Have you ever wanted to reflow surface mount circuits but not wanted to pay for expensive solder paste?
Have you ever had a good de-soldering sesion and found lots of old solder particles all over your desk and wondered what to do with it?
Well, I have an answer to both of these questions in one hit. You can make your own solderpaste!
In this instructable we are recycling old solder, and parts of old PCBs and components.
The only non-recycled part is the solder paste.
This is useful for repairs on the go, if you need to solder wires together, you put some of this paste on the joint and use a lighter to reflow.
A little warning first. The used solder you might use could contain lead, especially if its salvaged from old boards. but since you solder you probably has already accepted the risks of such exposure.
Ok, now the formalities are out of the way, here's what you need:
> Safety glasses
> An old board to desolder
> A solder sucker
> Flux paste (or soldering paste as it is sometimes called)
> A pair of abrasive sponges (or some kind of abrasives that won't leave its own dust or flake off)
> A piece of paper to catch the solder dust
> A piece of plastic or something to mix the paste on
> Something to mix the paste with (I used a blanking plate from the back of a PC and a paperclip)
> A cup of tea (I'm English so this is a must for me)
> A good soundtrack (For this instructable I listened to Billy Talent III)
The quality of the paste varies depending on how fine you can grind the solder, the quality of the paste used and the ratio between the two when mixing. This is something you will need to experiment with.
Step 1: Salvaging the Solder
For salvaging the solder it is best to use a solder sucker.
If you do not have one then all is not lost. To desolder without a sucker you can hold the board above the desk, heat up the solder joint and then hit it against the desk or hard object and the solder with splash off onto your desk.
If you do, then you can proceed with desoldering the solder joints. A tip for this part, when you re-arm the sucker, hold the tip over the piece of paper to catch what comes out.
When you are finished, tip the board on its side over the piece of paper to catch any particles that have fallen out onto the board.
When you feel you have gathered enough solder, we can move on to the next step.
Step 2: Refining the Solder Particles Into Solder Dust
Here comes a step that varies the quality.
First you should pick through the particles with the tweezer and remove anything that is not solder.
You need to pour the solder particles onto an abrasive block, and while over the top of another peice of paper, grind the particles with another abrasive block.
repeat this as much as you feel adequate, re-pouring the paricles on the abrasive block as required.
when finished grinding, it would probably be a good idea to sieve the particles through a mesh of some sort, I didn't have one at hand so I just picked through with tweezers and removed any large particles that failed to grind.
If you have a better way of grinding the solder particles into dust, I would love to hear it, any improvement on this method would be good.
when you are satisfied with the powder/dust we can move on.
Step 3: Mixing the Paste
Here is the fun part.
First we pour the solder dust onto a small pile onto the mixing pallete of your choice, I chose a lid from a tub of potato salad. I also deposited a glob of flux paste near it, I didn't glob it directly in because I didn't want the solder to get onto my brush.
The ratio of flux to solder dust is something you need to experiment with, too much flux and it you get flux running around the board during reflow (but it solders well), too little flux and the solder doesn't reflow correctly, it tends to bead up and stay as a paste.
The picture below of the newly made solder paste turned out to need a little more flux in it. once I added some more it worked great.
If you have completed all these steps, then well done, you have created a batch of solder paste!
I could stop there, but it would be rude if I didn't show it in action.
Step 4: Reflowing the Test Board
Ok, I have taken the board I used in my last instructable ( DIY PCB ) and found a nice spot to re-use the layout.
I start by dolloping solder paste onto where the legs of the components will go.
then I place the components onto the paste, and then with gentle waves of the the reflow gun the solder paster began to reflow and complete the joints. (the first attempt didn't go as well as it should, I had to mix a little more flux into the paste and try again).
Once it cooled, I cut out the section of board with my tin-snips and filed down the edges.
After it was filled down, I put it the cell, pushed the button and it lit up nicely.
I hope this is helpful to someone.
Thanks for reading.
Dont forget to check out my DIY circuit board creation instructable
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