Hi all,
I am experiencing a problem when developing a UV-sensitive PCB type AA16, made by CIF, available from RS Components as stock number 159-6057.
I mentioned this in my last post to this group, and have now made an exposure test from 1-10mins just to see more what's going on.
My problem is that it is difficult to remove all of the exposed etch resist layer reliably, at almost every exposure level. I'm using Sodium Metasilicate universal developer, RS stock number 690-849, in a hand-agitated plastic developing tray.
After removing the board's protective film, I notice there is a pattern like wood grain which is visible in the unexposed etch resist layer, which runs across the width of the board.
This pattern remains visible throughout the development, even after 10 minutes of constant agitation at 20'C.
I agitate the board as much as possible while developing it, then rinse the board thoroughly.
Here's a flatbed scan of the developed, but un-etched, boards:
https://www.sendspace.com/file/lr6uay (sorry, scan cropped the bottom board a bit)
And after etching:
https://www.sendspace.com/file/6xi3gw
I wonder whether there is a compatibility issue between the etch resist layer and my choice of developer? Do manufacturers tend to specify a preferred type of developer that works best with their boards?
When I etch the developed board, the remaining grain pattern creates lots of fine hair-like copper traces which interfere with the design.
So, I would be very grateful for any and all suggestions, comments and questions.
Kind regards,
Matt