Homebrew PCBs

I am new to this group and I have been tinkering around with making 
hobby PC boards for a couple of years now (I am no pro nor do I claim 
to be).

I have tried several iron-on toner transfer systems and don't like 
them much.  The best system (using this method) that I have found is 
using the press-n-peel blue sheets and using a Dry-Mount Press (Older 
photographic item used to mount old style non-coated paper to matte 
board).

This method is the best I have tried so far....  However, I am 
considering attempting to use a sort of silk screen method to create 
PCB etch resists, but I am wondering if anyone knows of a cost 
effective ink or paint that can be used as etch resist.  I believe 
some sort of fabric ink may hold up using this method.

Does anyone know what material should be used for that green 
soldermask like what is found on commercial PCBs?  I am looking to 
make my projects a little more professional looking.

I appreciate any constructive criticism or help on this topic.


Thanks

From: "johnman9146" <johnman@...>

>I have tried several iron-on toner transfer systems and don't like

Im my opinion you're much better off using photoresist coated boards.

Print your layouts using the right transparent medium for your printer
(laser or inkjet) and use that to expose the board under UV. I made a
suitable lightbox with tubes sold as spare parts for the ready-made
unit sold by Maplin. I also use ready-prepared developer and etcher
from them and get a great result every time.

Cheers

Derryck

In a message dated 02-Apr-02 05:36:45 Central Standard Time, 
derryck@... writes:


> Print your layouts using the right transparent medium for your printer
> (laser or inkjet) and use that to expose the board under UV


But this assumes the PRINTER will make an exact "1:1" duplicate of the 
artwork you "draw" on the screen!  Without a special plotter DESIGNED for 
that, how can this really happen?  Just how accurate ARE these ink-jet 
printers?  I have a current HP 960c, and it is very fine doing photos in 
color, but I have NO clue if it can "draw" say, a grid, of equal squares.  I 
will have to tinker!         Hmmm...   Jan Rowland


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

--- JanRwl@... wrote:
> In a message dated 02-Apr-02 05:36:45 Central Standard Time, 
> derryck@... writes:
> 
> 
> > Print your layouts using the right transparent medium for your
> printer
> > (laser or inkjet) and use that to expose the board under UV
> 
> 
> But this assumes the PRINTER will make an exact "1:1" duplicate
> of the 
> artwork you "draw" on the screen!  Without a special plotter
> DESIGNED for 
> that, how can this really happen?  Just how accurate ARE these
> ink-jet 
> printers?

I used to use a Canon 610, it was not symmetrical and printed
slightly smaller than it was supposed to. Haven't tested my Canon
6000 to any high degree of precision, I seem to recall measuring an
8x10 print once and it was within a 1/16".

Back in the days when I used copy machines to make business cards
and photo layouts, I had to use one particular copy machine. At
102%, it would print out very close to 100%. I had it worked out to
blow up a PCB or business card pattern to a particular percentage,
then I'd clean it up, then shrink it down by a particular
percentage. By the math, it wouldn't work out, but because of the
copy machine it would work out.

Steve Greenfield

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When you print to a laser printer, the paper gets heated causing the paper
to expand. The moisture also gets driven out, which I believe causes the
paper to shrink. Net expansion probably depends on the relative humidity of
where you live. Depending on the grain of the paper, it will probably
expand/shrink more in one dimension than the other.

Running some pages through the printer immediately before prior to printing
on them will help. You may need to print something along the edges to get
the wire to heat up.

You can really see this effect on duplexing laser printers, where the first
side imaged has a sometimes dramatically different size (up to 1/8") than
the second side imaged.

I believe that with transparencies, the expansion is more uniform. Because
the media is expanded while being printed, it causes your image to shrink
once the media cools down.

With ink jet printers, you're adding moisture to the page, which causes it
to expand. Here, the amount of ink makes a difference (more ink = more
expansion). The grain of the paper will cause different amounts of expansion
in either dimension. Things should shrink back up a bit once the ink is
completely dried.

I wouldn't expect transparencies to be affected on an ink-jet (except for
heating effects, which should be much less than a laser printer).

