Cleaning No Clean Flux/Paste Series – Part 3

Q: We clean No-Clean with chemistry. We seem to be in the 25-30% range running close to 150 degrees Fahrenheit. Would you say this is accurate?
A: Yes, I would say this is accurate. We would optimally like to see the concentration run from 13-15%, while getting you the results you’re looking for.
Q: We recently ran a 1000-piece and tested cleanliness after the first 50 boards in an alcohol-type tester. The numbers from the test were low, in fact, they showed a pass, so we never washed the entire order. Now the board we tested has gone white and the customer has refused the balance of the boards. Any ideas?
A: You should have cleaned them. What’s happened is the alcohol has turned the flux white. The reason you have a 0 for the test is because all of the low-residue (No-Clean) that’s left on the board itself has encapsulated the metal salt, so no ionic bleed is visible.
Q: You mentioned a possible test being a visual inspection. We run RF frequency boards. Do you think we can just look at them and determine if they are clean?
A: I wouldn’t. The smallest amount of contamination can interfere tremendously with your RF type application board. What I would do is subject them to a clean and run other testing protocol (Ion Chromatography or SIR Testing).
Q: I clean no cleans all the time but recently I have seen my testing results spike. Any ideas?
A: I would say your chemistry is loaded. If they are loaded, the cleaning efficacy begins to drop off.