JP2016174034A - Semiconductor power module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor power module which achieves high heat radiation performance and enables simplification of work related to heat treatment.SOLUTION: A semiconductor power module 1 includes: an insulation substrate 10 in which a first conducting layer 11 is provided on one surface 10a and a second conducting layer 12 is provided on the other surface 10b; a semiconductor element 20 disposed on the one surface 10a side; and a heat sink 30 disposed on the other surface 10b side. The heat sink 30 has folding fins 31 formed by folding a metal plate. The semiconductor element 20 and the first conducting layer 11, and the sink 30 and the second conducting layer 12 are joined through solder 40 having the same melting point.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a semiconductor power module.

  The semiconductor power module is applied to a power conversion device having a semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor), for example. In a semiconductor power module, it is necessary to efficiently dissipate heat generated from a semiconductor element to keep the temperature of the semiconductor element below a predetermined temperature. 2. Description of the Related Art Conventionally, as a semiconductor power module having a semiconductor element heat dissipation structure, for example, a power conversion device described in Patent Document 1 is known.

  The power conversion device described in Patent Literature 1 includes a semiconductor element on one surface side of an insulating substrate and a heat dissipation substrate on the other surface side of the insulating substrate. A plurality of heat radiating fins are formed on the heat radiating substrate, and the heat radiating fins are arranged in the cooling flow path in a direction parallel to the flow of the cooling liquid. The heat generated from the semiconductor element is transferred to the heat radiating substrate through the insulating substrate, and is radiated to the coolant through the heat radiating fins.

Japanese Patent No. 3982180

  Conventionally, in a semiconductor power module, a thermal interface such as silicon grease or a silicon sheet is sandwiched between the insulating substrate and the heat dissipation substrate in order to improve the adhesion between the insulating substrate and the heat dissipation substrate. However, this thermal interface has a thermal conductivity of, for example, about 1 to several W / m · K, and has a thermal conductivity that is two orders of magnitude smaller than that of a metal material.

  Here, it is conceivable to directly bond the insulating substrate and the heat dissipation substrate with a metal material such as a brazing material. However, when a semiconductor element is bonded to the insulating substrate in advance with solder or the like, There is a risk that the solder melts due to heat. For this reason, it is necessary to use a brazing material having a melting point different from that of solder, and it is necessary to perform heat treatment at different temperatures on the insulating substrate twice for each of the semiconductor element and the heat dissipation substrate, which is complicated.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a semiconductor power module that has high heat dissipation performance and that can simplify the work related to heat treatment.

In order to solve the above-mentioned problems, the present invention is arranged on the one surface side, with an insulating substrate provided with a first conductive layer on one surface and a second conductive layer on the other surface. A semiconductor power module including a semiconductor element and a heat sink disposed on the other surface side, wherein the heat sink includes a folding fin formed by bending a metal plate, and the semiconductor element and the first A configuration is adopted in which the conductive layer and the heat sink and the second conductive layer are bonded to each other through a bonding metal having the same melting point.
By adopting this configuration, in the present invention, the heat sink has a folding fin, and the heat sink is bonded to the second conductive layer of the insulating substrate by the same bonding metal as the semiconductor element. Since the folding fin has a large aspect ratio, it has higher heat dissipation performance, lighter weight, and smaller heat capacity than a normal fin of the same volume. For this reason, the difference in the heat capacity between the heat sink and the semiconductor element is reduced, and the joining of the semiconductor element and the heat sink to the insulating substrate can be achieved by collective reflow with a unified bonding metal.

Further, in the present invention, the heat sink has a base plate joined to the folding fin via a second joining metal having a melting point higher than that of the joining metal, and the base plate and the second conductive layer are A configuration is adopted in which bonding is performed via the bonding metal.
By adopting this configuration, in the present invention, the folding fin is joined to the second conductive layer via the base plate. The base plate is more flat than a folding fin formed by bending a metal plate. For this reason, the joining precision of a heat sink and a 2nd conductive layer can be improved, and the void (space | gap) which generate | occur | produces in a joining metal can be suppressed.

Moreover, in this invention, the structure that the said folding fin and the said 2nd conductive layer are joined via the said joining metal is employ | adopted.
By adopting this configuration, in the present invention, the folding fin is directly bonded to the second conductive layer via the bonding metal. For this reason, the heat capacity of the heat sink is further reduced, and the difference in heat capacity between the heat sink and the semiconductor element is further reduced. For this reason, the collective reflow which unified the joining metal can be performed more suitably.

