@Frank_Herrmann wouldn’t that result in the solder mask being broken along the isolation routes of the signal traces? which may in turn permit air to get in and oxidise some of the traces.
Also you’d end up with the vias being unmasked - again this would cause oxidation unless you later tinned the board.
@Justin_Adie sure, that’s a problem. But after the milling/drilling/solder process you can apply manual a second layer of transparent solder mask / lötstopplack via spray can. I.e. this here: http://www.kontaktchemie.com/koc/KOCproductdetail.csp?division&product=PLASTIK+70&ilang=en&plang=en
@Frank_Herrmann
fair enough. not sure really what advantage this gives overall though. you still have the same issue of having to be very precise on depth to remove the solder mask from the pins/pads. seems easier to coat the board after and either remove by milling or just use a mask during curing.
I bought some 2oz copper FR4 boards the other day to experiment with coming back and milling the pads after applying solder mask. The idea is that with thicker copper on the FR4, you have more copper to work with for milling down into the pad to scrub off the solder mask but leaving the copper (or most of it). When doing chemical processes for circuit boards the 1oz copper is more popular because you have less copper to etch away. With milling, we’re in a different ball game. We could have 10oz copper and be just as happy because we’re milling. Why shouldn’t we be able to mill away paths especially if we’ve done an auto-level so we have accurate depth knowledge of the board?
Question, can you run 2 different milling tools? I want to run a 5mm 2 flute end mill to clear out a big area for isolation between high voltage and low.
Sure. Just change your inflation size to 2.5mm (half your 5mm end mill size) and see what the paths look like.
interesting method being used in this video, using a spring loaded V-Bit to mill away the solder mask on the pads https://youtu.be/7EctuSTL7-w