Author Topic: tinning PCB's (Read 17628 times)

Simon · « **on:** January 07, 2011, 07:40:45 am »

Well like many people probably do I got some of that tinning powder you mix with water and put your pcb into to tin it.

However I was thinking there might be another method. what about putting solder paste on the track of the PCB and then using a hot air gun to heat it ? would it work ? what exactly is solder paste, I work for a radiator manufacturer and they guy has a solder paste (solder + flux) that they paint onto stuff to tin it and get it ready for soldering together, same stuff maybe ?

tyblu · « **Reply #1 on:** January 07, 2011, 09:53:26 am »

I just spread solder on it with an iron. If there are too many fine tracks to do this quickly (long <20mil data buses), I just do the pads and forget the tracks. Flux right before soldering helps. I'm thinking, however, of getting into electrochemical tinning after chemical treatments in order to do my own vias. Appears to require some intense, multi-step chemical treatment to get it to stick to drill bit glass transitioned FR-4 (bit melts and smoothes holes), but it doesn't seem too bad. Anything to keep it in my garage

mikeselectricstuff · « **Reply #2 on:** January 07, 2011, 10:16:37 am »

I used to use tinning solution a long time ago but don't bother these days - the stuff is expensive and solution doesn't last long.
I just leave a coat of flux on to prevent the copper oxidising.

RayJones · « **Reply #3 on:** January 07, 2011, 10:27:30 am »

Quote from: Simon on January 07, 2011, 07:40:45 am

Well like many people probably do I got some of that tinning powder you mix with water and put your pcb into to tin it.

However I was thinking there might be another method. what about putting solder paste on the track of the PCB and then using a hot air gun to heat it ? would it work ? what exactly is solder paste, I work for a radiator manufacturer and they guy has a solder paste (solder + flux) that they paint onto stuff to tin it and get it ready for soldering together, same stuff maybe ?

Yeouch, I'm thinking that stuff would corrosive as all hell - we call it Bakers Flux - but it's used by plumbers, not technicians.

NO NO NO.

Psi · « **Reply #4 on:** January 07, 2011, 10:56:30 am »

Maybe you could get one of these http://www.dealextreme.com/details.dx/sku.48764

Fill it with solder then just spoon it onto the pcb and let it run back off into the pot?

I have no idea how well it would work though, i just noticed those solder pots on DX a few days ago.

You'd want a ceramic spoon though i think, to stop the solder sticking to it or burning you by heating up the spoon.

They happen to have the correct plug for AU/NZ which is nice. (well, nice if your in AU/NZ

)

tyblu · « **Reply #5 on:** January 07, 2011, 11:39:18 am »

Quote from: RayJones on January 07, 2011, 10:27:30 am

Yeouch, I'm thinking that stuff would corrosive as all hell - we call it Bakers Flux - but it's used by plumbers, not technicians.

There's tinning mixtures available that are meant for this: http://www.mgchemicals.com/products/421.html .

Quote from: Psi on January 07, 2011, 10:56:30 am

Maybe you could get one of these http://www.dealextreme.com/details.dx/sku.48764

Fill it with solder then just spoon it onto the pcb and let it run back off into the pot?

I would think that this wouldn't work very well without a PCB preheater to get the tracks up to temperature...

Simon · « **Reply #6 on:** January 07, 2011, 01:27:24 pm »

I had thought of the pot, maybe I could try it at work in our tinning pit

comox · « **Reply #7 on:** January 07, 2011, 01:47:58 pm »

Tinning powder isn't worth the HASL.

Get it? HASL?

Har har har!!!! Bwaahahahahahha!

But seriously folks, if your not rich like Dave and go for gold plating, go for Hot Air Solder Leveling. If your making your own, well, your on your own.

JohnS_AZ · « **Reply #8 on:** January 07, 2011, 02:54:08 pm »

Quote from: Simon on January 07, 2011, 07:40:45 am

What exactly is solder paste, I work for a radiator manufacturer and they guy has a solder paste (solder + flux) that they paint onto stuff to tin it and get it ready for soldering together, same stuff maybe ?

Plumbing (radiator) solder paste is ground up solder in a flux (often acid based flux).
Electronic solder paste is VERY precisely manufactured solder spheres suspended in a much less aggressive flux (rosin or no-clean). The point of the spheres is that they pack well and predictably into the openings in a stencil. While plumbing solder is usually simple tin-lead, solder paste can have other compounds (nickle, silver, indium) to improve wetting and performance in electronic applications.

TheDirty · « **Reply #9 on:** January 07, 2011, 03:17:28 pm »

I once used a piece of solder wick soaked in solder and dragged around the board to tin a board just because I wanted it to look nice. It worked well. Otherwise I have no use for tinning boards and haven't done it since. The boards I haven't conformal coated tarnish and darken.

