12 Mar
2011
12 Mar
'11
1:04 p.m.
On 2011 Mar 12, at 7:22 AM, Shoppa, Tim wrote:
Oh, I'm (too) well-acquainted with cheap phenolic PCBs from the 50-60s.
But there was good- or reasonable-quality phenolic PCBs too. If
Sylvania was using some low quality stuff perhaps that's one of the
reasons they lost the missile silo contract, but you'd think they would
have known better for a big mil/gov contract.
HP used phenolic PCBs to a limited degree (bad) in some tube equipment,
but their early-60s solid-state equipment used a pretty reliable
phenolic PCB. TMO, they moved to fiberglass sometime in the mid-60's.
IBM got by with that yellow substrate for their SMS cards for a decade,
an early PCB substrate that was also used in consumer stuff.
As much as phenolic PCBs were widely used into the 60's, there was lots
of fiberglass used in that era too.
Not an indication of prevalence, but I have test equipment from as
early as 1961 with fiberglass PCBs.
IME, while a good fiberglass board is preferable, a good phenolic board
can be better than a bad fiberglass board, and there were lots of bad
fiberglass boards.
I wonder what
he means by 'cardboard' circuit boards though
I think it was a dig at Sylvania's (indeed the industry-wide) standard
PCB technology of the time. Today we are very used to etched PC boards with a
fiberglass epoxy
substrate and copper traces that were etched.
But the original consumer-type PCB technology was more often formica
or phenolic-type circuit boards with traces that were stamped from
sheet foil and then glued to the phenolic. (There was also a mil-spec
type of PCB that was a ceramic base with silvered traces essentially
painted on - you see stuff like this in Tek scopes of the 50's and
60's.)
Not surprising to see Sylvania mentioned in the same breath because of
course Sylvania used the phenolic PCB technology across many of their
consumer TV's and radios.
The cheap 50's and 60's phenolic PC boards are indeed like plasticized
chipboard/cardboard. I'm 99% sure that phenolic is still being widely
used in consumer electronics (although it is a higher grade than that
from Sylvania's 60 PCB's and you might not know it's really
plasticized chipboard until you break it.).
DEC modules from the 60's were most often a high grade (for the time)
phenolic PCB. Glass Epoxy really took off in the 70's. I'm thinking
the Foxboro 1 pictures are from the early 70's and represent a later
implementation of the Sylvania architecture. Fingers on phenolic PCB's
are far less durable than fingers on glass epoxy PCB's.
I never used a Fox 1, my earliest exposure was the Fox 2/30.