The CTE for both products ( assuming you are comparing the Borofloat to
the Pyrex 7740) are the same at 3.25 x 10-6/K (0 to 300 degree C)
 From what I am aware - 450 is well within the maximum operating
temperature of Borofloat-which is listed for long term use at 450c and
short term at 500c.
Maybe you have some other stresses or even a thermal shock is present
that are the cause of the cracking.

Regards,
Ken Smith

Kmbh Associates 47 Rocket Circle
Rancho Cordova, CA 95742  U  S  A
510-714-5055 Efax- 510 217 4421 or 561 658 6136
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Mirror Optics, Optoelectronics, MEMS, SOI, and other Semiconductor
applications. Service in SOI, Polishing SSP and DSP.
Quartz, Glass, Pyrex and Borofloat Wafer Supply. Anodic Bonding. SOG, SOS.


Zigurts Majumdar wrote:

> Hi,
>       I've read a paper where borofloat glass was anodically bonded
> to an Si wafer with 1200 V at 450 C, I used 15N of force for
> total area of about 1/3 of a 3 inch wafer. The glass cracks, I tried 3
> times. Does anyone have any suggestions about a better protocol? I've
> assumed the CTE is the same as Pyrex, which is true for the average
> CTE from 20-300C, but I haven't seen the data at 450 C.
>
> Thanks,
>
> Ziggy
>
> ********************
> (Ziggy) Zigurts K. Majumdar
> Department of Physics
> Laboratory for Fluorescence Dynamics
> University of Illinois at Urbana Champaign
> 1110 West Green St.
> Urbana, IL 61801
> ********************
>
>
>
>
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