Solder Diameter Question

[wraper]

IMHO you mainly need 0.5 or 0.56mm for general work, maybe 0.7 or 1mm if you solder a lot of larger joints to feed the solder faster. For tiniest of parts get 0.25mm, but you'll never spend even 100g of it. No need for other sizes unless you do a lot of some specific job where it fits better.

[bostonman]

I don't disagree.

I'm allotting myself a few bucks for solder because I've been somewhat burned by wrong sizes for different jobs. Last year I finished work on an oscilloscope repair that required I replace a hybrid. Long story short, I had to run a few jumpers to the IC pins and the 0.81mm solder resulted in bridges.

My plan is to go thinner, and, from what I'm seeing at my company, I think the 0.38mm is small enough. My current 0.81mm has done everything I've needed it to do when soldering everything other than the hybrid and 0402.

I'm uncertain if I overlooked the core or flux amount in the link, but I also haven't seemed to find the core in others I've looked at either.

Did I overlook something?

[tooki]

$80 63/37 RMA flux Kester (0.015" / 0.38mm) : https://www.digikey.com/en/products/detail/kester-solder/24-6337-9703/365518

Am I missing the core size (flux amount) in the description? I see it's RMA, 63/37, 0.38mm, but don't see anything about the core.

The datasheet lists 50,58, and 66 for 1.1%, 2.2%, and 3.3%, but I don't see any associated numbers.

Nah, you’re not missing anything, digikey just has incomplete metadata for that solder. (One of us should send a report, they’re usually quite good about fixing it.)

On the Kester website they list all the part numbers on each product’s page, e.g. for the 285 wire solder:  https://www.kester.com/products/product/285-flux-cored-wire

By the part number it’s size 66 core, so 3.3% flux.

[bostonman]

Wow.... I clicked on all the links on DigiKey and didn't find the list of part numbers you provided.

This is a help, thanks.

[wraper]

My plan is to go thinner, and, from what I'm seeing at my company, I think the 0.38mm is small enough.

It will be a pain for through hole jobbies though. So will suck unless you have other sizes.

[bostonman]

Previous posts state I already have 0.81mm (0.031"), which I use for through-hole (and other stuff).

The 0.38mm is for future needs such as 0402 (and other microscopic repairs), and I may get another roll of 0.81mm. I'm just making sure I'm covering various needs for the future.

Although no-clean has been suggested, I think my best bang for the buck is going with RMA 2.2%. My 3.3% seems good, and, although it doesn't need to be cleaned, really does a leave a mess. I'm not as concerned about ascetics as I am (again, thinking in the future) coming across high frequency circuits where the flux residue can be an issue.

The 0.38 is certainly a good addition for reasons mentioned above. Now it's just deciding if I should also add another roll of 0.81mm 2.2% or 3.3%, go with both (which is how I'm leaning), or the one with an additional alloy.

[bostonman]

I've meant to ask, is flux spray cleaner safe to use as opposed to alcohol or does a risk exist that plastic (or the PCB) will corrode?

[wraper]

I've meant to ask, is flux spray cleaner safe to use as opposed to alcohol or does a risk exist that plastic (or the PCB) will corrode?

Why opposed to alcohol? Ethanol and IPA are safe for almost anything. Spray cleaners usually contain stronger solvents which may be dangerous for some plastics. Circuit boards and components generally are very robust to solvents. Switches, unsealed relays, microphones and some other components should not be immersed into solvents as it can bring contaminants inside.

[bostonman]

Just seems no matter how much alcohol and cleaning I do, sticky residue always remains.

Again, it's not for looks, I just have concern that high RF areas may get affected if any residue is left on the board.

[wraper]

Just seems no matter how much alcohol and cleaning I do, sticky residue always remains.

Again, it's not for looks, I just have concern that high RF areas may get affected if any residue is left on the board.

It's because alcohol is not a miracle. It dissolves flux residues, not dissapears them. As alcohol evaporates, flux remains on the board, just spread out.  First you should dissolve them, then remove, for example with paper wipes. Or blow them away by compressed air.

[tooki]

Just seems no matter how much alcohol and cleaning I do, sticky residue always remains.

Sticky residue means you’re just dissolving and redepositing the flux, but not removing it. You either need to use tissues to mop up the flux-laden solvent, or use large amounts of fresh solvent to flush off the flux-laden solvent so it can’t redeposit.

[bostonman]

In the case of the oscilloscope I repaired last year, it had little metal standoffs to lock an RF shield.

Not only did it cause issues with trying to use a brush, but I couldn't do much without risking bending the tabs. I dumped lots of alcohol on the board, gently brushed, etc... and it seemed no matter what, I got white residue.

Anyway, think I'm deviating from the main question which was solder.

[tooki]

White residue is because many fluxes contain constituents that are not alcohol-soluble. Use proper flux remover (which is a blend of solvents) or water-based saponifier to clean it.

[Reminx123]

Hi All,
I was following this thread with interest, it triggers to me the curiosity to test small diameter solder wire with SMD parts. Is anyone willing to sell a small quantity (... how can I define my needs, for example a quantity around 20-30 spool circumference?) of 0.38mm 63/37 RMA 2.2% ? I will pay by Paypal, shipped to Bologna - Italy. Not urgent
Ciao Remin