In the present invention, the folding fin includes a plurality of fin portions having a first thickness and a connecting portion that connects the adjacent fin portions with a second thickness smaller than the first thickness. The configuration of having the above is adopted.
By adopting this configuration, in the present invention, the heat capacity of the connecting portion is relatively smaller than that of the fin portion of the folding fin. Therefore, in the connection part of the folding fin, the difference in heat capacity with the semiconductor element becomes smaller, and batch reflow in which the bonding metals are unified can be performed more suitably.

  ADVANTAGE OF THE INVENTION According to this invention, the semiconductor power module which has high heat dissipation performance and can simplify the operation | work which concerns on heat processing is obtained.

It is a section lineblock diagram of a semiconductor power module in a 1st embodiment of the present invention. It is a section lineblock diagram of a heat sink in a 1st embodiment of the present invention. It is a figure which shows the work flow which concerns on the heat processing of the semiconductor power module in 1st Embodiment of this invention. It is a figure which shows the flow which concerns on the heat processing of the conventional semiconductor power module as a comparative example. It is a section lineblock diagram of a semiconductor power module in a 2nd embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

(First embodiment)
FIG. 1 is a cross-sectional configuration diagram of a semiconductor power module 1 according to a first embodiment of the present invention. FIG. 2 is a cross-sectional configuration diagram of the heat sink 30 in the first embodiment of the present invention.
As shown in FIG. 1, the semiconductor power module 1 includes an insulating substrate 10, a semiconductor chip 20 (semiconductor element), and a heat sink 30.

  The insulating substrate 10 is an insulating material formed in a flat plate shape. As the insulating substrate 10, for example, an insulating metallized substrate having high thermal conductivity can be preferably used. Specifically, the insulating substrate 10 is made of silicon nitride, aluminum nitride, or the like. A first conductive layer 11 is provided on one surface 10 a of the insulating substrate 10. A second conductive layer 12 is provided on the other surface 10 b of the insulating substrate 10.

  The first conductive layer 11 is provided on one surface 10a of the insulating substrate 10 by plating or vapor deposition. The first conductive layer 11 is a circuit pattern such as copper or aluminum having conductivity. On the other hand, the second conductive layer 12 is provided on the other surface 10b of the insulating substrate 10 by plating or vapor deposition. The second conductive layer 12 is a conductive base pattern such as copper or aluminum. The insulating substrate 10 is configured to be sandwiched between the first conductive layer 11 and the second conductive layer 12.

  The semiconductor chip 20 is a semiconductor element such as an IGBT. The semiconductor chip 20 is disposed on the one surface 10 a side of the insulating substrate 10. The semiconductor chip 20 is bonded to the first conductive layer 11 via the solder 40 (bonding metal) on the one surface 10a side. Although two semiconductor chips 20 are shown in FIG. 1, the number of semiconductor chips 20 may be one, or three or more semiconductor chips 20 may be provided.

  The circuit configuration of the semiconductor power module 1 is known and described in, for example, Japanese Patent Application Laid-Open No. 2013-223384, Japanese Patent Application Laid-Open No. 2014-38982, and the like. Includes a positive electrode pattern (not shown), a negative electrode pattern, and an output pattern. For example, a positive electrode terminal and a negative electrode terminal of a power source are connected to the positive electrode pattern and the negative electrode pattern, and input via the positive electrode pattern and the negative electrode pattern. The semiconductor chip 20 converts the converted power into alternating current (or direct current), and outputs the converted power to the outside through an output pattern.

  The heat sink 30 includes a folding fin 31 and a base plate 32. The folding fin 31 is formed by bending a metal plate. As the metal plate, a metal plate having high thermal conductivity such as copper or aluminum can be suitably used. The thermal conductivity of copper is, for example, 398 W / m · K. The thermal conductivity of aluminum is, for example, 236 W / m · K. The folding fin 31 is formed by bending a single metal plate a plurality of times and has a high aspect ratio.

  As illustrated in FIG. 2, the folding fin 31 includes a plurality of fin portions 33 and a plurality of connection portions 34. The fin portion 33 is formed by folding metal plates. The fin portion 33 has a first thickness t1. The tip 33a of the fin portion 33 is a folded portion of the metal plate, and is larger than the first thickness t1 of the folded portion of the metal plate. A plurality of fin portions 33 are provided at intervals.

  The connection part 34 connects between the adjacent fin parts 33. The connecting portion 34 is disposed on the base end 33 b side opposite to the tip 33 a of the fin portion 33. The connecting portion 34 has a flat portion 34a. The flat surface portion 34a extends in a direction orthogonal to the protruding direction from the proximal end 33b of the fin portion 33 toward the distal end 33a. The connecting portion 34 has a second thickness t2 that is smaller than the first thickness t1. In the connection portion 34, the metal plates are not folded, and the second thickness t2 is half of the first thickness t1.

