Development of probing mark analysis model [IC testing]

A probe card is conventionally used in wafer-level testing to check defects in ICs. A stable contact resistance must be achieved when each probe is in contact with the bonding pad. A mechanical contact using excessive pressure can cause over sizing of the probing mark that may lead to damage of the die pad as well as permanent defibrination of the probe tip. In this paper, a 3D computational model has been developed for analyzing dynamic deformations of contact phenomena during probe testing by using explicit finite element analysis. The elastoplastic constitutive model of the tungsten probe is taken from micro-tester tensile testing to get the stress-strain relations. Actual probing tests with a single probe were performed to investigate the size of the probing mark. Probe tip and probing mark formation characteristics can be investigated either from tests or simulations. Both experimental and numerical methods can be employed as useful tools to study the relation between pressure forces and depth of the probing mark as well as the probe tip deformations.