A question came in to us recently about the right electrically conductive plastic for pressure sensors, which we felt was worth answering publicly.
The minimum thickness suitable for pressure sensors is 4mil, but the 6-mil and 8-mil thicknesses are more common for pressure sensors.
Question for Pressure Sensors
The question that was asked was from a designer that was designing a fairly large pressure mat with a sensor matrix. He was trying to figure out the min/max/typical sheet resistance for our MVCF and VCF (Mid-Level Conductive Film vs Low-Level Conductive Film) products. The website and the datasheets have conflicting information. Also, he would also like to know what the variability of sheet resistance in a single roll is. Would the variability be lower when using thicker films?
Answer for Pressure Sensors
Although, we are a little embarrassed to admit it, he was right. Over the past 6 months, we have been updating and rec-classifying our range of volume-conductive sheeting. The reason for this is because our customers have asked for more specific conductivity ranges with tighter tolerances. You can read the post here that talks about tighter specifications on LINQSTAT volume-conductive plastic for more details.
As a result of this, we have just updated our LINQSTAT Conductive Plastic Sheeting Overview page, which has the most current information. All the information on the website and in the technical datasheets has been updated to reflect this information.
As far as the variability goes, it is about 10% roll-to-roll due to the distribution of conductive filler, but is independent of the thickness. (the volume resistivity however is of course thickness dependent). Where the thickness plays a role and is particularly important for pressure sensor applications. The thinner sheets are less sensitive to pressure changes than the thicker ones (because essentially by reducing the thickness, you increase the conductivity). The minimum thickness suitable for pressure sensors is 4mil, but the 6-mil and 8-mil thicknesses are more common for pressure sensors.
I am not sure whether you need the 50,000 ohms per square or 10,000 ohms per square product for your application, but typically the larger the pressure sensor, the less conductive the film needs to be. You could still use the more-conductive material, but then you are paying for conductivity that you don’t necessarily require.
CAPLINQ is a specialty plastics supplier offering a range of LINQSTAT branded conductive materials including our broad range of electrically conductive plastics and antistatic tapes and films. If you have any questions, please don’t hesitate to contact us if you have further questions on using conductive plastic for pressure sensors.