Homebrew PCBs

Hello,

   I just bought some release paper and green foil from pulsarprofx.com.  Well, actually from Digikey, but it's the same stuff.  In his instrux, the guy specifically warns against the use of Brother printers.  It's not the first time I've heard this.  He says that Brother uses a unique high-temperature toner that just will not fuse to circuit boards.  

   I have a Brother 8860DN multifunction printer.  It's a fairly new, high-end machine.  Does 1200DPI, duplex, etc etc.  Importantly for our stuff, it does mirror-imaging.

   I've done several double-sided boards with the Brother.  I've gotten traces to work as small as 15-mil.  

   On the latest board, it didn't quite make it - this was a surface mount board with a 64-pin QFP, requiring lots of 10-mil traces.  Four of them broke while I was ever-so-gently scrubbing the paper off.

   But that's not the sort of failure I read about with the Brothers: I read about wholesale failure of toner to transfer at all, which is definitely not the case here.  I wonder if Brother "saw the light" and made their toner a bit milder WRT temperature?

   Digging through the web, I found this pulsarprofx guy who says that his paper "just floats off", and his foil will stop etchant from going through the toner.   Sounds good to me.  I'll be trying it tomorrow.  With the Brother.

   The paper is fairly pricy, at $14 for 10 sheets.  On the web site, he says it's covered with "dextrin", which as far as I can tell, is starch.  Wonder if one could make paper like that by spraying the ordinary stuff with starch solution?  I can probably stretch this stuff to where it's not an issue by cutting small pieces for my board printouts.

   If the Brother won't play, I also have an HP 1020, which I keep loaded with MICR toner for printing checks.  But I still have the original cartridge somewhere, with all of one sheet printed on it.
The HP only does 600DPI, and something they call "FAS1200".  I guess that's short for "Fake 1200" :).  And the driver doesn't do mirror printing.  It's the original driver from when I bought the printer - at least four years ago.  I see there's a newer driver dated 2007.  Anybody know if that one does mirror print?

                                  - Jerry Kaidor

On Tue, 10 Mar 2009 05:15:07 -0000, you wrote:

>Hello,
>
>   I just bought some release paper and green foil from pulsarprofx.com.  Well, actually from Digikey, but it's the same stuff.  In his instrux, the guy specifically warns against the use of Brother printers.  It's not the first time I've heard this.  He says that Brother uses a unique high-temperature toner that just will not fuse to circuit boards.  

Check to see if mouser has it cheaper.  I use an HP, not sure that the
color toner is not higher temperature.  No brother, though....
>
>   I have a Brother 8860DN multifunction printer.  It's a fairly new, high-end machine.  Does 1200DPI, duplex, etc etc.  Importantly for our stuff, it does mirror-imaging.
>
>   I've done several double-sided boards with the Brother.  I've gotten traces to work as small as 15-mil.  
>
>   On the latest board, it didn't quite make it - this was a surface mount board with a 64-pin QFP, requiring lots of 10-mil traces.  Four of them broke while I was ever-so-gently scrubbing the paper off.
>

QFP with 0.5 mm spacing?  interesting.

>   But that's not the sort of failure I read about with the Brothers: I read about wholesale failure of toner to transfer at all, which is definitely not the case here.  I wonder if Brother "saw the light" and made their toner a bit milder WRT temperature?

No idea.
>
>   Digging through the web, I found this pulsarprofx guy who says that his paper "just floats off", and his foil will stop etchant from going through the toner.   Sounds good to me.  I'll be trying it tomorrow.  With the Brother.
>

Well, he's mostly right.  If you read the instructions, they recommend
a laminator, 0.032 board, their products, etc....

the paper *does* just float off.  If you allow it to cool completely,
then it may pop off on its own.  I don't know if it leaves the toner
on the paper or behind.  I try to reheat it and go from there.  

Oddly enough, the one board that I printed on the backside of the
paper (by accident) did not do badly at all.

>   The paper is fairly pricy, at $14 for 10 sheets.  On the web site, he says it's covered with "dextrin", which as far as I can tell, is starch.  Wonder if one could make paper like that by spraying the ordinary stuff with starch solution?  I can probably stretch this stuff to where it's not an issue by cutting small pieces for my board printouts.

make sure that it fits the laser printer, and that your laser printer
does not do stupid things to make the drawing fit.

>
>   If the Brother won't play, I also have an HP 1020, which I keep loaded with MICR toner for printing checks.  But I still have the original cartridge somewhere, with all of one sheet printed on it.
>The HP only does 600DPI, and something they call "FAS1200".  I guess that's short for "Fake 1200" :).  And the driver doesn't do mirror printing.  It's the original driver from when I bought the printer - at least four years ago.  I see there's a newer driver dated 2007.  Anybody know if that one does mirror print?

Nope, I use Eagle (pause for boos and hisses) and that has a mirror
print capability.  For DS boards, I recommend feeding the sheet in the
same way each time and varying the position of the printout on the
paper.  Highest toner density is recommended as well.

Harvey

>
>                                  - Jerry Kaidor
>

Hello Jerry - it's been several days since your post and I'm VERY interested in how the Brother worked with the release paper and green foil from Pulsarprofx.com.  I also have the Brother 2140 laser printer and have used with it some success on TT.  

I use a toaster oven set at 450F for about 10 minutes to be sure it's headed thru my aluminum clamp assembly.  I had read on the Pulsarprofx the Brother would not wrok at all because it uses a hotter type toner.  Are you using the OEM toner? 

I'm a newbie here and am reading and learning.

