[sdiy] IC socket reliability

[ASSI]

Hi Dave,

On Sunday 20 January 2013, 18:30:52, Dave Kendall wrote:
> Are turned-pin IC sockets *much* more reliable than the regular double
> sprung flat-plate type, and is the type of plating important?

Leaf-type contacts aren't necessarily as bad as folklore would have it, 
although I've seen specimen that probably wouldn't survive the first 
insertion.  But the finger-type contacts in turned sockets can be dodgy, 
too.  I've recently acquired some fingered-contact socket strips that would 
not make a good IC socket at all because they have much too high extraction 
force on the flat IC pins, which would leave both the IC and the socket 
damaged after the first extraction already.  They are just about perfect for 
round contacts (i.e. stacking with turned pin strips), however.  When it 
comes to plating, many folks always go for gold and shiny, but that isn't 
necessarily the best surface either unless your IC pins are also gold 
plated.  Also, manufacturers have been getting good at plating gold in ever 
thinner layers and unless you know the thickness you can't expect the better 
wear resistance that used to come with it.

But you should ask yourself why you'd want a socket in the first place and 
how many insertion cycles you expect to have.  If you come up with more than 
a single digit, you need a zero insertion force socket anyway if you are 
worried about reliability and if they're any good they frequently cost as 
much or even more than the board they go into.

> Anybody have any experiences they'd like to share?

Sockets of any type are bad news for long-term reliability.  No socket is 
almost always more reliable than any socket.  The exceptions are where you 
can't do in-circuit programming (shouldn't be a problem anymore), where the 
IC in question would be damaged by the soldering process (those are _really_ 
rare), where the IC is much less reliable than the whole board (hmm… you 
wouldn't want to have that either) or lastly when the IC is much more 
expensive than the rest of the circuit and needs to be easily salvageable 
(the socket should be selected from the same price bracket then).


Regards,
Achim.
-- 
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