You see what I said, twenty wise men will have twenty different answers. I suppose what we have discussed hitherto is commercial/industrial boards. Our MIL/SPACE customers pay such a lot for our boards that they mean, quite frankly, that there shall not be any bubbles at all. Put into practice, nobody will do 100% Inspection at 200 time magnification, especially not in a line that assembles hundreds of boards a day. As said the Cypriot guru : ' use common sense' Inge PS. I forgot to give advice for the situation when common sense does not exist. Maybe someone else can help. On 23 March 2013 08:20, Brian Ellis <[log in to unmask]> wrote: > IMHO, it depends what you mean by bubbles/voids. If they are a result of > humidity being absorbed by hygroscopic contaminants through the coating > (vesication or mealing) then the answer is a resounding 'not acceptable' > under all conditions. > > If they are the result of poor application of a liquid conformal coating > or solder mask, I would say that they would not be acceptable if any of: > 1. the substrate is not wetted under any bubble > 2. a bubble bridges two bare conductors > 3. a bubble occupies more than 30% of the space between two bare > conductors with a potential difference of >10 V > 4. there are more than 2 bubbles per square decimetre on either side, not > counting the edges of a board where there are no conductors, up to 5 mm > from the edge > 5. a void or bubble can be seen by 10 X visual inspection under a component > 6. a paraxylylene coating displays any void > > Some of the numbers in 3., 4. and 5. are arbitrary; common sense should be > applied, along with the coating. > > My 2 eurocents. > > Brian > > > On 21.03.2013 17:18, Douglas Pauls wrote: > >> OK, Minions, your next question in the quest to improve J-STD-001 and >> A-610 relates to bubbles in the conformal coating. >> >> I think we can all agree that the ideal conformal coating layer contains >> no bubbles or voids and is "purdy". BUT: >> >> 1. Are there bubbles in coatings in areas where they will not impact >> reliability and their presence should be viewed as a "Process Indicator"? >> If so, where and what limits would you use? >> >> 2. What would you classify as a bubble requiring disposition, i.e. >> Becomes an actionable defect? If so, where and why? >> >> 3. Would any of your answers change depending on what KIND of coating it >> is, i.e. Acrylic vs. silicone vs. Parylene? >> >> Well, OK, that is three questions. I'm on a roll. >> >> >> Doug Pauls >> Chairman, IPC Cleaning and Coating Committees >> Galactic Emporer >> >> >> >> ______________________________**______________________________** >> __________ >> This email has been scanned by the Symantec Email Security.cloud service. >> For more information please contact helpdesk at x2960 or [log in to unmask] >> ______________________________**______________________________** >> __________ >> >> > ______________________________**______________________________**__________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or [log in to unmask] > **______________________________**__________ > ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________