Characterization of a bonding method for titanium-glass sealing
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Characterization of a bonding method for titanium‑glass sealing Sebastian Winkler1 · Jan Edelmann1 · Andreas Schubert1,2 Received: 15 May 2020 / Accepted: 9 November 2020 © The Author(s) 2020 OPEN
Abstract Applications for smart medical implants require hermetic and mechanically strong seals between functional and biocompatible materials. Hermetic seals between titanium Ti6Al4V and silica-based glass can be produced using a novel bonding method based on glass pressing at temperatures around the softening point. This paper presents investigation results for the tensile bond strength and the gas leak rate depending on the manufacturing process parameters. Notably, when using blasted surfaces, the tensile bond strengths reached 12 MPa and good adherence with very low leakage due to the removed oxide layer and surface structure. The interface is analyzed and characterized by applying SEM methods related to the different adhesion mechanisms. Keywords Glass · Glass-to-metal seals · Titanium · Hermetic seal
1 Introduction Glass-to-metal seals are required in numerous technological fields such as aerospace engineering [1], battery technology [2], and medical engineering [3]. Mechanical strength and sealing quality are the significant properties that determine the performance of glass-to-metal bondings. The glass material and the metal alloy must be biocompatible for applications in medical engineering. Implantable electronic devices such as pacemakers are encapsulated in order to protect the human body from potentially harmful substances. Titanium alloys combine mechanical strength with biocompatibility, making them the material of choice for most medical implants containing electronic systems. Figure 1 illustrates an implantable electronic system with a titanium housing. This implant contains an optical window for optical data communication with a control system located outside the body, as described in [4]. Other potential applications for optical windows are optical diagnosis systems. Silica-based glasses match the requirements for mechanical strength, biocompatibility, and optical transmission. Moreover, the
hermetic sealing between the titanium housing and the glass window is a crucial part of the encapsulation system (Fig. 1). Bonding of glass and metal is an old technology that can even be traced back to ancient Egypt, where decorative glass coatings were manufactured on metal surfaces. The technology applied for these coatings is based on glass melting and wetting of the metal surface, which was later referred to as enameling. Most industrial applications such as light bulbs or enameled cookware are produced by this common type of manufacturing process using high temperatures to melt the glass, allowing it to wet the metal surface [5]. Bonding of glass and titanium for medical and other applications is challenging and has been studied extensively [6–8]. Compared to the conventional glass melting approach, other bonding methods with low process temperatures have been introduced [9]. In the anodic bonding proc
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