Dave Hylands

> -----Original Message-----
> From: Steve Greenfield [mailto:alienrelics@...]
> Sent: Tuesday, April 02, 2002 12:54 PM
> To: Homebrew_PCBs@yahoogroups.com
> Subject: Re: [Homebrew_PCBs] Printing PCB boards
> 
> 
> --- JanRwl@... wrote:
> > In a message dated 02-Apr-02 05:36:45 Central Standard Time, 
> > derryck@... writes:
> > 
> > 
> > > Print your layouts using the right transparent medium for your
> > printer
> > > (laser or inkjet) and use that to expose the board under UV
> > 
> > 
> > But this assumes the PRINTER will make an exact "1:1" duplicate
> > of the 
> > artwork you "draw" on the screen!  Without a special plotter
> > DESIGNED for 
> > that, how can this really happen?  Just how accurate ARE these
> > ink-jet 
> > printers?
> 
> I used to use a Canon 610, it was not symmetrical and printed
> slightly smaller than it was supposed to. Haven't tested my Canon
> 6000 to any high degree of precision, I seem to recall measuring an
> 8x10 print once and it was within a 1/16".
> 
> Back in the days when I used copy machines to make business cards
> and photo layouts, I had to use one particular copy machine. At
> 102%, it would print out very close to 100%. I had it worked out to
> blow up a PCB or business card pattern to a particular percentage,
> then I'd clean it up, then shrink it down by a particular
> percentage. By the math, it wouldn't work out, but because of the
> copy machine it would work out.
> 
> Steve Greenfield

In general inkjet printers give far superior dimensional stability than laser
printers. The repeatability and accuracy across an A4 page is under 0.1mm on my
Epson 660 (i.e. better than what my eyes can see aligned up against a ruler).
This is on transparency, where water absorption in the polyester film is nil.

>
> With ink jet printers, you're adding moisture to the page, which causes it
> to expand. Here, the amount of ink makes a difference (more ink = more
> expansion). The grain of the paper will cause different amounts of expansion
> in either dimension. Things should shrink back up a bit once the ink is
> completely dried.
>
> I wouldn't expect transparencies to be affected on an ink-jet (except for
> heating effects, which should be much less than a laser printer).
>
> Dave Hylands
>

JanRwl@... wrote:
> 
> In a message dated 02-Apr-02 05:36:45 Central Standard Time,
> derryck@... writes:
> 
> > Print your layouts using the right transparent medium for your printer
> > (laser or inkjet) and use that to expose the board under UV
> 
> But this assumes the PRINTER will make an exact "1:1" duplicate of the
> artwork you "draw" on the screen!  Without a special plotter DESIGNED for
> that, how can this really happen?  Just how accurate ARE these ink-jet
> printers?  I have a current HP 960c, and it is very fine doing photos in
> color, but I have NO clue if it can "draw" say, a grid, of equal squares.  I
> will have to tinker!         Hmmm...   Jan Rowland

I use an epson stylus 400 colour inkjet and genuine epson transparency.
It's easy to do 8mil tracks/spacing, and there's no dimensional problems.
There's usually a printer option to scale the printout if you need to.

That kind of misses the point.  I am looking to see if anyone knows 
of a suitable etch resist ink, and/or a suitable soldermask ink.

If I do decide to go your way and do the transparancy method with UV 
sensitive photoresist, I have a few questions.

How do I know when I have the proper exposure?

Can you over-expose?  

How dark black does the transparancy need to be for this method to be 
effective?

I have access to some pretty sophisticated hardware if I do decide to 
try this method.  Items such as a photoplotter, a vacuum backed UV 
table (for exposing printing plates) and more, but it is a hassle to 
go there for all the neat toys.

I don't think there would be any issues with the image size not being 
exactly 100% as it is a professional photoplotter designed to make 
printing plates for magazine reproduction.

Potentially, I may just have to experiment with different inks if 
nobody has any suggestions.  

Does anyone print legends on thier prototype boards?  

Does anyone use anything to add a soldermask?  

Does anyone even use any type of conformal coating?



