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- Path: sparky!uunet!ogicse!uwm.edu!cs.utexas.edu!ut-emx!ccwf.cc.utexas.edu!wdlee
- From: david@moe.ece.utexas.edu (david lee)
- Newsgroups: sci.electronics
- Subject: Success! Resist Pen Works in HP Plotter!
- Keywords: resist pens, pcb, etching
- Message-ID: <78655@ut-emx.uucp>
- Date: 29 Aug 92 21:17:17 GMT
- Article-I.D.: ut-emx.78655
- Sender: news@ut-emx.uucp
- Reply-To: david@moe.ece.utexas.edu (david lee)
- Organization: The University of Texas at Austin
- Lines: 95
-
- Netones:
- First off, thanks to everyone who replied to my posting
- regarding resist pens in plotters. This is a preliminary,
- but very promising progress report.
-
- Act One, Scene 1:
- David thinks of a neat idea for a circuit, but is too *@#$ lazy
- to draw up a circuit pattern, make a mask, perform the usual
- photolithography, and etch the board.
- So, he says, "Why not just put a resist pen in my plotter, and
- have the silly computer plot my patterns directly on the copper
- clad pc board? Then I can plunk it in some ferric chloride and etch
- it right away!"
- Alas, there are two fundamental problems:
-
- Problem 1: Mechanical Considerations or "Pass me the Duct Tape!"
-
- Just about any pen that you and I find that will protect copper
- throughout the etching process "ain't gonna look like a plotter pen."
- "No problem!", says Dave, "I'll just take an old HP plotter pen,
- yank out the innards and run a drill (or a reamer) through it
- so that my resist pen will slide inside it. I'll adjust the position
- so that the tip of the pen will be held at just the proper level above the
- writing surface."
-
- But little does Dave realize that his HP plotter will not allow big ol'
- pens to be loaded into the pen carousel. "No Problem!", says Dave,
- "I'll use the old HP 7470A plotter. There is NO CAROUSEL anyway, just
- two pen holding bays (one on the left, one on the right) which are
- easily accessable; this plotter works with the cover raised, so there is
- plenty of clearance for my new pen, and the pen holder has a circular
- aperture which allows easy loading and removal of the pen into the
- newly reamed out pen adapter."
- Yes, but what happens when you download the drawing to the plotter,
- and It tries to pick up a pen?! "Well, if you go ahead and fill both the
- left bay and the right bay with pens, and then put our resist pen in the
- plotter's "claw", this will lead to a momentary fit of "plotter spasm"
- but have no fear, it works!
-
- I admit that this is only a temporary solution, since not everyone has
- an HP 7470A plotter. The goal is to fill a drafting pen (which is intended
- for use with plotters) with a suitable resist ink. The following paragraph
- addresses the ink issue.
-
- Problem 2: The Ink Issue or "Pardon me, is that squid ink?"
-
- After the miserable failure of the Sanford Sharpie in the etching tank,
- Dave heads for the campus bookstores, pockets full of clean copper clad
- G-10 fiberglass!
- "Basically, I tried every pen in the University Co-Op Office supplies
- section, every pen in the Art Store on MLK Blvd, and a couple from the
- Campus Supply and Mail Store... Each time writing the name, tip size
- and color of the pen on the freshly cleaned copper clad pcb. I made my way
- back to the EE building and etched the board.....
-
- And in the catagory of 'Best Pen to Withstand Etching of Copper Clad
- Circuit Board Using Ferric Chloride' the winner is....
-
- Manufacturer: Staedtler
- Model: Lumocolor 313 AV
- Ink color: Red
-
- This Pen is available in several sizes; The S size has a 0.4mm tip
- which is PERFECT for running traces *between* the 0.1 inch spacing
- of DIPs. After Etching the boards in warm ferric chloride, every other ink
- showed signs of pitting and undercutting. Only the Staedtler pen was
- absolutely unchanged! So then I tried a longer etch in cool ferric chloride.
- After 20 minutes, examination of the ink under a microscope revealed NO
- pitting, and No dissolving of the ink. Prior to etching, I did gently heat the
- boards with a heat gun to ensure that all the solvent was removed from the
- inks, but I suspect (and will verify tonight) that I might omit this step:
- this ink is awesome. (by the way, after discovering this, I checked my
- e-mail and found a note from a guy at AT&T verifying the performance
- of this pen!) By the way, I am using this pen now to draw boards for
- 100% surface mount. No Drilling! I can have a finished board in 30 min.
- and I don't have to leave my lab!
-
- The Future: The Best of Both Worlds or "Looks like a Borg vessel, Captain."
-
- Several folks have written to me reccomending using drafting pens
- that are designed for use in plotters. Perfect! Let's just get a bottle
- of the Staedtler ink, and fill up such pens! Alas, I called Staedtler's
- Customer Service number, and "no, we don't sell the ink."
- (Insert picture here of David using a hydraulic press to squeeze the
- ink out of a case of pens. :)
- So I e-mailed to a buddy in Munich which is a short train trip from
- Nurnberg, the birthplace of the Lumocolor Pen. He's going to see if
- he can details/samples of the ink, and I'll post the results in
- a (much shorter) letter.
-
- Your Humble Servant,
- David Lee (david@moe.ece.utexas.edu)
-
- Zaphod: "What have you been doing in the car-park Marvin?"
- Marvin: "Parking cars."
-