A hybrid capacitive pressure and temperature sensor fabricated by adhesive bonding technique for harsh environment of kraft pulp digesters

Abstract

We have developed a compensated capacitive pressure and temperature sensor for kraft pulp digesters (pH 13.5, temperatures 25-175°C reaching a local maximum of 180°C and pressures up to 2 MPa). The gauge capacitive pressure sensor was fabricated by bonding silicon and Pyrex chips using a high temperature, low viscosity UV (ultraviolent) adhesive as the gap-controlling layer and heat curing adhesive as the bonding agent. A simple chip bonding technique, involving insertion of the adhesive into the gap between two chips was developed. A platinum thin-film wire was patterned on top of a silicon chip to form a resistance temperature detector (RTD) with a nominal resistance of 1,500 X. A silicon dioxide layer and a thin layer of Parylene were deposited to passivate the pressure sensor diaphragm and the sensors were embedded into epoxy for protection against the caustic environment in kraft digesters. The sensors were tested up to 2 MPa and 170°C in an environment chamber. The maximum thermal error of ±1% (absolute value of ±20 kPa) full scale output (FSO) and an average sensitivity of 0.554 fF/kPa were measured. Parylene-coated silicon chips were tested for a full kraft pulping cycle with no signs of corrosion.

Analysis of application status and development prospect of environmental chambers: A review

“…The temperature, humidity, pressure, gas concentration, illuminance and other parameters are adjusted according to the principle of the researched sensor, and the small-sized environmental chamber is the main method for this type of study. [102][103][104][105][106][107] According to various studies, the sensitivity, frequency range, stability, repeatability and other parameters should be fully considered when selecting sensors. When studying the performance of batteries, especially automotive batteries, small environmental chambers are often used to simulate extreme environments.…”

A simple thermo-compression bonding setup for wire bonding interconnection in pressure sensor silicon chip packaging

“…The packaging step is one of the biggest limitations to the commercialization of sensors as it can be the most costly part of the manufacturing process (Kim et al 2010;Xie et al 2010). Problems due to packaging can account for up to three quarters of all instances of failure of working parts (Fahrner et al 2001;Mohammadi et al 2011). Wire bonding interconnection is one of the important processes in fabrication of silicon pressure sensor (Burla et al 2009;Lellouchi et al 2010).…”

Single-chip solution for electronics unit of a smart pressure sensor

“…Chen and Mehregany (2007) introduced the all-silicon carbide (SiC) capacitive pressure sensor, which incorporates a SiC diaphragm on a SiC substrate to measure pressure in high temperature and harsh environments. Mohammadi et al (2010, 2011) have developed a capacitive pressure and temperature sensor for kraft pulp digesters. The sensor was tested in extreme conditions (up to 2 MPa and 170°C) and showed good results.…”