Homebrew PCBs

Hi,

I am trying to etch a small PCB and finding it etches unevenly leaving a small area of copper which is stubborn to remove. Just leaving in the etchant for longer starts to undermine the tracks that etched ok.

Here's what I do:

1. Print the track layout on inkjet printer using transparency film.

2. Lay the film ink side down onto a 3" x 2" single sided photo resist coated copper clad board (cut from a Maplin Size 4 ref KU14)

3. Expose in a home made LED Light box for 4 minutes

4. Develop in Universal Developer (PBD2) Sodium Metasilicate for 1 minute.

5. Etch in Ferric Chloride track side down for 16 mins, agitating every minute or so.

The result is most of the copper dissolves after 10 mins then it leaves a small area which refuses to disappear after waiting a further 5 minutes.

A photo of the etched board is here

https://picasaweb.google.com/109391378120539635298

On close inspection of the board the unetched copper is left as stripes. So I am wondering if this is a board problem or the process.

Any help is appreciated.

Thanks
Pete

I'd say a process problem.  Agitate more often and more vigourously. The stripes are from the glass beneath the copper - the copper I believe is slightly thinner over the glass strands so etches faster than the slightly thicker copper surrounding it.

Try continuous agitation (rocking the tray) and warm FeCl (it will etch faster than 16 min) and see what happens.

HTH,
Donald.
--
*Plain Text* email -- it's an accessibility issue
()  no proprietary attachments; no html mail
/\  ascii ribbon campaign - <www.asciiribbon.org>

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

> From: "Pete" <pete@...>
> To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
> Sent: Sunday, March 4, 2012 5:45:40 PM
> Subject: [Homebrew_PCBs] Etching problem - Help please
> Hi,
> 
> I am trying to etch a small PCB and finding it etches unevenly leaving
> a small area of copper which is stubborn to remove. Just leaving in
> the etchant for longer starts to undermine the tracks that etched ok.
> 
> Here's what I do:
> 
> 1. Print the track layout on inkjet printer using transparency film.
> 
> 2. Lay the film ink side down onto a 3" x 2" single sided photo resist
> coated copper clad board (cut from a Maplin Size 4 ref KU14)
> 
> 3. Expose in a home made LED Light box for 4 minutes
> 
> 4. Develop in Universal Developer (PBD2) Sodium Metasilicate for 1
> minute.
> 
> 5. Etch in Ferric Chloride track side down for 16 mins, agitating
> every minute or so.
> 
> The result is most of the copper dissolves after 10 mins then it
> leaves a small area which refuses to disappear after waiting a further
> 5 minutes.
> 
> A photo of the etched board is here
> 
> https://picasaweb.google.com/109391378120539635298
> 
> On close inspection of the board the unetched copper is left as
> stripes. So I am wondering if this is a board problem or the process.
> 
> Any help is appreciated.
> 
> Thanks
> Pete
> 
> 
> 
> 
> 
> ------------------------------------
> 
> Be sure to visit the group home and check for new Links, Files, and
> Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
> 
> 
>

I've also seen this exact problem from under exposure.
If possible agitate / rotate board (or leds) during exposure, to ensure 
even coverage. You may need to experiment with exposure times more, I 
had to do this quite a bit with my home made uv ccfl box.

As a last resort, when you get to a stage of only having a little bit of 
copper left on an open area you can spot-etch it:
Pull the board out of the etchant and give it a rinse.
Put on rubber gloves and dip a bit of sponge into the etchant, then just 
wipe that gently and repeatedly over just the under etched area to 
finish it off. Alternately you gan buy a sponge-on-a-stick from a craft 
or paint supply store, hardware stores often have them under painting, etc.

