PCB Electroless Tin Plating

This is the first is a series of Instructables aimed at documenting all the electronics-related activities that go on at So Make It; Southampton Makerspace (on the South coast, UK) Requests are more than welcome!

On eBay and other on-line sources, you can buy these little twin-packs of tin plating chemicals. I bought some to play with and thought I'd start writing up some instructions on methods to use it.

Step 1: Study the Instructions

Thiourea is apparently quite nasty, so keep this stuff away from food, children and animals.

Don't eat it.

Step 2: Mix the Solution

Add part A into the appropriate amount of distilled water (in my case 250ml.) You can get this from a variety of home and DIY stores, also it used to be used in older 'wet' car batteries, so you could probably get some from a car shop.

Shake it up a bit to get it to dissolve.

Repeat for part B, shaking it around a bit over the course of a couple of hours until there are no undissolved granules. It will have a weird reddish tinge but be completely clear when read for use.

Step 3: Prepare Your PCB

Cleanliness is important when processing PCBs. However, for DIY use, no need to panic. Just clean off the photo resist on the board (you did resist cleaning it off after etching right?) with a little acetone, or gently scrub it off with some steel wool. Careful to get the really fine grade stuff, so as not to make deep scratches in the soft copper surface. You should be able to get the copper to be quite shiny and oxide free.

Clean off any residue in hot water.

You can make a really shiny, polished surface using 'Brasso' copper/brass polish (available in pretty much any household shop in the UK) just place a little onto a cloth, buff the board gently with circular motions, then buff off with another clean cloth and finally rinse in hot water. You don't want any residue contaminating the board!

This will result in almost a mirror finish, however you will clearly see the fiber weave of the PCB substrate material as a pattern in the shininess of the copper. It won't get any better than that. (no I couldn't get my camera to take a shot of that!) As soon a you have a shiny, residue free (don't worry about drying it, just shake off any water) PCB, progress straight to the final plating stage without delay!

Step 4: Immerse in Plating Solution

Simply stick the PCB in a CLEAN photographic tray (or some other tray, ideally with a pouring spout like this one) and pour over the plating solution, so the board is covered fully. Swish it back a forth a little. You will see an instant reaction (with a fresh solution) so don't hang around! Leave it for between 30 seconds and 2 minutes to get a nice flat even layer of tin. The longer you leave it, the thicker it will be, BUT also the faster your will exhaust your plating solution.

Finally, pour the solution back into your container and wash the PCB with some clean water and leave to dry.

Step 5: Final Thoughts

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    12 Discussions


    Question 8 months ago

    I want to do this with copper pipes know it will work since it copper but I can find Thiourea dioxide which 500 g cost 40 dollars CAN and Thiourea alone is 70-80 dollars alone for 30 g.

    Would thiourea dioxide work instead?

    Thiourea dioxide + water >>>>> Thiourea + Hydrogen peroxide.

    Tin (II) chloride plus H202 should give Tin (IV) chloride and tin hydrooxychloride.

    6 SnCl2 (aq) + O2 (g) + 2 H2O (l) → 2 SnCl4 (aq) + 4 Sn(OH)Cl (s).

    However in excess Hydrochloric acid oxygen from the Hydrogen peroxide and some chlorine gas will be emitted. 2HCl + H202 >>> 2H20 + Cl2.

    I am not entirely sure but would chlorine negatively effect the plating due to its reactivity?

    Most likely tin chloride (IV) would reverse back to tin (II) chloride and have little effect.

    parman josan

    1 year ago


    Will you please tell me the thickness of Tin layer after plating it on the copper layer and if we want to increase the thickness of it what should i do ?


    Reply 2 years ago

    This seems to be a product that is only available in the UK? At any rate, if you have a good digital scale you can mix a similar (possibly identical) solution at home.

    to 100ml of distilled water add 0.5g of stannous chloride, 2g of thiourea, and 3g of sulfamic acid.

    I recently purchased 1oz of stannous chloride, 2oz of thiourea, and 3oz of sulfamic acid from a single vendor on ebay for less than $30 shipped. Far cheaper, in the long run, than the pre-mixed stuff. Enough to mix up several litres. But the shelf life is not too good, so it makes more sense to make it a little at a time.

    None of these chemicals are controlled in the USA but it should be noted that thiourea is a bit toxic. Acute toxicity at these quantities is pretty unlikely but you should take proper precautions and familiarize yourself with the safety data sheet all the same.

    My chemist friend advises me that the thiourea and sulfamic acid will slowly react with each other even while dry if mixed. They will also slowly oxidize over time. For long term storage he recommended keeping each chemical in the original container, inside a zippered baggie with an oxygen absorber, inside a pint paint can.


    3 years ago

    I think I will be able to Tin plate my copper plated 3D parts with this right? if the copper has a mirror shine the Tin plate will also have a mirror shine right? oh and where can I get the tinning prodcut

    2 replies

    Reply 3 years ago

    Sure, the chemistry doesn't care where the copper is! Try it!
    I bought it on ebay, although it was back in 2014, and no longer seems available. Try this search


    You can also use 'senco tin plating' solution, but you'll need to google for it. It won't be cheap.


    I've read something like six months. Keep it cool? Or perhaps just mix up half the quantity and store the remainder for a fresh batch later...time will tell.


    I suspect it is based upon Stannous Chloride and Thiourea, but I have little evidence of such (other a bunch of googling and reading around) and chemistry lessons are a dim memory...It's either oxidation, or thermal decomposition at a guess. Or both...


    3 years ago on Introduction

    This looks so cool! Thanks for sharing. I may need to try this sometime!