Effects of PWB design factors on PTH reliability

Based on the barrel stress distribution model, the effect of printed wiring board (PWB) design factors such as plated through-hole (PTH) aspect ratio, the ratio of plating thickness over PTH radius, the ratio of board influence radius over PTH radius and glass transition temperature on PTH barrel stress and lifetime were studied quantitatively. Equivalent temperature load was introduced to found the barrel stress distribution model under different glass transition temperature. Results show that PTH life is sensitive to design factors when PWB operating at vicinities of the yielding temperature load. The PTH aspect ratio shows more significant impact when fixing the ratio of board influence radius over PTH radius. For the fixed PWB thickness, decrease PTH diameter results in the increase of PTH barrel stress and the decrease of PTH lifetime. PTH barrel strain sharply increases at the glass transition temperature. Results also show that the constant strain concentration coefficient is different in elastic and plastic stage.