Glassed-on silicon strain gauge on steel
For precision force measurements, the CiS Research Institute has developed miniaturised silicon strain gauges (Si-DMS) with integrated measuring bridge. The piezoresistive resistors are monolithically integrated in single-crystalline silicon (K-factor = 80) and are available as a double strain element and as a full bridge. By using semiconductor technologies, a higher long-term stability, precision and measurement reliability is achieved compared to ductile metal strain gages.
The temperature coefficient of the bridge is 0.70 % / 10 K. The resistance of the bridge at 30 °C is 5000 W and the sensitivity is 0.4mV/(VMPa).
The Si strain gauges, which measure only 1.0 mm x 0.5 mm x 0.015 mm, are joined to the elastic deformation body using innovative joining techniques.
Classical bonding methods are often not usable for demanding applications, such as industrial sensors and medical technology, because the joining materials used for this are sensitive to temperature and humidity and thus influence the stability of the electrical signal.
Assembly technologies such as vitrification, silver sintering or joining based on reactive multilayer systems are leading the way here. The selection of the appropriate process depends on the requirements of the measurement system and the conditions at the measurement location. CiS conducts investigations on the thermal behaviour of the material components and the reliability and long-term stability of the Si strain gauge on spring bodies made of stainless steel, Kovar, aluminium and other metals.
Project presentations at:
electronica, 08-11 November 2016, Munich, Hall B1, Booth 225
COMPAMED, 14-17 November 2016, Düsseldorf, Hall 8A, Booth H23.1