Mechanism of glass-frit fracture in MEMS packaging

Micro-electro mechanical systems (MEMS) are an emerging technology that may fundamentally affect every aspect of our lives. They are devices and machines fabricated using techniques generally used in the microelectronics industry and the next decades will see the incorporation of new types of functionality onto the chip with the rapid improvement of processing techniques. The small scales of MEMS offers the opportunity to exploit materials which would not normally be available for large scale devices as well as taking advantage of scale dependent properties, particularly yield and fracture strength. All MEMS product face the challenge and expense of packaging the product. Wafer bonding is widely used in MEMS to create cavities and glass frit bonding is a widely used technology for the hermetical encapsulation of MEMS. In this paper we will mainly focus on the instant failure of the bonding material and the influence of molding pressure induced stress on the strength of the bonding layer at the molding temperature. At the same time, the detailed numerical simulation will be generated with the consideration of the copper trace pattern, solder mask opening and solder mask protrusion from the real circuit drawing file. Finally, the effect of substrate design on glass-frit crack is considered by comparing the stress distribution on glass-frit with two different substrate designs.