From: david@moe.ece.utexas.edu (david lee) Subject: Success! Resist Pen Works in HP Plotter! Keywords: resist pens, pcb, etching Date: 29 Aug 92 21:17:17 GMT Reply-To: david@moe.ece.utexas.edu (david lee) Organization: The University of Texas at Austin 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." From: magore@icr2.uwaterloo.ca (Mike Gore) Subject: Re: Resist Pens in Plotters Organization: University of Waterloo Date: Thu, 3 Sep 1992 03:23:36 GMT In article <78433@ut-emx.uucp> david@moe.ece.utexas.edu (david lee) writes: >Netfolks: > I have been using permanent markers in my plotter, writing directly >onto copper pc boards, trying to circumvent the photo-lithographic steps. -For pens I use: Staedtler Lumocolor 313 Permanent pens. -For etchant I use: Ammonium Persulphate (very clean to work with and works well with the pens listed here) -For Tin plate I use solution from GC electronics. cat# 22-228-A (works great!) -For very fine detail I buy Micro Pigma (non water-proof) remove the ink filler and replace with one from a steadtler permanant (see above). Run the pin dry after removing the filler and before adding the filler from the steadtler. You have to cut the very back off the steadtler to remove it. Both pens use the same size fillers, just flip them around and punch them back into the point. The Micro Pigma pin come apart without damage - these pens come in VERY small sizes, the 005 pens tend to clog if you leave the steadtler filler in them for a long time so leave the final swap to just before a plot. I have been able to make surface mount at .025 spacing just fine, or for example do traces between a pad without problems! - Suggestion for those trying this - do the plot at least twice. - Use 0000 grade steel wool and clean the board to a polish just moments before the plot - wipe clean with a soft clean rag ( *** don't omit these steps *** ) - Heat the Ammonium persulphate to about 60C, the easy way is to mix only what you need just before using - ex: I often use 1/4 cup AP and 3/4 cup of hot water (ratio varies, so check your labels) - Float the plastic tray in hot water for the etch. * Read the safety instructions, where gloves, use good ventilation * - After etch use 0000 grade steal wool and clean the board to a polish just moments before the plating process but wash with clean water to clean. ( *** don't omit these steps *** ) Using a solvent to remove the ink will not remove the oxide that inhibits a good plate so even if you do use solvent use the steel wool _after_ the board dries - ex: don't risk the chance of a spark - keep your solvents in a safe place, etc... (I have made a few dozen boards in this way, so far the results are very very good ) Good Luck! # Mike Gore, Technical Support, Institute for Computer Research # Internet: magore@watserv1.waterloo.edu or magore@watserv1.uwaterloo.ca # UUCP: uunet!math!watserv1!magore # These ideas/concepts do *not* imply views held by the University of Waterloo. From: agodwin@acorn.co.uk (Adrian Godwin) Subject: Re: Success! Resist Pen Works in HP Plotter! Keywords: resist pens, pcb, etching Date: 4 Sep 92 08:46:02 GMT Organization: Acorn Computers Ltd, Cambridge, UK In article <78655@ut-emx.uucp> david@moe.ece.utexas.edu (david lee) writes: > >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 .. and also in several shapes, including some that are made to fit HP plotters ! After noticing that the plotter pens I was disembowelling to fit Lumocolor tips into were also made by Staedtler, I went hunting for an OHP plotter pen from the same company. They make : 31HP07K-2 0.7mm, short pen for 7220 and similar 31HP03K-2 0.3mm, ditto 31HP03L-2 0.3mm, long pen for Draftmaster etc. (-2 indicates red ink) I tried the 31HP03K-2 last night and it appears to be exactly the same ink as the 313 AV. It certainly works as well ! The tip on this pen is similar to that on the 'Fine' (318 AV ?) Lumocolor, and suffers slightly from poor ink transfer - fine lines appear in the resist, and it leaks slightly. I had this problem with all the Lumocolor pens I tried, to a greater or lesser degree. It certainly appears to be worthwhile plotting the tracks twice (or perhaps using a very slow plotting speed) as another writer suggested. -adrian -- Adrian Godwin : agodwin@acorn.co.uk : adrian@fangorn.demon.co.uk : g7hwn@gb7khw ObDisclaimer : I believe this rubbish .. don't imagine that anyone else does.