Analysis of the Electronic Assembly Repair Process for Lead-Free Parts Under Combined Loading Conditions

Abstract

The conversion from tin-lead (SnPb) to lead-free electronics has created concern amongst engineers about the reliability of electronic assemblies and the ramifications that reliability changes may have on the life-cycle cost and availability of critical systems that use lead-free electronics. In this paper, the impact of lead-free solder on the repair of electronic assemblies subject to combined thermal and vibration loading is studied. The cost, repair time, and availability of boards are quantified using a previously developed repair simulator for a test board developed and tested by the Joint Council on Aging Aircraft & Joint Council on Pollution Prevention that includes ceramic leadless chip carrier, thin small outline package, and plastic ball grid array packaged parts using SnPb and lead-free solders. This paper describes the process of calibrating a physics-of-failure reliability simulator using experimental highly accelerated life testing test results for a specific board assembly and using the calibrated model to generate failure distributions corresponding to combined thermal and vibration loading over an actual product life cycle for use in the repair simulator. The results of the repair simulation indicate that longer dwell times appear to cause more damage than larger Δ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> ; under combined loading conditions, SnPb appears to be more reliable than tin-silver-copper (for the board and parts considered in this paper) and as a result, repair cost is lower; and the number of failures and repair times track repair costs (depending on the capacity of repair process).