Comprehensive Assembly and Reliability Study of 0201´s for High Reliability Applications for Utilizing both a Pb-Free and Sn/Pb Assembly Process

A comprehensive study was undertaken to evaluate various board design parameters, assembly and reliability of 0201´s as it relates to high reliability products. The design parameters considered included four pad designs, two trace width terminations, three orientations, three board thicknesses and four component to component spacing on a large PWB panel. The assembly parameter evaluation included, SnPb and Pb-free solder pastes for board assembly, which were built at four different board assembly locations. The reliability testing included ATC, shear and mechanical shock testing. The purpose of this study was to evaluate the design space that will result in high assembly process yield and high solder joint reliability. A 0402 control leg was included in the design for comparison. About 400,000 of the 0201 components were assembled for this study. The assembly and design parameters were evaluated on all three board thicknesses (62 mils, 93 and 126 mils). Among the four pad designs two of the designs were intended for under the BGA placement (via to via). Among the remaining four pad designs, two of them showed better assembly process yields than the rest. Within the design space considered, no significant trends in assembly yield were observed due to trace terminations, component to component spacing and board thicknesses. For the reliability testing the boards were temperature cycled between 0-100degC per IPC9701. Shear testing was performed prior to and after the temperature cycling testing to observe any deterioration in the solder joint reliability for any of the pad designs considered. Mechanical shock testing at 340G´s 1.6 ms input pulse was also conducted for the different design parameters.