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How to make DIY Solder Paste for tinning PCBs at home

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I was looking for a solution for pre-tinning my DIY PCB boards. One way to do this is by reflowing solder paste. Another very cool use is repairing brass instruments - like trumpets, trombones and tubas, because all you need to do is heat up a joint with the paste in place and it magically bonds at the right temperature.

If you go on EBay and search for solder paste - the pro stuff costs an arm and a leg for small amounts, so I was wondering if it is possible to make entry grade solder paste at home. After looking at several forums, I found a forum conversation in which someone used shavings from a filed block of solder mixed with solder flux to create paste, and reported it as success. I decided to recreate this, and in the process discovered that it is much easier than i thought. And the bonus is that working with the pre-tinned pcbs is so much easier, soldering times are now significantly reduced. 

WARNING: THIS PROJECT INVOLVES FILING SOLDER - WHICH IS AT LEAST 40% LEAD. WORK IN WELL VENTILATED AREA AND WEAR A FACE MASK AND GLOVES. ALSO MAKE SURE LEAD DOES NOT END UP IN FOOD. 
Also read this: http://en.wikipedia.org/wiki/Lead_poisoning

What you will need:
1)  Solid Solder - 50-50 or 60-40. You can use solder that has flux in it - as long at it is NOT acid based flux which will corrode your components
2) A medium to fine file - the finer the file - more work but better quality paste
3) Solder Flux - also called "solder paste" but do not confuse this with real solder paste. Make sure it is not acid based for intended for soldering! Radio shack sell some of this stuff. 
4) a toaster oven, fire, or oven. 

This instructable has 12 steps.



 
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Snorkman6 months ago

Thank you very much! This tutorial saved me a few bucks :)

Drake4111 year ago
I wonder if anyone has tried to do this in a ball mill? Skip the first remelt and throw the chunks into a rock tumbler with some good steel bolts. Do you think that would work?
dflam (author)  Drake4116 months ago

Ok tested it in (now defunct) coffee grinder. Thinking blender. Also make sure you use the shredded pieces and not chunks of solder, or the spindle will jam.

dflam (author)  Drake4117 months ago

I think perhaps a small 12 coffee grinder might work better. Just need to be careful it doesnt overheat the solder into the meting point....

Drake411 dflam6 months ago

Nice experiment and thanks for posting this. I have a small collection of soft gray metal but still haven't done a single trial.

phisitja7 months ago

thank you very much.

dflam (author) 7 months ago

Just as an addendum: Indeed - well ventilated area and wear a mask... lead is poison.

I use the final paste also as a quick dip for coating the tip of my soldering iron.

nedry11 months ago

I would like to advise people to not do this. Lead is a potent neurotoxin and accumulates in the body. It only takes 500 ug of lead (assuming 5 liters of blood) to get you to the threshold for lead poisoning. At a density of 11.34 g/cm^3, that is very little dust and you could easily be exposed to that amount through cross contamination of tools and surfaces or poor technique. The risk of exposure when you are grinding lead into dust is much higher than the risk when soldering. In solder the lead is bound in a metal and is not available for ingestion. The lead oxide on a soldering sponge and solder paste require more caution but are still not as dangerous as the powdered lead in these procedures.

The money you save by making your own solder paste is just not worth the risk of brain damage. Don't do it.

Or, to minimize the risk of aerosolizing and subsequently breathing in the solder:

place
the file under water and, while wearing gloves, run the solder across
the file. Drain the water, collect the filings, and in a draft-free
space, let the particles dry. Once dry, mix the filings INTO the flux
(to minimize agitating the filings into the air).

Yes, this method
is more time consuming, but it virtually (IMHO) eliminates any health
exposure, Until you forget to look before crossing the street and get
run down by the motorist engaged in a text exchange.

burhanmz1 year ago
@masterpj I faced the same problem and I tried with a 95/5 (lead free) and 80/20 leaded.
I was going to try it with 60/40 as its got a smaller plastic range, but seeing your post I think best option would be to go for 63/37 as it has no plastic range at all and solder melts exactly at 191degree Celsius. Though I do still think that I'll have to make my own flux (with 80~85% Rosin powder with 20~15% isopropyl alcohol by weight) the market version is made for the newer solders (95/5) usually.
masterpj2 years ago
I tried this.
But the solder didn't melt.
The flux did flow though!
I even cranked up my hot air station to the max, the solder still didn't melt or attach to the board. (only a reallllllllllllly tiny bit did).
It's 60/40 solder.

The flux is a rosin paste (the fake amtech one found on ebay)
What might I be doing wrong?
AtomRat2 years ago
Are there any issues with tracks accidently joining to one another with small melted 'bridges' ? I have been trying to find some solution to this for ages, thanks!
I use a $10 electric griddle for reflow soldering. That would probably work quite nicely. You can pick them up for next to nothing at thrift stores sometimes.
AWESOME !! I had just bought some expensive solder paste but now when that finishes i will be making my own paste !!!


Thanks a Million dflam !!!

Also @ dustinandrews;

DUDE !

Please could you email me a picture or a few pictures of your $10 griddle for reflow soldering as i REALLY want to get into that without paying THOUSANDS for the BIG HEAVY machinery or Desktop reflow station with a HUGE price tag !!

Really need to see how youve hacked together this griddle, ohh please please please take some juicy pictures and even a few of it in action lol !!

Many thanks in advance & Again @ dflam - Best-idea-Since-SLICED-BREAD !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
You can see picture of my griddle here on my reflow based Instructable. It's not hacked in any way.  This one from Target is pretty similar to the one I have. I got mine on sale at Fred Meyer for about half the price though.

I just crank it up to about 375 and set the boards on it. Here is a video of it in "action".
dflam (author)  dustinandrews2 years ago
Great - will probably try it out!
uberchoob2 years ago
awesome idea bro. I'll be using this alot!
David972 years ago
This is a great idea.
Neat. I added this to one of the steps in my Toner Transfer Instructable.