JP2016033943A - Power module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resolve heat unevenness between semiconductor elements mounted on a power module and thereby prevent performance deterioration of the power module.SOLUTION: A power module 1 of the invention includes: an insulative substrate 3; a metal wiring layer 5 formed on the substrate 3 and having a predetermined shape; and an insulation layer 7 covering the metal wiring layer 5. Semiconductor elements 11 connected with the metal wiring layer 5 are mounted on the power module 1. Heat radiation parts 23a, 23b, in which a cover formed by the insulation layer 7 does not exist and the metal wiring layer 5 is exposed, are formed around the semiconductor elements 11. Areas of the heat radiation parts 23a, 23b are set according to heat values of the semiconductor elements 11.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power module on which a plurality of semiconductor elements are mounted.

  With recent miniaturization and higher output of power equipment, cooling measures for power modules have become important. Conventionally, as a cooling method of a power module on which a semiconductor element is mounted, a method of dissipating heat of the semiconductor element by installing a radiator on the side opposite to the mounting surface of the semiconductor element is generally used. Here, Patent Document 1 discloses a structure in which a heat spreader is installed on the mounting surface side of a semiconductor element for the purpose of improving heat dissipation. This structure is intended for a power module in which a semiconductor element is bonded to a substrate by wire bonding or ribbon bonding.

  Further, recent power modules have a structure in which a plurality of semiconductor elements are mounted for higher output, and the distance between the semiconductor elements is made as narrow as possible in order to reduce the size.

JP 2011-192689 A

  However, when a plurality of semiconductor elements are mounted and the distance between the semiconductor elements is made as narrow as possible as in the above-described conventional power module, a thermal imbalance between the semiconductor elements is likely to occur, and the power module There is a problem that the performance of the system is degraded.

  Therefore, the present invention has been proposed in view of the above-described circumstances, and an object thereof is to provide a power module capable of eliminating a thermal imbalance between a plurality of semiconductor elements and preventing performance degradation. .

  In order to solve the above-described problem, a power module according to one embodiment of the present invention includes an insulating substrate, a metal wiring layer having a predetermined shape formed over the substrate, and an insulating layer that covers the metal wiring layer. A plurality of semiconductor elements connected to the metal wiring layer are mounted. In the power module, a heat radiating portion that is not covered with an insulating layer and has an exposed metal wiring layer is formed around a plurality of semiconductor elements, and the size of the heat radiating portion is set according to the amount of heat generated by the semiconductor elements. .

  According to the present invention, since the thermal imbalance among a plurality of semiconductor elements mounted on the power module can be eliminated, it is possible to prevent the performance of the power module from being deteriorated.

FIG. 1 is a plan view showing the structure of the power module according to the first embodiment of the present invention. 2 is a cross-sectional view taken along line AA of FIG. 1 showing a cross-sectional structure of the power module according to the first embodiment of the present invention. 3 is a cross-sectional view taken along the line BB in FIG. 1 showing a cross-sectional structure of the power module according to the first embodiment of the present invention. FIG. 4 is a plan view showing a structure of a power module according to a comparative example. FIG. 5 is a cross-sectional view taken along the line CC in FIG. FIG. 6 is a plan view for explaining a current flow of the power module according to the comparative example. FIG. 7 is a plan view for explaining the current flow of the power module according to the comparative example. FIG. 8 is a plan view showing the structure around the semiconductor element of the power module according to the second embodiment of the present invention. 9 is a cross-sectional view taken along the line DD of FIG. 8 showing a cross-sectional structure around the semiconductor element of the power module according to the second embodiment of the present invention. FIG. 10 is a plan view showing a structure around a semiconductor element of a power module according to a comparative example. 11 is a cross-sectional view taken along line EE in FIG. 10 showing a cross-sectional structure around a semiconductor element of a power module according to a comparative example. FIG. 12 is a plan view showing the structure of a power module according to the third embodiment of the present invention. FIG. 13 is a plan view showing the structure of a power module according to the fourth embodiment of the present invention. FIG. 14 is a plan view showing a structure around a semiconductor element of a power module according to the fifth embodiment of the present invention. FIG. 15 is a cross-sectional view taken along line FF in FIG. 14 showing a cross-sectional structure around a semiconductor element of a power module according to the fifth embodiment of the present invention.

  Hereinafter, first to fifth embodiments to which the present invention is applied will be described with reference to the drawings.

[First Embodiment]
[Power module structure]
FIG. 1 is a plan view showing the structure of a power module according to the present embodiment, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB in FIG. As shown in FIGS. 1 to 3, the power module 1 according to this embodiment includes an insulating substrate 3, a metal wiring layer 5 having a predetermined shape formed on the substrate 3, and an insulation covering the metal wiring layer 5. A plurality of semiconductor elements 11 including the layer 7 and connected to the metal wiring layer 5 are mounted.

