Thermomechanical Characterization and Geometric Optimization of Multi-Layer Cantilever Probe Card Needles for Wafer Testing

Probe cards play an essential role in wafer testing, with multi-layer cantilever designs accommodating the high pin-count requirements of modern IC devices. However, dense probe arrangements increase the risk of interference, while variations in the geometric parameters of the needles in the different layers can lead to inconsistent contact forces and scratch marks on the bond pads. Accordingly, this study employs an experimental and simulation approach to investigate the dynamic deformation behavior of the probe needles of a five-layer cantilever probe card. The study commences by investigating the thermomechanical properties of Rhenium Tungsten (ReW) needles using a microforce tensile tester at various temperatures and strain rates. The stress-strain curves are employed to construct an empirical constitutive model to describe the thermomechanical characteristics of the needles. A three-dimensional finite element model is then constructed of a five-layer cantilever probe card. The validity of the FE model is confirmed by comparing the predicted contact forces of the five needles with the experimental measurements obtained using a commercial probe card inspection system. Finally, the FE model is integrated with Castigliano's second theorem and a multi-objective genetic algorithm (MOGA) to determine the needle geometry parameters of the multi-layer cantilever probe card that maximize the uniformity of the scrub mark length and shape across the different layers of the card. The results indicate that adjusting the taper length and bending angle significantly improves scrub consistency, offering a systematic approach for optimizing multi-layer probe card designs.