Intersting finding. I never could observe this! Might depend on the kind
of make/modell of the restist itself?
Markus
Adam Seychell schrieb:
[snip]
>
>
> Also I just discovered the importance of leaving the PCB stand after
> exposure for > 5 minutes. I've read several places that negative
> photoresists continue to polymerise after exposure , and that this
> polymerisation is inhibited by oxygen. So its really important you leave
> the protective polyester cover film on during this hold time. I was
> getting really puzzling results before I realised this. Often I used to
> just develop immediately after exposure, and would find that one side of
> the PCB would appear to be underexposed and get attacked in the
> developer. It turned out to be the short delay differences from exposing
> one side at a time was enough to show the problem. I also found I could
> reduce my exposure from 60 seconds to 30 seconds when the PCB held > 5
> minutes after exposure. The PCB process is much more consistent now.
>
> Adam
>