Homebrew PCBs

Hi.

I have been printing artwork for making PCB's using negative photo resist. The first problem I ran into was the lack of opacity of the toner. It looks nice and dark until I hold it up to a light, then it's easy to see how translucent it really is.

I tried using the whiteboard marker method mentioned on this list before, but had problems getting it to work consistently. Usually I can't removed the marker from the clear part of the foil without also removing some of the toner.

I have tried dipping the foil in acetone or xylene. The toner looks much better, but is only marginally more opaque.

Heating the foil gives basically the same result as the solvents, but somewhat more opaque.

I tried spraying the foil with clear paint. Doesn't help at all, but it looks very nice. Might be useful for other purposes like panels.

The method I found to work best us to bond an opaque powder to the toner.

I used a very fine cerium oxide powder, normally used for polishing telescope mirrors. I will try aluminium oxide when I remember where I put it. I also tried powdered graphite, but it did not work nearly as well as the cerium oxide.

I put a clothes iron upside down and the put the foil on top of it, with the non-printed side touching the iron. I then brush CeO2 powder on it until no more powder will stick. After it has cooled for a few seconds I wash it with water and detergent. The result looks gray but is very opaque. It took some experimenting to find the correct temperature setting so that the toner would bond to the powder while not shrinking, but there seems to be a wide range that works.

I also tried mixing the CeO2 with xylene and dip the foil in it before leaving it to dry. After it was dry I washed off the excess powder. This works, but the result was less consistent and not as opaque as the melting method.


Emil

Interesting! Thanks for posting.

How about dipping the film in a liquid that will make the toner sticky and
the toner dries slowly.  Then sprinkle lots of powder over it and hopefully
the [powder will stick in the still sticky toner.  After drying, shake off
the extra powder.

Bertho

From: Emil Johnsen   Sent: Thursday, August 30, 2012 10:11



Hi.
I have been printing artwork for making PCB's using negative photo resist.
The first problem I ran into was the lack of opacity of the toner. It looks
nice and dark until I hold it up to a light, then it's easy to see how
translucent it really is.

I tried using the whiteboard marker method mentioned on this list before,
but had problems getting it to work consistently. Usually I can't removed
the marker from the clear part of the foil without also removing some of the
toner.

I have tried dipping the foil in acetone or xylene. The toner looks much
better, but is only marginally more opaque.

Heating the foil gives basically the same result as the solvents, but
somewhat more opaque.

I tried spraying the foil with clear paint. Doesn't help at all, but it
looks very nice. Might be useful for other purposes like panels.

The method I found to work best us to bond an opaque powder to the toner.

I used a very fine cerium oxide powder, normally used for polishing
telescope mirrors. I will try aluminium oxide when I remember where I put
it. I also tried powdered graphite, but it did not work nearly as well as
the cerium oxide.

I put a clothes iron upside down and the put the foil on top of it, with the
non-printed side touching the iron. I then brush CeO2 powder on it until no
more powder will stick. After it has cooled for a few seconds I wash it with
water and detergent. The result looks gray but is very opaque. It took some
experimenting to find the correct temperature setting so that the toner
would bond to the powder while not shrinking, but there seems to be a wide
range that works.

I also tried mixing the CeO2 with xylene and dip the foil in it before
leaving it to dry. After it was dry I washed off the excess powder. This
works, but the result was less consistent and not as opaque as the melting
method.
Emil



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

Hi Emil,

I found I did not need to improve the contrast ratio of the phototools I
made with a laser printer.  I am using Riston MM540 from the Czech
Republic, via eBay:

  http://www.tech-place.com/pyralux/23-photosensitive-film.html
  http://myworld.ebay.com/gaminn/

I used a ~1mm photodiode with light from an incandescent lamp to test
how much light passed through the black areas of the phototools I
created by laser printing on this "A4 transparency film":

  http://screenprinting.asc365.com/index.asp?ID=PD007003

I am using a Brother HL-5250DN, running at 1200 x 1200 DPI.

