Development of conductive plastics with mixed Pb/Sn solder for injected wiring

摘要

Three dimensional wiring by injection molding is proposed by using two shot molding where conductive plastic is used instead of the other resin. Assuming that injected wiring can be realized based on this method, it would be essential to develop materials with the conductivity as metals and with injection formability. In this study, the development of conductive plastics was attempted by using soldering powder as the conductive filler. In the kneading of plastic and metal powder, the metal must not to be in liquid form. One possible method of achieving this is to use semi-molten (mashy state) metal and knead it with solid metal. Semi-molten metal which is partly liquid and partly solid can be realized in certain temperature ranges by using solder compositions other than eutectic crystal solder. Conduction is realized when the metal powder contact each other in this state. The ratio of solid to liquid can also be controlled by changing the composition and temperature. Based on the above assumptions, the conductivity of the kneaded material was investigated experimentally in this study. The solder content was changed from 5 vol％ to 60 vol％ and the conductivity was evaluated. The results showed that a solder content of 50 vol％, produces conductivity in the order of 10{sup}(-5)Ω·cm a level at which the material can be used for wiring.