Reliability Assessment for Printed Circuit Board in Lead-Free Process

This study aimed to explore Printed Circuit Board (PCB) failure mechanism and recommend appropriate material and handling process for the boards used in lead-free assembly process. In this study, the most stringent conditions in Printed Circuit Board Assembly (PCBA) process was used for various base-materials of PCB, such as Tg, and curing agent. In addition, thermal shock testing at 0∼100°C for 900 cycles was employed to simulate PCB performance during field service. Cross-section analysis was implemented to identify failure modes. Finally, the PCB moisture absorption property was evaluated by exposing the boards in a temperature/humidity chamber at 28°C and 60% RH, that was the worst condition in PCBA production environment. Results indicated that Tg had significant influence to the PCB quality, high Tg materials performs better. During multiple reflow process verification, cross section analysis of high Tg material indicated that Dicy material appear delamination even no electrical failure occurred. As for thermal shock test, high Tg material (either with Dicy or Phenolic curing agent) survived after 900 shock cycles. Also, moisture uptake in assembly environment, even at the worst scenario of 28°C and 60% RH for 120 hours, had not caused any PCB delamination.