Electronics > Beginners

Flux

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perieanuo:
I must reply to acid haters:
from wikipedia:

--- Quote ---Composition
La colophane est composée à 90 % d’un mélange d’acides organiques de la famille des diterpènes appelés acides résiniques, qui répondent à la formule brute C20H30O2. Ces acides résiniques sont des isomères. La proportion des différents acides résiniques dans la colophane est variable suivant l’espèce de pin à partir de laquelle la colophane a été obtenue. Certains acides ne sont présents que chez certaines espèces (et leur sont donc caractéristiques)
--- End quote ---
I used colophane for years, it's basically acid, works without damage to pcb.
ALL is in quality of work done, I must repeat, cleaning is a essential part after soldering.
I saw basic fluxes that damage the boards, like those intended for copper plumbing.
So for beginner use colophane flux or RMA223 or cousins.Cost is ok.
What other people discuss for pro soldering is another matter.If the person asks, obviously it's not a pro, so let's discuss cheap fluxes.I can do me also a big article about pro's flux, who cares.
But don't repeat like a monkey acid is bad.Maybe it's not the best.
regards,Pierre

tooki:

--- Quote from: Zero999 on June 12, 2019, 10:23:18 am ---Also note that lead free solder is not suitable for hobbyist usage. It's actually more dangerous, than leaded solder, because it requires a higher temperature iron and a more aggressive flux which is irritating to the lungs. Although lead is toxic, providing sensible precautions are taken, such as hand washing after use, the amount adsorbed into the body is well below the level which can cause adverse effects.

--- End quote ---
Well, regardless of your opinions on the matter, since March 2018, leaded solder may no longer be sold to consumers in the EU (and other countries that follow the EU's rules, like Switzerland; the rule in question is REACH Annex XVII). Hobbyists here in Europe will have to work with lead-free, like it or not. Honestly, though it's not as easy as leaded, it's still fine, especially if you buy a more expensive alloy like SAC305, and not the cheap 99.7-100% tin kind. It's true that the flux fumes are a bit worse, but it's not as though the fumes from classic rosin flux are somehow good for us, either!


--- Quote from: Zero999 on June 12, 2019, 10:23:18 am ---Lead free solder was introduced because people often don't dispose of their old electronic equipment responsibly, resulting in lead leaching out into the environment and polluting the groundwater. It has nothing to do with health and safety.

--- End quote ---
Well, RoHS was conceived back when CRT TVs contained several kilos of heavily leaded glass. But ultimately, it was a dumb policy enacted by do-gooder politicians without enough technical knowledge to understand the consequences.

tooki:

--- Quote from: perieanuo on June 13, 2019, 08:38:23 am ---I must reply to acid haters:
from wikipedia:

--- Quote ---Composition
La colophane est composée à 90 % d’un mélange d’acides organiques de la famille des diterpènes appelés acides résiniques, qui répondent à la formule brute C20H30O2. Ces acides résiniques sont des isomères. La proportion des différents acides résiniques dans la colophane est variable suivant l’espèce de pin à partir de laquelle la colophane a été obtenue. Certains acides ne sont présents que chez certaines espèces (et leur sont donc caractéristiques)
--- End quote ---
I used colophane for years, it's basically acid, works without damage to pcb.
ALL is in quality of work done, I must repeat, cleaning is a essential part after soldering.
I saw basic fluxes that damage the boards, like those intended for copper plumbing.
So for beginner use colophane flux or RMA223 or cousins.Cost is ok.
What other people discuss for pro soldering is another matter.If the person asks, obviously it's not a pro, so let's discuss cheap fluxes.I can do me also a big article about pro's flux, who cares.
But don't repeat like a monkey acid is bad.Maybe it's not the best.
regards,Pierre

--- End quote ---
FYI, "colophane" is called "rosin" in English. (We also have the archaic word "colophony" for it, but this isn't used by native speakers any more.)

Anyhow, while rosin does indeed consist of resin acids, it's not an "acid flux" as such. The abietic acid in rosin is not active as an acid in any meaningful sense. It's only activated when hot, which is why it works so well as a flux. At room temperature it's so neutral that it can be used to protect copper from corrosion.