Thanks to all for input.

ken H> K9FV

--- In Homebrew_PCBs@yahoogroups.com, "jerrytr2.com" <jerry@...> wrote:

>
> Hello,
> 
>    I just bought some release paper and green foil from pulsarprofx.com.  Well, actually from Digikey, but it's the same stuff.  In his instrux, the guy specifically warns against the use of Brother printers.  It's not the first time I've heard this.  He says that Brother uses a unique high-temperature toner that just will not fuse to circuit boards.  
> 
>    I have a Brother 8860DN multifunction printer.  It's a fairly new, high-end machine.  Does 1200DPI, duplex, etc etc.  Importantly for our stuff, it does mirror-imaging.
> 
>    I've done several double-sided boards with the Brother.  I've gotten traces to work as small as 15-mil.  
> 
>    On the latest board, it didn't quite make it - this was a surface mount board with a 64-pin QFP, requiring lots of 10-mil traces.  Four of them broke while I was ever-so-gently scrubbing the paper off.
> 
>    But that's not the sort of failure I read about with the Brothers: I read about wholesale failure of toner to transfer at all, which is definitely not the case here.  I wonder if Brother "saw the light" and made their toner a bit milder WRT temperature?
> 
>    Digging through the web, I found this pulsarprofx guy who says that his paper "just floats off", and his foil will stop etchant from going through the toner.   Sounds good to me.  I'll be trying it tomorrow.  With the Brother.
> 
>    The paper is fairly pricy, at $14 for 10 sheets.  On the web site, he says it's covered with "dextrin", which as far as I can tell, is starch.  Wonder if one could make paper like that by spraying the ordinary stuff with starch solution?  I can probably stretch this stuff to where it's not an issue by cutting small pieces for my board printouts.
> 
>    If the Brother won't play, I also have an HP 1020, which I keep loaded with MICR toner for printing checks.  But I still have the original cartridge somewhere, with all of one sheet printed on it.
> The HP only does 600DPI, and something they call "FAS1200".  I guess that's short for "Fake 1200" :).  And the driver doesn't do mirror printing.  It's the original driver from when I bought the printer - at least four years ago.  I see there's a newer driver dated 2007.  Anybody know if that one does mirror print?
> 
>                                   - Jerry Kaidor
>

Hi Jerry,
Papermaking requires multimillion dollar equipment, well beyond the scope of
the homebrew pcb vendors.

Pulsar has carved out a very nice niche by repackaging and reselling some
very standard industrial materials. Some people have  success with their
products while other people find them overpriced and worthless. There are
just too many factors in toner transfer for anything to be 100% reliable.

For example, the "green' film is a standard heat transfer foil. You have
probably seen the gold version used to hot stamp stamp jewelry boxes. If you
remember the early days of laser printers, before inkjets came out, you
could buy (and still can buy) "laser foil" to add metallic colors to
certificate.

Dextrin is a very cheap starch used in papermaking as a "sizing / coating
on paper to bind it together and make the surface smoother.

There is nothing "magic" in these products. Other than the "magic" of
marketing and making a profit.

You'll need to try a few different papers and techniques and find one that
works for you under yor conditions.

Myc



On Thu, Mar 19, 2009 at 2:45 PM, Ken H> <sailingto@...> wrote:

>   Hello Jerry - it's been several days since your post and I'm VERY
> interested in how the Brother worked with the release paper and green foil
> from Pulsarprofx.com. I also have the Brother 2140 laser printer and have
> used with it some success on TT.
>
> I use a toaster oven set at 450F for about 10 minutes to be sure it's
> headed thru my aluminum clamp assembly. I had read on the Pulsarprofx the
> Brother would not wrok at all because it uses a hotter type toner. Are you
> using the OEM toner?
>
> I'm a newbie here and am reading and learning.
>
> Thanks to all for input.
>
> ken H> K9FV
>
> --- In Homebrew_PCBs@yahoogroups.com <Homebrew_PCBs%40yahoogroups.com>, "
> jerrytr2.com" <jerry@...> wrote:
> >
> > Hello,
> >
> > I just bought some release paper and green foil from pulsarprofx.com.
> Well, actually from Digikey, but it's the same stuff. In his instrux, the
> guy specifically warns against the use of Brother printers. It's not the
> first time I've heard this. He says that Brother uses a unique
> high-temperature toner that just will not fuse to circuit boards.
> >
> > I have a Brother 8860DN multifunction printer. It's a fairly new,
> high-end machine. Does 1200DPI, duplex, etc etc. Importantly for our stuff,
> it does mirror-imaging.
> >
> > I've done several double-sided boards with the Brother. I've gotten
> traces to work as small as 15-mil.
> >
> > On the latest board, it didn't quite make it - this was a surface mount
> board with a 64-pin QFP, requiring lots of 10-mil traces. Four of them broke
> while I was ever-so-gently scrubbing the paper off.
> >
> > But that's not the sort of failure I read about with the Brothers: I read
> about wholesale failure of toner to transfer at all, which is definitely not
> the case here. I wonder if Brother "saw the light" and made their toner a
> bit milder WRT temperature?
> >
> > Digging through the web, I found this pulsarprofx guy who says that his
> paper "just floats off", and his foil will stop etchant from going through
> the toner. Sounds good to me. I'll be trying it tomorrow. With the Brother.
> >
> > The paper is fairly pricy, at $14 for 10 sheets. On the web site, he says
> it's covered with "dextrin", which as far as I can tell, is starch. Wonder
> if one could make paper like that by spraying the ordinary stuff with starch
> solution? I can probably stretch this stuff to where it's not an issue by
> cutting small pieces for my board printouts.
> >
> > If the Brother won't play, I also have an HP 1020, which I keep loaded
> with MICR toner for printing checks. But I still have the original cartridge
> somewhere, with all of one sheet printed on it.
> > The HP only does 600DPI, and something they call "FAS1200". I guess
> that's short for "Fake 1200" :). And the driver doesn't do mirror printing.
> It's the original driver from when I bought the printer - at least four
> years ago. I see there's a newer driver dated 2007. Anybody know if that one
> does mirror print?
> >
> > - Jerry Kaidor
> >
>
>  
>


