Vibration at Low and Extreme Cold Temp for QFN Assembly Reliability

Abstract

This paper first briefly updates the failure test data in Weibull plots for QFN package assemblies under standard thermal cycle/shock conditions. The same test vehicle configuration was used to perform combined vibration at low/extreme cold temperatures. Two QFN assemblies were subjected to 50g three-dimensional random vibration under two temperature conditions. One QFN assembly was subject to random vibration in a highly accelerated life test (HALT) chamber held at a low temperature of −20°C whereas the other one was tested at an extreme cold temperature of −100°C.These temperatures were chosen based on a predictive analytical model that showed the QFN solder joints at −20°C and at −100°C will be at the static elastic/inelastic strain ranges, respectively. Only four representative daisy-chain QFN assemblies were monitored during HALT testing, but all daisy-chains were verified manually after test. In addition, failure analyses were performed by optical inspection, scanning electron microscopy (SEM), and cross-sectional microscopy to determine failure mechanisms. The paper presents a brief discussion on analytical approach, it provides detailed testing results, and optical/SEM images from failure analyses.