Joe,

Thanks for correcting my mistake.

Matthew

>>> Joseph Fjelstad <[log in to unmask]> December 16,
1997  12:48 pm >>>
Hi Matt!

Good point...  but I think you meant glass transition
temperature (Tg) and
not CTE (coefficient of thermal expansion). You may wish to
correct your message

Cheers!
Joe

At 12:16 PM 12/16/97 -0800, you wrote:
>Since this topic is very hot in Technet, I'd like to drop few
>cents of my own.
>
>All we, boneheads know board design and fabrication
>processes are contributing factors for flatness of boards.
>Hope we all realize that CTE of FR4 material is approx.
>130'c.  When the material goes above this temp during
board
>fabrication, reflow or wavesoldering processes, it expands,
>shrinks, warp, bows, and do all kinds of bad things to itself.
>So why not a mad chemist invents a board material with
CTE
>of 250'c or higher?...
>
>Using OSP or Ni/Au surface finish boards provides
>consistent flatness because they are not subjected to
>thermal stress during board fabrication process, unlike
HASL
>process.
>
>regards
>Matthew Park
>Automation Engineer
>Norsat International Inc.  BC.
>
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