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Photo-etch light source?

U

Usual Suspect

Jan 1, 1970
0
MG Chemicals sells pre-sensitized copper-clad PCB blanks for use with their
exposure and etch kit. Pretty straightforward "print pattern on transparency;
place on PCB; expose to light; wash off exposed portion; etch" process.

The "expose" part of this process consists of using MGC's "daylight"
fluorescent lamp.

If it's truly a "daylight" bulb, wouldn't direct sunlight work for this
purpose? I presume this bulb is of a particular wavelength. What is it?

Any other ideas to use this process to etch PCBs without their lamp?

Thanks,
 
J

John Popelish

Jan 1, 1970
0
Usual said:
MG Chemicals sells pre-sensitized copper-clad PCB blanks for use with their
exposure and etch kit. Pretty straightforward "print pattern on transparency;
place on PCB; expose to light; wash off exposed portion; etch" process.

The "expose" part of this process consists of using MGC's "daylight"
fluorescent lamp.

If it's truly a "daylight" bulb, wouldn't direct sunlight work for this
purpose? I presume this bulb is of a particular wavelength. What is it?

Any other ideas to use this process to etch PCBs without their lamp?

I use sunlight to expose all my boards. The only difficulty
is waiting for a clear sky, so the exposure is predictable
and the edges are sharp.
 
J

John Barrett

Jan 1, 1970
0
Usual Suspect said:
MG Chemicals sells pre-sensitized copper-clad PCB blanks for use with
their
exposure and etch kit. Pretty straightforward "print pattern on
transparency;
place on PCB; expose to light; wash off exposed portion; etch" process.

The "expose" part of this process consists of using MGC's "daylight"
fluorescent lamp.

If it's truly a "daylight" bulb, wouldn't direct sunlight work for this
purpose? I presume this bulb is of a particular wavelength. What is it?

Any other ideas to use this process to etch PCBs without their lamp?

Thanks,

"daylight" flourescents are easy to get at your local home store -- as are
the fixtures to run them -- buddy of mine used just one... but had some
problems with fuzzing that I think would have been solved had he used 2 or 3
for a more even light source -- making an exposure box with 2 or 3 lamps --
the ones about 12" long, and a piece of plexi as the exposure surface is
pretty easy.
 
P

petrus bitbyter

Jan 1, 1970
0
John Popelish said:
I use sunlight to expose all my boards. The only difficulty is waiting
for a clear sky, so the exposure is predictable and the edges are sharp.

Waiting for a clear sky may take days or even weeks in this part of the
world. Even then exposure time is a long shot. So for years I used a 120W
high pressure mercury bulb, meant for streetlighting. It not only produced
enough UV, it also produced a lot of visible light and even much more heat.
So last year I got an obsolete A4 flatbed scanner and an old home solarium -
"face browner" - and build a new exposure box. Works like a charm so the old
one is for sale now :) The idea of the new exposure box is not new. Look at
http://gathering.tweakers.net/forum/list_messages/730455
The text is Dutch but the pictures are universal.

Exposure time is 2 min. Make sure the traces on the transparency are pitch
black. I always stack two of them as one lets through too much UV and makes
the etched copper look like a rats dinner.

petrus bitbyter
 
T

Tim

Jan 1, 1970
0
Waiting for a clear sky may take days or even weeks in this part of the
world. Even then exposure time is a long shot. So for years I used a 120W
high pressure mercury bulb, meant for streetlighting. It not only produced
enough UV, it also produced a lot of visible light and even much more heat.
So last year I got an obsolete A4 flatbed scanner and an old home solarium -
"face browner" - and build a new exposure box. Works like a charm so the old
one is for sale now :) The idea of the new exposure box is not new. Look at
http://gathering.tweakers.net/forum/list_messages/730455
The text is Dutch but the pictures are universal.

Exposure time is 2 min. Make sure the traces on the transparency are pitch
black. I always stack two of them as one lets through too much UV and makes
the etched copper look like a rats dinner.

petrus bitbyter
Stack 2 of them eh? I never thought of that. I used a tanning bulb for
exposing the board when I did that stuff. I built an exposing table with
a timer that kept the bulb on for 15 minutes. It had the timer built
into the table, and a piece of soft wall conduit that supported the lamp
so it was 12" from the board surface. Worked great too! Probably would
have been more reliable using 2 transparencies.

