High current properties of a microspring contact for flip chip packaging

The high current properties of a micro spring pressure contact are characterized. The spring has large compliance (>30um) compared to other packaging technologies and fits in a 180um pitch 2d array. Daisy chains of spring contacts in a silicon package show stable resistances for 250 mA DC soaks at 65C. At 1 amp, failure near the spring tip or body was observed. Simultaneous force and resistance measurements suggest there is no spring force softening. Finite element modeling is performed to study the current and temperature distribution and provide failure mode insight. The results suggest a 10mg (100uN) micro spring with large compliance can be reliable for high current applications.