Sometimes when looking on a datasheet for MLCC Ceramic Capacitors you might see references to the terms"PME" and "BME"?These acronyms are describing the metals used for the MLCC Capacitor electrode plates
PME and BME MLCCs
Multilayer ceramic capacitors (MLCCs) consist of two materials—ceramic dielectric materials and metal electrode materials. The superimposed metal electrode layers and ceramic dielectric layers generate voltages with high electric fields, enabling the MLCC to regulate current flow and prevent electromagnetic interference between components. Two common electrodes are used in multilayer ceramic capacitors (MLCCs): noble metal electrodes (PME) containing palladium silver and common metal electrodes (BME) containing nickel or copper. These two electrode types have their own characteristics and have their respective fields of application in industrial applications.
Advantages of Traditional PME MLCCs
Palladium-silver (PME) electrode material is used in MLCC. PME provides robustness and long-term reliability of components. Its dielectric thickness meets military specifications MIL-PRF-55681 and MIL-PRF-123, which set stringent requirements for high reliability applications.
PME MLCCs are not negatively affected during the thermal sintering of the electrodes and dielectric materials of the MLCCs. To prevent oxidation of BME MLCCs during the thermal process of manufacture, engineers must create a suitable sintering atmosphere to help remove lubricants and reduce surface oxides, thereby protecting the MLCCs from oxidation. Although this method can prevent oxidation, it also reduces the insulation resistance.
Advantages of BME MLCC
BME is a newer MLCC electrode technology based on nickel and copper. Compared with PME MLCC, BME MLCC is more cost-effective and its economic value is widely recognized by the market. 99% of the world's second-class ceramic dielectric MLCCs are BME MLCCs. Under proper manufacturing conditions, BME MLCCs meet the same high reliability and performance testing requirements as PME MLCCs.
BME MLCCs have a more uniform microstructure (i.e., grains) to meet volumetric efficiency requirements—more electrodes and dielectric layers can be stacked within the structure, thus providing higher capacitance in a smaller package size. With the trend of smaller and smaller electronic products, small size has become its main advantage.
As mentioned earlier, the design requirements and manufacturing considerations of BME MLCCs raise some reliability concerns, but we can also find appropriate countermeasures to prevent component performance failures. Requirements like minimum dielectric thickness, for example, are standards based on performance studies. If the BME MLCC meets these criteria, the design team can be confident that a sudden failure of the component is avoided. Careful design deployment, such as avoiding excessive mechanical stress, also reduces the likelihood of failure.
As technology develops and more performance studies are accumulated, BME MLCCs are increasingly being adopted in high-reliability electronics applications.
PME and BME: Both have advantages
In today's electronics industry, we need these two different electrode technologies. PME MLCCs will bring full confidence in applications due to their long application history and proven high reliability; while BME MLCCs are relatively new technology, but their cost-effectiveness and size advantages make them more favored in commercial applications . Over time, we expect BME MLCCs to become more widely accepted as an option for high reliability applications.