MSS Bi-Face^TM Technology The MSS Bi-FaceTM Technology is based on a substrate which integrates hermetic vias allowing to interconnect the sensors side to the electronic one.
It is made of a hydrophobic material processed by the injection of polymers in the substrate in order to maintain insulation at 100%RH.
The sensor side is made up of the base electrode built in the substrate and connected to the electronic, allowing to avoid any contact with condensation, parasite’s deposits or anyhting that could cause isolation problems and thereby damage measurement under severe environemental conditions. The sensor side doesn’t show any ruggedness or asperity , indeed extra thin layers (total thickness 1µm) of polymer cover it.
Moreover it is processed in order to have an homogeneous sliding coefficient . The electronic side is developed as an electronic circuit allowing to design any electronic function.

The polymer is the sensitive part of the sensor, its permittivity varies with the humidity rate.
The originality of the UPSI’process consist of building the dielectric in 4 layers in order to enhance relashinship between the polymer and the base electrode. It guarantees the functionning of the sensor at high humidity rates and improves its long term stability. The layer’s modulation varies from 1 to 100.
The product has a multi layer structure. The last operation of the process consist of melting the several layers in order to reach a unique one, allowing to enhance the products yield and lead to highly performant resulst.

The porous electrode also acts as a second electrode. Indeed, its two main purposes are: On the one hand, an electronic duty: to act as an electrode, on the other hand, a physical role: to be porous in order to let the water vapor through.
It enables the sensor to adapt to the ambient climate.The electrode is made up of the same polymer as the dielectric ( allows porosity) blended with conductive elements (enables conductivity).
The porous electrode is connected to the ground of the electronic circuit, thereby it creates an electrostatic shield for the sensor and enables, combined to the active electrode’s fitting, to avoid problems of isolation loss even in a satured atmosphere .
The electrode’surface has been studied to reduce its surface by abrasion.

Calibration is made by abrasion of the electrode’surface. Indeed the capacitive value of the sensor depends on the porous electrode’ surface, thus by reducing it, we are able to fit the sensor in order to correct manufacture variations due to the polymer’s thickness, the porous electrode’s position or again the electronic dispersions.