Homebrew PCBs

Hi everyone,

I wonder if it is possible to use the photo sensitive Emulsion used in the silk screen making process directly on the blank PCB copper surface. I realize that in the silk screen process there is the silk mesh in which the emulsion gets trapped and then hardens to form the "screen". The idea that I would like to test is whether:

1.	Will the emulsion initially stick to the copper surface?
2.	Will a screen be formed on the copper surface as it does in the case of the silk screening process?

Any comments most appreciated.

Thanks and regards

Aurangzeb

The emulsion is between the theads... the screen is what holds it

-----Original Message-----
Date: Monday, June 22, 2009 8:20 am
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] Using Silk Screen Emulsion for PCB making
From: "aurangzebhaque" <aurangzebhaque@...>

Hi everyone,

I wonder if it is possible to use the photo sensitive Emulsion used in the silk screen making process directly on the blank PCB copper surface. I realize that in the silk screen process there is the silk mesh in which the emulsion gets trapped and then hardens to form the "screen". The idea that I would like to test is whether:

1.	Will the emulsion initially stick to the copper surface?
2.	Will a screen be formed on the copper surface as it does in the case of the silk screening process?

Any comments most appreciated.

Thanks and regards

Aurangzeb

----- Original Message ----- 

From: "aurangzebhaque" <aurangzebhaque@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Monday, June 22, 2009 11:34 AM
Subject: [Homebrew_PCBs] Using Silk Screen Emulsion for PCB making


> Hi everyone,
>
> I wonder if it is possible to use the photo sensitive Emulsion used in the 
> silk screen making process directly on the blank PCB copper surface. I 
> realize that in the silk screen process there is the silk mesh in which 
> the emulsion gets trapped and then hardens to form the "screen". The idea 
> that I would like to test is whether:
>
> 1. Will the emulsion initially stick to the copper surface?
> 2. Will a screen be formed on the copper surface as it does in the case of 
> the silk screening process?

Silk screening used to be used for applying resist. We had a silk screen PCB 
making facility at English-Electric-Leo-Marconi Computers, Kidsgrove, when I 
was a student there in the 1960s. When the resist was dry, the boards were 
etched in the usual way. The silk screens had to be made photographically, 
of course, and they had a limited life.

Leon

Leon

That occurred to me, also.  I have some emulsion sitting around, 
although it may be out of date.
Other things to test:

3.   Will it resist etch?

4.   Can you get it thin and smooth enough?


The steps would be:

Clean board.
Coat with emulsion.
Let dry in dark room.
Print artwork to transparency, reversed and negative.
Place transparency over board, toner down.
Cover transparency with glass to keep everything flat.
Expose to direct sunlight for 60 seconds.
Wash board with water to remove unexposed emulsion.
Etch board.
Remove emulsion.

Acetone or Denatured alcohol might remove emulsion, saving a bit of 
money over emulsion remover.

Give it a try and report back to us!  ;)

Kerry


aurangzebhaque wrote:

> Hi everyone,
>
> I wonder if it is possible to use the photo sensitive Emulsion used in the silk screen making process directly on the blank PCB copper surface. I realize that in the silk screen process there is the silk mesh in which the emulsion gets trapped and then hardens to form the "screen". The idea that I would like to test is whether:
>
> 1.	Will the emulsion initially stick to the copper surface?
> 2.	Will a screen be formed on the copper surface as it does in the case of the silk screening process?
>
> Any comments most appreciated.
>
> Thanks and regards
>
> Aurangzeb
>

On Mon, 2009-06-22 at 10:34 +0000, aurangzebhaque wrote:
> I wonder if it is possible to use the photo sensitive Emulsion used in
> the silk screen making process directly on the blank PCB copper
> surface. I realize that in the silk screen process there is the silk
> mesh in which the emulsion gets trapped and then hardens to form the
> "screen". The idea that I would like to test is whether:
> 

I also think about it, not to use the 'emulsion' but to buy the
'sensiblizer' which is said to be benzenophenone, the same thing used in
dry films and i think also in LPI and dry film soldermask. 
I know an 'how to' full of pictures with the process. But is Brazilian.
All Portuguese/Spanish speakers will be fine others...

http://br.geocities.com/jaosan13/DicasCustomizacao/PhotoetchEmulsaoFotosensivel.html 

Some curious things there is that i talks about the emulsion (without
sensiblizer) that can be replaced with white hood glue (PVA - water
soluble also), and the not exposed emulsion he uses is washed with
simple water.