I cannot state emphatically enough how irresponsible it is to say that acid plumbing flux is in any way acceptable for hobbyist electronics use. It's not. Even the acid fluxes made specifically for electronics (the "water soluble" fluxes) can only be used in VERY strictly controlled applications with strict cleaning processes, and are categorically unsuited for hobbyist use.

tooki:

--- Quote from: fixit7 on June 11, 2019, 09:53:10 pm ---I am researching flux. I see there are lead free, acid based, and no clean up ones.

Which is best for circuit boards?

I know every situation will be different.

--- End quote ---
Basically, fluxes fall into a few categories (in terms of active ingredient, not the delivery method):
1. Rosin
2. No clean
3. Alcohol
4. Acid (water soluble)


First off, acid/water soluble fluxes are categorically unsuited to hobby electronics. Do not even think about using them. (Any flux that says it uses ammonium chloride or zinc chloride is an acid flux and must not be used.)


Rosin fluxes are made from the refined sap of pine trees, with activators added to improve the fluxing action. You can get rosin fluxes with varying concentrations of rosin and activators, making them more or less aggressive, and more or less hazardous. (Halogen activators are more effective, but bad for the lungs.)

Highly activated fluxes, which are better for hard-to-solder things like old components, are labeled as RA, ROM1 (halogenated), or ROM0 (halogen free). The flux in my favorite solder, Kester 44, is RA.

Slightly milder rosin fluxes are classified RMA, ROL1, and ROL0.


No-clean fluxes are essentially a subtype of rosin fluxes, made from either extra-refined rosin, or even from synthetic rosin (sometimes labeled as resin instead), such that the flux residues are clear and look better. They also may contain much less of the active ingredients, especially in liquid and gel fluxes. They aren't usually as active as rosin fluxes. They may be classified RMA (rarely), ROL1, ROL0, REL1, or REL0. (Other classifications exist, I just listed what you're likely to see.)

- Both rosin and no-clean fluxes exist as rosin core solder, paste and gel, and liquid flux forms. Note that despite the name, you can clean off no-clean flux, and that despite not saying so, rosin flux residue does not need to be cleaned for most applications. For the kind of stuff you're doing, it's purely a matter of aesthetics.

Alcohol fluxes are used in some gel fluxes and in solder paste.

Lead-free fluxes are simply fluxes formulated to tolerate the higher temperatures of lead-free soldering. (Regular fluxes may degrade at those temperatures before having a chance to work.)



In a nutshell, here's what I recommend:

1. If you can, use rosin-core leaded solder as your everyday solder. It's the easiest to work with. (For example, my favorite solder, the Kester 24-6337-00xx series, which is 63/37 leaded alloy with 44 (RA) flux. I recommend either 0.031" or 0.020" size.)

2. A tacky gel or paste flux. I use the MG Chemicals 8341 No-Clean Flux Paste. This is really good for heavily corroded surfaces, or for SMD components, where the tacky texture helps hold components in place. (MG also makes the 8342 RA flux paste, which should be even more aggressive, I just haven't had the chance to try it.)

3. A liquid flux pen. The low solids content makes these not as effective as the paste, but it's easier to clean up, and works well for when you need to flux something that isn't heavily corroded. I use this often for tinning clean wire, for component legs and pads on through-hole soldering, etc. I'd suggest an MG Chemicals 835-P, Kester 186, or SRA 312.

Zero999:

--- Quote from: tooki on June 13, 2019, 09:31:41 am ---
--- Quote from: Zero999 on June 12, 2019, 10:23:18 am ---Also note that lead free solder is not suitable for hobbyist usage. It's actually more dangerous, than leaded solder, because it requires a higher temperature iron and a more aggressive flux which is irritating to the lungs. Although lead is toxic, providing sensible precautions are taken, such as hand washing after use, the amount adsorbed into the body is well below the level which can cause adverse effects.

--- End quote ---
Well, regardless of your opinions on the matter, since March 2018, leaded solder may no longer be sold to consumers in the EU (and other countries that follow the EU's rules, like Switzerland; the rule in question is REACH Annex XVII). Hobbyists here in Europe will have to work with lead-free, like it or not. Honestly, though it's not as easy as leaded, it's still fine, especially if you buy a more expensive alloy like SAC305, and not the cheap 99.7-100% tin kind. It's true that the flux fumes are a bit worse, but it's not as though the fumes from classic rosin flux are somehow good for us, either!
--- End quote ---
I doubt that will make much difference. I expect hobbyists will still have no problem getting leaded solder years to come. A quick search reveals it's widely available on-line and I doubt many places will check whether the buyer an individual or a business.

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