zotog@SunLab14.essex.ac.uk (Zotos G) (12/06/89)
Form:zotog@uk.ac.essex.servax0 Date:5-12-89 I'm new in this news group so forgive me if this has been asked before. I recently came to a point where I have to produce a good PCB. The easy method of drawing the tracks and the pads with a pen is not very good in compicated or/and fast circuits so I'm after a better but easy method of doing it. Some one helped me by given me a book called "PCB made easy" but fails to give details of what chemicals and sort of things there exist in the market (in U.K.). The usual photographic method of transfering the layout to a film is very undesireable by me as I'm sort of dark-room and equipment. Has any one a good solution for my problem? Is it posible to photocopy the piece of paper with the track layout on a clear plastic film used on overhead projectors and use this as the film plased on the premade positive photoresist PCB and then to expose that in UV light ? Thanks in advance. P.S. Please forgive my English, as I'm Greek.
JTW106@PSUVM.BITNET (Jeff Wolfe) (12/08/89)
In article <2652@servax0.essex.ac.uk>, zotog@SunLab14.essex.ac.uk (Zotos G) says: >I'm new in this news group so forgive me if this has been asked before. >I recently came to a point where I have to produce a good PCB. >The easy method of drawing the tracks and the pads with a pen is not very good >in compicated or/and fast circuits so I'm after a better but easy method of >doing it. Some one helped me by given me a book called "PCB made easy" but >fails to give details of what chemicals and sort of things there exist in the >market (in U.K.). > >The usual photographic method of transfering the layout to a film is very >undesireable by me as I'm sort of dark-room and equipment. >Has any one a good solution for my problem? > >Is it posible to photocopy the piece of paper with the track layout on a >clear plastic film used on overhead projectors and use this as the film >plased on the premade positive photoresist PCB and then to expose that >in UV light ? In my old High School, we used A software program for the PC (the name escapes me at the momnet) that did basic things like Pads and traces, and advanced stuff like autorouting. it even had a module that contained pinouts and specs on about 700 chips or so. The pacakge ran in 512K on an XT, so I assume it would run on an AT or a '386 without any mods. Our output was a laser printed photo positive ( laser transparency ) which was then 'burned' onto a silk screen. From there, we screened our PCBs and etched them with Radio Shack etchant (we found that FFG textile ink worked held up incredibly well in the acid) Towards the end of the year, we experimented with photo etching, but I do not know the exact processes behind it. I do know they used 2 Halogen streetlight bulbs for the light source, and some type of photo-emultion that hardend under the halogen. ------- Jeff Wolfe JTW106@psuvm.psu.edu 114 Lake St. JTW106@psuvm.BITNET Dalton, PA. 18414 "A Computer's efficiency decreases as the urgency of retrieval increases"
john@anasaz.UUCP (John Moore) (12/08/89)
In article <89341.162802JTW106@PSUVM.BITNET> JTW106@PSUVM.BITNET (Jeff Wolfe) writes:
[request for methods of making PCB's deleted]
I have experimented with the following method:
(1) Produce artwork by either drawing it on paper or by generating a
positive from a computer program.
(2) Copy that artwork onto Meadowlake film. This is a rigid, clear film
that will run through laser printers or copiers and is made for
this purpose. It is available from The Meadowlake Corp,
25 Blanchard Drive, P.O. Box 497, Northport, New York 11768
(3) Tape the film to the board with the toner side in contact with the copper
(4) Cover the film with cotton cloth
(5) Heat an iron to about 300 degrees (max setting on my temperature controlled
laundry iron). Heat the board/film by putting the iron on the cloth and
gently moving it around. Press down on the iron to insure
contact between the hot copper and the film. Be patient and take a long
time at this to make sure all of the toner is melted.
(6) Place the hot board with the film still taped to it onto a bed of ice
cubes. Wait for it to cool.
(7) Etch like normal
(8) Scrub off the toner.
