Design and Fabrication of Commercial Grade High Voltage Multilayer Ceramic Capacitors
Multilayer ceramic capacitors (MLCCs) are typically manufactured as follows:
First, stirring and mixing dielectric ceramic powders with a binder and a dispersion agent in a ball mill for several hours to prepare slurry having a desired viscosity.
Next, a green sheet is prepared by a doctor blade method, wherein, the slurry is discharged onto a carrier film through a small orifice and the carrier film is pulled under a doctor blade or a slot die, which is set at a particular height to obtain a desired sheet thickness. The sheet is then dried to produce the green sheet.
Then, a conductive paste is applied on a number of green sheets to form internal electrodes by screen-printing. The desired number of ceramic green sheets with internal electrodes are stacked and compressed to form a laminated body. The laminated body is then diced into a number of capacitor elements having a predetermined size. Thereafter the capacitor elements are through binder burnout and sintered then finally external electrodes are formed on opposite end portions of each of the capacitor elements to produce multiplayer ceramic capacitors.
Once terminated, MLCC is typically electro-plated with a layer of nickel followed by a layer of tin in order to be surface-mountable. Surface mounting is soldering of components onto PCBs. The nickel layer is typically referred to as the barrier layer. Although nickel is solderable, it does not readily dissolve in molten solder as silver does. The end terminals when the capacitors are soldered to PCBs. Tin coatings serve to protect the nickel from oxidation and to make components readily solderable.
Precious metal electrode (PME) system and solvent base are introduced in this report. Capacitors were fabricated from 22£gm thick tapes consisting of ceramic powders (X7R AD292U, Degussa Corporation and NP0 VLF-220, MRA Laboratories, Inc.) that involves a sequence of a large number of processing steps, with production losses associated with each step. Optimized and controlled processing parameters can get reliable yield.
Advisor:Wen-Hsi Lee; Cheng-Fu Yang; Ying-Chung Chen; Chih-Yu Huang; Fu-Thang Shiao
School:National Sun Yat-Sen University
School Location:China - Taiwan
Source Type:Master's Thesis
Keywords:x7r np0 pme high voltage mlcc
Date of Publication:01/29/2007