> Im my opinion you're much better off using photoresist coated 
boards.
> 
> Print your layouts using the right transparent medium for your 
printer
> (laser or inkjet) and use that to expose the board under UV. I made 
a

> suitable lightbox with tubes sold as spare parts for the ready-made
> unit sold by Maplin. I also use ready-prepared developer and etcher
> from them and get a great result every time.
> 
> Cheers
> 
> Derryck

There's good printers and crappy printers. Crappy: lasers, many
inkjets. Good: epson stylus colour. I did various comparisons.
The main thing with the epson ones is that the genuine epson
inkjet transparency has a smooth absorbant layer, and the
printout is also smooth.

To test for exposure, expose segments of a pcb in 30s increments,
then develop. Make your exposure time a couple of minutes longer
than the minimum. Crappy printouts are easily over-exposed. With
an epson printout, i expose for 5mins using a small light-box with
4 tubes, but if i forget and expose it for half an hour, i still
get an excellent result (just some tracks get slightly thinner).

johnman9146 wrote:
> 
> That kind of misses the point.  I am looking to see if anyone knows
> of a suitable etch resist ink, and/or a suitable soldermask ink.
> 
> If I do decide to go your way and do the transparancy method with UV
> sensitive photoresist, I have a few questions.
> 
> How do I know when I have the proper exposure?
> 
> Can you over-expose?
> 
> How dark black does the transparancy need to be for this method to be
> effective?
> 
> I have access to some pretty sophisticated hardware if I do decide to
> try this method.  Items such as a photoplotter, a vacuum backed UV
> table (for exposing printing plates) and more, but it is a hassle to
> go there for all the neat toys.
> 
> I don't think there would be any issues with the image size not being
> exactly 100% as it is a professional photoplotter designed to make
> printing plates for magazine reproduction.
> 
> Potentially, I may just have to experiment with different inks if
> nobody has any suggestions.
> 
> Does anyone print legends on thier prototype boards?

Some labels on the top copper.

> Does anyone use anything to add a soldermask?
> 
> Does anyone even use any type of conformal coating?

Sometimes, for water-proofing.

> > Im my opinion you're much better off using photoresist coated
> boards.
> >
> > Print your layouts using the right transparent medium for your
> printer
> > (laser or inkjet) and use that to expose the board under UV. I made
> a
> > suitable lightbox with tubes sold as spare parts for the ready-made
> > unit sold by Maplin. I also use ready-prepared developer and etcher
> > from them and get a great result every time.
> >
> > Cheers
> >
> > Derryck

From: JanRwl@...

>> Print your layouts using the right transparent medium for your printer
>> (laser or inkjet) and use that to expose the board under UV
>
>
>But this assumes the PRINTER will make an exact "1:1" duplicate of the
>artwork you "draw" on the screen!  Without a special plotter DESIGNED for
>that, how can this really happen?  Just how accurate ARE these ink-jet

All I can say is that I've never had a problem with the Kyocera laser printer
I use, even SMD fingers seem to come out properly. Suck it and see is the
best way to be sure of course!

Cheers

Derryck

johnman9146 wrote:

>That kind of misses the point.  I am looking to see if anyone knows 
>of a suitable etch resist ink, and/or a suitable soldermask ink.
>
>If I do decide to go your way and do the transparancy method with UV 
>sensitive photoresist, I have a few questions.
>
>How do I know when I have the proper exposure?
>
>Can you over-expose?  
>
>How dark black does the transparancy need to be for this method to be 
>effective?
>
>I have access to some pretty sophisticated hardware if I do decide to 
>try this method.  Items such as a photoplotter, a vacuum backed UV 
>table (for exposing printing plates) and more, but it is a hassle to 
>go there for all the neat toys.
>
>I don't think there would be any issues with the image size not being 
>exactly 100% as it is a professional photoplotter designed to make 
>printing plates for magazine reproduction.
>
>Potentially, I may just have to experiment with different inks if 
>nobody has any suggestions.  
>
>Does anyone print legends on thier prototype boards?  
>
>Does anyone use anything to add a soldermask?  
>
>Does anyone even use any type of conformal coating?
>

How much knowledge to you have on ink formulations ? Its an entire field 
of expertise. Inkjet ink chemists are specialized people. You want to 
develop your own inkjet ink that gives high image quality AND can also 
forms a stable acid etch resist ? !  My best bet would search 
http://www.uspto.gov and see if anyone else has done it.  

