Homebrew PCBs

----- Original Message ----- 

From: richanny@... 
To: Homebrew_PCBs@yahoogroups.com 
Sent: Friday, January 10, 2014 9:44 AM
Subject: [Homebrew_PCBs] Stubborn ferric chloride etching.


  
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?
*******************************************


Try a fish-tank air-pump to aggitate the solution.

geoff
.

Is it fresh?  Ferric Chloride does get worn out, the more copper it 
takes on, the slower it will work, until eventually you'll be there forever.

I'd suggest you try Cupric Chloride, which is simply HCl and H202 after 
it's etched a board or two and picked up a nice lime green colour.  No 
heating required, you can see through it, re-usable indefinately, just 
add just add a cap or two of H202 (depending on how strong your H202 is) 
when you etch (add and stir before you add the board) and it's good as 
new. Yes for the real deal you should test the specific gravity etc 
etc... but you really really don't need to, just eyeball it, lime green 
good, dark green need peroxide, brown add some HCl too.  Wear eye 
protection in case of accidents, etch outside.

On 10/01/14 09:44, 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?
>
> Has anyone had success with an electrolytic technique?
>
> Rich
>

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.

Try Green TRF by Pulsar pro to protect traces. I use a GPC Creative Laminator instead of a iron but I used a household clothing iron with that etchant to success. A laminator uses the smallest thickness of board thou.



On Thursday, January 9, 2014 8:43 PM, "richanny@..." <richanny@....uk> 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?

Has anyone had success with an electrolytic technique?

Rich

Do you do this after the board has already been developed and dried, 
then hardened, or is this how you do the initial develop?

--Rick

On 1/10/2014 12:26 AM, Russell Shaw wrote:
> 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.

On 11/01/14 03:04, Rick Watson wrote:
> On 1/10/2014 12:26 AM, Russell Shaw wrote:
>> 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.

 > Do you do this after the board has already been developed and dried,
 > then hardened, or is this how you do the initial develop?

It is straight after removing from the exposure light box.

If you've tried developing in the normal developer, then etched the board in 
ferric chloride, and after 15mins found that stubborn copper won't come off due 
to UV leaking through the ink, i have rinsed the board and put it into a tray of 
weak NaOH stripper like i said, got the residual resist removed, then put back 
in the etching tank and ended up with a perfectly saved board.

I usually etch in low-light so that if i needed to do a weak strip, the resist 
is no more exposed than when starting.

I now just develop first-off in weak stripper, because until i fix the printer 
driver in linux that changed and now puts out less ink, all my boards get 
slightly over exposed due to UV getting through the ink.

I've never bothered with a "drying and hardening" step after developing. I just 
rinse the board then put straight in the bubble etcher. 12mins unheated works well.