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

> For example, the "green' film is a standard heat transfer foil. You >have probably seen the gold version used to hot stamp stamp jewelry >boxes. If you remember the early days of laser printers, before >inkjets came out, you could buy (and still can buy) "laser foil" to > add metallic colors to certificate.
> 

This is very interesting information. I have been looking at the Pulsar product. I am new to toner transfer but find it very interesting. Anyway, once you said laser foil I found the following link which has product at least 1/3 the price of Pulsar. 

http://www.craftycomputerpaper.co.uk/products-Laser-Transfer-Foils_LASFOILPROD.htm


> Dextrin is a very cheap starch used in papermaking as a "sizing / ? > coating on paper to bind it together and make the surface smoother.

Then this on Dextrin. 

http://forums.makezine.com/comments.php?DiscussionID=1825

What a difference a few key words make. I did not know a lot about the materials used. I also assumed that maybe they had put a lot Pulsar had maybe put a lot of effort into perfecting the technique. If their product are just rebadged well good for them. But if you are saying they are doing nothing special then it seems a little cynical of them really. I wonder if they read this and might have a comment to make on the subject?

Great information though, thanks

Trev

Trev,
I wouldn't call Pulsar cynical. They just found a way to make a profit in a
niche market. That's just good business practice.

The key is to be a smart consumer.

Myc


On Fri, Mar 20, 2009 at 8:33 AM, trevwhite74 <trevor.white100@...
> wrote:

>
> > For example, the "green' film is a standard heat transfer foil. You >have
> probably seen the gold version used to hot stamp stamp jewelry >boxes. If
> you remember the early days of laser printers, before >inkjets came out, you
> could buy (and still can buy) "laser foil" to > add metallic colors to
> certificate.
> >
>
> This is very interesting information. I have been looking at the Pulsar
> product. I am new to toner transfer but find it very interesting. Anyway,
> once you said laser foil I found the following link which has product at
> least 1/3 the price of Pulsar.
>
>
> http://www.craftycomputerpaper.co.uk/products-Laser-Transfer-Foils_LASFOILPROD.htm
>
> > Dextrin is a very cheap starch used in papermaking as a "sizing / ? >
> coating on paper to bind it together and make the surface smoother.
>
> Then this on Dextrin.
>
> http://forums.makezine.com/comments.php?DiscussionID=1825
>
> What a difference a few key words make. I did not know a lot about the
> materials used. I also assumed that maybe they had put a lot Pulsar had
> maybe put a lot of effort into perfecting the technique. If their product
> are just rebadged well good for them. But if you are saying they are doing
> nothing special then it seems a little cynical of them really. I wonder if
> they read this and might have a comment to make on the subject?
>
> Great information though, thanks
>
> Trev
>
>  
>


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

>
> Trev,
> I wouldn't call Pulsar cynical. They just found a way to make a profit in a
> niche market. That's just good business practice.
> 
> The key is to be a smart consumer.
> 
> Myc
> 

No, I do not think I really explained what I meant properly. I would not think they are cynical to be honest. Looking at the web site there is lots of great information and hints and tips. It just did not seem to match the idea that the materials are not that special. It sounded like they really had come up with a good idea. Just the previous mention of over priced material was something that made me wonder. 

Trev

--- In Homebrew_PCBs@yahoogroups.com, "trevwhite74" <trevor.white100@...> wrote:
>
> >
> > Trev,
> > I wouldn't call Pulsar cynical. They just found a way to make a profit in a
> > niche market. That's just good business practice.
> > 
> > The key is to be a smart consumer.
> > 
> > Myc
> > 
> 
> No, I do not think I really explained what I meant properly. I would not think they are cynical to be honest. Looking at the web site there is lots of great information and hints and tips. It just did not seem to match the idea that the materials are not that special. It sounded like they really had come up with a good idea. Just the previous mention of over priced material was something that made me wonder. 
> 
> Trev

I would not expect them to give up the horse. That is smart marketing. I wish I could have at just a little of that marketing sense in me, maybe I'd have made some money instead of giving away all my good ideas...

Steve Greenfield

Just a note about today's task.  I scrounged some tubing and made some
adapters, got some scrap rubber gasket material, and converted my UV
exposure box to vacuum hold-down.  I used a 1/4" wide strip of rubber
sticky-backed gasket material around the edge, drilled a hole in from
the front and up into the space within the gasket, and made a wooden
adapter (stopper) to connect the shop-vac to the tubing.

I didn't feel much "suck" on the end of the tube with my finger, but
the first time I hooked it up and tested it I saw the glass bow in so
much I feared it would break!  I just need to find out if I can run
the shop vac with low air flow for the 5.5 minutes it takes to do an
exposure.

What I decided to do is keep a stack of card stock (half-sheets) to
prop up the board to keep it just a little below the height of the
1/8" gaskets, so that the glass doesn't bend that much, but not so
much that the film isn't held tightly to the board.  I'll have to run
some tests with a dial indicator.

I can't find my vacuum gauge, though.  I was thinking of making a new
adapter that allowed some air to flow through to the vacuum to keep it
from overheating, but without knowing how much vacuum it's drawing I
have no way of knowing how much extra flow I can afford.  Anyone else
have any idea how much vacuum is needed to hold the film down, or
other tips?

