Tin verses SS 4

[itsmoked]

I need to put a bunch of springs up against tin soldered pads. Stainless is being pushed in this regard. You guys see any issue with this? I suspect it won't be a problem.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[unclesyd]

I can't see any real issues with this arrangement as presented. We had some springs on some contact arms that were in contact with Sn-Pb solder and ran for years with no problem.

Here are two minor concerns.

One problem that I envision is that the springs will move a little metal in the landing area.

If this is pure tin there is a small possibility that the tin will oxidize a little in the contact area.

 

[EdStainless]

The tin will creep under load, that is the springs will impress into them. there should not be adverse interaction between the two metals.

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Plymouth Tube

 

[itsmoked]

These will be static and the pressure won't be very high.

Thanks much!

Keith Cress
kcress -

http://www.flaminsystems.com

 

[IRstuff]

Used to be used a lot for battery connections to PCBs

TTFN

FAQ731-376

 

[desertfox]

Hi itsmoked

Check out this bi-metallic corrosion table its suggests you might have a corrosion problem if there is any electrolyte substance present.

http://www.roymech.co.uk/Useful_Tables/Corrosion/Cor_bi_met.html

desertfox

 

[itsmoked]

IR that's a god point. I suspect that those Battery Springs were generally something else and plated but I'm not sure.

fox; Thanks for that table. It does show some reason for concern... dang! These joints could have some high humidity associated with them occasionally. Perhaps I need to consider nickle plated springs.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[desertfox]

Hi itsmoked

A possible alternative to plating the springs, would be to introduce an end cap over the spring that eliminates the possible corrosion problem between the stainless and tin.
Although this might cost more than plating, just something to consider.

desertfox

 

[EdStainless]

Your moisture would have to be fairly conductive in order to get galvanic corrosion issues.
If you are concerned a small plastic shim between the two might be less trouble than platting.

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Plymouth Tube

 

[itsmoked]

The spring has to electrically connect to the tin pad. This is for a touch keyboard.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[EdStainless]

I wouldn't worry about it.

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Plymouth Tube

 

[itsmoked]

I'm there!

Keith Cress
kcress -

http://www.flaminsystems.com