Homebrew PCBs

To learn about transparencies, temperatures, and techniques for Toner
Transfer, I took the time to run a series of tests with my hacked
laminator:

	http://www.delorie.com/pcb/transparencies/

24 different transfers, with comparisons and the original (big) scans
of the results.

Summary (if you don't want to look at all the pictures :)

* no matter how hot the laminator is, you need multiple passes

* there's a fine line between "stuck" and "squished"

* cleaning the board and keeping dust off everything is still critical
  (sigh)

* preheat the pcb

* don't put paper between the film and the rollers after the first
  pass.  You can probably make do without it for the first pass too,
  but it helps keep the film in place.  Tape would probably do if you
  need to accurately align the film.

* you *can* apply a second layer of toner if you need to, if you can
  align it sufficiently with the first.

* a mechanical bond is required; if the copper is too shiny the toner
  won't stick.

DJ great results reporting.  In the part

 

Theory: The unevenness of the copper due to the underlying FR4 was causing
uneven pressure and missed spots.

Test: The PCB was sanded to 2000 grit, resulting in a mirror-like surface.

Results: It's hard to see in the photos as the copper was reflects enough
light in the scanner that it appears dark, but there was very poor adhesion
of the toner! This was a very unexpected result - the toner needs a
mechanical bond to transfer. Scuff it!

 

Can you explain what you mean by scuff?  Are you referring to using the
green Scotch Brite pads?

 

Jeff

 

  _____  

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
On Behalf Of DJ Delorie
Sent: Sunday, November 20, 2011 3:34 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] Testing TT with Transparencies

 

  


To learn about transparencies, temperatures, and techniques for Toner
Transfer, I took the time to run a series of tests with my hacked
laminator:

http://www.delorie.com/pcb/transparencies/

24 different transfers, with comparisons and the original (big) scans
of the results.

Summary (if you don't want to look at all the pictures :)

* no matter how hot the laminator is, you need multiple passes

* there's a fine line between "stuck" and "squished"

* cleaning the board and keeping dust off everything is still critical
(sigh)

* preheat the pcb

* don't put paper between the film and the rollers after the first
pass. You can probably make do without it for the first pass too,
but it helps keep the film in place. Tape would probably do if you
need to accurately align the film.

* you *can* apply a second layer of toner if you need to, if you can
align it sufficiently with the first.

* a mechanical bond is required; if the copper is too shiny the toner
won't stick.





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

"Jeff Heiss" <jeff.heiss@...> writes:
> Can you explain what you mean by scuff?  Are you referring to using
> the green Scotch Brite pads?

Yes, I mean use some sort of abrasive to scratch up the surface enough
to provide mechanical grip.  Green scrubbies are the usual tool, but a
suitably coarse sandpaper grit (i.e. not 2000 ;) would do as well.

I just use a salt and vinegar mix on a 3M kitchen foam pad. Instant removal of oxide and a good surface to key onto.


Malcolm

 
I don't suffer from insanity I enjoy it!


________________________________

 From: DJ Delorie <dj@...>
To: Homebrew_PCBs@yahoogroups.com 
Sent: Sunday, November 20, 2011 5:30 PM
Subject: Re: [Homebrew_PCBs] Testing TT with Transparencies
 

  

"Jeff Heiss" <jeff.heiss@...> writes:
> Can you explain what you mean by scuff?  Are you referring to using
> the green Scotch Brite pads?

Yes, I mean use some sort of abrasive to scratch up the surface enough
to provide mechanical grip.  Green scrubbies are the usual tool, but a
suitably coarse sandpaper grit (i.e. not 2000 ;) would do as well.

 

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

DJ,

Have you tried different brand transparencies?

Before going back to photo etching >10 years ago
I used to do toner transfer from transparencies.

I started doing it in the early 90's after
reading about PARC doing TT in an EA magazine.

Anyway, I found that the transparency had a huge
effect on the transfer.

I got fantastic results with Faber-Castell
OH-LUX.  However these stopped being available
in oz, so I switched to the next best ones I
tried.  This was 3M Brand CG3300.

With the OH-LUX transfers, I would run cold water
over the top as it was still hot.  The totally
clear film would just crack off.  I never needed
to apply so much pressure to squish the traces.

The 3M was not as good and the extra heat/time
they needed would sometimes squish traces.

All the other brands I tried that where
available here either didn't take the toner
well from the printer, or never let go well to
the copper.

> DJ wrote:
> 
> To learn about transparencies, temperatures, and
> techniques for Toner Transfer, I took the time
> to run a series of tests with my hacked laminator
>
> <SNIP>

If you were looking for "further study" suggestions, I would try first sanding the FR4 to a mirror finish and then scuffing it up: the "weave" of the fibreglass def. affects pressure and therefore adhesion. (But, OTOH, you'd probably get very different thicknesses and therefore etch rates ...)

I know I'd like to see that.

