Back in the 70s people used blue and red tape taped out on the same side of the same piece of plastic sheet, typically at 2:1 scale. The blue was the top copper, the red was the bottom copper (or vv?!). It was projected through coloured filters onto the light-sensitive etch resist.
Four layer boards? No. Poured copper areas? Tedious. Lifting a blue track layed under a red track?
If you get carbide-ball-tipped dental burrs from a dental supply house, you can even use them free-hand in your Dremel. The shanks are steel and handle plenty of side load for carving... about anything short of dropping the Dremel tip-down.
The tips themselves will last forever; the only ones I've lost were by (ahem!) dropping the Dremel. I made a simple metal sleeve to slip over the end of the Dremel to protect the tip when not in use, and that's pretty much solved the problem.
Dental burrs are fine for drilling use as well, but you can only do one board at a time due to the tapered shank leading to the ball tip.
Best regards,
Bob Masta DAQARTA v7.60 Data AcQuisition And Real-Time Analysis
Or, more often, reduced 2:1 to B+W film to make the boards. The PCB resist (usually KPR) was UV sensitive.
I didn't like the color stuff. It was hard to "edit" a layout, and the color separation photography didn't work well. We could do tricks to burn assembly and fab drawings when each layer was its own mylar, which didn't work with colored tape.
Sure, we did those.
Cut from Rubylith with an x-acto. That was as fast as CAD.
Lorry Ray could make a ground plane, or power pours, from the padmaster mylar, using some photographic tricks.
Early ICs were designed with Rubylith and x-acto knives. People didn't have metric rulers handy, so someone decided that there were 25 mm to the inch.
That's why we had a sheet of mylar for each trace layer.
The real annoyance of hand-taped PCB layout was checking. Checking clearances and connectivity of a serious layout would take two people two days. Now it takes seconds.
I still draw a lot, mechanical sketches and schematics. It's much more intuitive to me than using a screen. I have minions who CAD my stuff for me.
-- John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Under $1 each on ebay.
-- John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Free for me. My partner's daughter and her husband are dentists.
I agree absolutely about hand drawn, its perfect free form and so user friendly. But no minions I'm afraid :-(
We go to the movie theater about once or twice a month. Movie theaters aren't exactly going out of business here. In fact, new ones are opening relatively often. As far as "abusive prices" go, I don't consider $7 for a few hours of entertainment to be too bad.
I can't seem to sleep. Good time for a rant.
At the risk of starting a nostalgia thread, we didn't use the different colored tape method. Everything was done 2:1 or preferably
4:1. We used mylar sheets and an Xacto knife, Brady tape "donuts" for pads, Brady black tape for traces, red rubylith for ground planes and solder masks. Red photo opaque paint for touchup. I was marked for an early death when I used one of draftings sacred Xacto knives to cut traces on a PCB board. They had to be very sharp to work well for working with rubylith.I still have my seriously expensive E size 0.1" mylar alignment grid somewhere. However, the glue on the tape and pads would dry out after a few years. Most of my early layouts and layout supplies have long ago dried out and were thrown out. The lifetime of these original layouts sometimes defined the lifetime of the product as making changes to a layout using a photographed enlargement or the negatives or a PCB was not easy.
While computer layout to Gerber plots were common, I found myself making changes and corrections to old PCB layouts using these methods well into the 1990's. Old tech dies hard: "How It Was: PCB Layout from Rubylith to Dot and Tape to CAD"
In RF, it was common for the design engineers to participate directly in the layout process. Most managers didn't want to waste expensive engineering time on "menial" tasks, such as PCB layout and checking. However, those with an interest in getting things right the first time had other ideas and allowed direct involvement. For RF boards I would locate the major RF components on a PCB, mark the location of grounding holes, and make sure the RF path was reasonably straight, didn't loop back on itself, devices were properly bypassed, and often supplied the prototype PCB to the layout person. Just handing them the schematic and parts list was an invitation to start over from scratch. In honor of my involvement in this system, the drafting department presented me with a "Change Everything" rubber stamp.
