Anodic Glass Pedestal Bond Creep Mechanics during Extended Temperature Cycling
Anodic glass pedestal bonds creep during thermal cycling via sodium-depleted layer relaxation, inducing permanent piezoresistive sensor zero-point drift.
Hoya SD-2
Specialized Substrate
Alkaline earth boro aluminosilicate glass provides a thermal expansion profile that matches silicon across a wide temperature range for anodic bonding applications. This hoya sd-2 material is a primary choice for microelectromechanical systems where the sensor die must be hermetically sealed to a rigid base. It minimizes the mechanical stress induced during the cooling phase of the bonding process.
Material Composition
The specific chemical formulation of the glass includes mobile ions necessary for the electrochemical reaction. During the bonding of hoya sd-2 to a silicon wafer, a high voltage creates a depletion layer at the interface. This creates a strong chemical bond that resists environmental degradation and high pressures.
The absence of alkali metals like sodium prevents contamination of sensitive electronic circuits on the die.
Thermal Matching
Precise control over the coefficient of thermal expansion ensures that the bonded assembly remains stable during subsequent processing steps. Because hoya sd-2 mirrors the expansion of silicon at approximately three parts per million per degree Celsius, it prevents the wafer from bowing or cracking. This alignment is verified by dilatometry during the manufacturing of the glass melt.
Stable thermal properties allow the finished sensor to maintain its calibration under extreme temperature shifts.
Optical Quality
Surface finish and flatness are maintained at sub micron levels to ensure a uniform bond across the entire wafer area. Polished sheets of hoya sd-2 undergo rigorous inspection for pits and scratches that could cause leaks in a vacuum seal.