JP2018129351A - Fitting structure of heating member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent thermal conductivity between a heating member and a heat radiating member from being deteriorated over time.SOLUTION: A semiconductor device 2 that is a heating member is fixed to a heat sink 3 that is a heat radiation member via a heat conduction sheet 4. The heat conduction sheet 4 is a heat conductive and elastic compressible member. A cylindrical metal collar 13 is disposed on the inner peripheral side of a sheet through hole 12 of the heat conduction sheet 4. Into the collar 13, a screw 5 is inserted. The collar 13 is set to be thinner than the heat conduction sheet 4. Thus, excessive tightening of the heat conduction sheet 4 by the collar 13 is suppressed, and occurrence of creep phenomenon in the heat conduction sheet 4 can be suppressed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a structure for attaching a heat generating member to a heat radiating member.

  A heat generating member such as a semiconductor radiates heat by being attached to a heat radiating member such as a heat sink. Here, in order for the heat dissipating member to exhibit a sufficient cooling capacity, it is necessary to closely contact the heat generating member and the heat dissipating member. However, the mounting surface of the heat generating member to the heat radiating member and the mounting surface of the heat radiating member to which the heat generating member is mounted may not be flat or may have irregularities due to surface roughness.

  For example, in Patent Document 1, a resin sheet having thermal conductivity is interposed between a wiring board on which an LED (light emitting diode) as a heating element is mounted and a heat sink as a heat radiating member, and the wiring board and the resin sheet are screwed. And the heat sink are tightened and fixed together. Accordingly, the resin sheet is compressed between the wiring board and the heat sink by tightening with a screw, and deforms following the uneven shape of the mounting surface of the wiring board to the heat sink or the mounting surface of the heat sink to which the wiring board is attached. .

  That is, in Patent Document 1, the resin sheet is compressed and deformed, and the space between the wiring board and the heat sink is filled with the resin sheet without a gap, so that the wiring board and the heat sink are substantially closely contacted via the resin sheet. I am letting.

JP 2012-251089 A

  However, if the resin sheet continues to be compressed excessively for a long time, there is a possibility that a creep phenomenon occurs in which the resin sheet is gradually plastically deformed and loses its elastic force. Therefore, in the configuration as in Patent Document 1, when the resin sheet loses elastic force due to the creep phenomenon, a gap is easily generated between the resin sheet and the wiring board or between the resin sheet and the heat sink. There is a possibility that the thermal conductivity between the substrate and the heat sink may deteriorate.

  The heat generating member mounting structure of the present invention comprises a heat generating heat generating member, a heat radiating member to which the heat generating member is mounted, a heat conductive sheet sandwiched between the heat generating member and the heat radiating member, and the heat generating member as the heat radiating member. And a metal collar into which the screw member is inserted. The collar is set to be thinner than the thickness of the heat conductive sheet, and the heat penetrating through the screw member. The conductive sheet is arranged on the inner peripheral side of the through hole of the conductive sheet.

  The collar may have a truncated cone shape, and may be set so that the outer diameter of the bottom surface of the collar having a relatively large diameter is the same as the diameter of the through hole.

  The dimensional tolerance of the outer diameter of the bottom surface and the diameter of the through hole may be set so that the outer diameter size of the bottom surface of the collar is at least equal to or larger than the diameter of the through hole.

  According to the present invention, excessive tightening of the heat conductive sheet is suppressed by the collar, and a creep phenomenon can be suppressed from occurring in the heat conductive sheet. Therefore, it is suppressed that a gap is generated between the heat conductive sheet and the heat generating member or between the heat conductive sheet and the heat radiating member due to the creep phenomenon. That is, it can suppress that the heat conductivity between a heat generating member and a heat radiating member deteriorates with time.

The top view of the power converter device with which 1st Example of this invention was applied. Sectional drawing along the AA line of FIG. Explanatory drawing which expanded and showed typically the principal part of the power converter device with which 1st Example of this invention was applied. Sectional drawing of a comparative example. Explanatory drawing which expanded and showed the principal part of the comparative example typically. Sectional drawing of the power converter device with which 2nd Example of this invention was applied. Explanatory drawing which expanded and showed typically the principal part of the power converter device with which 2nd Example of this invention was applied.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  A mounting structure for a heat generating member (a semiconductor device 2 described later) in the first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a plan view of a power converter 1 to which a first embodiment of the present invention is applied. FIG. 2 is a cross-sectional view taken along line AA in FIG. FIG. 3 is an explanatory view schematically showing an enlarged main part of the power conversion device 1 to which the first embodiment of the present invention is applied.

