Electrical Engineering - Photo-etch light source?

Author

Photo-etch light source?

Usual Suspect

2007-03-04, 1:25 pm

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,
--
Al, the usual

John Popelish

2007-03-04, 1:25 pm

Usual Suspect wrote:
> 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.

John Barrett

2007-03-04, 1:25 pm

"Usual Suspect" <reply@thegroup.net> wrote in message
news:0001HW.C2104D2E025D5113F01826C8@news.sf.sbcglobal.net...
> 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,
> --
> Al, the usual
>

"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.

petrus bitbyter

2007-03-04, 1:25 pm

"John Popelish" <jpopelish@rica.net> schreef in bericht
news:WOydnZ4O8KR3kHbYnZ2dnUVZ_t7inZ2d@adelphia.com...
> Usual Suspect wrote:
>
> 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...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

Tim

2007-03-04, 5:25 pm

In article <45eb186d$0$27917$e4fe514c@dreader24.news.xs4all.nl>,
pieterkraltlaatditweg@enditookhccnet.nl says...
>
> "John Popelish" <jpopelish@rica.net> schreef in bericht
> news:WOydnZ4O8KR3kHbYnZ2dnUVZ_t7inZ2d@adelphia.com...
>
> 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...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 -

Jan Panteltje

2007-03-04, 5:25 pm

On a sunny day (Sun, 04 Mar 2007 18:14:40 GMT) it happened Usual Suspect
<reply@thegroup.net> wrote in
<0001HW.C2104D2E025D5113F01826C8@news.sf.sbcglobal.net>:

>
>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.

Barry Lennox

2007-03-04, 5:25 pm

Ecnerwal

2007-03-04, 8:25 pm

In article <0001HW.C2104D2E025D5113F01826C8@news.sf.sbcglobal.net>,
Usual Suspect <reply@thegroup.net> wrote:
> 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.

--
Cats, coffee, chocolate...vices to live by

Lionel

2007-03-04, 8:25 pm

Bob Masta

2007-03-05, 9:25 am

On Sun, 04 Mar 2007 18:14:40 GMT, Usual Suspect <reply@thegroup.net>
wrote:

>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!

Sergey Kubushin

2007-03-05, 5:25 pm

In sci.electronics.misc Lionel <usenet@imagenoir.com> wrote:
> On Sun, 04 Mar 2007 18:14:40 GMT, Usual Suspect <reply@thegroup.net>
> wrote:

[color=darkred]
> Yes, but it's very hard to get an accurate exposure with sunlight.

[color=darkred]
> 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...

---
******************************************************************
* KSI@home KOI8 Net < > The impossible we do immediately. *
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************

--
Posted via a free Usenet account from http://www.teranews.com

2007-03-06, 9:25 am

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.

"Usual Suspect" <reply@thegroup.net> wrote in message
news:0001HW.C2104D2E025D5113F01826C8@news.sf.sbcglobal.net...
> 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,
> --
> Al, the usual
>

Usual Suspect

2007-03-06, 1:25 pm

> 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?

--
Al, the usual

www.china-powerseller.com

2007-03-07, 1:25 pm

Dear friend :
It is my fortunate writing to you . you will discover this is a wealth
accumulation place.
The website of our company is http://www.china-powerseller.com
We are a big agent for Laptop
Mobile Phone\Digital Camera\CDJ\DJM\Apple Ipod\PSP\VEDEO GAMES
\Television\GPS\Telescope in CHINA .
All of our commodities is the most advanced quality but lowest price.
we also have the

safest and most
convenient transaction way to guarante the transaction arries on
normally .
looking forward to your coorporation and cause all of us both to
profit.
you can contact us by Email:china.seller#hotmail.com
MSN: china.seller#hotmail.com
best wishes!
your sincerely

http://www.china-powerseller.com
MSN/Email: china.seller@hotmail.com

2007-03-08, 1:25 pm

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.