  The base plate 32 is a flat metal plate. As the metal plate, similarly to the folding fin 31, a metal plate having high thermal conductivity such as copper or aluminum can be suitably used. As shown in FIG. 1, one surface 32 a of the base plate 32 is joined to the second conductive layer 12 via solder 40. Further, the other surface 32b of the base plate 32 is joined to the folding fin 31 via a brazing material 41 (second joining metal). The brazing material 41 only needs to have a higher melting point than the solder 40.

Then, the operation | work which concerns on the heat processing which manufactures the semiconductor power module 1 of the said structure is demonstrated.
FIG. 3 is a diagram showing a work flow related to the heat treatment of the semiconductor power module 1 in the first embodiment of the present invention. FIG. 4 is a diagram showing a flow relating to heat treatment of a conventional semiconductor power module as a comparative example.

  In the work flow shown in FIG. 3, first, solder printing is performed on the insulating substrate 10 and the heat sink 30. In the heat sink 30, the folding fin 31 and the base plate 32 are bonded together with a brazing material 41 in advance. Solder 40 having the same melting point is disposed on the first conductive layer 11 of the insulating substrate 10 and one surface 32a of the base plate 32 by solder printing. The solder 40 may be a solder sheet as well as paste printing.

  Next, the semiconductor chip 20 is mounted on the solder 40 printed on the insulating substrate 10. Next, the reflow jig is mounted, and the insulating substrate 10 on which the semiconductor chip 20 is mounted is placed on the solder 40 printed on the heat sink 30. Thereafter, a combination of the insulating substrate 10, the semiconductor chip 20, and the heat sink 30 is put into a vacuum reflow furnace, and batch reflow is performed. Thereafter, the semiconductor power module 1 is manufactured through a post-process such as a wire bonder.

  For example, the thickness of the first conductive layer 11 is 0.4 mm, the thickness of the second conductive layer 12 is 0.3 mm, the thickness of the base plate 32 is 2 mm, the first conductive layer 11, the second conductive layer 12, and the base plate Assuming that the areas 32 are substantially the same and the forming material is copper, the volume ratio of copper between the insulating substrate 10 and the base plate 32 is (0.4 + 0.3): 2, that is, approximately 1: 3. Then, the heat capacity ratio between the insulating substrate 10 and the base plate 32 that affects the reflow is also about 1: 3. Therefore, for example, if the thermal time constant of the upper part including the insulating substrate 10 is about 10 seconds, the time constant of the entire semiconductor power module 1 is about 40 seconds, and sufficient reflow can be performed.

  On the other hand, in the work flow of the comparative example shown in FIG. 4, first, solder printing of solder A is performed on an insulating substrate. Next, a semiconductor chip is mounted on the solder A printed on the insulating substrate. Next, a reflow jig is mounted and the first reflow is performed. On the heat sink side, solder B is printed on the heat sink. As the solder B, one having a melting point lower than that of the solder A is selected. Next, an insulating substrate on which a semiconductor chip is placed is mounted on the solder B printed on the heat sink. Next, a reflow jig is mounted and a second reflow is performed. Thereafter, a semiconductor power module is manufactured through a post-process such as a wire bonder.

  In the semiconductor power module of the above comparative example, assuming a configuration that is normally employed, assuming that the thickness of the heat sink is about 10 mm and the area is about twice that of the insulating substrate, the copper of the insulating substrate and the heat sink The volume ratio is approximately 1:30. Then, the heat capacity ratio between the insulating substrate and the heat sink that affects the reflow is also approximately 1:30. If the difference in heat capacity is large, the temperature of the insulating substrate quickly rises, whereas the temperature of the heat sink does not rise easily, and soldering on the heat sink side becomes difficult. For this reason, it is necessary to use materials having different melting points for the solder A for mounting the semiconductor chip and the solder B under the insulating substrate 10.

  As described above, in the comparative example, since the solders A and B having different melting points are used, the heat treatment (reflow) is required twice, and the work is complicated. On the other hand, in the present embodiment shown in FIG. 3, since the solder 40 having the same melting point is used, batch reflow is possible, and heat treatment is only required once, and the operation can be simplified. That is, the heat sink 30 of the present embodiment has a folding fin 31 formed by bending a metal plate. Since the folding fin 31 has a large aspect ratio, the heat dissipation performance is higher than that of a normal fin of the same volume. Higher and lighter, with a smaller heat capacity. For this reason, the difference in heat capacity between the heat sink 30 and the semiconductor element 20 is reduced, and the joining of the semiconductor element 20 and the heat sink 30 to the insulating substrate 10 can be achieved by batch reflow in which the solder 40 is unified.