  In the power conversion apparatus 1, a box-shaped semiconductor device 2 is fixed to a heat sink 3 with a screw 5 as a screw member via a heat conductive sheet 4.

  The power converter 1 is, for example, an inverter that converts DC power into AC power, a converter that converts AC power into DC power, or the like.

  The semiconductor device 2 is a heat generating member having heat generation properties, and is, for example, a semiconductor switching element such as an IGBT element (insulated gate bipolar transistor) or an FET (electrolytic effect transistor).

  As shown in FIGS. 1 to 3, the semiconductor device 2 has a screw insertion portion 7 in which a screw hole 6 into which the screw 5 is inserted is formed.

  As shown in FIGS. 2 and 3, the semiconductor device 2 has a bottom surface 8 facing the heat sink 3 as a mounting surface (heat sink mounting surface) to the heat sink 3.

  The heat sink 3 is a heat radiating member having a plurality of heat radiating fins 9 and is made of, for example, a metal material such as copper or aluminum.

  As shown in FIGS. 2 and 3, the heat sink 3 has a semiconductor device mounting surface on which the upper surface 10 facing the bottom surface 8 of the semiconductor device 2 is attached. As shown in FIG. 2, the heat dissipating fins 9 are formed to protrude on the opposite side of the upper surface 10. The heat sink 3 is formed with a screw fixing hole 11 into which the screw 5 is screwed. On the inner peripheral surface of the screw fixing hole 11, a female screw that is screwed with the male screw portion of the screw 5 is formed.

  The heat conductive sheet 4 is, for example, a sheet-like or thin plate-like member made of a compressible resin material or rubber material having thermal conductivity and elasticity. The heat conductive sheet 4 is set to have a predetermined thickness t1 in a natural state, in other words, an uncompressed initial state. As shown in FIGS. 2 and 3, the heat conductive sheet 4 is sandwiched between the semiconductor device 2 and the heat sink 3. The heat conductive sheet 4 is formed with a sheet through hole 12 having a diameter d1 through which the screw 5 passes. The heat conductive sheet 4 has substantially the same size as the area of the bottom surface 8 of the semiconductor device 2.

  As shown in FIGS. 2 and 3, a cylindrical collar 13 is disposed on the inner peripheral side of the sheet through hole 12 of the heat conductive sheet 4. The collar 13 is inserted with the screw 5 and is made of a metal material such as iron, stainless steel, brass, copper, or aluminum. The collar 13 can be made of a metal other than the above.

  The collar 13 is set to be thinner than the heat conductive sheet 4 and smaller than the sheet through hole 12. The collar 13 is set to have a thickness t2 and an outer diameter d2. That is, the relationship between the collar 13, the heat conductive sheet 4, and the sheet through hole 12 is set so that t1> t2 and d1> d2.

  4 and 5 show a comparative example in which the collar 13 is omitted in the mounting structure of the heat generating member (semiconductor device 2) in the first embodiment described above. 4 is a cross-sectional view corresponding to a position along the line AA in FIG. FIG. 5 is an explanatory diagram schematically showing an enlarged main part of FIG.

  For example, in the configuration as in the comparative example shown in FIGS. 4 and 5, when an excessive compressive force acts on the heat conductive sheet 4 for a long time by tightening the screws 5, the heat conductive sheet 4 is gradually plastically deformed and elastic force is applied. There is a risk that a creep phenomenon will occur.

  When the heat conductive sheet 4 loses its elastic force, a gap is likely to be generated between the semiconductor device 2 and the heat sink 3 as shown in FIG. Specifically, a gap is likely to occur between the bottom surface 8 of the semiconductor device 2 and the heat conductive sheet 4 or between the heat conductive sheet 4 and the top surface 10 of the heat sink 3. In the example of FIG. 4, a gap is generated between the bottom surface 8 of the semiconductor device 2 and the heat conductive sheet 4. If such a gap is formed, the thermal conductivity between the semiconductor device 2 and the heat sink 3 is deteriorated, and the semiconductor device 2 is not sufficiently cooled, which may cause a failure of the semiconductor device due to overheating.

