Metal coating for soldering? 1

[etang858]

Hello,

I have a piece of steel that is currently coated in zinc. I need to be able to solder to this piece of metal but zinc doesn't seem to be working well.

Any suggestions on materials I can coat the steel in to make a good solder connection?

Can be an industrial coating process.

Thanks for any help or insight!

 

[itsmoked]

Absolutely. Copper plate it.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[racookpe1978]

Need to remove the galvanizing completely before copper-plating though.

What is the purpose of the soldered-on part? Electrical grounding or power connection or instrumentation? Surely not fabrication or strength?

 

[racookpe1978]

Also: "Solder" is translated as welding in spanish, some other languages. What exact temperature and brazing/soldering/welding method do you want to use?

 

[etang858]

itsmoked- will try, thanks

racookpe1978- I have a slot in a PCB which I push the metal through. I then solder the metal (kinda encase the metal) to the board in order to get connectivity from the board to the other end of the metal. It serves as a mechanical hold, not ideal. Signal is then read from the metal back to the PCBA. I know there are better ways to do this, but its a legacy design and I'm confined to this. Just need the solder to stick to the steel which is currently zinc coated.

Thanks for any more insight and feedback!

 

[itsmoked]

Oh now you say... Another would be gold plating. They have gold plating processes where they just dip the plate-e in a solution.

Consider using copper instead of steel and pushing that into the board.
Consider cheap batch plating them gold then pressing them in.
Tin plate then push-in.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Compositepro]

Soldering of galvanized sheet metal is done all the time. Perhaps you are using the wrong flux or solder.

 

[itsmoked]

Good point but..... that's using acid core solder, a huge no-no in electrical applications.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[VEBill]

Does it have to be one step?

They could pre-tin the metal item (or part of it) using acid core solder, then clean it.

Then, the pre-tinned item might subsequently be more-easily soldered onto the PCB (using normal flux solder).

This pre-tinning would also help with the item's thermal mass and excess temperature-duration aspect of trying to solder larger items onto delicate PCBs. Because pre-tinning speeds up the later soldering.

 

[waross]

That was my thought also Victor-Echo. lps

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[etang858]

VE1BLL, WAROSS-

Do you mean push the metal through the PCBA, use acid core solder to make the connection, then clean off the surrounding area to remove the acid core solder from eating away any other electronic components?
If so, what would I use to clean?
I'm naive when it comes to soldering. I'm not the one doing the actual soldering, just need to find the solutions.

Thanks for everyone's help and insight.

 

[waross]

NO! Clean and tin the part with acid flux away from the circuit board. Once it is tinned and cleaned, insert it into the circuit board and solder it in place with rosin flux.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[etang858]

Waross-
Thanks for that. Unfortunately the opening for the piece of metal is very tight to the actual part so manual tinning prior to inserting will not fit without precise control. Currently it is done by hand.

All-
I've also done some reading about tin plating. There seems to be shelf life on the solder-ability of tin plating. I know it varies based on thickness, substrate, etc, but does anyone know if the shelf-life is on the order of years or are we talking months when exposed to ambient air (not in a Nitrogen filled bag).

Thanks

 

[VEBill]

"...about tin plating..."

Tinning is not tin plating.

'Tinning' in this context means applying solder (correctly, so it's bonded properly), and then removing almost all of it leaving as thin a layer as you want.

In the amateur/hobbyist world, removal of the excess solder might be accomplished by flicking the still-hot part onto a hard surface. The still molten solder would fly off, leaving the thinnest possible layer. You wouldn't use such an approach in industry, where there's QA etc. This extreme example is just to ensure you understand what's being described here.

 

[etang858]

Hi VE1BLL,

I'm thinking of something along these lines:

https://advancedplatingtech.com/electrolytic-plating/tin-plating-services/

Thanks

 

[etang858]

Hi All,

I was looking at the surface finish of the piece of zinc coated metal. I have one piece with a matte finish which solders fine, but the one with a more polished finish is the one which started this thread. Matte = solders OK, polished = solder does not stick as well.

I did a quick test and used low grit sand paper to abrade the polished surface. I then heated the surface and applied solder. The polished surface created a more bulbous solder ball while the sanded surface looked spread out more- better wetting. I think my issue may not be the zinc itself but an actual surface finish issue. I think the matte surface has more surface roughness therefore is better for soldering.

Matte finish on the left, polished on the right

Thoughts?

 

[etang858]

Hi all,

I looked into conductive epoxy and yes, its way too pricey for our application. Cleaning of the parts to expose the steel to make it solderable is too time consuming.

We are ready to just make a fresh run of parts with the proper plating. I've looked into tin plating and there is a shelf life due to oxidation of the surface and growing inter-metallics. We are not yet sure on how fast these parts will move so the shelf life concerns me a bit. I know we can ship them in nitrogen bags to slow this and keep parts in a temperature controlled room.

Do you all know of any other plating (over a stamped steel piece) that will promote wetting and solderability without the shelf life concerns? A shelf life of 2-3 years should be fine. Storage temperature will be ~20C.

Thanks!