I have since switched to the photo paper method published by Thomas P.
Goote, and I find very reliable and sufficiently accurate for my needs.
FYI, I use ammonium persulfate to etch the boards I make. Check out his
web page here; http://www.fullnet.com/~tomg/gooteepc.htm

Have fun!

- Tim -
 
J

Jan Panteltje

Jan 1, 1970
0
If it's truly a "daylight" bulb, wouldn't direct sunlight work for this
purpose? I presume this bulb is of a particular wavelength. What is it?

Any other ideas to use this process to etch PCBs without their lamp?

Thanks,

Sure, 250W photolamp at 30cm distance for 8 minutes.
Except for DownUnder, where these lightbulbs will be illegal soon.
 
B

Barry Lennox

Jan 1, 1970
0
MG Chemicals sells pre-sensitized copper-clad PCB blanks for use with their
exposure and etch kit. Pretty straightforward "print pattern on transparency;
place on PCB; expose to light; wash off exposed portion; etch" process.

I don't know about the MG system, but I have used sunlight a number of
years ago. It works well, the only problem is that it's variable
depending upon cloud cover and the time of year. Experiments are
needed to get the exact exposure.

I now use a Philips TUV 20 flouro lamp and it works fine. However, it
is a short wavelength UV and the radiation is considered a little
hazardous, I just take care to only switch in on when the artwork is
all set-up and everything is covered.

Barry
 
E

Ecnerwal

Jan 1, 1970
0
Any other ideas to use this process to etch PCBs without their lamp?

I've used a 100W mercury vapor lamp, up close and personal. Most of the
resists are looking for some UV component. A metal-halide fixture will
probably also work well, a sodium vapor light probably would not. 175W
is probably easier to find than 100W, that just happened to be the lamp
I had handy at the time.

A carbon arc would be just dandy, and could offer some old-fashioned
electro-mechanics for a bit of variety in your projects.
 
L

Lionel

Jan 1, 1970
0
MG Chemicals sells pre-sensitized copper-clad PCB blanks for use with their
exposure and etch kit. Pretty straightforward "print pattern on transparency;
place on PCB; expose to light; wash off exposed portion; etch" process.

The "expose" part of this process consists of using MGC's "daylight"
fluorescent lamp.

If it's truly a "daylight" bulb, wouldn't direct sunlight work for this
purpose?

Yes, but it's very hard to get an accurate exposure with sunlight.
I presume this bulb is of a particular wavelength. What is it?

Any other ideas to use this process to etch PCBs without their lamp?

I've heard that greenhouse fluorescent tubes (the kind used for
hydroponics) work okay, but I don't have any personal experience with
them.
 
S

Sergey Kubushin

Jan 1, 1970
0
Yes, but it's very hard to get an accurate exposure with sunlight.
I've heard that greenhouse fluorescent tubes (the kind used for
hydroponics) work okay, but I don't have any personal experience with
them.

I wonder guys, why wouldn't you just use a proper long-wave UV bulb? They
are aplenty and dirt cheap... Any T8 BL or BLB works like a charm, doesn't
require anything but regular fluorescent ballast to run and produces that
very sub-400nm lightwave required for exposure...

Why are you trying anything but a proper tool? Am I missing something?

Just FUI -- that magical MGC lamp is just a 15 Watt T8 BL bulb in a regular
fluorescent fixture...
 
B

Bob Masta

Jan 1, 1970
0
MG Chemicals sells pre-sensitized copper-clad PCB blanks for use with their
exposure and etch kit. Pretty straightforward "print pattern on transparency;
place on PCB; expose to light; wash off exposed portion; etch" process.

The "expose" part of this process consists of using MGC's "daylight"
fluorescent lamp.

If it's truly a "daylight" bulb, wouldn't direct sunlight work for this
purpose? I presume this bulb is of a particular wavelength. What is it?