Andrew

On 5/03/2012 1:53 PM, Donald H Locker wrote:
>
> I'd say a process problem. Agitate more often and more vigourously. 
> The stripes are from the glass beneath the copper - the copper I 
> believe is slightly thinner over the glass strands so etches faster 
> than the slightly thicker copper surrounding it.
>
> Try continuous agitation (rocking the tray) and warm FeCl (it will 
> etch faster than 16 min) and see what happens.
>
> HTH,
> Donald.
> --
> *Plain Text* email -- it's an accessibility issue
> () no proprietary attachments; no html mail
> /\ ascii ribbon campaign - <www.asciiribbon.org>
>
> ----- Original Message -----
> > From: "Pete" <pete@... 
> <mailto:pete%40ridcom.fsnet.co.uk>>
> > To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com 
> <mailto:Homebrew_PCBs%40yahoogroups.com>>
> > Sent: Sunday, March 4, 2012 5:45:40 PM
> > Subject: [Homebrew_PCBs] Etching problem - Help please
> > Hi,
> >
> > I am trying to etch a small PCB and finding it etches unevenly leaving
> > a small area of copper which is stubborn to remove. Just leaving in
> > the etchant for longer starts to undermine the tracks that etched ok.
> >
> > Here's what I do:
> >
> > 1. Print the track layout on inkjet printer using transparency film.
> >
> > 2. Lay the film ink side down onto a 3" x 2" single sided photo resist
> > coated copper clad board (cut from a Maplin Size 4 ref KU14)
> >
> > 3. Expose in a home made LED Light box for 4 minutes
> >
> > 4. Develop in Universal Developer (PBD2) Sodium Metasilicate for 1
> > minute.
> >
> > 5. Etch in Ferric Chloride track side down for 16 mins, agitating
> > every minute or so.
> >
> > The result is most of the copper dissolves after 10 mins then it
> > leaves a small area which refuses to disappear after waiting a further
> > 5 minutes.
> >
> > A photo of the etched board is here
> >
> > https://picasaweb.google.com/109391378120539635298
> >
> > On close inspection of the board the unetched copper is left as
> > stripes. So I am wondering if this is a board problem or the process.
> >
> > Any help is appreciated.
> >
> > Thanks
> > Pete
> >
> >
> >
>



[Non-text portions of this message have been removed]

As mentioned by Donald, heating your etchant helps a lot. I've lost the
link, but there was a white paper published by some company that suggested
that heating improves your speed without significantly increasing your
undercutting.  Whereas agitating more causes more undercutting.

You could also choose to agitate certain areas more. I'm working on a
bubbler that has four different sections, each controlled by a different
valve. That way you can target the areas with more copper.

Sent from my iPad

On 2012-03-04, at 8:20 PM, Andrew Leech <coronasensei@...> wrote:



I've also seen this exact problem from under exposure.
If possible agitate / rotate board (or leds) during exposure, to ensure
even coverage. You may need to experiment with exposure times more, I
had to do this quite a bit with my home made uv ccfl box.

As a last resort, when you get to a stage of only having a little bit of
copper left on an open area you can spot-etch it:
Pull the board out of the etchant and give it a rinse.
Put on rubber gloves and dip a bit of sponge into the etchant, then just
wipe that gently and repeatedly over just the under etched area to
finish it off. Alternately you gan buy a sponge-on-a-stick from a craft
or paint supply store, hardware stores often have them under painting, etc.

Andrew

On 5/03/2012 1:53 PM, Donald H Locker wrote:
>
> I'd say a process problem. Agitate more often and more vigourously.
> The stripes are from the glass beneath the copper - the copper I
> believe is slightly thinner over the glass strands so etches faster
> than the slightly thicker copper surrounding it.
>
> Try continuous agitation (rocking the tray) and warm FeCl (it will
> etch faster than 16 min) and see what happens.
>
> HTH,
> Donald.
> --
> *Plain Text* email -- it's an accessibility issue
> () no proprietary attachments; no html mail
> /\ ascii ribbon campaign - <www.asciiribbon.org>
>
> ----- Original Message -----
> > From: "Pete" <pete@...
> <mailto:pete%40ridcom.fsnet.co.uk>>
> > To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com
> <mailto:Homebrew_PCBs%40yahoogroups.com>>
> > Sent: Sunday, March 4, 2012 5:45:40 PM
> > Subject: [Homebrew_PCBs] Etching problem - Help please
> > Hi,
> >
> > I am trying to etch a small PCB and finding it etches unevenly leaving
> > a small area of copper which is stubborn to remove. Just leaving in
> > the etchant for longer starts to undermine the tracks that etched ok.
> >
> > Here's what I do:
> >
> > 1. Print the track layout on inkjet printer using transparency film.
> >
> > 2. Lay the film ink side down onto a 3" x 2" single sided photo resist
> > coated copper clad board (cut from a Maplin Size 4 ref KU14)
> >
> > 3. Expose in a home made LED Light box for 4 minutes
> >
> > 4. Develop in Universal Developer (PBD2) Sodium Metasilicate for 1
> > minute.
> >
> > 5. Etch in Ferric Chloride track side down for 16 mins, agitating
> > every minute or so.
> >
> > The result is most of the copper dissolves after 10 mins then it
> > leaves a small area which refuses to disappear after waiting a further
> > 5 minutes.
> >
> > A photo of the etched board is here
> >
> > https://picasaweb.google.com/109391378120539635298
> >
> > On close inspection of the board the unetched copper is left as
> > stripes. So I am wondering if this is a board problem or the process.
> >
> > Any help is appreciated.
> >
> > Thanks
> > Pete
> >
> >
> >
>

