Long time ago I read a story about someone who made his own flux from kitchen ingredients. Main ingredient was citric acid and water, combined with something that made it a bit less runny. Part of the goal was to only use ingredients which dreadily dissove in water, so it’s easy to clean by washing with water.
There is nothing wrong with cleaning PCB’s with water, soap and a brush, if you do it right.
Most important is to let it dry thoroughly before applying voltage.
Another thing that may help is to make the water a bit more conductive to prevent ESD buildup, although this is probably not very important, but don’t hurt either. Just a bit of regular table salt will do for this.
I don’t know of a direct way like it is done on stack exchange so I took the liberty of doing a work around by editing your opening post. Consider this as an example only and feel free to make whatever changes you wish, including changing it back to the original. After all, it is YOUR post.
Check with your PCB company to find out what they use for Conformal Coating! Before you destroy the PCB.
Different companies use different coatings and don’t bother to inform customers for general electronic gizmos (and, more-so the case with China companies).
This Link for quick learning and This for comparison…
Assuming this is Hobby stuff for you, this may not be of interest…
Examples from experience/lessons learned as Missile Control Systems engineer that required Compliance/Testing to a zillion Mil-Std’s. You wouldn’t think that Oil flowing at high speed through a Teflon lined/StainlessSteel braided hose would ever see what I saw but, x-ray’s revealed ‘lightening strikes’ from ESD through the Teflon along full hose length that caused leaking over time. So, when you say you’re not worried about trace width, gap and arching, well, might not be a problem but, I won’t hire you.
Sure, you may not need to worry about it but, it’s natural for me to focus on all aspects of what I design… so, just passing along info.
Chemical, Water, Cleaning Agent compatibility:
• softened the coating and remained soft/gummy
• dissolved the coating
• ingress into edges of pcb caused delamination and shorting
• trace/pad lifting
Not to mention Silkscreen bleeding, distortion…
Happens once on a $5 board with $50 in parts and you won’t forget!
I have never been into military electronics, but I understand that the Vietnam war demonstrated that (I think it was pcb spacings) deemed adequate proved not to be so under conditions of tropical heat + humidity with applied voltage. They developed copper whiskers which shorted out after time.
Right now I am doing a design using a FET in a fairly new 2mm square SMT package. The FET is rated for 60V (another similar one is rated for 100V) and the pad spacing under the FET body I think is 0.35 mm for this voltage. I am suspecting that this might not pass all military standards, although I am not designing military…
I shouldn’t post this… It could quickly traverse into personal opinions. Opinions are good but, mostly good ‘only’ if coming from experience of having done ‘it’ (whatever the ‘it’ is) and/or learning from the experience of others.
The majority of technology we enjoy today grew out of Military funding of Science. We would not have iPhones today were it not for that. Extreme test conditions led to robust engineering design.
A simple example is splicing two wires together. Below image from the $15 book at Amazon, “‘Basic Electricity’, prepared by Bureau Of Naval Personal’” shows how to Splice. Which involved an amount of testing that today’s engineers have no clue about.
I’ll leave my opinions there except to add that the gap dimension of 0.3mm, I pointed out above, is close to the thickness of a Human Hair. Under 50mA @ 5vdc, in standard conditions, perhaps not a problem. But, prove it to me after tests like: Salt-Fog, Radiation Bombardment, Extreme Temp’s/Humidity and a host of Mechanical and Vibration Stress testing. Those airplanes we fly on aren’t falling from the sky for a reason…
The book is outdated, of course but worth the price of admission to the movie, so to speak…
I pulled a 20 yr old Professionally made PCB from my bin and put it under the microscope.
You can’t see it with a triplet Jewelers mag but, under the scope, take a look at the image below… a shard between two Pads… And, this board was cleaned at the Fab house and cleaned by me before adding RJ11 conc to it…
Have you ever experienced shorting on your PCBs? I guess you might only get shorts if you have close together contacts like in my case with the SSOP footprint.
I bought some MG Chemicals brand PCB cleaner at my local electronic supply store that seemed to do the job, not sure if it’s the same stuff.
I once had a short on a matrix board.
The cheap green ones from Ali with plated through holes and solder mask.
Apparently a hair had drifted onto the PCB during the production process, and copper was not etched under it, which shorted 7 or so pads together.
It was very hard to see, as the line was very thin, and also hidden under the solder mask.
Perhaps your book is not so out of date.
Stripping insulation from wire the “right” way is the only permissible way when laying mains wire inside walls of buildings where I live.
and I wish you wouldn’t brag about measuring the width of the hair from your head…If only I had some left to measure
or was it one that fell out
