Seeking Motorola S38FC012PIO2 ($$$ Bounty! $$$)

Dwight K. Elvey dwight.elvey at amd.com
Mon Mar 14 16:51:45 CST 2005


>From: "Pete Turnbull" <pete at dunnington.u-net.com>
---snip---
>
>Bad contacts in sockets, accumulation of dust and airborne detritus,
>and problems resoldering or modifying boards when they get older.  It's
>the lighter silicones that cause the problems, though, and if you
>can find a modern grease that has a smaller spread of molecular
>weights, the problem will be greatly reduced.  The difficulty is in
>getting rid of the silicones, as they don't wash off, and flow into
>holes especially when you heat them up.

Hi
 Silicon grease has a negative coefficient over much of the
normal temperature range. I actually gets thicker with heat not
the other way around.

>
>I used to do a lot of commercial repairs, especially on 1980s micros,
>and I used to hate the ones where people had put gobs of heatsink
>compund on socketed chips.  The compound contains lots of light
>silicones, which used to get into the sockets and cause bad
>connections, and then it was a pain to remove the socket and solder in
>a new one.  Of course, the worst were the ones drenched in "contact
>cleaner" and WD40.

 Don't confuse with heat sink compound. I actually put silicon grease
into sockets to improve contact. It is used by manufactures in many
places that require improved contact. Heat sink compound is nasty
stuff. It is not what I'm talking about. I have sockets that have
10-20 years of trouble free function with silicon grease in them.
 From experiments that I did years ago when working for Intel,
silicon grease not only works well on sockets and edge connectors,
it help switches as well. Especially those that have particularly
high or low current. In the high current ones it helps to prevent
arcing. The improved contact reduces contact heating.  In the low
current ones it reduces the need for contact scrubbing.
 About the only bad thing I can think of is that one might
get it on the surface of a floppy disk. Any grease on the surface
usually makes writing the disk problematic.
 I've never seen DC#4 cause a bad contact. I've seen many cases
where it has improved it enough that problems of contact over
heating are no longer an issue ( Molex connectors in pinball
machines ).
 WD40 contains all kinds of junk. I've never had troubles soldering
when the joint had silicon grease ( DC#4 ) on it. In fact, most
cases, it almost works as well a flux by keeping the oxidation
down ( Also done while at Intel ). The only reason Intel didn't
use it after the experiments I did was because they feared that
pre-labled parts would get this on them and the lables would not
stay on ( a valid reason ).
Dwight





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