[Non-text portions of this message have been removed]

 


[Non-text portions of this message have been removed]

Try etching it face up...instead of face down. Etches much cleaner. brush it lightly with a nylon (white brisel ) paint brush after about 15 minutes and you should be about there.
Terry
 


________________________________

From: Donald H Locker <dhlocker@...>
To: Homebrew PCBs <Homebrew_PCBs@yahoogroups.com> 
Sent: Sunday, March 4, 2012 9:53 PM
Subject: Re: [Homebrew_PCBs] Etching problem - Help please


  
I'd say a process problem. Agitate more often and more vigourously. The stripes are from the glass beneath the copper - the copper I believe is slightly thinner over the glass strands so etches faster than the slightly thicker copper surrounding it.

Try continuous agitation (rocking the tray) and warm FeCl (it will etch faster than 16 min) and see what happens.

HTH,
Donald.
--
*Plain Text* email -- it's an accessibility issue
() no proprietary attachments; no html mail
/\ ascii ribbon campaign - <www.asciiribbon.org>

----- Original Message -----
> From: "Pete" <pete@...>
> To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
> Sent: Sunday, March 4, 2012 5:45:40 PM
> Subject: [Homebrew_PCBs] Etching problem - Help please
> Hi,
> 
> I am trying to etch a small PCB and finding it etches unevenly leaving
> a small area of copper which is stubborn to remove. Just leaving in
> the etchant for longer starts to undermine the tracks that etched ok.
> 
> Here's what I do:
> 
> 1. Print the track layout on inkjet printer using transparency film.
> 
> 2. Lay the film ink side down onto a 3" x 2" single sided photo resist
> coated copper clad board (cut from a Maplin Size 4 ref KU14)
> 
> 3. Expose in a home made LED Light box for 4 minutes
> 
> 4. Develop in Universal Developer (PBD2) Sodium Metasilicate for 1
> minute.
> 
> 5. Etch in Ferric Chloride track side down for 16 mins, agitating
> every minute or so.
> 
> The result is most of the copper dissolves after 10 mins then it
> leaves a small area which refuses to disappear after waiting a further
> 5 minutes.
> 
> A photo of the etched board is here
> 
> https://picasaweb.google.com/109391378120539635298
> 
> On close inspection of the board the unetched copper is left as
> stripes. So I am wondering if this is a board problem or the process.
> 
> Any help is appreciated.
> 
> Thanks
> Pete
> 
> 
> 
> 
> 
> ------------------------------------
> 
> Be sure to visit the group home and check for new Links, Files, and
> Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
> 
> 
> 



[Non-text portions of this message have been removed]

Pete

I would suggest that you are not removing all the resist when you develop your board, they need longer and a good spray rinse. I get similar islands due to finger grease when I use toner transfer. I remove the board, rinse and scratch at the stubborn area with a blade, then back in the etch.


Malcolm
 
I don't suffer from insanity I enjoy it!
Mene, mene, tekel, upharsin
The writing is on the wall.


________________________________

 From: Pete <pete@...>
To: Homebrew_PCBs@yahoogroups.com 
Sent: Sunday, March 4, 2012 10:45 PM
Subject: [Homebrew_PCBs] Etching problem - Help please
 

  
Hi,

I am trying to etch a small PCB and finding it etches unevenly leaving a small area of copper which is stubborn to remove. Just leaving in the etchant for longer starts to undermine the tracks that etched ok.

Here's what I do:

1. Print the track layout on inkjet printer using transparency film.

2. Lay the film ink side down onto a 3" x 2" single sided photo resist coated copper clad board (cut from a Maplin Size 4 ref KU14)

3. Expose in a home made LED Light box for 4 minutes

4. Develop in Universal Developer (PBD2) Sodium Metasilicate for 1 minute.

5. Etch in Ferric Chloride track side down for 16 mins, agitating every minute or so.

The result is most of the copper dissolves after 10 mins then it leaves a small area which refuses to disappear after waiting a further 5 minutes.

