Positive or Negative Photoresist

[marcwolf1960]

Hi. Are you using positive or negative photoresist. And are you exposing where you want the coper to stay.. or exposing where you want to remove it. I have seen some experiments re using paint and burning the paint off using a laser but that tends to leave a lot of copper on the boards.

Many thanks

[hzeller]

I am using the photo resist gel that is exposed where the copper should stay. However the other works as well (but as far as I heard a little less light sensitive). You can choose the mode of exposure with the -i option to the ldgraphy binary.

The laser is not powerful enough to burn away paint, so you can't use it for that, but the photo-resist method is possibly a lot more accurate.

[christianlupus]

@hzeller you are using negative resist then. As far as I have learned, positive resist is inherently more accurate because for the negative resist a local polymerization is triggered by the light. This process might spread out and blur an edge. However this was in a lecture about microprocessing of silicon. So the average size of a pcb is much larger than the problems involved there....

The laser is not powerful enough to burn away paint, so you can't use it for that, but the photo-resist method is possibly a lot more accurate.

You mean any photo-method to be more accurate, right? I am not sure I get the meaning of your statement.