  However, when the semiconductor device 2 is attached to the heat sink 3 with the screw 5 by disposing the collar 13 on the inner peripheral side of the sheet through hole 12 as in the first embodiment described above, the excessive amount of the heat conductive sheet 4 is excessive. Compression is suppressed. That is, when tightened to some extent by the screw 5, the semiconductor device 2 is supported by the heat sink 3 by the collar 13, and the gap between the semiconductor device 2 and the heat sink 3 does not become less than the thickness t2 of the collar 13, as shown in FIG. .

  Therefore, although the heat conductive sheet 4 is compressed according to the thickness of the collar 13, it is not excessively compressed if the thickness t2 of the collar 13 is set appropriately.

  That is, if the ratio between the thickness t2 of the collar 13 and the thickness t1 of the heat conductive sheet 4 is appropriately set, the heat conductive sheet 4 is not compressed excessively, and the heat conductive sheet 4 is moved to the bottom surface of the semiconductor device 2. 8 and the upper surface 10 of the heat sink 3. In other words, by using the collar 13, it is possible to suppress the occurrence of a creep phenomenon in which the heat conduction sheet 4 gradually plastically deforms and loses its elastic force, and between the semiconductor device 2 and the heat sink 3 with the heat conduction sheet 4. It is possible to fill without gaps over a long period of time.

  Accordingly, it is possible to suppress deterioration of heat conduction from the semiconductor device 2 to the heat sink 3 with time.

  In addition, heat can be efficiently radiated from the semiconductor device 2 to the heat sink 3 without depending on the flatness or surface roughness of the bottom surface 8 of the semiconductor device 2 or the upper surface 10 of the heat sink 3.

  If the creep phenomenon can be suppressed, the heat conductive sheet 4 can suppress the aging deterioration which loses elastic force, and can maintain the close contact state with respect to the semiconductor device 2 and the heat sink 3 for a long time.

  In order to prevent creep phenomenon from occurring in the heat conductive sheet 4 and to bring the heat conductive sheet 4 into close contact with the bottom surface 8 of the semiconductor device 2 and the top surface 10 of the heat sink 3, for example, the compressibility of the heat conductive sheet 4 Is preferably in the range of 70% to 90% with 80% as the median.

  In the first embodiment, the ratio of the thickness t1 of the heat conductive sheet 4 to the thickness t2 of the collar 13 is set to 1: 0.8 so that the compressibility of the heat conductive sheet 4 is 80%. ing.

  Next, a second embodiment of the present invention will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the component same as 1st Example mentioned above, and the overlapping description is abbreviate | omitted.

  FIG. 6 is a cross-sectional view of the power converter 21 to which the second embodiment of the present invention corresponding to the position along the line AA in FIG. 1 is applied. FIG. 7 is an explanatory diagram schematically showing an enlarged main part of the power conversion device 21 to which the second embodiment of the present invention is applied.

  The mounting structure of the heat generating member (semiconductor device 2) in the second embodiment has substantially the same configuration as that of the first embodiment described above, but the shape of the collar 22, the outer diameter of the collar 22, and the diameter of the sheet through hole 12 And the dimensional relationship is different.

  As shown in FIGS. 6 and 7, the collar 22 in the second embodiment has a truncated cone shape and is arranged on the inner peripheral side of the sheet through hole 12 of the heat conductive sheet 4.

  The collar 22 is inserted with the screw 5 and is made of a metal material such as iron, stainless steel, brass, copper, or aluminum, for example, like the collar 13 described above. The collar 22 can also be made of a metal other than the above.

  The collar 22 has a lower bottom 23 serving as a bottom surface located on the heat sink 3 side.

  The collar 22 is set so that the outer diameter d3 of the lower bottom 23 is equal to the diameter d1 of the sheet through hole 12. In other words, the collar 22 is set so that the outer diameter d3 of the lower base 23 having a larger diameter than the upper base 24 on the semiconductor device 2 side is the same diameter as the diameter d1 of the sheet through hole 12.

  The collar 22 is set to be thinner than the heat conductive sheet 4. That is, the collar 22 is set to satisfy t1> t3 when the thickness thereof is t3.

  That is, in the second embodiment, the relationship between the collar 22, the heat conductive sheet 4, and the sheet through hole 12 is set so that t1> t3 and d1 = d3.

  Also in the second embodiment, the ratio of the thickness t1 of the heat conductive sheet 4 to the thickness t3 of the collar 22 is 1: 0.8 so that the compressibility of the heat conductive sheet 4 is 80%. It is set.

