Photo-etch light source?

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!

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
>

> 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

Hi Usual Suspect, you wrote:

>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.

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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...
> > 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
>

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.

On Thu, 8 Mar 2007 19:18:54 -0800, saxum@webtv.net (Grostle News)
wrote:

>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.

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

On Fri, 09 Mar 2007 14:53:15 +1100, Lionel <usenet@imagenoir.com>
wrote:

>On Thu, 8 Mar 2007 19:18:54 -0800, saxum@webtv.net (Grostle News)
>wrote:
>
>>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.

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!

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

Time depends on strength of developer, temperature and speed of the
resist.

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

> > > 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?

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