Hi Joyce,

It may help if the manufacturer of the heat sink starts with 1.0 cm stock
instead of starting with thicker Cu stock and machine it down to 1.0 cm. I
do not know how practical is that and what surface finish the heat sink
should have. But it may be worth trying.

Sherif,

----- Original Message -----
From: "joyce" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, July 11, 2002 8:16 AM
Subject: [TN] warpage heat sink


> Guys,
> I got a heat sink look like potato chips after reflow using conduction hot
> plate (230-240 C).  The heat sink is 1 cm thick Cu with few position screw
> holes on 2 sides.  The size is 13.0x10.0x1.0 cm with 0.45 mm diagonal
height
> variation at the moment (one corner point to the sky and one down to the
> earth).  Any remedy for the "cure"at this stage? ?  (it is Au/Ni plated).
> Anything I can do to prevent from happening besides specify the annealed
Cu
> must be used?  (can't reflow on the other side, it has to bond to fan by
> thermal compound).  Never see anything like that.  The internal residual
> stress must be extremely high!
> Thanks in advance for all your help...;-(
>                                                                        jk
>
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