  The power module 1 has a 2-in-1 structure, and a semiconductor element 11a constituting an upper arm and a semiconductor element 11b constituting a lower arm are mounted on one substrate. However, the structure of the power module 1 does not have to be limited to 2 in 1, and other structures such as 6 in 1 and 1 in 1 are applicable.

  The substrate 3 is made of an insulating material such as an epoxy resin. A heat radiator 15 is installed on the lower surface of the substrate 3 via a heat spreader 13, and the heat spreader 13 is formed of a material having good thermal conductivity such as copper or aluminum. As shown in FIGS. 1 and 3, a part of the heat spreader 13 is exposed to form a connection portion 17 to which wiring from the semiconductor element 11 b is connected. This connection portion 17 is provided for each semiconductor element 11b, and has a structure in which the heat spreader 13 is exposed without being covered with the insulating layer 7, the metal wiring layer 5, and the substrate 3. Thereby, the heat spreader 13 is used as an N wiring and an N terminal and functions as a metal wiring layer.

  The metal wiring layer 5 includes a P wiring 5a and an output wiring 5b, and is formed of a material such as copper or aluminum having a low wiring resistance. The P wiring 5 a is connected to the P terminal 19, and the output wiring 5 b is connected to the output terminal 21. The P terminal 19 and the output terminal 21 may be formed using a material such as aluminum or copper having a low wiring resistance, and may be subjected to a surface treatment such as Ni plating.

  Here, a heat radiating portion 23a is formed around the semiconductor element 11a on the upper arm side without being covered with the insulating layer 7, and the P wiring 5a is exposed, and an insulating layer is formed around the semiconductor element 11b on the lower arm side. A heat radiating portion 23b is formed in which the output wiring 5b is exposed without being covered with the cover 7. The heat radiating portions 23a and 23b are regions having a structure in which the insulating layer 7 is not provided in the vicinity of the semiconductor element 11 and the P wiring 5a and the output wiring 5b in the lower layer are exposed. When the P wiring 5a and the output wiring 5b are exposed, the P wiring 5a and the output wiring 5b are exposed after ensuring insulation from other components. Thus, by exposing the P wiring 5a and the output wiring 5b in the vicinity of the semiconductor element 11, heat generated by the semiconductor element 11 can be radiated from the exposed portion.

  Further, the width of the heat radiation part 23a, that is, the area where the P wiring 5a is exposed is set according to the amount of heat generated by the semiconductor elements 11a mounted in parallel. Specifically, among the plurality of semiconductor elements 11a, the heat radiating part formed around the semiconductor element having the largest heat generation amount is widened, and the heat radiating part formed around the semiconductor element having the small heat generation amount Reduces the exposed area of the P wiring 5a in accordance with the amount of heat generated. In FIG. 1, the semiconductor element 11 a closest to the P terminal 19 generates the largest amount of heat, so that the surrounding heat dissipating part 23 a is the widest, and the heat dissipating part 23 a becomes narrower as the distance from the P terminal 19 increases. ing. In FIG. 1, the heat dissipating part 23 b on the lower arm side is formed only around the semiconductor element 11 b closest to the output terminal 21, but the heat dissipating part 23 b may be formed around all the semiconductor elements 11 b. Good. In this case, the width of the heat radiating portion 23b is set according to the amount of heat generated by the semiconductor element 11b, similarly to the heat radiating portion 23a on the upper arm side described above.

  Further, on the surface of the power module 1, a connection portion 25 for connecting the wiring from the semiconductor element 11a to the output wiring 5b is formed. The connection portion 25 is provided for each semiconductor element 11a, and has a structure in which the output wiring 5b is exposed without being covered with the insulating layer 7.

  The insulating layer 7 is formed of an insulating material such as an epoxy resin and covers the surface of the power module 1.

  The semiconductor element 11 is composed of a plurality of semiconductor elements 11a constituting an upper arm and a plurality of semiconductor elements 11b constituting a lower arm. In the present embodiment, a case of a MOSFET will be described as an example. However, the semiconductor element 11 is not limited to the MOSFET, and may be another semiconductor element such as an IGBT or a thyristor. The semiconductor element 11 is bonded onto the metal wiring layer 5 via a bonding material 27. The bonding material 27 may be a brazing material such as solder, or may be a sinter bonding using silver particles or the like. The wires 29 and 31 connected from the semiconductor element 11 to the connection portions 17 and 25 are made of a material such as aluminum or copper having a low wiring resistance, and may be a ribbon type instead of a wire. The semiconductor element 11 is driven by a gate signal from the gate signal line 33 for the semiconductor element 11a on the upper arm side and by a gate signal from the gate signal line 35 for the semiconductor element 11b on the lower arm side.

