Design and in-situ mechanical testing system for probe card/UV-LIGA-Ni microspring

In this study, we designed an S-type micro-spring for a probe card and fabricated it by UV-LIGA/Ni electroforming. The mechanical properties of electroformed Ni exhibits a lower Young´s modulus and a much higher tensile strength than those of conventional bulk material. Using a scanning electron microscope, a newly developed testing machine enables in-situ observation of a microspring during and after loading cycles. During repeated cycles, voids developed on the surface of the microspring, resulting in a decreased spring constant. This determines fatigue strength, and the S-N curves indicate superior characteristics.