Werner:
Is the coefficient of expansion for ceramic components
linear or exponential? If it is exponential, components may reach a point
where the expansion still exists but it is negligible. What are your
thoughts?
Regards,
Ramon
> -----Original Message-----
> From: Werner Engelmaier [SMTP:[log in to unmask]]
> Sent: Monday, November 17, 2003 10:05 PM
> To: [log in to unmask]
> Subject: Re: [TN] Not that our process is out of control or anything,
but --
>
> In a message dated 11/17/2003 16:52:11, [log in to unmask]
writes:
> >It is the preheat it the wave that is controlled (the infamous 2C/sec)
> >to prevent thermal shock.
> ---This is correct.
> >Once the chip has achieved a specified temp, all the materials have
expanded
> equally and >after this point the rapid thermal change of hitting the wave
> does not affect the chip.
> ---Sorry, but there is no such condition; different materials will always
> have a differentiasl thermal expansion, unless they have identical CTEs.
> >It is the different expanding properties of the two materials that cause
the
> chip
> >to crack.
> ---Quite correct.
> >Once they have both expanded to their maximum state, the temperature
curve
> is irrelevant.
> ---Sorry again, but there is no such state; as long as you raise the
> temperature materials will expand, unless they have a negaqtive CTE.
>
> Regards,
> Werner Engelmaier
> Engelmaier Associates, L.C.
> Electronic Packaging, Interconnection and Reliability Consulting
> 7 Jasmine Run
> Ormond Beach, FL 32174 USA
> Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
> E-mail: [log in to unmask], Website: www.engelmaier.com
>
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