On 10/01/14 07:44,
richanny@... wrote:
>
>
> Using plain hydrated ferric chloride etch, warmed up a little, the last two
> boards done have been really stubborn to etch away the bridges between narrow
> tracks and pads. They needed extended time , so much that some narrow tracks
> just disappeared under the resist, and the boards scrapped.
>
> Any suggestions?
The ferric chloride should be diluted 1:1 with water and have some (like 1-5%)
HCl added. For best results, use bubble agitation and keep the etchant covered
when finished. Adding a bit of HCl every few months will make it etch well for a
very long time (i'm using the same tank full from a few years ago).
Stubborn etching can mean some UV is getting through the ink.
Either reduce the exposure time, or better still (i found) is develop the board
in weak NaOH stripper. First put the exposed board in a tray of warm water, then
add some 10% conc. NaOH while sloshing. Continue sloshing or brushing over with
a paint brush for a minute or two. If there's no change, add more NaOH and
repeat until the unexposed resist is properly removed, then rinse in water. It
gives an excellent result for over-exposed boards.