A Method to Evaluate PCBA Suppliers' Pb Free vs. Leaded Processes for Telecom Applications

摘要

The purpose of this program was to evaluate the solder joint reliability, using the IPC-9701 standard as a guideline, of PCBAs that were assembled with conventional leaded and ROHS compliant lead free processes and to evaluate the capabilities of multiple PCBA assembly houses. 6 sample groups of 26 samples each from 3 different suppliers were subjected to a full qualification plan, SEM, cross-sectional imaging and EDX analysis. The groups consisted of lead free (SAC) test coupons and standard leaded (SnPb) test coupons. The test coupons were populated with surface mount daisy chained dummy components. The component finishes were SnCu and the board finishes were immersion Ag. The coupons were subjected to mechanical strength (lead pull testing, vibration and impact tests), long term reliability (damp heat, temperature cycling and whisker growth tests) and solder joint quality (cross-sectioning, SEM imaging and EDX of components). The test results were analyzed to compare the capabilities of the 3 PCBA assembly houses and to evaluate the relative differences between the conventional leaded and ROHS compliant lead free processes.