JP6710155B2 - Power semiconductor module and method of manufacturing power semiconductor module - Google Patents

Description

The present invention relates to a power semiconductor module.

For example, in Patent Document 1, a power semiconductor module (power semiconductor module) in which an insulating layer is formed on a heat conductor (cooler) having a heat dissipation function and a power semiconductor chip (semiconductor chip) is mounted on the insulating layer Is disclosed. In the power semiconductor module of Patent Document 1, the insulating layer and the semiconductor chip are bonded by solder (bonding material), and the insulating layer and the heat conductor are bonded by copper material (bonding material). In addition, Patent Document 1 discloses a configuration in which a heat conductor mounts a power semiconductor module on a plurality of surfaces.

JP, 10-284685, A

When bonding semiconductor chips to a plurality of surfaces of the heat conductor, it is necessary to first bond the semiconductor chips to the first surface and then bond the semiconductor chips to the second surface. In Patent Document 1, even when semiconductor chips are mounted on a plurality of surfaces of the heat conductor, the same bonding material is used on all the surfaces. Therefore, when joining the second surface of the cooler, the heat of the heating furnace is also transferred to the first surface, and the joining material of the substrate previously joined to the first surface is remelted, and the semiconductor on the first surface The chip and the substrate may peel off.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to ensure the bondability of a semiconductor chip in a manufacturing process of a power semiconductor module.

In order to achieve the above object, in the present invention, as a first means, a cooler having a first surface and a second surface as heat transfer surfaces and a first bonding material that melts at a predetermined melting temperature are used to form a first semiconductor. The chips are joined together, the first substrate joined to the first surface of the cooler, and the second semiconductor chip joined together by the second joining material having a melting temperature different from that of the first joining material and the cooler. A second substrate bonded to the second surface of the first semiconductor chip, the first semiconductor chip has a larger heat generation amount than the second semiconductor chip, and the first bonding material has a thermal conductivity higher than that of the second bonding material. Is set to be high.

As a second means, in the first means, the first bonding material is a silver sintered material and the second bonding material is solder.

According to the present invention, the first joining material and the second joining material have different melting temperatures. First, the substrate is joined to the cooler by using the joining material with the higher melting temperature on one heat transfer surface, and then the substrate is joined with the joining material with the lower melting temperature on the other heat transfer surface. By joining to the cooler, the joining material having the higher melting temperature will not be re-melted in the joining process using the joining material having the lower melting temperature.

It is a schematic diagram which shows the cross section of the power converter device with which the power semiconductor module which concerns on one Embodiment of this invention is equipped.

An embodiment of a power semiconductor module according to an embodiment 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 recognizable. FIG. 1 is a schematic diagram showing a cross section of a power conversion device 1 included in a power semiconductor module according to this embodiment.

The power semiconductor module according to the present embodiment includes the power conversion device 1. As shown in FIG. 1, the power conversion device 1 includes a cooler 2, a first electronic board unit 3, and a second electronic board unit 4.
The cooler 2 includes a top plate portion 2a, a bottom plate portion 2b facing the top plate portion 2a, and a heat radiating portion 2c provided between the top plate portion 2a and the bottom plate portion 2b. The heat radiating portion 2c has a plurality of heat radiating fins standing upright so as to be perpendicular to the top plate portion 2a and the bottom plate portion 2b. When water passes between the heat radiating fins, heat is released from the surface of the heat radiating fins. ing. The cooler 2 is a water cooling jacket that cools the first electronic board unit 3 and the second electronic board unit 4 by radiating the heat of the first electronic board unit 3 and the second electronic board unit 4 from the radiation fins.

A plurality of (three in the present embodiment) first electronic board units 3 are provided on the outer surface (first surface) of the top plate portion 2a that is the heat transfer surface of the cooler 2, and the first board 3a and the first board 3a are provided. The semiconductor chip 3b and the silver sintered material bonding layer 3c (first bonding material) are provided. The first substrate 3a is an insulating substrate on which the first semiconductor chip 3b is mounted, and is joined to the outer surface of the top plate portion 2a of the cooler 2 by the silver sintered material joining layer 3c. In addition, the first substrate 3a is provided with conductive members 3d on both sides between the silver sintered material bonding layer 3c. The conductive member 3d is provided to fix the silver sintered material bonding layer 3c to the first substrate 3a.

The first semiconductor chip 3b is mounted on the surface of the first substrate 3a facing the surface to be bonded to the cooler 2 by the silver sintered material bonding layer 3c, and generates heat at a maximum of about 140° C. when energized. .. The silver-sintered-material bonding layer 3c is obtained by baking fine silver powder at about 300° C. to melt the fine silver powder, and then cooling and solidifying the fine silver powder. The silver-sintered-material bonding layer 3c has a remelting temperature of about 960° C. and a thermal conductivity of about 420 W/m·K.

A plurality of (three in the present embodiment) second electronic board units 4 are provided on the outer surface (second surface) of the bottom plate portion 2b that is the heat transfer surface of the cooler 2, and the second board 4a and the second semiconductor are provided. The chip 4b and the solder bonding layer 4c (second bonding material) are provided. The second substrate 4a is an insulating substrate on which the second semiconductor chip 4b is mounted, and is joined to the outer surface of the bottom plate portion 2b of the cooler 2 by the solder joining layer 4c. Further, the second substrate 4a is provided with the conductive members 4d on both surfaces between the second substrate 4a and the solder bonding layer 4c. The conductive member 4d is provided to fix the solder bonding layer 4c to the second substrate 4a.

