What is a ceramic disc capacitor?

A ceramic disc capacitor is a capacitor constructed with a ceramic disc as the dielectric. You'll recall that the basic definition of a capacitor is two conductors separated by an insulator (dielectric) of some kind. As a charge is driven onto one plate of a capacitor, the extra charge there builds up an electric field. Each charge arriving on one plate forces a charge off the other plate. Charge (and, therefore, voltage) builds. Let's build one to see how it works.

Imagine a thick coin of some kind, but made of ceramic. You will (of course) have a ceramic disc. If you coat each face with metal and attach a lead to it, you'll have the basic construct. Note that the edges of the disc are left uncoated, and the two faces, which are conductive now, are insulated by the disc. Just dip the capacitor into a phenolic or epoxy to coat it and it's ready to go, except for the labels.

These caps are used in tuning or decoupling applications in RF circuits. And the leads are a dead giveaway to their through-hole use. Crimped or straight leads, please? Use the link below to view some pictures, and all this will make a lot more sense.