Benefiting from the electrochemical impedance spectroscopy (EIS) technique, the capacitor reliability under different corrosion states is also evaluated in a detailed manner. This work offers great value both in electronic corrosion mechanisms and future rational design for reliable IEDs.
For all capacitors under 3 V, corrosion products initially form on the capacitor surface due to relatively slow ion transport to the cathode, where ions will combine with OH − to first form corrosion products and in turn lead to a certain degree of ion depletion in the process of migration.
The continuous reduction in capacitor size makes the newer base metal electrode capacitors more vulnerable to moisture degradation than the older generation precious metal capacitors. In addition, standard humidity life testing, such as JESD-22 THB and HAST, will likely not uncover this problem.
The report of Hillman and Helmold proved that the cause of the failed capacitors was a faulty electrolyte mixture used by the Taiwanese manufacturers, which lacked the necessary chemical ingredients to ensure the correct pH of the electrolyte over time, for long-term stability of the electrolytic capacitors.
Generalizing capacitance degradation from exposure to room temperature with 100% relative humidity, to 85 °C with 85% relative humidity and to autoclave environments The average capacitance degradation data can be combined to describe capacitance degradation across temperature ranges.
Although several factors (i.e., contaminations, humidity, temperature) are proved to be the parameters closely related to ECM susceptibility of capacitors on a PCB under climate environments, further targeted research under other environments still needs to be conducted as ECM is highly environmental-dependent.
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The capacitor plague was a problem related to a higher-than-expected failure rate of non-solid aluminium electrolytic capacitors between 1999 and 2007, especially those from some Taiwanese manufacturers, due to faulty electrolyte composition that caused corrosion accompanied by gas generation; this often resulted in rupturing of the case of the capacitor from the build-up of pressure.