Does anyone have an information or can point me to any studies which identifies any mechanisms/interactions which could explain void creation in Sn63Pb37 PTH solder joints resulting from gold plated leads?
I have been attempting to address a systemic issue with PTH voiding at the wave and selective solder process. The issue impacts multiple assemblies which run Sn63Pb37 alloy, impacts multiple surface finishes and impacts multiple component designs from multiple manufacturers.
The only commonality is that the voiding is isolated to component leads which are gold plated and do not violate J STD-001 4.5.1.a “gold must be removed: From at least 95% of the surfaces to be soldered of the through-hole component leads with >2.54 μm [100 μin] gold thickness and all through-hole leads that will be hand soldered regardless of gold thickness” (we automatically solder wash all components which violate this requirement).
In all cases we have attempted different no clean fluxes and combinations of increased and decreased process parameters (flux deposition, preheat, solder temp, dwell time, localized preheat) without eliminating the voiding. The only process so far which has been shown to completely eliminate the voiding issue is tinning the component leads and removing the gold.
If we get an alternate part which is not manufactured with the gold plating on the leads we do not have any issues with voiding.
Even though we have a solution to the problem by tinning or sourcing non-gold leaded components I would still like to understand the true root cause. This might help me to identify or develop a less time consuming and costly solution.
Has anyone else seen this issue?
If you think there is anything I might have overlooked please let me know.
This message was posted the
Electronics Forum @ SMTA
reply »