The black areas passed about 1/7th the light of the clear areas.  There
is some variation in the darkness of the black areas, due to
irregularities in the drum, the toner cart and how the toner arranges
itself on the film.  600 x 600 mode looks the same and is just as good
for most PCB designs.  I get a more even pattern of darkness with the
HL-4040CN colour printer operating in monochrome mode.

The lighter parts of the image are the limiting factor for exposing
photoresist.  Without a smaller photodiode, I can't tell exactly what
the light level is there.  (I could scan it with a transparency scanner
to find out for sure.)  I guess I have a 5:1 contrast ratio between the
clear parts of the image and the lightest parts of the black part.

I find this is plenty of contrast for the Riston.  I am using a 500W
240v quartz halogen lamp to expose the Riston.  Most of the exposure
occurs in the violet and near ultraviolet ranges.  As far as I know, the
toner is just as opaque there as it is for visible light.

  - Robin   http://www.firstpr.com.au/pcb-diy/

One problem with the Laser discharge - electrostatic toner process is
that the characteristics of the phototconducter do not assure a uniform
density over large solid areas. I don't know the details so I will not
speculate as to any remedies. Simply copying the image to an inkjet at a
higher contrast level might serve your needs if you are not doing toner
transfer.  Also,  it would seem to me that a 2x copy from a laser
printer reduced to correct size on an inkjet might eliminate the voids.

Of course that brings its own problems like wet ink wrinkles and
tracking in the inkjet.  After a while it may turn out that accepting
the quality you have is not so bad!

My experience is from many years of field service with IBM equipment. I
learned long ago that I should pay attention to what a new operator had
to say about today's problems.  Frequently the newbie's fresh view led
the way to a better process!

Don't give up fixing the problem!



--- In Homebrew_PCBs@yahoogroups.com, Emil Johnsen <emil123@...> wrote:
>
> Hi.
>
> I have been printing artwork for making PCB's using negative photo
resist. The first problem I ran into was the lack of opacity of the
toner. It looks nice and dark until I hold it up to a light, then it's
easy to see how translucent it really is.
>
> I tried using the whiteboard marker method mentioned on this list
before, but had problems getting it to work consistently. Usually I
can't removed the marker from the clear part of the foil without also
removing some of the toner.
>
> I have tried dipping the foil in acetone or xylene. The toner looks
much better, but is only marginally more opaque.
>
> Heating the foil gives basically the same result as the solvents, but
somewhat more opaque.
>
> I tried spraying the foil with clear paint. Doesn't help at all, but
it looks very nice. Might be useful for other purposes like panels.
>
> The method I found to work best us to bond an opaque powder to the
toner.
>
> I used a very fine cerium oxide powder, normally used for polishing
telescope mirrors. I will try aluminium oxide when I remember where I
put it. I also tried powdered graphite, but it did not work nearly as
well as the cerium oxide.
>
> I put a clothes iron upside down and the put the foil on top of it,
with the non-printed side touching the iron. I then brush CeO2 powder on
it until no more powder will stick. After it has cooled for a few
seconds I wash it with water and detergent. The result looks gray but is
very opaque. It took some experimenting to find the correct temperature
setting so that the toner would bond to the powder while not shrinking,
but there seems to be a wide range that works.
>
> I also tried mixing the CeO2 with xylene and dip the foil in it before
leaving it to dry. After it was dry I washed off the excess powder. This
works, but the result was less consistent and not as opaque as the
melting method.

>
>
> Emil
>

You might try misting your image with CitraSolv concentrate. It is an excellent environmentally friendly toner solvent and works as well as acetone to remove toner after etching. It seems to melt the toner. I wipe a thin coat on the copperclad and let it dry before passing my board through the laminator to aid in the fusing process. In your case, the thought is that it might melt the toner to increase the Opacity. I have seen a product that comes in a spray can that claims to do the same thing, but I can't remember it name.

