Simple Trick For Solder Paste In Storage

Freezer temps do not actually freeze CA. I would not want to do that either. CA's polymerize mainly by base catalysis. Low temps reduce that risk.
John

Mosaic said:

I don't freeze em....they're in the butter compartment. I can use it anytime at that temp. 2 years running since being opened!

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So you are saying fridge then not freezer?

For smiles and giggles, I tried pushing some 42/57/x solder through a 30 AWG pointy needle. Surprisingly I could push it through with a LOT of effort. I loaded an insulin syringe from the plunger end and pushed it through. Way too much effort for a Luer friction fit, that's for sure. Remember, I do have the assortment of the blunt stuff. Not tried yet.

Refrigeration, not freezing.

Pre heating the PCB before application makes it a lot easier, esp via the toothpick approach. The flux gets tacky and grabs the PCB (leaves the toothpick) and the SMD part as well when you place it.

KeepItSimpleStupid said:

For smiles and giggles, I tried pushing some 42/57/x solder through a 30 AWG pointy needle. Surprisingly I could push it through with a LOT of effort. I loaded an insulin syringe from the plunger end and pushed it through. Way too much effort for a Luer friction fit, that's for sure. Remember, I do have the assortment of the blunt stuff. Not tried yet.

Click to expand...

Hi,

Wow that is a small diameter. Would be nice to have that work without too much effort.

Mosaic said:

Refrigeration, not freezing.

Pre heating the PCB before application makes it a lot easier, esp via the toothpick approach. The flux gets tacky and grabs the PCB (leaves the toothpick) and the SMD part as well when you place it.

Click to expand...

Hi,

That's an interesting idea because i noticed right away that the solder paste does not like to 'stick' to anything, it's more like it 'lays' there. Spreading with a toothpick is a bit strange because it's like trying to spread damp sand. It goes on rather sloppy, but it still does 'seek' out the metal pins and pads when it is heated with the hot air. It's like a bunch of silver worms that are seeking a hiding place so they quickly migrate to the pins and PCB pads.

If the stuff was warm i bet it would stick. I tried sticking it to the bottom of the IC pins one time, because that would put just the right amount right on the bottom of the pins so that when the IC chip was placed on the board the paste would be between the pins and the PCB pads. But that did not work because the small pins would not grab any of the paste. The paste did touch the pins, but did not stick. If the paste was more fluid i bet this would work nicely because then there would be no paste between pins already as it would all be just on the bottom of the pins where it really does the most good.

Ideally my idea was to spread a small portion of paste onto a flat surface, then place the IC chip on the thin layer of paste which would presumably pick up some of the paste onto the bottom of the IC pins. But alas, that did not work as above because the paste does not stick to anything very well, like say super glue or any other glue might. Maybe mix it with more flux? I'd have to try it. I guess it is not too bad though spreading it with the toothpick, it just takes a little practice to get the right (sparingly applied) amount.

Mosaic said:

Well I've done that, and it works fine. But you have to make a powder via filing a solder oval made by remelting solder [from a desoldering pump] in a s/s teaspoon over the stove top. But lead powder spreading around your work area ain't a great thing. Do it outside and wear gloves.
It is good for the environment though, significant reduction in lead waste generated by you.

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Hola MrAl, please do not take this as inconsiderate hijacking.

Mosaic, I am interested in trying the mix of flux and "powder". Do you believe that the way is just filing with the smaller grain file available? Any other suggestion or idea?

I understand this is one "pass" process since I do not see a chance of "refining" the powder even more afterwards.

Hi,

Why you dirty rotten inconsiderate hijacker you! (ha ha)

I would also be interested in hearing just about anything useful that has to do with solder paste too.
How about use a cheeze grader? (chuckle)

Seriously, from what i read a set of "abrasive sponges" does the trick and you can refine more and more. By that they might mean the scrubby kind with one green side, but im not really sure.

MrAl said:

Why you dirty rotten inconsiderate hijacker you! (ha ha)

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The same as with jokes with idioms or local jargon, when you manage to understand, you have no energy left to take offence.

Once I complete the soldering of a level translator (5 to 3V3) right now on my bench, I will try to grate some solder as finely as possible. Wondering if instead of those sponges, steel wool could make it...

According to the manufacturers, the solder powder needs to be beads and not oxidized. I think the lack of surface oxidation is probably more important. Ideally, you could do the filing in an argon atmosphere, but you probably do not have such a glove box in your kitchen. As an alternative, consider doing the filing under water, alcohol, or light naptha that has been taken to boiling and let cool (i.e, "degassed").

John

Hola John,

Any chance to do normal filing and then deoxidize the powder with a simple kitchen-table procedure?

Well, lead oxides are soluble in acids, e.g., vinegar. Some people say that is what killed the Romans (BTW, lead oxides are sweet. They were used as a cheap substitute for sugar.).

