How to get rid of vibration problems for electrolytic capsFollow article
Due to their large mechanical structure and weight, aluminium electrolytic capacitors are sensitive to any mechanical vibration within the application. In the side diagram, you can see the winding element A, which is connected to the solder terminals C via some small aluminium strips (also called tabs) and marked as B. The tabs experience normal mechanical forces during vibration testing in the manufacturing process. But they can also see torque due to rotational forces.These types of normal mechanical stress on the tabs can result in a complete tear across the tab and a resulting open-circuit in the capacitor.
For this reason, IEC has defined standard vibration tests for electrolytic capacitors. The cans of the device are clamped to a vibration frame (E) and subjected to forces in two or three perpendicular directions, with a typical amplitude of 0.75 mm and acceleration of 10 g. These tests have predictive power for movement of the winding relative to the can (D), meaning the stiffness of the internal construction. But they do not say anything about what could occur when the PCB material is too weak, or in the case of resonances.
Improvements to the internal robustness of the capacitor can be made by providing a more rigid axial or radial fix for the winding element. Some Vishay series improve the vibration sensitivity capability up to 50 g, which is five times the requirement of the IEC test.
During vibrations, the heavy parts could easily break loose from the PCB. Therefore, care has to be taken in regards to PCB thickness and fixation of the capacitor to the board. Relatively unknown is the appearance of resonances during vibrations. Cases have been reported in which the actual measured vibrational accelerations at the capacitor location gained up to a factor of 50 relative to the pre-set test conditions.
Therefore, care has to be taken in regards to the rigidness of the construction around the capacitor area on the PCB, e.g. with the help of screws to fixate the PCB to the housing. Here, the use of damping material between the PCB and housing could also help to prevent the appearance of resonances.