JPS61103672A - Adhesion structure - Google Patents

Abstract

PURPOSE:To elevate a reliability with absorbing a strain and with preventing the cracks of articles and the peeling of a connection part by connecting with heating with arranging the metal plate consisting of plural layers among the articles having different thermal expansions. CONSTITUTION:The forming solder 7 of the metallic plate of three layers structure pinching the solder 5 with a high melting point by a low melting point solder 6 is pinched between a solder plated radiator 1 and the ceramics substrate 2 with printed 4 electrode on its back face and heated at the temp. that the low melting point solder 6 is melted but high melting point solder 5 is not melted. Then due to one part of the high melting point solder 5 being melted but the majority being not melted according to a diffusion phenomenon the both 1, 2 are connected and the difference in the thermal expansions of the both 1, 2 cause by the temp. cycling is absorbed by the thickness of the solder. Even in case of the inner layer 5 of the metallic plate 7 being made of the metal having the thermal expansion coefficient which is larger than the ceramics substrate 2 but smaller than the radiating plate 1 the strain to be caused between the both 1, 2 is dispersed into the two of the substrate 2 and inner layer 5, and the inner layer 5 and radiator 1 and the similar effect as above is obtainable.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a structure for bonding articles with different thermal expansions using molded solder, and in particular to a structure for bonding articles with different thermal expansion using molded solder. Regarding adhesive structure.

(Prior art) Conventionally, when attaching a heat sink to a ceramic substrate on which a hybrid IC is mounted, electrodes are printed on the back side of the ceramic substrate as shown in Japanese Patent Application Laid-Open No. 58-116237. Sandwich the molded solder between the
It was used to perform solder bonding by heating.

(Problems to be Solved by the Invention) FIG. 2 is a diagram illustrating a conventional solder bonding structure. As shown in the figure, aluminum alloy or copper with good thermal conductivity is used for the heat dissipation body 1, but these have a large coefficient of thermal expansion, and the ceramic substrate 2 has a small coefficient of thermal expansion, so both When connected by solder 3, there was a problem that the solder connection part peeled off and the ceramic board cracked due to the temperature cycle. In an adhesive structure in which a metal plate for bonding by heating is arranged between a substrate and a heat sink, the metal plate is made up of an n layer (n layer 3), an outer layer of the metal plate is made of solder, and the metal The inner layer of the plate is made of metal that absorbs strain caused by differences in thermal expansion occurring at the bond between the ceramic substrate and the heat sink. Note that as the metal for absorbing the strain, a solder having a higher melting point than the solder of the outer layer is used, or a metal having a coefficient of thermal expansion larger than that of the ceramic substrate and smaller than that of the heat sink is used.

(Function) In the bonding structure of the present invention, the ceramic substrate and the heat sink are bonded together by the solder in the outer layer, and the strain caused by the difference in thermal expansion is absorbed by the metal in the inner layer. If high melting point solder is used for the inner layer, the inner layer will not melt during bonding, so
A sufficiently thick solder can be applied, and the thickness of the solder absorbs the strain. Furthermore, when a metal having a coefficient of thermal expansion larger than that of the ceramic substrate and smaller than that of the heat sink is used for the inner layer, the strain generated in each outer layer is relatively absorbed.

(Embodiment) FIGS. 1 and 3 are diagrams illustrating the configuration of an embodiment of the present invention. As shown in the same figure, solder.

A molded solder 7, which is a metal plate with a three-layer structure in which high melting point solder 5 is sandwiched between low melting point solder 6, is sandwiched between the heat dissipating body 1 and the ceramic substrate 2 with electrodes 4 printed on the back side. This is heated at a temperature that melts the low melting point solder 6 but does not melt the high melting point solder 5.

In this case, a part of the high melting point solder 5 melts due to the diffusion phenomenon, but most of it does not melt, so the heat sink 1
and the ceramic substrate 2 are connected as shown in FIG. 3, and the solder thickness H can be made sufficiently thicker than in conventional solder connections. In this way, if a thick solder connection is made, the difference in thermal expansion between the ceramic board and the heat sink caused by temperature cycles will be absorbed by the solder thickness K, resulting in the ceramic board cracking or the solder connection surface peeling off. That will no longer be the case. In this case, if the temperature difference between the high melting point solder and the low melting point solder is small, all of the high melting point solder will melt, so it is better that this difference is as large as possible. For example, if eutectic solder with a melting point of 183° C. is used as the low melting point solder, high temperature solder with a melting point of 309° C. is preferable as the high melting point solder. The production of the three-layer solder is a pressing process for forming the solder pad into a predetermined shape, and it is desirable to stack three solder sheets and press them. In this way, the three layers of solder do not separate and are easy to handle, and the number of man-hours does not increase at all compared to the conventional method. Next, a case where the inner layer is made of a metal having a coefficient of thermal expansion larger than that of the ceramic substrate and smaller than that of the heat sink (usually made of aluminum) will be described. In this case, the strain that occurs between the ceramic board and the aluminum heat sink can be dispersed between the ceramic board and the inner layer, and the inner layer and the heat sink, so if the ceramic board breaks or the solder connection surface peels off, That will no longer be the case.

Incidentally, since the thermal expansion coefficient of ceramic is 6X10' and that of aluminum is 23X10', the metal used for the inner layer may have an expansion coefficient clearly within the range. Preferably, the use of a metal having an intermediate coefficient, such as pure iron, is highly effective.

(Effects of the Invention) As explained above, the present invention ensures that even if a ceramic substrate with a different coefficient of thermal expansion and a heat sink are connected, the substrate will not crack or the connection will peel off due to temperature cycles, and the device will be reliable. It has the advantage of improving performance.

Furthermore, the present invention is not limited to the combination of a ceramic substrate and a heat sink, but can also be applied to, for example, soldering a ceramic substrate and electronic components mounted thereon, or fixing a ceramic substrate to a device case by soldering. It can also be used in cases where

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of a prior art, and FIG. 3 is an explanatory diagram of an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Heat sink, 2... Ceramic substrate, 5... High melting point solder, 6... Low melting point solder. Patent applicant: Oki Electric Industry Co., Ltd. Figure 1 Figure 3 Procedural amendment (voluntary) 1. Indication of the case 1982 Patent Application No. 225872 2. Name of the invention Adhesive structure 3. Person making the amendment Relationship with the case Patent application office (105) 1-7-12-4 Toranomon, Minato-ku, Tokyo
Agent Address (〒105) 1-7 Ao-1 Toranomon, Minato-ku, Tokyo
No. 2 No. 5, subject of amendment Column 6 of "Detailed Description of the Invention" in the specification, content of amendment 1, page 2, line 6 of the specification states that "Conventionally, Hybrid I
"C" should be corrected to "conventional electronic components." 2. On page 5, line 7 of the Ministry of Health, the phrase "high temperature solder" has been corrected to "high melting point solder."

Claims (3)

[Claims] (1) In an adhesive structure in which a metal plate is arranged for bonding articles having different coefficients of thermal expansion by heating, the metal plate is n
(n≧3), the outer layer of the metal plate is made of solder, and the inner layer of the metal plate is made of a metal that absorbs strain due to differences in thermal expansion occurring at the bonded portion between the articles. Adhesive structure characterized by: (2) The adhesive structure according to claim 1, wherein the strain-absorbing metal is made of solder having a higher melting point than the solder of the outer layer. (3) The adhesive according to claim 1, wherein the strain-absorbing metal is made of a metal having a coefficient of thermal expansion larger than that of one of the articles and smaller than that of the other article. structure.