Printed circuit board fabrication
 

"Dave Plowman (News)" wrote in message
...
In article ,
TonyL wrote:
You do need to use a reasonably accurate combination of level and time
though - like any exposure. And the coated board is rather expensive
to experiment with.


I would guess for calibration....a timer and a 1 cm by 10 cm strip of
coated board with sections exposed for various time periods.

Yes - with a light box which I have. But with the sun it would vary
according to time of day and year - even on a cloudless day?

IIRC, some ovens with exposed elements can be used too.

Wouldn't that be IR. ?

Printed circuit board fabrication
 

In article ,
Arny Krueger wrote:
You do need to use a reasonably accurate combination of level and time
though - like any exposure.

Not like *any* exposure. The "negative" generally is line art, thick
black over transparent film. Very, very high contrast. The "film" is
designed to be very tolerant of small exposures to light. It wants to
produce a high contrast "picture".

Oh it's not as critical as a photo - but you still need some care. I'd
have no idea how long it would need in the various flavours of sunlight we
get in the UK.

--
*If all is not lost, where the hell is it?

Dave Plowman London SW
To e-mail, change noise into sound.

Printed circuit board fabrication
 

Don Pearce wrote:

Radiospares used to do UV sensitive double sided board. It was
covered with black plastic, which you could use as a resist if you
fancied just cutting the pattern with a scalpel. No idea if they
still stock it.


Just checked - they do.


Thnks Don.

Printed circuit board fabrication
 

David Looser wrote:
"TonyL" wrote in message
...
Dave Plowman (News) wrote:

You do need to use a reasonably accurate combination of level and
time though - like any exposure. And the coated board is rather
expensive to experiment with.


I would guess for calibration....a timer and a 1 cm by 10 cm strip of
coated board with sections exposed for various time periods.


Not a lot of use with sunshine, as the UV content varies from
minute-to-minute depending on cloud cover.


Quite. It is going to be a UV box, either home made or bought.

Printed circuit board fabrication
 

On Sun, 8 Feb 2009 10:38:19 -0000, "TonyL"
wrote:

Don Pearce wrote:

Radiospares used to do UV sensitive double sided board. It was
covered with black plastic, which you could use as a resist if you
fancied just cutting the pattern with a scalpel. No idea if they
still stock it.


Just checked - they do.


Thnks Don.


Welcome - just to be clear, I meant the black plastic could be a photo
resist, not an etch resist.

d

Printed circuit board fabrication
 

In article ,
TonyL wrote:
Quite. It is going to be a UV box, either home made or bought.

A selection of tubes he-

http://www.tlc-direct.co.uk/Main_Ind...s_2/index.html

Some fittings that might do he-

http://www.tlc-direct.co.uk/Main_Ind...lar/index.html

Or do a search for a twin ballast for the tube size you want.

A small toolbox with lid could be a suitable case, with a glass platform
fitted and sponge in the lid to press the transparency and board to the
glass.

Paint the inside white for maximum reflection - you might have to make up
a reflector shaped sort of ^^ in cross section.

They are quite pricey to buy due to low volumes of production - although I
haven't really looked on Ebay, etc. My guess is you could make one at a
parts cost of approx half of buying one.

Remember to print the transparency mirror image as you want the 'print'
side in contact with the work to avoid refraction effects.

--
Is the hardness of the butter proportional to the softness of the bread?*

Dave Plowman London SW
To e-mail, change noise into sound.

Printed circuit board fabrication
 

On Sun, 08 Feb 2009 11:43:28 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
TonyL wrote:
Quite. It is going to be a UV box, either home made or bought.

A selection of tubes he-

http://www.tlc-direct.co.uk/Main_Ind...s_2/index.html

Some fittings that might do he-

http://www.tlc-direct.co.uk/Main_Ind...lar/index.html

Or do a search for a twin ballast for the tube size you want.

A small toolbox with lid could be a suitable case, with a glass platform
fitted and sponge in the lid to press the transparency and board to the
glass.

Paint the inside white for maximum reflection - you might have to make up
a reflector shaped sort of ^^ in cross section.

They are quite pricey to buy due to low volumes of production - although I
haven't really looked on Ebay, etc. My guess is you could make one at a
parts cost of approx half of buying one.

Remember to print the transparency mirror image as you want the 'print'
side in contact with the work to avoid refraction effects.

I made one years ago for the cost of four fluorescent tubes, holders
and ballasts. The box was wood, and the glass was a spare pane from
the greenhouse.

Incidentally I took care of registration of the two sides by stacking
the two artworks on top of the board, drilling a pair of holes at
diagonally opposite corners and eyeballing the holes to line things
up.

d

Printed circuit board fabrication
 

Don Pearce wrote:
On Sun, 08 Feb 2009 11:43:28 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
TonyL wrote:
Quite. It is going to be a UV box, either home made or bought.

A selection of tubes he-

http://www.tlc-direct.co.uk/Main_Ind...s_2/index.html

Some fittings that might do he-

http://www.tlc-direct.co.uk/Main_Ind...lar/index.html

Or do a search for a twin ballast for the tube size you want.

A small toolbox with lid could be a suitable case, with a glass
platform fitted and sponge in the lid to press the transparency and
board to the glass.

Paint the inside white for maximum reflection - you might have to
make up a reflector shaped sort of ^^ in cross section.

They are quite pricey to buy due to low volumes of production -
although I haven't really looked on Ebay, etc. My guess is you could
make one at a parts cost of approx half of buying one.

Remember to print the transparency mirror image as you want the
'print' side in contact with the work to avoid refraction effects.

I made one years ago for the cost of four fluorescent tubes, holders
and ballasts. The box was wood, and the glass was a spare pane from
the greenhouse.

Incidentally I took care of registration of the two sides by stacking
the two artworks on top of the board, drilling a pair of holes at
diagonally opposite corners and eyeballing the holes to line things
up.

d

Hints&tips noted. Thanks all.