The In-Circuit test is to probe the integrity of the conductivity of the soldering on a PCB at high speed. It has been a very important process in quality controls that checks the correctness of positioning assembled electrical parts such as resistors, capacitors, and ICs, and detects faults of soldering. For the enhancement of the inspection efficiency, The probing devices currently used in industry contact with the solder joint at high speed (0.2~0.4 m/sec). As a consequence, the excessive contact force causes plastic deformation on the surface of a solder joint. The deformed surface is easily corroded by its oxidation. The corroded solder is likely to crack under a small shock. In order to obtain the appropriate inspection speed, and preserve the penetration depth within the limits, the impact model of the rigid probe and the solder joint is needed. In this paper, considering the variant penetration radius R of the contacting probe, the analytical model proposed by Forrestal and Longcope [8~17] is modified, and the model parameters for the four different soldering materials are estimated from experimental data .This enables to predict the final penetration depth, and select the shape of the conical probe tip for given contact force and penetration depth.
