At 10:53 AM 4/1/2005 , you wrote:
>----------------------------------------------------------------------
>
>Message: 1
>Date: Thu, 31 Mar 2005 17:44:37 -0800
>From: "Pat Barthelow" <aa6eg@hotmail.com>
>Subject: [TowerTalk] Relay Specs -Coax Switch
>To: w8ji@contesting.com, keith@dutson.net, TowerTalk@contesting.com
>Message-ID: <BAY106-F28BF0ADC546629AE971C02FB380@phx.gbl>
>Content-Type: text/plain; format=flowed
>
>Hello Tom, Keith, and group.
>
>I went searching for some relay images to post and have some experts view
>them and comment on the plusses and minuses relative to High Power RF use,
>of the various designs. I found quite a few pictures, on the web, which I
>may post for viewing and feedback from the experts.
>
>I also remember in the W6AM Biography book by Jan Perkins, that Don Wallace,
>W6AM had humongous numbers of big antenna relays for his Rhombic Farm
>that he had to modify to make less lossy at HF...Very interesting book...
>
>BUT what I also found is mind boggling and I think of interest to many of
>us, especially in this time of (apparent) change towards no-lead solders.
>Check out these NASA and related sites and what they document with respect
>to tin whiskers and the damage they do, esp to high rel (space) systems.
>
>http://nepp.nasa.gov/whisker/photos/
>http://nepp.nasa.gov/whisker/photos/relay/ng/relay-armature2.jpg
>http://nepp.nasa.gov/whisker/photos/relay/ng/relay-armature1.jpg
>http://nepp.nasa.gov/whisker/photos/relay/gsfc/whisker2.html
>http://nepp.nasa.gov/whisker/photos/relay/gsfc/whisker3.html
>http://nepp.nasa.gov/whisker/photos/waveguide/2004-waveguide-tin-whiskers01
>.jpg
>http://nepp.nasa.gov/whisker/photos/waveguide/2004-waveguide-tin-whiskers05
>.jpg
>http://nepp.nasa.gov/whisker/photos/waveguide/2004-waveguide-tin-whiskers02
>.jpg
>http://nepp.nasa.gov/whisker/photos/waveguide/2004-waveguide-tin-whiskers02
>.jpg
>http://nepp.nasa.gov/whisker/anecdote/20year/index.html
>http://nepp.nasa.gov/whisker/failures/index.htm
>
>There are also Ziinc whiskers that did damage, that came from: Floor tiles,
>of all things...
>A paper within these listings documents quite a few million dollar plus
>satellites destroyed by these teeny tiny tin whiskers...
>Fascinating, and scary if you are in the space electronics industry...
>
>73, DX, de Pat Barthelow AA6EG aa6eg@hotmail.com
>
This is a looming problem in the electonics industry. The European Union
started the RoHS laws (reduction of hazardous substances) after some alarm
about the amount of solder in the landfills over there. They set a date
for phasing out lead, and I think it's in a few years. Unfortunately,
there is no substitute that is just as good. While they specifically
excluded military and high-rel applications (there are comparatively few of
them), that's silly. Everyone buys parts from the same manufacturers and
if the part sources go lead-free, everyone gets lead-free parts! (The
Analog Devices guys told me they use the term "Pb-Free" because non-English
speakers get mixed up between short "e" lead (pronounced "led" - Pb) and
long "e" lead ("leed" - the things that hang out of a component that you
solder to).
Maybe people don't mind if their cellphone shorts out and dies in a couple
of years, and they toss it, but nobody wants to toss out a $30,000 aircraft
radio - let alone a multi-million dollar satellite. I don't know about
you, but I sure don't want to lose my Icom to a tin whisker!
From what I gather, nobody really knows how to deal with the
problem. I've heard that a solder coating, a high lead solder, or gold
plating may prevent it. But no hard data.
I'm dealing with this issue at work right now, so sorry if I seem a little
"worked up" about it.
73,
Bob
W4ATM
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