Now that I have a temperature controlled laminator to put films on (it
wants 240F, not the 320F the laminator used to do) and a vacuum to
hold them down, maybe tomorrow I'll try making some spirals too :-)

DJ Delorie  wrote:

> 
> I didn't feel much "suck" on the end of the tube with my finger, but
> the first time I hooked it up and tested it I saw the glass bow in so
> much I feared it would break!  I just need to find out if I can run
> the shop vac with low air flow for the 5.5 minutes it takes to do an
> exposure.
> 
>

Sounds like you need a calibrated hole :)

Just like a domestic vacuum cleaner, have a hole in the vacuum pipe to reduce the effective vacuum.

Warren

LOL you are not supposed to suck the glass down!
The vacuum exposure units I have seen use a flexible clear plastic
cover (like clear plastic tablecloth) to hold down the films.

Usually it's like this (top to bottom):

upper part (hinged)
{lid
 UV tubes
 glass
}

Vacuum cover
{thin frame with plastic film, hinged separately.
}

lower part (fixed)
{glass with hole in corner for vacuum
 UV tubes
 bottom of case
}

You slap on the film stack, flip down the vacuum cover, engage the
vacuum, check alignment, flip down the top part with the upper
exposure tubes, and start the timer.

For a vacuum pump you can use an old fridge compressor (get it at the
recycling place already disconnected). It has very decent vacuum. A
diaphragm pump (fish tank) would likely also suffice.

ST

On Sun, Mar 22, 2009 at 3:44 AM, DJ Delorie <dj@...> wrote:
>
> Just a note about today's task.  I scrounged some tubing and made some
> adapters, got some scrap rubber gasket material, and converted my UV
> exposure box to vacuum hold-down.  I used a 1/4" wide strip of rubber
> sticky-backed gasket material around the edge, drilled a hole in from
> the front and up into the space within the gasket, and made a wooden
> adapter (stopper) to connect the shop-vac to the tubing.
>
> I didn't feel much "suck" on the end of the tube with my finger, but
> the first time I hooked it up and tested it I saw the glass bow in so
> much I feared it would break!  I just need to find out if I can run
> the shop vac with low air flow for the 5.5 minutes it takes to do an
> exposure.
>
> What I decided to do is keep a stack of card stock (half-sheets) to
> prop up the board to keep it just a little below the height of the
> 1/8" gaskets, so that the glass doesn't bend that much, but not so
> much that the film isn't held tightly to the board.  I'll have to run
> some tests with a dial indicator.
>
> I can't find my vacuum gauge, though.  I was thinking of making a new
> adapter that allowed some air to flow through to the vacuum to keep it
> from overheating, but without knowing how much vacuum it's drawing I
> have no way of knowing how much extra flow I can afford.  Anyone else
> have any idea how much vacuum is needed to hold the film down, or
> other tips?
>
> Now that I have a temperature controlled laminator to put films on (it
> wants 240F, not the 320F the laminator used to do) and a vacuum to
> hold them down, maybe tomorrow I'll try making some spirals too :-)
>
>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
>

At 09:44 PM 3/21/2009, DJ Delorie wrote:
>  converted my UV exposure box to vacuum hold-down.. . . the glass bow in so
>much I feared it would break!

i've built several vac hold downs over the years and the trick is to 
have the substrate supported everywhere. one way i did this was to 
take a piece of good quality flat plywood and cut parallel groves 
with a table saw in both directions about 1/8 inch deep on one side 
across the entire face of the board. (say, 1/2" apart) spray it with 
acrylic or some other sealer to seal the wood, drill a 3/4" or 
whatever size hole you need to connect to the vacuum line in the 
center of the board and then glue a piece of Formica on the top of 
the grooved side carefully so's not to get glue in the grooves (i 
used contact cement on a 2 ft x 3 ft table that lasted over 20 years 
for screen printing). now you can see from the edges where the 
grooves are and draw pencil lines across the formica and use these 
guides to drill 1/16" holes across the entire surface over the 
grooves beneath. now tape up the edges to seal the ends of the 
grooves and attach the vac hose (maybe with a 90 degree connector). 
you will have to put wooden feet on the bottom so the hose can exit 
from beneath and keep the board sitting level. now whatever size 
board you place on the top, just tape around it's edge to seal off 
the uncovered vac holes and any size board can be accommodated. if 
you want to expose negs to photoresist, you can also place a piece of 
flexible clear plastic over the top of the board/litho neg sandwich 
that covers the entire hold-down surface and get perfect contact for 
exposures. i used to use sunlight to expose and place a toy dart 
stuck on the top edge of the board to orient to the sun. when you 
move the board so that the shadow of the darts shaft disappears, the 
board is exactly perpendicular to the sun's rays. i now have access 
to some free corian and will build one from that which has a 
perfectly flat and smooth surface.


William Alford

GI Motility Medical Research Page
http://alford.grimtrojan.com/ 

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

William Alford <walford@...> writes:
> I've built several vac hold downs over the years and the trick is to 
> have the substrate supported everywhere.

Maybe I missed a bit of info...  the first time I tested it, I had
nothing in it - just the glass panel with the gasket around the edges.
I guessed that the panel would be pulled down evenly, and I could
measure how far.  What happened, obvious in retrospect, is that the
glass bowed down further in the middle.  My solution, obviously, is to
use the pcb to support the middle of the glass.  The trick will be to
support it enough but not too much - I want the glass flat on the
board at full pressure, not bowed down due to insufficient support or
arched over due to too much.

