Accelerated testing for the selection of the most reliable microvia design

Abstract

The small size and high density of microvias makes them susceptible to developing cracks resultant from the stresses that produce mechanical and thermal fatigue on fragile structure. Their use in support of the critical functions of systems regardless of the industry type brings up the importance of their high reliability. Having in mind the overall industry concern, the design team of the transmitter/receiver (T/R) modules has developed the test for selection of the most reliable design which would satisfy the very stringent reliability requirements of this complex system. The accelerated thermal cycling and thermal dwell test has evaluated and compared the variations of a group of legacy deign microvia shapes to the proposed design solutions and was able to aid in selection of the most desirable design solution. Out of 24 new design variations each using four different materials, the best reliability was found in the design D3A-B where the reliability results did not depend on the material used. Majority of other new designs for high reliability results used Material #4, the fact that poses a certain limitation on the design requirements. The test was highly accelerated and automated, and the effort has provided well identified distinctive results for prevention of mission critical failures.