There are some videos on the internet of various formulations of lead paste. Of course, the Kester brand with bright, shiny balls forms a very nice joint. The "other" brand does not. As I said, I don't see how balls vs. flakes/shavings per se will make much difference. Albeit, balls have less surface area per volume than flake/shaving have. I do think surface oxidation on the lead will make a difference. So, however you prepare the paste, try to avoid surface oxidation, which will form quite quickly. Ever try to solder aluminum? Same problem, but much worse, as aluminum is much more reactive with air. Aluminum solders are typically high in zinc, which counteracts that effect.

John

Is this a problem with the lead-free solders too? e.g. Sn96 which I hate.

atferrari said:

The same as with jokes with idioms or local jargon, when you manage to understand, you have no energy left to take offence. View attachment 96397 View attachment 96396

Once I complete the soldering of a level translator (5 to 3V3) right now on my bench, I will try to grate some solder as finely as possible. Wondering if instead of those sponges, steel wool could make it...

Click to expand...

Hi,

If you get any success at all or even failure i'd like to hear what happened. We might find a way.

jpanhalt said:

Well, lead oxides are soluble in acids, e.g., vinegar. Some people say that is what killed the Romans (BTW, lead oxides are sweet. They were used as a cheap substitute for sugar.).

There are some videos on the internet of various formulations of lead paste. Of course, the Kester brand with bright, shiny balls forms a very nice joint. The "other" brand does not. As I said, I don't see how balls vs. flakes/shavings per se will make much difference. Albeit, balls have less surface area per volume than flake/shaving have. I do think surface oxidation on the lead will make a difference. So, however you prepare the paste, try to avoid surface oxidation, which will form quite quickly. Ever try to solder aluminum? Same problem, but much worse, as aluminum is much more reactive with air. Aluminum solders are typically high in zinc, which counteracts that effect.

John

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Hi,

Interesting, i noted that the solder paste had a 'sweet' sort of smell to it.

I have also read that the oxide on the 'balls' keeps it from reacting with the flux for a longer time period in storage, although that would not be needed if the paste was used right after making it. Loosing all the oxide supposedly causes the balls to stick together over time which makes bigger balls and so maybe less flow during soldering.

Needles: Remember, it's OD. See https://en.wikipedia.org/wiki/Needle_gauge_comparison_chart
A few I checked between #16 and #22 seems close to AWG numbers.

Hi,

Yes, good point KISS.

I checked, and for an ID close to #22 i would have to get #19 or #20. Something to keep in mind.

I tried the 'trick' this thread was about a little while ago with an 8 pin SMD package and 1206 size capacitor.
I pushed out about a 3/4 inch strip of the paste maybe came out to 1/8 inch diameter. Let it sit for one hour uncovered, as i had something else to do anyway. Seemed to work just the same as by letting the whole tube stay out for 3 hours. I did not notice any difference in the way it spread or the way it melted and formed into shiny solder and sought out the pins and pads.
There was a question of maybe some extra moisture, but i can tell you once you hit it with the hot air any extra moisture would boil away quickly. If it does affect the joint, i cant tell as there is nothing apparent that is different from doing it the normal way. Funny i only used about 1/4 inch of that strip of paste as it takes to very little to solder one 8 pin SMD chip and one tiny 1206 capacitor. I used a 28 pin SMD to DIP surf board and found that the capacitor terminals align nicely with 0.1 inch spacing pads so it bridges nicely over one 0.05 inch spaced pad.
I'll try to post a pic in a minute or two.
Ignore the spots that is not solder.

atferrari said:

Hola MrAl, please do not take this as inconsiderate hijacking.

Mosaic, I am interested in trying the mix of flux and "powder". Do you believe that the way is just filing with the smaller grain file available? Any other suggestion or idea?

I understand this is one "pass" process since I do not see a chance of "refining" the powder even more afterwards.

Click to expand...

As I recall, filing with an iron file worked ok, but I also recall doing it with a dremel tool (not a stone). I believe it was a ceramic tile cutter. A jeweller's file seems to give the finest powder.
You can reprocess poor grindings by remelt.
I suppose it's possible to sieve it for quality control, but I never had to bother...it worked fine.

Have a lookt at this thread back in 2010...from post #9
https://www.electro-tech-online.com/threads/how-to-make-solder-paste.113743/#post-931761

jpanhalt said:

Copper is much less reactive. You can put a puddle of CA on a scrap piece of PCB and it will stay for an hour. I sometimes do that when I am using the CA to fix very small SMD's to the PCB before soldering. A microdot of CA applied with a wire toothpick will hold resistors and capacitors in place nicely.

John

Click to expand...

Excellent tips!

Rosin flux gel does the tackiness for me.