Homebrew PCBs

I am a newbie to this list and am keen to set up for using Riston
(negative) photoresist for making small quantities of relatively small
PCBs.  I used it in mid-1980s but then I had a process camera and could
make really good phototools.

The developer and stripper chemicals are cheap and easy - sodium
carbonate (washing soda) and caustic soda respectively.

My initial tests with a novel exposure technique are encouraging - I
will describe this in another message.

It is possible to buy Riston coated single-sided 1.6mm FR4 PCB material
in Australia:  (Asterisks added to force indents in the Yahoo Groups
archives, which gobble leading spaces.)

*  http://www.jaycar.com.au/productView.asp?ID=HG9970

but it is expensive: $24.95 for 152 x 152mm (6 inches square).  This is
what I used for tests.  According to the instructions in the pack, this
material comes from http://www.rcsradio.com.au, a business established
in 1943 but which has ceased trading since the proprietor Bob Barnes died:

*  http://www.thebackshed.com/forum/forum_posts.asp?TID=3574

so it would not be surprising if Jaycar discontinued this.

Kalex in Melbourne: http://www.kalex.net.au advertise 1.6mm single-sided
Riston-coated PCB material in their pricelist.  I called them and was
told that this is only for large quantity - they don't keep any in stock.

I couldn't find any other sources of FR4 already coated with Riston, so
this lead me to buying the Riston film itself, and looking at techniques
for laminating it to the PCB material.  This will allow me to choose
1.6mm and 0.8mm material with normal (1 ounce) copper or thinner (0.5
oz) copper.  I understand the finer tracks can be achieved with the
thinner copper because the etch time is reduced, leaving less time to
undercut the photoresist, and I guess with the copper being thinner and
less accessible to the etchant.  If I get adventurous I may even try
double-sided PCBs.

This is for prototyping - and for the satisfaction of making things at home.

The Riston information is at:

*
http://www2.dupont.com/Imaging_Materials/en_US/tech_info/product_selector.html

I found 3 sources of Riston film.  I also found some Chinese sources of
generally un-named dry negative photoresist film.  The last one mentions
it is Hitachi photoresist:

*  http://stores.ebay.com/Led-Light-Bulb-World/_i.html?_nkw=photoresist
*  http://stores.ebay.com/Digole-Digital-Solution/_i.html?_nkw=photoresist
*  http://stores.ebay.com/oneworldonedream2010/_i.html?_nkw=photoresist
*  www.ebay.com/sch/dr_ho_000/m.html


The first Riston source is Think and Tinker in the USA.  They sell rolls
of "M115", which I assume means Riston MM115 or MM115i.  This is 50
microns thick.  However, I don't need such large quantities.

  http://www.thinktink.com/products/Photopolymers.asp

The second source is in Sweden.  They sell sheets of Riston FX515 which
is 15 microns thick.

* http://www.ebay.com/sch/karass/m.html

The third source is in the Czech Republic.  They sell A5 sheets of
Riston MM540.  This is 38 micron.  I ordered some sheets today.

*  http://www.ebay.com/sch/gaminn/m.html

Can anyone comment on the merits of Riston or alternative brands of
negative photoresist, or on the three thicknesses: 15um, 38um and 50um?

  - Robin   Melbourne Australia    http://www.firstpr.com.au/rwi/dfish/

Thanks for a detailed post with good information.

A quick question:  Why not also consider positive resist?

=============================

From:  Robin Whittle  Sent: Thursday, May 17, 2012 11:12
I am a newbie to this list and am keen to set up for using Riston
(negative) photoresist for making small quantities of relatively small
PCBs. I used it in mid-1980s but then I had a process camera and could
make really good phototools.

The developer and stripper chemicals are cheap and easy - sodium
carbonate (washing soda) and caustic soda respectively.

My initial tests with a novel exposure technique are encouraging - I
will describe this in another message.

