2022 Volume 130 Issue 8 Pages 686-690
Effect of thermal radiation on reliability is investigated for ZnO-based multilayer ceramic varistors (MLCVs). Withstanding capabilities against load dump surge (LDS) are compared between MLCVs with connecting structure of various-sized chips (co-MLCVs) and large size ones (5.7 × 5.0 × 3.0 mm). The LDS stability are improved with surface area of co-MLCVs. In particular, when connected chips are under 3.2 × 2.5 × 1.6 mm in size, co-MLCVs have more 30 % higher withstanding voltage (>100 V) and current (>53 A) than those of conventional large MLCVs, despite the same electrode area and nonlinear V-I characteristics. The results of thermal simulations show that heat dissipation in co-MLCVs is improved due to an expansion in surface area with a decrease of chip size. Thus, this notable enhancement of stability should be caused by an increase of heat radiation. And more, the LDS capability is independent of variation coefficient in V1mA of chips (e.g., as σ/x < 0.032). It is evident that improvement of radiation performance gives a significant increase in reliability of MLCVs. The high thermal radiation certainly leads to further advance in MLCVs for high-energy surge.