MECHANICAL STRESS CONTROL AND MANAGEMENT IN THE ASSEMBLY PROCESSES FOR Sn-Pb AND Pb-FREE SYSTEM PHASE Ⅱ - LEAD-FREE PROCESS AND PRODUCT TRANSITION Phase Ⅰ - A Methodology for Process Risk Prevention and Understanding of Residue Stress on the Reliabilit

摘要

As a phase Ⅱ future study, a Lead-Free test vehicle with advanced testability feature for extensive reliability study on all representative package types and solder joint were designed. To streamline the lead-free product and process transition, a MPRST model is proposed to facilitate the lead-free material selection, perform package and solder joint reliability test, conduct product level process qualification, and achieve total e-SPC manufacturing. Solder alloy assessments were performed on various paste types and surface finishes. A computerized gray level measurement methodology was intelligently created to quantitatively study the color change during the corrosion test. Various surface finish for PCB and leaded devices will factored into Design Of Experiment to assess the solder joint correlation to the reliability scale as well to observe and prevent the tin whisker formation. Advanced design feature to achieve optimal PCB thermal management and wave soldering are layout into the test vehicle to compare to the mathematical model on solder hole fill in the PTH component. Finally, field mechanical stress will be monitored and FEM modeling will be created to assess and infer beyond the limitation of instrumentation. A methodology to eastblished the residue stress under mechanical bending to the reliability scale is proposed. Strengthening mechanism hypothesis for the lead-free Sn-Ag-Cu ternary system was theorized and will be proved in the near future.