The effects of sintering conditions and Ni powder size on the dielectric properties of a X7R multilayer ceramic capacitor

The effects of the Ni powder size and the sintering conditions on the electrical properties, especially in regards to the reliability, of a X7R multilayer ceramic capacitor (MLCC) possessing a Ni internal electrode and thin layers were investigated. This research also attempts to use a paste made from 200 nm and 400 nm Ni powder in order to compare the MLCC properties. The ceramic was sintered at the increasing temperatures of 1230 degrees C, 1250 degrees C and 1270 degrees C at a fixed heating rate of 60 K.minute(-1) which caused the internal electrode connectivity to decrease. The MLCC sintered at 1270 degrees C suffered from an Ni internal electrode contraction with an increased ceramic thickness. Conversely, the internal electrode connectivity was improved when the sintering temperature was fixed at 1270 degrees C with the heating rate being varied at 20, 40, and 60 K.minute(-1). The ceramic treated with dense sintering (1250 degrees C, 60 K.minute(-1)) had a 10% higher breakdown voltage (BDV) compared to less densely sintered ceramic (1230 degrees C, 60 K.minute(-1)). In addition, there was a decrease in the degree of internal electrode disconnection. Therefore, the high temperature insulation resistance (ER) voltage properties were fine for a relatively high sintering temperature and a good internal electrode connectivity. The best result was found for a sintering condition of 1250 degrees C, at 60 K.minute(-1). The effects on the capacity and breakdown voltage of the high temperature IR for different Ni powder sizes were tested. The MLCC using 200 nm Ni powder had a 2% larger capacity and a 60% higher internal resistance when compared to the MLCC using 400 nm Ni powder. The MLCC using 200 nm Ni powder had a high temperature IR value of 9 Vr and the one using 400 nm Ni powder had high temperature IR value of 5 Vr, both showing good high temperature IR values when the internal electrode connectivity was good.