Low-stress 3D packaging of a microsystem

The field of microsystems has in recent years attracted huge interest. Advances in micromachining have allowed the development of microfluidic components such as pumps, valves and flow channels. However, the packaging of microsystems, particularly microsensors, has proven one of the biggest limitations to their commercialization. This paper describes the 3D packaging of a microsystem demonstrator with sensor applications from the Esprit project BARMINT. Central to the operation of the 3D demonstrator is a micromachined silicon membrane pump to supply fluids to a sensor chamber over a universal sensor chip carrying ISFET-based chemical sensors, pressure and thermal sensors. The electronics required for controlling and regulating the activity of the sensors is also available on this chip and as other chips within the assembly, which also contains a power-supply module. Costs are minimized by use of standard off-the-shelf components. In addition, consideration is given to the need to minimize packaging-induced stresses on the delicate membranes and structures involved in the system, and the packaging approach described herein is compared, from a stress-minimization viewpoint, with previous and alternative approaches from within the project. (C) 1998 Elsevier Science S.A. All rights reserved.