Flux removal

[Davor]

True.
There are cheaper ways to obtain colophony than bumping into a music store, but it is a sure way nevertheless. So once I stumbled into a not too shabby store and asked for a colophony, and a salesperson asked me what instrument I need a colophon for. When I answered "a soldering iron" he just laughed and gave me the cheapest one. Apparently there are some differences in clarity etc. between a violin colophon and a contrabass one. Anyway, for soldering all work the same.
There are some uses for colophon in rubber industry as well, but such colophony is rather dark and not too clean. Better use a contrabass one

There is one substance that works basically the same: shellac. It is also soluble in alcohol. In case someone in your circle is in furniture renovation business you may go for shellac. It comes in small flakes and it is usually much easier to dissolve in alcohol.

BTW, colophony and other resins tend to shorten your soldering iron tip's life because they promote alloying of various metals, and in a process your soldering tip will become less and less ... until you'll have to replace it. I have a very old iron just for encouraging dull wires to wet by using colophony as an encouraging agent - there is not much of the tip left.

[ivconic]

take a colophony and dissolve it in 95% alcohol. you will get a best flux for any soldering.

I am using kolophonium dissolved in nitro resin.
It is catalyzing process of soldering pretty nice and later presents excellent protection for pcb.

[Jerry]

I am using kolophonium dissolved in nitro resin.
It is catalyzing process of soldering pretty nice and later presents excellent protection for pcb.

Just goes to show that one is never too old to learn something. I have been working on electronics and soldering since at least 1960 and this is something that I had not heard of.

Jerry

[ivconic]

Just goes to show that one is never too old to learn something. I have been working on electronics and soldering since at least 1960 and this is something that I had not heard of.

Jerry

Yes i adopted that method from my older radio amateur colleagues.
Back, some 20 years and more; here we hadn't well supplied stores to buy material and stuff. So we had to find alternative ways to make our diy's better.
Dissolved kolophonium is forming very nice and shiny layer over Cu tracks on pcb.
Dries very fast too.
In process on soldering it is helping much to achieve nice and solid soldering points. Sort of "catalysator".
Now days i can easy obtain lotlack spray and use it instead, but as old donkey; once adopting some habit - i never later change it!
Nitro resin is faster for dissolving it. Also faster to dry. So usually i do that fast.
Prepared pcb, cleaned, washed and dried, usually i coat fast with dissolved kolophonium and leave it to dry for few hours.
Once dry; it is shiny and keeps Cu tracks permanent clean without oxidation.
Same as KT315; i don't approve use of flux paste! God no! It is conductive and greasy! Yiakkk!

[migusch]

I probably didn't get you on the use of kolophonium:
Do You leave the kolophonium after soldering on PCB or do You remove it after soldering.
I used kolophonium / isopropyl alcohol-solution just for preservation of freshly etched PCBs that have to be stored for some weeks/months before further use. I also appreciate the nice tin flow during soldering. After soldering the components I thoroughly clean complete PCB with alcohol and toothbrush because I fear any residual kolophonium might cause leakage-currents. (Kolophonium remains a little sticky and tends to attract dust and with that possibly moisture)

In metal detection applications I recently had big problems with leakage due to condensing damp air, so I thought about covering the finished PCB with some sort of insulating laquer. It should be possible to solder through this kind of varnish in case of repair or modding. I already bought a spraycan of "Lötlack SK10" (manufacturer "Kontakt Chemie") but up to now I refused from using it as a PCB insulation because I have no experience with it in sensible MDs so far and I am afraid of having to remove it again from the already wired and cased PCB in case the detector goes crazy because of possibly resulting leakage-currents. I tried it out on a non-MD test project but this SK10 stays a little sticky as well. Maybe its main ingredient is sort of Kolophonium...?
Does that stuff really insulates or are there known problems with high-gain OPamp circuits?
What do you use for PCB insulation against humidity and dirt?
Best regards, migusch

[Flash1940]

In studying and trying to analyze two or three different metal detectors.....I have noticed several circuits where impedances of the inputs of the op-amps are really high....and in some cases are configured open loop....no feedback. Older metal detectors using lower grade board materials are highly prone to leakage. The newer fiberglass boards are better.....but with conductive contaminants can create odd leakage paths and cause strange behavior. Even a DVM making voltage measurements will drive your circuit nuts....and most DVM's have input Z above 10 Megohms.
Soldering on your MD is like a popular medical philosophy....."do no harm" Your solder connections on the board need to be antiseptic......leave no traces of flux. If you can stick the probes of your DVM in your flux while on ohms....and you see conductivity.....then DO NOt USE THIS FLUX. I use acetone and an acid brush to clean...before & after a solder session. Keep your iron clean (damp sponge)....use the right heat....get in & out as quickly as possible. Check out some of the You Tube videos on soldering....they are a big help....almost as good as having your personal instructor. We're all different....all of us aproach electronics in different ways. If you have all the screws and the board on your bench....you have overcome the biggest hurdle.....FEAR !.....so go to it....and good luck.

Flash

[ODM]

There are several compositions of fluxes. Some modern "no clean" fluxes will work well if left on board, but will eventually develop slight conductivity if working in moist conditions and through temperature changes. Some no-clean fluxes can be a real pain to clean, so if there are few high-impedance points, it can be better to leave it on. Some proper solder manufacturers also supply flux removers which are good for a particular flux.

Rinse the board with the cleaning agent, brush well, and rinse again with the agent a few times. Finish off with water and clear alcohol to remove last residues. After cleaning, apply a good quality lacquer or coating. With some solders (multicore crystal 400) the flux can be removed through repeated washes of isopropyl alcohol and ethanol, and water.

A warning: if you start removing a flux, then be sure to remove it completely. Partially broken flux residue are more likely to cause problems than untouched "no clean" residue.

[Pennypacker]

I also use a Rosin core solder. I sometimes chip of big pieces with a bamboo stick then brush the rest of with acetone.

I have sometimes used alcohol or flux removers, but acetone works much better.

Incidentally, acetone cleans up old tube/valve sockets etc. better then pretty much anything else, including purpose made products.

[ODM]

Be careful with acetone, though. It can attack parts, and also lead to insidious hard-to-trace minor damage when absorbed into capacitors, insulators or harming plastic package seals.

[Pennypacker]

Any liquid that finds its way into a capacitor will cause problems.

Acetone evaporates better then just about anything else, but yes obviously be careful with some paints or plastics.

Just keep it on the bottom of the board, a drop or two landing on any quality component will not bother it, as most are designed to be submerged/washed anyways.

[Polymer]

Thought this might be of interest.

Since i have to use solder with an activated flux where I am most of the time now,
I've started to learn how to clean pcbs. Here's what's helped me:

- Ethyl alcohol 96+ % (I find it smells nice)
- Windex (Window cleaner, the ammonia component is the important part here)

A mixture of 50:50 does the trick for me.
I use toothbrushes for the scrubbing.
Rinsing with pure water (RO or distilled).
Dry well.

If you want to see how much flux is on your board,
you can use a "black light", which is also used for checking banknotes.

Heres what it looks like: