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.
> 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.