PG

On 21/11/2011, at 4:30 AM, DJ Delorie wrote:

> 
> "Jeff Heiss" <jeff.heiss@...> writes:
> > Can you explain what you mean by scuff? Are you referring to using
> > the green Scotch Brite pads?
> 
> Yes, I mean use some sort of abrasive to scratch up the surface enough
> to provide mechanical grip. Green scrubbies are the usual tool, but a
> suitably coarse sandpaper grit (i.e. not 2000 ;) would do as well.
>

Piers Goodhew <piers@...> writes:

> If you were looking for "further study" suggestions, I would try first
> sanding the FR4 to a mirror finish and then scuffing it up: the
> "weave" of the fibreglass def. affects pressure and therefore
> adhesion. (But, OTOH, you'd probably get very different thicknesses
> and therefore etch rates ...)

Hmmm... I did the board I was running the tests for, so my incentive is
gone, but that's something to try.  Also: sanding with various grits to
see if there's a "sweet spot" in the coarse/fine continuum.

I also discovered that toner doesn't like to stick to the non-copper
side of a single-sided PCB :-P so I'll have to try sanding that side as
well.

> I know I'd like to see that.

So give it a try and see, I'm not the only one here who can do science :-)

"cunningfellow" <andrewm1973@...> writes:
> Have you tried different brand transparencies?

No, I just happened to have a big box of those sitting around from a
long time ago so I used them.  I was making a single-sided board and
wanted (1) a thick coat of toner on the etch side, and (2) tomer
"silkscreen" lined up on the component side.  If figured, the only way
to do the silkscreen side was toner, and transparencies would make it
easy.  Plus, I'm out of UV film at the moment, and the project had no
small traces, so TT was a viable option.  Figured I'd give it a try.

Based on the results, I think the key thing to realize is that toner
sticks due to a *mechanical* bond.  Transparencies are very smooth.  If
the PCB is less smooth, the toner will stick to it instead of the
transparency when you peel them apart.

Thus, vellum wouldn't work because it's got a matte finish on it.

> With the OH-LUX transfers, I would run cold water
> over the top as it was still hot.

I press the sandwich down on my table saw.  The cast iron sucks the heat
out in seconds, the pressure makes sure the toner is stuck to the pcb
when that happens.

DJ Delorie <dj@...> writes:
> I also discovered that toner doesn't like to stick to the non-copper
> side of a single-sided PCB :-P

Photo: http://www.delorie.com/pcb/transparencies/tt-on-fr4.html

Also: the board I made (partially populated) is shown here:
http://www.delorie.com/electronics/bldc/

Yes, that's just what happens.

I used double-sided board and just etched the spare copper away (the
surface that is left has a perfect micro-rough finish). Sanding never
did quite as well.

ST

On Mon, Nov 21, 2011 at 5:48 PM, DJ Delorie <dj@...> wrote:
>
> DJ Delorie <dj@...> writes:
>> I also discovered that toner doesn't like to stick to the non-copper
>> side of a single-sided PCB :-P
>
> Photo: http://www.delorie.com/pcb/transparencies/tt-on-fr4.html
>
> Also: the board I made (partially populated) is shown here:
> http://www.delorie.com/electronics/bldc/
>
>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
>

Stefan Trethan <stefan_trethan@...> writes:
> I used double-sided board and just etched the spare copper away (the
> surface that is left has a perfect micro-rough finish). Sanding never
> did quite as well.

I wonder if a coat of flat white spray paint (before
etching/trimming/etc so at least it's neat :) would give a suitable
surface to adhere toner too.  It would also provide a better background
for the image.

I don't understand.. wouldn't the entire paint layer resist the etch? I
have done etchings using a laser to selectively burn off a spray paint
layer, using the paint as the resist.

-David


On Mon, Nov 21, 2011 at 12:24 PM, DJ Delorie <dj@...> wrote:

> **
>
>
>
> Stefan Trethan <stefan_trethan@...> writes:
> > I used double-sided board and just etched the spare copper away (the
> > surface that is left has a perfect micro-rough finish). Sanding never
> > did quite as well.
>
> I wonder if a coat of flat white spray paint (before
> etching/trimming/etc so at least it's neat :) would give a suitable
> surface to adhere toner too. It would also provide a better background
> for the image.
>  
>


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

Could work....
I only put the clear paint on afterwards to make some boards look nice.

ST

On Mon, Nov 21, 2011 at 7:24 PM, DJ Delorie <dj@...m> wrote:
>
> Stefan Trethan <stefan_trethan@...> writes:
>> I used double-sided board and just etched the spare copper away (the
>> surface that is left has a perfect micro-rough finish). Sanding never
>> did quite as well.
>
> I wonder if a coat of flat white spray paint (before
> etching/trimming/etc so at least it's neat :) would give a suitable
> surface to adhere toner too.  It would also provide a better background
> for the image.
>
>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
>

David Mitchell <gossiphog@...> writes:
> I don't understand.. wouldn't the entire paint layer resist the etch?

I was talking about silkscreen on the non-copper side of a single-sided
board.