It is possible to buy Riston coated single-sided 1.6mm FR4 PCB material
in Australia: (Asterisks added to force indents in the Yahoo Groups
archives, which gobble leading spaces.)

* http://www.jaycar.com.au/productView.asp?ID=HG9970

but it is expensive: $24.95 for 152 x 152mm (6 inches square). This is
what I used for tests. According to the instructions in the pack, this
material comes from http://www.rcsradio.com.au, a business established
in 1943 but which has ceased trading since the proprietor Bob Barnes died:

* http://www.thebackshed.com/forum/forum_posts.asp?TID=3574

so it would not be surprising if Jaycar discontinued this.

Kalex in Melbourne: http://www.kalex.net.au advertise 1.6mm single-sided
Riston-coated PCB material in their pricelist. I called them and was
told that this is only for large quantity - they don't keep any in stock.

I couldn't find any other sources of FR4 already coated with Riston, so
this lead me to buying the Riston film itself, and looking at techniques
for laminating it to the PCB material. This will allow me to choose
1.6mm and 0.8mm material with normal (1 ounce) copper or thinner (0.5
oz) copper. I understand the finer tracks can be achieved with the
thinner copper because the etch time is reduced, leaving less time to
undercut the photoresist, and I guess with the copper being thinner and
less accessible to the etchant. If I get adventurous I may even try
double-sided PCBs.

This is for prototyping - and for the satisfaction of making things at home.

The Riston information is at:

*
http://www2.dupont.com/Imaging_Materials/en_US/tech_info/product_selector.ht
ml

I found 3 sources of Riston film. I also found some Chinese sources of
generally un-named dry negative photoresist film. The last one mentions
it is Hitachi photoresist:

* http://stores.ebay.com/Led-Light-Bulb-World/_i.html?_nkw=photoresist
* http://stores.ebay.com/Digole-Digital-Solution/_i.html?_nkw=photoresist
* http://stores.ebay.com/oneworldonedream2010/_i.html?_nkw=photoresist
* www.ebay.com/sch/dr_ho_000/m.html

The first Riston source is Think and Tinker in the USA. They sell rolls
of "M115", which I assume means Riston MM115 or MM115i. This is 50
microns thick. However, I don't need such large quantities.

http://www.thinktink.com/products/Photopolymers.asp

The second source is in Sweden. They sell sheets of Riston FX515 which
is 15 microns thick.

* http://www.ebay.com/sch/karass/m.html

The third source is in the Czech Republic. They sell A5 sheets of
Riston MM540. This is 38 micron. I ordered some sheets today.

* http://www.ebay.com/sch/gaminn/m.html

Can anyone comment on the merits of Riston or alternative brands of
negative photoresist, or on the three thicknesses: 15um, 38um and 50um?

- Robin Melbourne Australia http://www.firstpr.com.au/rwi/dfish/





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

Hi Robin, I use Kinsten precoated board from Kalex and find it excellent, 
the difference being it is positive acting resist!. Look in the Kalex 
catalogue for the sizes and prices. I use 7 grams of caustic soda to 1 litre 
of warm water to dissolve the caustic as a developer and acrylic thinners to 
clean it off after exposure. Exposure is with 4 15w black lights for approx 
80 seconds. They also have polyester translucent sheets which I use to print 
the pattern with a laser printer and contact expose directly on to the 
sensitisized board sandwiched between 2 pieces of 0.25" glass and the lamps 
are about 3" above the glass. I have never had a failure yet after a couple 
of tries initially to get the settings right.
My 2 cents worth. Been there and done that and now would not even give 
Riston a second look!

Don VK3YV  ......
----- Original Message ----- 
From: "Robin Whittle" <rw@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, May 18, 2012 1:12 AM
Subject: [Homebrew_PCBs] Riston precoated FR4 in Australia, Riston sheets 
and rolls

>I am a newbie to this list and am keen to set up for using Riston
> (negative) photoresist for making small quantities of relatively small
> PCBs.  I used it in mid-1980s but then I had a process camera and could
> make really good phototools.
>
> The developer and stripper chemicals are cheap and easy - sodium
> carbonate (washing soda) and caustic soda respectively.
>
> My initial tests with a novel exposure technique are encouraging - I
> will describe this in another message.
>
> It is possible to buy Riston coated single-sided 1.6mm FR4 PCB material
> in Australia:  (Asterisks added to force indents in the Yahoo Groups
> archives, which gobble leading spaces.)
>
> *  http://www.jaycar.com.au/productView.asp?ID=HG9970
>
> but it is expensive: $24.95 for 152 x 152mm (6 inches square).  This is
> what I used for tests.  According to the instructions in the pack, this
> material comes from http://www.rcsradio.com.au, a business established
> in 1943 but which has ceased trading since the proprietor Bob Barnes died:
>
> *  http://www.thebackshed.com/forum/forum_posts.asp?TID=3574
>
> so it would not be surprising if Jaycar discontinued this.
>
> Kalex in Melbourne: http://www.kalex.net.au advertise 1.6mm single-sided
> Riston-coated PCB material in their pricelist.  I called them and was
> told that this is only for large quantity - they don't keep any in stock.
>
> I couldn't find any other sources of FR4 already coated with Riston, so
> this lead me to buying the Riston film itself, and looking at techniques
> for laminating it to the PCB material.  This will allow me to choose
> 1.6mm and 0.8mm material with normal (1 ounce) copper or thinner (0.5
> oz) copper.  I understand the finer tracks can be achieved with the
> thinner copper because the etch time is reduced, leaving less time to
> undercut the photoresist, and I guess with the copper being thinner and
> less accessible to the etchant.  If I get adventurous I may even try
> double-sided PCBs.
>
> This is for prototyping - and for the satisfaction of making things at 
> home.
>
> The Riston information is at:
>
> *
> http://www2.dupont.com/Imaging_Materials/en_US/tech_info/product_selector.html
>
> I found 3 sources of Riston film.  I also found some Chinese sources of
> generally un-named dry negative photoresist film.  The last one mentions
> it is Hitachi photoresist:
>
> *  http://stores.ebay.com/Led-Light-Bulb-World/_i.html?_nkw=photoresist
> *  http://stores.ebay.com/Digole-Digital-Solution/_i.html?_nkw=photoresist
> *  http://stores.ebay.com/oneworldonedream2010/_i.html?_nkw=photoresist
> *  www.ebay.com/sch/dr_ho_000/m.html
>
>
> The first Riston source is Think and Tinker in the USA.  They sell rolls
> of "M115", which I assume means Riston MM115 or MM115i.  This is 50
> microns thick.  However, I don't need such large quantities.
>
>  http://www.thinktink.com/products/Photopolymers.asp
>
> The second source is in Sweden.  They sell sheets of Riston FX515 which
> is 15 microns thick.
>
> * http://www.ebay.com/sch/karass/m.html
>
> The third source is in the Czech Republic.  They sell A5 sheets of
> Riston MM540.  This is 38 micron.  I ordered some sheets today.
>
> *  http://www.ebay.com/sch/gaminn/m.html
>
> Can anyone comment on the merits of Riston or alternative brands of
> negative photoresist, or on the three thicknesses: 15um, 38um and 50um?
>
>  - Robin   Melbourne Australia    http://www.firstpr.com.au/rwi/dfish/
>
>
>
>
>
>
> ------------------------------------
>
> 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 went down a similar track a few years ago Robin, as I had a stock of 
Riston pre-coated board inherited from a closed major electronics 
workshop. The problem I struck was that the box of 3M reversing film 
that I had bought some 20+ years earlier had "gone-off" and would no 
longer function. I was unable to locate a source of the film, as by then 
3M had ceased production.

I guess I might have been able to overcome the absence of a negative by 
using one of the PC packages that can produce a negative print from 
positive artwork but I ran out of time to experiment along those lines. 
At that point I switched over to Kinsten positive board, which you will 
see is also stocked by Kalex in Melbourne.

Sorry I cant be of help with your specific questions but I have read 
reports that one of the Chinese eBay sources you mention has a reliable 
product in his negative film. I don't have the source on this machine 
but I can probably find it and post later.

Bill
On 18/05/2012 3:54 AM, Boman33 wrote:
> Thanks for a detailed post with good information.
>
> A quick question:  Why not also consider positive resist?
>
> =============================
>
> From:  Robin Whittle  Sent: Thursday, May 17, 2012 11:12
> I am a newbie to this list and am keen to set up for using Riston
> (negative) photoresist for making small quantities of relatively small
> PCBs. I used it in mid-1980s but then I had a process camera and could
> make really good phototools.
>
> The developer and stripper chemicals are cheap and easy - sodium
> carbonate (washing soda) and caustic soda respectively.
>
> My initial tests with a novel exposure technique are encouraging - I
> will describe this in another message.
>
> It is possible to buy Riston coated single-sided 1.6mm FR4 PCB material
> in Australia: (Asterisks added to force indents in the Yahoo Groups
> archives, which gobble leading spaces.)
>
> * http://www.jaycar.com.au/productView.asp?ID=HG9970
>
> but it is expensive: $24.95 for 152 x 152mm (6 inches square). This is
> what I used for tests. According to the instructions in the pack, this
> material comes from http://www.rcsradio.com.au, a business established
> in 1943 but which has ceased trading since the proprietor Bob Barnes died:
>
> * http://www.thebackshed.com/forum/forum_posts.asp?TID=3574
>
> so it would not be surprising if Jaycar discontinued this.
>
> Kalex in Melbourne: http://www.kalex.net.au advertise 1.6mm single-sided
> Riston-coated PCB material in their pricelist. I called them and was
> told that this is only for large quantity - they don't keep any in stock.
>
> I couldn't find any other sources of FR4 already coated with Riston, so
> this lead me to buying the Riston film itself, and looking at techniques
> for laminating it to the PCB material. This will allow me to choose
> 1.6mm and 0.8mm material with normal (1 ounce) copper or thinner (0.5
> oz) copper. I understand the finer tracks can be achieved with the
> thinner copper because the etch time is reduced, leaving less time to
> undercut the photoresist, and I guess with the copper being thinner and
> less accessible to the etchant. If I get adventurous I may even try
> double-sided PCBs.
>
> This is for prototyping - and for the satisfaction of making things at home.
>
> The Riston information is at:
>
> *
> http://www2.dupont.com/Imaging_Materials/en_US/tech_info/product_selector.ht
> ml
>
> I found 3 sources of Riston film. I also found some Chinese sources of
> generally un-named dry negative photoresist film. The last one mentions
> it is Hitachi photoresist:
>
> * http://stores.ebay.com/Led-Light-Bulb-World/_i.html?_nkw=photoresist
> * http://stores.ebay.com/Digole-Digital-Solution/_i.html?_nkw=photoresist
> * http://stores.ebay.com/oneworldonedream2010/_i.html?_nkw=photoresist
> * www.ebay.com/sch/dr_ho_000/m.html
>
> The first Riston source is Think and Tinker in the USA. They sell rolls
> of "M115", which I assume means Riston MM115 or MM115i. This is 50
> microns thick. However, I don't need such large quantities.
>
> http://www.thinktink.com/products/Photopolymers.asp
>
> The second source is in Sweden. They sell sheets of Riston FX515 which
> is 15 microns thick.
>
> * http://www.ebay.com/sch/karass/m.html
>
> The third source is in the Czech Republic. They sell A5 sheets of
> Riston MM540. This is 38 micron. I ordered some sheets today.
>
> * http://www.ebay.com/sch/gaminn/m.html
>
> Can anyone comment on the merits of Riston or alternative brands of
> negative photoresist, or on the three thicknesses: 15um, 38um and 50um?
>
> - Robin Melbourne Australia http://www.firstpr.com.au/rwi/dfish/
>
>
>
>
>
> [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
>
>
>
>


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

Hi Boman33, Don and Bill,

I am responding to your replies to my message "Riston precoated FR4 in
Australia, Riston sheets and rolls".

I am pursuing Riston, or potentially other negative photoresist films,
because its my impression it can reliably produce finer lines than the
other alternatives.

For instance, from this list (2012-02-14):

*  http://tech.groups.yahoo.com/group/Homebrew_PCBs/message/29673

Bob Balderstone wrote to the effect that Toner Transfer was not as easy
or repeatable as Riston type laminated film, that spray-on or sponge-on
photoresists don't work, and that "pre-coated boards" (negative,
positive? - at least as distinct from laminating your own Riston
negative resist) were:

>> Good sometimes but expensive and sometimes poorly cut
>> (raised edges have to be filed down before exposure)
>> and occasionally unevenly coated meaning it's hard to
>> get consistent results. My experience is they have a
>> shelf-life (older = longer exposure time) which again
>> causes inconsistencies if you don't make many boards
>> at one go.

I have read about toner transfer, and my impression is that it would be
tricky to get the transfer lamination process working reliably, with
expensive transfer film required for each attempt.  Also, it is clear
from the Pulsar documentation:

*  http://www.pcbfx.com/main_site/pages/direct_etch/the_8min_pcb.html

that the toner itself is not good enough, so there has to be a second
step of applying a "Green TRF foil" so the combined bonded "foil" and
toner will keep the etchant reliably off the copper.

These steps involve melting the toner on a flat surface and pressing it,
so I would expect it to spread out and so make lines wider, with fuzzier
edges.

If I can laminate my own Riston or similar to FR4 material, rather than
buy pre-laminated FR4 material, then I can choose whatever thickness of
FR4 I want, with one or two copper layers, with the copper thickness
whatever I want, without having bunches of laminated boards degrading
over time.

I have some single-sided Riston FR4 from the 1980s.  It is all
polymerized dark blue - so it can't be used.  I understand the thin
mylar film is to protect the Riston from oxidation, which I guess causes
the photoresist to polymerize.  I guess this can be avoided if the dry
film is stored correctly.  Maybe it goes off after a few years, but the
dry film is cheap.  Pre-laminated Riston FR4 boards are difficult or
impossible to obtain and would be much more expensive.

The low cost and simplicity of Riston developer and stripper would be
hard to beat.

There are plenty of etching options, so the remaining problems are:

1 - Choose and purchase some Riston film.  I should have some 38 micron
    MM540 in the next few weeks.

2 - Figure out how to laminate it onto single and double sided boards
    - probably A5 size will be fine for me.  I will write a separate
    message about the laminator I bought today.

3 - Expose the Riston without too much fuss.  I have a promising
    technique which I will write to the list about once I have tested
    it further.

 - Robin

Hi Robin,

I 100% agree with you about the limited performance of toner transfer.

My question is: why exclude positive resist options?

 

Years ago I used to make custom prototype PCBs but now I am too busy so I
usually order the quick turnaround PCBs.

 

Independently of the photo resist is a question of how to generate high
contrast fine line artwork.

 

You can find resolution charts and printer testing info on my website:

http://www.vinland.com/USAF-1951.html

 

Have a great weekend!

Bertho

-----Original Message-----
From: Robin Whittle [mailto:rw@...] 
Sent: Friday, May 18, 2012 10:32
To: Homebrew_PCBs@yahoogroups.com
Cc: Bill Maxwell; Boman33; VK3YV
Subject: Why use Riston or some other negative photoresist dry film?

 

Hi Boman33, Don and Bill,

 

I am responding to your replies to my message "Riston precoated FR4 in
Australia, Riston sheets and rolls".