The gasket is 125 mil, the boards range from 8 to 65 mil, each sheet
of card stock is 8 mil, the film is a few mil, etc.  So I can stack it
all up so that the glass is pulled down evenly over everything.

"warrenbrayshaw" <warrenbrayshaw@...> writes:
> Sounds like you need a calibrated hole :)

That's why I was looking for my vacuum gauge :)

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
> 
> Just a note about today's task.  I scrounged some tubing and made some
> adapters, got some scrap rubber gasket material, and converted my UV
> exposure box to vacuum hold-down.  I used a 1/4" wide strip of rubber
> sticky-backed gasket material around the edge, drilled a hole in from
> the front and up into the space within the gasket, and made a wooden
> adapter (stopper) to connect the shop-vac to the tubing.
> 
> I didn't feel much "suck" on the end of the tube with my finger, but
> the first time I hooked it up and tested it I saw the glass bow in so
> much I feared it would break!  

You don't say how big the tube was, but if you can stopper it with a finger then it is probably 3/8 or 1/4 inch ID. Well, 5 psi of pull would translate to about 2 pounds pull on your fingertip. Put that on a 10x8 sheet of glass and it is the equivalent of placing 400 pounds on the glass!

I'd make an adjustable hole in the shopvac hose or in the vacuum table. It is bad for the shopvac to run without any air input anyway, the motor will overheat, and you can regulate the vacuum this way.

Steve Greenfield

That reminds me I must look for my glass nails.... :)


To: Homebrew_PCBs@yahoogroups.com

From: dj@...
Date: Sun, 22 Mar 2009 12:09:19 -0400
Subject: Re: [Homebrew_PCBs] Re: vacuum hold-down for exposure box






"warrenbrayshaw" <warrenbrayshaw@...> writes:
> Sounds like you need a calibrated hole :)

That's why I was looking for my vacuum gauge :)








_________________________________________________________________
Get 30 Free Emoticons for your Windows Live Messenger
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[Non-text portions of this message have been removed]

Oh, and -please- start a topic by opening a fresh new message and addressing it to the group.

When you started a new topic by replying to the Brother Printer thread, even though you replaced the subject line and all quoted text, it still ends up linked to it in the archives.

http://tech.groups.yahoo.com/group/Homebrew_PCBs/message/22265

Steve Greenfield

The trick is not to pull a vacuum in a large cavity beneath the glass, but to pull it between two sheets of glass, or between a sheet of glass and a clear flexible sheet over it.

The plastic would tend to seal down and prevent a good vacuum from being pulled all across the surface, maybe some paper towels placed right up to the edge of the board would allow air to be pulled out.

Steve Greenfield

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:

>
> 
> William Alford <walford@...> writes:
> > I've built several vac hold downs over the years and the trick is to 
> > have the substrate supported everywhere.
> 
> Maybe I missed a bit of info...  the first time I tested it, I had
> nothing in it - just the glass panel with the gasket around the edges.
> I guessed that the panel would be pulled down evenly, and I could
> measure how far.  What happened, obvious in retrospect, is that the
> glass bowed down further in the middle.  My solution, obviously, is to
> use the pcb to support the middle of the glass.  The trick will be to
> support it enough but not too much - I want the glass flat on the
> board at full pressure, not bowed down due to insufficient support or
> arched over due to too much.
> 
> The gasket is 125 mil, the boards range from 8 to 65 mil, each sheet
> of card stock is 8 mil, the film is a few mil, etc.  So I can stack it
> all up so that the glass is pulled down evenly over everything.
>

Note that fabric works very well as vacuum conductor. So you could
conduct your vacuum around with sheets of fabric (different sheets for
different sizes of boards).
However that only works for single sided exposure.

I don't think any vacuum distribution is really needed. The commercial
machines i have seen just suck the cover against the glass and it
pulls the whole surface just fine. Maybe put a wick around the
perimeter if you are really worried.


ST

On Sun, Mar 22, 2009 at 4:12 PM, William Alford <walford@dbtech.net> wrote:
> At 09:44 PM 3/21/2009, DJ Delorie wrote:
>>  converted my UV exposure box to vacuum hold-down.. . . the glass bow in so
>>much I feared it would break!
>
> i've built several vac hold downs over the years and the trick is to
> have the substrate supported everywhere. one way i did this was to
> take a piece of good quality flat plywood and cut parallel groves
> with a table saw in both directions about 1/8 inch deep on one side
> across the entire face of the board. (say, 1/2" apart) spray it with
> acrylic or some other sealer to seal the wood, drill a 3/4" or
> whatever size hole you need to connect to the vacuum line in the
> center of the board and then glue a piece of Formica on the top of
> the grooved side carefully so's not to get glue in the grooves (i
> used contact cement on a 2 ft x 3 ft table that lasted over 20 years
> for screen printing). now you can see from the edges where the
> grooves are and draw pencil lines across the formica and use these
> guides to drill 1/16" holes across the entire surface over the
> grooves beneath. now tape up the edges to seal the ends of the
> grooves and attach the vac hose (maybe with a 90 degree connector).
> you will have to put wooden feet on the bottom so the hose can exit
> from beneath and keep the board sitting level. now whatever size
> board you place on the top, just tape around it's edge to seal off
> the uncovered vac holes and any size board can be accommodated. if
> you want to expose negs to photoresist, you can also place a piece of
> flexible clear plastic over the top of the board/litho neg sandwich
> that covers the entire hold-down surface and get perfect contact for
> exposures. i used to use sunlight to expose and place a toy dart
> stuck on the top edge of the board to orient to the sun. when you
> move the board so that the shadow of the darts shaft disappears, the
> board is exactly perpendicular to the sun's rays. i now have access
> to some free corian and will build one from that which has a
> perfectly flat and smooth surface.
>
>
> William Alford
>
> GI Motility Medical Research Page
> http://alford.grimtrojan.com/
>
> [Non-text portions of this message have been removed]
>

Hmmm... I'm usually pretty careful to not do that, not sure how it got
by me this time.  Sorry.