[Effects of power module]
When the power module 1 having the structure described above is driven, current flows from the P terminal 19 via the P wiring 5a to the drain electrode of the semiconductor element 11a mounted in parallel on the upper arm side. Thereafter, the current flows from the source electrode of the semiconductor element 11a to the connection portion 25 via the wire 29, and flows to the output terminal 21 through the output wiring 5b.

  When a current flows from the output terminal 21, the current from the output terminal 21 flows to the drain electrode of the semiconductor element 11b mounted in parallel on the lower arm side via the output wiring 5b. Thereafter, the current flows from the source electrode of the semiconductor element 11b to the connection portion 17 via the wire 31, and then flows to the heat spreader 13 that functions as an N wiring and an N terminal.

  At this time, in the power module 1 according to the present embodiment, since the heat radiating portions 23a and 23b exposing the metal wiring layer 5 are formed around the semiconductor element 11, the heat generated in the semiconductor element 11 from the heat radiating portions 23a and 23b. Can be dissipated. Thereby, the heat dissipation of the power module 1 can be improved.

  In addition, since the size of the heat radiating portions 23a and 23b is set according to the amount of heat generated by the semiconductor element 11, the thermal imbalance among the plurality of semiconductor elements 11 mounted in parallel is eliminated and the performance of the power module 1 is degraded. Can be prevented.

  Here, the heat radiation effect of the power module 1 according to the present embodiment will be specifically described by comparing with a comparative example in which the heat radiation portions 23a and 23b are not provided. 4 is a plan view showing the structure of a power module of a comparative example, and FIG. 5 is a cross-sectional view taken along the line CC in FIG.

  As shown in FIGS. 4 and 5, in the power module 40 of the comparative example, since the heat dissipation portions 23 a and 23 b described above are not formed, the insulating layer 7 is formed on the surface of the metal wiring layer 5 around the semiconductor element 11. Has been.

  In this comparative example, when the power module 40 is driven, as shown in FIG. 6, the current I1 from the P terminal 19 flows through the upper arm side semiconductor element 11a via the P wiring 5a and via the connection portion 25. And flows from the output wiring 5b to the output terminal 21. At this time, current concentration is likely to occur in the region X around the semiconductor element 11a closest to the P terminal 19 among the three semiconductor elements 11a mounted in parallel.

  When current flows from the output terminal 21, as shown in FIG. 7, the current I2 from the output terminal 21 flows through the semiconductor element 11b on the lower arm side via the output wiring 5b and passes through the connection portion 17. Then, it flows to the heat spreader 13 that becomes the N terminal. At this time, current concentration is likely to occur in the region Y around the semiconductor element 11b closest to the output terminal 21 among the three semiconductor elements 11b mounted in parallel.

  Therefore, the amount of heat generated by the semiconductor elements adjacent to the P terminal 19 and the output terminal 21 is increased, and a thermal imbalance occurs with other semiconductor elements mounted in parallel, thereby reducing the performance of the power module. .

  However, in the power module 1 according to the present embodiment, the heat radiating portions 23 a and 23 b with the metal wiring layer 5 exposed are formed around the semiconductor element 11, and the area of the heat radiating portions 23 a and 23 b is set to the amount of heat generated by the semiconductor element 11. It is set according to. That is, since the heat generation amount of the semiconductor element 11 is the largest at the position closest to the P terminal 19 and the output terminal 21, the width of the heat radiation portions 23a and 23b (the exposed area of the metal wiring layer 5) is maximized. And since the emitted-heat amount of the semiconductor element 11 falls as it leaves | separates from the P terminal 19 and the output terminal 21, the width of the thermal radiation parts 23a and 23b is set so that it may become narrow as it leaves | separates from the P terminal 19 and the output terminal 21. Thereby, the thermal imbalance between the several semiconductor element 11 mounted in parallel can be eliminated, and the performance fall of the power module 1 can be prevented.

  Further, in Patent Document 1, since the heat spreader is installed on the mounting surface side of the semiconductor element in order to improve heat dissipation, there is a problem that the size in the height direction is increased. However, in the power module 1 according to the present embodiment, since the insulating layer 7 is removed and the metal wiring layer 5 is exposed to radiate heat, the power module 1 can be radiated without increasing its size in the height direction. Can be improved.