I have had trouble with this technique, but the last time I tried it,
adding step 4 above, it worked very well. I reproduced a board that had
lines as small as 10 mils, and was relatively complex. The only problem was
one trace that etched completely away in one place. Not bad for a home
prototype process. The film is relatively expensive at about 1 dollar per
sheet, but a lot cheaper than the photo approach.
I would not recommend this approach for production - only for prototypes
or a small quantity of boards.
This has been discussed recently in Radio Electronics in the Don Lancaster
Hardware Hacker column. Don recommends using a Kroy color press for
more consistency. He also is experimenting with other, cheaper
plastic sheets. Has anyone tried overhead transparency film?
--
John Moore (NJ7E) mcdphx!anasaz!john asuvax!anasaz!john
(602) 861-7607 (day or eve) long palladium, short petroleum
7525 Clearwater Pkwy, Scottsdale, AZ 85253
The 2nd amendment is about military weapons, NOT JUST hunting weapons!woods@robohack.UUCP (Greg A. Woods) (12/15/89)
In article <2652@servax0.essex.ac.uk> zotog@essex.ac.uk writes: > > I'm new in this news group so forgive me if this has been asked before. > I recently came to a point where I have to produce a good PCB. >[...] > Is it posible to photocopy the piece of paper with the track layout on a > clear plastic film used on overhead projectors and use this as the film > plased on the premade positive photoresist PCB and then to expose that > in UV light ? In the December 1989 issue of RADIO-ELECTRONICS, Don Lancaster outlines a rather neat way of making PCB's. He calls it a breakthrough, but I'm not sure I'd go that far, as I'm sure I've heard of the idea before, perhaps using regular artwork, and an image reversing photocopier. Anyway, it goes like this: 1. Using suitable software (he suggests using PostScript directly, for those of us with PostScript printers :-) to design your board in 1:1 scale, as a positive, and reversed (mirror) image. 2. Then print the design using a laser printer onto a polyester based overhead transparency sheet coated with heated mold release agent (Miller Stephenson MS-136). The trick is to use a special thermal transfer toner cartridge. 3. The image may then be transfered directly to a thoroughly cleaned PCB blank with even heat, and hardened by baking. The toner will now act as etch resist, and all that remains is to etch in the usual manner. There are a few more hints and tips in the article, including addresses of suppliers and such. -- Greg A. Woods woods@{robohack,gate,tmsoft,ontmoh,utgpu,gpu.utcs.Toronto.EDU,utorgpu.BITNET} +1 416 443-1734 [h] +1 416 595-5425 [w] VE3-TCP Toronto, Ontario; CANADA
zotog@SunLab6.essex.ac.uk (Zotos G) (12/15/89)
From:zotog@uk.ac.essex.servax0 I would like to thank all who send a reply to my query. I appologise thought, since I wasn't able to reply to any one due to pressure of work. Happy Crhistmas and New Year.
emmo@moncam.co.uk (Dave Emmerson) (12/20/89)
In article <2652@servax0.essex.ac.uk>, zotog@SunLab14.essex.ac.uk (Zotos G) writes: >[] > > Is it posible to photocopy the piece of paper with the track layout on a > clear plastic film used on overhead projectors and use this as the film > plased on the premade positive photoresist PCB and then to expose that > in UV light ? > Very unlikely. Even if you can get enough density in the image area, it will tend to be grainy. Also, you may not get 1:1 copies You need to use 'Ortho Lith' photographic film, in a lith developer, or at least a VERY high-contrast developer. You can handle this in red safelight and dish develop it quite easily. Better, Draw it 2:1 on white paper, with a dense black pen, and get it camera'ed at a specialist PCB photo house for about 15 pounds for a 10 x 8 inch final positive. Even better, buy some of the transfer sheets made for the job, or even the proper black crepe tapes + pads from (say) Maplin Electronics. Most of us start out this way, you'll only get what you pay for. Another possibility, if you have wide (>0.05 inch) tracks, is to use presensitised silk screens, and PRINT your circuit onto plain copper clad board, if you intend to make a few of them. > Thanks in advance. You're very welcome. > > P.S. Please forgive my English, as I'm Greek. Your English is much better than my Greek! Dave E.
