Homebrew PCBs

Hello,

I just got two 8W blacklight tubes, and have build some kind of
exposure stand. I put the tubes on the bottom, facing up, and 7 cm
above there is a transparent 0.5mm crystal. On top of it, it will be
the PCB, facing down, with some weigth on it. Do you think this will work?

I just find some problem with this approach:
- No reflector, is it really necesary?
- Maybe 7cm is too close to the blacklight tubes... I really don't
know if it will be done in 2 minutes, or 6. But anyway, is it too close?

Thank you

----- Original Message ----- 

From: "patroclus04" <patroclus04@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Thursday, April 06, 2006 8:54 AM
Subject: [Homebrew_PCBs] Will this work? (my first photo-resist PCB)


> Hello,
>
> I just got two 8W blacklight tubes, and have build some kind of
> exposure stand. I put the tubes on the bottom, facing up, and 7 cm
> above there is a transparent 0.5mm crystal. On top of it, it will be
> the PCB, facing down, with some weigth on it. Do you think this will work?
>
> I just find some problem with this approach:
> - No reflector, is it really necesary?
> - Maybe 7cm is too close to the blacklight tubes... I really don't
> know if it will be done in 2 minutes, or 6. But anyway, is it too close?

It should work OK, I have a similar arrangement that works very well. My 
distance between the glass and the tubes is greater (13 cm, IIRC). I would 
just try it and see if it works. 6 mins would be a good starting point, but 
you really need to use a test pattern and move a mask along every minute, to 
get it working optimally.

Leon 

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patroclus04 wrote:
> Hello,
> 
> I just got two 8W blacklight tubes, and have build some kind of
> exposure stand. I put the tubes on the bottom, facing up, and 7 cm
> above there is a transparent 0.5mm crystal. On top of it, it will be
> the PCB, facing down, with some weigth on it. Do you think this will work?
> 
> I just find some problem with this approach:
> - No reflector, is it really necesary?
> - Maybe 7cm is too close to the blacklight tubes... I really don't
> know if it will be done in 2 minutes, or 6. But anyway, is it too close?

Put a sheet of white paper over the glass and see how bright it glows in
the dark. If you can see bright bands because of the tubes being too close
to the glass, you should put in more tubes, or move them further away. Four
tubes 5-10cm away from the glass should be ok. Two widely separated tubes 5cm
away probably won't be good. Use a diffuse silvery surface behind the tubes
to make the thing a bit more efficient.

When I started off making PCBs, I used photoresist PCBs from MG Chemicals.
I didn't need blacklight tubes for the process to work, a single ordinary
neon tube held about 7-8" over the PCB worked perfectly.  I printed my
circuits onto overhead transparencies.  Neons are cheaper than blacklight
and available in all sorts of sizes.

Robert
:)



-----Message d'origine-----
De : Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com] De
la part de Leon Heller
Envoyé : avril 6 2006 04:03
À : Homebrew_PCBs@yahoogroups.com
Objet : Re: [Homebrew_PCBs] Will this work? (my first photo-resist PCB)


It should work OK, I have a similar arrangement that works very well. My 
distance between the glass and the tubes is greater (13 cm, IIRC). I would 
just try it and see if it works. 6 mins would be a good starting point, but 
you really need to use a test pattern and move a mask along every minute, to

get it working optimally.

Leon 

---
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to maintain up to date anti virus software on the device that you are
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----- Original Message ----- 

From: "Robert Hedan" <robert.hedan@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Thursday, April 06, 2006 4:23 PM
Subject: [Homebrew_PCBs] RE : Will this work? (my first photo-resist PCB)


When I started off making PCBs, I used photoresist PCBs from MG Chemicals.
I didn't need blacklight tubes for the process to work, a single ordinary
neon tube held about 7-8" over the PCB worked perfectly.  I printed my
circuits onto overhead transparencies.  Neons are cheaper than blacklight
and available in all sorts of sizes.

Don't you mean fluorescent tubes?

Leon
--
Leon Heller, G1HSM
leon.heller@...
http://www.geocities.com/leon_heller
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Uh, yeah, we call them neons, but they are fluorescents.  The one I have now
is Globe F15T8D 15W.

I saw an entire unit; single lamp, casing, power switch, cord and ballast at
a local dollar store for something like $5.

Robert
:)



-----Message d'origine-----
De : Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com] De
la part de Leon Heller
Envoyé : avril 6 2006 11:34
À : Homebrew_PCBs@yahoogroups.com
Objet : Re: [Homebrew_PCBs] RE : Will this work? (my first photo-resist PCB)


Don't you mean fluorescent tubes?

Leon
--
Leon Heller, G1HSM
leon.heller@... http://www.geocities.com/leon_heller
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> Neons are cheaper than blacklight
> and available in all sorts of sizes.
>

Prefer cardinal tetra's myself.

What is it with people these days, if it lights up its a bloody neon!

Every car magazine and ebay auction has 'neons' that have never been
near the gas!

led's, cold cathode flourescent and whatever else all sold as neon!

