| Popis: |
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. |
