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Lower X7R Ceramic capacitors sintering temperature

Author: YangFengChun
Tutor: WuMengQiang
School: University of Electronic Science and Technology
Course: Electronic information materials and components
Keywords: PME-MLCC BaTiO3 modification mechanism low-temperature sinter
CLC: TM534.1
Type: Master's thesis
Year: 2008
Downloads: 143
Quote: 2
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Abstract


Ceramic multilayer capacitors （MLCC） are one of the most important electronic components at the surface mounting of electronic circuits. The expensive precious metals such as Pd or Ag/Pd are utilized as internal metallization in MLCC, which can be sintered in the air. We should decrease the amount of Pd in internal metallization to achieve a substantial cost saving, for Pd is much more expensive than Ag. If MLCC is sintered at lower temperature, the amount of Pd in internal metallization can be reduced, and the cost is fewer. In this thesis, novel materials and process are explored and investigated to reduce the sintering temperature of X7R ceramic capacitor.Following are the main results:The effects of metal （Zn） on the microstructure and dielectric properties of BaTiO3-Nb2O5-ZnO system are investigated in detail. The ceramics can be sintered at 980℃, because the intenerate temperature and melting point of Zn is low. Dielectric constant of Zn doped BT ceramics is rapidly increscent, and capacitance variation rate of Zn doped BT ceramics is worse as the amount of Zn is increased. It can be explained by filter theory and principle of stabled proportion.The effects of CuO on the microstructure and dielectric properties of BaTiO3-Nb2O5-ZnO system are investigated in detail. The ceramics can be sintered at 950℃, because the intenerate temperature and melting point of CuO is low. There will be much glass matter at lower temperature. The effect of CuO doped BT ceramics is not very great.By adjusting the amount of the composition of BT ceramics （MnCO3, CBS, ZnO）, dielectric constant of BT ceramics is greater(ε=2878, TCC125℃=-3.4). The effects of composition （MnCO3, CBS, ZnO） of BaTiO3-Nb2O5-ZnO system are investigated in detail, and greater dielectric constant is achieved by reducing or taking out the amount of the composition of BT ceramics.The capability standards of X7R ceramic capacitor are met by adjusting the sintering process. As the sintered speed is changed, the BaTiO3 cell size is changed. So the dielectric constant of BT ceramics is changed and the capacitance variation rate of BT ceramics is changed reverse. Finally, the best sintering time （2h15m to 2h20m） is confirmed. The cost of the BT ceramics is about 64% of BT ceramics sintered at 1080℃, The capabilities of X7R ceramic capacitor are:ε≥2700 ,ρ≥1011Ω·cm , tgδ≤1.0% ,△C/C25℃（-55℃-+125℃）≤±15%

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CLC: > Industrial Technology > Electrotechnical > Electrical > Capacitor > Inorganic dielectric capacitor > Ceramic dielectric capacitors
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