Metal working – Method of mechanical manufacture – Electrical device making
Patent
1998-06-03
2000-04-25
Arbes, Carl J.
Metal working
Method of mechanical manufacture
Electrical device making
29832, 295921, 29593, A05K 330
Patent
active
060528931
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for manufacturing a resin-encapsulated electronic product which consists of a substrate on which required electronic components are mounted and are entirely sealed in a resin for packaging.
BACKGROUND ART
A resin-encapsulated electronic product is generally manufactured through such processes as described below. Specifically, as shown in FIG. 2A, the product is assembled such that a double-side printed circuit substrate 1, on both sides of which predetermined printed patterns are formed, is mounted with necessary electronic components 2-4 by soldering and is connected with lead elements 7 at its both ends, so as to have certain required functions, for example, as a gas meter or other appliances. Next, as shown in FIG. 2B, the entire printed circuit substrate 1 including the electronic components 2-4 is inserted into a cavity 10 formed by a lower mold 8 and an upper mold 9, after which both molds 8, 9 are clamped together. Successively, a thermoplastic resin material 12 which has been heated at a high temperature and thus melted is injected into the cavity 10 through an injection orifice 11. After the thermoplastic resin 12 has been set by being cooled, the molds 8, 9 are removed, resulting in a resin-encapsulated electronic product 13 which is covered with a package layer 17 of the thermoplastic resin 12 and thereby protected from an outer atmosphere as shown in FIG. 2C.
However, the above-described conventional manufacturing method has such a drawback that when the thermoplastic resin 12 is injected into the cavity 10 from the orifice 11, the heated and melted resin 12 tends to cause various defects: for example the electronic components 2-4 may be damaged by heat; a part of solder paste which connects the electronic components 2-4 on the substrate 1 may melt and flow away; or electronic components may be shoved and thus displaced from a certain mounting position. There has been a problem of decrease in the yield of such resin-encapsulated electronic products 13 due to these defects.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a manufacturing method of small electronic components, by which a decline in the yield is prevented.
To accomplish the above said object, the method for manufacturing a resin-encapsulated electronic product according to the present invention comprises the steps of: a component mounting step of mounting a necessary electronic component on a substrate; a coating layer forming step of forming a coating layer for covering and sealing the substrate in its entirety including the electronic component with a coating material having high heat resistance; and a package layer forming step of forming a package layer for covering and sealing a circumference of the coating layer with a thermoplastic resin material.
According to the manufacturing method of the present invention, in the package layer forming step, the electronic component, the printed circuit substrate, and the solder paste are all protected by the coating layer which has a distinct heat-resisting property and are thereby prevented from being directly contacted with the melted thermoplastic resin. Accordingly, the electronic components are prevented from being damaged by heat, since the heat stress exerted thereto is alleviated due to the coating layer which blocks the heat conductance from the thermoplastic resin. Also, the shearing strain which is exerted on the electronic components and the solder paste from the inflow of the thermoplastic resin is remarkably reduced as compared with the case in which they are not covered with the coating layer because they are fixed by the coating layer. Thus, it is avoided that the electronic components are displaced or a part of the solder paste melts and flows away. Accordingly, highly favorable sealing in terms of functions and reliability can be achieved with the package layer of the thermoplastic resin, and the yield of the finished resin-encapsulated electronic product is remarkably enhanced.
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Fukushima Tetsuo
Suetsugu Kenichiro
Yoshida Koichi
Arbes Carl J.
Matsushita Electric - Industrial Co., Ltd.
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