The Optimisation of Carbon and Silver Inks for Low ESR Tantalum Capacitors

摘要

There is a continual demand to lower the ESR (Equivalent Series Resistance) of both polymer and manganese dioxide based tantalum capacitors. Optimisation of the carbon and silver ink formulations to achieve good wetting and corner / edge coverage of the cathode layers is an essential part to produce the necessary intimate / ohmic contact. These layers also have to exhibit good thermal stability and bond strength during the manufacture and surface mounting of the tantalum capacitor. This paper describes the key features of the carbon and silver inks. The interactions of the carbon ink onto the dielectric and subsequent silver ink on the carbon during the fabrication of the tantalum capacitor will be discussed. Characterisation of these inks will be explained using wetting angle measurements, thermal stability analysis and interfacial bond strengths on the anodes. The role of the silver flake / carbon, resin and solvent systems in the ink to achieve optimal performance will be highlighted. Recommendations on the ink properties will be given to produce low ESR tantalum capacitors.