DJ Delorie  wrote:

> > Sounds like you need a calibrated hole :)
> 
> That's why I was looking for my vacuum gauge :)
>

Teenage vacuum gauges are susceptible to peer pressure and will go missing without explanation.

Should it not return I would make an adapter for the hose with many holes drilled along its length and progressively tape them off until you observe the required push on your stack. If the combined area of all these holes starts out equalling that of the open hose, then the experiment will start at nearly no push.  

Additionally the shop vac is then getting the maximum cooling air available.

Looking forward to you entry in the spirals competition.

Just try some water between the film and the board.  I've found it works fine.

	 
	
	








	


	
	


      

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

If you have a pressure gauge for 1 athmosphere you can usually open it
up and bend a little piece of metal to zero the pointer at "1" and you
have your vacuum gauge.
(No warranty on accuracy, but i've done it and it seemed fine).

ST

On Sun, Mar 22, 2009 at 8:35 PM, warrenbrayshaw
<warrenbrayshaw@paradise.net.nz> wrote:

> DJ Delorie  wrote:
>
>> > Sounds like you need a calibrated hole :)
>>
>> That's why I was looking for my vacuum gauge :)
>>
>
> Teenage vacuum gauges are susceptible to peer pressure and will go missing without explanation.
>
> Should it not return I would make an adapter for the hose with many holes drilled along its length and progressively tape them off until you observe the required push on your stack. If the combined area of all these holes starts out equalling that of the open hose, then the experiment will start at nearly no push.
>
> Additionally the shop vac is then getting the maximum cooling air available.
>
> Looking forward to you entry in the spirals competition.
>
>

KeepIt SimpleStupid <keepitsimplestupid@...> writes:
> Just try some water between the film and the board.  I've found it
> works fine.

Except I want to image a circuit board, not a large grey blob.  The
ink on my films will run if they get wet.

(I assume you really meant "photoresist film" - I've got the laminator
for that.  I'm talking about the photo master for the exposure box)

At 11:54 AM 3/22/2009, Steve wrote:
>The plastic would tend to seal down and prevent a good vacuum from 
>being pulled all across the surface,

i've never had a problem with that in over 20 years, but since my 
vacuum tables have a grid of holes across the entire surface, the 
vacuum path is along the entire perimeter of the board.  but i will 
say that professional screenprinting exposure machines have a piece 
of string about like a venetian blind cord anchored near the vacuum 
outlet hole and this is laid across the substrate out of any artwork 
path and acts like a wick or 'tunnel' for the air to escape during 
the pump down. these professional machines (i own several different 
kinds) have a highly flexible rubber blanket that pulls the substrate 
against the thick rigid glass. Oh, i also use a vacuum pump from an 
old offset press, but it'll take a decent time interval to wear out a 
motor in a shop vac and you can find them cheap all the time in yard 
sales/goodwill stores.


William Alford

GI Motility Medical Research Page
http://alford.grimtrojan.com/  

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

DJ Delorie <dj@...> writes:
> That's why I was looking for my vacuum gauge :)

My wife found it.  I'm drawing about 2.5 in Hg, either with the
stopper or just holding the tube in the airstream (venturi).  So I
built a small wooden venturi-style holder for it, allowing maximum
airflow into the shop vac.

That's only about 115 lbs across the whole glass plate.

What I did, was printed the layout on polyester paper and put a little bit of water between the board and the paper and exposed a sensitized board.

The water's surface tension holds the mask (polyester paper) tight against the board.  Glass is usually used in this step, but water works fine.  We are only talking a few drops or so.


--- On Sun, 3/22/09, DJ Delorie <dj@delorie.com> wrote:

> From: DJ Delorie <dj@...>
> Subject: Re: [Homebrew_PCBs] Re: vacuum hold-down for exposure box
> To: Homebrew_PCBs@yahoogroups.com
> Date: Sunday, March 22, 2009, 4:36 PM
> KeepIt SimpleStupid <keepitsimplestupid@...>
> writes:
> > Just try some water between the film and the board. 
> I've found it
> > works fine.
> 
> Except I want to image a circuit board, not a large grey
> blob.  The
> ink on my films will run if they get wet.
> 
> (I assume you really meant "photoresist film" -
> I've got the laminator
> for that.  I'm talking about the photo master for the
> exposure box)

The ink didn't run?  My ink isn't waterproof.

Hi, i can't really see a point in using vacuum in two rigid flat
surfaces. Two glass parts seems to be used just with springs without the
need of vacuum. Professional vacuum tables use glass under and a really
well design plastic above, its not entirely flat, has a matrix of small
relief squares, its a strong plastic but will perfectly shape to your
board. Maybe can be bought as spare part for this machines.

The vacuum table i have used (professional) work with a pressure of
-0.7bar (1 bar = 100kPa ~ 1atmosphere, Pa is SI unit) , but half seems
enough. To lift the plastic cover we had to wait until the pressure came
to zero again!

About the calibration hole, can also be done regulating the power or rpm
of your vacuum motor pump. A hole from the vacuum table to pump (series)
will not work, but from pump to free air (parallel) yes. (professional
regulators have a weight above/closing this hole, and the pressure
depends on this weight). One source of vacuum pump could be a hot air
solder station, once i opened mine and it has two ends to fit rubber
tubes on the air pump, one air out other air in, but the stupid Chinese
manufactor broke the air in end...

