材と、
を有し、
前記第1金属板、前記第2金属板、前記第3金属板、及び前記絶縁部材によって、1つの部品が構成されている、
請求項9に記載の電子装置。 - 前記絶縁部材の厚さによって、前記熱伝導絶縁体の厚さが決定されている、
請求項11に記載の電子装置。 - 前記絶縁部材は、前記ヒートシンクに面する端面に設けられたリブを備え、
前記ヒートシンクは、前記リブに対応する位置に設けられた溝を備え、
前記溝に前記リブが挿入されている、
請求項11に記載の電子装置。 - 回路パターンを有する基板と、
前記基板上に配置され、前記基板とは反対側に位置する上面放熱部を有する発熱素子と、
前記上面放熱部上に配置された熱伝導部材と、
前記熱伝導部材上に配置された金属板と、
前記金属板上に配置された熱伝導絶縁体と、
前記熱伝導絶縁体上に配置されたヒートシンクと、
を備える電動パワーステアリング装置。
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JP2008130879A (ja) * | 2006-11-22 | 2008-06-05 | Denso Corp | 電子装置 |
JP2008277330A (ja) * | 2007-04-25 | 2008-11-13 | Mitsubishi Electric Corp | 放熱装置 |
JP6160576B2 (ja) | 2014-07-31 | 2017-07-12 | 株式会社デンソー | 駆動装置、および、これを用いた電動パワーステアリング装置 |
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CN117693811A (zh) | 2024-03-12 |
EP4379792A1 (en) | 2024-06-05 |
JPWO2023007546A1 (ja) | 2023-02-02 |
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