Q: We are looking for a non-conductive screw with lower dielectric constant / dissipation factor to replace a steel screw (Tensile Strength 70kpsi) in one of our products.
So were trying to get to similar strength / properties to the steel screw to meet our torque requirements. Will a ceramic screw be a work?
A: Any polymer or ceramic will have a lower dielectric constant than steel. The question is what other properties do you need. Ceramics will certainly work for an electrically insulating point of view but will be very expensive and brittle. Depending on your application this option has to be evaluated carefully.
Generally speaking a good material to consider would be a PEEK Glass filled material. The carbon filed is electrically conductive so that probably will not work for your application. Glass filled PEEK screws are tough, strong and non-conductive. It will not be as strong as your steel fasteners, having a tensile around 28-30ksi, but if your application could accept that it would be a good choice.