quantify rammifications of silver contamination in eutectic solder? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: April 05, 2020, 01:53:42 am
content: http://www.circuitnet.com/experts/87891.htmlSo long its under 2%, which I assume a silver plating is well under, it does not make the joint brittle. But the answer given is a bit cryptic.Does anyone know more specific data regarding lead bearing solder? Everything I find is lead free related data with plating contamination.Since I assume this data does not exist, does anyone have an idea for a test that would exaggerate the results of this quickly to give some kind of indicator? Something with a vibramotor?

author: WattsThat
author_rank: Frequent Contributor
timestamp: April 05, 2020, 04:16:03 am
content: Contamination? Heck, they add 2% silver to leaded solder. It’s been around since forever.https://www.amazon.com/Kester-Solder-24-7150-0018-ELECTRONIC-SILVER/dp/B01N44GDE4

author: coppercone2
author_rank: Super Contributor
timestamp: April 05, 2020, 04:54:26 am
content: Does it diffuse quickly through the joint?What I was worried about is thinking (despite what the guy said) is that it forms a thin.. greater then 2% layer of silver that fully envelopes the region and is a failure point.I don't understand metal dissociation well enough to be anything less then paranoid. Then again, the copper must do the same thing.. and thats not even a real formula.. I assume the solubility of copper and silver are similar to eutectic solder?Those solders are like all stir mixed (lumped analysis). This feels like a gradient analysis. Do they do something like slow lapping + XRF to determine the alloy to verify platings are safe (slice analysis)?Naturally I think silver is great because when its used in a braze, the strength usually goes up as the content goes up, but brazing is devoid of things like lead typically.I assume, since it typically works (or at least its done, but again not quantified by reliability analysis), that it must either diffuse quickly or at least have some portion of joint where its not present (diffusion to the side? hard to imagine).What I am scared of, is if a side by side comparison of bare copper + eutectic, silvered copper + eutectic, copper + silver bearing 2% eutetic solder, the silvered copper performance is worse then the silver 2% alloy done on bare copper (due to it not being homogenious).Is there any procedure to follow, like heating the joint for longer then usual for normal soldering, so there is more time for mixing to occur? (this would normally be bad). Would also be a consideration for other platings too.. I figure they are usually so thin that the time constants of soldering are more then enough and their modification would lead to gross hazards for the chips with little benefit to homogenity (the solubility rates of copper and silver are similar too I imagine, so if you are diffusing more silver you are also diffusing more copper and the supply of copper is effectively endless in comparison to the silver, so you are basically letting snakes in.. for some reason I imagine you would need laser heat control and extremely thin preforms to make use of this, but that is just a hunch, and there is the brazing graph that shows there is optimal seperation thicknesses, hence mass limits that must be adhered to, so diffusion control might not be achiavable because of thermal time constants save for some very advanced heating equipment.. like depth zone heating on the order of microns).Kind of curious actually about that, I want to try to suspend a chip on a micrometer and try different elevations (not letting the solder tension do the work, i.e. fixturing) and see if it gets stronger.. (instead of industrial scale oven potato chips).