What is the best method, for a small office, for cleaning batches of maybe 50-100 small PCBs? I'm making small runs of PCBs with a lot of big through hole joints, so they come out basically covered in flux. Cleaning them by hand takes far too much time. Does anyone have experience with a specific method that works well for lots of boards, but isn't terribly expensive? Maybe an ultrasonic cleaner with a specific solution?

 

If you use a water soluble flux, then a dishwasher works well.

 

I recently heard of someone cleaning boards in a warm crockpot with DI water. Not sure how well it worked.

I’d only advise dishwasher of your home if you are truly lead free.

 

Maybe an ultrasonic cleaner with a specific solution?

That's what I use successfully. Ultrasonic cleaner, warmed to 50C and undiluted mineral spirits solution (or paint thinner, it's cheaper, or charcoal grille fluid, which is kerosene).

 

Dishwasher is an interesting idea, but not going to use the kitchen one and don't make enough boards to justify a separate one.

For Kerosene, mineral spirits, etc.. what is your second wash with to get rid of the residue from the solvent?

I tried denatured alcohol and a brush in a bowl, but after less than 20 boards there is enough flux in the alcohol that it starts leaving a waxy film on the boards when it dries. CRC aerosol contact cleaner works great and leaves the boards really clean, but is very expensive.

 

For Kerosene, mineral spirits, etc.. what is your second wash with to get rid of the residue from the solvent?

Plain water (well I have a reverse osmosis tap, so really clean plain water). If the boards are taken out immediately after the ultrasonic cycle all the gunk is suspended in the cleaning solution. After a rinse with water and drying they look pretty clean.

If your cleaning solution is really dirty from flux, you'll need to run it a second time, and then wash. If you are doing many batches, filling it up with 2 gallons of solvent each time can get expensive. You'd probably want to make some filtration system.