oby@munnari.oz.au (David O'Brien) (12/22/89)
In article <317@marvin.moncam.co.uk>, emmo@moncam.co.uk (Dave Emmerson) writes: > In article <2652@servax0.essex.ac.uk>, zotog@SunLab14.essex.ac.uk (Zotos G) writes: > >[] > > > > Is it posible to photocopy the piece of paper with the track layout on a > > clear plastic film used on overhead projectors and use this as the film > > plased on the premade positive photoresist PCB and then to expose that > > in UV light ? > > > > Very unlikely. Even if you can get enough density in the image area, > it will tend to be grainy. Also, you may not get 1:1 copies > > You need to use 'Ortho Lith' photographic film, in a lith developer, or > at least a VERY high-contrast developer. You can handle this in red > safelight and dish develop it quite easily. > > Dave E. I have found these Overhead Projection transparency films produce grainy artwork,and if used develop pourous Photoresist finish. A way to remedy this is to print Two of these grainy artwork sheets at the same time,with the artwork in the same position on the Copier then expose the PCB using these two sheets together. The effect is that the grains of both sheets combine to give a better quality artwork,and the resulting PCB will have clean tracks without the small pits associated with tiny holes in the Photoresist The Quality of the Photocopier is a big factor also. Try it ,it works David Obrien Department of Computer Science University of Melbourne Parkville, Victoria Australia
whit@milton.acs.washington.edu (John Whitmore) (12/22/89)
In article <2952@munnari.oz.au> oby@munnari.oz.au (David O'Brien) writes: >In article <317@marvin.moncam.co.uk>, emmo@moncam.co.uk (Dave Emmerson) writes: >> In article <2652@servax0.essex.ac.uk>, zotog@SunLab14.essex.ac.uk (Zotos G) writes: >> > Is it posible to photocopy the piece of paper with the track layout on a >> > clear plastic film used on overhead projectors and use this ... >> Very unlikely. Even if you can get enough density in the image area, >> it will tend to be grainy. Also, you may not get 1:1 copies >> >> You need to use 'Ortho Lith' photographic film, in a lith developer, or >> at least a VERY high-contrast developer. You can handle this in red >> safelight and dish develop it quite easily. >> Dave E. > > I have found these Overhead Projection transparency films produce > grainy artwork,and if used develop pourous Photoresist finish. > > David O'Brian > University of Melbourne > Australia > The use of high-contrast negatives when contact printing to the final (copper) surface is essential to avoid pinholes. Most people use high-contrast UV sensitive film (Kodak Kodalith film is what the U. of WA. prefers), which is not itself a good Xerox-process substrate. In fact, transparency film is also not a good Xerox-process substrate, and paper prints almost always come out denser (because of the toner powder, which is most sticky to a rough paper surface and only lightly coats a slick smooth plastic film). I had good luck with a two step process: photocopy to exact size on paper, then contact print paper to Kodalith. This requires the UV lamp to shine through the paper onto the Kodalith, which takes about 10 minutes (opposed to 1 minute for Kodalith-to-Kodalith prints), but that is not a tricky step. The Kodalith is then the negative for the photoresist exposure on the copper surface. Of course, the paper is printed-side down; less obviously, the Kodalith film goes coated-side down as well, onto a black surface (in my case). The extra few minutes of exposure time is going to depend on the paper weight and the lamp character, of course; experiment on some test strips to determine the exposure before you use full-size sheets. The Kodalith negatives are developed with xylenol, and are trivial to deal with in comparison with the copper etching baths; they use the same UV illumination for exposure that most resists (like KPR) for PC boards use. I am known for my brilliance, John Whitmore by those who do not know me well.
sjb@dalek.UUCP (Seth J. Bradley) (12/23/89)
What is the best method for making a PC board if you have
a finished PC board as a master (no parts loaded)?
Thanks in advance!
--
Seth J. Bradley UUCP: uunet!{lll-winken|zorch}!dalek!sjb
Internet: lll-winken.llnl.gov!dalek!sjb