冲击载荷作用下钽电容的电压瞬变特性及微观机理

为探究钽电容在冲击载荷作用下的失效机制，设计并开展了5组不同强度的钽电容水下爆炸冲击实验，研究了冲击载荷作用下钽电容的电压瞬变特性，通过漏电、充电电流变化分析了钽电容的失效模式，利用扫描电镜观察钽电容的微观结构，讨论了冲击载荷作用下钽电容的失效机理。结果表明：钽电容受冲击后发生短路失效，电压大幅度降低，在自愈完成后电压缓慢上升。随着冲击波超压的增大，钽电容失效的概率增大，钽电容失效的临界超压约为32 MPa。不同类型的电压变化对应不同的失效模式，包括击穿后瞬间自愈、击穿后缓慢自愈和多次击穿自愈。不同类型电压变化的初始漏电电流峰值有较大差别，Ⅰ类电流峰值为2.5~5 A，Ⅱ类为1~2 A，Ⅲ类为8~9 A，且峰值越大，峰宽越小。冲击载荷作用下钽电容的微观失效机理与其氧化膜的瑕疵相关，机理包括氧化膜中微裂缝扩展使得局部电场强度超过击穿场强造成击穿、氧化膜较薄区域下方的杂质及晶态膜突出形成导电通道、贯穿型裂缝形成后气体电离导致的击穿。

Voltage transient characteristics and microscopic mechanism of tantalum capacitors under impact load

To investigate the failure mechanism of tantalum capacitors under shock loads, shock experiments were conducted on tantalum capacitors using shock waves generated by underwater explosions with an electronic detonator. Five groups of experiments with different shock intensities were designed by varying the distance between the capacitor and the electronic detonator. The transient voltage characteristics of tantalum capacitors under different intensity shock loads were studied. The voltage variations of tantalum capacitors were explained based on the changes in internal leakage current and external charging current, and the failure modes of tantalum capacitors were analyzed. Scanning electron microscopy was utilized to observe the microstructure of damaged areas in tantalum capacitors and the micro-failure mechanisms of tantalum capacitors under shock loads were discussed. The results indicate that tantalum capacitors experience short-circuit failures after shocks, with a significant decrease in voltage initially, followed by a slow rise and self-recovery. As the shock wave overpressure increases, the probability of tantalum capacitor failure increases, with a critical overpressure threshold of approximately 32 MPa. Different types of voltage variations correspond to different failure modes, including instant self-recovery after breakdown, slow self-recovery after breakdown, and repetitive breakdown with self-recovery. Different types of voltage variations exhibit significant differences in the peak values of initial leakage currents, with the first type ranging from 2.5 A to 5 A, the second type ranging from 1 A to 2 A, and the third type ranging from 8 A to 9 A. Moreover, larger peak values of leakage currents result in narrower peak widths. The micro-failure mechanisms of tantalum capacitors under shock loads include the propagation of microcracks within the oxide film leading to excessive local electric field strength and breakdown, impurities and surrounding crystalline oxide film protruding to form conductive channels in the region of thinner oxide film, and the formation of through-cracks followed by gas ionization leading to breakdown.