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Stainless Steel tabs in brd assemblies

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Hi all! Heres wishing everyone a Happy & Prosperous 2008!! ... - Jan 03, 2008 by fsw  


fsw

#53060

Stainless Steel tabs in brd assemblies | 3 January, 2008

Hi all! Heres wishing everyone a Happy & Prosperous 2008!!

We are a small OEM/CM that use Ni tabs in our design/applications. We have a request to use Stainless steel to reduce/eliminate the Ni content. Can Stainless steel be soldered? If yes, is our normal process adequate?

Regards

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#53062

Stainless Steel tabs in brd assemblies | 3 January, 2008

Q1: Can Stainless steel be soldered? A1: Yes, stainless steel can be soldered.

Q2: If yes, is our normal process adequate? A2: We know nothing about your normal process. Common flux used in routine soldering will not step-up to the requirements necessary to solder stainless steel. You will need BIG BOY flux to solder stainless steel. And you will need to clean the flux residues, as you'd expect.

What is the purpose of the tabs that you use on these boards?

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#53063

Stainless Steel tabs in brd assemblies | 3 January, 2008

As Dave said stainless steel can not be soldered using fluxes designed for electronics. The only way this could be done is to spot plate copper or tin where you want to make the solder connection.

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fsw

#53064

Stainless Steel tabs in brd assemblies | 3 January, 2008

Davef, thnx for your reply. Sorry, forgot to clarify "our normal soldering process". We use standard Sn/Pb & SAC305 for our non RoHS & RoHS requirements. We only have a "No Clean" process, no aqueous flux is used. Hence our flux will be mild. As suspected, we will need a paste with agressive flux. Any info on available paste will be appreciated. Meanwhile will try our local paste suppliers for feedback.

Tabs are used for battery connections.

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fsw

#53065

Stainless Steel tabs in brd assemblies | 3 January, 2008

Patrick, thnx for your info. The tabs will be soldered on a PCB pad just like an SMT component. Will let all know once I have some more info.

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#53066

Stainless Steel tabs in brd assemblies | 3 January, 2008

Stainless steel can NOT be soldered with the solder that is used in electronics, be it Sn63 or SAC305.

I have 1st hand experience in this. Solder will NOT wet to it no matter how much flux is applied, or what type of flux is applied. Again, I have hands-on experience with this.

Now, there are other types of steel that CAN be solder - for example, plain old Tool Steel.

If anyone can successfully solder stainless, please let me know.

(on a side note, solder not adhering to stainless is actually a good thing. My wedding ring is made of stainless. :-) )

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#53067

Stainless Steel tabs in brd assemblies | 3 January, 2008

Recommended procedure for soldering stainless steel [Atlas Steels Australia]: * Surfaces must be clean and free of oxidation. * A rough surface improves adherence of the solder, so roughening with grinding wheel, file or coarse abrasive paper is recommended. * Use a phosphoric acid based flux. Hydrochloric acid based fluxes require neutralising after soldering as any remnant traces will be highly corrosive to the steel. Hydrochloric acid based fluxes are not recommended for soldering of stainless steels. * Flux should be applied with a brush, to only the area being soldered. * A large, hot iron is recommended. Use the same temperature as for carbon steel, but a longer time will be required because of stainless steel's low thermal conductivity. * Any type of solder can be used, but at least 50% tin is recommended. Solder with 60-70% tin and 30-40% lead has a better colour match and greater strength.

Be aware that phosphoric acid is nasty. It will kill the canary.

Separately, "Soldering Handbook" [American Welding Society, 3rd e, 3.3.4, p.224] discusses soldering stainless steel, including Table 3-10, which lists specific inorganic flux formulations for specific stainless steel alloys. One of the flux formulations in Table 3-10 is eerily simlar to Jesse's Super Flux [We don't know who Jesse is. We were told "Don't ask."] that we have been meaning to try. Jesse's Super Flux: * 96 gr ZnCl2 * 9.6 gr NH4Cl * 25 ml H2O * 10 ml HCl (conc.)

Obviously, Jesse's is a hydrochloric acid based flux that will require neutralizing after soldering.

