The main circuit board on my tractor is filthy. It is full of grass, dirt and debris. I want to clean it . I gave it a few shots with compressed air but it is still grimy. If I remove it how can I safely deep clean it?
Dampen a cotton swab with isopropyl alcohol. You should use isopropyl alcohol that is at least 90%-100% alcohol. ...
Brush the cotton swab across the grime to dislodge it. ...
Allow the alcohol to dry. ...
Use compressed air to blow away any dislodged grime.
We'd need GOOD pics of the board to see what components are on it.
"Most" don't mind getting wet, but some do.
"Some" of those that mind, can be covered.
"IF" you can't get it wet then you need to use electrical contact cleaner after the initial prep steps of getting the majority of the big particles off.
"IF" it has an EPROM you need to be careful about stray ESD using a brish.
"IF NOT", you can use a dry brush to first get off the bulk of the material.
"IF" the board can get wet, you can use hot, strong, detergent solution and submerge the board and use a soft bristled (paint, etc) brush to dislodge gunk. If it's can't get wet, you'll be doing that with residue-free electrical contact cleaner.
"IF" the grime is only cosmetic except for the the electrical contacts to wiring harness, you may not even need to get the whole board clean, just those electrical contacts. How to clean those depends on whether they are gold or silver plated and just need grime cleaned off, or tin with a median amount of oxidation, or brass with a lot of it. Tin can usually be cleaned with a paper towel/etc and contact cleaner. Brass needs a brass cleaner then a rinse if it leaves behind an anti-oxidative film, or abrasion cleaning if it is more readily exposed to facilitate that.
Relays, if not sealed, should not be allowed to get contact cleaner inside unless it is a last ditch effort because they are shorting out and you need to use the equipment prior to having a chance to replace the relay. Relays that are sealed but have a breather hole covered with tape, might have the tap fall off if sprayed with contact cleaner. Worse things can happen but it is best not to get any inside.
If it's a full blown mainboard with a computer real time clock, the battery should be removed prior to exposure to water. Any socketed chips should be removed, following ESD safe procedures, before cleaning then reinserted after the board is dry.
After a detergent wash you can rinse with water that has alcohol in it to break the surface tension, or a drop of dishwashing machine rinse agent to break the tension, or worse case shaken gently, then blown dry. If it is a modern construction using water soluble flux, do not let pools of dissolved flux sit in any area while it dries as they can cause corrosion and short circuits.
If it has rosin core flux residue left behind and you use alcohol, then you should similarly make sure there are no pools of that muck left behind unless it is very hard from old age, not flowing anywhere.
Be very careful with compressed air, that velocity is not really needed and if the board flexes too much you risk breaking solder joints or components, depending on what's on it.
The next consideration is why it got so filthy. Does it have passive heatsinks and needs airflow to stay cool enough or was it just a substandard job sealing it from the elements? You might see whether you can improve that.
That's about it, I shouldn't have written this much before seeing pics.
I can't get a pic. But if you google John Deere AM 132500 Ignition module you can see it. And these boards are subject to lots of moisture.
Wash it with water and a toothbrush in a sink. Dry completely before reinstalling. However, if those rectangles are relays I would keep the water away from those or use another method. The bottom of the board I would be OK with water and a toothbrush. I suspect that the dirtiest part is the top part though.
A modern board with ball grid array ICs will not like water. It will trap water between the contacts under the chip. Ideally and ultrasonic cleaning bath, but if that isn't an option, place the board on a grounded mat, then flux remover spray or 97% isopropyl alcohol and a soft horsehair brush work your way through it. Then thoroughly flush with the same cleaner numerous times. Tracks of dirt or carbon can play havoc with data being transmitted around the board. Gently blow dry it with computer duster spray or ionized air.
There is a really good photo here:
CLEARLY, there is some type of "clear-coat" water resistant coating to protect the components soldered to the board.
i agree - - do not get any water into the relays (black cubes)