It is well established that Pb free alloys tend to solder less readily than Sn/Pb. It is not clear that this is always a major problem, but two factors combine to make it more of a concern for flip chip than for other applications. Not surprisingly, wetting and spreading appears to become less effective as the solder volume is reduced and a larger fraction of it is near the surface. At the same time assembly yields tend to become more sensitive to this. The present paper addresses the assembly of flip chips with Sn/Ag/Cu bumps onto Ni/Au and OSP coated copper pads on organic substrates. Soldering defects observed included incomplete wetting and collapse, as well as poor self centering. The sensitivity to fluxes, reflow profiles, and substrate pads were investigated and potential consequences for assembly yields calculated numerically.
Managing assembly yield in the Printed Circuit Board (PCB) assembly process is crucial in reducing the overall manufacturing cost of a product. Being faced with electronic components that have high interconnect (pin or solder bump) count, density, and complexity, it is extremely important to streamline the manufacturing losses arising from misplaced or poorly assembled components. In order to achieve this goal, yield models are utilized to anticipate and evaluate problems and their causes. This activity could be potentially implemented at the design stage or at least much before the product reaches the manufacturing floor. This research examines some important factors that affect area array (BGA, CSP, flip chip) assembly yields, taking a two-pronged approach to modeling. Achievable yield is classified into placement and assembly components and is estimated using a simulation model.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.