Study On The Characteristics Of Ni Electrode Paste And The Applications In Multilayer PTCR

To meet the development needs of miniaturization, lightweight, high performance and low power consumption of electronic devices, multilayer PTCR came into being. As"one of the multilayer chips that most difficult to be realized in the world", many technical problems need to be solved in the preparation of multilayer PTCR. In the paper, Ni inner electrode paste used in multilayer BaTiO₃ based PTCR prepared by reducing-reoxidation and co-firing process was investigated.Ni pastes were made from Ni powder with different particle size of 0.2μm, 0.6μm and 1μm. First, the properties of Ni powder of different particle size were studied. On the basis of previous study, the effect of particle size of Ni powder on the characteristics of Ni paste was discussed, including sintering characteristics, ohmic contact performance, resistance against oxidation, electrical conductivity and shrinkage of electrode; the effect of particle size of Ni powder on the properties of multilayer PTCR was investigated.In the paper, Ni pastes mentioned above were used as inner electrode in multilayer PTCR, and the influence of oxidation of Ni inner electrode on the characteristics of PTCR ceramics was studied. The results are as follows: when heat treatment temperature is above 800℃, Ni electrode was oxidized that the ohmic contact of Ni electrode with ceramics was broken, and the room temperature resistivity of multilayer PTCR increased but lift-drag ratio decreased.In order to improve the interface match of metal inner electrode with ceramic layers, 5% BaTiO₃ was added to Ni paste. It's observed that sintering starting temperature of Ni electrode increased, and sintering shrinkage rate was reduced, moreover, the room temperature resistance of multilayer PTCR decreased and resistance jump was not affected.The influence of the particle size of Ni powder used as inner electrode in multilayer PTCR on the electrical properties of the components was studied first in the paper. When Ni paste added with BaTiO₃ was used as inner electrode, the room temperature resistance was 4.5 ?, and resistance jump reached 3.7 orders.