Sockets containing elastomeric elements have been successful in connecting very high density leadless chip packages and LGAs to PWBs (printed wiring boards). Connections are made by sandwiching the elements between the two mated substrates, producing a zero insertion force contact. The elastomer effectively seals out moisture and other degrading environments, ensuring long, reliable operation. The two elastomeric elements that are the most effective are the layered connectors and the metal-in-elastomer elements. These elements are described, and the development of sockets for MCMs (multichip modules) and chip carriers is described. Attention is given to test and burn-in sockets, permanent connections, and electronic package design.
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