So solder paste needs to be refrigerated. I assume that the reasons why this is necessary is because the balls eventually stick together forming larger irregular balls. Refrigeration helps slow down this process.
If this is the case would it be possible to coat the tin balls with some material that would prevent the effect but also evaporate when heated? If so then this would potentially be a better solder paste as it would keep much longer. (this is more a about chemistry than electronics)
First off, it is NOT an off topic post.
Refrigeration slows the degradation of the flux.
The flux is usually a mixture of components, one of which is a volatile vehicle. Keeping it cold reduces the amount of evaporation which occurs in the flux components. They also eventually expire.
No, the solder balls do not fuse together.
Keep the paste in the fridge and flip it over every week maybe. That helps keep the balls from clumping. Let it warm up before you open it to avoid condensation.
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It's not really all that pertinent to this forum though. It's not that big a deal so I added the OT (better safe than sorry).
Ok, so it's the flux that breaks down. If that is the case then why can one mix when needed? Or add more flux when it starts to harden up? Can one buy "tin dust"?
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sEvaporation? Surely that is not true. Simply keep the material in a sealed container then and no refrigeration needed?
If it's simply the flux then it seems that a simple solution is to add whatever is "evaporating" back into the mix. BTW, do you or anyone else know what the approximate percent by volume the tin is? eg, 20% tin 80% flux, etc... (I know there are many chemicals involved by I'm just curious the approximate amount).
If one had the appropriate "tin dust" could they simply mix it in with the right flux in the right amount and it effectively work as most pro grade solder pastes?
Unless you have the correct formulation, you will screw up any controlled solder process.
If you are talking about hand assemblies, you would be fine.
Once the paste degrades, one begins seeing things like tombstoned components, non-wetting, etc.
Do you know what Reid vapor pressure is?
If it has a volatile vehicle such as alcohol in it, it WILL evaporate unless it gets placed into a pressure vessel.
Alcohol also slowly takes on water, which messes with the reflow process as well.
Absolutely not.
The 'solder' that makes up solder pastes is made up of balls of the alloy involved. They are already alloyed together.
There are no separated tin balls and lead balls. You cannot 'mix your own'.
You have succeeded in defining yourself as a troll.
Either that or YOU have been breathing 'tin dust'.
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Once upon a time, about 25 years ago, i was involved in a early SMT = project=20 where we had to use solder paste in dispensing syringes. The company = bought=20 about 500 g worth of 50 g syringes. After the three month "shelf life" = beyond=20 the end of the project there were 3 unopened syringes left. I asked for = them=20 instead of letting them be thrown away. I used them for about three = years=20 afterwards. Went through one and was about 1/3 through the second when = they=20 all hardened up on me. Don't know the mechanism, suspect polymerization.= =20 Maybe i should have refrigerated them.
But that was some time ago, the current stuff is likely to be way = different.
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