Design and testing of conductive polysilicon beam leads for use in a high-density biomedical connector

A study was conducted to measure and characterize the reliability of polysilicon cantilever beams with electroplated gold pads for use in a high-density biomedical connector. In this design, an array of beams is brought into contact with a corresponding array of 30 mum high gold bumps, forming electrical connection. Analytical computations of multi-layer beams were performed, including the effects of residual stresses. Beam leads of various lengths and widths with electroplated gold contact pads on their ends were tested over 1000 cycles to determine their mechanical reliability, and to measure their contact resistance with gold bumps on a separate substrate. The dimensions of the polysilicon beam that produce the least breakage were determined to be 400 mum long by 125 mum wide. For a beam having a calculated contact force of similar to100 muN, the initial contact resistance was 764 mOmega. After 1000 connect/disconnect cycles, beams of this type had an average final contact resistance of 1.598 Omega. These results demonstrate that very high-density connectors with high mechanical reliability and low-contact resistance can be fabricated.