Which applications would you specifically not use no clean flux. This is typical no clean flux in SAC305 or other lead free solder for SMT assembly. Assume the board is packaged in a plastic enclosure with a tight fit but not air or water tight. matchbox size.
Min current in any node is hundreds of uA with at least 5V - 50V driving it. so I would say 100K max node resistance.
1) where the board could be exposed dusty environments?2) high temperature environments (125C) could the flux stay active and corrode the copper in the board or terminals on typical fine pitched or small electronics.
3) high humidity. Form corrosive compounds with water vaper in the air? leakage currents?I've never used no clean flux and have not tested it. Just getting your experience. Is No clean flux approved for military applications that will see high temperature and humidity? (125C)
the good news for my application is it only needs to last a short period of time when active. single day or so. so long term failure modes caused by heat or contamination are not a concern. If it takes months at high temp for the flux to etch through copper, I can live with that.