As a rule, the sooner after reflow you clean a PCB, the easier it is to remove flux and other residues. After cleaning, the PCBs should be allowed to dry completely before any power is applied.
After heat testing, they just need to cool to room temperature before functional test. Unless a second round of cleaning is required after all that testing, there is no reason to wait before conformal coat.
Application Engineering Supervisor
Mr. Vivari has more than 15 years of electronic engineering design and assembly experience. His expertise in fluid dispensing and solder paste technology assists others in identifying the most cost effective method for assembling products.
Typically the only two that are critical are reflow to clean and clean to coating and it depends on what are you cleaning off and how.
President/Senior Technical Consultant
Mr. Munson, President and Founder of Foresite, has extensive electronics industry experience applying Ion Chromatography analytical techniques to a wide spectrum of manufacturing applications.