Yes, although getting them right was difficult. Without computerized rule checking, it was easy to create problems and not find them until the prototype was built.
Not really, at least for RF. The real PCB would be fair accurate clone of the hand made prototype board. The ground plane was always on top of the PCB. Where the prototype used routed clearances for non-grounded areas, the PCB layout used rubylith with those areas cut out with a swivel knife compass. It was a bit tedious, but not very difficult. The hard part was reconnecting the "islands" of ground with Brady black tape.
I tried to find examples of such layouts using Google image search and found nothing. I'll see if I dig out some old photos.
Yep. That's why we didn't use that method. Instead, we had multiple layers of transparent mylar, with the layers aligned by punched holes with "pins" and targets. With a 2 layer PCB, there would be 2 sheets for the traces, and one each for the solder mask and silk screen. For digital PCB's, we would use 3 layers. There would be a "pad master", which was used for both the component and circuit side pads. The other two sheets were just the traces for the component and circuit sides. When photographed and reduced, the pad master was combined with the traces to form the final image. The component outlines (silk screen) were done by hand with an elevated template and india ink. Every time components were moved due to a design change, the silk screen had to be redone from scratch as making changes to the original were difficult.
With luck everything would fit. With my luck, there could be duplicate reference designators, test points under parts, traces shorting to component cases, interchanged circuit and components side copper, and a myriad of other layout mistakes that never seemed to completely disappear. I never could get anything right the first. There would always be mistakes. Even when everything seemed perfect, somone might do something stupid, like leave the original "tape ups" in a hot car, and have the pads and traces drift when the glue melts. Traces and pads falling off on the way to the photographers was common.
I once worked on a very simple design where I decided I was going to have one PCB that worked the first time. Everything was triple checked by 3 different people. Everything looked good until the PCB arrived. The PCB fab shop had gotten the component and circuit side reversed. Life was hell.
All of that changed when computerized layout and schematic capture arrived. The term "capture" is rather interesting as I participated in several ordeal processes of converting pencil drawings on velum to vector line drawings on a computer. I think my first was in 1979(?) on an Applicon CAD system running on a PDP11/34. Having an RF design engineer doing board layout, mechanical design, and drawing schematics was initially deemed a waste of time, so I had to do it after hours. I wanted to experience the entire process, which proved worthwhile.
When I first jumped into this newsgroup in about 2011, I got an initial surprise when the other JL (John Larkin) announced that he doesn't do full breadboards of complete products. In the 1970's and
80's, I always did breadboards because there were so many unknowns that could only be answered by building a prototype. Today, those problems are anticipated by simulations and better characterized parts. In other words, most of what I did back then is now totally obsolete.-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Here's the undisputed king of prototyping;
He published vast amounts of application notes with plenty of photographic evidence.
We did black pads (padmaster) and black traces. The mylar sheets were padmaster, top traces, bottom traces, assembly, and often a ground plane thermals. Sometimes more layers. The photographer could make ground plane film from the padmaster - all copper, clearances for the pads, thermals added from the thermal sheet.
We did biggish boards, so worked 2x.
At Data General, only one person had a reserved parking spot: the layout guy.
The best layout people I have worked with were women. True today.
A good light table, and a young body, were necessary for hand-taped layout.
You also needed a flat table with an overhead UV light, for burning sepia assembly and fab drawings from the various mylar layers. And a blueline machine of course.
We didn't have trouble with multilayers. We just checked the layouts (and the film!) a lot. Most boards worked first time; still do. A couple days of overboard checking pay off.
I still have a few mylar layouts around. I'll post pics if anyone is interested.
I never have!
In the 1970's and
-- John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Jim, rest his dear soul, was something of a hack. Much of his stuff was over-the-top complex, and his idea of stabilizing any control loop was to add a huge cap somewhere.
