A sheet impedance characterization for bound thin sheets of metal-coated microballoons has been investigated. The binder material is a urethane that can be made as thin as 1 to 2 mil. The microballoons are hollow ceramic spheres coated with 100 to 200 AA of silver that are 10 to 100 mu m in diameter. The dependence of sheet impedance on the volume fraction of the microballoons, the coating thickness, the microballoon diameter, and the binder thickness has been determined by measurements. Thus, a range of sheet impedances can be synthesized easily and inexpensively by appropriate specification of the raw design parameters.
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