Low profile open MEMS and ASIC packages manufactured by flexible hybrid integration in a roll-to-roll compatible process
Here we report on a flexible, foil based packaging process in which a standard commercially available MEMS capacitive air pressure sensor is packaged in an open package configuration such that the sensitive membrane side of the MEMS is always in contact with the ambient atmosphere. Additionally, the matching ASIC chip to readout the MEMS sensor is integrated into the same package in a System-in-Foil (SiF) configuration. Here, both the MEMS and the ASIC wafers were thinned down to 250 m 250 mm, which resulted in a combined package height profile of <0.5 <0.5 mm. This foil based patch sensor has then been characterized in ambient air and its performance has been compared against a commercial MEMS (bare die) sensor available as standard Surface Mounted Device (SMD) component having a package height of 1 mm. The electrical performance and the functionality under thermal cycling and thermal shocks of these packaged sensors were found to be identical to the commercially available SMD variant. Furthermore, to demonstrate the applicability of such a thin, flexible foil sensor patch in the field of non-invasive air pressure measurements on planar and curved surfaces, these sensors were mounted onto the carrosserie of a car at different locations and the air pressure change due to the laminar / non-laminar flow of air (or air turbulence) over these control surfaces were measured. The results further verify the need for such low profile packaging such that the airflow over control surfaces can be measured without disturbing the laminar airflow. This opens up the application field of these packaged sensors for wind turbines, aircraft wings, skyscrapers/buildings and automotive applications.