Baxter

--- In Homebrew_PCBs@yahoogroups.com, Emil Johnsen <emil123@...> wrote:

>
> Hi.
> 
> I have been printing artwork for making PCB's using negative photo resist. The first problem I ran into was the lack of opacity of the toner. It looks nice and dark until I hold it up to a light, then it's easy to see how translucent it really is.
> 
> I tried using the whiteboard marker method mentioned on this list before, but had problems getting it to work consistently. Usually I can't removed the marker from the clear part of the foil without also removing some of the toner.
> 
> I have tried dipping the foil in acetone or xylene. The toner looks much better, but is only marginally more opaque.
> 
> Heating the foil gives basically the same result as the solvents, but somewhat more opaque.
> 
> I tried spraying the foil with clear paint. Doesn't help at all, but it looks very nice. Might be useful for other purposes like panels.
> 
> The method I found to work best us to bond an opaque powder to the toner.
> 
> I used a very fine cerium oxide powder, normally used for polishing telescope mirrors. I will try aluminium oxide when I remember where I put it. I also tried powdered graphite, but it did not work nearly as well as the cerium oxide.
> 
> I put a clothes iron upside down and the put the foil on top of it, with the non-printed side touching the iron. I then brush CeO2 powder on it until no more powder will stick. After it has cooled for a few seconds I wash it with water and detergent. The result looks gray but is very opaque. It took some experimenting to find the correct temperature setting so that the toner would bond to the powder while not shrinking, but there seems to be a wide range that works.
> 
> I also tried mixing the CeO2 with xylene and dip the foil in it before leaving it to dry. After it was dry I washed off the excess powder. This works, but the result was less consistent and not as opaque as the melting method.
> 
> 
> Emil
>

Thank you for your reply John.

I consider the problem to be (mostly) solved :)

The heat + powder method I described works very well. It adds 5 minutes to the process but the results are good.


Emil

On 31-08-12, John  <jferrell13@...> wrote: 
> One problem with the Laser discharge - electrostatic toner process is
> 
> that the characteristics of the phototconducter do not assure a uniform
> 
> density over large solid areas. I don't know the details so I will not
> 
> speculate as to any remedies. Simply copying the image to an inkjet at a
> 
> higher contrast level might serve your needs if you are not doing toner
> 
> transfer.  Also,  it would seem to me that a 2x copy from a laser
> 
> printer reduced to correct size on an inkjet might eliminate the voids.
> 
> 
> 
> Of course that brings its own problems like wet ink wrinkles and
> 
> tracking in the inkjet.  After a while it may turn out that accepting
> 
> the quality you have is not so bad!
> 
> 
> 
> My experience is from many years of field service with IBM equipment. I
> 
> learned long ago that I should pay attention to what a new operator had
> 
> to say about today's problems.  Frequently the newbie's fresh view led
> 
> the way to a better process!
> 
> 
> 
> Don't give up fixing the problem!

I've heard of people using solvent fumes to inrease the opacity.

I never had any problems with it when I used a laser printer, FWIW.

I've now been using inkjet printers for many years, and never have any 
problems with my transparencies using those, either.

Leon
-- 
Leon Heller
G1HSM

There is a relatively easy solution. From the PCBfabinabox product there is something called TRF, or toner reactive film.  You apply your toner to your board, then place a piece of this toner film over and run it through a laminator.  Peel the TRF film away and it will leave behind a very opaque substance on the PCB that only sticks to the toner.

Perhaps this might help.

http://www.pcbfx.com/main_site/pages/products/toner_foils.html

Neill





________________________________

 From: Robin Whittle <rw@firstpr.com.au>
To: Homebrew_PCBs@yahoogroups.com 
Sent: Thursday, August 30, 2012 7:23 PM
Subject: Re: [Homebrew_PCBs] Increasing the opacity of laser printed film
 

  
Hi Emil,

I found I did not need to improve the contrast ratio of the phototools I
made with a laser printer.  I am using Riston MM540 from the Czech
Republic, via eBay:

http://www.tech-place.com/pyralux/23-photosensitive-film.html
http://myworld.ebay.com/gaminn/

I used a ~1mm photodiode with light from an incandescent lamp to test
how much light passed through the black areas of the phototools I
created by laser printing on this "A4 transparency film":

http://screenprinting.asc365.com/index.asp?ID=PD007003

I am using a Brother HL-5250DN, running at 1200 x 1200 DPI.

The black areas passed about 1/7th the light of the clear areas.  There
is some variation in the darkness of the black areas, due to
irregularities in the drum, the toner cart and how the toner arranges
itself on the film.  600 x 600 mode looks the same and is just as good
for most PCB designs.  I get a more even pattern of darkness with the
HL-4040CN colour printer operating in monochrome mode.

The lighter parts of the image are the limiting factor for exposing
photoresist.  Without a smaller photodiode, I can't tell exactly what
the light level is there.  (I could scan it with a transparency scanner
to find out for sure.)  I guess I have a 5:1 contrast ratio between the
clear parts of the image and the lightest parts of the black part.

I find this is plenty of contrast for the Riston.  I am using a 500W
240v quartz halogen lamp to expose the Riston.  Most of the exposure
occurs in the violet and near ultraviolet ranges.  As far as I know, the
toner is just as opaque there as it is for visible light.

- Robin http://www.firstpr.com.au/pcb-diy/


 

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

There are foils used with laser printers to create gold and other metallic looking logos for fancy stationary.  I used to buy it decades ago.  If I remember correctly, it was/is called Omni-Chrome or something like it.  

I also used it for making dense artwork as described below.  I think that company is just using that same material and re-labeling it as special product for PCBs.

Bertho

From: Confidential   Sent: Saturday, September 01, 2012 05:58



There is a relatively easy solution. From the PCBfabinabox product there is something called TRF, or toner reactive film.  You apply your toner to your board, then place a piece of this toner film over and run it through a laminator.  Peel the TRF film away and it will leave behind a very opaque substance on the PCB that only sticks to the toner.
Perhaps this might help.
http://www.pcbfx.com/main_site/pages/products/toner_foils.html
Neill



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

On Sat, Sep 1, 2012 at 2:58 AM, bebx2000 <bebx2000@...> wrote:

> **
>
>
>
>
> You might try misting your image with CitraSolv concentrate. It is an
> excellent environmentally friendly toner solvent and works as well as
> acetone to remove toner after etching. It seems to melt the toner. I wipe a
> thin coat on the copperclad and let it dry before passing my board through
> the laminator to aid in the fusing process. In your case, the thought is
> that it might melt the toner to increase the Opacity. I have seen a product
> that comes in a spray can that claims to do the same thing, but I can't
> remember it name.
>
> Baxter
>
>

Laser Buddy?


http://www.laserbuddy.com/faq.htm

Think it's just solvent in a can.  I bought some for use with toner
transfer. Had very mixed results.

 -carl


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

Looks like there are many products like this.. not found any here.

My thinking was the same, just a solvent in a spray can, that's why I tried acetone and xylene.


Emil

> Laser Buddy?
> 
> http://www.laserbuddy.com/faq.htm
> 
> Think it's just solvent in a can.  I bought some for use with toner
> 
> transfer. Had very mixed results.
> 
> -carl

A question for you chemical experts out there: If this question is not off topic: if it is let me know and I will stop.
I have a large amount of copper clad boards with no positive or negative devolopement solution on them.  Is there
a chem. that I can brush or spray onto these boards to turn them into boards ready for positive or negative developement type boards?


________________________________

 From: H. Carl Ott <hcarlott@...>
To: Homebrew_PCBs@yahoogroups.com 
Sent: Saturday, September 1, 2012 7:56 AM
Subject: Re: [Homebrew_PCBs] Re: Increasing the opacity of laser printed film
 

  
On Sat, Sep 1, 2012 at 2:58 AM, bebx2000 <bebx2000@...> wrote:

> **
>
>
>
>
> You might try misting your image with CitraSolv concentrate. It is an
> excellent environmentally friendly toner solvent and works as well as
> acetone to remove toner after etching. It seems to melt the toner. I wipe a
> thin coat on the copperclad and let it dry before passing my board through
> the laminator to aid in the fusing process. In your case, the thought is
> that it might melt the toner to increase the Opacity. I have seen a product
> that comes in a spray can that claims to do the same thing, but I can't
> remember it name.
>
> Baxter
>
>

Laser Buddy?

http://www.laserbuddy.com/faq.htm

Think it's just solvent in a can.  I bought some for use with toner
transfer. Had very mixed results.

-carl

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


 

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

On 09/02/2012 12:08 AM, Kevin Byrne wrote:
> A question for you chemical experts out there: If this question is not off topic: if it is let me know and I will stop.
> I have a large amount of copper clad boards with no positive or negative devolopement solution on them.  Is there
> a chem. that I can brush or spray onto these boards to turn them into boards ready for positive or negative developement type boards?
> 


Kontaktchemie: Positiv 20 (spray)
Cinkarna Celje: P-501 (1 l bottle for various ways of application)

-- 
Best Regards,
Q Systems
Zoran A. \u0160\u0107epanovi\u0107
http://zastos.com
+381 63 609-993

-..-
S**t happens. When you solve s**t, it mutates.
S**t never goes away. Entropy IS s**t.
Depend on it.

I think the best option is a negative film.

You stick it to the board and then use a laminator or clothes iron to bond the film to the board.

I'm using this one:
http://www.octamex.de/shop/?page=shop/flypage&product_id=29&category_id=5848924494118370762daa6f026e22f7&/Tenting__Laminat_fuer_Bestueckungsdruck__1m_kaufen.html

The are a different kinds on ebay. Search for "photo resist".

I'm not aware of any wet chemistry to make negative boards, but there are various positive photo resist products that are sprayed on or the board or you dip the board in it. I have not tried this, but I have heard it's hard to get consistent results with the spray products.


Emil 

On 02-09-12, Kevin Byrne  <kbyrne10@...> wrote:     
> A question for you chemical experts out there: If this question is not off topic: if it is let me know and I will stop.
> 
> I have a large amount of copper clad boards with no positive or negative devolopement solution on them.  Is there
> 
> a chem. that I can brush or spray onto these boards to turn them into boards ready for positive or negative developement type boards?

You can also get films that you can laminate onto the board. That is what I have been using. Never tried spray-on though as I can't get any easily.

--- In Homebrew_PCBs@yahoogroups.com, "Zoran A. Scepanovic" <zastos@...> wrote:

>
> On 09/02/2012 12:08 AM, Kevin Byrne wrote:
> > A question for you chemical experts out there: If this question is not off topic: if it is let me know and I will stop.
> > I have a large amount of copper clad boards with no positive or negative devolopement solution on them.  Is there
> > a chem. that I can brush or spray onto these boards to turn them into boards ready for positive or negative developement type boards?
> > 
> 
> 
> Kontaktchemie: Positiv 20 (spray)
> Cinkarna Celje: P-501 (1 l bottle for various ways of application)
> 
> -- 
> Best Regards,
> Q Systems
> Zoran A. Šćepanović
> http://zastos.com
> +381 63 609-993
> 
> -..-
> S**t happens. When you solve s**t, it mutates.
> S**t never goes away. Entropy IS s**t.
> Depend on it.
>

Can you provide a source to buy and research that product as I am new to this?


