There was a package called Autoboard II from the Great Softwestern Company. The drill information often was a copy of the pad layer (or solder layer) with letter coding beside particular holes and a table was provided with the hole sizes versus the letter coding. Of course the layers had to be thermally stable or expansion due to heat could cause problems on the layout. The first layer on the light table was an accurate grid, and sometimes the fourth lay of just the pads was actually placed on a grid sheet (light blue if I remember) and the photography filtered out the grid.
PCAD 2001 PCB REFERENCE DESIGN REGISTRATION
Layout registration was often aided by special punches that made coded locating holes and then the matching holes in the sheets were fitted on to metal templates.Īll work was done on a light table to facilitate seeing through the layers. Aligning the layers on top of each other needed targets to ensure good registration during photography. The 3 layers consisted of the solder and component sides, silk screen, and sometimes a fourth layer which was only the pads and vias to improve the alignment. The layouts were only done with black tape and required 3 or 4 layers. When the 1973 Yom Kippur war started studies were suspended and I got a job at Elbit Computers (then associated with Control Data Corporation) verifying PCB layout to schematic by going over every trace one for one, a practice I still do to this day. I was working with Dot and Tape while still a student circa 1973, so my experience in fact pre-dated my knowledge of Rubylith that was shown to me by some old-timers once I started work. The photographic process used filters to separate the solder from the component layer.
Dot and Tape was applied with the aid of a fine, and very sharp, Xacto knife.Īn alternate technique mentioned by David Ashton in his comment to Max’s How it was: CAD, CAE, and EDA article was to do the layout on a single layer using two different colored tapes, which meant that alignment was less of an issue. Often the IC pads had the track between them already in place. You could get them in 1:1, 2:1 and 4:1 scale if memory serves. IC and transistor pads were also available pre-made. They could be used for transistors and ICs, but were mostly just for vias. The dots were annular rings made from the same material as the tape and also came with different inner and outer diameters. The tape was self adhesive and black with a kind of crepe texture and was supplied on a roll of about 2″ diameter when fresh and about 1″ when finished. There were several manufacturers although the only one that I remember was Bishop Graphics. The author “Then” (left) and “Now” (right)ĭot and Tape refers to the product used to lay the patterns of tracks and IC/transistor pads on to mylar sheets.
The finished piece of Rubylith was the negative of the layout (and in 1:1 scale) and was placed over the photo resist and then exposed to light. I can only assume that they used some template placed on the Rubylith and exposed the area where the metal would be. I don't really recall how one created IC and transistor pads. I was only introduced to this at the start of my career in 1976 and never actually worked with it. It was really good for earth planes, but I am not sure if double sided layout was possible and certainly a track between IC pins was impossible. The technique required a completely different mindset to today’s “positive” approach. Generating a PCB layout was done in the negative, removing the red film where there was to be track. This consisted of a thin red film stuck to a mylar film. In addition to writing several articles for Circuit Cellar and having ideas published in EDN and Electronic Design, Aubrey wrote Excel by Example: A Microsoft Excel Cookbook for Electronics Engineers (Newnes, 2004).īefore Dot and Tape (see below) there was Rubylith.
Aubrey is engineering manager at Emphatec, a Toronto-based design house of industrial control interfaces and switch-mode power supplies.
PCAD 2001 PCB REFERENCE DESIGN PROFESSIONAL
Editor’s Note: This “How it Was” story is told by Aubrey Kagan, who is a professional engineer with a BSEE from the Technion-Israel Institute of Technology and an MBA from the University of the Witwatersrand.
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