To socket or not to socket?

[Batz Goodfortune]

Y-ellow Y'all.
	Not wishing to drag this out too much longer. But I wish to concur with my
learned colleagues and add one more thing about sockets.

At 07:00 PM 02/05/00 +0100, Magnus Danielson wrote:

>You should notice that my experiences are coloured by may days as
repairman of
>PA-system gear where not only transport but also normal operation would hold
>pretty impressive shock and vibration experiences for electronics.

[bobbit]
And my days working with old PCs and Apple ][s

The thing about where I live, and this isn't experienced everywhere, is
that we have a fairly widely varying temperature range. From lows of just
about zero degrees in winter. All the way up to extreme highs of perhaps
44C in summer. If you go out-back it can get as hot as 50C in places.
That's half boiling for those still using Fahrenheit. 37.6C is body
temperature in Celsius. Right at the moment we've just come out of a 3 day
42 degree heat wave. (107 degrees Fahrenheit) We've got a cool change of 35
degrees and belive me, that really does feel like a cool change after 3
days of 42. But I digress.

The point is that not only does the temperature change on a daily bases but
the ambient temperature changes widely as well. In November December, and
again in May/June, you can expect that anything could go wrong. just from
the general expansion and contraction of materials. Sockets are
particularly vulnerable. Especially those on PC expansion cards. Apple ][s
use to be notorious.

The solution of course is often simple. Press down on the ICs and/or
re-seat them. Especially expansion cards etc. But I've seen ICs just kinda
sitting on top of their production sockets for apparently no reason. As if
someone had extracted them and just left them there. Or they were
manufactured in the Bermuda triangle. And all due to a few years of this
expansion and contraction. One of the reasons we have air conditioned
equipment rooms is not so much because of the accumulated heat, but simply
to provide a reasonably stable environment. Temperature and humidity all
take a toll. 

And it's also worth noting that different materials expand and contract at
different rates. The plastic housing for socket pins expands differently to
the metal of the pins themselves. All kinds of weird shit can happen as a
result.

Now for me, I'm pretty use to it. I expect to have to do all this stuff
from time to time. But for a consumer this might be the source of extreme
aggravation. Most punters (in fact a lot of engineers) fail to consider
changes in weather as a source of problems. And for this reason, in this
kind of climate, sockets are bad news.

This is not to say that you shouldn't use sockets. If I have to repair
anything I'll generally put it in a socket. This is primarily to save the
board any further damage. Especially if it's one of those Japanese pressed
phenolic type boards. If I'm working with CMOS on a prototype (The majority
of my work in fact) I'll always use sockets of course. But I always expect,
and suspect that I'll have trouble with them somewhere down the line. I
don't always but then sometimes I do. If it happens around the above
mentioned months of the year then it's a high likelihood.

Having said all that I'm still unclear however which sockets are best. I
have used Machine pin sockets that have never fouled up. But then again
other machine pin sockets by the same manufacture but a different batch
have been problems. Likewise with production sockets. I've had some
absolutely crappy looking sockets that have never given me any problems. On
the other hand I've had some that look like they're designed to make
maximum contact with the pins and they've been so much trouble that I've
eventually replaced the socket it self.

I am of the opinion on two things. That with production sockets, very fine
tolerances in manufacture could have a large bearing on the longevity of
the socket. 2 That machine pins by their very nature can cause problems
because they really only contact the pins in their 4 corners of the pin.
Rather than across either side of the pin's surface. So in some cases
you'll get a great contact that will never shift. In other cases the daily
expansion and contraction is enough to weaken the contact. Or worse, allow
dirt to deposit while expanded and compress it into some kind of resistive
gunk that eventually causes a strange, unexplainable failure.

As an aside. Never use sockets on a rocket. My father use to work as part
of the Woomera rocket program. Including prep work for the US red-stones
and British Blue Streaks. These guys found ways of getting even some valve
gear to go up on these things but the G-forces were so great that they
would rip every component, and the tracks off an ordinary circuit board.
The boards were a 3 to 5 layer ply construct on a fibre glass substrate. To
etch the boards required a 3 to 5 stage etching process. One of the layers
was nickel for some reason. All just to make sure the tracks were strong
enough to survive. Anything in a socket wouldn't survive the first second
of blast off.

And just out of interest, the substance y'all know as silly putty was
actually invented here for this specific purpose. I have a very small pot
of the original stuff. It was actually designed to be poured into
electronics cavities in rockets. Not only to suspend the electronics on
lift off but also to cushion it when it fell back to Earth. We're talking
something having to survive a heap of Gs, then travel up to 3000Ks down
range and crash into the desert somewhere. Then have to sit round in the
desert heat for perhaps a month before anyone got out there to find it.
Longer if the locator broke. In those days, the only way they could recover
much of the data was to design measurement systems that could survive all
that and recover them still in tact.

So if you really want to prevent problems with your PAs and stuff, Just get
a shit-load of silly putty and completely fill your boxes with it. 9 out of
10 rocket scientists recommend silly putty. :)

Hope this helps.

Be absolutely Icebox.

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