Anodic Field-Assisted Bonding

Anodic bonding technique allows adhesion of glass onto a metal or semimetal such as silicon. In anodic bonding, glass wafer and silicon wafer are bonded together at elevated temperatures 

A special type of glass named Pyrex 7740 is most commonly used in anodic bonding because of large sodium cation content and matched thermal expansion coefficient ( 32.5 X 10 cm/°C) with that of silicon. The approximate Composition of Pyrex 7740 is 

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Anodic bonding is a relatively simple process, which provides hermetic seals by bonding silicon wafers to glass plates at rather low temperatures (300—450 °C), with the assistance of an electrostatic field (400-800 V), such that the glass wafers are negative with respect to the silicon [35]. 

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