If you are willing to try, get the benzenophenone, and emulsion, or
acrylic resin (widely avaiable) or even de PVA glue. The acrylic resin
should behave like the dry film, develop with Na2CO3 and strip with
NaOH. But is my guess.

The silkscreen method use this emulsion to make the silkscreen, and
apply almost anything on the board with it. Acrylic based, epoxy based
(soldermask), oil based, even asphalt! But yes you can use it directly.
if you can do an uniform thick layer.

> 1. Will the emulsion initially stick to the copper surface?
> 2. Will a screen be formed on the copper surface as it does in the
> case of the silk screening process?
> 
> Any comments most appreciated.
> 
> Thanks and regards
> 
> Aurangzeb

>

Using silk screen emulsion,  it is worth a try,
The only thing I would be concerned with is the emulsion's adhesion to the
copper. Silk screens are made from very fine polyester fibers that have a
lot of surface area to "grab" onto and it is formulated for this.

Copper is a horse of another coleor.

Myc


On Mon, Jun 22, 2009 at 11:11 AM, Simao Cardoso <simaocardoso@...>wrote:

>
>
> On Mon, 2009-06-22 at 10:34 +0000, aurangzebhaque wrote:
> > I wonder if it is possible to use the photo sensitive Emulsion used in
> > the silk screen making process directly on the blank PCB copper
> > surface. I realize that in the silk screen process there is the silk
> > mesh in which the emulsion gets trapped and then hardens to form the
> > "screen". The idea that I would like to test is whether:
> >
>
> I also think about it, not to use the 'emulsion' but to buy the
> 'sensiblizer' which is said to be benzenophenone, the same thing used in
> dry films and i think also in LPI and dry film soldermask.
> I know an 'how to' full of pictures with the process. But is Brazilian.
> All Portuguese/Spanish speakers will be fine others...
>
>
> http://br.geocities.com/jaosan13/DicasCustomizacao/PhotoetchEmulsaoFotosensivel.html
>
> Some curious things there is that i talks about the emulsion (without
> sensiblizer) that can be replaced with white hood glue (PVA - water
> soluble also), and the not exposed emulsion he uses is washed with
> simple water.
>
> If you are willing to try, get the benzenophenone, and emulsion, or
> acrylic resin (widely avaiable) or even de PVA glue. The acrylic resin
> should behave like the dry film, develop with Na2CO3 and strip with
> NaOH. But is my guess.
>
> The silkscreen method use this emulsion to make the silkscreen, and
> apply almost anything on the board with it. Acrylic based, epoxy based
> (soldermask), oil based, even asphalt! But yes you can use it directly.
> if you can do an uniform thick layer.
>
> > 1. Will the emulsion initially stick to the copper surface?
> > 2. Will a screen be formed on the copper surface as it does in the
> > case of the silk screening process?
> >
> > Any comments most appreciated.
> >
> > Thanks and regards
> >
> > Aurangzeb
>
> >
>
>  
>


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

Simao,

Thanks for the excellent link. I am going to try it this weekend.

One comment. I have been making many many silkscreens using translucent tracing paper, with the design pattern printed out on common laser printer. I have never had the problem of opacity in the printout, and edges etc. have always been satisfactorily sharp. We use the sunlight here because it is abundant and free ;-), and the rays are parallel. Maybe you should try it too. Hopefully it will save you money on film.

And thanks everybody for your inputs.

Aurangzeb

On Tue, 2009-06-23 at 11:23 +0000, aurangzebhaque wrote:
> I have never had the problem of opacity in the printout, and edges
> etc. have always been satisfactorily sharp. We use the sunlight here
> because it is abundant and free ;-), and the rays are parallel. Maybe
> you should try it too. Hopefully it will save you money on film.

