End Item Temperature Test -- An Improved LRU-Level Screen

This paper details the evaluation and implementation of Honeywell's End Item Temperature Test (EITT) process which functionally tests each production LRU at the customer-required temperature extremes. An aircraft system that formerly utilized 100% screening of electronic parts was selected for this process. A fixture was developed to allow the end item to be thoroughly tested while inside an environmental chamber. Using EITT, Honeywell replaced screening with EITT for specifically selected parts. The EITT adds thermal testing in addition to the normal environmental stress screening and acceptance test procedure steps. EITT also provides an effective tool for root cause failure analysis. The EITT-produced units (LRUs) were found to have 47% fewer IC removals than the previously built systems that were subjected to the 100% part screening. By reducing the part screening-caused damage, a 42% reduction was observed in mechanical damage such as bent leads. Since production implementation in 1998, only 2 field failures have been observed on the more than 300,000 EITT / characterized ICs in the field.