I met him a couple of times at the Foothill flea market. He was nice and seemed sort of shy. Unlike Bob Pease, who was really out there.
-- John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Sometimes. Depends on the situation.
For a guy with very little formal training and almost no math at all, he did a remarkable amount. Errol Dietz, who used to be CTO of National, started out as Bob Pease's technician.
Gotta hand it to folks like that.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Some of the best appnotes came out of LT (and NS) - unfortunately the bulk of my junkbox is salage. AFAICR I've yet to find any LT parts in anything.
NS is pretty much a second source supplier too, I almost never find any parts that are uniquely theirs in anything.
The last NS only part I found was a Boomer stereo amp chip, it was a sort of large wallet thing with CD pockets, the amp and speakers were bonded into the foam padding - you had to provide your own CD - "Walkman" device.
Agreed.
Yep. I brought in a NuArc light table that I inherited from a previous print shop adventure. The lighting was superb, fairly cool, and the table big enough for most PCB's. Something like this: I dragged it through 2 employers, several long term consulting jobs, and two home business ventures.
At the time, leaning over the table for hours was not particularly difficult. Today, it would give me back pains in about 15 minutes. Yep, a young body was a requirement. As I vaguely recall, the oldest PCB layout person I knew that did layout on mylar was about 25 years old.
Yep. I learned the hard way NOT to run the layout and blueprint paper through the rollers on the Diazit(?) machine. Destroying the mylar original was not a good thing. I had a sheet of plywood and a loose glass plate. I would pile everything between the plywood and glass plate, and take it outside for the exposure. Most of the time, the registration was tolerable. At one company, we did have a UV light, but it was constantly being "borrowed" by the CEO's son for his psychedelic light show parties.
That was suggested many times. However, the schedule never permitted it. Management tended to prefer doing things over rather than getting it right the first time. I was not in a position to change that even though the damage it caused was obvious to everyone involved.
I found one of my layouts from 1985: It's a light pen interface card for the IBM PD as a 16 bit ISA card. I did a lousy job and am not very proud of it. However, it does show what was typical of 1970's PCB layout technology. If anyone wants details or more drawings, please say something as all of this is going into the trash in a few daze.
Never having announced or never having done full breadboards? I'll assume never having done full breadboards.
You gave me quite a shock when you mentioned that. I've always built breadboards of everything I've done. At first, I didn't think it was possible to bypass the breadboard stage. I then talked to others in the business and found that few have the time or justification to do full breadboards. Many things have changed between the 1970's and today. Mostly, the components have become so small, that building a breadboard (much less the real product) by hand would be impossible. I tried it with a PCB that had a few 0603 resistors and decided that it wasn't going to happen. Better to go directly to the PCB. Also, as I mentioned, modeling, simulations, and better characterization of the components have also improved the situation.
Back to refurbishing a sewing machine. One can't do electronics full time.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
You didn't literally need a UV light. A 250-watt warehouse-type mercury vapor lamp, maybe 6 feet above a table, worked fine.
Ooh, curved traces. I was taught to never do that, on the theory that the tape would eventually creep in the corners.
Right. I only breadboard little snippets of circuits. For most designs, I don't breadboard anything. What with ARM CPUs and FPGAs and all those tiny parts, breadboarding doesn't work.
It's faster and better to lay out a board, check the heck out of it, have manufacturing build a couple, and test it.
I know companies that define "breadboard" "prototype" "beta" "pre-production" "pilot production" and "production". And use all of them. Takes them years to finish anything. They assume the first few iterations will have errors, so they do.
-- John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Yep. That should work. Some detail and alternatives: How we got to the plywood and glass kludge was almost predictable. Someone defined the need. Management declared that there was no money, floor space, staffing, etc. Irritated engineer throws something temporary together to be used only until the necessary money, floor space, staffing, etc are found. However, since the temporary kludge worked reasonably well, the crisis had been averted, and the kludge become permanent.
Moral: If it works, it's permanent.
