PCB Etching Nightmare
Bennet Williams
developing step went great. All the exposed parts of the PCB looked
like copper and all the unexposed parts looked like photo resist. So
far, so good. After rinsing and drying, I put my board in a tank of
Radio Shack's best etching solution. Unfortunately, I don't have a
good etching tank, just a pan. After stirring for 30 minutes, barely
any of the copper was etched. After leaving it overnight, still only
1/2 of the copper is etched and some of my traces are starting to
erode - aargh! I used to etch standard PCBs all the time with Radio
Shack etchant with no problem (about 30 minutes etch time). Is there
something special about photo resist PCBs that standard etchant won't
work? Am I doing something wrong? Please help.
BRW
Tom Woodrow
Tom Woodrow
Bennet Williams
use plastic. Even the $150 model uses polyethylene (plastic).
BRW
On Wed, 13 Aug 2003 02:01:21 GMT, Tom Woodrow <tomwo...@comcast.net>
wrote:
CWatters
remove any unexposed resist using a special solution? You mentioned rinsing
but what with? Perhaps it's water but I can't remember.
"Bennet Williams" <brwil...@adelphia.net> wrote in message
news:9p2jjv087johiam71...@4ax.com...
Gary Lecomte
Did you heat the Ferric Chloride?
It Helps a lot if its at a temperature of 100 F to 120 F or even a little more.
Take care.....Gary
Boris Mohar
<brwil...@adelphia.net> wrote:
>No. It was Tupperware. I figured that was OK since most etching tanks
>use plastic. Even the $150 model uses polyethylene (plastic).
>
>BRW
Was the etchant fresh or previously used?
--
Regards,
Boris Mohar
Got Knock? - see:
Viatrack Printed Circuit Designs http://www3.sympatico.ca/borism/
Aurora, Ontario
Blake
> I have tried my first positive photo resist etch. The light exposure /
> developing step went great. All the exposed parts of the PCB looked
> like copper and all the unexposed parts looked like photo resist. So
> far, so good. After rinsing and drying, I put my board in a tank of
> Radio Shack's best etching solution. Unfortunately, I don't have a
> good etching tank, just a pan. After stirring for 30 minutes, barely
> any of the copper was etched. After leaving it overnight
Try some agitation during the etch. Orienting it either vertically or
face-down in the etchant speeds things up. Laying it flat with copper-up
will take forever.
You say you stirred for 30 minutes. Hmmm. Maybe you need new etchant. The
bottle you bought from Radio Shack may have been from 1972.
Blake
--
Drop 'pants' to reply by email
Frank Pickens
Frank P
Bennet Williams
BRW
On Wed, 13 Aug 2003 13:13:18 -0400, Boris Mohar <bor...@sympatico.ca>
wrote:
Bennet Williams
your circuit in the etching tank. You just rinse the board in water.
BRW
Bennet Williams
minutes, 5 cm away from fluorescent light. After developing, the
exposed portion was clearly copper vs. a dark blue film on the
unexposed portion.
Bennet Williams
heater and bubbler. I am also going to try a higher quality board (if
price is any indication) - M.G. Chemicals 600 series. It costs $6.50
for a 4" x 6" board vs. the $2.50 for the board I was using. I figure
if I throw enough money at this problem, it will go away. I'll
probably end up spending so much that I could get 10 boards done at
professional PCB house. The problem is, I don't have the PCB layout
software that they need.
BRW
On 13 Aug 2003 10:09:17 -0700, chem...@hotmail.com (Gary Lecomte)
wrote:
Richard Crowley
> ...I figure if I throw enough money at this problem,
> it will go away. I'll probably end up spending so much
> that I could get 10 boards done at professional PCB
> house. The problem is, I don't have the PCB layout
> software that they need.
Several have FREE layout software availble for download.
For example: http://www.pcb123.com/
AtPCLogic
>heater and bubbler. I am also going to try a higher quality board (if
>price is any indication) - M.G. Chemicals 600 series. It costs $6.50
>for a 4" x 6" board vs. the $2.50 for the board I was using. I figure
>if I throw enough money at this problem, it will go away. I'll
>probably end up spending so much that I could get 10 boards done at
>professional PCB house. The problem is, I don't have the PCB layout
>software that they need.
>
>BRW
There is an abundance of low cost software that can output files used by most
pcb houses. What house are you talking to? What software do they need?
Regards,
Brad
PC Logic
Schematic entry and PCB design software
http://www.pclogic.biz
http://members.aol.com/atpclogic/index.html
Harry Conover
After exposure, did you rinse off the un-exposed resist with the proper solvent?
Harry C.
Bennet Williams
organization. Have you used them?
BRW
Richard Crowley
> Thanks Richard. I'll look into them. It looks like a top-notch
> organization. Have you used them?
