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Tinning With Solder Paste and Flux Gel

Tinning With Solder Paste and Flux Gel

2013-09-29 by James

I've always found tinning to be one of those things I could never get 
the hang of the "traditional" way using solderwick.

Today I tried something which actually worked remarkably well and very 
easy, solder paste and flux gel.

I mixed very small amount (a small blob on the end of a toothpick) of 
solderpaste with probably  3 or 4 times the amount of a gel type flux 
(Amtech type stuff from a syringe) until it was an even colour quite a 
lot lighter than the original solder paste.  Then I simply spread this 
"weak" solder paste mixture over the (small) board, not too carefully, 
with a toothpick.

Turned my handy clothes iron to it's hottest setting, flipped it upside 
down, and sat the board on it.

The flux liquified immediately, and a minute or two later the solder 
reflowed really nicely, a very thin shiny and reasonably even coating.  
A couple of areas looked like they needed a bit more so I just touched 
it with the toothpick that had some of the mixture on it and it 
instantly wicked out and gave a better coat.  I was surprised just how 
well the solder coated from such a thin mixture (thinly and unevenly 
applied at that).  Admittedly this was on a ("from the failure drawer" - 
the etch had too many problems) board which had a ground fill so there 
was quite a bit of copper to "soak up" the solder.

Slide the board off, let it cool a bit, then wipe down with methylated 
spirits to clean off the flux residue.

Naturally this won't work well with double sided boards, but a hot air 
gun might do the trick in that case (I guess that'd make it something 
like DIY HASL :))

The solder paste ("Best" in a "50g" jar, which weighed 26g when it 
arrived) and flux (M-223, typical 10cc syringe) were both just cheap 
ebay stuff.

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