One of the essential processes shared by many microelectromechanical systems (MEMS) is packaging. Packaging is a less-explored aspect of a microsystem, but can significantly affect overall device performance and cost. To minimize damage to the final microdevice, new packaging technologies that can be applied at the wafer level, before the device is separated from the host wafer, have gained much attention. Bonding methods are commonly utilized in packaging processes to achieve a hermetic seal between the package and the substrate.
Researchers at the University of Michigan have developed a process for bonding an insulator to eutectic solder using field-assisted bonding, also known as electrostatic or anode bonding. The process consists of placing a molten solder in close surface contact with an insulator element, heating the insulator element to render it electrically conductive, followed by application of a potential across the solder and the insulator element to create an electrostatic field, which chemically bonds the molten solder to the insulator element. Significant improvement in bond quality, uniformity, and reproducibility has been achieved via application of an anodic bias in a standard eutectic bond.
Applications and Advantages
- MEMS devices- optical/wireless radiofrequency-nl-communication systems, bioMEMS
- uniform, intimate contact between the solder-nl-and glass over large areas
- instant and contiguous planarization over-nl-non-planar substructures
- biocompatible bonding materials
- eutectic solder does not outgas-nl-(including in vacuum enclosures)