The second semiconductor chip 4b is mounted on the surface of the second substrate 4a opposite to the surface bonded to the cooler 2 by the solder bonding layer 4c, and generates heat at a maximum of about 110° C. when energized. The solder joining layer 4c has a melting temperature and a remelting temperature of about 270° C., and a thermal conductivity of about 62 W/m·K.

That is, the first semiconductor chip 3b has a higher maximum temperature when generating heat and a larger amount of heat generation than the second semiconductor chip 4b. The silver sintered material bonding layer 3c has a higher thermal conductivity than the solder bonding layer 4c, and the remelting temperature is higher than the melting temperature of the solder bonding layer 4c.

A method of assembling the first electronic board unit 3 and the second electronic board unit 4 and the cooler 2 in the power conversion device 1 in this embodiment will be described.
First, the work of attaching the first electronic substrate unit 3 is performed on the top plate portion 2 a of the cooler 2. Specifically, silver nanoparticles are arranged between the conductive member 3d provided on the first substrate 3a and the top plate portion 2a of the cooler 2. Then, the silver nanoparticles are heated and pressed through the conductive member 3d and the top plate portion 2a of the cooler 2, whereby the film on the surface is removed and the particles come into contact with each other. Furthermore, when the silver nanoparticles are sintered at about 300° C., the particles are melted and bonded to each other, and the silver nanoparticles are welded to the conductive member 3d and the top plate portion 2a, whereby the conductive member 3d and the top plate portion 2a. And the silver sintered material bonding layer 3c are formed between them.

Next, the attachment work of the second electronic substrate unit 4 is performed on the bottom plate portion 2b of the cooler 2. Specifically, solder is arranged between the conductive member 4d provided on the second substrate 4a and the bottom plate portion 2b of the cooler 2. Further, the solder is melted by being heated at a temperature of about 270° C. by a heating furnace (not shown), and is solidified in a state in which the conductive member 4d and the bottom plate portion 2b of the cooler 2 are in close contact with each other. A solder joint layer 4c is formed between the bottom plate portion 2b of the cooler 2 and the bottom plate portion 2b. At this time, the heat of the heating furnace and the heat applied from the heating furnace to the bottom plate portion 2b of the cooler 2 are transmitted to the top plate portion 2a side, but the silver sintered material bonding layer 3c on the top plate portion 2a side is The re-melting temperature does not rise to about 960° C., and the silver sintered material bonding layer 3c of the top plate 2a does not re-melt.

According to the present embodiment, the silver sintered material bonding layer 3c is set to have a higher melting temperature and remelting temperature than the solder bonding layer 4c. This prevents the silver sintered material bonding layer 3c from being remelted by the bonding work of the second electronic substrate unit 4 to the cooler 2.

Furthermore, according to this embodiment, the silver sintered material bonding layer 3c has a higher thermal conductivity than the solder bonding layer 4c. Further, the first semiconductor chip 3b has a higher heat generation temperature than the second semiconductor chip 4b. Therefore, the high calorific value of the first semiconductor chip 3b can be efficiently transmitted to the cooler 2 by the silver sintered material bonding layer 3c, the first semiconductor chip 3b can be efficiently cooled, and the first semiconductor It is possible to prevent the chip 3b from overheating.

The preferred embodiments of the present invention have been described above with reference to the drawings, but the present invention is not limited to the above embodiments. The shapes, combinations, and the like of the respective 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 spirit of the present invention.

In the above-described embodiment, the first electronic board unit 3 and the second electronic board unit 4 are configured to be joined to the cooler 2 by three, respectively, but the present invention is not limited to this. The first electronic board unit 3 and the second electronic board unit 4 may be four or more or two or less.

1... Power converter, 2... Cooler, 3... First electronic substrate unit, 3a... First substrate, 3b... First semiconductor chip, 3c... Silver sintered material bonding layer, 4... Second electronic substrate unit, 4a...Second substrate, 4b...Second semiconductor chip, 4c...Solder bonding layer

Claims (3)

A cooler having both surfaces consisting of a first surface and a second surface as a heat transfer surface;
A first semiconductor chip is bonded by a first bonding material that melts at a predetermined melting temperature, and a first substrate that is bonded to the first surface of the cooler by the first bonding material ;
A second semiconductor chip is bonded to the first bonding material by a second bonding material having a different melting temperature, and a second substrate is bonded to the second surface of the cooler by the second bonding material .
The first semiconductor chip generates a larger amount of heat than the second semiconductor chip,
The power semiconductor module, wherein the first bonding material is set to have higher thermal conductivity and melting temperature than the second bonding material. The first bonding material is a silver sintered material,
The power semiconductor module according to claim 1, wherein the second bonding material is solder. In the method of manufacturing a power semiconductor module,
The first substrate is bonded to the first surface, which is the heat transfer surface of the cooler, by the first bonding material that melts at a predetermined melting temperature, and the first semiconductor chip is bonded to the first substrate by the first bonding material. A first joining step,
The second substrate is joined to the second surface, which is a heat transfer surface of the cooler, which is on both sides of the first surface, by the second joining material having a melting temperature different from that of the first joining material, and by the second joining material. A second bonding step of bonding a second semiconductor chip to the second substrate,
The first semiconductor chip generates a larger amount of heat than the second semiconductor chip,
The method for manufacturing a power semiconductor module, wherein the first bonding material is set to have higher thermal conductivity and melting temperature than the second bonding material.

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