User Guide for FSR Sensor

Page 10 FSR Integration Guide and Evaluation Parts Catalog
with Suggested Electrical Interfaces
FSR Usage Tips
The Do’s and Don’ts
• Do follow the seven steps of the FSR Integration Guide.
• Do, if possible, use a firm, flat and smooth mounting surface.
• Do be careful if applying FSR devices to curved surfaces. Pre-loading of the device can occur as the two
opposed layers are forced into contact by the bending tension. The device will still function, but the dynamic
range may be reduced and resistance drift could occur. The degree of curvature over which an FSR can be
bent is a function of the size of the active area. The smaller the active area, the less effect a given curvature
will have on the FSR’s response.
• Do avoid air bubbles and contamination when laminating the FSR to any surface. Use only thin, uniform
adhesives, such as Scotch brand double-sided laminating adhesives. Cover the entire surface of the sensor.
• Do be careful of kinks or dents in active areas. They can cause false triggering of the sensors.
• Do protect the device from sharp objects. Use an overlay, such as a polycarbonate film or an elastomer, to
prevent gouging of the FSR device.
• Do use soft rubber or a spring as part of the actuator in designs requiring some travel.
• Do not kink or crease the tail of the FSR device if you are bending it; this can cause breaks in the printed
silver traces. The smallest suggested bend radius for the tails of evaluation parts is about 0.1” [2.5 mm]. In
custom sensor designs, tails have been made that bend over radii of 0.03” (0.8 mm]. Also, be careful if
bending the tail near the active area. This can cause stress on the active area and may result in pre-loading
and false readings.
• Do not block the vent. FSR devices typically have an air vent that runs from the open active area down the
length of the tail and out to the atmosphere. This vent assures pressure equilibrium with the environment, as
well as allowing even loading and unloading of the device. Blocking this vent could cause FSRs to respond
to any actuation in a non-repeatable manner. Also note, that if the device is to be used in a pressure chamber,
the vented end will need to be kept vented to the outside of the chamber. This allows for the measurement of
the differential pressure.
• Do not solder directly to the exposed silver traces. With flexible substrates, the solder joint will not hold
and the substrate can easily melt and distort during the soldering. Use Interlink Electronics’ standard
connection techniques, such as solderable tabs, housed female contacts, Z-axis conductive tapes, or ZIF (zero
insertion force) style connectors.
• Do not use cyanoacrylate adhesives (e.g. Krazy Glue) and solder flux removing agents. These degrade the
substrate and can lead to cracking.
• Do not apply excessive shear force. This can cause delamination of the layers.
• Do not exceed 1mA of current per square centimeter of applied force (actuator area). This can irreversibly
damage the device.