Did ponder the same way Inge ;
The high(permanent)force is actually more harmful that good in longer term
and in hotter environments .
Some of the bolted misdesigns caused problems within couple of years .
That may be why Bill is on about ; the window between too little and too
much is desirable to know ,
especially as the consequent relations may influence the reliability of the
joint itself .

Quite often I've seen bolted AFTER the solder ;
with so much induced twist torque that the self shear was just a question of
time .
Interesting topic Bill ; but very much on application dependable answers ;
you did not give enough info .
Unless you do, feel it from inside , vibration test would aid the visibility


paul


-----Original Message-----
From: Ingemar Hernefjord (EMW)
[mailto:[log in to unmask]]
Sent: Thursday, 30 September 1999 2:31
To: [log in to unmask]
Subject: Re: [TN] HELP!


Bill&Carey,
sure you really need to measure the pressure? Why?. Isn't the percentage of
true contact what is of most interest? Calculated the need how to transport
heat from sort of a Neumann computer, in principle everything on one wafer,
and the contacting area seemed to be A&O. We proposed filling the microgaps
with He, so force wasn't so critic. Of course you can't do that here, but
Choterm's and other's cooling mats use to fill up enough. Just interested to
know...../Ingemar


Bill,
Let me know if you need help on this.  There are straight foward ways to
measure contact pressure by placing known materials of specific hardness
where you want them and measuring indentation.  I have never done it, but it
is routine in some R&D labs.  I'm not a fab person, so I'm not familiar if
this is standard.
Carey



>Hi everybody:
>
>Does anyone know of any effective ways to measure contact surface force
>like between a heat
>sink and heat source?
>
>Thanks.
>Bill Ebner
>
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