Current crowding study of a micro spring contact for flip chip packaging

Current crowding of a micro spring pressure contact under high current is studied. The spring conducts >; 250 mA electrical current between chips, has large mechanical compliance (>; 30 μm) compared to other packaging technologies, and fits in a 180 μm pitch 2d array. At 250 mA and 65°C, daisy chains of 134 spring contacts in a silicon package show stable resistances and hot spot temperature rises of less than a degree. At 1 A, failure near the spring tip or body is observed. Finite element modeling is performed to study the current density distribution and provide failure spot insight. A strategy is proposed to avoid current crowding.