Improving the Manufacturing Test Interval and Costs for Telecommunication Equipment

Generally, most circuit packs of telecommunications 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. A production sampling plan is developed to address manufacturing testing of high volume circuit packs. The sampling plan is designed to control both the producer's and consumer's risk to be 10 to 20 percent. Factory and field reliability circuit pack data are analyzed to determine the acceptable quality level and the limiting quality level (i.e., unacceptable quality level) that are needed in establishing a sampling plan.