The reason why everyone uses photoresists is because it works the best. 
 The phototool  is important, and I've only ever seen good ones from an 
inkjet./transparency, I've also seen many more bad ones from various 
inkjets and inkjet transparencies. Its important that the ink and 
transparency are compatible with each other, otherwise you get pin 
holes, banding and rough edges. The Epson stylus series do very good job 
with their dye based black inks on their transparency. Only problem they 
are expensive. I suspect Epson have patented their transparency because 
no one else make one the same. You can print on it then dunk it in water 
and nothing happens to the ink. There are other transparencies that work 
well with the Epson black ink. The HP inkjets use a pigment black and do 
not go so well on Epson transparencies. Use HP transparencies with HP 
ink, the results are quite ok.

There was a company in West Hartford CT which was pioneering a piezo 
ink-jet head with extremely fine "resolution" -- Accent Color 
Sciences (now bankrupt).  There were a couple patents filed by them 
in 1999 and 2000 which describe the remarkable resolution of the 
print head.  Look under assignee name (AN/Accent) field in the 
advanced search engine at the www.uspto.gov   While there was a lot 
of interest from some of the cell phone manufactures, (if you wanted, 
you could change circuitry on the fly) the economy took its toll.

> How much knowledge to you have on ink formulations ? Its an entire 
field 
> of expertise. Inkjet ink chemists are specialized people. You want 
to 
> develop your own inkjet ink that gives high image quality AND can 
also 
> forms a stable acid etch resist ? !  My best bet would search 
> http://www.uspto.gov and see if anyone else has done it.  
> 
> The reason why everyone uses photoresists is because it works the 
best. 
>  The phototool  is important, and I've only ever seen good ones 
from an 
> inkjet./transparency, I've also seen many more bad ones from 
various 
> inkjets and inkjet transparencies. Its important that the ink and 
> transparency are compatible with each other, otherwise you get pin 
> holes, banding and rough edges. The Epson stylus series do very 
good job 
> with their dye based black inks on their transparency. Only problem 
they 
> are expensive. I suspect Epson have patented their transparency 
because 
> no one else make one the same. You can print on it then dunk it in 
water 
> and nothing happens to the ink. There are other transparencies that 
work 
> well with the Epson black ink. The HP inkjets use a pigment black 
and do 
> not go so well on Epson transparencies. Use HP transparencies with 
HP 
> ink, the results are quite ok.



I'm not looking for ink for an ink-jet, I am looking for ink that one 
would use for silk-screen type printing.

Ink for printing with an ink-jet print head would be very thin.  I am 
looking for a nice thick almost paint like ink that is acid (etch) 
resistant.

I have been reading more and more about a certain kind of etch resist 
pen that uses a laquer based ink.  Perhaps I will try some type of 
laquer paint/ink.

I am also considering the photoresist method as it sounds like this 
is the method of choice here.

I will start a new thread.

--- johnman9146 <johnman@...> wrote:

> I have been reading more and more about a certain kind of etch
> resist 
> pen that uses a laquer based ink.  Perhaps I will try some type
> of 
> laquer paint/ink.
> 
> I am also considering the photoresist method as it sounds like
> this 
> is the method of choice here.

Please check out the bookmarks section. I went to a lot of trouble
to organize it. There are links there for all kinds of methods, and
as far as etch resist pens there are pens -much- better than those
lame laundry marking pens that are sold as etch resist pens.

Steve, moderator feeling unappreciated


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At 05:49 AM 4/4/02 +0000, johnman9146 wrote:

>I'm not looking for ink for an ink-jet, I am looking for ink that one
>would use for silk-screen type printing.

The stuff we used to use was called "Circuit Black" but I don't remember 
the manufacturer's name.  Check your local Silk Screen supply house - they 
should be able to search that name for you.

If I get a chance tomorrow, I call around and see what I can find out.

dwayne


Dwayne Reid   <dwayner@...>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

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