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Q:

What is the difference between PME and BME Ceramics?

A:

Sometimes when looking on a datasheet for Ceramic Capacitors you might see references to the terms”PME” and “BME”?  What do these mean and why should you pay attention?  These acronyms are describing the metals used for the electrode plates.

Definitions

BME stands for “Base Metal Electrode” while PME stands for “Precious Metal Electrode.”  This means PME typically uses metals like Palladium-Silver (PdAg).  BME, on the other hand, will use less expensive metals like Nickel or Copper.  Nickel is the most common while Copper may be used in specialized capacitors like KEMET’s CBR Series which are RF Ceramic Capacitors.  Copper has similar conductivity to Silver-Palladium without the extra cost.

RoHS

Cost isn’t the only reason to give consideration to PME or BME.  Another reason refers to RoHS Compliance.  In order to manufacture a PME ceramic with Palladium-Silver, the dielectric material will have Lead(Pb) added to it.  BME ceramics, on the other hand, do not.  All PME capacitors, that I know of, are inherently not RoHS compliant.  While all BME, at least from KEMET, are RoHS compliant.

For example, KEMET’s line of Commercial C0G, X7R, X5R, Y5V, and Z5U ceramic capacitors are all BME and RoHS compliant.

Added on:

Monday, August 17th, 2015