Abstract
Thermal failures in printed circuit boards (PCB) primarily occur in plated through holes (PTH) due to stress induced by the dielectric material onto the copper of the PTH. The thermomechanical properties of the dielectric material are known to influence the stress, but an exact relationship has never been established. PCBs made from six different FR-4 dielectric materials were thermally cycled to compare the effects of coefficient of thermal expansion (CTE), decomposition temperature (Td), and glass transition temperature (Tg). Td was found to be the most significant factor for temperatures below the Tg, but its effect varied among different materials with the same Td value. Tg appears to only be important when the environmental temperature is close to the Tg. Further research into material properties is proposed.