| 摘要 |
Thermoplastic printed wiring board spacers are fabricated by providing a water soluble partially hydrolyzed polyvinyl alcohol resin or fully hydrolyzed polyvinyl alcohol resin or a blend of partially hydrolyzed polyvinyl alcohol resin and fully hydrolyzed polyvinyl alcohol resin, the ration thereof depending upon (1) the degree of hydrolyzation of the polyvinyl alcohol resins, (2) crystallinity associated with particular polyvinyl alcohol resins, (3) the fabrication temperatures of the printed wiring board to avoid spacer melting and (4) the degree of solubility in water of the spacer. The spacers are fabricated by injection molding the polyvinyl alcohol resins or desired polyvinyl alcohol resin mixture to provide a molded configuration having a runner system with spacers attached to a sub runner system by a very thin gate. The spacers are removed from the molded configuration by initially cooling the surface of the total molded configuration to a temperature at which the thin gate sections becomes very brittle. The cooled molded configuration is then subjected to tumbling or a jolt whereby the spacers break away from the runner system at the gates.
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