4 Mar
2014
4 Mar
'14
5:05 p.m.
FYI, a normal ENIG finish is very thin. Most board houses will charge
extra for hard gold fingers which are designed for insertion durability.
Most of my ENIG ISA boards wear through with just a few insertions.
HASL is more durable.
4 layers is not necessary as most signals on the bus transition or are
registered sub 1 MHz.
-Alan
On 2014-03-04 19:48, allison wrote:
However properly plated fingers is a must. That's
Nickel over Copper
then Gold. Why?
My first Altair had a poisoned bus some of the early MITS cards were
tin
plate, some
Gold over Nickel and the nasty ones were Gold over Copper. Ever see
gold turn green?
That's what happens you get copper migration and the connectors
especially gold plated
ones get contaminated by that... then its a remove and reinsert before
using forever
or crash. The fix for the Altair was replace the backplane. Not
likely to hppen on a
PDP-8.
Allison