Issues in Assembly

2017/3/21 16:13:07

Hi All,

I have been looking in to some failures of PCB's in Assembly. After SMT the boards are stored for different periods of time in high humility environment (72% RH and 21.4 degrees Celsius) before being sent to Assembly to be handsoldered/put through a wave machine.

Is there anyway to work out how long say a FR4 board can sit in 72% RH at 21.4 degrees Celsius absorbing moisture without blistering by handsoldering/going through the wave machine?

I have seen a few articles on moisture absorption but no linear/non-linear data that correlates moisture absorbed over time and blistering from handsoldering/using a wave machine.