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'[PICLIST] [OT] PCB fabrication - broken copper tra'
2001\04\20@180327 by John Waters

picon face
Hi All,

I made a number of PCB but the copper trace on all of them got very thin,
some are even broken. The followings were what I did:-

1. The dimension of the positive photoresist coated PCB was 3"x4".
2. I put the inkjet printed transparency on top of the PCB and exposed under
UV light for 7 minutes.
3. I put the PCB into developer solution and used a brush to help removing
the photoresist, within less than a minute, all unwanted blue colored
photoresist was gone, but I still leave the PCB soaked in the solution for
another 2 more minutes,
4. The developed PCB was then put into slightly warmed Ferric Chloride
solution, again I used a brush to remove the copper until all unwanted
copper is cleared, the whole process took about 20 minutes.

I want to know what causes the problem:-
excessive UV-exposure, developed or etched the board too long, Ferric
Chloride solution too concentrated, or what?

Thanks in advance!

John



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2001\04\20@204254 by John Waters

picon face
Hi All,

I made a number of PCB but the copper trace on all of them got very thin,
some are even broken. The followings were what I did:-

1. The dimension of the positive photoresist coated PCB was 3"x4".
2. I put the inkjet printed transparency on top of the PCB and exposed under
UV light for 7 minutes.
3. I put the PCB into developer solution and used a brush to help removing
the photoresist, within less than a minute, all unwanted blue colored
photoresist has gone, but I still leave the PCB soaked in the solution for
another 2 more minutes.
4. The developed PCB was then put into slightly warmed Ferric Chloride
solution, again I used a brush to remove the copper until all unwanted
copper is cleared, this process took about 20 minutes.

Could somebody tell me what causes the problem:-
excessive UV-exposure, developed or etched the board too long, Ferric
Chloride solution too concentrated/dilute, or what?

Thanks in advance!

John



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2001\04\21@022101 by Joan Ilari

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John Waters wrote :

{Quote hidden}

My suggestion : have a look at the following thread in PICLIST :

[OT]: laser print -> copper board PCB transfer

For me it is the definite solution for homemade PCBs. If you have any doubt
do not hesitate to contact me

Joan

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2001\04\21@071811 by Dave Selvester

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Exposure time seems a tad long to me(unless your using sunlight).
I make numerous prototype at work before committing to production.The method i use is plotting straight to transparency using a good quality laser printer at 1-1(only use high temp transparency!!).I then expose the pcb thru this for 2-3 minutes max.
The developer usually takes another 2-3 minutes,then etch normally(ferric chloride)
I have found over the years that the quality of the finnished pcb is all down to artwork quality(ie the opaqueness of the transparency)These days i tend to design 5 or 6 pcbs at a time and have them photoplotted all on a large transparent sheet by a bureau(25 pounds in uk).I can then cut this up to give me individual 'masters'
The only other advise i would give is stay away from sodium hydroxide as the developer - awfull stuff(i'm sure others would concur)

Dave

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2001\04\21@161954 by Alan B. Pearce

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>  1. The dimension of the positive photoresist coated PCB was 3"x4".
>  2. I put the inkjet printed transparency on top of the PCB and
>  exposed under
>  UV light for 7 minutes.
>  3. I put the PCB into developer solution and used a brush to
>  help removing
>  the photoresist, within less than a minute, all unwanted blue colored
>  photoresist was gone, but I still leave the PCB soaked in the
>  solution for
>  another 2 more minutes,
>  4. The developed PCB was then put into slightly warmed Ferric Chloride
>  solution, again I used a brush to remove the copper until all unwanted
>  copper is cleared, the whole process took about 20 minutes.
>
>  I want to know what causes the problem:-
>  excessive UV-exposure, developed or etched the board too long, Ferric
>  Chloride solution too concentrated, or what?

I suspect a major part of your problem is using a brush at any stage. I have
always done these sort of things by bubbling air through the liquid to
agitate it as using a brush is too likely to lift the resist, and I do not
see that it would speed up the etching any more than air bubbles. Using a
brush in the developing tank is likely to lift the resist exactly where you
want it to stay.

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2001\04\22@082341 by Wojciech Zabolotny
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On Sat, Apr 21, 2001 at 12:16:15PM +0100, Dave Selvester wrote:

> The only other advise i would give is stay away from sodium hydroxide as the developer - awfull stuff(i'm sure others would concur)
>
So what could I use instead? (NaOH is recommended by the manufacturer of
my photoresist. I dislike it too, because it is sold in big packages only,
and deteriorates quickly due to CO2 absorption :-( )
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2001\04\22@121658 by Dave Selvester

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On Sun, 22 Apr 2001 14:16:49 +0200 Wojciech Zabolotny <@spam@wzabKILLspamspamISE.PW.EDU.PL> wrote:
> On Sat, Apr 21, 2001 at 12:16:15PM +0100, Dave Selvester wrote:
>
> > The only other advise i would give is stay away from sodium hydroxide as the developer - awfull stuff(i'm sure others would concur)
> >
> So what could I use instead? (NaOH is recommended by the manufacturer of
> my photoresist. I dislike it too, because it is sold in big packages only,
> and deteriorates quickly due to CO2 absorption :-( )
> --
>           Wojtek Zabolotny
>           KILLspamwzabKILLspamspamise.pw.edu.pl
>
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>
>
Silicate based stuff is the best i have found.
It lasts for ages as a made up solution(NAOH doesnt),its not so temperature dependant and ive yet to over develop a board using it.Its incredibly fast too and is totally uncaustic which is a majot plus
In the uk i get it from http://www.megaelect.demon.co.uk
Also take a look at http://www.netcomuk.co.uk/~wwl/pcbs.html
Good pcb info here