Me, i just use toner transfer, because is simpler, i wish to use direct
print for layout and soldermask if possible, but i still didn't even
finish the cnc :|

The page author really uses more prints glued for better opacity.
Professional transparencies are like old photo cameras negatives. Burned
with laser, and revealed and fixed and let dry.

Using emulsion as resist instead of the dry film I think will archive a
more successful rate with plated holes. The dry film can lift on small
ring holes, filling the hole can be a solution. So I look for it, only
know that link reporting success with the method. 

If you have the benzenophenone, and are willing to try this. I think we
all appreciate reports with soldermask also. Maybe only part A (resin)
epoxy glue. And i am curious about the acrylic resin mixture (never heat
it!).

I hope the automatic translation worked. The important part is:
For 3ml emulsion use 5 drops of sensiblizer. For 3 ml PVA glue use 2
drops, either both will do 15cm x 15cm board area minimum.
Where emulsion is the one from the silkscreen store.
And he refers to never use running water, just wetting the thing
carefully with water.

PS: My bad english and the automatic correction dependency, leaved the
word 'i' instead of 'he' in the previous email, for which i am sorry.
(among hood instead of wood)

Hi guys,  that's not a silk screen, it's a mask.

A silkscreen is a mesh cloth (silk) that is stretched across a frame. It's coated with a rubbery plastic goo. The plastic is exposed and developed like film and when finished, the bare silk screen is exposed where ever you wanted copper traces. The silkscreen is placed over a copper board and an ink is squeegeed over the whole thing. The silk screen is lifted off and the ink now covers the copper traces. The ink is allowed to dry and the silk screen is washed out. After the ink dries, the board is etched. 

We used to do this in high school back in the 70's and 80's. The Graphic Arts students with their dark room would make the silk screens for us electronics students. It's good for low production medium resolution boards (low resolution by todays standards - it can do DIPs and probably .050 SOIC's).

The emulsion itself could possibly be applied directly to a copper board but I don't see how this is different than just going with a wet photo process that is already known to work.

Me, I'll stick with the toner transfer. Thanks to this group I have that one down solid :-).

Phil - KA0HBG


--- In Homebrew_PCBs@yahoogroups.com, "aurangzebhaque" <aurangzebhaque@...> wrote:

>
> Simao,
> 
> Thanks for the excellent link. I am going to try it this weekend.
> 
> One comment. I have been making many many silkscreens using translucent tracing paper, with the design pattern printed out on common laser printer. I have never had the problem of opacity in the printout, and edges etc. have always been satisfactorily sharp. We use the sunlight here because it is abundant and free ;-), and the rays are parallel. Maybe you should try it too. Hopefully it will save you money on film.
> 
> And thanks everybody for your inputs.
> 
> Aurangzeb
>

Yes, strictly speaking that is correct.

However in the PCB industry "silkscreen" usually only means the component
legend print no matter if this is even done with silkscreen process or not.
Not very clear, but that's how it is for now.

ST

On Tue, Jun 23, 2009 at 6:43 PM, pgdion1 <pgdion1@...> wrote:

> Hi guys,  that's not a silk screen, it's a mask.
>
> A silkscreen is a mesh cloth (silk) that is stretched across a frame. It's
> coated with a rubbery plastic goo. The plastic is exposed and developed like
> film and when finished, the bare silk screen is exposed where ever you
> wanted copper traces. The silkscreen is placed over a copper board and an
> ink is squeegeed over the whole thing. The silk screen is lifted off and the
> ink now covers the copper traces. The ink is allowed to dry and the silk
> screen is washed out. After the ink dries, the board is etched.
>


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

Simao,
 
> If you have the benzenophenone, and are willing to try this. I think..


I have no problem with benzenophenone, except it may not be available and/or its cost.

The English translator works for me.

Sorry everybody. I assumed that since the group was about PCB making the difference between silk screen (the process) and component data (on top of the PCB) would need no elaboration. 

I guess the assumption turned out to be wrong. Another assumption ;-)

Aurangzeb