Improving the manufacturing test interval and costs for telecommunication equipment

Generally, most circuit packs of telecommunication systems are processed through a manufacturing test process that may include in-circuit test, functional test, factory environmental stress testing or environmental stress screening (ESS), and system tests. Some of these tests, like ESS, may also be due to customer or Bellcore requirements. However, it is both expensive and time consuming to process all production circuit packs through all these tests, particularly when the test yields in some of these tests are close to 100 percent, and the field reliability performance is much better than expected. In this paper, we describe an approach for developing sampling plans for performing these tests. We feel that this approach of using production sampling plans in manufacturing coupled with statistical analysis of factory test yield and field reliability data to identify the best circuit pack candidates, can be applied to any large production volume telecommunication system for reducing both the manufacturing test interval and costs.