Bonding properties of metals anodically bonded to glass

Abstract

Anodically bonded Pyrex-/Metal double stack were investigated for applications in the sensor encapsulation field. The use of metals can increase the robustness of the packaging and eliminate the use of glue. Titanium anodically bonded to glass can lead to biocompatible systems The anodic bonding of metallic sheets of Invar, Kovar, Alloy 42 and titanium to ion-containing glasses, Pyrex and Foturan, was evaluated in terms of samples preparation, bonding parameters, and bonding characteristics. At a bonding temperature below 300 • C, the stress induced to Pyrex was smaller when the Invar was used, however, a weak bonding was obtained at the lowest bonding temperatures investigated. In comparison with Invar and Alloy 42 bonded to Pyrex, Kovar induced a smaller stress for bonding temperatures higher than 350 • C. For bonding temperatures in between 300 and 350 • C, a similar value of stress was obtained for Kovar and Alloy 42 bonded to Pyrex as well as a high bonding strength. A post-annealing step at a temperature of and higher than the bonding temperature was shown to decrease the bonding stress and can be used to improve the bonding strength of samples bonded at low temperature. Kovar and Alloy 42 bonded to Pyrex at temperatures of and higher than 250 • C were tight to liquid at a pressure of 1.5 bars. In the case of titanium, Pyrex and Foturan were successfully bonded to titanium thin films and sheets, respectively. A proper selection of metals and bonding parameters led to levels of residual stress, strength and tightness that make anodic bonding of metals to glass a suitable technique for the assembling and packaging of microsystems, for instance piezoresistive silicon sensors and microfluidic devices.

Microsensors for Microreaction and Lab-on-a-Chip Applications

“…Test: bathed in H2SO4+HNO3 mixture ----+ (Briand at al., 2004;Knapkiewicz at al., 2007;Dziuban, 2006). Two ways to integrate pressure sensors directly to the microreactor are possible.…”

Manufacture of microfluidic glass chips by deep plasma etching, femtosecond laser ablation, and anodic bonding

“…The mechanism of glass-to-glass bonding is similar to a conventional silicon-to-glass electrostatic bonding. Such bonding can only be achieved using interlayers (Ju et al 1998), and at least one intermediate layer such as amorphous silicon (Lee et al 2000;Wei et al 2004;Kutchoukov et al 2004, Berthold et al 2000, Lee et al 2001, polysilicon (Berthold et al 2000;Xue and Qiu 2005), silicon nitride, carbide or oxide or a combination of them (Berthold et al 2000), or a titanium thin film interlayer (Briand et al 2004;Mrozek 2009). With low temperature bonding, no appreciable flow of the glass occurs, hence enabling sealing around previously machined grooves, cavities, etc.…”

Micro-hotplates on polyimide for sensors and actuators

“…An aluminium film is patterned to define the heating element (750 m-wide) and the rim for the anodic bonding of the Pyrex cavity, used to store the paraffin, on the top side of a 50 m-thick polyimide sheet. Metal to glass anodic bonding was the technique chosen to fix the Pyrex chip on the polyimide hotplate [10]. To achieve at the same time the anodic bonding of the Pyrex chip on the Al rim and on the two interconnections of the Al heater, an Al line linking both structures has been added to the design to electrically connect them during the anodic bonding.…”