How to make Solder Paste?

[Mosaic]

Hi all:

I am considering making my own solder paste, but I don't have a source of powdered Tin/Cu/or Sn.

I was thinking of somehow grinding solder wire into powder.

Solder wire is quite ductile/malleable and may not 'grind' easily so b4 I make a mess I was hoping for suggestions.

I need to do this as I am outside the USA and the commercial stuff is not stocked at all here. Doing a little batch from time to time seems to be a good way to keep fresh material on hand.

 

[#12]

I've never done this, but I have the idea that you are going to have to file the solder with a hand file. A grinder will make too much heat, as in vaporize some of the flux, cause clumps to partially melt together, and spew the particles all over the place.

 

[jbeng]

It's not just a matter of mixing the dry tin and lead powders together... The metals in solder paste are already alloyed and formed into microscopic spheres which are then suspended in flux. Just buy some from DigiKey and save yourself a load of headaches.

Solder Paste | Digi-Key

 

[etofans]

Hi, I would help but sorry that I haven't had the experience, I think you'd better just buy from store to save time.

 

[Mosaic]

There's a pressing reason to make it....and that is shelf life. I can't stock small quantities repeatedly because of shipping out of the US and large quantities won't last.
I do note that a solder sucker turns solder into powder when sucking it up....that might be a possibility.

 

[3v0]

I do not think the shelf life is limited as indicated. Maybe it takes a bit longer to melt or some other property changes. A big problem for a fab outfit but not so much with a fry pan or a heat gun.

Mine is over 2 years old and it still works with stencils. I think it was at date when the vendor tossed it in with the hot air setup I purchased.

I am thinking to make the little solder blobs you might spray hot solder under pressure into a moving stream of air. Very fine spray tip.

Not sure if this is any help but it is interesting. Solder paste at 200X magnification.
**broken link removed**

 

[Mosaic]

A molten solder atomiser then? The reverse of a solder sucker effect?

 

[3v0]

A molten solder atomiser then? The reverse of a solder sucker effect?

That is my best guess for how they would make the beads. The problem is you have a number of variables, solder temperature, air temperature, air speed, jet/orifice size, pressure on the solder.

Found an article on making shot Shot tower - Wikipedia, the free encyclopedia. According to it wind towers have replaced shot towers. And the good news is that the tiny drops of solder will cool fast making the process easier.

 

[Mosaic]

Success!!

Ok folks...100% success.

Simpler than it seemed.

Steps as follows:

1) Melt some solder in a spoon....u can do it on the stove if u like. I have a propane torch so i used that. Perhaps 2 grams or so. About as much metal as in a quarter.
U can recycle the solder beads/lumps obtained when tinning your iron.
You want a flattish roundish piece when done, that's easy to hold in a bird beak pliers. Don't worry if there's a bit of dark surface oxide on the solder piece.

Time: 5-10 min:

2) File that cast solder piece down (flat iron file) into a clean container, preferably a white one so u can see the powder. I do this manually with an ordinary flat iron file, holding the piece in a bird beak pliers so as not to file my fingers.

Time: 15 min or so.

3) Mix in rosin flux gel...1 part rosin gel to 3 parts powder by volume works for me.
Gets like gray/silver toothpaste. If lumpy u need more flux gel, work it smooth.
Makes a bit more than 1 cc of solder paste. Good for perhaps 200+ smd joints.

Time: < 5 min.

4) Place paste in a tiny resealable container or wrap tight in some aluminum foil, or pack in a 5 cc syringe, like the ones that carry the thermal paste.

Summary:

So 30 mins gives enough paste to do a whole board saving me at least 2 hours of arduous smd wire-soldering work pin by pin. That's 1.5hrs saved, subtract another 15 min for placing parts & solder paste stenciling. Still 1.25hrs saved per board.

Plus no solder wasted and better fillets all around, with no heat damage to components or traces.

 

[3v0]

Way cool and you did not have to build anything !

