Also known as field assisted bonding and anodic bonding, electrostatic bonding has been in use since the 1960s for joining silicon to glass. Similarly to diffusion bonding, electrostatic bonding requires that the surfaces to be joined are as flat and clean as possible.
The components to be joined are heated in a vacuum and pressure is applied. Typical conditions would be 3MPa and 400°C. When the required temperature has been achieved, a DC voltage of about 100V is applied, with the metallic component being held positive.
The non-metallic component must contain mobile ions such as Na+. The process has been successfully applied to glass and some ceramics such as beta-alumina.
Advantages
- bonding performed without interlayers
- relatively low bonding temperatures
Disadvantages
- expensive capital equipment
- specialised process
- material limitations
- requires specialised knowledge
- surface area limitations
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