Piezoresistive sensor elements for the measurement of pressure, force or strain

Medical technology requires high precision, stability and reliability. The principle of piezoresistive pressure sensor chips from CiS Forschungsinstitut für Mikrosensorik GmbH can be used for force measurement in silicon strain gages.

The strain-sensitive resistors are monolithically integrated into wafer-thin chips as wheat-stone measuring bridge. With the technologies the Thuringian research institute wants to support companies in their product development, possibly for haptic catheters in surgical instruments or force sensors for dentistry and dosing pumps in infusion and dialysis technology.
 

The semiconductor technologies used ensure high long-term stability, resolution and measurement reliability. The chip design significantly reduces transverse expansion sensitivity, which is an advantage when mechanical stresses in a target have to be analyzed. If a sensor is to withstand high temperatures, a silicon-on-insulator substrate is used for production instead of silicon. Function and reliability of the microchip can then be achieved even at temperatures up to 300°C.   
 

The DMS chips, which are only 0.5 mm x 0.5 mm x 0.5 mm x 0.015 mm in size, are connected to the elastic deformation body, such as stainless steel, titanium or aluminum, by pick & place and joining techniques tailored to the application, after they have been diced. Traditional bonding methods are often not usable in medical technology, as the materials used are sensitive to temperature and humidity, thus influencing the stability of the electrical signal.

Assembly technologies such as glass soldering, silver-sintering or joining on the basis of reactive multilayer systems are pioneering here. The selection of the appropriate method depends on the requirements for the measuring system and the conditions at the measuring point. CiS carries out the necessary tests on the thermal behavior of the material components and the reliability and long-term stability in-house. 

 

Contact: Uta Neuhaus, CiS Forschungsinstitut für Mikrosensorik GmbH

uneuhaus@cismst.de