Polymer Thick-film Piezoresistive Sensor Integrated into the PCB

Abstract

This article discusses the development of a simple force, pressure, or deformation sensor that can be integrated into printed circuit boards (PCBs) using polymer thick-layer pastes (PTF) as the sensing element. The piezoresistive effect of PTF pastes, including ED7500 with/without addition of dielectric paste and ED5020 carbon paste, was evaluated for sensitivity and hysteresis under compressive and tensile stress. The sensing element of the sensor is based on the piezoresistive phenomenon in the PTF resistor layer, where a bridge connection is used to measure the change in electrical resistance of a deformed element. The flexibility of lamination in PCB production is utilized to create a sensor with a membrane made of FR4 (by milling the glass-epoxy material) or polyimide material. Overall, the results indicate that this approach provides a relatively inexpensive solution for undemanding applications that do not require precise strain gauge measurements, such as pressure or force.