Any other ideas to use this process to etch PCBs without their lamp?


If you want to stick with photo-resist methods, the simplest
approach is to buy a "tanning" lamp. Mine looks like a standard
floodlamp, with a dimple in the center. Puts out plenty of UV,
way more than direct sunlight (at least here in Michigan!) and
it's consistent even on cloudy days. <g>

Now, I should add that it's been a "few" years since I bought
this (20 or more) so they may not be so readily available as
they once were. Even back then, it was pretty clear that
tanning was not such a smart idea. Now, you'd have to be
pretty crazy or illiterate to do it... which means only 99% of
students and only half of the voting public. ;-) So the
market and supply for these may have slacked off a bit.

Best regards,




Bob Masta

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!
 
G

Guest

Jan 1, 1970
0
i used a Gralab photo timer with a single 200 watt standard incandescent
about 3 feet above the bench.

standard safelight was handy also.

i tape the film onto the pc board. then a single sheet of window glass
weights the film/pc board flat.

after 25 yrs, no problems.

time to expose ? always went with about 4-5 minutes. it depended on the
ants in my pants. critical it is not,

the solvent bath later i found was the real problem with leaving in too
long.

i always used photo filmed positives, very precise and failsafe.
 
U

Usual Suspect

Jan 1, 1970
0
i used a Gralab photo timer with a single 200 watt standard incandescent
about 3 feet above the bench.

Nothin' could be simpler...
standard safelight was handy also.

i tape the film onto the pc board. then a single sheet of window glass
weights the film/pc board flat.

after 25 yrs, no problems.

Now, that's a tome of data!
time to expose ? always went with about 4-5 minutes. it depended on the
ants in my pants. critical it is not,

OK. I won't be a "clock watcher".
the solvent bath later i found was the real problem with leaving in too
long.

You mean the chemical for removing the exposed photo-sensitive stuff from the
PCB? Don't you just submerge it and brush it and watch when it's all gone
(all the exposed part) then take it out? Or am I missing something?
i always used photo filmed positives, very precise and failsafe.

You're talking about the transparency? I hear that output from a printer is
good enough. No?
 
G

Grostle News

Jan 1, 1970
0
If it's truly a "daylight" bulb, wouldn't direct
sunlight work for this purpose? I presume this
bulb is of a particular wavelength. What is it?

Manufacturers of fluorescent light bulbs provide wavelength and light
intensity data for their products. If you have the bulb stock number try
putting this into google search engine. The retailers of light bulbs
sometimes have product info sent to them by manufacturer. Catalogs used
by retailers for ordering may have such info. You can always write to
the company manufacturer to get product specifications.

There are other applications using bulbs for photo light or chemical
reactions. Some types of silk screen processes use exposure bulbs.
Diazo-blueprint photo process uses UV light bulbs. E-prom devices use UV
to erase content. UV bulbs are used in medical applications for
sterilization.

If you get a bulb but need a fixture you can use a screw-in energy
saving fluorescent light bulb.
In my area these screw-in energy savers cost less than a dollar. I
removed the bulb from one of these then replaced it with the fluorescent
bulb I wanted to operate. I made sure the wattage ratings for both were
nearly the same before I started. The re-wiring should be as short as
possible. Be careful and don't forget that fluorescent bulbs run on
higher voltage.

btw- I have replaced all incandescent lights in my apartment with the
screw-in fluorescent fixtures and have seen a significant savings in
electric bill.
 
W

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Jan 1, 1970
0
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G

Guest

Jan 1, 1970
0
the developer/xylene (or whatever it is) i never made any mechanical
brushing or other attempt to force the residue to release any faster than
the dissolving rate.

my problem originally was i left the exposed board in way tooooo long and
the light fixed resist actually did disssolve eventually, perhaps 20
minutes! way too long

stick with the manufacturers recommends

i always did a second wash in fresh developer to remove any trace residual.

then after it had completely dried/evaporated, it went under some cool then
warm water with small amt of detergent (actually any wetting agent will do,
the blu stuff used in automatic dishwashers is cheap and easy to find)
before it went into the etch bath. that seemed to make the etch time
consistent across the entire board.

yes, the transparency may be made with printer, i have used a good 600 dpi
laser printer (overkill actually) but 300 or even 150 dpi will do.

vellum is usable, overhead mylar film is better, plain paper is good for
crude stuff

my only hazard with that was the 200 watt bulb often melted the toner and
screwed up the board. so i switched to using photo exposed
negatives/positives. it takes longer, but results are far superior and the
physical stability of the film always gives u the same dimensions EVERY
TIME. thats assuming u make it a proper size initially! detail and
resolution are superior also.

short runs of less than ten units, i usually winged it with the printer
though.
 