Simao

On Sun, 2009-03-22 at 07:16 +0000, warrenbrayshaw wrote:
> DJ Delorie wrote:
> 
> > 
> > I didn't feel much "suck" on the end of the tube with my finger, but
> > the first time I hooked it up and tested it I saw the glass bow in
> so
> > much I feared it would break! I just need to find out if I can run
> > the shop vac with low air flow for the 5.5 minutes it takes to do an
> > exposure.
> > 
> >
> 
> Sounds like you need a calibrated hole :)
> 
> Just like a domestic vacuum cleaner, have a hole in the vacuum pipe to
> reduce the effective vacuum.
> 
> Warren
> 
> 
> 
> 
>

Simao Cardoso <simaocardoso@...> writes:
> Hi, i can't really see a point in using vacuum in two rigid flat
> surfaces.

I've found that they're not quite "flat" enough.

On Sun, 2009-03-22 at 22:50 -0400, DJ Delorie wrote:
> 
> Simao Cardoso <simaocardoso@...> writes:
> > Hi, i can't really see a point in using vacuum in two rigid flat
> > surfaces.
> 
> I've found that they're not quite "flat" enough.
> 
> 

Maybe is a problem in my English again, but i didn't understand... I
used flat word as a plane surface. Vacuum will always try bend your
glass/plastic by the shape of your pcb. Vacuum don't seem to help with
glass...


> 
>

Well, this thread that wont die gets you thinking:

My first thought was:

glass
fabric
board (incl. artwork and film)
base

to evenly remove the air between the board and the glass. But, uh, the  
UV might not go thru the fabric so evenly ...

Board and glass need to be close to the same size to prevent stress,  
with a flexible seal around them.

Then I thought, you could replace the glass with clear vinyl, which  
will just flow around the board and not bow

Then I thought, make the *bottom* vinyl and eveything is evenly  
pressed UP onto the glass with no stresses at all, and you still get  
that nice even glass.

Then (for the less frequent exposer) why not stick the whole sandwich  
into one of those vacuum  "space bags" you use to shrink your winter  
clothes away with.

(Myself, I think I'll keep on improving my TT skills)

PG

On 23/03/2009, at 1:50 PM, DJ Delorie wrote:

>
> Simao Cardoso <simaocardoso@...> writes:
> > Hi, i can't really see a point in using vacuum in two rigid flat
> > surfaces.
>
> I've found that they're not quite "flat" enough.
>
>

I printed with a laser printer, so no problems.  Besides the non-toner side may have been against the PC board.  With a laser you can always mirror image.

With my Epson Artisan 800 Inkjet, I can mirror.
With an HP Laserjet 2014dn PostScript I can also mirror. 

Ink jet might bleed through polester, but toner won't.

Give it a shot.

Basically just rinse the board in some water. Shake off the excess water, but don't dry it.  Lay the mask over the board.  Expose.

--- On Sun, 3/22/09, DJ Delorie <dj@...> wrote:

> From: DJ Delorie <dj@...>
> Subject: Re: [Homebrew_PCBs] Re: vacuum hold-down for exposure box
> To: Homebrew_PCBs@yahoogroups.com
> Date: Sunday, March 22, 2009, 10:23 PM
> The ink didn't run?  My ink isn't waterproof.

The good part about the water method, is that it lends itself very well to double sided boards.  

On the outer edge drill two small holes the size of a thumbtack.  You can use these holes a fudicuary marks and line up the mask and do double sided boards with ease.  Two holes in the board and two holes in the mask.

UV light
(Some part of tack sticks up here)
Mask
Circuit board
2 thumbtacks with the head of the tack on the bottom side

On Mon, 23 Mar 2009 14:13:13 +1100, you wrote:



I'd be tempted to do the following:

1) use a piece of vinyl (upholstery type) for the bottom.
2) make an odd older out of scraps of PC board, same thickness as your
board.  Air channels as needed, plenum or whatever for a cover with
grooves in it for vacuum.
3) upper layer is more vinyl, or plastic.  glass could be used for the
bottom as well.
4) lights on both sides.

Vacuum does not have to be extreme.  1/10 atmosphere is still 1.47
pounds per square inch pressure on the board.  Ought to be enough.

I've mad a vacuum frame for one sided work out of shelving with a 1/4
inch hole matrix (1 inch spacing), holes for shop vac.  Light frame on
top.  Upholstery vinyl for the cover.  Old photographic enlarger timer
for exposure.  You might find a lot of them now that digital has
"won"... (not really, but they ought to be easy to find).

Harvey

>Well, this thread that wont die gets you thinking:
>
>My first thought was:
>
>glass
>fabric
>board (incl. artwork and film)
>base
>
>to evenly remove the air between the board and the glass. But, uh, the  
>UV might not go thru the fabric so evenly ...
>
>Board and glass need to be close to the same size to prevent stress,  
>with a flexible seal around them.
>
>Then I thought, you could replace the glass with clear vinyl, which  
>will just flow around the board and not bow
>
>Then I thought, make the *bottom* vinyl and eveything is evenly  
>pressed UP onto the glass with no stresses at all, and you still get  
>that nice even glass.
>
>Then (for the less frequent exposer) why not stick the whole sandwich  
>into one of those vacuum  "space bags" you use to shrink your winter  
>clothes away with.
>
>(Myself, I think I'll keep on improving my TT skills)
>
>PG
>
>

--- In Homebrew_PCBs@yahoogroups.com, Piers Goodhew <piers@...> wrote:
>
> 
> Then (for the less frequent exposer) why not stick the whole sandwich  
> into one of those vacuum  "space bags" you use to shrink your winter  
> clothes away with.
> 

Along that line of thought, one thing I tried about a year or so ago was heat shrink plastic like you find wrapping music or video CD's.

