Hello Jim:
I too would like to have a copy of this chart, if you don't mind.
My fax # is 208-622-4377.
I highly appreciate that.  Thanks and regards.
Gabe Cherian


-----Original Message-----
From: James R. Paulus <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Wednesday, October 21, 1998 8:27 AM
Subject: Re: [TN] FR4 thermal expansion


>I have a comprehensive chart which I can fax you, if you want to provide
the
>phone #.
>Generally, Z-axis is 60 to 80 ppm (or microinches/inch/C), X is 17-20 ppm,
and
>Y is 15 to 18 ppm.  Lots of variables however:
>a.  These values are for a temp ramp up to the Tg, which is 135C typically
for
>FR4.
>b.  Remember that FR4 today can be a material with a Tg as high as 180C.
>Higher Tg FR4's tend to exhibit a slightly lower Z-expansion below the Tg
than
>135C types.
>c.  Z-axis is particularly affected by resin:glass ratio.  Higher Resin
>content means greater expansion, which has to be considered in high layer
>count designs.
>d.  Above the Tg,  the X and Y movements get squirrelly because the
softened
>resin allows the glass fabric to pull back against the expanding matrix,
>resulting in much lower values.
>jimpaulus
>
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