Simon · « **Reply #10 on:** January 07, 2011, 03:58:00 pm »

well essentially I just want to protect the copper from oxidising, so if I just flux it that will do ?

wd5gnr · « **Reply #11 on:** January 07, 2011, 04:11:13 pm »

Instead of solder wick get the braid off some coax and use it to make a "snuggie" around your iron tiip. This will soak up solder and then you can drag it over the traces. I usually just use a conformal coating spray though. Of course, the boards that already have mask layers shouldn't be a problem.

JohnS_AZ · « **Reply #12 on:** January 07, 2011, 04:13:28 pm »

No, flux won't. But paint will.
Krylon Clear Gloss Enamel has always been my favorite. (sometimes color pigments are conductive)

Be sure to test your specific paint before coating your board.

Simon · « **Reply #13 on:** January 07, 2011, 04:18:48 pm »

yea paint is starting to sound attractive, but then will tinning help me solder SMD parts ?

mitpatterson · « **Reply #14 on:** January 07, 2011, 04:27:39 pm »

I have never used any of the solutions, normally what i do i just use a small bottle(with a needle tip that I got from mouser for flux, its just MG Chemicals Rosin Flux) and use that to cover all the traces and then just put a blob of solder on my tip and drag it around until i'm happy, normally works quite well, and normally after etching, but before "tinning" i use some scotchbright again to clean up the board and clean with IPA then flux and tin, works great for me.

In regards to the via's someone mentioned, yah, that the same as MG chemicals makes a "professionals prototyping kit" that lets your make your own PTH, but its like a 5 step chemical process(involving fermaldiahite, what they preseve anamils for science in) a lot of carsiniginas, and that's just for the Electorless parrt, then you have to electricaly plate them, its a lot of work, and 2 of the chemicals are only good for like 2 days after mixe, and then you ahve a lot of chemcilas to dispose of, but i miss PTH on home made boards, make 2 sided boards hard to do and solder though hole components, but i digress.

Simon · « **Reply #15 on:** January 07, 2011, 04:40:06 pm »

has anyone ever tried dipping the board in a solder bath ?

TheDirty · « **Reply #16 on:** January 07, 2011, 06:25:42 pm »

Yikes, like that solder dipping shown in one of the other threads?

If I don't want it to tarnish, I just spray it with a bit of conformal coating. I have the cheaper acrylic stuff rather than the nicer silicon based coating. Otherwise I haven't found any issue with tarnished boards, I just let them tarnish as long as they have all the components on them already.

Simon · « **Reply #17 on:** January 07, 2011, 06:36:04 pm »

you mean the copper won't eventually wear away when tarnished ?, I have a high current project that could do with no tin for heat dissipation

mitpatterson · « **Reply #18 on:** January 07, 2011, 07:19:18 pm »

Quote from: Simon on January 07, 2011, 06:36:04 pm

you mean the copper won't eventually wear away when tarnished ?, I have a high current project that could do with no tin for heat dissipation

Normally with most oxides they are actually, believe it or not, a protective barrier to prevent further oxidation, now i can't say it won't wear away after 100 years, but in the short term(5-10 years) i don't know why it would. because the layer on the outside actually acts to protect whats underneath from oxidizing.

Simon · « **Reply #19 on:** January 07, 2011, 07:28:58 pm »

hm yes that's what I'd think, but 35um is not a lot. I suppose i worry because i took apart a prototype we were given at work and the thin traces were falling apart but then I don't know what he had been doing with it

Zero999 · « **Reply #20 on:** January 07, 2011, 08:27:52 pm »

Use a conformal coating to prevent tarnishing. The one I use can be easily soldered through so I coat before soldering if I know I'm not doing to solder it all in one go.

RayJones · « **Reply #21 on:** January 07, 2011, 09:16:23 pm »

Quote from: tyblu on January 07, 2011, 11:39:18 am

Quote from: RayJones on January 07, 2011, 10:27:30 am
Yeouch, I'm thinking that stuff would corrosive as all hell - we call it Bakers Flux - but it's used by plumbers, not technicians.
There's tinning mixtures available that are meant for this: http://www.mgchemicals.com/products/421.html .

Sorry, I quoted too much, I was referring to the radiator solder paste.

DavidDLC · « **Reply #22 on:** January 07, 2011, 11:33:24 pm »

I use MG Liquid Tin For Copper Circuits, with very good results for me.

David.

TheDirty · « **Reply #23 on:** January 08, 2011, 06:24:21 pm »

The oldest unprotected copper PCB I have is about 6 years old I think. It's darkened but it's not noticeably corroded. The darkest ones are ones that I handle regularly.

joelby · « **Reply #24 on:** January 09, 2011, 10:50:16 pm »

I silver plate boards using Cool-Amp powder. You just tip some powder onto the board and using a damp paper towel or similar, rub until it's coated.

A bit more information here: http://www.cool-amp.com/cool_amp.html
Available in smaller, cheaper quantities from Ultrakeet.


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Author Topic: tinning PCB's (Read 17628 times)

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