No-Clean Assembly Process Conditions ―Effects on Flip-Chip/Underfill Reliability

摘要

The residue material generated by no-clean fluxes during flip-chip solder processing has been shown to effect the performance of underfill materials. The analyses conducted during this experiment show that both reflow process conditions as well as flux chemistry may have a profound impact on flip-chip underfill processing and reliability. High temperature reflow processes, such as those developed for the emerging lead-free alloy systems, lead to accelerated flip-chip assembly failures. High resolution CSAM analysis may aid the manufacturing engineer to identify potential insoluble flux residues prior to stress testing. It is theorized that compositional changes of the flux residue created by high temperature reflow conditions generate an insoluble intertayer at the underfill - component interface. This interlayer becomes the weak point within the assembly for moisture ingress, corrosion and delamination. Flux residues that do not form insoluble interiayers dissolve into the underfill material during processing. This results in an ideal situation in which the underfill material forms an intimate, contamination-free interface with the components of the assembly. The residues, typically consisting of mono and poly-carboxylic acids react with the underfill epoxy to form polymer chains.