Searching \ for '[OT] developing photosensitive boards' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/index.htm?key=developing+photosensitive
Search entire site for: 'developing photosensitive boards'.

Exact match. Not showing close matches.
PICList Thread
'[OT] developing photosensitive boards'
1999\12\03@072130 by Quentin

flavicon
face
Hi Picsters, it's been a while..

I am experimenting with these kind of boards to see if it is worthwhile
for prototyping.
What can I use for developing and exposing?

Years ago a played with something called Positiv20. It's a spray on
photosensitive (and a pain to use, so don't ask me about it, hehe).
I exposed the board for 30 minutes in the sun and used Caustic Soda to
develop it.

will it work for pre coated boards?

If I have to build an exposure unit, what wattage of lamp must I use?
Will Metal-Hallide lamps work (used for printing plate exposures)?

Oh, and BTW, are the boards positive or negative exposure?

Thanks
Quentin

1999\12\03@075319 by Pavel Korensky

flavicon
face
Hello,

>Years ago a played with something called Positiv20. It's a spray on
>photosensitive (and a pain to use, so don't ask me about it, hehe).
>I exposed the board for 30 minutes in the sun and used Caustic Soda to
>develop it.
>
>will it work for pre coated boards?

Caustic soda is NaOH (natrium hydroxide) ? If so, it will work with
precoated boards, I am using it.

>
>If I have to build an exposure unit, what wattage of lamp must I use?

I am using homebuild unit, made from UV tubes sold in Europe by Conrad and
RS. Those tubes are 8W/230V. I am using two of them.

>Oh, and BTW, are the boards positive or negative exposure?

All boards I saw was positive. But there can be exceptions.

Best regards

PavelK

**************************************************************************
* Pavel KorenskyÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊ *
* DATOR3 LAN Services spol. s r.o.ÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊ *
* Styblova 13, 140 00, Prague 4, Czech Republic      ÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊ *
*ÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊ *
* PGP Key fingerprint:Ê F3 E1 AE BC 34 18 CB A6Ê CC D0 DA 9E 79 03 41 D4 *
*ÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊ *
* SUMMA SCIENTIA - NIHIL SCIREÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊ *
**************************************************************************

1999\12\03@081206 by Graham North

flavicon
face
       >Oh, and BTW, are the boards positive or negative exposure?

       All boards I saw was positive. But there can be exceptions.



       What is the difference between positive and negative exposure?

       What does this mean?

1999\12\03@082034 by Quentin

flavicon
face
Positive, you use a master image exaxtly like you see it. When you
develop, only the areas that were exposed will wash off.
Negative, only the areas that were not exposed will wash of, so you will
have to use a negative master of the image.
Don't worry about it, I don't think I've ever seen negative exposure
stuff for PCB myself, but had to ask to make sure.

Quentin

Graham North wrote:
>
>         >Oh, and BTW, are the boards positive or negative exposure?
>
>         All boards I saw was positive. But there can be exceptions.
>
>         What is the difference between positive and negative exposure?
>
>         What does this mean?

1999\12\03@082244 by Graham North

flavicon
face
Yes, sorry I remember using this stuff at school(!) now.

       ----------
       From:  Quentin [SMTP:spam_OUTqscTakeThisOuTspamICON.CO.ZA]
       Sent:  03 December 1999 13:24
       To:  .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
       Subject:  Re: [OT] developing photosensitive boards

       Positive, you use a master image exaxtly like you see it. When you
       develop, only the areas that were exposed will wash off.
       Negative, only the areas that were not exposed will wash of, so you
will
       have to use a negative master of the image.
       Don't worry about it, I don't think I've ever seen negative exposure
       stuff for PCB myself, but had to ask to make sure.

       Quentin

       Graham North wrote:
       >
       >         >Oh, and BTW, are the boards positive or negative
exposure?
       >
       >         All boards I saw was positive. But there can be
exceptions.
       >
       >         What is the difference between positive and negative
exposure?
       >
       >         What does this mean?

1999\12\03@151859 by Brian Aase

flavicon
face
Back in my PCB-making days, I used photoresist coatings
exclusively.  If everything is done just right, you get excellent
resolution and repeatability.  (If not, you get a lot of frustration and
wasted materials.)

In my experience (which is a few years old) there were two
fundamental types of photoresist: Negative-acting (Kodak and
Dynachem), and Positive-acting (Shipley).  These resists are
marketed under various names, so it's sometimes hard to tell
which brand you have. DuPont also makes a laminated-film
type of resist, but that was always beyond my budget.

In general, the negative-acting resists use some type of
hydrocarbon solvent as a developer, such as Xylene.  The positive
ones use variations of sodium hydroxide solutions, as the caustic
soda you mentioned.  Development is kind of an all-or-nothing
process.  The idea is to dissolve the unwanted resist, while leaving
the PCB resist pattern intact.  Both Shipley and Dynachem resists
were colored so you could get a clue when to pull the board out of
the developing solution.

Exposure time is not critical.  To get your process "right on", go to
the camera store and pick up one of those little 14-step gray scale
guides, and expose a few small boards with it using various times
like 5, 10, 15 minutes.  Pick the time that results in the bottom 1/3
of the scale leaving solid resist, and the top 1/3 being cleanly
washed away.  For Kodak KPR4 resist and a No. 2 photoflood bulb
at a distance of 10" from the PCB, six minutes of exposure was
just right for me.  Shipley resist wanted much more time, maybe
20 minutes or so.

Tip: I found it important to use as much of a point-source lamp as
possible for best resolution.  Those exposure frames with banks of
blacklights always blurred things out too much when I tried them.
If you're really serious, you can get *great* results from a carbon
arc lamp.

The final trick is to get an exposure frame that keeps the PCB in
*intimate* contact with the film!  (Yes, this is crucial.)  A vacuum-
back frame will give you perfect results every time, if you can afford
one.  I found those little wood-and-glass things with a spring on the
back never really did an adequate job for me.

email me if you want further useless info  ;-)

Brian Aase

{Quote hidden}

1999\12\06@023606 by ruben

flavicon
face
CAD a layout with horizontal lines of the linewidth You use under
each other, perhaps 15cm wide. Make 10 vertical lines (of the same
width) spaced 1cm apart. Starting from left, write the numbers 15,
14, 13...7, 6, 5 under the vertical lines. Expose Your PCB with this
layout as You normally would except that You start with only the
vertical line numbered 15 visible and the others covered with some UV
blocking material (a non etched PCB perhaps). For every minute that
passes You slide the cover to the right exposing the next vertical
line. When the last vertical line is visible expose for 5 more
minutes. The leftmost part of the PCB is now exposed 15 minutes and
the rightmost part is exposed 5 minutes. Now develop your board and
etch it as You usually would do. At the resulting PCB You should be
able to see what exposure time is the best to use.

Depending on the materials of the film, the type of photoresist and
the type of lamp You use 15 to 5 minutes may not be the best, just
add vertical lines and increase exposure time if You need more.

{Quote hidden}

==============================
Ruben Jvnsson
AB Liros Elektronik
Box 9124, 200 39 Malmv, Sweden
TEL INT +4640 142078
FAX INT +4640 947388
rubenspamKILLspam2.sbbs.se
==============================

More... (looser matching)
- Last day of these posts
- In 1999 , 2000 only
- Today
- New search...