A photo of the etched board is here

https://picasaweb.google.com/109391378120539635298

On close inspection of the board the unetched copper is left as stripes. So I am wondering if this is a board problem or the process.

Any help is appreciated.

Thanks
Pete


 

[Non-text portions of this message have been removed]

On 04/03/2012 22:45, Pete wrote:
> Hi,
>
> I am trying to etch a small PCB and finding it etches unevenly leaving a
> small area of copper which is stubborn to remove. Just leaving in the
> etchant for longer starts to undermine the tracks that etched ok.

Try continuous agitation (I rock the container) in heated etchant. I put 
the small plastic container I use for etching in an outer container of 
very hot (just boiled) water. I wear rubber gloves, of course. Brushing 
the surface of the board with a soft brush is another technique. My 
technique takes about 5 minutes to etch a board.

Leon
-- 
Leon Heller
G1HSM

I presume this is positive photoresist, in which case it looks like either
over exposure or transparencies that are not dense enough.  Try adjust you
exposure a bit or double up on your transparencies if possible.

On Mon, Mar 5, 2012 at 12:45 AM, Pete <pete@...> wrote:

> **
>
>
> Hi,
>
> I am trying to etch a small PCB and finding it etches unevenly leaving a
> small area of copper which is stubborn to remove. Just leaving in the
> etchant for longer starts to undermine the tracks that etched ok.
>
> Here's what I do:
>
> 1. Print the track layout on inkjet printer using transparency film.
>
> 2. Lay the film ink side down onto a 3" x 2" single sided photo resist
> coated copper clad board (cut from a Maplin Size 4 ref KU14)
>
> 3. Expose in a home made LED Light box for 4 minutes
>
> 4. Develop in Universal Developer (PBD2) Sodium Metasilicate for 1 minute.
>
> 5. Etch in Ferric Chloride track side down for 16 mins, agitating every
> minute or so.
>
> The result is most of the copper dissolves after 10 mins then it leaves a
> small area which refuses to disappear after waiting a further 5 minutes.
>
> A photo of the etched board is here
>
> https://picasaweb.google.com/109391378120539635298
>
> On close inspection of the board the unetched copper is left as stripes.
> So I am wondering if this is a board problem or the process.
>
> Any help is appreciated.
>
> Thanks
> Pete
>
>  
>


[Non-text portions of this message have been removed]

Apologies to the O.P. I missed the exposed resist and was thinking toner transfer.

Donald.
--
*Plain Text* email -- it's an accessibility issue
()  no proprietary attachments; no html mail
/\  ascii ribbon campaign - <www.asciiribbon.org>

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

> From: "Eddie Stassen" <estassen@...>
> To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
> Sent: Monday, March 5, 2012 6:01:43 AM
> Subject: Re: [Homebrew_PCBs] Etching problem - Help please
> I presume this is positive photoresist, in which case it looks like either
> over exposure or transparencies that are not dense enough. Try adjust you
> exposure a bit or double up on your transparencies if possible.
> 
> On Mon, Mar 5, 2012 at 12:45 AM, Pete <pete@...> wrote:
> 
> > **
> >
> >
> > Hi,
> >
> > I am trying to etch a small PCB and finding it etches unevenly
> > leaving a
> > small area of copper which is stubborn to remove. Just leaving in
> > the
> > etchant for longer starts to undermine the tracks that etched ok.
> >
> > Here's what I do:
> >
> > 1. Print the track layout on inkjet printer using transparency film.
> >
> > 2. Lay the film ink side down onto a 3" x 2" single sided photo
> > resist
> > coated copper clad board (cut from a Maplin Size 4 ref KU14)
> >
> > 3. Expose in a home made LED Light box for 4 minutes
> >
> > 4. Develop in Universal Developer (PBD2) Sodium Metasilicate for 1
> > minute.
> >
> > 5. Etch in Ferric Chloride track side down for 16 mins, agitating
> > every
> > minute or so.
> >
> > The result is most of the copper dissolves after 10 mins then it
> > leaves a
> > small area which refuses to disappear after waiting a further 5
> > minutes.
> >
> > A photo of the etched board is here
> >
> > https://picasaweb.google.com/109391378120539635298
> >
> > On close inspection of the board the unetched copper is left as
> > stripes.
> > So I am wondering if this is a board problem or the process.
> >
> > Any help is appreciated.
> >
> > Thanks
> > Pete
> >
> >
> >
> 
> 
> [Non-text portions of this message have been removed]
> 
> 
> 
> ------------------------------------
> 
> Be sure to visit the group home and check for new Links, Files, and
> Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
> 
> 
>

Hi Pete

Are you are buying your pre-sensitised board from Maplin? Particularly 
from a store rather than mail-order? The only major problem I have had 
has been with board bought from a Maplin store.

