PACKAGING OF MICROFABRICATED DEVICES AND SYSTEMS

All devices and systems need to be packaged for applications. For microfabricated devices or systems the packaging is an essential part of the design, not an after-thought. The functions of packaging are: (i) to protect the devices from the environment, and (ii) to protect the environment from the device operation. At present, there is no generally applicable packaging method for all microdevices, but there are basic principles useful in packaging design. This article outlines the fundamental requirements, design considerations, and packaging techniques for sensors and microsystems, with selected examples, and suggested references. The protection of the device includes: (i) electrical isolation and passivation of leads and device structures from the penetration of moisture and ions; sealing techniques and hermeticity measurements are important aspects; (ii) mechanical protection to ensure structural integrity and dimensional stability; (iii) thermal and optical isolation, and (iv) chemical and biological isolation and protection. It is also necessary to protect the environment from the device materials and device operation, so that no undesirable reaction with or contamination of the environment occurs. This is especially important for devices used in biomedical, pharmaceutical and food processing. Biocompatibility and contamination must be considered as factors in the design. Successful packaging design requires the integration of knowledge of materials, device characteristics, packaging and evaluation techniques. It remains as a challenge in the MEMS field for engineers.