Determination of acceleration factor in predicting the field life of plated through holes from thermal stress data

Accelerated thermal stress tests nowadays have widely been used in qualification and reliability assessment of printed wiring boards (PWBs). Predicting the field life of plated through holes (PTHs) from test data has been a primary goal of this type of testing. Understanding the PTH cycles to failure (CTF) versus temperature relationship and having a good estimate of acceleration factor (AF) not only expedites the data processing process but also helps in optimizing test conditions and minimizing the number of tests, and hence, reducing the test cost. In this paper, three different PTH CTF-temperature models, including an inverse power law (IPL) model, an IPC model, and an enhanced PTH fatigue-life prediction model, are discussed and evaluated in their effectiveness of determining acceleration factors for the purpose of PTH field life prediction under different test conditions. In addition, using the third model, AF influencing factors, including PTH geometric dimensions, PWB glass transition temperatures (Tg), and the temperature dependency of PWB material properties, are also discussed to provide information for accelerated test design in PWB qualification and reliability assessment.