________________________________

 From: Zoran A. Scepanovic <zastos@gmail.com>
To: Homebrew_PCBs@yahoogroups.com 
Sent: Saturday, September 1, 2012 5:14 PM
Subject: Re: [Homebrew_PCBs] Re: Increasing the opacity of laser printed film
 

  
On 09/02/2012 12:08 AM, Kevin Byrne wrote:
> A question for you chemical experts out there: If this question is not off topic: if it is let me know and I will stop.
> I have a large amount of copper clad boards with no positive or negative devolopement solution on them.  Is there
> a chem. that I can brush or spray onto these boards to turn them into boards ready for positive or negative developement type boards?
> 

Kontaktchemie: Positiv 20 (spray)
Cinkarna Celje: P-501 (1 l bottle for various ways of application)

-- 
Best Regards,
Q Systems
Zoran A. Šćepanović
http://zastos.com
+381 63 609-993

-..-
S**t happens. When you solve s**t, it mutates.
S**t never goes away. Entropy IS s**t.
Depend on it.

 

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

On Sat, Sep 1, 2012 at 9:41 AM, Boman33 <boman33@...> wrote:

> There are foils used with laser printers to create gold and other metallic
> looking logos for fancy stationary. I used to buy it decades ago. If I
> remember correctly, it was/is called Omni-Chrome or something like it.


I remember those. But the ones I bought (and still have) are or were sold
under the name "Ibifoil".

I´ve never thought of those films for use in making PCBs, however... (I´m
new on this list and only thinking about some day making my own PCBs...
just gathering information on the best and cheapest way to do it...).

FC
-- 
During times of Universal Deceit, telling the truth becomes a revolutionary
act
- George Orwell


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

Thank you for the help. I have the web-site bookmarked and will be investigateing negative developement. I only 
know positive developement thou. Does any one know of a tutorial in negative developement that they would 
recommend going along with this topic I have been following? Thanks Kevin


________________________________

 From: Kevin Byrne <kbyrne10@yahoo.com>
To: "Homebrew_PCBs@yahoogroups.com" <Homebrew_PCBs@yahoogroups.com> 
Sent: Saturday, September 1, 2012 9:03 PM
Subject: Re: [Homebrew_PCBs] Re: Increasing the opacity of laser printed film
 

  
Can you provide a source to buy and research that product as I am new to this?

________________________________
From: Zoran A. Scepanovic <zastos@...>
To: Homebrew_PCBs@yahoogroups.com 
Sent: Saturday, September 1, 2012 5:14 PM
Subject: Re: [Homebrew_PCBs] Re: Increasing the opacity of laser printed film


  
On 09/02/2012 12:08 AM, Kevin Byrne wrote:
> A question for you chemical experts out there: If this question is not off topic: if it is let me know and I will stop.
> I have a large amount of copper clad boards with no positive or negative devolopement solution on them.  Is there
> a chem. that I can brush or spray onto these boards to turn them into boards ready for positive or negative developement type boards?
> 

Kontaktchemie: Positiv 20 (spray)
Cinkarna Celje: P-501 (1 l bottle for various ways of application)

-- 
Best Regards,
Q Systems
Zoran A. Šćepanović
http://zastos.com
+381 63 609-993

-..-
S**t happens. When you solve s**t, it mutates.
S**t never goes away. Entropy IS s**t.
Depend on it.

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


 

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

I just made a little batch of boards using a fresh batch of Riston MM540
from the Czech Republic, via eBay:

  http://www.tech-place.com/pyralux/23-photosensitive-film.html
  http://myworld.ebay.com/gaminn/

As I described earlier, I am using a Brother HL-5250DN on laser film
from Canada:

  http://screenprinting.asc365.com/index.asp?ID=PD007003

where the black blocks all but about 1/7th of the light.

This is with a 500W 240V incandescent floodlight with about 40cm from
the filament to the PCB.  The protective glass from the floodlight was
removed, and I used it to hold the phototool to the PCB, which was on
some firm foam.  I used extra weight to hold the glass down more firmly.
 Glass is not as good for pressing the phototool to the PCB as a
flexible plastic vacuum frame would be.

