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
High Purity Float Zone and Specialty CZ Silicon  for Power, IR and
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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