So, your wedding band is not as immune as you thought. A short time after my wife and I married, I slopped mercury on my gold band. Not good. Unfortunately, I've done worse things during my 93 years of marrage. So that little episode is a distant memory.

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#53068

Stainless Steel tabs in brd assemblies | 3 January, 2008

Consider conductive epoxy. Among the suppliers that make the stuff are: * Master Bond [154 Hobart St, Hackensack, NJ 07601; 201-343-8983 F201-343-2132 http://www.masterbond.com]

* Chomerics [Parker Hannifin, 77 Dragon Ct, Woburn, MA 01801; 781-935-4850 F781-933-4318 chomailbox@parker.com http://www.chomerics.com]

* EpoTek [14 Fortune Dr, Billerica, MA 01821; 978-667-3805 F978-663-9782 http://www.epotek.com]

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#53069

Stainless Steel tabs in brd assemblies | 3 January, 2008

Why are you using stainless steel? Corrosion resistance? Can the stainless be gold plated? I think this can occur metallurgically. Maybe nickel first then gold. Why are you removing the nickel? Nickel is somewhat magnetic. Had an application once where the PCB could not contain nickel because the PCB was a compass board. I agree with Patrick. Plate the stainless with some other metal. I know this can be done.

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#53075

Stainless Steel tabs in brd assemblies | 4 January, 2008

So, I'd have to grind the living sh#t out of my wedding ring, and then use phosphoric acid based flux that can kill a small animal in order to solder stainless steel.

Cool!

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fsw

#53078

Stainless Steel tabs in brd assemblies | 4 January, 2008

All,

The reason SS (stainless steel) was being considered is - customer wnats to reduce Ni or basically eliminate it. Anyway, seems that soldering SS for electronics is not going to be an easy option. Suggestions for different plating has been forwarded.

Thnx to all for inputs!

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#53079

Stainless Steel tabs in brd assemblies | 4 January, 2008

Good move. Again, stainless can NOT be soldered with standard materials used in electronic manufacturing, as everyone agrees in this thread.

Additionally, the physical properties of stainless have to be altered in order for soldering to take place.

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RDR

#53096

Stainless Steel tabs in brd assemblies | 7 January, 2008

they make tin plated steel batt contacts. may be your best option

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#53097

Stainless Steel tabs in brd assemblies | 7 January, 2008

Another thing I'm curious about. What is the "functional purpose" of soldering stainless? Solder coatings generally prevent oxidation on surfaces, but why would somebody solder STAINLESS?

Stainless, by nature, is resistant to rust, and hence, oxidation processes. To quote Wikipedia: "Stainless steel forms a passivation layer of chromium(III) oxide."

As for my situation, we tried using it for a selective soldering nozzle. The nozzle needs to be solder-coated for solder to flow nicely on it.

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#53100

Stainless Steel tabs in brd assemblies | 7 January, 2008

All must be cautioned when messing with acids. Of course, neutralization is required. ("ADD ACID TO WATER", says the wise mans daughter). But at what cost to do the job right? Theoretically, anythings possible. Have messed with acids for soldering and other steel industry applications. Nasty stuff if you don't use proper precautions. Secondly, the neutralization (water) can make the job worse if running no clean and no DI source. But if it's a battery bank (buncha D cells), like what the original poster mentioned, prolly good ol' baking soda and water with a clean water flush will work, followed by die-electric grease to prevent oxides forming (ya ya , it's stainless steel, but what is it soldered to?)

Finally- being an ol' pick and file guy (GM) I used to work with tin-lead for body dents on the cars. Ends up- inhaled enuff lead dust, it got in my blood, it has all centered in my seat and feet. Don't know whats worse- mercury poisoning on ring finger or lead foot.

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#53102

Stainless Steel tabs in brd assemblies | 7 January, 2008

might try solder-less through hole connector technology for your SS tabs- the pins are barbed and it is pressed into place.

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#53112

Stainless Steel tabs in brd assemblies | 8 January, 2008

If your wedding ring ever gets hot enough to melt solder, I sure hope your finger isn't in it at the time!

On the original question, most stainless alloys have quite a bit of Nickel in them, so going to stainless will not ELIMINATE nickel, although it may reduce it a lot.

Jon

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