I did two exposure times for this phototool which contained 12 little
PCB images.  The boards which got 2 minutes 20 seconds mainly worked,
but there were a few defects.  Those which got 4 minutes worked very
well.  The boards were single-sided, with SMD components including an
SOIC-16, with 0.010" tracks.

This is quite a range of exposure times.  In the past I had a test
exposure where boards worked out not too bad with exposure times which
were a factor of two different.

I think this Riston is quite a high contrast material, so the ~7:1 ratio
of light and dark I get, which is probably 5:1 or so for the weakest
parts of the "black" image, is perfectly adequate without any need to
make the black parts darker.

I think the key to this is to use a clear film which the laser toner
bonds to evenly - as is the case with the material I am using.  A
diffuse film would reflect some light back and would scatter the light
it passes.

I am using a Lowell laminator modified for cooler operation at around
125C instead of 150C, as I wrote to the list on 19th May.  I cut away
the top housing so I can see the aluminium channels which contain the
rollers.  I also got rid of a pesky metal thing on the output slot.
(This is arguably unsafe, since the metal is not grounded and there are
potentially exposed mains wires - so don't take this as a recommendation
for a safe way of working.)

I find the trick for laminating large areas of Riston without wrinkles
or bubbles is:

1 - Clean the copper with Jif (abrasive white liquid for cleaning sinks
etc.) of similar, to give it a clean and perhaps
slightly rough surface.

2 - Press one edge of the Riston onto the leading edge of the copper
clad board.  All the rest of the Riston should be laying flat, on the
copper *except* that there is a sheet of paper between the Riston and
the copper.

3 - As I feed the board into the laminator, I hang onto the paper so its
edge is always a few mm away from the rollers.  I may lift the Riston up
a little and provide a little tension on it.  The goal is to stop the
Riston sticking to the copper until it is very close to, or exactly at,
the rollers.

As per the Riston documentation I develop with 0.85% sodium carbonate
solution, warmed up somewhat to I guess 30 or 35C.  There is a rinse
step as well, but I haven't yet got suitable mildly hard water.  Maybe
Melbourne tap water is OK.

The MM500 series datasheet is the general processing guide is at:

  http://www2.dupont.com/Imaging_Materials/en_US/tech_info/datasheets
/index.html

I am etching with ferric chloride and citric acid, as I will describe in
another message.  I strip the Riston off the etched board with 3% sodium
hydroxide.  These circuits were with 0.5 oz copper on thin FR4:

 http://www.pcbfx.com/main_site/pages/products/rigid_pc_boards.html

  - Robin   http://www.firstpr.com.au/pcb-diy/

I found on E-Bay positiv 20 and another brand with the 21 # on the bottle but can only find them overseas, Europe
no american suppliers so far. Thanks for help and leads as I am following this post. best Kevin


________________________________

 From: Emil Johnsen <emil123@...>
To: Homebrew_PCBs@yahoogroups.com 
Sent: Saturday, September 1, 2012 5:31 PM
Subject: Re: [Homebrew_PCBs] Re: Increasing the opacity of laser printed film
 

  
I think the best option is a negative film.

You stick it to the board and then use a laminator or clothes iron to bond the film to the board.

I'm using this one:
http://www.octamex.de/shop/?page=shop/flypage&product_id=29&category_id=5848924494118370762daa6f026e22f7&/Tenting__Laminat_fuer_Bestueckungsdruck__1m_kaufen.html

The are a different kinds on ebay. Search for "photo resist".

I'm not aware of any wet chemistry to make negative boards, but there are various positive photo resist products that are sprayed on or the board or you dip the board in it. I have not tried this, but I have heard it's hard to get consistent results with the spray products.

Emil 

On 02-09-12, Kevin Byrne  <kbyrne10@...> wrote: 
> A question for you chemical experts out there: If this question is not off topic: if it is let me know and I will stop.
> 
> I have a large amount of copper clad boards with no positive or negative devolopement solution on them.  Is there
> 
> a chem. that I can brush or spray onto these boards to turn them into boards ready for positive or negative developement type boards?


 

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