  In this second embodiment, when the heat conductive sheet 4 is sandwiched between the semiconductor device 2 and the heat sink 3 and compressed by tightening the screws 5, the outer peripheral surface of the collar 22 is the sheet as shown in FIG. Close contact with the inner peripheral surface of the through hole 12.

  Also in the second embodiment, the same operational effects as those of the first embodiment described above can be achieved.

  Further, in this second embodiment, the dimensional tolerances of the outer diameter d3 of the lower bottom 23 of the collar 22 and the diameter d1 of the sheet through hole 12 are set so that the dimension of the outer diameter d3 is at least equal to or larger than the dimension of the diameter d1. ing. More specifically, the dimensional tolerance of the diameter d1 of the sheet through hole 12 is, for example, that the upper dimensional tolerance is 0 mm and the lower dimensional tolerance is -0.1 mm. The dimensional tolerance of the outer diameter d3 of the lower base 23 of the collar 22 is, for example, an upper dimensional tolerance of +0.1 mm and a lower dimensional tolerance of 0 mm. In other words, in the collar 22, the maximum allowable dimension of the outer diameter d3 of the lower bottom 23 is larger than the maximum allowable dimension of the diameter d1 of the sheet through hole 12, and the minimum allowable dimension of the outer diameter d3 of the lower bottom 23 is the sheet penetration. It is set to be larger than the minimum allowable dimension of the diameter d1 of the hole 12.

  For this reason, the collar 22 is securely in close contact with the sheet through hole 12 of the heat conductive sheet 4 and is less likely to fall off the sheet through hole 12 due to frictional force.

  Therefore, in the second embodiment, for example, even when the mounting surface of the semiconductor device 2 and the heat sink 3 is along the vertical direction, the color is removed when the semiconductor device 2 is replaced or the like. It can suppress that 22 falls out. In other words, even when the axial direction of the screw 5 is orthogonal to the vertical direction, it is possible to suppress the collar 22 from falling off during removal such as replacement of the semiconductor device 2.

  In each of the above-described embodiments, the ratio of the thickness t1 of the heat conductive sheet 4 to the thicknesses t2 and t3 of the collars 13 and 22 is set to 1: 0.8, but the present invention is limited to this. However, it can be appropriately changed within a range in which the creep phenomenon does not occur in the heat conductive sheet 4.

  Further, the shape of the metal collar is not limited to the cylinder and the truncated cone of the first and second embodiments described above, and may be a square or a truncated pyramid, for example.

  In the first embodiment described above, the outer diameter of the collar 13 can be formed to be equal to the inner diameter of the sheet through hole 12 of the heat conductive sheet 4. In this case, the collar 13 is in close contact with the sheet through hole 12 of the heat conductive sheet 4 and is less likely to fall off the sheet through hole 12 due to frictional force.

  In each of the above-described embodiments, the semiconductor device 2 is fixed to the heat sink 3 with the screws 5, but the semiconductor device 2 may be fixed to the heat sink 3 with bolts. That is, a bolt can be used as the screw member.

DESCRIPTION OF SYMBOLS 1 ... Power converter 2 ... Semiconductor device 3 ... Heat sink 4 ... Heat conductive sheet 5 ... Screw 6 ... Screw hole 7 ... Screw insertion part 8 ... Bottom 9 ... Radiation fin 10 ... Upper surface 11 ... Screw fixing hole 12 ... Sheet through-hole 13 ... Color 21 ... Power converter 22 ... Color 23 ... Lower base 24 ... Upper base

Claims (3)

A heat-generating member having a heat-generating property;
A heat dissipating member to which the heat generating member is attached;
A heat conductive sheet sandwiched between the heat generating member and the heat radiating member;
A screw member for fixing the heat generating member to the heat radiating member;
A metal collar into which the screw member is inserted,
The heating member mounting structure, wherein the collar is set to be thinner than the thickness of the heat conductive sheet, and is arranged on an inner peripheral side of a through hole of the heat conductive sheet through which the screw member passes.   2. The collar according to claim 1, wherein the collar has a truncated cone shape, and an outer diameter of a bottom surface having a relatively large diameter is set to be equal to a diameter of the through hole. The heating member mounting structure described.   The dimensional tolerance of the outer diameter of the bottom surface and the diameter of the through hole is set so that the outer diameter of the bottom surface is at least equal to or larger than the diameter of the through hole. The heating member mounting structure described.

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