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.
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.
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.
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
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558