We routinely use tape or adhesives to attach heat sinks. First the
adhesives: Loctite 315 gives about a 15 minute cure time when applied
properly and can be stressed (temp/mech) after about two hours. In fact
the temperature of the IC helps accelerate the curing slightly.

For the tape, we get heatsinks with the tape already attached to the
sink from the sink supplier. We then heat the tape slightly (warm
hotplate seems to do well, though I guess hot air guns would work as
well). Then we remove the tape backing & attach it.

I caution about the use of down force on the IC's, especially if they
are either BGA or CSP. These package types are not 'compliant' packages,
such as a leaded package (TSSOP, QFP, etc...). We use something less
than 2 pounds to attach either tape or adhesive...

Hope this helps

-----Original Message-----
From: Mark Ross [mailto:[log in to unmask]]
Sent: Tuesday, December 29, 1998 6:50 PM
To: [log in to unmask]
Subject: Re: [TN] Attaching heatsinks to IC's


Chi,

Do you really want to unecessarily stress the solder connections like
that?  It can lead to pre-mature
field failures.

However this may depend on the type of IC.  Is it DIP, TO-220, TO92, SMT
SOIC etc.  If the force is applied
parallel to the solder connection this may put force on the solder
connection and cause premature
failures.  You may want to check and see if there are any guidelines for
this and it may be material
related also.  For Example, ok to do on FR-4 Material but not CEM-1 as
it flexes more.  Let me know how it
turns out!

Mark Ross
Sr. Design Engineer
Whistler Auto-Mation Products Inc.


Chi Wong wrote:

> Hi,
>
> We have several applications of attaching heatsinks to IC's at our
plant and
> currently it seems that the easiest method is to use a double sided
thermal
> tape.  We are currently applying the tape manually and using hot air
guns to
> heat up the surfaces and tape to decrease the pressure and time
required for
> the adhesive to set.  However, we are searching for a more reliable
and
> consistent automated method for attaching the heatsink to the IC's
without
> putting the solder joints in jeopardy.
>
> Does anyone know of any press manufacturers that may carry something
for
> this type of application?  We are talking about 30 psi at room temp
for 5
> sec or 10 psi at 50-65 deg C for 5 sec.  Does anyone know of a better
> process besides thermal tape?
>
> Any feedback is appreciated.  Thanks.
>
> Chi Wong
> Process Manufacturing Engineer
> [log in to unmask]
>
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