I normally buy board from Mega Electronics and was getting quite blase. 
Exposure time (4 mins) always gave consistent good results. Then I 
bought some Maplin board, exposed it in the same way, and had results 
very similar to yours. I guess the stores don't sell much pre-sensitised 
board and it may have been on the shelf for a long time?

I do still buy board from Maplin. There is a store just a few miles away 
and so it is very convienient if I only need small quantities. But I 
always run a test strip to determine the optimum exposure for each batch.

Regards

Paul

On Mon, Mar 5, 2012 at 12:45 AM, Pete <pete@...> wrote:
>> **
>>
>>
>> Hi,
>>
>> I am trying to etch a small PCB and finding it etches unevenly leaving a
>> small area of copper which is stubborn to remove. Just leaving in the
>> etchant for longer starts to undermine the tracks that etched ok.
>>
>> Here's what I do:
>>
>> 1. Print the track layout on inkjet printer using transparency film.
>>
>> 2. Lay the film ink side down onto a 3" x 2" single sided photo resist
>> coated copper clad board (cut from a Maplin Size 4 ref KU14)
>>
>> 3. Expose in a home made LED Light box for 4 minutes
>>
>> 4. Develop in Universal Developer (PBD2) Sodium Metasilicate for 1 minute.
>>
>> 5. Etch in Ferric Chloride track side down for 16 mins, agitating every
>> minute or so.
>>
>> The result is most of the copper dissolves after 10 mins then it leaves a
>> small area which refuses to disappear after waiting a further 5 minutes.
>>
>> A photo of the etched board is here
>>
>> https://picasaweb.google.com/109391378120539635298
>>
>> On close inspection of the board the unetched copper is left as stripes.
>> So I am wondering if this is a board problem or the process.
>>
>> Any help is appreciated.
>>
>> Thanks
>> Pete
>>
>>
>>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
>

On 05/03/2012 12:51, Paul Whatton wrote:
> Hi Pete
>
> Are you are buying your pre-sensitised board from Maplin? Particularly
> from a store rather than mail-order? The only major problem I have had
> has been with board bought from a Maplin store.
>
> I normally buy board from Mega Electronics and was getting quite blase.
> Exposure time (4 mins) always gave consistent good results. Then I
> bought some Maplin board, exposed it in the same way, and had results
> very similar to yours. I guess the stores don't sell much pre-sensitised
> board and it may have been on the shelf for a long time?

I use Mega Electronics boards, and they seem to go off after about six 
months or so.

Leon
-- 
Leon Heller
G1HSM

Thanks for the advice folks, a great response to my question and all  much appreciated.

I'll do some more trials and report back soon.

Thanks
Pete

--- In Homebrew_PCBs@yahoogroups.com, "Pete" <pete@...> wrote:

>
> Hi,
> 
> I am trying to etch a small PCB and finding it etches unevenly leaving a small area of copper which is stubborn to remove. Just leaving in the etchant for longer starts to undermine the tracks that etched ok.
> 
> Here's what I do:
> 
> 1. Print the track layout on inkjet printer using transparency film.
> 
> 2. Lay the film ink side down onto a 3" x 2" single sided photo resist coated copper clad board (cut from a Maplin Size 4 ref KU14)
> 
> 3. Expose in a home made LED Light box for 4 minutes
> 
> 4. Develop in Universal Developer (PBD2) Sodium Metasilicate for 1 minute.
> 
> 5. Etch in Ferric Chloride track side down for 16 mins, agitating every minute or so.
> 
> The result is most of the copper dissolves after 10 mins then it leaves a small area which refuses to disappear after waiting a further 5 minutes.
> 
> A photo of the etched board is here
> 
> https://picasaweb.google.com/109391378120539635298
> 
> On close inspection of the board the unetched copper is left as stripes. So I am wondering if this is a board problem or the process.
> 
> Any help is appreciated.
> 
> Thanks
> Pete
>

I just started doing toner transfer this week after having used a different process for a few years that required too many setup steps.  While waiting for my Pulsar Toner Transfer Paper to show up from Mouser, I tried some paper from Staples that was suggested on this list a number of months ago.