Dave

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2001\04\22@175447 by mike

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On Sun, 22 Apr 2001 14:16:49 +0200, you wrote:

>On Sat, Apr 21, 2001 at 12:16:15PM +0100, Dave Selvester wrote:
>
>> The only other advise i would give is stay away from sodium hydroxide as the developer - awfull stuff(i'm sure others would concur)
>>
>So what could I use instead? (NaOH is recommended by the manufacturer of
>my photoresist. I dislike it too, because it is sold in big packages only,
>and deteriorates quickly due to CO2 absorption :-( )
>--
>          Wojtek Zabolotny
>          RemoveMEwzabTakeThisOuTspamise.pw.edu.pl
Totally agree - NaOH, while cheap and readily available is pretty
awful stuff.
Use a silicate based developer - solution has indefinite shelf life,
it's not nearly as temperature sensitive, and has a huge margin
between developing and overdeveloping, so you can use it really strong
to develop PCBs in 10 seconds, but not ruin them if left for a couple
of minutes.  It is available from Mega and others in the UK, and there is also a
recipie to make it on my PCB making page
http://www.netcomuk.co.uk/~wwl/pcbs.html

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2001\04\23@085119 by t F. Touchton

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part 1 2531 bytes content-type:text/plain; charset=us-asciiI think the 7 minutes was excessive.   I have used the Kepro products for quite
a few years, and have exposed the PCB with 4 flourescent UV bulbs.  My exposure
time was 20 seconds.

The brush may also be part of the problem for it is possible to scratch the
resisit.

Hope this helps,

Scott F. Touchton



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 |       Subject:     [OT] PCB fabrication - broken copper trace problem      |
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Hi All,

I made a number of PCB but the copper trace on all of them got very thin,
some are even broken. The followings were what I did:-

1. The dimension of the positive photoresist coated PCB was 3"x4".
2. I put the inkjet printed transparency on top of the PCB and exposed under
UV light for 7 minutes.
3. I put the PCB into developer solution and used a brush to help removing
the photoresist, within less than a minute, all unwanted blue colored
photoresist was gone, but I still leave the PCB soaked in the solution for
another 2 more minutes,
4. The developed PCB was then put into slightly warmed Ferric Chloride
solution, again I used a brush to remove the copper until all unwanted
copper is cleared, the whole process took about 20 minutes.

I want to know what causes the problem:-
excessive UV-exposure, developed or etched the board too long, Ferric
Chloride solution too concentrated, or what?

Thanks in advance!

John



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part 2 3156 bytes content-type:application/octet-stream; (decode)

part 3 144 bytes
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2001\04\23@193413 by Peter L. Peres

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NaOH is not that nasty in 8-10% concentration as used to develop
photoresist. I's just leach after all ?! Leach used to make soap is MUCH
stronger than 10%.

There are some solutions for photographic use that can be used to develop
photo resist. You want one whose PH can be tuned down as needed. A
photo darkroom recipe book will yield results.

Peter

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2001\04\25@010036 by Chris Cox

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I've heard NaOH called several things in these discussions. In America
it's called lye. Red Devil instructs to add it SLOWLY to COLD water, and
even after that the water warms up rapidly with stirring. Sodium
hydroxide and sodium hyperchloride are the two active ingredients in
Liquid Plumber...

"Peter L. Peres" wrote:
{Quote hidden}

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2001\04\25@185618 by Gennette, Bruce

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Some info on NaOH -

The normal layer of natural oil on your skin will protect you from contact
with low strength NaOH solutions (<10%), BUT A SECOND CONTACT WILL CAUSE
DAMAGE.  Your eyes will be damaged by exposure to the fumes as they are
protected not by skin oil but by tear water.

Repeated contact brings on sesitisation which will keep you out of any room
where NaOH is kept - even your own bathroom where ordinary soap is kept.

Use gloves and glasses while using these solutions.

Just an aside to dissolving NaOH - a common chemistry trick is to initially
dissolve it in about 10 times its volume of water.  The heat liberated
brings this small amount of water almost to boiling point which dissolves
the NaOH in just a few minutes (of rapid stirring). Cold water is then added
to bring the solution to the required strength.

Use gloves and glasses while preparing the solution.

Have I said it enough times yet - Use gloves and glasses while using these
solutions.  [That's 3 times now; ought to be enough]

Bye.

{Original Message removed}

2001\04\26@061055 by Peter L. Peres

picon face
> I've heard NaOH called several things in these discussions. In America
> it's called lye. Red Devil instructs to add it SLOWLY to COLD water, and
> even after that the water warms up rapidly with stirring. Sodium
> hydroxide and sodium hyperchloride are the two active ingredients in
> Liquid Plumber...

By leach I meant lye of course. And I was not trying to say it is baby
oil, just not cyanhidric acid or nitroglycerine, ok. Look up some figures
on the domestic consumption of NaOH (in various forms). If it would be
that bad 10% of the population should have been hurt already. Also Liquid
Plumber has a concentration of 30-40% or more.

Peter

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