To socket or not to socket?

[Magnus Danielson]

From: "Batz Goodfortune" <batzman at all-electric.com>
Subject: Re: To socket or not to socket?
Date: Sat, 05 Feb 2000 12:19:54 +1000

> Y-ellow Michael 'n' y'all.
> 	Sockets do have problems (sometimes) in high shock, high vibration
> environments. Where the IC can literally be shaken out of it's socket. Some
> sockets get dirty due to poor materials and or vibration. Sockets suffer
> with expansion and contraction due to temperature as well. This in
> conjunction with dirt can cause poor connections to the IC after a time. We
> use to have this problem with early PCs. The solution was to go round and
> press all the ICs firmly back in their sockets.

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. When your
electronics is standing on the same wooden floor as a bunch of bass speakers
pumping the base-line for larger event, then things will shake seriously, I
tell you. I have also seen gear go bananas from that treatment while this was
their intended operating environment. What do you guys feel about
self-oscillating FIR filters? ;)

But, I also seen what happends when gear becomes 20+ years of age and then the
sockets really show their downside. I have this effect box where the socket
based interconnects seems to be THE only real sign of age, it makes any other
age problem be hidden in the troubles. I have been moving an overhaul of it
up for years since I just don't like debugging this type of trouble.

> However. Most of this can be avoided if you (a) never move your gear. Or
> (b) place a dob of silicon adhesive or hot-melt under the chip before
> pressing it into the socket. This prevents the IC from moving and because
> of it's rubbery nature, also provides a kind of suspension support. You can
> replace the IC by simply prizing it out of it's socket as usual but it
> won't possibly move of it's own accord.

Right, not moving your gear is one reason where sockets should be less of a
threat. But there are places where your living conditions still may have
constant vibrations. For instance, New York area is the 4:th most earthquake
active area in the USA. There are a constant set of small earthquakes, so they
are barely noticed. These sources are however weaker than a shakey transport.

> I have heard RF people complain about sockets causing problems but that's
> hardly an issue with synth gear I would think.

Yes, the reason is simple, you add lead length and thus add inductance. Also,
you increase the cross-coupling in both inductive and capacitive sence.
This is also a reason why sockets are basically band of high speed digital
designs, it is much more analog up there.

> On the whole I use sockets extensively. Especially when running up a
> prototype. You never know when you might want to exchange that pin
> compatible OP-amp or something. And as John says. Replacing an IC in a
> socket is 500% easier if it's in a socket.

It is sure easier, but I would at least like to point out that one migth want
to be a bit picky about which sockets to pick. I rarely use sockets and
besides, at the few times I need to replace a chip I get to perfect my
experience of unsolder chips. It's a nuance but it doesn't happend that often.
For experimental curcuits sockets play a diffrent role, but once I have
settled for an IC I would solder it hard.

Cheers,
Magnus