Failure behavior of tantalum electrolytic capacitors under extreme dynamic impact: Mechanical–electrical model and microscale characterization

Abstract

Tantalum electrolytic capacitors have performance advantages of long life, high temperature stability, and high energy storage capacity and are essential micro-energy storage devices in many pieces of military mechatronic equipment, including penetration weapons. The latter are high-value ammunition used to strike strategic targets, and precision in their blast point is ensured through the use of penetration fuzes as control systems. However, the extreme dynamic impact that occurs during penetration causes a surge in the leakage current of tantalum capacitors, resulting in a loss of ignition energy, which can lead to ammunition half-burst or even sometimes misfire. To address the urgent need for a reliable design of tantalum capacitor for penetration fuzes, in this study, the maximum acceptable leakage current of a tantalum capacitor during impact is calculated, and two different types of tantalum capacitors are tested using a machete hammer. It is found that the leakage current of tantalum capacitors increases sharply under extreme impact, causing functional failure. Considering the piezoresistive effect of the tantalum capacitor dielectric and the changes in the contact area between the dielectric and the negative electrode under pressure, a force–electric simulation model at the microscale is established in COMSOL software. The simulation results align favorably with the experimental results, and it is anticipated that the leakage current of a tantalum capacitor will experience exponential growth with increasing pressure, ultimately culminating in complete failure according to this model. Finally, the morphological changes in tantalum capacitor sintered cells both without pressure and under pressure are characterized by electron microscopy. Broken particles of Ta–Ta2O5 sintered molecular clusters are observed under pressure, together with cracks in the MnO2 negative base, proving that large stresses and strains are generated at the micrometer scale.