Contact properties of micromachined Ni probes

The authors have investigated the aluminum-contact properties of two types of micromachined nickel probes, designed for low-contact force and high density probe cards. One probe is a micro-machined Ni curl-up cantilever, which was realized utilizing electroplating deposition of two layers having different internal stress, and has the low force constant of 0.1-0.3 N/m. The other is the Ni microcantilever designed to make contact to pad electrodes by buckling at a load of about 5 mN. This buckling contact has the advantage that the contact forces of all the probes could be almost uniform. For the two types of probes, although low contact resistance could not be obtained by only mechanical pressure, a contact resistance of around 1 Ω was obtained using the fritting process, in which a voltage is applied between a pair of probes. For the case of the curl-up micro-cantilevers, the force required to make low resistance contact was smaller than 10 μN. A fritting current larger than 200 mA makes it possible to decrease the contact resistance to around 1 Ω for both types of micro-machined probes.