Subject:
Re: [gnupic] PCB blues - any suggestions?
From:
"Colin Hunter" ####@####.####
Date:
31 May 2005 04:44:18 +0100
Message-Id: <s29c862b.061@smtp.landcareresearch.co.nz>
Try http://www.megauk.com, go to the 'Printed Circuit Boards' link and at the right hand side there is a link to 'Producing a PCB'. This describes how to do it with their equipment, but in reality the only critical parts you need are LaserStar film, any photoresist coated PCB laminate, UV light source, developer (although sodium hydroxide will, mind your fingers and the concentration) and Ferric Chloride or other etchant. I have used the LaserStar film to successfully produce PCBs with 0.65mm (0.025") lead pitch or tracks between standard SOIC pins (0.127mm or 0.05" pitch). A few tips,
- when you print to LaserStar film, print it in reverse for the top side of a PCB or right way fro the bottom. That way the printing on the film surface ends up against the surface of the PCB avoiding bleeding under the artwork through the thickness of the film. Only critical for very fine artwork, but good practice.
- the developer should not be cold, warm room temperature, 20C to 25C is fine.
- most photoresist has a greenish tinge after exposure, so you can see the exposed areas if you look closely. I normally develop in a plastic food tray, keeping it moving for a couple of minutes and inspect regularly until you are sure you can see clean copper, then rinse thouroughly under a tap.
- the etchant needs to be hand hot, 40C - 50C. I stand the plastic storage bottle in a sink of hot water for half an hour before use. I use the same plastic food tray as above, just rinsed. If you dip the board in for just a few seconds and remove you will clearly see the areas of clear copper which are etching and any underdevoloped areas. Again keep the liquid moving over the surface by gently rocking the container and turning the board regularly or holding the board and swishing around. Should take about 5 minutes. Inspect regularly to avoid over etching. A good fast etch avoids undercutting your artwork. Ferric chloride stains badly, so wear protective clothing, latex gloves and do not spill even on stainless steel.
-once etched, the photoresisted can be wiped off with a little acetone or other solvent. I leav it on if I'm not using a board straight away as it stops tarnishing.
Mega now also sell JetStar film for Epson inkjets. I've never used it, but if it's as good as LaserStar it will work fine. I've used LaserStar in the UK where I sourced it from Farnell and I still source it from Farnell in New Zealand. The Mega site has online shopping and they seem to have distributers worldwide.
Hope this helps,
Colin.
Colin Hunter
R&D Manager
Sirtrack Ltd
Goddard Lane
(Postal : Private Bag 1403)
Havelock North 4230
New Zealand
####@####.####
Ph + 64 6 877 7736
Fax + 64 6 877 5422
Visit our website: http://www.sirtrack.com
>>> "csb" ####@####.#### 31/05/2005 1:56 p.m. >>>
Oops... sent a PM instead of a post. take 2.
-----------------
> I've made at least 12 attempts today, to transfer the artwork onto the
> copper, with no success.
Hmm... I made this board (plus a few others) with the toner-transfer
method: (please excuse the bad focus)
http://rsc-mirror3.netfirms.com/1/elec/board-pics.htm
the exacto marks are there for safety. I found no shorts, but there
were a few specks of copper left in some places.
This is only the my second 2-layer board... that's why the holes aren't
lined up properly. They weren't buffed yet, either. . The 2X13 header
has 0.1" pitch. 99% traces are 16mil (or 12?? can't remember), the others
are 10mil.
> Printer I'm using is an HP 2550L Color Laserjet.
This could be *a* problem.
Here's what I do:
I use a HP LJ 2100, with glossy photo paper (I don't even know what kind
or brand). I print the artwork twice, to have thick lines. Thick enough
so I can feel the traces when I run my fingers over them. I cut out the
artwork, leaving some paper around what I want. I fold the excess paper
around the board so it won't slide when I'm ironing it.
I heat up an old clothes iron (I put it to max for a few minutes) while
I get 2 containers full of ordinary hot water.
I don't know how much time is needed, I just heat up the paper until
its brown everywhere (especially around corners), I normally start to
see some traces through the paper.
Dunk the board in hot water. I let it sit for 10 minutes, and by that
time the paper just peels of. I finish cleaning off the paper in the
second container, using my fingers. Then, I etch the board in warm
ferric chloride. and finally, drill, buff, test, solder, test, etc.
> I'm getting very tempted to give up on artwork transfer entirely, and
> use Eagle to create standardised veroboard (strip board) layouts - an
You might give it a few last tries, just to be sure. It's great to be
able to use 0603, SOIC and SOT packages without having to buy or make
special adapters... plus, a home-made PCB looks a lot better than a
proto-board improvisation!
Good luck!
Christian
---------------------------------------------------------------------
To unsubscribe, e-mail: ####@####.####
For additional commands, e-mail: ####@####.####
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
WARNING: This email and any attachments may be confidential and/or
privileged. They are intended for the addressee only and are not to be read,
used, copied or disseminated by anyone receiving them in error. If you are
not the intended recipient, please notify the sender by return email and
delete this message and any attachments.
The views expressed in this email are those of the sender and do not
necessarily reflect the official views of Landcare Research.
SirTrack
http://www.sirtrack.com
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