That does happen if one stretches the tape when laying a trace. It's especially bad with narrow traces. Traces will move, especially if the layout is left in the sun. I used a rubber roller from my wet photography kit, to flatten the traces and make sure they're properly stuck to the mylar. (Incidentally, note that I used acetate instead of mylar in the above layout. Not a good idea and I forgot why I did it).
For RF, rounded corners are a problem due to impedance bumps. Sharp corners are equally bad due to reflection problems. The compromise is a chamfered corner (mitered bend): which unfortunately also makes a tolerable fuse at the bend.
However, the above PCB is not an RF board. Instead, the problem was the cheap wave solder machine that we were using at the time. Somehow, it often managed to burn or scrape off the solder mask on sharp corner bends. The result was usually an impressive solder bridge at the corners and a tedious touchup job. I was never able to determine the cause, so it was circumvented by using radiused bends and liberal trace spacing.
I had a weird situation at 3 consecutive companies. After the usual extremely long management inspired delays deciding if the company should work on a given product, a schedule was created, usually by the engineering manager. Invariably, there was not enough time to work through a proper design. For example, one project that took about 8 or 9 months from conception to delivery, only allowed 2 weeks for the initial (paper) design. Everything else was allowed a fairly normal period (breadboard, testing, FCC certification, compliance testing, fixture construction, prototype run in manufacturing, etc). In effect, the design was mostly frozen two weeks after the project started. Little wonder we needed a full prototype in order to find the inevitable design errors. If we had time to have done a more rigorous design, much of the subsequent fire drills could have been avoided.
As I previously noted, my attempts to do one product perfectly the first time, failed because the PC fab house reversed the component and circuit sides of the PCB.
Lesson learned: Trust but verify.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I sometimes put test traces with SMAs on boards and TDR them. For a 50 ohm microstrip on a normal board, 90 degree bends are invisible on a
20 GHz TDR. Vias are visible. What's tough is the transition from microstrip to an edge-launch SMA. We've spent a lot of time getting that good, ATLC sims and such.We used to put PARTS SIDE and SOLDER SIDE in copper text. They need to read right on the finished board.
-- John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Ah, a diazo copier. I first, and last, used one in high school drafting class, around 1989. I remember that it was the first time I had seen a peristaltic pump, and that after several guys had made copies on it, the ammonia fumes would start to fill the room. The usual remedy was to open the windows, even in January in Kansas City. Who needs OSHA or a MSDS, anyway.
At a job about 7 years ago, the Panasonic 32" professional flat-screen monitor (full HD, metal case, serial port, HD-SDI inputs - a few grand at the time) was absent one Monday morning. After a search of the building and general denials, the boss was preparing to phone the police. Just then, a person in the same position showed up, and admitted that he had taken it home over the weekend to watch the ball game.
In the flesh, but as Rev D, as opposed to the Rev B artwork above:
In June 1986, you could get this board, an FT-156 light pen, *and* a free copy of Windows (about what it was worth, then), for the low low price of $349! Roughly $760 today, according to the bls.gov calculator, so probably even more than that. Source: ad in the June 10, 1986 "PC Magazine", probably not available at or maybe even
At the few places I've worked where they made boards from scratch, it depended on the board. Simple stuff (microcontroller, a few LEDs) didn't get breadboarded. Complex stuff (like a several-hundred-watt
1 GHz transmitter) had some sections breadboarded, like the final amplifier and maybe some of the filtering. Then they would order three boards, stuff and test, and usually end up doing one spin of the board. This was recent enough that it was all CAD.Matt Roberds
From the source you cite: "If you use a radius greater than three times the line width, you will have a transmission line that is almost indistinguishable in impedance characteristics from a straight section."
So where is the problem?
My understanding the reflection idea is also a myth but rather the real issue is the impedance change due to the added capacitance of the corner, which is also supported by your reference. Impedance changes will also cause reflections, but the signal does not reflect from the corner itself like a light beam.
-- Rick
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