The only real commonality between chip resistors and chip capacitors is that the external metallising, by which the part is soldered to the board, is solder coated, and this coating usually lies on top of a nickel barrier layer. In other respects, the chip resistor or chip capacitor are totally different.
The first difference is that they are based on different materials: the chip resistor is made of alumina, fired at high temperature and essentially a structural ceramic on which the resistor is laid; the capacitor is made of a special-purpose electronic ceramic such as barium titanate, and that material forms the dielectric between the electrode of the capacitor. In other words, the capacitor dielectric is part of the circuit function, whereas the alumina is merely a support.
The chip capacitor has an internal laminar structure, built up of many layers of ceramic and metallising, which is sandwiched together before firing; the chip resistor is metallised using lower temperature processes and on the outside of the chip.
The protection given to the active elements in the case of the chip capacitor is the dielectric material itself, extra layers of which are used on the outside of the ‘sandwich’; for the chip resistor, the protection is usually a low-firing glaze applied to the surface after the resistors have been individually trimmed.
Also from the materials point of view, it is worth noting that the resistor chip is made as one of many, which are broken out before end terminations are applied, whereas each chip capacitor is an individual before the firing process. The nature of the ceramic, and the processes themselves, mean that chip resistors are essentially flat on the lower surface, whereas chip capacitors need not be – historically, small capacitor chips tended to look a bit like miniature rugby balls!
Author: Martin Tarr
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence.
Terms and conditions apply.