Blowholing in PTH Solder Fillets

This is the third paper in the series of eight, studying voids and blowholes in PTH printed circuit boards. In the previous papers the industrial significance of this problem has been established and moisture identified as the primary cause of the gassing. Now, particular attention is focused on the understanding of the mechanisms and kinetics of moisture uptake in the FR‐4 laminate. From the authors' data the rate of moisture uptake and the rate of drying of laminate can be predicted as a function of temperature and relative humidity.