On Sat, 20 Sep 2014 17:22:29 -0700, Jeff Liebermann
wrote:

On Sat, 20 Sep 2014 11:00:09 -0700, John Larkin
wrote:

The best layout people I have worked with were women. True today.

Agreed.

"How It Was: PCB Layout from Rubylith to Dot and Tape to CAD"
http://www.eetimes.com/author.asp?section_id=14&doc_id=1285442

A good light table, and a young body, were necessary for hand-taped
layout.

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:
http://www.ebay.com/itm/321208321135
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.

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.

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.

You didn't literally need a UV light. A 250-watt warehouse-type
mercury vapor lamp, maybe 6 feet above a table, worked fine.






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.

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 still have a few mylar layouts around. I'll post pics if anyone is
interested.

I found one of my layouts from 1985:
http://802.11junk.com/jeffl/PCB-Layout/
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.

Ooh, curved traces. I was taught to never do that, on the theory that
the tape would eventually creep in the corners.





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.

I never have!

Never having announced or never having done full breadboards? I'll
assume never having done full breadboards.

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