Abstract
Abstract The combinations of one kind lead free solder(Sn/Ag3.8-4.0/Cu0.5-0.7) and two kinds of surface finishing (OSP and ENIG) were investigated. By suitable design of PCB board, the analyze of single joint reliability during the four point cycle bending could be monitored and recorded in real time. The pads used for four point cyclic bending test are 400um in diameter. However, the pads used in thermal cycle aging test are 350um in diameter. The pad size is very small. The effect of IMC (intermetallic compound)growth and the situation of high temperature testing environment are taken into consideration in this investigation. The cycle date of four point cyclic bending was analyzed by using two-parameter Weibull distribution. The result of shear test and four point cyclic bending test showed that the OSP pad is batter than ENIG pad in all test situation. However, the OSP pad had thicker IMC layer. The IMC growth layer will become a weaker layer and cause the damage area flatter and brittle. The pull residual strength will be stable after two hundred cycles of thermal cycle aging. The fracture mode changed from smooth to coarsing during the thermal aging. However, the resistance of two kinds of pads did not have significant change.