"Usual Suspect" <reply@thegroup.net> wrote in message
news:0001HW.C212E99D02CFFC6CF01826C8@news.sf.sbcglobal.net...
incandescent[color=darkred]
>
> Nothin' could be simpler...
>
>
> Now, that's a tome of data!
>
the[color=darkred]
>
> OK. I won't be a "clock watcher".
>
>
> 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?
>
>
> You're talking about the transparency? I hear that output from a printer
is
> good enough. No?
>
> --
> Al, the usual
>

sirkituk

2007-03-09, 9:25 am

[color=darkred]

Time depends on strength of developer, temperature and speed of the
resist.
[color=darkred]
> the

I use sodium hydroxide solution to develop and a brush to speed the
process.
[color=darkred]
>
> is

Yes.Beware of laser printing onto acetate sheet it can melt the sheet
and wreck the printer.
I use good quality tracing paper and find it works well with both
laser printers and highest density ink jet printers.

Regards sirkituk
www.geocities.com/sirkituk.htm

Lionel

2007-03-09, 1:25 pm

On 9 Mar 2007 05:15:25 -0800, "sirkituk" <sirkituk@yahoo.co.uk> wrote:

>
>Yes.Beware of laser printing onto acetate sheet it can melt the sheet
>and wreck the printer.

Yes. You need to use acetate sheets that are specifically labelled as
being suitable for photocopiers or laser printers. They are perfectly
safe for this purpose. Ones intended for inkjet ARE NOT safe in
lasers. Don't take the salesperson's word for it, check the label on
the box yourself.

>I use good quality tracing paper and find it works well with both
>laser printers and highest density ink jet printers.

I've heard others say that too, but haven't tried it myself. Can you
recommend any specific brands?

--
W "Some people are alive only because it is illegal to kill them."
. | ,. w ,
\|/ \|/ Perna condita delenda est
---^----^---------------------------------------------------------------

Usual Suspect

2007-03-09, 1:25 pm

> 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 meant to say "submerge it in developer..."

> I use sodium hydroxide solution to develop and a brush to speed the
> process.

The MG Chemicals demo video
< http://www.mgchemicals.com/download...otofablarge.wmv>
shows that there is a developer solution into which the exposed PCB needs to
be developed. They just use a foam brush to brush off the exposed resist.
Looks like a pretty quick process.

Are you using NaOH in place of the developer? To supplement the developer? Or
are you using it as a wash to remove the unneeded (exposed) resist after
development?

And are you using MG Chem. PCBs? (Just want to understand what chems work
with what boards...)

> I use good quality tracing paper and find it works well with both
> laser printers and highest density ink jet printers.

A great idea.

Thanks,
--
Al, the usual

Jamie

2007-03-12, 5:25 pm

"Sergey Kubushin" <ksi@koi8.net> wrote in message
news:45eba505$0$16391$88260bb3@free.teranews.com...
> In sci.electronics.misc Lionel <usenet@imagenoir.com> wrote:
>
>
>
>
>
> 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...
>
> ---
> ******************************************************************
> * KSI@home KOI8 Net < > The impossible we do immediately. *
> * Las Vegas NV, USA < > Miracles require 24-hour notice. *
> ******************************************************************
>
> --
> Posted via a free Usenet account from http://www.teranews.com
>
FWIW-
Some people just enjoy the challenge of re-inventing the wheel...
Jamie

sirkituk

2007-04-23, 8:25 pm

On Mar 9, 6:52 pm, Usual Suspect <r...@thegroup.net> wrote:
>
> I meant to say "submerge it in developer..."
>
>
> The MG Chemicals demo video
> <http://www.mgchemicals.com/download...otofablarge.wmv>
> shows that there is a developer solution into which the exposed PCB needs to
> be developed. They just use a foam brush to brush off the exposed resist.
> Looks like a pretty quick process.
>
> Are you using NaOH in place of the developer? To supplement the developer? Or
> are you using it as a wash to remove the unneeded (exposed) resist after
> development?
>
> And are you using MG Chem. PCBs? (Just want to understand what chems work
> with what boards...)
>
>
> A great idea.
>
> Thanks,
> --
> Al, the usual

I live and work in UK
I use what I refer to as standard PCB board (purchased from Rapid
Electronics) They have a website catalogue you could check for more
details
http://www.rapidelectronics.co.uk
With these boards NaOH is the developer
The unexposed resist can be removed with alcohol (methylated spirits)
but since the heat of a soldering iron strips it as you solder that's
not really needed and it does protect the board from oxidation prior
to soldering
Regards sirkituk
www.geocities.com/sirkituk.htm

LinkBot