G

Grostle News

Jan 1, 1970
0
BTW- If you ever need to measure light intensity directly, such as
lumens/candela etc it is possible to do this with the built-in light
meter most 35mm cameras are equipped with. I did this many moons ago so
I don't recall the details.

Here is an explanation I just now found in google about the procedure,
just in case any one is interested:

http://fins.actwin.com/aquatic-plants/month.9711/msg00049.html

saxum g.n.
 
G

Grostle News

Jan 1, 1970
0
hapticz said:
the developer/xylene (or whatever it is)
Safety reminder: If you use Xylene don't forget that this liquid is as
flammable as gasoline. Vapors of xylene from an open container or an
evaporating source can crawl invisibly and without detection of it's
odor to an ignition point (pilot light, static discharge, electric range
etc.)

Xylene should be used in a well-ventilated area nowhere near any flame
or possible spark.

saxum g.n.
 
L

Lionel

Jan 1, 1970
0
BTW- If you ever need to measure light intensity directly, such as
lumens/candela etc it is possible to do this with the built-in light
meter most 35mm cameras are equipped with. I did this many moons ago so
I don't recall the details.

Here is an explanation I just now found in google about the procedure,
just in case any one is interested:

http://fins.actwin.com/aquatic-plants/month.9711/msg00049.html

Good tip. That should work fine with more modern - even digital - SLR
cameras, as long as they have a full manual mode, eg; any Canon or
Nikon DLSR. The only problem is that the table in that post is for
ASA/ISO 25, which isn't available on many DSLRs. Fortunately, that's
easy to correct, by converting it for ISO 100 (2 stops faster), which
most DSLRs have, then shifting the shutter speed by 2 stops to
compensate:

*OLD* ASA/ISO 25 @ 1/60:
f-stop foot-candles
2 100
2.8 200
4 400
5.6 800
8 1,600
11 3,200

*NEW* ISO 100 @ 1/250:
f-stop foot-candles
2 100
2.8 200
4 400
5.6 800
8 1,600
11 3,200

Please note the comments about metering on white objects vs green,
etc, in the original post at that URL.
 
B

Bob Masta

Jan 1, 1970
0
Good tip. That should work fine with more modern - even digital - SLR
cameras, as long as they have a full manual mode, eg; any Canon or
Nikon DLSR. The only problem is that the table in that post is for
ASA/ISO 25, which isn't available on many DSLRs. Fortunately, that's
easy to correct, by converting it for ISO 100 (2 stops faster), which
most DSLRs have, then shifting the shutter speed by 2 stops to
compensate:

*OLD* ASA/ISO 25 @ 1/60:
f-stop foot-candles
2 100
2.8 200
4 400
5.6 800
8 1,600
11 3,200

*NEW* ISO 100 @ 1/250:
f-stop foot-candles
2 100
2.8 200
4 400
5.6 800
8 1,600
11 3,200

Please note the comments about metering on white objects vs green,
etc, in the original post at that URL.

The problem with this approach (regarding the original photo-etch
topic in the subject line) is that it only applies to visible light,
whereas photo-resist is sensitive to UV, which is greatly
reduced by camera lenses.

So, you can't use this to make any sort of absolute measurement
of UV levels, but if you have a source that emits a broad spectrum
(like a tanning lamp) such that you can get a reading on the meter,
then it would probably be reasonable to assume that everything
scales properly. Thus, if you use that same source at a different
distance, the camera meter could tell you the *change* in
exposure.

Best regards,


Bob Masta

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!
 
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