Prevailing antennas here are a 40 Meter
Delta Loop and a Half Square, oriented with the lobes north-south from
Crossville, Tennessee, USA. Before retirement I worked in the prototype development
laboratory for Delco - Hughes G.M. Electronics Division and part of the
work centered around building proto boards on our Philips MCM-VII
placement machines manufactured in the Netherlands.
One thing that unnerved me a bit was that
all of our reels of surface mount chips had to be date-coded not to
exceed 1 year of age. Any reels (Siemens, RCA, Mitsubishi, Philips, NTE,
Motorola, etc.) of chips older than 1 year in our inventory had to be
destroyed. I asked one of the Philips engineers about it one day,
wondering if we could expect electronic equipment failures after a
year's service. (???)
He explained that the expiration date had to do with the 'solderability'
of the components - not on their life expectancy. The oxidation present
on their contacts caused reliability problems in the continuity -
usually in the wave-solder operations. I thought that was particularly
interesting.
I remember trying to change an op-amp in an older Radio Shack HTX-202
and I had a terrible time with solderability issues and finally caused
the traces to lift off of the circuit board before losing the battle.
Old solder joints can be a veritable challenge to reflow and repair!