Hi Byron,
It sounds like you are having a lot of fun!
I have used the sun to expose the photo resist on my boards for years ( since 1969 actually ) and I consistently get perfect boards with .010 traces between pins using a 30 second exposure time.
Lately I have been using tracing paper with a HP 5L with very good results. I have to tape it to a sheet of regular paper to get it to feed right but it is fast simple and much cheaper than transparencies.
Jack
----- Original Message -----
From: starsnstripes_2003
To: Homebrew_PCBs@yahoogroups.com
Sent: Saturday, July 19, 2003 8:49 PM
Subject: [Homebrew_PCBs] Poor Man's Drill Press
Greetings! Thanks to all you guys posting the valuable info!
I just wandered in here a few days ago, and was looking for some
helpful hints on starting out with homebrew PCBs. I have enjoyed the
posts here very much!
I'm the type of DIY person that believes in KISS (Keep it simple,
stupid), so I am using all locally available supplies. (except drill
bits and PCB stock that I ordered).
The methods I used are surely not optimal, but extremely simple and
readily available.
I just made my first successful PCB at home using the most basic
items and thought I'd share my limited experiences, and maybe get
some pointers (Especially on Etchant).
Drill:
My new but cheap drill press from Harbor Freight had so much wobble
in the chuck it snapped the .8 mm carbide drill immediately. Upon
inspection, I found the step pulleys were not bored properly,
causing the wobble.
I therefore needed a way to drill some boards with my Dremel. (I
don't have the drill-press stand attachment yet.)
I already knew that Carbide drills were very long-lasting, but
extremely brittle.
The slightest lateral movement or wobble will break these tiny
drills.
So I needed a way to improve my somewhat unsteady hand.
Here's what I found worked to steady the Dremel 395 enough to drill
with Carbide Drills.
I figured that taking the weight and alignment away from hand
control might help.
I'm a not-so-good guitarist, but I had a microphone stand with a
boom arm attached. (Any over-hanging support can be used. Light
fixture maybe?)
I suspended my Dremel from my boom by using 3 ordinary rubber-bands
such that it hung straight over my board and about an inch away.
The Dremel has a wire loop at the tail, so I just used it with a
half wrap around the cord to make it hang straight.
This allowed me to concentrate on a slight downward movement of the
tool using only 2 fingers with a very light touch.
This transfers the alignment and load of the tool to the Boom and
gravity.
I drilled about 60 holes using a .8 mm carbide resharpened bits from
Drill-Bit City http://shop.store.yahoo.com/drillcity/. (These bits
have a .125" shank and are reasonable price.)
I know that I will need a more reliable solution if I continue to
make boards, but I thought I'd pass on this temporary solution for
those that are just doing a few boards and don't want to invest in
more equipment.
Board: GC #21-243 1 oz. grade FR4 Positive Resist. Advertised as GC-
603 at Abra Electronics http://www.abra-electronics.com (I believe
that is a MG part number? Maybe they changed suppliers?)
Circuit Layout: Eagle w/12 mil traces.
I used Paint Shop Pro to Panelize these small 1" x 1" circuits, but
had to put the holes in manually, because my Eagle 4.03 didn't do
that when exporting the image. (It does it when printing direct,
though).
Transfer Method: Canon F80 Ink-Jet printer on Office Depot Ink-Jet
Transparencies.
Printed at 1200 dpi. 2 Passes on the same sheet to darken image.
Very clean looking results!
May try single pass later.
Exposure: Mid-day Texas direct sunlight.
Test exposure used 1" strip with foil "slider". Test was 30 sec. to
3 minutes in 30 sec intervals.
Results showed all (even 30 sec.) worked about the same, so I tried
one at about 35 sec. and one at 1 minute.
The 1 Minute board over-exposed I think, because I got some pitting
in the traces. The 35 sec. board came out pretty nice on the 12 mil
traces and would likely have done 5 mil if exposure was adjusted a
little better.
As soon as it arrives, I will be trying a surplus Derma-Spec lamp
($6.95) that has a small 6" Blacklight BLB tube and 1-Min. timer in
it. I ordered 2, and plan on modifying the 1 min. timer circuit to
suit the exposure time needed. Maybe this will offer a little more
control of the exposure.
Developer: Lewis Red Devil Lye purchased from Albertson's July,
2003. Mixed at approx 6g per Liter?
I calculated it to be 1 Tsp per Quart. Used Lowe's 1" foam brush
lightly. Worked great.
Etchant: I'm using 34% HCL from Lowe's Garden Center and 3% Hydrogen
Peroxide from Albertson's mixed 1:1.
I used no water, because most recipes call for stronger Peroxide.
This solution seems to work if you use it right away.
If you let it stand for a while it seems to be "die" or slow down.
Why is this?
I Really could use some input on this Etchant mix. Does the HCL/H2O2
mix always die soon after mixing?
Does it only work while the solution is still bubbling?
Other Supplies: 3 Cheap plastic freezer containers for
Developer/Etchant/Water. Homemade tongs fashioned from 2 plastic
forks.
Any input/comments would be much appreciated!
Regards to all,
Byron
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