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We clean populated PCB with alcohol and dry with an air compressor. What is the proper distance and psi to consider when doing this? If we check data sheets for information will this give us an idea.?

Jessie
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    Depends what’s on it. Tall fragile stuff? All SMD low profile? – winny Jun 09 '22 at 18:44
  • Populated and soldered or not soldered yet? – Solar Mike Jun 09 '22 at 19:44
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    get closer until parts fly off, then back off a bit. – Neil_UK Jun 09 '22 at 20:28
  • Parts are not tall. Low surface mount diodes and capacitors – Jessie Jun 09 '22 at 21:01
  • Parts are soldered – Jessie Jun 09 '22 at 21:01
  • [This](https://electronics.stackexchange.com/questions/39220/cleaning-circuits-with-compressed-air?rq=1) similar question attracted some answers with references as to concerns about ESD. Drying is more of a ME problem with velocity, temperature and dew point of concern (and possible contaminants such as compressor oil). If you're trying to quickly dry under BGAs and such like you may need/want to wash over the board with jets of air. – Spehro Pefhany Jun 09 '22 at 21:25
  • I don't see how this is opinion based any more than any other question like "how hot do I heat the boards to reflow them". Even if it lacks details. – Drew Jun 10 '22 at 04:53

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There is no proper psi and distance because these two values are not even remotely close to determining the mechanical loads imposed on the parts. And the parts’ sensitivity to mechanical loads varies a lot.

To have a repeatable process, you can “be reasonable” but don’t let a person hold the nozzle. Replace the extruder head of a 3D printer with a nozzle holder and use some fixed gcode pattern for drying. You’ll have a reproducible process and if there are problems, you can modify the process and ensure it’ll be followed precisely. Instead of a 3D printer you could use most manipulator robot arms – it depends on what’s there room for in your budget.

The bigger concerns are occupational safety and contamination potential. The air should be dried and filtered. The pressure across the nozzle should be such that direct contact of body parts such as hands won’t cause fluid injection injuries. This is a huge problem when the air circuit (pipes and hoses) are not thoroughly dry and the pressures are high. You can get water droplets injected under the skin, or even air injected – bad news. Also eye and hearing protection is mandatory, likely a face shield perhaps too.

Kuba hasn't forgotten Monica
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