Not yet. But their customer list reads like "Who's Who" of
blue-chip technology companies. I will certainly use them
for my next project.
AtPCLogic
>organization. Have you used them?
>
>BRW
>
One word of caution. Most of the free software from a pcb house will not
produce industry standard files. You will have to go to them for additional
copies and so on. Think razor blades here. The entry price is very low, but
they get you on every board they make for you.
dan williams
my own tank with heater and bubbler, and had no problems using USED 1972
ferric chloride(well plus or minus a few years), that 4L did a LOT of
boards before it was hooped, unlike my experiances with ammonium
persulfate, when that stuff is done, it kills boards, dosn't go nearly
as far either...
dan
--
Dan Williams, Owner
Electronic Device Services
(604) 741 8431
RR8 855 Oshea rd
Gibsons BC Canada
V0N 1V8
Ross Herbert
1.Expose Riston board for approx 90 sec in light box (depends on tubes)
2.Develop pcb to remove unexposed Riston coating
3.Etch in Ammonium Persulphate or Ferric Chloride
Etching in a heated bubble tank will usually take only minutes depending
on freshness of etchant and amount of copper to be removed.
Ross Herbert
Ross Herbert
http://www.computronics.com.au/kinsten/
Geo
>This how to do it.
>
>http://www.computronics.com.au/kinsten/
>
but did you carry out the DP50 stage?
http://www.computronics.com.au/kinsten/dp/
Geo
Bennet Williams
decided that they are a little too rich for my blood. I need one-offs,
and I don't want to pay $100 for it. I'm probably being unrealistic
here, but I would like to pay about $40 - $50 for a small single-sided
board.
BRW
Allan Adler
Herbert Ross writes:
>This how to do it.
>http://www.computronics.com.au/kinsten/
It is a nice site. I'd like it better if it also included information
on environmentally responsible ways to dispose of the used chemicals
and maybe also sold stuff to facilitate doing so.
Allan Adler
a...@zurich.ai.mit.edu
****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
****************************************************************************
Ross Herbert
> Herbert Ross writes:
>
>>This how to do it.
>>http://www.computronics.com.au/kinsten/
>
> It is a nice site. I'd like it better if it also included information
> on environmentally responsible ways to dispose of the used chemicals
> and maybe also sold stuff to facilitate doing so.
>
> Allan Adler
> a...@zurich.ai.mit.edu
>
Hi Allan,
Yes, I have to agree with you that sellers of potentaially hazardous
chemicals should also act responsibly by giving information about
disposal of waste products.
I did some digging and found the MSDS for the 2 most common etchants;
Ferric Chloride http://www.deltrex.com.au/products/s080.htm
Ammonium Persulphate
http://www.progen.com.au/zone_files/Life_Sciences_MSDS/ammonium_persulphate_ud007-02.pdf
Recycling of Ferric Chloride etchant can be done but is really only
economical in large quantities as indicated by this item
http://emeso.lanl.gov/Stories/FeCl.htm
This paper http://www.rsc.org/pdf/jem/1999/A9808158.PDF indicates
several techniques for re-utilisinf Ferric Chloride but again, none of
these methods would be available to the hobby or small pcb manufacturer.
This University of Wisconsin page recommends that up to 5lbs of Ammonium
Persulphate is safe to dispose of via the sewer
http://www.uwm.edu/Dept/EHSRM/HAZMAT/SOPoxidizer.html
I suppose that all of this really highlights the fact that in most cases
hobby pcb manufacturers are almost forced to dispose of our waste
etchant down the sewer. I dare say that eventually it will come back to
bite us on the bum.
Ross Herbert
Bill Jenkins
long enough to get thru the resist. Try repositioning your layout and
re-exposing again. What type of artwork did you use?
I looked at the replies and your answers, and I think you said the
board was 5" away from your light source.
Did you use a piece of glass to hold the layout against the board?
If you did, and you used just any old piece, it may have had lead in
it. This will impede the uv which exposes the resist. Get a piece of
6mm no lead content plate glass from your local glass house and try
again.
I use F15T8BL uv lamps or the latest eqv in cheap fluroscent holders
I buy from Home Depot. I remove the plastic cover, replace their lamp.
I built a box big enough to hold 4 holders, with 6" high sides and
rabbitted a groove on the top inside edge, for the glass to sit in.
With the holders 3" apart, I can expose a 12" x 12" board without
problems. Since my lamps are 15 years old, I expose 5 minutes and can
easily do .01" traces. I have used MG boards and resist for years,
but now they don't supply resist. I coat my own boards with positive
resist and use MG418 developer mixed .1part dev, to 6 parts water.
