Thermoelectric flow sensors on flexible substrates and their integration process

A thermoelectric mass flow rate sensor on a 10 µm thick polyimide foil and its integration process on planar as well as non-planar surfaces has been developed. Flow sensors, fabricated by MEMS technology, usually have a height which is directly coupled to the wafer thickness (typically 525 µm or 380 µm). They are not bendable and an integration process is always complex when steps in flow channels have to be avoided. A fabrication process has been developed where the functional layers were removed from the silicon substrate and transferred onto a 10 µm thick polyimide foil. The resulting flexible flow sensor has been integrated on different materials by means of flip chip mounting and tested on its electrical and mechanical characteristics. It could be shown that thermoelectric flow sensors on polymer foils have comparable characteristics to flow sensors on silicon substrates but higher diversity in system integration.

[1]  W. Benecke,et al.  Toward Flexible Thermoelectric Flow Sensors: A New Technological Approach , 2008, Journal of Microelectromechanical Systems.

[2]  M. Shikida,et al.  Characteristics of On-Wall In-Tube Thermal Flexible Mass-Flow Sensors , 2006, 19th IEEE International Conference on Micro Electro Mechanical Systems.

[3]  Wolfgang Nitsche,et al.  AeroMEMS polyimide based wall double hot-wire sensors for flow separation detection , 2008 .

[4]  W. Benecke,et al.  A high-temperature thermopile fabrication process for thermal flow sensors , 2005, The 13th International Conference on Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. TRANSDUCERS '05..

[5]  W. Lang,et al.  Temperature stability improvement of thin-film thermopiles by implementation of a diffusion barrier of TiN , 2009, 2009 IEEE Sensors.

[6]  J. Burghartz,et al.  Ultra-thin chip fabrication for next-generation silicon processes , 2009, 2009 IEEE Bipolar/BiCMOS Circuits and Technology Meeting.

[7]  C. Burwick,et al.  A Seamless Ultra-Thin Chip Fabrication and Assembly Process , 2006, 2006 International Electron Devices Meeting.

[8]  Yasuroh Iriye,et al.  Characteristics of on-wall in-tube flexible thermal flow sensor under radially asymmetric flow condition , 2007 .

[9]  Yasuroh Iriye,et al.  Experimental and theoretical study of an on-wall in-tube flexible thermal sensor , 2007 .

[10]  Walter Lang,et al.  Thermal flow sensor for liquids and gases based on combinations of two principles , 1999 .

[11]  J. Müller,et al.  Low power consumption thermal gas-flow sensor based on thermopiles of highly effective thermoelectric materials , 1997 .