My laser printer is also one of the highly-regarded printers for this, the LaserJet Pro hp1525.  I'm doing double-sided 1/16" 1/2oz double-sided 4x6" boards.  My traces are all around 16mil.  I scrub the board with green Scotch-Brite or 0000 steel wool, and then wipe off with an old T-shirt and IPA.

I initially used a friend's off-the-shelf Scotch or 3M laminator for a few tries and found that it didn't get hot enough to stick the toner onto the board without peeling off some of the toner during the paper soak/removal.

I then tried a regular $20 Black and Decker hand iron with no water in it on its highest setting for 3 minutes.  I found that the heat adhered both the toner as well as the glossy coating on the paper to the board.  It also caused the toner to pancake-out -- almost certainly due to too much heat.  It additionally made paper removal all but impossible.

One by one I decreased the heat setting on the iron from 7 down to 3 on successive boards, and decreased ironing time to 1 minute per side with pretty good pressure and that appeared to work perfectly.  I let the paper soak for an hour before trying to remove it, but I'm guessing that 2-3 minutes would have been enough.  The paper slid pretty much entirely off without having to touch it.  The detail and sharpness was comparable to the original paper print after the transfer was complete.

When I laid out the paper print I did so such that the front and back designs faced each other along one axis and added fiducials on opposite corners to facilitate alignment.  This enabled me to line-up the top and bottom layers by folding the paper over on itself while holding it up to a light and creasing it along its common edge.  I slipped the board in between the two layers and initially taped-down one opposite edge.  I then flipped it over and after tensioning, taped-down the other side's crease-opposing edge.

I just got done etching it an hour ago and it etched perfectly.  Front to back registration was perfect.

It has worked out well enough that I don't think that I'll even need my Pulsar TTF and TRF, but I may break into it if I need to once I attempt 8-10mil.  For the time being, I don't feel like I need to fork out the $90 for the GBC(?) laminator.

I also happen to use 0.8mm drill holes for DIP/header pins as well as vias (the latter which could be smaller if I chose to swap bits).  If you use a low-speed drill, you're much more likely to rip off the copper around the hole, so you really want something high-speed like a Dremel, all other things being equal.

-ebw

Hi All,

As promised I am posting the conclusion to the etch problem I request help for and for which I received many suggestions.

I can now etch the boards without problems and get repeatably good results.

Here's what I did to improve the process.

1. Increased the exposure time in the UV LED Box from 4 mins to 5 mins as well as reducing the inter LED matrix spacings from 25mm to 12.5 mm. The LEDs are 3 inches from the board and originally illuminated as spots of light, they now give a more even illumination.

2. Kept the universal developer time the same ie 1 min

3. Spray with a small pressure spray and clean water.

4. Etch in hot Ferric Choride and use a small nylon toothbrush to  scrub the last few spots of copper. Most of the copper is cleared after 8 mins with the remainder clearing after 10mins when using fresh etchant.

The result is a perfectly etched board with sharp tracks even etch and no traces of copper residue.

Many thanks for all your suggestions,

Pete








--- In Homebrew_PCBs@yahoogroups.com, "Pete" <pete@...> wrote:

>
> Hi,
> 
> I am trying to etch a small PCB and finding it etches unevenly leaving a small area of copper which is stubborn to remove. Just leaving in the etchant for longer starts to undermine the tracks that etched ok.
> 
> Here's what I do:
> 
> 1. Print the track layout on inkjet printer using transparency film.
> 
> 2. Lay the film ink side down onto a 3" x 2" single sided photo resist coated copper clad board (cut from a Maplin Size 4 ref KU14)
> 
> 3. Expose in a home made LED Light box for 4 minutes
> 
> 4. Develop in Universal Developer (PBD2) Sodium Metasilicate for 1 minute.
> 
> 5. Etch in Ferric Chloride track side down for 16 mins, agitating every minute or so.
> 
> The result is most of the copper dissolves after 10 mins then it leaves a small area which refuses to disappear after waiting a further 5 minutes.
> 
> A photo of the etched board is here
> 
> https://picasaweb.google.com/109391378120539635298
> 
> On close inspection of the board the unetched copper is left as stripes. So I am wondering if this is a board problem or the process.
> 
> Any help is appreciated.
> 
> Thanks
> Pete
>