piclist-bounces@mit.edu wrote: > and will be > conformal coated. Normal operating environment will be below > 50% RH, but if it wouldn't take too much more effort from a > PCB design standpoint, I'd like it to be able to work in > condensing humidity for a planned future application. the most important thing when coating is that the surface is clean. You have to be especially mindful of residual flux. This applies to anything you solder by hand with flux/fluxed solder, but also to the misleadingly-named "no-clean" flux. In some cases you do not have to clean it, other times you do. That heavily depends on the manufacturer. If you're doing just a few by hand (as opposed to volume production), get some industrial IPA and a brush. physically scrub the flux off with the IPA + brush, and rinse with warm water (DI preferred). repeat. Dry as appropriate. Oven-dry is one method but i've also used compressed air (I'm sure that's a bad idea but for a few samples you should be able to get away with it) then coat as soon as the board is dry. I like Dip-coating when practical, but that can't always be done easily. Oh, and be careful around connectors. Its easy for the coating to wick up into the contacts. If you have connectors, I'd install the mating plug prior to coating if at all possible. Many coatings come with a UV tracer so when you shine a UV light on them, you can see where it is coated and where you missed a spot. > What specs are out there for the minimum clearance between a > trace attached to the bus and any other trace (e.g. ground or > a small-signal trace)? Do I have to abide by such specs > legally or are they simply guidelines? If they are merely > guidelines, what spacing do people typically use? if you're coating, then you can get away with a little less spacing. I *think* (eg don't take my word for it) that the published spacings are primarily a matter of preventing arcing. >From the IPC-2221 table 6.1, 51V to 100V it recommends 0.13mm spacing for external coated traces, or 0.6mm for external uncoated traces. Inner layers may have even less spacing between traces > Almost all of the specs I've seen so far are from the IEC and > are for AC line voltages. They also references things like > "material class III or IV" or "functional vs. basic > insulation" for which I've not been able to find definitions. here is a basic description of the different insulations: hope that points you in the right direction. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist