Homebrew_PCBs

Since Kepro went out of business, I need to find a new supplier of
presensized negative acting photoresist material . I tried some positive
material from Injectorall, but can't seem to get a decent board from it. I'm
sure it will work after I figure out the correct process, but that can get
pretty expensive.

Ideally I'd like to find some place that provides the same type of material
as Kepro had. It was a 1.3mil thick laminated negative acting photoresist,
Riston EM312 Photopolymer film made by Dupont. It was developed with sodium
carbonate.

Any ideas
Ron

>Since Kepro went out of business, I need to find a new supplier of
>presensized negative acting photoresist material . I tried some positive
>material from Injectorall, but can't seem to get a decent board from it. I'm
>sure it will work after I figure out the correct process, but that can get
>pretty expensive.
>
>Ideally I'd like to find some place that provides the same type of material
>as Kepro had. It was a 1.3mil thick laminated negative acting photoresist,
>Riston EM312 Photopolymer film made by Dupont. It was developed with sodium
>carbonate.

Isn't Bungard also selling in the us (asuming you live there)? They do
have a photoresist from an english manufacturer (sorry, don't have the
name handy) and the resist works very well. From what you describe it
seems to be mostly the same thing as you had.

Markus

Ron,

Let me know if you need help with laminated panels. I have a dry film
laminator and use a resist similar to the DuPont material. The resist
I use is called ETERTEC HQ6015. It is 1.5 mils thick and processes
the same as the DuPont 4015 we used in the past. Exposure time is 17
seconds when using a Colight DMVL-930 exposure unit with 1.5 Kw lamps.
Development is in 1% sodium carbonate. Resist stripping uses a weak
sodium hydroxide solution heated to about 120 degress F. This resist
can be stripped at room temperature with longer process times.

I can supply single or double sided panels laminated with this resist
and sealed in opaque black poly bags. Contact me off list with your
requirements if you are interested in these materials.

Tom


--- In Homebrew_PCBs@yahoogroups.com, "Ron Amundson"
<ron_amundson@h...> wrote:

> Since Kepro went out of business, I need to find a new supplier of
> presensized negative acting photoresist material . I tried some

positive

> material from Injectorall, but can't seem to get a decent board

from it. I'm

> sure it will work after I figure out the correct process, but that

can get

> pretty expensive.
>
> Ideally I'd like to find some place that provides the same type of

material

> as Kepro had. It was a 1.3mil thick laminated negative acting

photoresist,

> Riston EM312 Photopolymer film made by Dupont. It was developed

with sodium

> carbonate.
>
> Any ideas
> Ron

Try contacting a local PCB fabricator and see if they will
sell you the last 10 meters off the dry film rolls, when
they next do a change over on the hot roll laminator. You
might like to cut it in 300x300mm squares for convenience,
then store in black plastic bag, in the fridge, and it will
last for many years.

As for the applying the film, I've finally got it worked
out. You need to get hold of a rubber roller like that from
ink printing machinery. Here, I took a few photos to show
basically what I use to put the film on the board and
process the photoresist. Excuse some of the poor quality
photos, I wasn't taking my time to do a better job.


http://members.optusnet.com.au/~eseychell/pictures


These two images show a magnified view of a pattern in the
photomask and the same pattern developed on the photoresist.

http://members.optusnet.com.au/~eseychell/pictures/Epson_inkjet_film.jpg
http://members.optusnet.com.au/~eseychell/pictures/resist_image_on_copper.jpg

Ron Amundson wrote:

> Since Kepro went out of business, I need to find a new supplier of
> presensized negative acting photoresist material . I tried some positive
> material from Injectorall, but can't seem to get a decent board from it. I'm
> sure it will work after I figure out the correct process, but that can get
> pretty expensive.
>
> Ideally I'd like to find some place that provides the same type of material
> as Kepro had. It was a 1.3mil thick laminated negative acting photoresist,
> Riston EM312 Photopolymer film made by Dupont. It was developed with sodium
> carbonate.
>
> Any ideas
> Ron
>

I should add some explanation to the photos I took earlier
and uploaded to the following location;
http://members.optusnet.com.au/~eseychell/pictures

The dry film I'm using is a product from MacDermid part
number AquaMer MP215. Its dated 1998, but still seems to
work perfectly fine for me. I bought it about 2 years ago
from a guy who owns a small PCB fab shop and he sold be
about 20~30 meter roll for AU$20. I store it in the fridge
just to be safe. Its appears to be a high sensitivity type
of resist, since exposure takes less than 10 seconds in
direct sunlight on a summer day.

I had built a hand roller to apply the film. The design of
the roller is based on many hours of experimenting with dry
film, and learning how to get the stuff on without wrinkles,
or trapped air bubbles and relatively free of contaminants.
The technique uses a film of hot water on the surface of the
copper while the the resist is being applied by a roller
with an even pressure. The idea of using water came to me
after reading articles about "wet lamination" published on
PCB industrial web sites. I have found the water has three
major advantages over dry hot rolling.
1) It virtually eliminates the wrinkling problem because the
film does not instantaneously bond to the copper, allowing
some movement as the film contacts the copper.
2) Trapped air bubbles are reduced because the water
displaces air.
3) Dust and surface contaminates are dramatically reduced
since the water washes the surface clean. This is probably
the most biggest benefit.

http://members.optusnet.com.au/~eseychell/pictures/roller_bottom_view.JPG
A bottom view of the hand roller is shown in this photo;
The red board screwed to steel right angle is a support for
the resist while rolling on the film (see later photos).

http://members.optusnet.com.au/~eseychell/pictures/micro_etch.JPG
After scrubbing the PCB clean with caustic engine degreaser
I dip in room temp ammonium persulfate for 20 seconds to
further clean the copper and roughen its surface. This step
increases photoresist bonding.

http://members.optusnet.com.au/~eseychell/pictures/cut_to_size.JPG
The film is cut to a size just a bit smaller than the PCB so
it will leave one edge uncovered a few millimeters.


http://members.optusnet.com.au/~eseychell/pictures/remove_protective_film.JPG
The resist is laid on the board and the polyethylene
protective film is removed. The film is then pulled over the
roller so it wraps around about halfway. Its important to
keep the film square with the roller so it doesn't move off
to one side when rolling on the PCB. I draw a series of
lines on the red board to help square up the film.

http://members.optusnet.com.au/~eseychell/pictures/boiling_water.JPG
Boiling water is pored over the PCB to both heat and wet it.
The heat makes the film soft and bonds strongly to the
copper surface. The PCB is laying on a large block of
polystyrene foam.


http://members.optusnet.com.au/~eseychell/pictures/roll_application.JPG
This is the actual rolling on of the film. I apply pressure
(sorry no numbers) and slowly move forward.

http://members.optusnet.com.au/~eseychell/pictures/resist_applied.JPG
This photo is of the PCB after the resist is applied.

http://members.optusnet.com.au/~eseychell/pictures/after_exposure.JPG
After exposure you can see the faint image of the masked
pattern in the resists. The resist becomes pinker after
exposure. In this photo I'm pealing away the protective
Mylar film from the resist. The main purpose of the Mylar
film is to act as an oxygen barrier during exposure.

http://members.optusnet.com.au/~eseychell/pictures/developing.JPG
The typical developing method shown here. A solution of
10g/L sodium carbonate heated 30°C to 40°C.

http://members.optusnet.com.au/~eseychell/pictures/resist_processing_finished.JPG
The board after developing is rinsed and microetched once
again to remove any traces of resist. Placing the PCB in an
acidic solution also stops continuing developing of the
resist, which can otherwise lead to "furry edges" if left
too long (1+ minutes). The next step will the remainder of
the pattern plating process, i.e. tin plating followed by
photoresist strip and alkaline copper etch. This method is
not the normal hobbyist way, so typically a negative
photomask will be used with a negative acting dry film
photoresist followed by copper etching in FeCl3, ect.


http://members.optusnet.com.au/~eseychell/pictures/Epson_inkjet_film.jpg
http://members.optusnet.com.au/~eseychell/pictures/resist_image_on_copper.jpg
Out of curiosity I took some microscope shots of the
photomask pattern and the same pattern in the developed
photoresist (after "microetched"). This is good indication
the processes went ok, at least in this part of the artwork :).

regards,

Adam

But i still don't really know which advantage the dry (wet) film has.
May you lay out the advantages compared to presensitized boards?
As i understand it is only a method of applying photoresist?
The only advantage i see is when using rotary drum-like laser exposure
plotter.
Sure it is good for something - you wouldn't use it if not... please tell
me.

thanks..
st


...snip

>But i still don't really know which advantage the dry (wet) film has.
>May you lay out the advantages compared to presensitized boards?
>As i understand it is only a method of applying photoresist?
>The only advantage i see is when using rotary drum-like laser exposure
>plotter.
>Sure it is good for something - you wouldn't use it if not... please tell
>me.
>
>thanks..
>st

Hi Stefan

I use photoresist because of through hole plating process
requirements. Only with this resist I can cover the holes after the
through hole plating (and of course for the plating process the boards
can't be coated with photoresist).

Apart of this, I can also achive finer layouts using the resist.

Just the reasons why I use the resist. As elsewhere mentioned I'm
using the one available from Bungard. I'm laminating it using an
office laminator (GBC 1200).

HTH

Markus

On Mon, 29 Sep 2003 15:49:50 +0200, Markus Zingg <m.zingg@...> wrote:

>> But i still don't really know which advantage the dry (wet) film has.
>> May you lay out the advantages compared to presensitized boards?
>> As i understand it is only a method of applying photoresist?
>> The only advantage i see is when using rotary drum-like laser exposure
>> plotter.
>> Sure it is good for something - you wouldn't use it if not... please
>> tell me.
>>
>> thanks..
>> st
>
> Hi Stefan
>
> I use photoresist because of through hole plating process
> requirements. Only with this resist I can cover the holes after the
> through hole plating (and of course for the plating process the boards
> can't be coated with photoresist).
>
> Apart of this, I can also achive finer layouts using the resist.
>
> Just the reasons why I use the resist. As elsewhere mentioned I'm
> using the one available from Bungard. I'm laminating it using an
> office laminator (GBC 1200).
>
> HTH
>
> Markus

hi markus...

i see, for hole covering it is a good method (maybe the only).
i did know that but somehow didn't think of it....
but you all expose the film after laminating?

maybe it can be exposed by putting it into a laser printer assembly before
lamination?
i think you know the bungard "barrel" exposure unit?
what do you think?

mfg
stefan

>
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>
>

>hi markus...
>
>i see, for hole covering it is a good method (maybe the only).
>i did know that but somehow didn't think of it....
>but you all expose the film after laminating?

Well - all - I don't know, but for me this is a must. Otherwise it
will not work.

>maybe it can be exposed by putting it into a laser printer assembly before
>lamination?

Well, never tried something like this and I highly doubht if the
laminage I use would survive the temperatures that the fixing unit of
a laser imposes. Apart of this - nice idea indeed. But then again, I
don't think that this would work out reasonably well when it comes to
double sided or multilayers because of the difficulties with
laminating this precisely enough. Laminating is a bit tricky -
especially if the envireonemental temperature goes above 30 degrees C
(86 degrees farenheit) as it happened often this summer.

>i think you know the bungard "barrel" exposure unit?
>what do you think?

No, not really. I use a home built exposure unit adn havne't looked
much around in this area. I also must say that I'm menawhile really
fully doing this the "chemical" way and so far I'm very happy. Once
you start to through hole plate, you need that many chemicals that
developing, exposing and makeing films etc. does not really matter
that much anymore. Of course I do agree that other ways could be
combined etc...

Markus

i think i described it not precise enough..
(expected you know the bungard "barrel" exposure plotter).

The idea is to put the film on a drum (before laminating).
this drum rotates and a laser exposed one line a time.
(this is what i THINK the bungard unit works - never seen one).

for use in laser plotter i did think of somehow mounting the film on the
photodrum
and having it exposed by the laser. (tus no run through fuser etc.)
- would require severe printer conversion thus a separate unit....

main problems:
a) mechanical - just some tinkering
b) more important for me: optical
do you know if the laser wavelength, power/area, and exposure time may
suit photoresist?
i fear not. (sensitivity of photo-drum and film(at wavelength) would
require comparision)


I understand there would be alignment problems with double sided - but the
alignment when exposing after lamination also needs care.

if the laser in a simple and cheap laser printer would be suited to expose
dry film
without needing to change exposure time (much work i guess) it would be
very interesting
for me (you know i have a lot of problems with this plotter method)



stefan

On Mon, 29 Sep 2003 18:06:28 +0200, Markus Zingg <m.zingg@...> wrote:

>> hi markus...
>>
>> i see, for hole covering it is a good method (maybe the only).
>> i did know that but somehow didn't think of it....
>> but you all expose the film after laminating?
>
> Well - all - I don't know, but for me this is a must. Otherwise it
> will not work.
>
>> maybe it can be exposed by putting it into a laser printer assembly
>> before lamination?
>
> Well, never tried something like this and I highly doubht if the
> laminage I use would survive the temperatures that the fixing unit of
> a laser imposes. Apart of this - nice idea indeed. But then again, I
> don't think that this would work out reasonably well when it comes to
> double sided or multilayers because of the difficulties with
> laminating this precisely enough. Laminating is a bit tricky -
> especially if the envireonemental temperature goes above 30 degrees C
> (86 degrees farenheit) as it happened often this summer.
>
>> i think you know the bungard "barrel" exposure unit?
>> what do you think?
>
> No, not really. I use a home built exposure unit adn havne't looked
> much around in this area. I also must say that I'm menawhile really
> fully doing this the "chemical" way and so far I'm very happy. Once
> you start to through hole plate, you need that many chemicals that
> developing, exposing and makeing films etc. does not really matter
> that much anymore. Of course I do agree that other ways could be
> combined etc...
>
> Markus
>
>
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
>
> To unsubscribe from this group, send an email to:
> Homebrew_PCBs-unsubscribe@yahoogroups.com
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>

Hi Stefan

Reading my post again, I must have been in a real hurry typing it :)

>i think i described it not precise enough..
>(expected you know the bungard "barrel" exposure plotter).
>
>The idea is to put the film on a drum (before laminating).
>this drum rotates and a laser exposed one line a time.
>(this is what i THINK the bungard unit works - never seen one).

I see.. Well, again, I'm out of the experimenting stage for the
moment. My methods work so well for me that my motivation to change
things is really low. :)

>for use in laser plotter i did think of somehow mounting the film on the
>photodrum
>and having it exposed by the laser. (tus no run through fuser etc.)
>- would require severe printer conversion thus a separate unit....
>
>main problems:
>a) mechanical - just some tinkering
>b) more important for me: optical
> do you know if the laser wavelength, power/area, and exposure time may
>suit photoresist?
>i fear not. (sensitivity of photo-drum and film(at wavelength) would
>require comparision)

Sorry - no idea. How about calling Bungard? I found that Mr. Bungard
is very helpfull and is having a heart for "Homebrewers". I got a
great deal of support with tips etc. back when I was building my
through plating machine. I'm very sure he's willing to give you
information.

>
>I understand there would be alignment problems with double sided - but the
>alignment when exposing after lamination also needs care.

Of course, I'm also convinced that you might be able to get these
things under control. But - again - for me printing on a foil
(zweckform 2502 type) using an epson stylus c62 does a wonderfull job.

>if the laser in a simple and cheap laser printer would be suited to expose
>dry film
>without needing to change exposure time (much work i guess) it would be
>very interesting
>for me (you know i have a lot of problems with this plotter method)

Again, I can imagine that exposing the film this way would be cool but
I do se severe difficuties when it comes to laminate this onoto the
PCB in alignement with other layers. The problem is that you then
would have to manage to laminate it to a very precisely defined area
of the PCB and after some experinece with laminating those materials I
can tell you that I'm usually happy if I manage to laminate wihouth
bubbles or other odities. That said, in order to laminate aligned you
also would have to build a special laminator to achive this purpose
and I think you probably will end up building a device that exposes
(using the laser) and laminates just in one shot.

Just my 2¢ though.

Markus

You are correct, its not a huge advantage being able to apply
your own "dry film photoresist" for conventional print and etch.
However, for producing plated through hole boards, the dry film
is mandatory. The only possible advantage I can see is that it
reduces cost, since blank PCB is much cheaper, especially if you
get off-cuts from fabricators. Although it sure is a _lot_ better
to use than spray on liquid resists, such as Electrolube PRP.
One other minor advantage is that if you mess up the exposure in
some way, you can easily strip the resist off and start again.

As far as I'm aware, photoresist can only be directly exposed
with very expensive UV lasers. Normally a red light sensitive
film is exposed with a laser to make a photomask, then the
photoresist is contact exposed under high power gas discharge UV
lamps.

Stefan Trethan wrote:

> But i still don't really know which advantage the dry (wet) film has.
> May you lay out the advantages compared to presensitized boards?
> As i understand it is only a method of applying photoresist?
> The only advantage i see is when using rotary drum-like laser exposure
> plotter.
> Sure it is good for something - you wouldn't use it if not... please tell
> me.
>
> thanks..
> st
>
>