16 Aug
2019
16 Aug
'19
3:59 p.m.
From: Brent Hilpert
I've seen pieces of HP high-end lab equipment from
thru the 60s that
used tin plating on the PCB edge fingers, mating into gold-plated edge
connectors on the backplane.
ISTR that DEC used bronze contacts in their backplanes, but basically all the
boards had gold-plated fingers. (I think I've seen a few power supply boards
that had tinned fingers.)
I think the bronze was preferred since the contacts bend back and forth as
cards are inserted/removed, and bronze is more durable; and being part tin,
has the same corrosion characteristics are the tin.
Noel
16 Aug
16 Aug
7:21 p.m.
On 08/16/2019 05:59 PM, Noel Chiappa via cctalk wrote:
The contacts were mostly phosphor bronze, but they had a
little spot of selectively plated gold where the PC board
finger actually wiped. I think they used basically the same
technology from the PDP-8 era to the VAX 7xx series.
Jon
Jon
From: Brent
Hilpert
I've seen pieces of HP high-end lab equipment
from thru the 60s that
used tin plating on the PCB edge fingers, mating into gold-plated edge
connectors on the backplane.
ISTR that DEC used bronze contacts in their backplanes, but basically all the
boards had gold-plated fingers. (I think I've seen a few power supply boards
that had tinned fingers.)
I think the bronze was preferred since the contacts bend back and forth as
cards are inserted/removed, and bronze is more durable; and being part tin,
has the same corrosion characteristics are the tin.
Noel
7:33 p.m.
As Jon said, from my analysis of busted-apart DEC connectors, there's a
selectively plated "pad" where the contact surface actually is.
I wouldn't be surprised if the bulk of the contact fingers is *phosphor
bronze* which is often used in springs. Perhaps we can get Connor to do a
metallurgical analysis once he gets the EDX attachment for his SEM going!
Thanks,
Jonathan
On Fri, Aug 16, 2019 at 10:21 PM Jon Elson via cctalk <cctalk at classiccmp.org>
wrote:
On 08/16/2019 05:59 PM, Noel Chiappa via cctalk
wrote:
that
all the
From:
Brent Hilpert
> I've seen pieces of HP high-end lab equipment from thru the 60s > used tin plating on the PCB edge
fingers, mating into gold-plated
edge
connectors on the backplane.
ISTR that DEC used bronze contacts in their backplanes, but basically boards had gold-plated fingers. (I think I've
seen a few power supply
boards
that had tinned fingers.)
I think the bronze was preferred since the contacts bend back and forth
as
cards are inserted/removed, and bronze is more
durable; and being part
tin,
has the same corrosion characteristics are the
tin.
Noel
The contacts were mostly phosphor bronze, but they had a
little spot of selectively plated gold where the PC board
finger actually wiped. I think they used basically the same
technology from the PDP-8 era to the VAX 7xx series.
Jon
Jon
1954
days inactive
1955
days old
2 comments
3 participants
participants (3)
-
elson＠pico-systems.com -
jnc＠mercury.lcs.mit.edu -
systems.glitch＠gmail.com