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Is it necessary to remove flux?

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Damo666

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I've just knocked up a couple of pcb's running on vhf.Is it a necessity to remove the residue of flux left by multicore solder, or can i just leave it? If i should, what's the best way/chemical to use please? Thanks in advance.
 
An old tooth brush (hard) and acetone or alcohol.
You don't have to do it in most cases.

I'm still Googling to answer this, and gain more insight but No Clean Fluxes seem not to be recommended.
https://www.qsl.net/ve3mcf/elecraft_reflect/Elecraft_Recommended_Solders.txt

**broken link removed**
Flux
In high-temperature metal joining processes (welding, brazing and soldering), the primary purpose of fluxFlux (metallurgy)

In metallurgy, flux is a substance which facilitates soldering, brazing, and welding by chemically cleaning the metals to be...
is to prevent oxidation of the base and filler materials. Tin-lead solder, for example, attaches very well to copper, but poorly to the various oxides of copper, which form quickly at soldering temperatures. Flux is a substance which is nearly inert at room temperature, but which becomes strongly reducing at elevated temperatures, preventing the formation of metal oxides. Secondarily, flux acts as a wetting agent in the soldering process, reducing the surface tensionSurface tension

In physics, surface tension is an effect within the surface layer of a liquid that causes that layer to behave as an elastic...
of the molten solder and causing it to better wet out the parts to be joined.

Fluxes currently available include water-soluble fluxes (no VOCVolatile organic compound

Volatile organic compounds are organic chemical compounds that have high enough vapour pressures under normal conditions to...
's required for removal) and 'no-clean' fluxes which are mild enough to not require removal at all. Performance of the flux needs to be carefully evaluated; a very mild 'no-clean' flux might be perfectly acceptable for production equipment, but not give adequate performance for a poorly-controlled hand-soldering operation.

Traditional rosinRosin Overview

Rosin, formerly called colophony or Greek pitch, is a solid form of resin obtained from pines and some other pla...
fluxes are available in non-activated (R), mildly activated (RMA) and activated (RA) formulations. RA and RMA fluxes contain rosin combined with an activating agent, typically an acid, which increases the wettability of metals to which it is applied by removing existing oxides. The residue resulting from the use of RA flux is corrosiveCorrosive

A corrosive substance is one that will destroy or irreversibly damage another substance with which it comes in contact....
and must be cleaned off the piece being soldered. RMA flux is formulated to result in a residue which is not significantly corrosive, with cleaning being preferred but optional.

and later:
An improperly selected or applied flux can cause joint failure, or if not properly cleaned off the joint, may corrode the metals in the joint over time and cause eventual joint failure. Without flux the joint may not be clean, or may be oxidized, resulting in an unsound joint.

still later:
For PCB assembly and rework, alcohol and acetone are commonly used with cotton swabs or bristle brushes to remove flux residue.
 
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Good man.In that case i'll use my girlfriends nail varnish remover.She says it contains acetone.Cheers.
 
You can use that if you superglue the two of you together too :)
Clear heavy nail polish is also nice to have on hand. (what is that, it's not a pun, is it?). I have used it as an insulator, coil dope, to hold screws in place, etc. It's not fire proof and it is low Q as a coil dope.
 
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