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Sponges - if you have a decent iron, you should be using a clean, damp-not-wet, sulfur-free, cellulose sponge. This means: buy the type sold for use with a sol

Sponges - if you have a decent iron, you should be using a clean, damp-not-wet, sulfur-free, cellulose sponge. This means: buy the type sold for use with a soldering iron, squeeze the water out of it after wetting it, and switch to a fresh one when it gets cruddy. I have never had an issue. Flux - hobbyists either try to use 50-year-old parts with totally oxidized plating and no flux, or they use too much flux. New parts should not need more flux than you have in your flux-core solder or in your paste. The next thing that happens after people discover flux is that they want to clean it off, and 99% of the time, hobbyists should not be cleaning flux. If you cannot measure the reason for cleaning your board, leave it alone. The manufacturers will tell you that modern RA and RMA type fluxes do not require cleaning for "most applications" - and "most applications" almost certainly means you. No-clean flux should be called "never-clean" for the reason you outline. You shouldn't try to clean it, and it will never get as clean as you'd like if you do. I like no-clean for stuff I'm going to show to other people. You will almost certainly use no-clean in production if you go to production. Water-clean is lovely stuff but it's very unforgiving. It will corrode if not cleaned, and you have to plan to wash your board by using sealed parts or adding water-sensitive parts afterward. You have to be careful with tip temperature too or it will destroy your tips. I have a spool of 63/37 water-clean I've used maybe twice - the boards sparkled but it was just too much trouble.

CarVac 4y ago
"Yes-clean" flux has absolutely been the cause of controller malfunctions due to its conductivity for makers of my controller project. It needs to be removed. But yes, no-clean flux is best left where it is.
- buescher 4y ago
  Could be so, and it can depend on the flux and the processing, but it's almost never the flux. From a 10,000 ft look at your project, I wouldn't expect it to need the high isolation or high impedances that would drive a serious cleanliness spec. You could have other issues that a temperature and humidity test would uncover with no-clean, for example. We can discuss them if you'd like. Depends on what you mean by "yes-clean" though - "water-clean" OA flux must absolutely be cleaned - it can start to corrode overnight even.
  - CarVac 4y ago
    The "yes-clean" flux I'm talking about is high-solids rosin flux that leaves a conductive residue. The conductivity can definitely cause a circuit to fail. Makers come to our discord chat, asking why their builds aren't working and post a pictures. I suggest cleaning the flux off, and they start functioning. As an aside: My current solder brand (Chip Quik) has a "no-clean water-soluble" flux that I'm curious about. Surely that's not going to be as corrosive as the flux you're talking about. (I probably wouldn't use it myself because it needs 140°F water to dissolve)
    - buescher 4y ago
      Without answering how much conductivity you had, how it caused the circuit to fail, what part of your circuit failed, and in what way, you haven't really narrowed it down to the flux, even if cleaning helped. There are a number of more likely root causes of the kind of issue you describe. I can make time for going into that if you're interested. "No-clean water soluble" is news to me. Don't know if I'd trust that in a humid environment.

CarVac 4y ago

"Yes-clean" flux has absolutely been the cause of controller malfunctions due to its conductivity for makers of my controller project. It needs to be removed. But yes, no-clean flux is best left where it is.

buescher 4y ago
Could be so, and it can depend on the flux and the processing, but it's almost never the flux. From a 10,000 ft look at your project, I wouldn't expect it to need the high isolation or high impedances that would drive a serious cleanliness spec. You could have other issues that a temperature and humidity test would uncover with no-clean, for example. We can discuss them if you'd like. Depends on what you mean by "yes-clean" though - "water-clean" OA flux must absolutely be cleaned - it can start to corrode overnight even.
- CarVac 4y ago
  The "yes-clean" flux I'm talking about is high-solids rosin flux that leaves a conductive residue. The conductivity can definitely cause a circuit to fail. Makers come to our discord chat, asking why their builds aren't working and post a pictures. I suggest cleaning the flux off, and they start functioning. As an aside: My current solder brand (Chip Quik) has a "no-clean water-soluble" flux that I'm curious about. Surely that's not going to be as corrosive as the flux you're talking about. (I probably wouldn't use it myself because it needs 140°F water to dissolve)
  - buescher 4y ago
    Without answering how much conductivity you had, how it caused the circuit to fail, what part of your circuit failed, and in what way, you haven't really narrowed it down to the flux, even if cleaning helped. There are a number of more likely root causes of the kind of issue you describe. I can make time for going into that if you're interested. "No-clean water soluble" is news to me. Don't know if I'd trust that in a humid environment.