Micro-Coil Spring Interconnection for Ceramic Grid Array Packaged Integrated Circuits

摘要

This method of interconnecting ceramic integrated circuits to organic printed circuit boards (PCBs) is designed to substantially increase the life of the interconnections. This is accomplished by providing a means of compensating for the shear stresses produced by thermal excursions as a result of the large mismatch of coefficients of thermal expansion between the integrated circuit and the printed circuit board. The micro-coil spring is highly flexible and allows significant movement to counteract the thermal expansion forces between the ceramic and the organic PCB. Once a ceramic part with micro-coil springs is mounted onto an organic PCB, each micro-coil spring essentially forms two solder bumps: one at the ceramic surface and one at the organic PCB surface. Both solder bumps are encapsulated in the BeCu closed coils. These two solder bumps are interconnected with active coils of the BeCu micro-coil spring (see figure). These active coils provide the flexibility to compensate for the opposing forces.