rinse pump thing

[adx]

oh man 275psi

That is another good question, how much is too much for shooting under PCB chips

I don't know, 30000 psi?! (Department of Conservation above.) At first guess 0402 vs say 0805 shouldn't make much difference, because the 'beam' of pressure acts over an area, and shear force and solder joint tension on pads are also an area based things. To be 'scientific' one could measure the force for different size blocks then find or characterise removal force needed, but surely the most direct method is to see what it takes to wash off various sized parts. I guess they'd be pretty robust, I don't think I've waterblasted a loaded board before certainly not while on, but I do have a HDD board I'd like to debug...

I've always been satisfied with the idea of low pressure rinsing, assuming the cleaning is done right. If it can dribble in one side of something, then out the other, I'm happy (or at least was). Saves worries about getting it only partially in something like a pot or switch, bad enough but then how do you dry it. I don't like the idea of leaving things to air dry no matter how pure the solvent is supposed to be (or leaving it to leach something or corrode), so prefer a brutal fling or spin, or a saturated air blast until it's "dry". A quick blast of atmospherically-dry air shouldn't do too much harm (evaporate before removed). But "leaving it to dry" is how vapour phase cleaning is done, and many manufacturers use a heated dryer and call it done.

I've never really worried about gunk under a QFN (until now). Despite my earlier story with the conductive boards, I pretty much never see boards cleaned in production. Just trusted to the no-clean flux and not make too much of a mess handling everything prior to assembly (like when people grab a board by the flat (you know what I mean) surfaces prior to soldering). After that the pads have either parts on them or wires sticking out of them and the more critical areas tend to be where the components are. No-clean flux is hard to get off, and possibly counterproductive if it's providing a conformal coating function itself for tin whiskers etc. Most places conformal coat over it if needed. One place I worked had a high-volume (I guess, 1M+/yr) module which got dusty due to depanelling (with a little router) they maybe gave that a quick rinse before coating with something smelly and apparently quite toxic which needed a special double chamber OSH (as it's known here) room that looked like some sort of train or pizza oven in the middle of the factory (more so than the SMT lines, of which there were many).

If I'm washing a grungy prototype, hand made board or something with optics visible through a window, I tend to use an IPA soak, toothbrush, tap water at pressure, fling dry, DI rinse, fling dry then an actual dry somewhere where it won't take too long (like behind the PSU fan of the busiest engineer's PC...). Grungy mods or rework maybe just alcohol. I steer clear of ultrasonic for electronics unless there's a need, this thread has renewed my interest though. But if there's a QFN or any chance for cleaning goo to get stuck, I'd have to think about whether I'm making it better or worse by cleaning. So far as I know, partially cleaned no-clean flux is no worse than uncleaned apart from being all white and an eyesore, I guess remelting it won't expose unactivated flux?

So anyway, hence me not knowing about ROSE testing of boards for cleanliness (where a rinse of IPA and DI water is tested for conductivity then back-calculated to the equivalent mass of NaCL per area on the board and sometimes components). I guess if it's going to be done, it'd be something the factory might do as a test and I'd never know about (if done offsite). Eg IPC-TM-650 2.3.25.1 for bare boards (which'd be done at the fab I guess).

Alconox generally not available here (banned soap). Sounds like a good cleaning setup, I've tried to set up a little station with rain from a slightly stinky pickle barrel scrubbed of nutrients (from the rain, not the barrel, it still grows algae) filtered and optionally DId for a cheap source of bulk pure water, sprayers and cleaning chemicals etc. But not quite there yet. Dehumidifier water can be very good (less residue than rain even of 0 ppm ionic, less than electronic grade IPA too, evaporated down onto a black spotting plate or glass slide). Those cheap magnetic rotor pumps from Aliexpress make processing some of this very convenient and kind of fun. Watch out though - playing with pipes and water is diagnostic for autism! (As I found out the hard way, despite not even remotely meeting the screening threshold, somewhat surprisingly.)

[coppercone2]

I thought it was a good idea for gardening with rain water because you can get diagnosed deceased from a well pump replacement (and actually from a mains water leak, if you spring a leak, in a larger house $5000 was triage)

I was by the back pipes recently when the washer got turned on and seeing it recoil scared me too, that needs a damper for sure.

I also saw those little pumps keep people alive. Kind of silly to say when 1/3 Americans will die of heart disease (small pump)  I would not wanna scare the future inventer of a better robot heart away from playing with fluids    maybe they need to make a garbage disposal for the circulatory system

But the work can be awful, I spent 3 hours on saturday cleaning out my vacuum portable sqeegee, felt like I am never gonna get that time back

[adx]

Oh, been meaning to say I tried making TSP the "proper" way (using the Wikipedia formula above, and guessing at all the conditions and quantities with no idea of what I was doing in my metal coffee cup) and it didn't work. This lot came out wet, and crystallised into long needles amongst the slush overnight. Did not seem to be any good at cleaning. I think I'll leave it to the experts for the time being. Unlikely I'd drink it (unless it turned brown and I had an "oooh, coffee dregs" moment before my morning caffeine), but could make something noxious.

People were using vacuum cleaner turbines (the small DC brushless ones) during the worst of covid (so far), so doesn't surprise me those little pumps are getting used for life support (dialysis? dare not look).

And found that plastic jar that got eaten (the innocent bystander mentioned above), here is a pic:

[BradC]

I've just gone back to the original post about a "rinse pump thing". I picked up a dental water flosser thing for $10 on sale at the supermarket. No grease, no contamination and loads of pressure in a directed jet. USB re-chargeable and cheap.

Edit : And for TSP I just phoned around a few chemical suppliers and found *all* of them would sell it. I bought a kilo a couple of years ago. Great for periodic cleans on the washing machine, dish washer and coffee machine.

[Kean]

I've just gone back to the original post about a "rinse pump thing". I picked up a dental water flosser thing for $10 on sale at the supermarket. No grease, no contamination and loads of pressure in a directed jet. USB re-chargeable and cheap.

I had the same idea, and picked one up on AliExpress for less than AUD $8, but it was a fail.

1. The stream has pressure, but not really enough to get under components or move anything around.  A brush in a tub is more effective.
2. More water came out around the base of the tip than the end of tip.  Maybe this is the reason I found the pressure too low.  Not sure if there is a o-ring seal, or they sent the wrong style tips.
3. You have to press the button multiple times before it turns off!
4. I used it at my bench which also has my desktop PnP, stencil printer, PCBs, & reels of parts.  Because of the above 3 points, I got water everywhere!  At least it was demineralised water.
5. It works best if held upright, unless the tank is full which isn't the case for very long.  So you really must use it over a sink and move the PCB around the stream, rather than pointing the water stream at the PCB.

One day I might try disassembling it to see if I can fix #2, and how the pump is arranged re potential contamination.  Not a great loss if not.

I have a better quality Waterpulse unit at home that I use for its intended purpose, which has a hose going to a separate large (800ml?) tank.  Might be a better solution if I decide to try again.