JP2018107367A - Power semiconductor module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure bondability of a semiconductor chip in a manufacturing process of a power semiconductor module.SOLUTION: A power semiconductor module includes: a cooler 2 having a first surface and a second surface which serve as heat transfer surfaces; a first substrate 3a to which a first semiconductor chip 3b is joined by a first joint material 3c which melts at a predetermined melting temperature, the first substrate 3a joined to the first surface of the cooler 2; a second substrate 4a to which a second semiconductor chip 4b is joined by a second joint material 4c having a melting temperature different from the first joint material 3c, the second substrate 4a joined to the second surface of the cooler 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power semiconductor module.

  For example, Patent Document 1 discloses 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 joined by solder (joining material), and the insulating layer and the heat conductor are joined by copper material (joining material). Patent Document 1 discloses a configuration in which a heat conductor is mounted with a power semiconductor module on a plurality of surfaces.

JP-A-10-284585

  When joining a semiconductor chip to a plurality of surfaces of a heat conductor, it is necessary to join the semiconductor chip to the second surface after first joining the semiconductor chip to the first surface. In patent document 1, even when a semiconductor chip is mounted on a plurality of surfaces of a heat conductor, the same bonding material is used on all surfaces. For this reason, when joining to the 2nd surface of a cooler, the heat of a heating furnace is transmitted also to the 1st surface, the joining material of the board | substrate previously joined to the 1st surface remelts, and the semiconductor in a 1st surface The chip and the substrate may be peeled off.

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

  In order to achieve the above object, according to 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, the first semiconductor While the chip is bonded, the second substrate is bonded by the first substrate bonded to the first surface of the cooler, and the second bonding material having a melting temperature different from that of the first bonding material, and the cooler. A second substrate bonded to the second surface, wherein the first semiconductor chip generates a larger amount of heat than the second semiconductor chip, and the first bonding material has a thermal conductivity higher than that of the second bonding material. A configuration is adopted in which is set high.

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

  According to the present invention, the melting temperature is different between the first bonding material and the second bonding material. First, the substrate is bonded to the cooler using a bonding material having a higher melting temperature on one heat transfer surface, and then the substrate is bonded using a bonding material having a lower melting temperature on the other heat transfer surface. By bonding to the cooler, the bonding material having the higher melting temperature is not re-melted in the bonding process using the bonding material having the lower melting temperature.

It is a mimetic diagram showing the section of the power converter with which the power semiconductor module concerning one embodiment of the present invention is provided.

  Hereinafter, an embodiment of a power semiconductor module according to an embodiment of the present invention will be described 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. FIG. 1 is a schematic diagram illustrating a cross section of a power conversion device 1 included in the power semiconductor module according to the present embodiment.

The power semiconductor module in the present embodiment includes a 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 part 2c is provided with a plurality of heat radiating fins so as to be perpendicular to the top plate part 2a and the bottom plate part 2b. 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 (three in this embodiment) of first electronic board units 3 are provided on the outer surface (first surface) of the top plate portion 2a, which is the heat transfer surface of the cooler 2, and the first board 3a, A semiconductor chip 3b and a 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 bonded to the outer surface of the top plate portion 2a of the cooler 2 by a silver sintered material bonding layer 3c. 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 opposite to 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 melting silver fine powder by firing at about 300 ° C., and further cooling and solidifying the molten silver fine powder. The sintered silver bonding layer 3c has a remelting temperature of about 960 ° C. and a thermal conductivity of about 420 W / m · K.

  A plurality (three in the present embodiment) of the second electronic substrate unit 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 substrate 4a and the second semiconductor are provided. A chip 4b and a 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 bonded to the outer surface of the bottom plate portion 2b of the cooler 2 by a solder bonding layer 4c. The second substrate 4a is provided with conductive members 4d on both sides between 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 bonding 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 during heat generation and a larger amount of heat generation than the second semiconductor chip 4b. Further, 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, in the top plate portion 2a of the cooler 2, the first electronic board unit 3 is attached. Specifically, silver nanoparticles are disposed between the conductive member 3 d provided on the first substrate 3 a and the top plate portion 2 a of the cooler 2. The silver nanoparticles are heated and pressurized through the conductive member 3d and the top plate portion 2a of the cooler 2, whereby the surface film is removed and the particles come into contact with each other. Further, the silver nanoparticles are sintered at about 300 ° C., so that the particles are melted and bonded to each other and welded to the conductive member 3d and the top plate portion 2a, so that the conductive member 3d and the top plate portion 2a are bonded. The silver sintered material bonding layer 3c is formed between the two.

  Next, the mounting operation of the second electronic board unit 4 is performed on the bottom plate portion 2 b of the cooler 2. Specifically, solder is disposed between the conductive member 4 d provided on the second substrate 4 a and the bottom plate portion 2 b of the cooler 2. Further, the solder is melted by being heated at about 270 ° C. by a heating furnace (not shown), and solidified while being in close contact with the conductive member 4d and the bottom plate portion 2b of the cooler 2, so that the conductive member 4d A solder bonding layer 4 c is formed between the bottom plate portion 2 b of the cooler 2. At this time, although 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, the silver sintered material bonding layer 3c on the top plate portion 2a side The remelting temperature does not increase to about 960 ° C., and the silver sintered material bonding layer 3c of the top plate portion 2a does not remelt.

  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. Thereby, the silver sintered material joining layer 3c is not remelted by the joining operation of the second electronic substrate unit 4 to the cooler 2.

  Furthermore, according to the present embodiment, the silver sintered material bonding layer 3c has a higher thermal conductivity than the solder bonding layer 4c. The first semiconductor chip 3b has a heat generation temperature higher than that of 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, and the first semiconductor chip 3b can be efficiently cooled. The chip 3b can be prevented from overheating.

  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 spirit of the present invention.

  In the above embodiment, the first electronic board unit 3 and the second electronic board unit 4 are each joined to the cooler 2 by three, 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.

DESCRIPTION OF SYMBOLS 1 ... Power converter device, 2 ... Cooler, 3 ... 1st electronic board unit, 3a ... 1st board | substrate, 3b ... 1st semiconductor chip, 3c ... Silver sintered-material joining layer, 4 ... Second electronic substrate unit, 4a... Second substrate, 4b... Second semiconductor chip, 4c.

Claims (2)

A cooler having a first surface and a second surface as heat transfer surfaces;
A first substrate bonded to the first surface of the cooler and bonded to the first semiconductor chip by a first bonding material that melts at a predetermined melting temperature;
A second substrate bonded to the second surface of the cooler and a second semiconductor chip bonded by a second bonding material having a melting temperature different from that of the first 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 a higher thermal conductivity 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.

Images