Oh its getting to me it really is, I'm off to find a nice dark quite
room and have a little nap.......

Here's what I will be using.

http://img218.imageshack.us/img218/4043/box19ks.jpg

it is not finished yet, but still. I can't change the distance between
tubes and glass once finished, so I'll have a try.
the two tubes will be separated a about 2 cm from each other, and both
of them at 7-8 cm from the PCB. Each one is 6W, so maybe they are not
too close.. I hope! :)

On the other hand, I will put a reflecting surface below the tubes,
but I did not plan to close the sides of the "box". As it is quite
close, I hope no reflector is needed, as I find no easy way of adding
them.
I'll try 5 minutes, then 8 minutes, with 2 different little boards,
and see which one comes out better.

I will be using metasilicate (I hope this is how it's called in
English) instead of NaOH for developing. Do you guys know if I can use
the solution several times, or have to throw away each time??
About 2 minutes for developing would be a good starting point??

thanks for your help!

----- Original Message ----- 

From: "patroclus04" <patroclus04@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, April 07, 2006 2:32 PM
Subject: [Homebrew_PCBs] Re: Will this work? (my first photo-resist PCB)


>
>
> Here's what I will be using.
>
> http://img218.imageshack.us/img218/4043/box19ks.jpg
>
> it is not finished yet, but still. I can't change the distance between
> tubes and glass once finished, so I'll have a try.
> the two tubes will be separated a about 2 cm from each other, and both
> of them at 7-8 cm from the PCB. Each one is 6W, so maybe they are not
> too close.. I hope! :)

The distance is a compromise, you need them close enough to get a short 
exposure and far enough away to get some collimation effect.

Mine is made from three pieces of MDF (fibreboard) strengthened in the 
corners with 2 cm square wood and two lengths of wood to support the glass 
above the tubes,which are mounted on the base like you have done. I have 
enough space to add a third tube.

>
> On the other hand, I will put a reflecting surface below the tubes,
> but I did not plan to close the sides of the "box". As it is quite
> close, I hope no reflector is needed, as I find no easy way of adding
> them.
> I'll try 5 minutes, then 8 minutes, with 2 different little boards,
> and see which one comes out better.
>
> I will be using metasilicate (I hope this is how it's called in
> English) instead of NaOH for developing. Do you guys know if I can use
> the solution several times, or have to throw away each time??
> About 2 minutes for developing would be a good starting point??

You should see the resist coming off, as it is coloured with a dye. Just 
leave it a little longer than it takes for all the dye to disappear.

Leon


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About your "box", are the sides closed? you use any reflector?

I got metasilicate, in powder, to prepare 1 litre solution, but it is
suppose to last for 8 hours only. I can't spend more than $3 (in
euros, I live in Spain)  everytime I need to develop a PCB, and also,
because that litre of solution is capable of developing 20 boards. How
can I get rid of this??

----- Original Message ----- 

From: "patroclus04" <patroclus04@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, April 07, 2006 8:14 PM
Subject: [Homebrew_PCBs] Re: Will this work? (my first photo-resist PCB)


>
> About your "box", are the sides closed? you use any reflector?

Sides are closed, but not the ends. No reflector.

>
> I got metasilicate, in powder, to prepare 1 litre solution, but it is
> suppose to last for 8 hours only. I can't spend more than $3 (in
> euros, I live in Spain)  everytime I need to develop a PCB, and also,
> because that litre of solution is capable of developing 20 boards. How
> can I get rid of this??

That's why I use NaOH. It's so cheap that I don't bother to re-use it, 
although it will last a long time. I make up a litre at a time (10 g NaOH) 
and use just enough to cover the board in a small container, then throw it 
away.

Give my regards to Achilles,

Leon
--
Leon Heller, G1HSM
leon.heller@...
http://www.geocities.com/leon_heller 

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Hello patroclus04 and all groupies,

  Friday, April 7, 2006, 9:14:43 PM, ti rece:


> About your "box", are the sides closed? you use any reflector?

> I got metasilicate, in powder, to prepare 1 litre solution, but it is
> suppose to last for 8 hours only. I can't spend more than $3 (in
> euros, I live in Spain)  everytime I need to develop a PCB, and also,
> because that litre of solution is capable of developing 20 boards. How
> can I get rid of this?? 

  Just  uploaded  3 photos in Files section so that anyone interrested
  can  see  the  exposure  un  it that I use. It consists 2 Philips TL
  20W/09N tubes with the reflectorc made from 110mm PVC tube cutted in
  half  and  with reflective foil sticked inside. The distance between
  tubes  is  110mm  and the height from glas covered PCB/Film combo is
  approx 200mm. Exposure time 5 minutes. Glas used is ordinary 6mm.

-- 
 Best regards,
 Zoran A. Scepanovic
 zastos@...
 
*********
A carelessly planned project takes three longer to complete than expected;
  a carefully planned project takes only twice as long. 
*********

Please be advised what was said may be absolutely wrong, and hereby this disclaimer follows.  I reserve the right to be wrong and admit it in front of the entire world.



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