[Second Embodiment]
Next, a power module according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a plan view showing the structure around the semiconductor element of the power module according to the present embodiment, and FIG. 9 is a sectional view taken along the line DD in FIG. In addition, the same number is attached | subjected to the component same as 1st Embodiment, and detailed description is abbreviate | omitted.

  In the first embodiment, the heat radiating portions 23a and 23b are directly formed on the periphery of the semiconductor element 11, but in this embodiment, the insulating layer 70 is formed between the semiconductor element 11 and the heat radiating portions 23a and 23b. Is different.

  As shown in FIGS. 8 and 9, in the power module according to the present embodiment, an insulating layer 70 is formed on the periphery of the semiconductor element 11 in contact with the heat radiating portions 23a and 23b. For example, the insulating layer 70 having a width of about 0.5 mm is formed along the outer periphery of the semiconductor element 11 at a position about 0.1 to 0.3 mm away from the end of the semiconductor element 11. Outside the insulating layer 70, heat radiation portions 23a and 23b having a structure in which the metal wiring layer 5 is exposed are formed. The thickness of the bonding material 27 is preferably set to about 0.1 to 0.3 mm.

  Thus, in the power module according to the present embodiment, since the insulating layer 70 is formed on the periphery of the semiconductor element 11, the bonding material 27 is blocked by the insulating layer 70 having a width of about 0.5 mm when the semiconductor element 11 is mounted. Therefore, it is possible to prevent the bonding material 27 from spreading more than necessary, and thus it is possible to suppress the positional deviation and θ deviation of the semiconductor element 11 and the inclination of the bonding material 27 in the cross-sectional direction.

  On the other hand, when the insulating layer 70 is not formed, a mounting process such as a reflow furnace is performed in the process of mounting the semiconductor element 11 without using a positioning jig or the like, as shown in the plan view of FIG. In some cases, the bonding material 27 spreads more than necessary. Further, as shown in FIG. 11, which is an EE cross-sectional view of FIG. 10, the bonding material 27 may be inclined in the cross-sectional direction. Therefore, the mounting accuracy of the semiconductor element 11 can be improved by forming the insulating layer 70 as described above.

[Third Embodiment]
Next, a power module according to a third embodiment of the present invention will be described with reference to the drawings. FIG. 12 is a plan view showing the structure of the power module according to the present embodiment. In addition, the same number is attached | subjected to the component same as 1st and 2nd embodiment, and detailed description is abbreviate | omitted.

  In the first embodiment, the connection portions 17 and 25 have a structure in which only the portions to which the wires 29 and 31 are connected do not have the insulating layer 7 and expose the heat spreader 13 and the output wiring 5b. However, this embodiment is different from the first embodiment in that the heat spreader 13 and the output wiring 5b are widely exposed without providing the insulating layer 7 not only in the connection portion of the wires 29 and 31 but also in the periphery thereof. doing.

  As shown in FIG. 12, in the power module 50 according to the present embodiment, the connection portions 17 and 25 of FIG. 1 provided for each of the plurality of semiconductor elements 11 are enlarged to form second heat dissipation portions 51 and 53. doing.

  The second heat radiation part 51 has a structure in which the output wiring 5b is exposed without being covered with the insulating layer 7, and is formed by enlarging the connection part 25 in FIG. Thereby, since the 2nd thermal radiation part 51 can perform heat radiation in the whole exposed part, the heat dissipation of power module 50 can be improved. Similarly, the second heat radiating portion 53 has a structure in which the heat spreader 13 is exposed without being covered with the insulating layer 7, and is formed by enlarging the connection portion 17 in FIG. . Thereby, since the 2nd thermal radiation part 53 can thermally radiate in the whole exposed part, the thermal radiation property of the power module 50 can be improved. When the output wiring 5b and the heat spreader 13 are exposed, they are exposed after ensuring insulation from other components.

  As described above, in the power module 50 according to the present embodiment, the connection portions 17 and 25 of FIG. 1 are enlarged around and between the connection portions 17 and 25 to form the second heat radiation portions 51 and 53. Thereby, the heat generated in the semiconductor element 11 can be transferred to the output wiring 5b and the heat spreader 13 through the wires 29 and 31, and can be radiated from the exposed portions of the second heat radiation portions 51 and 53. Therefore, the heat dissipation of the power module 50 can be improved.

[Fourth Embodiment]
Next, a power module according to a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 13 is a plan view showing the structure of the power module according to the present embodiment. In addition, the same number is attached | subjected to the component same as 3rd Embodiment, and detailed description is abbreviate | omitted.

  As shown in FIG. 13, in the power module 60 according to the present embodiment, the width of the second heat radiating portions 61 and 63 is set according to the amount of heat generated by the connected semiconductor element 11 according to the third embodiment. Is different.

