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SMT termination visual and solderability issues.

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Carol Stirling


SMT termination visual and solderability issues. | 14 February, 2006

CRITICAL DILEMA! Has anyone run into the problem described below and if so, what was the fix (besides not dealing with this Supplier)? Also, we do not have component manufacturing process experience.

We are purchasing a surge resistor that functions as desired, but we cannnot consistently get a solderable terminantion from the Manufacturer. The parts have copper terminations plated with 90/10 tin/ lead. The parts are showing visible copper/brass colored material on the inward formed L-shaped ribbon leads terminations. In addition, the parts that look `good' are not accepting solder to 610 STD. During solderability testing, the solder globs and spikes on the termination. These parts were stripped and batch plated as initially they failed solderability due to oxidization. The reworked parts are certified as having 8-12 microns of plating coverage.

The Supplier is adament the parts are good, knowing we are an IPC CLass 3 facility. Personally, I have never come across this type of a product before and to this point in time, we can not find another manufacturer whose product fits the engineering requirement.

Can anyone advise if re-stripping and re-plating will be detrimental to the copper termination? The molded body will be fine. We can't purchase new material in the required time line as it not a stocked item.

If someone who has knowledge of resistor type part manufacturing would like to contact me and share some information, it would be appreciated.

Thanks in advance for the help,


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Cal Kolokoy


SMT termination visual and solderability issues. | 14 February, 2006

That is a tough situation and a tough answer for us SMT forum participants. After all, most of us are in the business of placing and soldering components to circuit boards, and you know the saying; you can't make solder joints with an unsolderable surface. It is physically impossible.

I, too, don't personally have component manufacturing experience, but if you're unplating and then soldering to bare copper, my first guess would be that you need a very high activity & high-solids flux, say an RMA type formulation, to solder or tin the terminations. You would probably then have to put the devices through some type of cleaning process.

I would start by researching component termination plating methods.

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