23-06-2015, 01:54 PM
Interesting - the reason I ask is that the images you posted of the completed boards appear to be "undershot" - that is UV has crept in under the edge of the mask creating a jagged finish...
What a lot of folk tend to do is to print a mirror image of the mask, so that you apply it to the coated PCB INK SIDE DOWN, so the mask is in direct contact with the photo-resist, not via one or more thicknesses of acetate.
The mask is then pressed to the board with a sheet of glass (not plastic).
Doing it this way results in far finer edges to the finished board, with consequential greater overall accuracy due to lack of any parallax error. This is what I always did (never used multiple layers) - I used to be able to do 10mil feature boards with ease.
Eagle and I presume other PCB packages have this feature as an output option for exactly the reasons mentioned - otherwise you can take the image and flip it in MS Paint or similar...
HTH
What a lot of folk tend to do is to print a mirror image of the mask, so that you apply it to the coated PCB INK SIDE DOWN, so the mask is in direct contact with the photo-resist, not via one or more thicknesses of acetate.
The mask is then pressed to the board with a sheet of glass (not plastic).
Doing it this way results in far finer edges to the finished board, with consequential greater overall accuracy due to lack of any parallax error. This is what I always did (never used multiple layers) - I used to be able to do 10mil feature boards with ease.
Eagle and I presume other PCB packages have this feature as an output option for exactly the reasons mentioned - otherwise you can take the image and flip it in MS Paint or similar...
HTH
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