I bought some from ULine for relatively cheap and more than I could ever use. I heat sealed the board and mask inside of the pouch and ran the whole thing through my laminator. to shrink the plastic wrap. 

The biggest problem I had was that the corners would not shrink evenly and was somewhat wrinkled. However in the center the mask was held quite tightly to the board. I have not done anymore testing since then, but that would be an option if someone wanted to try a vacuum-less method.

If you do that you may as well stick to a sheet of foam rubber
pressing the stack up against the glass and dump the vacuum.

I sort of thought the whole purpose was to get a double-sided exposure machine.

ST

On Mon, Mar 23, 2009 at 4:13 AM, Piers Goodhew <piers@...> wrote:

>
> Then I thought, make the *bottom* vinyl and eveything is evenly
> pressed UP onto the glass with no stresses at all, and you still get
> that nice even glass.
>

KeepIt SimpleStupid <keepitsimplestupid@...> writes:
> I printed with a laser printer, so no problems.

Hmmm... I tried using the laser printer for UV exposure, but (1) the
toner didn't block much UV, and (2) the resolution was poor compared
to my inkjet.  With the laser, the best I could do was 7 mil or so.

Plus, aren't you supposed to put the ink side *towards* the board, to
avoid the extra 8 mil or so distance which may blur the edges some?
The whole point of this is to get the image (ink) as close to the
photomask as possible, to get the cleanest edges.

Stefan Trethan <stefan_trethan@...> writes:
> If you do that you may as well stick to a sheet of foam rubber
> pressing the stack up against the glass and dump the vacuum.

I suppose, if I could figure out how to hold the glass down.  Not much
extra room around the edges for screws, the box is sized to fit the
glass with little margin.

> I sort of thought the whole purpose was to get a double-sided
> exposure machine.

No, it's a single sided exposure box.  I'm just trying to hold the
film against the board.  Old way: the pcb sits on the plywood bottom
of the box, the film sits on that, the glass sits on that.  Expose
from the top.  New way: similar, but pcb sits on stack of paper, glass
has gasket, vacuum sucks out air between pcb, film, and glass, holding
the film against the photomask.

For DS boards I etch the two sides separately so I can align the films
more accurately.

I haven't found another good source yet.  Some of it was lying around from 20 years ago.  I do know the paper I used was translucent and made from polyester.

Probably something like this stuff.

http://inapatecno.com/en/site/172/173/i167/i167_3/page/products/index.xml

--- On Mon, 3/23/09, DJ Delorie <dj@...> wrote:

From: DJ Delorie <dj@...>
Subject: Re: [Homebrew_PCBs] Re: vacuum hold-down for exposure box
To: Homebrew_PCBs@yahoogroups.com
Date: Monday, March 23, 2009, 3:53 AM











    
            

KeepIt SimpleStupid <keepitsimplestupid@ yahoo.com> writes:

> I printed with a laser printer, so no problems.



Hmmm... I tried using the laser printer for UV exposure, but (1) the

toner didn't block much UV, and (2) the resolution was poor compared

to my inkjet.  With the laser, the best I could do was 7 mil or so.



Plus, aren't you supposed to put the ink side *towards* the board, to

avoid the extra 8 mil or so distance which may blur the edges some?

The whole point of this is to get the image (ink) as close to the

photomask as possible, to get the cleanest edges.


 

      

    
    
	
	 
	
	








	


	
	


      

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

That looks like standard transparency paper for overhead projectors.
Could you use that stuff?  It's available at any office supply store.

On Mon, Mar 23, 2009 at 1:59 AM, KeepIt SimpleStupid
<keepitsimplestupid@...> wrote:
> I haven't found another good source yet.  Some of it was lying around from 20 years ago.  I do know the paper I used was translucent and made from polyester.
>
> Probably something like this stuff.
>
> http://inapatecno.com/en/site/172/173/i167/i167_3/page/products/index.xml
>

-- 
Erik L. Knise
Pacific Shipping Company
Seattle, WA

The Polyester paper I used is translucent, not clear.  The ink adheres extremely well.  Transparency paper suffers from uniformity problems.

--- On Mon, 3/23/09, Erik Knise <elknise@...> wrote:

From: Erik Knise <elknise@...>
Subject: Re: [Homebrew_PCBs] Re: vacuum hold-down for exposure box
To: Homebrew_PCBs@yahoogroups.com
Date: Monday, March 23, 2009, 2:15 PM











    
            That looks like standard transparency paper for overhead projectors.

Could you use that stuff?  It's available at any office supply store.



On Mon, Mar 23, 2009 at 1:59 AM, KeepIt SimpleStupid

<keepitsimplestupid@ yahoo.com> wrote:

> I haven't found another good source yet.  Some of it was lying around from 20 years ago.  I do know the paper I used was translucent and made from polyester.

>

> Probably something like this stuff.

>

> http://inapatecno. com/en/site/ 172/173/i167/ i167_3/page/ products/ index.xml

>



-- 

Erik L. Knise

Pacific Shipping Company

Seattle, WA


 

      

    
    
	
	 
	
	








	


	
	


      

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

KeepIt SimpleStupid <keepitsimplestupid@...> writes:
> The Polyester paper I used is translucent, not clear.  The ink
> adheres extremely well.  Transparency paper suffers from uniformity
> problems.

Sounds like vellum.