There are composite pwb materials with matched CTE's to silicon  etc and therefore to Kovar/42
alloy etc, but these tend to be expensive.
I am a little puzzled on this, maybe I am out of touch, but can you explain why the CTE of the
leads is important to you?
Alloy 42 has been a standard lead frame material for years. So far as I understand it the usual
reason for device manufacturers changing to copper is to improve thermal conductivity from their
device, which is worth the extra difficulties involved.

Mike

----- Original Message -----
From: Louis, Edwin @ CSE <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, February 18, 2000 7:10 PM
Subject: [TN] Alloy 42 Leaded TSOPS


> We have a sole source for  TSOP components, in which, they are only
> available with alloy 42 leads. The vendor refuses to build the parts with
> Copper leads because the  CTE of alloy 42 better matches the die CTE and as
> result they have fewer component failures and defects.
>
> Does any one know of a PWB material that would better match the CTE of alloy
> 42 leaded TSOPs?
>
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