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I guess the other obvious place to look for these lamps is the supplier you use to purchase other PCB-making goods (board, developer, etc.). The suppliers I use in the UK for such materials (RS Components, Farnel, Rapid Electronics...) sell suitable lamps, and complete exposure units designed for the job too.

Regards,
Tony

Hi John,

What you want is called a "germicidal lamp". It is a clear glass
fluorescent lamp. Mine is about 14 inches long. I bought it and a
holder for about $20 (quite some time ago). Ask for one at an
electrical supply house.

HTH

Alan KM6VV

johnman9146 wrote:

It takes only low UV to expose the photoresist used for PCBs. So a
blacklight will work, however, anything that gives off low UV will
work. Like plant grow lights, those slightly bluish lights you can
get even at the hardware store.

Steve Greenfield

--- crankorgan <john@...> wrote:

Hi,
Years ago I tried to locate a UV light to erase Eproms. I
got alot of bad info. The Blacklight for posters is not
the right wavelength. UV bulbs look like a clear florescent
light bulb. They used to come with a drop of mercury in them.
After
trying to buy one, I found one in a Tropical Fish store. They
are used in a Sterilizer. Water passes past the bulb and the
germs in the water are killed. Do not look at the light while
it is on!!! It may look like it is not bright but it can give
you welders flash! You will wake up 2 o'clock in the morning with
the feeling sand is in your eyes. Be careful!

John

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Even better is to get some real flourescent UV bulbs. I got mine from a
local lighting supply house. I just looked for light bulbs in the yellow
pages. The bulbs are F20T12/BL and cost me about $10 per tube when I bought
them last year. They are a 2' long bulb and go into a standard fixture that
I got at Home Depot. I added a 5 minute mechanical timer to control the
exposure.

Tim
[Denver, CO]

--- 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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--- johnman9146 wrote:

Several of you have written of the benefits and good quality that
can
be had by using the photoresist copper clad boards. You now have
my
interest.

-snip-

So please, if you could help me build a UV light source to expose

small PCB's, I would appreciate it.

It has been a while since I did photoresist, but I used to use an
incandescent plant grow light. I suspect the fluorescent grow
lights give off more UV.

Steve Greenfield




=====
Steve Greenfield // Digital photo scanning, retouching,
Polymorph Digital Photography // and photomorphing to your specs.
253/318-2473 voice // We use the best little computer in
polymorph@... // the world, the Amiga!
// Based in Tacoma, WA, USA

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Hi,
Years ago I tried to locate a UV light to erase Eproms. I
got alot of bad info. The Blacklight for posters is not
the right wavelength. UV bulbs look like a clear florescent
light bulb. They used to come with a drop of mercury in them. After
trying to buy one, I found one in a Tropical Fish store. They
are used in a Sterilizer. Water passes past the bulb and the
germs in the water are killed. Do not look at the light while
it is on!!! It may look like it is not bright but it can give
you welders flash! You will wake up 2 o'clock in the morning with
the feeling sand is in your eyes. Be careful!

John




--- In Homebrew_PCBs@y..., "johnman9146" <johnman@d...> wrote:

Several of you have written of the benefits and good quality that

can

be had by using the photoresist copper clad boards. You now have

my

interest.

I have some of the raw materials to attempt this method including

pre-

sensitized copper clad, and developer. I even have glass plates to
keep the transparancy in close contact with the copper.

I do not have a UV light source. I didn't buy one as I didn't want
to spend the money. Some of you have told me that you made a light
box. What types of lights/lamps work for exposure? I saw

somewhere

that a blacklight works. Is this true?

Our old Diazo machine at work seems to have a long
flourescent "black" light that it uses to expose diazo paper.
(BLUELINE MACHINE). How would I construct a lightbox for exposure?

Most if not all my PCB's are small. Thje biggest board that I have
etched was 5x7, so I don't need a giant box.

I don't need any help with making transparancies as I have access

to

a photoplotter (typesetting machine that directly exposes film).
There are no issues with film growth as there is no heat in the
process. There are no issues with pinholes/banding as this is a
professional imager used to expose printing plates for magazine
reproduction. All I must do is output 1-to-1 EPS file and the

imager

does the rest.

So please, if you could help me build a UV light source to expose
small PCB's, I would appreciate it.

Thanks

Several of you have written of the benefits and good quality that can
be had by using the photoresist copper clad boards. You now have my
interest.

I have some of the raw materials to attempt this method including pre-
sensitized copper clad, and developer. I even have glass plates to
keep the transparancy in close contact with the copper.

I do not have a UV light source. I didn't buy one as I didn't want
to spend the money. Some of you have told me that you made a light
box. What types of lights/lamps work for exposure? I saw somewhere
that a blacklight works. Is this true?

Our old Diazo machine at work seems to have a long
flourescent "black" light that it uses to expose diazo paper.
(BLUELINE MACHINE). How would I construct a lightbox for exposure?

Most if not all my PCB's are small. Thje biggest board that I have
etched was 5x7, so I don't need a giant box.

I don't need any help with making transparancies as I have access to
a photoplotter (typesetting machine that directly exposes film).
There are no issues with film growth as there is no heat in the
process. There are no issues with pinholes/banding as this is a
professional imager used to expose printing plates for magazine
reproduction. All I must do is output 1-to-1 EPS file and the imager
does the rest.

So please, if you could help me build a UV light source to expose
small PCB's, I would appreciate it.

Thanks

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
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.

I already own one. I tried using it before, but didn't like the
results. I even modified a couple of pens as I thought this might be
an easy way to "draw" boards to etch. I have owned this plotter
since new a long time ago.....

The main problems I had with trying the plotter were:

1. The ink would not last through the etch. At the time I think I
had tried to use a OHT marker (cut it off and used one of the plotter
pen bodies).

2. When the pen would "land" on the copper, tiny ink droplets would
splatter and make a mess of the fine traces.

3. The speed seemed WAY too fast to get nice dark lines that you
could get by hand with the same pen.

4. Securing the board to backing paper. As the plotter requires
paper to "grip". (The paper movement also seemed WAY too fast and
would sometimes move the board out of registration.)

5. The process seemed slow, and since I never got a decent board to
etch with this method, I abandoned it.

The plotter now once again collects dust in the closet :(

If you have any ideas to try, or like you said, software to try I
would be game to try it once again as I would like to get some more
use out of this practically new plotter.

like the HP7475a which I own, I've written some code to also use it
as an XY pen-plotter.

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.

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 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.

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

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

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

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.

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.

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

--- 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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