Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Glad to report that I've had some significant success by changing the UV board type and the developer.

I was experiencing incomplete removal of exposed photoresist layer, when using a combination of CIF's AA16 board (RS 159-6057) and sodium metasilicate universal developer (RS 690-849). Despite a wide range of exposure times and plenty of time in the developer, there was always a fine and laterally-patterned residue of photoresist that refused to dissolve.

After a long chat with Mega UK, they kindly sent me a couple of complimentary Microtrak (mfr = Bungard) pre-sensitised boards to try, and recommended using their Seno 4006 (Mega 600-010) concentrated developer at 1:9 dilution rather than the default 1:19. I also laser printed the artwork onto some LaserStar film using a humble 600dpi HP CP1215 in mono mode, which gave adequate but not quite 100% opacity.

A 5 minute exposure in an LV202E UV box, followed by 2 ~ 2.5 minutes developing in the 1:9 mix, resulted in a very satisfactory etch. Traces of less than 6mil were reproducible, where ground plane polygons had been squeezed very thinly between tracks and 0805 pads. :)

Conclusion:
∗ This combination is problematic: CIF AA16 (RS 159-6057) + developer RS 690-849, at least at the advertised dilution
∗ This combination works: Microtrak (Mega 03-5108-1) + developer (Mega 600-010 @ 1:9 dilution)

Next steps:
I might try another CIF board, but develop it in double strength RS 690-849 developer.

Many thanks for everyone's help and support!

Matt