Experimental and statistical analyses of surface-mount technologyPLCC solder-joint reliability

The mechanical integrity of surface-mount technology (SMT) plastic leaded chip carrier (PLCC) solder joints has been studied by a four-point mechanical flexure fatigue test. The effects of printed circuit board (PCB) pad surface composition and testing temperature on solder-joint reliability are emphasized. Three sets of PCBs have been tested, one with Cu-Ni-Sn pad surface metallurgy, one with Cu-Ni-Au, and one with SMOBC/SSC (solder mask over bare copper selective solder coating). The solder composition was the 63 wt.%Sn/37 wt.%Pb eutectic. A two-parameter Weibull distribution was used for the lifetime model for these three products. The uniformity, quality, reliability, and a comparison of these products are discussed. The joints formed on Cu-Ni-Au and SMOBC boards were appreciably more reliable than those formed on the Cu-Ni-Sn board