 

I am pursuing Riston, or potentially other negative photoresist films,
because its my impression it can reliably produce finer lines than the other
alternatives.

 

For instance, from this list (2012-02-14):

 

*   <http://tech.groups.yahoo.com/group/Homebrew_PCBs/message/29673>
http://tech.groups.yahoo.com/group/Homebrew_PCBs/message/29673

 

Bob Balderstone wrote to the effect that Toner Transfer was not as easy or
repeatable as Riston type laminated film, that spray-on or sponge-on
photoresists don't work, and that "pre-coated boards" (negative, positive? -
at least as distinct from laminating your own Riston negative resist) were:

 

>> Good sometimes but expensive and sometimes poorly cut (raised edges 

>> have to be filed down before exposure) and occasionally unevenly 

>> coated meaning it's hard to get consistent results. My experience is 

>> they have a shelf-life (older = longer exposure time) which again 

>> causes inconsistencies if you don't make many boards at one go.

 

I have read about toner transfer, and my impression is that it would be
tricky to get the transfer lamination process working reliably, with
expensive transfer film required for each attempt.  Also, it is clear from
the Pulsar documentation:

 

*   <http://www.pcbfx.com/main_site/pages/direct_etch/the_8min_pcb.html>
http://www.pcbfx.com/main_site/pages/direct_etch/the_8min_pcb.html

 

that the toner itself is not good enough, so there has to be a second step
of applying a "Green TRF foil" so the combined bonded "foil" and toner will
keep the etchant reliably off the copper.

 

These steps involve melting the toner on a flat surface and pressing it, so
I would expect it to spread out and so make lines wider, with fuzzier edges.

 

If I can laminate my own Riston or similar to FR4 material, rather than buy
pre-laminated FR4 material, then I can choose whatever thickness of

FR4 I want, with one or two copper layers, with the copper thickness
whatever I want, without having bunches of laminated boards degrading over
time.

 

I have some single-sided Riston FR4 from the 1980s.  It is all polymerized
dark blue - so it can't be used.  I understand the thin mylar film is to
protect the Riston from oxidation, which I guess causes the photoresist to
polymerize.  I guess this can be avoided if the dry film is stored
correctly.  Maybe it goes off after a few years, but the dry film is cheap.
Pre-laminated Riston FR4 boards are difficult or impossible to obtain and
would be much more expensive.

 

The low cost and simplicity of Riston developer and stripper would be hard
to beat.

 

There are plenty of etching options, so the remaining problems are:

 

1 - Choose and purchase some Riston film.  I should have some 38 micron

    MM540 in the next few weeks.

 

2 - Figure out how to laminate it onto single and double sided boards

    - probably A5 size will be fine for me.  I will write a separate

    message about the laminator I bought today.

 

3 - Expose the Riston without too much fuss.  I have a promising

    technique which I will write to the list about once I have tested

    it further.

 

- Robin

 



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

Hi Bertho,

Thanks for the link to your test charts.  I will use these when I have
the Riston film in a few weeks time.  At present I only have a small
piece of already-coated board.

You wrote:

> I 100% agree with you about the limited performance of toner transfer.
> 
> My question is: why exclude positive resist options?

I haven't excluded them.  Are positive photoresists available as film
for lamination at home, or is it necessary to buy already-coated boards?
 If the latter, then I think the result may be higher costs than DIY
lamination of negative photoresist films such as Riston, possibly with
greater difficulty of obtaining whatever FR4 thickness and copper
thickness might be desired.

I don't know about shelf-life of Riston film, shelf-life of FR4 material
which has had this film applied, and likewise shelf-life of positive
film and positive-coated boards.

However, in the message I quoted:

*  http://tech.groups.yahoo.com/group/Homebrew_PCBs/message/29673

Bob Balderstone wrote of pre-coated boards (negative or positive reist?):

>> My experience is they have a shelf-life (older = longer exposure
>> time) which again causes inconsistencies if you don't make many
>> boards at one go.

