This paper describes a highly accelerated life test (HALT, USPCBT) method for rapid qualification testing of STH PWB(Silver Through Hole Printed Wiring Boards). This method was carried out to be an alternative to the present time-consuming standard 1344 hours life testing(THB). The accelerated life test conditions were $121^{circ}C$/95%R.H. at 50V bias and without bias. Their results are compared with those observed in the standard 1344 hours life test at $40^{circ}C$/95%R.H. at 50V bias and without bias. The studies were focused on the samples time-to-failure as well as the associated conduction and failure mechanisms. The abrupt drop of insulation resistance is due to the absorption of water vapour. And the continuous drop of insulation resistance is due to the Ag migration. The ratios of time-to-failure of HALT(USPCBT) to THB were 25 and 11 at 50V bias and without bias respectively.