Skip to main content
27 votes
Accepted

What happens if a solder joint cools before all the flux has evaporated?

Technically, the unevaporated flux will form voids in the solder and mechanically weaken it. Additionally, the non-conductive voids will slightly increase the overall resistance of the connection. ...
WhatRoughBeast's user avatar
24 votes
Accepted

Is acetone or isopropyl alcohol better for removing rosin flux?

Acetone being used to clean circuit boards can be problematic. The biggest issue that I found was that it leaves a residue in the board that still requires several other cleaning steps to get rid of ...
Michael Karas's user avatar
14 votes
Accepted

Storage of liquid flux

Liquid flux is typically flammable (when it is) because there is some alcohol-like carrier (eg. butanol). You can look up the MSDS for the particular flux you have and find out what that material is. ...
Spehro Pefhany's user avatar
11 votes
Accepted

Why does PCB copper surface oxidize when I apply flux on its surface?

If you look at the datasheet, you'll see a few important tips: This flux must be cleaned after you apply it, since it is corrosive, and shouldn't be used on bits that you're not soldering. The latter ...
BeB00's user avatar
  • 5,485
11 votes

Storage of liquid flux

The main ingredient is alcohol, and possibly water. It will not spontaneously combust. A bookshelf is safe enough, for reasonable amounts (and 1l sounds reasonable). I'd look that it doesn't stand in ...
Marcus Müller's user avatar
10 votes

Is acetone or isopropyl alcohol better for removing rosin flux?

If you want real results to clean PCBs after rosin-based fluxes, you should use a specially-formulated solvent. Typically the solvents are based on IPA, but contain Toluene, Heptane, and ...
Ale..chenski's user avatar
  • 40.9k
9 votes

Solder Paste vs Solder Flux

This is not the stuff to use to solder electronic boards, this is for plumbing fittings, a flux to be used in addition to stick of solder. Electronic boards require either 'flux-cored solder' for ...
Neil_UK's user avatar
  • 168k
9 votes
Accepted

Which flux type to use for SMD hobbyist (home-made) PCB?

If a flux is "no clean" it means it doesn't, under normal circumstances, conduct electricity. The exception is when the flux gets burned by too high a temperature and turns brown. At this point it can ...
Majenko's user avatar
  • 56.3k
9 votes

Recovering from failure to clean off solder flux

I have real doubts that this is your problem. For leakage caused by flux residue I've used a toothbrush and solvent of some kind such as IPA or lacquer thinner as well as soapy water. But the leakage ...
Spehro Pefhany's user avatar
8 votes
Accepted

Are soldering fluxes safe to touch?

There seems to be a translation issue, and it's a good job you asked the question; this is not the roisin flux commonly used in electronics, but Zinc Chloride (if my machine translation of the German ...
pjc50's user avatar
  • 46.9k
7 votes

Clean vs no-clean for high voltage circuit

To the best of my knowledge conformal coating requires very clean surfaces for proper adhesion (see doi: 10.1088/1741-2560/10/3/031002 ). At least in our lab all boards are cleaned using a complex ...
Christian B.'s user avatar
  • 2,006
7 votes

Recovering from failure to clean off solder flux

Kester 2331-ZX is water soluble acid-based flux which needs to be washed off immediately after soldering. If not washed off, it will turn gold black rendering the pad unsolderable. The flux is ...
qrk's user avatar
  • 10k
6 votes

When do I choose to use a rosin based flux or rosin-free flux?

There's three general kinds of solders (not counting lead-free vs leaded). 1) Solid core solder: used for plumbing with acid paste flux you put on copper fittings with a brush. If you don't get the ...
horta's user avatar
  • 12.8k
6 votes

Why is the Exciting Current zero in an ideal transformer?

The big mistake in your question is that with infinite permeability, the inductance of the primary winding also becomes infinite and hence the magnetization current becomes zero. So no, there won’t be ...
Andy aka's user avatar
  • 462k
5 votes

Solder Paste vs Solder Flux

This seems to be an Asian-English thing- calling flux "soldering paste" or even "solder paste". Sometimes the word "cream" is in there. I've seen it in China, Hong Kong and Taiwan, and this "...
Spehro Pefhany's user avatar
5 votes
Accepted

Soldering question

As others have said, practice makes perfect. There are lots of videos on the web but unfortunately they don't all offer great advice. This series is great, John Gammell is a master. It would help if ...
Minho's user avatar
  • 361
5 votes
Accepted

soldering a 12V plug cathode

Most likely, not enough heat. Both the terminal and the wire need to be heated to the melting point of solder for the solder to flow properly. But that spring terminal is acting as a very effective ...
Simon B's user avatar
  • 19.5k
5 votes

Transformer’s Flux and Back-EMF

Before you connect a secondary load, magnetization current is flowing in the primary and this sets up the flux in the core. That flux remains constant as an RMS value with any load changes. Any ...
Andy aka's user avatar
  • 462k
5 votes
Accepted

What is "activity" in solder flux?

Flux "eats" oxidation. You can't make a soldered connection to oxidized metal - it has to be bare, clean metal. Flux removes the oxidized layer, and prevents the bare metal from oxidizing ...
JRE's user avatar
  • 72k
4 votes

How does flux work, chemically, and what are the products?

This is a VERY good question! ALL fluxes throughout welding, brazing, soldering and even the production of metals, work all manner of magic at different stages of their given processes. Oxides are in ...
Ken Mason's user avatar
4 votes

Is acetone or isopropyl alcohol better for removing rosin flux?

For rosin based flux I clean with IPA (93%) and then hot water with a detergent. Then dry. That is for one-of's or a small number of pcbs.
George Herold's user avatar
4 votes

Is acetone or isopropyl alcohol better for removing rosin flux?

Just adding to the answers because nobody's mentioned it yet - as well as melting plastic, acetone can strip the insulation off enameled (magnet) wires. So if you decide to use it be super careful ...
Flyingfirepig's user avatar
4 votes
Accepted

What type of electronics soldering is this soldering flux used for?

The clue is it says 'weak acid'. This is an acid-based flux, for soldering 'big stuff', cables onto terminals, and it should be suitable for plumbing as well. Clean the joint after soldering. For ...
Neil_UK's user avatar
  • 168k
4 votes
Accepted

Effects of no-clean flux or RMA flux residue on signals

I have run into this problem with precision photodetection circuitry. After reworking a board any leftover flux threw off the instrument calibration due to increased surface leakage bypassing guard ...
Luke Gary's user avatar
  • 1,075
4 votes

Using and maintaining lower end soldering iron tips without destroying them

That is exceptionally bad. It is not normal for a tip to be destroyed after a single use on 350 degC. Even a single use on ~420degC and probably even a bit higher should not immediately damage the tip....
Arcatus's user avatar
  • 1,845
4 votes
Accepted

Understanding the flux linkage in transformers

It is good if the flux is confined to inside the core. Magnetic flux changes result in a circular electric field. Any closed loop wire encircling the flux, no matter what diameter and how located, ...
user107063's user avatar
  • 3,743
3 votes
Accepted

I need help for soldering. Is this good flux for use on PCB/Electronics?

Both will work. In this particular case, the paste is actually essentially the same flux as the wire provides, so there is no penalty (other than a very high inconvenience level) in using it. In ...
WhatRoughBeast's user avatar
3 votes

I need help for soldering. Is this good flux for use on PCB/Electronics?

You just need the solder with the flux core. You don't need the flux paste. The flux paste is essential when "drag-soldering" fine-pitch devices, because the blob of solder on the iron tip no longer ...
Leon Heller's user avatar

Only top scored, non community-wiki answers of a minimum length are eligible