 

[#12]

Glad to know I guessed right. Just file a blob of solder into particles and add flux. It saves shipping costs and the time it takes for the parcel to arrive. Very convenient because most of us have some add-on flux and the floor around the work bench is splattered with solder blobs.

 

[Mr RB]

You could use a Dremel rotary tool with a burr bit, it would make a pretty consistent size powder and be a lot quicker than a file.

 

[RMMM]

As long as you dremel'ed in an enclosed area, you wouldn't have to wipe the solder off the ceiling..and your face and etc.

Mosaic, How was the solderability? Tack and melt? Everything ok?

 

[Jon Chandler]

I'm surprised nobody has mentioned the health risks here! At least wear a dust mask, and wash your clothes and especially your hands and face when done.

 

[Mr RB]

As long as you dremel'ed in an enclosed area, you wouldn't have to wipe the solder off the ceiling..and your face and etc.

I'm guessing you don't Dremel metals much.

The high mass of the material means it throws off in a single direction, you could just do it over a bucket. However I would still wear goggles and face mask, and yes I should definitely have included that in the suggestion.

 

[AtomSoft]

OMG THANKS.. i will try this ASAP today perhaps!!! I have all the tools! Can i use the file from a nail clipper?

UPDATE:
Just tried it but no luck so far. I guess practice makes perfect. Im not measuring, im eyeing it so maybe just have to adjust my eyes heh. Ill try again tomorrow.

 

[Mosaic]

I don't think a nail clipper file will work. Not coarse enough. Don't use sandpaper, masonry block or Dremel grinding stones.... u just adding sand to the metal filings.
I don't do this with lead based solder. I'd want a full face mask and have to bathe after etc...lead powder ain't fun.

I did some basic solderability tests on aluminium foil to check the beading...it's ok, decent coalescing.

My mix has about a 25% flux content...which is a bit high...but u get excellent tack and wettability for lead free.
I get smooth silver looking fillets....not as crusty as with wire solder.

I am using my DIY HOT air pencil.
https://www.electro-tech-online.com/threads/diy-hot-air-pencil-8-easy-steps.113697/


Edit...
I used a dremel Burr bit and it makes quick work of the grinding, although the filings are not as fine as hand filing. Did some manual work with it...slapped on a bridging blob over both 805 pads. Melted with the Hot air...it coalesced nicely on both pads...no bridging. Rested the 805 part with a tweezerr and reflowed...perfect. Desoldered and reflowed the same part 4 times...no problem ..no damage to part or traces!

I added the fresh powder to the existing mix to up the metal content to about 85% as per a standard solder paste mix. Not as tacky as before though, I figure it would work for manual use here but not so well for stencil.

BTW RB, I really liked your 'black' page, there are several useful projects there I'd like to try. Would any magnetic sounder work with your 1 bit audio encoder? To play xmas music perhaps?

 

[Mr RB]

Re the Dremel burr, you can get these in different coarseness, I bought a pack of 1/8" shank burrs for about $15 (not Dremel brand) and there are 10 sizes and shapes, they look like little files but rotary of course. A fine tooth burr would give good fine metal dust, based on my experience cutting aluminium with them.

Thanks for the nice words about my web page.

I'm not sure what you mean by "magnetic sounder" but any magnetic speaker can be driven with 1bit sound, provided you don't need top sound quality. It is for minimal speech systems that need to work from a small PIC etc where sound quality is not the most important factor. Things like a talking remote control using just one PIC.

If you need good sound quality then you are best putting 8bit sound on a SD card and playing that back with a DAC and a small amplifier like a LM386.

 

[AtomSoft]

This is my second try:

THIS IS SO AWESOME!!! THANKS AGAIN!

TQFP here i come! lol

Tools used:

I used RadioShack since i used to work there i have friends that let me use there discount.

 

[RMMM]

If you want to do this regularly, get bar solder. The type used for solder pots.

It will be MUCH easier to file then wire solder, and its much cheaper.