Interface separation phenomena during immersion in water of anodically bonded Kovar alloy–borosilicate glass joints with application of opposite polarity

• Published in: Sensors and actuators. A. Physical. Vol. 290; pp. 125 - 129
• Main Authors: Nishikawa, Satoru, Takahashi, Makoto
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.05.2019; Elsevier BV
• Subjects: Alkali ion accumulation layer; Alloys; Anodic bonding; Bonded joints; Borosilicate glass; Chemical bonds; CRTs; Direct current; Ferrous alloys; Glass; Interface separation; Kovar (trademark); Membrane separation; Opposite polarity; Polarity; Separation; Silicon; Sodium silicate; Sodium silicates; Water immersion; Sodium silicate; Alkali ion accumulation layer; Anodic bonding; Opposite polarity; Interface separation; Water immersion
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2019.03.020

[Display omitted] Schematic illustration of bond interface separation for anodically bonded Kovar alloy–borosilicate glass joint with application of opposite polarity and immersed in water. •Interface separation of anodically bonded joints is clarified.•Bonded joint treated with opposite polarity separated by immersion in water.•Water-soluble sodium silicate formed in the bond interface.•Shorter bonding time increased the rate of interface separation.•Longer application of opposite polarity increased rate of separation. Anodic bonding is a process for bonding metal to ion-conductive glass at a temperature below the glass softening point, where a direct current voltage is applied to the metal and glass with an anode and cathode, respectively. The bond interface was not immediately separated when opposite polarity was applied to anodically bonded Kovar alloy–borosilicate glass, however, the bond interface was separated after long-term exposure to air. Given that the bond interface was not changed after exposure to vacuum, it was suggested that water in the air caused interface separation. When opposite polarity was applied to the bonded joint, the concentrations of Na and Si in water after a water immersion test increased when compared with tests that did not use opposite polarity. Thus, it was considered that the water-soluble sodium silicate layer, which was formed in the bond interface by the application of opposite polarity, eluted into the water to cause interface separation.