Characterization of FR-4 Printed Circuit Board Laminates Before and After Exposure to Lead-free Soldering Conditions

Abstract

The transition to lead-free soldering of printed circuit boards (PCBs) using solder alloys such as Sn/Ag/Cu has resulted in higher temperature exposures during assembly compared with traditional eutectic Sn/Pb solders. The knowledge of possible variations in the PCB laminate material properties due to the soldering conditions is an essential input in the selection of appropriate laminates.

An experimental study was conducted to investigate the effects of lead-free processing on key thermomechanical, physical, and chemical properties of a range of FR-4 PCB laminate materials. The laminate material properties were measured as per the IPC/UL test methods before and after subjecting to multiple lead-free soldering cycles.

The effect of lead-free soldering conditions was observed in some of the material types and the variations in properties were related to the material constituents. Fourier transform infrared (FTIR) spectroscopy and combinatorial property analysis were performed to investigate the material-level transformations due to soldering exposures.