Improving Electronic Packaging Through Product and Process-Driven Analysis: A PWB Case Study
Scholand, A. J; Peak, R. S.; Fulton, R. E. (1997) CAE/CAD and Thermal Management Issues in Electronic Systems, EEP-Vol. 23/HTD-Vol. 356, Agonafer, D., et al., eds., ASME Intl. Mech. Engr. Congress & Expo., Dallas, pp. 23-31.
This paper demonstrates how the use of product analysis combined with process data can provide information about the product quality impact of high-level process decisions. A specific case study involving the warpage of two PWB designs as they move through a reflow oven is presented. A new approximate thermal model is derived which analyzes processing rate dependent warpage, an important metric of product quality for ovens with edge support conveyance systems. Agreement between the theoretical model and prior published experimental results was found to be strongly dependent on the precise temperature dependent material property values used, underlining the need to have accurate thermo-mechanical characterizations of PWB constituent materials. A set of property values based on data published in the literature was assembled which provided a fair match to experimental results, giving sufficient confidence to apply the model predictively. For the case study presented, the model predicts a 10% decrease in processing time will increase board warpage by at most 11.5%. This case study illustrates how product analysis can arm production managers with the information they need to make informed, effective decisions which trade off the economic gains realizable by implementing process improvements against the product quality impact of those improvements.