Homebrew PCBs

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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