The Mechanism of Water Evaporation at the Vacuum Accelerated Bonding Interface

The bonding strength of hydro-catalytic bonding is influenced by multiple factors such as bonding solution parameters, curing time, and temperature. Curing at room temperature requires 4 weeks to complete the bonding process. While low-temperature heating can accelerate curing and shorten the time, it is not suitable for heat-sensitive precision devices. To address this issue, this study innovatively proposes a vacuum-assisted hydro-catalytic bonding method. By utilizing a vacuum environment to accelerate the escape of water from the bonding interface, and based on the Hertz-Knudsen equation, an ultra-high vacuum dual-chamber system combined with a quadrupole mass spectrometer is used to monitor water vapor pressure in real time (characterizing the water escape flux). This is complemented by a microbalance to measure sample weight loss (characterizing the amount of water escaped), and bonding strength tests to verify the process effectiveness. The results show that the water escape flux at the bonding interface is significantly higher under vacuum than under atmospheric pressure. After pre-bonding followed by 24 h of atmospheric curing and 4 h of vacuum treatment, the average bonding strength reaches 11.31 MPa, reducing the curing cycle from 4 weeks to 28 h, while meeting the requirements of heat-sensitive precision devices. The study confirms that vacuum is an efficient way to promote water escape at the bonding interface, and a modified H-K equation can describe its acceleration mechanism.