Homebrew PCBs

Very interesting. - And good advice for DIY Uv'ers - but...

One thing the Photoploter companies will do - Is still make photplots , cause no inkjet can do 1/8th, - 1./48th of a mil in perfect registration.  I personally have specs between traces that are somewhere between 3 and 4 mil

I can take a hotpot, put it on a board and exposes it for hours, and none of the uv leaks through. 

S800 is out of production, (original ink kit from cannon is $149) I'm not sure how many 8X10 negatives one tank full of ink can print, but that's the cost equivalent of 21 8X10 1/8 mil photplots. 

If the guy had compared the inkjet to a $20,000 photplot with 4000dpi) and came to the same conclusion, I would take his word a little bit more seriously, but claiming an inkjet is on the same plane as a $200,000 ( talking 1um resolution here) , I cant take it to heart , but that said, - I'll probably go inkjet shopping tonight. 

JT
  ----- Original Message ----- 
  From: mpdickens 
  To: Homebrew_PCBs@yahoogroups.com 
  Sent: Friday, July 30, 2004 5:52 PM
  Subject: [Homebrew_PCBs] Inkjet printers, transparencies and UV light...


  A member of another mailing list I am a member of
  found the following in a archive. Further, he tested
  and it worked as advertised:

  I have been dealing with a development effort for a
  circuit that my company is developing. In order to get
  fast turnaround of boards for testing, I needed a way
  to make high quality circuit boards (multilayer) in
  under 8 hours. Cost from commercial board houses for
  24 hour turnaround was in the range of $2000-$3000 per
  design.  In my case, I had to also develope plating
  systems and through-hole activation, fast etching, and
  a hot 20 ton press which I built by converting a shop
  press from harbor freight and adding a temperature
  controller and heating elements.  etc.

  For ATM purposes, 2 sided boards can be made for a
  minimal expense.

  Because many on this list make their own circuit
  boards on occassion (for stepper circuits and camera
  circuits), I thought I would share my experience
  with the group.

  I am currently producing 4, 6 and 8 layer circuit
  boards using equipment now in my basement. Granted my
  basement looks like a chamber of horrors, but I
  suspect this is true for many on this list. Eight mil
  traces and lands are now easily doable and I am
  holding +/- 2 mil registration.

  The greatest roadblock to producing good circuit
  boards was getting good artwork on a transparency.  In
  that regard, I have made several discoveries which are
  not immediately intuitive.

  First, getting really good artwork for the spec above
  is not possible with a laser printer. Phase error
  creeps in and even for printers claiming 1200
  DPI the accuracy just isn't there.  I tested this with
  several models of HP printers including the 2000
  series and the 4000 series.

  In addition, the toner is just not dark enough.  You
  end up having to underexpose the photoresist in order
  to get good removal and then you have a problem with
  undercured photoresist that will not tent over holes
  and whose sides are weak. Further the developing
  process just trashes the underexposed resist.

  I finally decided to try an inkjet printer.  After
  some research looking for a printer that supported
  high resolution in black, I purchased a Canon.
  Initially, I purchased the S300 but it turned out that
  clever marketing made is sound like it supported high
  res black.  In reality, the black was only 600 DPI
  like every other printer...  Not enough resolution.  I
  then tried the S800, which did support 2400 x 1200 DPI
  in color and in Black - the only printer that
  supported high resolution black printing. Experiments
  with
  this printer unfortunately revealed the problem that
  most people have with bubble jets.  The black is
  simply not dark enough in UV.  This despite the fact
  that it was a pigment based ink.

  I did have moderate success stacking tranparenies. 
  This allowed me to increase the exposure time, but
  because only the first transparency was ink down (the
  second had to have a full 5 mil separation for the
  thickness of the first transparency, the edges were
  not very clean.

  I then had a brainstorm, I realized that my UV filters
  for my flourescent lighting were amber.  I decided to
  try other colors... I quickly discovered that yellow
  was just as dark (in UV) as black. Disappointed that
  it was not darker, I began thinking about ways I could
  change the formulation of the ink to include a
  coreactive UV blocking chemical. I started searching
  the net when I discovered that ink fading as a result
  of UV is a real problem for photography. To my
  surprise, my printer already contained an ink that
  was UV blocking.  All I had to do was tell the printer
  that it was printing on high resolution photopaper. 
  This automatically switched cartridges to the PC
  (Photo Cyan) and PM (Photomagenta). Yellow remains the
  same because yellow only fades to yellow.

  In any case, once I did that, I was able to fully
  expose the Photoresist. In comparing a foil blocked
  section and a photo ink exposed section there
  was little difference. Moreover, in testing artwork
  created by a real photoplotter (costing $200,000). 
  There was no difference. The only difference was that
  I settled on "GREEN" as being the color that was best.
  This selected the darkness of yellow in UV and the
  chemical UV blocking in Photo Cyan to produce a very
  dark black in UV and a pretty green in visible... :-)

  Perfect exposures!  That along with unbelievable
  resolution of these printers make for a killer
  combination for producing your own artwork and
  consequently your own circuit boards.

  The bottom line is this. You DON'T want a printer with
  a dark black! Forget whether it is pigment based ink
  or dye based ink. That is all irrelavent, none of them
  are going to be dark enough.

  You want a PHOTO printer with PHOTO ink.  Further ALL
  photoprinters have high resolution in color!  Even the
  cheap ones ($100)! Just make sure a photo ink is
  available either from the manufacturer or for an ink
  refiller. All photo ink is, is ink with UV blocking
  added so the photos you print don't fade.

  What will the photoplotter companies do???

  Armed with this information, there is no reason
  everyone on this list does not do steves killer mod
  for the Philips Vesta camera or the many circuits
  for telescope motorization and tracking.


  Best

  Marvin Dickens
  Alpharetta, Georgia

  =====
  Registered Linux User No. 80253
  If you use linux, get counted at: 
  http://www.linuxcounter.org


              
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