I had the same problem. I am using Pyrex 7740 blend or at least the vendor
claims so. I have checked the thermal expansion coeff. of Si and Pyrex and
they are almost the same. I concluded that either the batch of Pyrex was bad
(because bonding process was going fine with previous batches) or Pyrex
wafer was thin and it couldn't take the stress after the sample cooled
down. Although I am also curious if this can be avoided.

Mehmet

On Thu, Feb 26, 2009 at 8:12 AM, jingru zhang  wrote:

> Dear all,
>
> I have deep channels (around a hundred microns) on the silicon substrate.
> and
> during the anodic bonding of silicon and glass, they bonded well but the
> glass cracked. Maybe it is the stress around the channels walls which
> caused
> cracking. The voltage I am using now is 500 w, and the temperature goes to
> 400 deg c.  Does anyone have similar experience? How to avoid this?
>
> Thank you very much.
>
> Best Regards,
> Jingru

--
Mehmet Aykol
University of Southern California
EE - Electrophysics
Phone: (213) 821-4090