This is my "stock" solution. When I need developer, I mix 1 part stock
to 1 part water. It can be cold and put it in a glass dish. I watch
the resist change color, and remove the board when it is quite dark. I
wash it off and put it back into the tray to finish developing, then
wash and etch.
The developer can be reused until it get too dark to see the board.
Keep the used developer in a different bottle.
If you need any assistance please contact me and I will try to help.
Bill Jenkins
Charles Jean
wrote:
___
I tried looking for some positive photoresist at MG, but couldn't find
any. Where can you get it? Any special tips or tricks about applying
it to the boards?
Bill Jenkins
years or so. At least not in Canada where I am. I bought 5 gallons
from the company who made the original resist that MG sold. Now due to
WHMIS and all those regulations, it's difficult to send it in liquid.
The fines are disgusting.
I had thought that a way to do it would be to coat boards and sell
them. There would be a learning curve to be able to coat them in
quantity for resale. I usually coat a 36" x 12" piece and cut when and
as needed. This works for me.
I coat the boards by first wiping the copper with a paper towel soaked
in some acetone. This removes the surface grease and allows the resist
to coat quite nicely. I pour some resist into a glass or metal tray,
hold the board vertical and use a fine foam brush to "paint" a layer
of resist over it. Excess resist will run down into the tray, for use
again, then when most of the excess is off, I take the board into my
darkroom and place it upright and onto a pad of paper towel to sop up
the resist drips. Then pour the tray resist back into the bottle.
The new resist I have is quite forgiving, it doesn't matter if there
are run lines, making some areas thicker than others, (within reason).
I just expose a little longer and these runs develop out and I get a
etchable board.
Resist is green and exposed resist turns red in the developer making
it easy to see areas needing to be developed longer. As I said
previously, I take the board out of the developer just after it turns
red and wash the developed resist off, then back in for more develop
time.
Hope this helps
Bill
Allan Adler
Bill Jenkins wrote:
>Positive photo resist has not been available to us users for three
>years or so. At least not in Canada where I am. I bought 5 gallons
>from the company who made the original resist that MG sold. Now due to
>WHMIS and all those regulations, it's difficult to send it in liquid.
What about in a spray can?
Ignorantly,
Bill Jenkins
brush to smooth it out and give a level coating.
MG dropped these years ago. Never found any others here. Have seen
them mentioned in newsgroups.
Bill
On 19 Aug 2003 01:39:56 -0400, Allan Adler <a...@nestle.ai.mit.edu>
wrote:
Allan Adler
Bill Jenkins wrote of spray cans of positive resist:
>Loved these when they were available. Sprayed a little, used the foam
>brush to smooth it out and give a level coating.
>MG dropped these years ago. Never found any others here. Have seen
>them mentioned in newsgroups.
Others will probably mention them, if they are still available.
But I'm just wondering how hard it is to make one's own spray cans
for this purpose. People do home canning and people use CO2 cartridges
to make their own seltzer and several decades ago, in lieu of canned bug
sprays, people had DIY bug spray using some clumsy mechanical contraption
that came with the liquid insecticide. So maybe it is possible to improvise.
I'm no good at practical stuff like this, although I succeed occasionally,
but what would be wrong with an arrangement using a CO2 cartridge and
positive resist in a seltzer bottle and a suitable kind of nozzle to shape
the spray better, just as some kinds of shower heads do?
JeffM
will quickly tell you whether it is depleted etchant.
I'm lucky that there was a stirring hotplate
in my lab when I got there.
A pyrex baking dish, a teflon-coated magnet
(stirred by the magnet clutch of the hotplate),
and some ceramic blocks to elevate the PCB
make life easy.
CadSoft USA (divison of a German company)
http://www.cadsoftusa.com/
has a nice PCB layout package called EAGLE
(Easily Applicable Graphical Layout Editor).
The free version does 100mm x 80mm double-sided (4" x ~3").
It will output Gerber;
many PCB houses also take native EAGLE files.
Like anything else, it has its quirks but it is very popular.
The upgrade path is also reasonable.
There is a user's newsgroup and a factory-guys newsgroup
(caution: Tilmann doesn't suffer fools lightly).
>boards like a nice warm sauna
>dan williams
>>I've decided to...buy a $40 etch tank with a heater and bubbler.
>>...professional PCB house...
>>...I don't have the PCB layout software that they need.
>>Bennet Williams
>>>..After stirring for 30 minutes...
>>>..After leaving it overnight
>>>...some of my traces are starting to erode
>>>Bennet Williams
Terry J. Ilardi
local hardware store, or at least a local home center such as Home Depot
carries Preval units. These come with compressed cartridges and a small
glass sjar and are made specifically for for the purpose of making your
own spray "cans". They are cheap (under 10 USD) and widely
available-at least in the US.
Terry Ilardi