Die-level glass frit vacuum packaging for a micro-fuel processor system

Abstract

Vacuum packaging utilizing glass frit is investigated for the use with a micro-fuel processor. Enhanced device performance through proper thermal management motivates the need for a vacuum package on the micro scale. Constraints imposed by the design and fabrication of the micro-fuel processor deem glass frit bonding as the optimal method for packaging. The quality of the glass seal is dependent on the pre-sintering process as well as bonding parameters. Ideal pre-sintering of a lead-zinc-borosilicate glass tape, GPR-10 from Vitta Corp., has been achieved, and a vacuum bonding technique was optimized. The seal quality is determined visually with microscopy by comparing the size and quantity of voids present in the frit layer post-bonding. A package with a vacuum of <150mTorr was obtained but the seal quickly degraded. A new packaging scheme utilizing a two-step bond process is developed and evaluated. Bond optimization is applied to this process resulting in a hermetically sealed package. Hermeticity was not lost after heating the package at 450⁰C for 30+ hours. Final seal-off in a vacuum chamber was attempted with glass powders, glass preforms, and solders to no avail but preliminary results with solder appears promising.

(cont.) Despite unsuccessfully producing a vacuum package, the methodology for optimizing bonding parameters can be utilized for glass frits that possess different physical properties from GPR-10. The two step process developed is quite versatile and permits the use of bonding technologies that was considered incompatible previously. There is confidence that a vacuum package can be achieved if the additional work described is conducted.