He mentioned no shelf-life problems with Riston-type (positive
photoresist) film:

>> Very, very good indeed once you've mastered the art
>> of laminating. Definitely worth shelling out the ?10 or so for a
>> cheapo laminator. Very cheap chemistry. No shelf life that I've
>> seen. Very consistent results. Can also be used as a poor man's
>> solder mask. Buy flat sheets (eBay China) not the cheap roll ends
>> which curl up every other whichway when you're trying to apply it.


 - Robin

Understood Robin, although I have not encountered problems with the 
Kinsten positive pcb in terms of registration or under-cutting etc.

I must check my Riston stock for polmerization, as it is also of 1980s 
vintage. Last time I looked, about 7 years ago, it was still red.

cheers
Bill, VK7MX

On 19/05/2012 12:31 AM, Robin Whittle wrote:
> Hi Boman33, Don and Bill,
>
> I am responding to your replies to my message "Riston precoated FR4 in
> Australia, Riston sheets and rolls".
>
> I am pursuing Riston, or potentially other negative photoresist films,
> because its my impression it can reliably produce finer lines than the
> other alternatives.
>
> For instance, from this list (2012-02-14):
>
> *  http://tech.groups.yahoo.com/group/Homebrew_PCBs/message/29673
>
> Bob Balderstone wrote to the effect that Toner Transfer was not as easy
> or repeatable as Riston type laminated film, that spray-on or sponge-on
> photoresists don't work, and that "pre-coated boards" (negative,
> positive? - at least as distinct from laminating your own Riston
> negative resist) were:
>
>>> Good sometimes but expensive and sometimes poorly cut
>>> (raised edges have to be filed down before exposure)
>>> and occasionally unevenly coated meaning it's hard to
>>> get consistent results. My experience is they have a
>>> shelf-life (older = longer exposure time) which again
>>> causes inconsistencies if you don't make many boards
>>> at one go.
> I have read about toner transfer, and my impression is that it would be
> tricky to get the transfer lamination process working reliably, with
> expensive transfer film required for each attempt.  Also, it is clear
> from the Pulsar documentation:
>
> *  http://www.pcbfx.com/main_site/pages/direct_etch/the_8min_pcb.html
>
> that the toner itself is not good enough, so there has to be a second
> step of applying a "Green TRF foil" so the combined bonded "foil" and
> toner will keep the etchant reliably off the copper.
>
> These steps involve melting the toner on a flat surface and pressing it,
> so I would expect it to spread out and so make lines wider, with fuzzier
> edges.
>
> If I can laminate my own Riston or similar to FR4 material, rather than
> buy pre-laminated FR4 material, then I can choose whatever thickness of
> FR4 I want, with one or two copper layers, with the copper thickness
> whatever I want, without having bunches of laminated boards degrading
> over time.
>
> I have some single-sided Riston FR4 from the 1980s.  It is all
> polymerized dark blue - so it can't be used.  I understand the thin
> mylar film is to protect the Riston from oxidation, which I guess causes
> the photoresist to polymerize.  I guess this can be avoided if the dry
> film is stored correctly.  Maybe it goes off after a few years, but the
> dry film is cheap.  Pre-laminated Riston FR4 boards are difficult or
> impossible to obtain and would be much more expensive.
>
> The low cost and simplicity of Riston developer and stripper would be
> hard to beat.
>
> There are plenty of etching options, so the remaining problems are:
>
> 1 - Choose and purchase some Riston film.  I should have some 38 micron
>      MM540 in the next few weeks.
>
> 2 - Figure out how to laminate it onto single and double sided boards
>      - probably A5 size will be fine for me.  I will write a separate
>      message about the laminator I bought today.
>
> 3 - Expose the Riston without too much fuss.  I have a promising
>      technique which I will write to the list about once I have tested
>      it further.
>
>   - Robin
>
>
>
> ------------------------------------
>
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>
>
>
>


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