liquid tinner finish with pcb question

[FUZZZZzzzz]

I've watched some etching tutorials and started to make my own pcbs. Everything turns out real nice so nothing to complain about, but I saw one video where a guy puts his pcb in a bath of liquid tinner as a last step for anti corrosion and such.. Do you guys do this as well.. i had never seen it before,but it looked nice and makes sense I guess.

[karbomusic]

It looks cool that's for sure. Here is my personal take on it as someone who etches their own PCBs; I usually do one of the following:

1. Don't use liquid tin and instead spray a very thin coat of lacquer over the clean copper before soldering. The iron burns right through it and it keeps the copper from tarnishing.

2. Use liquid tin which solves the tarnishing issue and allows easy soldering. In this case, I'm still going to add a thin layer of lacquer post soldering.

In the first case, part of the lacquer's function is to keep the copper shiny and untarnished. In both cases the lacquer layer is there to prevent unintentional shorts such as some tiny metallic foreign material landing on the PCB (I often use a ground plane). AKA a sort of poor man's solder mask. I don't have a huge preference over either other than sometimes the tinning is just an extra step but again, it has it's place and like I said, looks really cool.

[amptramp]

We used to buy in printed circuit boards that were "solder-plated" rather than tinned.  Our experience was that if the plating was bright and shiny, solderability would be a problem but if it was dull and grey like solder then it would work perfectly.  If you manufacture the board then populate it immediately there would be no problem soldering directly to the copper.  If you are going to leave the board unused for a while, tinning may be a better idea.  I would be careful of lacquer - it should work but it may interfere with the flux and may make the connections look messy and difficult to inspect.

[karbomusic]

I would be careful of lacquer - it should work but it may interfere with the flux and may make the connections look messy and difficult to inspect.

It actually works incredibly well. I had the same fear until I began doing it but it doesn't look messy or cause any issues I can find. Obviously, I wouldn't coat it like I was finishing an enclosure, just a very thin single coat that typically dries within a couple of minutes.

[dschwartz]

What kind of laquer you use for that? Enamel, poly?

[karbomusic]

What kind of laquer you use for that? Enamel, poly?

Usually enamel if I remember correctly. I can check for sure once I'm back home. I spray them downstairs in the garage, by the time I walk upstairs to the bench, they are already dry enough to handle and solder. Here are two with the lacquer just after drilling...

[davent]

i do the lacquer as well and have a bottle of Liquid Tin, the lacquer works far better then the liquid tin. Left for any lenght of time, say populate the board set aside, it sits, it oxidizes and those pads left unsoldered are a royal pain to get solder up.

A light mist coat of lacquer, i've used solvent and waterborne whatever lacquer i'm using for finishing, boards have sat for a couple years and solder up no problem. Lacquer flashes off with the touch of the hot iron and solder flows, easy!

Testors has some candy transparent lacquers that give you a pseudo soldermask in look at least.



Last ever toner transfer attempt, photoresist all the way.




dave

[FUZZZZzzzz]

great stuff guys, thanks!

I've finally etched my first board yesterday and was very pleased with the result. I always felt like pcbs were a little bit like cheating (you know painting by numbers), but after a decade of vero board it's very appealing. Especially if you design everything yourself as well.

[CodeMonk]

I use this stuff:
http://www.mgchemicals.com/products/prototyping-and-circuit-repair/prototyping/liquid-tin-421/
You can find it on Amazon.
It only takes a few minutes for it to work.
Its kind of a dull finish though.
I dunno, maybe if I were to buff the copper before using the liquid tin? (just thinking out loud to myself there).

[anotherjim]

PCB lacquer is polyurethane I always thought. I've used it with success. That said, that was with 60:40 lead based solder. Higher temperature solder might be an issue with the lacquer burning? Burnt lacquer could be conductive or attract moisture?