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 Post subject: DiY Circuit Board Tinning
PostPosted: Mar Tue 31, 2020 3:35 am 
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I did this today. Spent not much over $10 tinning my circuit board. It worked like magic.

Needing more ordered parts to come in and not wanting to delay populating the board, I was looking for a solution (pun intended) to refreshen the copper traces after they've been sitting a few days. That's a hassle on a partially populated board.

OR I could tin it and not worry about refreshing it. Found this five minute video: https://www.youtube.com/watch?v=Hsw3lOnHaas&t=209s

I had some 95% tin solder on hand, just as it calls for. The acid was $4.99 and the Tarn-X was $8.59. It took just a couple of hours for the 1 gram of solder to dissolve in 10mL of acid, then the antimony was sitting at the bottom of the solution as the video shows. I poured off the solution and I added 100 mL of Tarn-X. Just like in the video it made a white precipitate. I heated it to at least 125 degrees F to get it clear.

I stuck in a piece of 14 ga copper wire and it INSTANTLY turned silver. Like magic.

Next, the circuit board (made with the toner process, so it's ragged) was put in a small leakproof picture frame. I poured in just enough solution to cover it. Within a couple seconds I had a tinned board. The flaws visible in the photo are etching flaws. The tin is even throughout.

Reminds me of Jesse Pinkman happily exclaiming to Walter White, "YEAH, SCIENCE, B----!


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 Post subject: Re: DiY Circuit Board Tinning
PostPosted: Mar Tue 31, 2020 3:50 am 
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Location: Livermore, CA
Nice procedure. Be sure acid is well washed off the PCB.

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 Post subject: Re: DiY Circuit Board Tinning
PostPosted: Mar Tue 31, 2020 5:08 am 
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Muriatic Acid can be very nasty stuff. One of it's primary uses is to clean swimming pool surfaces. Definitely wear gloves and use eye protection when working with it. Notice that the container says, "for exterior (outdoor) use only". Make sure you have adequate ventilation, preferably a breeze from an open window or a fan. Take a whiff of this stuff and you'll get my meaning.

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 Post subject: Re: DiY Circuit Board Tinning
PostPosted: Mar Tue 31, 2020 6:41 am 
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Good catches, guys. Yeppers, I worked outside. I could SEE the fumes.


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 Post subject: Re: DiY Circuit Board Tinning
PostPosted: Apr Wed 01, 2020 2:07 am 
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Location: Montreal, Quebec
Decades ago I bought some sort of circuit board tinning liquid, from Active Electronics. Seemed to work fine, I don't know what was in it. I eventually had to throw it out, the bottle leaked.


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 Post subject: Re: DiY Circuit Board Tinning
PostPosted: Apr Wed 01, 2020 2:28 am 
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Location: Norfolk, VA
mblack wrote:
Decades ago I bought some sort of circuit board tinning liquid, from Active Electronics. Seemed to work fine, I don't know what was in it. I eventually had to throw it out, the bottle leaked.


TINNIT was the brand name. No longer supplied - the two-part stuff was great, but the Thiourea (also in solution with Sulfamic Acid in the Tarn-X) is hazardous, and it was pulled. Philmore was my last source, but they too quit selling it.

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 Post subject: Re: DiY Circuit Board Tinning
PostPosted: Apr Wed 01, 2020 6:05 pm 
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Apparently this solution can be used again, which I've not tried. Note, however, that at room temperature it reverts back to a white precipitate so it will need to be heated to at least 125 degrees F to become clear liquid. I doubt Tinnit had that issue.

I expect I'll use a double boiler to heat it, as I don't want acid in my microwave and I have it stored in canning jar which may not be rated to put on the stove.


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