Temperature accelerated life test (ALT) at the circuit board level

The purpose of ALT (Accelerated life test) lies in evaluating the failure rate of an item by obtaining expedient information on the lifetest distribution of a material or product by applying stress levels more severe than those specified by standard conditions, in order to greatly reduce the time needed to observe stress reactions or to magnify such reactions within a given time frame so as to ultimately reduce the time, cost, and effort required to evaluate the item. It is not difficult to determine the failure rate at the component level using ALT. However failure rate prediction at the circuit board level is difficult with ALT, because various electrical parameters at the component level have to be taken into account, and determination of accelerated factors is not so easy. This paper describes temperature ALT conducted for the purpose of estimating failure rates and analyzing forms of failure during operation at the circuit board level of a telecommunication system. In this method, a temperature higher than the operational temperature of an item was applied to it in order to generate failure rate data within a short period of time to estimate the failure rate during actual system operation. We proposed systematically the test temperature, test duration, and the sample size for high temperature ALT of the circuit board of a telecommunication system.