  That is, in the second heat radiating portion 61, the semiconductor element closest to the P terminal 19 among the semiconductor elements 11 a mounted in parallel has the largest amount of heat generation, so the area connected to the semiconductor element (output wiring) 5b (exposed area) is set to be the largest. And since the emitted-heat amount of the semiconductor element 11a becomes small as it leaves | separates from the P terminal 19, the area of the 2nd thermal radiation part 61 is set so that it may become narrow according to it.

  Similarly, in the second heat radiating portion 63, the semiconductor element closest to the output terminal 21 among the semiconductor elements 11b mounted in parallel has the largest amount of heat generation, so the width of the portion connected to the semiconductor element ( The exposure area of the heat spreader 13) is set to be the largest. And since the emitted-heat amount of the semiconductor element 11b becomes small as it leaves | separates from the output terminal 21, the area of the 2nd thermal radiation part 63 is set so that it may become narrow according to it.

  As described above, in the power module 60 according to the present embodiment, the size of the second heat radiating portions 61 and 63 is set according to the amount of heat generated by the connected semiconductor elements 11. Thereby, since heat dissipation of the semiconductor element 11 having a large calorific value can be promoted compared to other semiconductor elements, the thermal imbalance among the plurality of semiconductor elements 11 can be improved, and the heat dissipation of the power module 60 can be improved. Can be improved.

[Fifth Embodiment]
Next, a power module according to a fifth embodiment of the present invention will be described with reference to the drawings. FIG. 14 is a plan view showing the structure around the semiconductor element of the power module according to this embodiment, and FIG. 15 is a cross-sectional view taken along the line FF of FIG. In addition, the same number is attached | subjected to the component same as 1st-4th embodiment, and detailed description is abbreviate | omitted.

  As shown in FIGS. 14 and 15, the power module according to the present embodiment is different from the first to fourth embodiments described above in that the substrate is filled with a filler 81 such as a resin.

  Further, when the power module is filled with resin or the like, a filler 81 made of a material having a thermal conductivity higher than that of the insulating layer 7 is used. Specifically, the insulating layer 7 uses an epoxy resin having a thermal conductivity of about 1 W / m · K, and the filler 81 has a high thermal conductivity silicone gel having a thermal conductivity of about 2 to 4 W / m · K. Or an epoxy transfer mold resin with high thermal conductivity.

  Thus, in the power module according to the present embodiment, the filler 81 having a thermal conductivity higher than that of the insulating layer 7 is filled. As a result, even if the exposed heat dissipating parts 23a and 23b are closed with the filler 81, the heat transfer from the heat dissipating parts 23a and 23b to the filler 81 is promoted, and the heat dissipation of the power module can be improved. .

  The above-described embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and even if it is a form other than this embodiment, as long as it does not depart from the technical idea of the present invention, it depends on the design and the like. Of course, various modifications are possible.

DESCRIPTION OF SYMBOLS 1, 40, 50, 60 Power module 3 Board | substrate 5 Metal wiring layer 5a P wiring 5b Output wiring 7,70 Insulating layer 11, 11a, 11b Semiconductor element 13 Heat spreader 15 Radiator 17, 25 Connection part 19 P terminal 21 Output terminal 23a , 23b Heat radiation part 27 Bonding material 29, 31 Wire 33, 35 Gate signal line 51, 53, 61, 63 Second heat radiation part 81 Filler

Claims (5)

A power having an insulating substrate, a metal wiring layer having a predetermined shape formed on the substrate, and an insulating layer covering the metal wiring layer, and mounting a plurality of semiconductor elements connected to the metal wiring layer A module,
Around the plurality of semiconductor elements, there is formed a heat radiating portion that is not covered with the insulating layer and the metal wiring layer is exposed, and the size of the heat radiating portion is set according to the amount of heat generated by the semiconductor elements. Power module characterized by   The power module according to claim 1, wherein an insulating layer is formed on a peripheral edge of the semiconductor element in contact with the heat radiating portion. A connection portion for connecting the wiring from the semiconductor element to the metal wiring layer by exposing the metal wiring layer without covering with the insulating layer is provided for each of the plurality of semiconductor elements,
The connection part provided for each of the plurality of semiconductor elements is enlarged around the connection part and between the connection parts to form a second heat radiating part. Power module.   The power module according to claim 3, wherein the width of the second heat radiating portion is set according to the amount of heat generated by the semiconductor element.   The power module according to any one of claims 1 to 4, wherein the power module is filled with a filler having a thermal conductivity higher than that of the insulating layer.

Images