Electronic products are being stressed by increasing operating temperatures and higher assembly temperatures. Silicon and product power consumption are increasing as the silicon densities and signaling frequencies increase. And, the transition to lead-free solders is resulting in higher thermal excursions during assembly. Both of these conditions are impacting material selection during product design and are having an impact on product qualification, and influencing long term via reliability. This paper details the results of an Intel investigation of printed circuit board materials, fabrication processes, and design variables and the resulting impact on board reliability after lead-free assembly. Results were baselined against standard tin-lead assembly for purposes of comparison. Printed circuit board process and design variables examined included via size, layer count, board thickness, and laminate material. Also examined were the variation within an individual supplier and the variation across multiple suppliers using the same materials. The paper details the test board configurations used in the study, the lead-free and tin-lead assembly profiles to which the boards were subjected, and the test methods employed to collect the data. The test data highlights key trends in the reliability data as a function of changes in the variables tested.
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