Essential Consumables for Building Circuits - Workbench Wednesdays 31

I think flux paste is generally for plumbers

Hmm. Now I wonder what "shelf life" means in these datasheets. Is that how long it can sit on a distributor's shelf before being opened? Or is it how long it is good for after it has been opened? Or is it only good for 5 years after being manufactured?

Of the three datasheets, none seem to differentiate the shelf life between storage and operation.

According to their data sheet, the Chemtronics flux pens (CW8100, CW8200) have a shelf life of 5 years?

No, I believe you have these swapped over.

Isopropyl Alcohol (IPA) dissolves oils.

Denatured alcohol contains additives.

Sorry, but that is something I have never heard and cannot seem to find a reference. IPA is used throughout the electronics industry.  It is specifically used because it removes the ionic salts left behind by flux residue.

You might notice, I never used the phrase "rubbing alcohol" which may contain additives that make it unsuitable for cleaning electronics.

I do not know of any electronics manufacturer that cleans their boards with denatured alcohol.

Liked the video.  One FYI, Isopropyl Alcohol has oil in it to prevent freezing/ burning your skin.  Denatured alcohol does not have the oil and will not leave a film.

From YouTube,

Do the flux pens/syringes/pastes need to be refrigerated to extend their shelf life? In the video that was mentioned as required for the flux containing solder paste. I'm only a light hobbyist so I may go many months before soldering or desoldering something, so I've avoided buying any flux thinking it'd expire before I use much of it.

I mostly use the Kester flu pen and the Chip Quik flux. According to Kester's datasheet, it has a shelf-life of a year at room temperature. While my preferred flux, the Chip Quik SMD291 datasheet says it has a >24 month shelf-life regardless if cooled. And I use my flux up faster than one year.

From YouTube,

What about washing pcb’s with water? I’ve seen this from a few folks and even some that wash larger boards in a dishwasher. I’ve never done this myself as it just seems wrong, but the results look good on camera and the boards always seem to work. Is there a technical reason that would make this a bad practice?

There are two reasons I wouldn't recommend using a dishwasher.

1. The flux residue, and other chemicals, may get trapped in the recirculating pump, which would then end up on your dishes. Not all flux is water-soluble.

2. Water contains minerals that can containment the board.

When washing with water, it is better to use distilled water and ideal to use deionized.

Others may have different opinions, but I won't be putting any boards in a dish washer any time soon.

I got thinking, it might be useful with a brush. Maybe a lower-cost alternative to a flux pen.

I am also curious about the usage of the flux in a can - it just can't be used effectively IMHO.

Senior engineers might remember transformer soldering iron and they were also used with a solid flux in a can. People used it in a way that they heated the soldering iron using a button, put it into the can, then released the button, let it cool and then soldered the joint. The trouble is, once the flux is heated for a few seconds, it doesn't work any more, so this worked really random.