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From:
"Louis, Edwin @ CSE" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 15 Mar 2000 12:36:55 -0500
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Kelly, could I have your telephone # so that we could discuss this together?
My number is 856-338-3508?

-----Original Message-----
From: Kelly M. Schriver [mailto:[log in to unmask]]
Sent: Saturday, February 19, 2000 5:34 PM
To: [log in to unmask]
Subject: Re: [TN] Alloy 42 Leaded TSOPS


Hi Ed -

In a scan of posts on this subject by the rest of the gang, they have
already noted that the nickel/iron lead material family (which includes
alloy 42) has been around for a long, long time.  Most specifically, on
military ceramic bodied flatpacks, ceramic quad packs, etc., use in hi-rel
hardware for many years.  The TSOP package is similar in style to these
items and should produce no problems that are new or different.  I would
expect that the leads would have some amount of compliance.  If your devices
are in a plastic body, then that's still another plus in a TCE match to the
board.  It might be reasonable to have a few parts measured to determine
their actual TCE over your operating temperature range, before going much
farther.

The wild card in this whole equation, however, may not be the laminate
material.  It may well be the amount of copper in the circuit board zones
immediately under the components themselves.  We designed and built a 16
layer high density multilayer a couple of years ago.  Specimen were
fabricated from both polyimide/glass (12-14 PPM/deg C) and non-woven
aramide/polyimide laminates (low TCE ~5-8 PPM/deg C as I recall).  Copper
thicknesses were held to 1/2 oz. on all layers.  When we had an ITL perform
TCE measurements over a range of -55/+125C, guess what the plots looked
like?  Almost identical to copper at 17.5 PPM/deg C.  We couldn't tell the
specimen apart, without reading the title on the plots.

Let us hear what you learn, and good luck.

Regards - Kelly



-----Original Message-----
From: Louis, Edwin @ CSE <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Friday, February 18, 2000 1:16 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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