  In the present embodiment, the heat sink 30 has a base plate 32 joined to the folding fin 31 via a brazing material 41 having a melting point higher than that of the solder 40, and the base plate 32 and the second conductive layer 12 are made of the solder 40. It is joined via. According to this configuration, the folding fin 31 is joined to the second conductive layer 12 via the base plate 32. The base plate 32 is more flat than the folding fin 31 formed by bending a metal plate. For this reason, the joining precision of the heat sink 30 and the 2nd conductive layer 12 can be improved. Also, voids (voids) generated in the solder 40 can be suppressed. Therefore, heat conduction from the second conductive layer 12 to the heat sink 30 can be performed efficiently.

  Thus, according to the above-described embodiment, the insulating substrate 10 in which the first conductive layer 11 is provided on one surface 10a and the second conductive layer 12 is provided on the other surface 10b, and the one surface 10a. The semiconductor power module 1 has a semiconductor element 20 disposed on the side and a heat sink 30 disposed on the other surface 10b side, and the heat sink 30 has folding fins 31 formed by bending a metal plate. The semiconductor element 20 and the first conductive layer 11, and the heat sink 30 and the second conductive layer 12 are joined together via solder 40 having the same melting point, so that heat dissipation performance is achieved. Therefore, the semiconductor power module 1 can be obtained, which can simplify the work related to the heat treatment.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the following description, the same or equivalent components as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is simplified or omitted.

FIG. 5 is a cross-sectional configuration diagram of a semiconductor power module 1A according to the second embodiment of the present invention.
As shown in FIG. 5, the heat sink 30 </ b> A of the second embodiment is different from the above-described embodiment in that the base plate 32 is not provided.

  In the second embodiment, the folding fin 31 and the second conductive layer 12 are joined via the solder 40. That is, the folding fin 31 is directly bonded to the second conductive layer 12 via the solder 40. According to this configuration, since the base plate 32 is not provided, the heat capacity of the heat sink 30A is further reduced. Then, the difference in heat capacity between the heat sink 30A and the semiconductor element 20 is further reduced. For this reason, the batch reflow which unified the solder 40 can be performed more suitably.

  As shown in FIG. 2, the folding fin 31 includes a fin portion 33 having a first thickness t1 and a connection portion 34 having a second thickness t2 smaller than the first thickness t1. Therefore, the heat capacity of the connecting portion 34 is relatively smaller than that of the fin portion 33 of the folding fin 31. Further, when the folding fin 31 and the second conductive layer 12 are joined, the solder 40 is printed on the connection portion 34 as shown in FIG. Therefore, in the connection part 34 of the folding fin 31, the difference in heat capacity with the semiconductor element 20 becomes smaller, and batch reflow that unifies the solder 40 can be performed more suitably.

  As mentioned above, although preferred embodiment of this invention was described referring drawings, this invention is not limited to the said embodiment. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  For example, a wide band gap semiconductor may be used for the semiconductor chip 20.

  For example, as long as the solder 40 has the same melting point, components and compositions may be different between the upper and lower sides of the insulating substrate 10. Further, the joining metal is not limited to the solder 40 and may be other brazing material.

1, 1A Semiconductor power module 10 Insulating substrate 10a One surface 10b The other surface 11 First conductive layer 12 Second conductive layer 20 Semiconductor chip (semiconductor element)
30, 30A Heat sink 31 Folding fin 32 Base plate 33 Fin part 34 Connection part 40 Solder (joining metal)
41 Brazing material (second bonding metal)
t1 first thickness t2 second thickness

Claims (4)

An insulating substrate having a first conductive layer on one surface and a second conductive layer on the other surface; a semiconductor element disposed on the one surface side; and a semiconductor element disposed on the other surface side. A semiconductor power module having a heat sink,
The heat sink has folding fins formed by bending a metal plate,
The semiconductor power module, wherein the semiconductor element and the first conductive layer, and the heat sink and the second conductive layer are bonded to each other via a bonding metal having the same melting point. The heat sink has a base plate joined to the folding fin through a second joining metal having a melting point higher than that of the joining metal,
The semiconductor power module according to claim 1, wherein the base plate and the second conductive layer are bonded via the bonding metal.   The semiconductor power module according to claim 1, wherein the folding fin and the second conductive layer are bonded via the bonding metal. The folding fin is
A plurality of fin portions having a first thickness;
4. The semiconductor power module according to claim 3, further comprising a connection portion that connects between the adjacent fin portions with a second thickness smaller than the first thickness. 5.

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