Ceramic Capacitor Lifetime Calculation

Are there any methods for estimating the lifetime of a capacitor.

Ceramic capacitor lifetime calculation.

Typical accelerated test for ceramic capacitor is an accelerated test using temperature and voltage factors. The following equation 2 expressed by the applied voltage and the temperature is usually used to estimate the life. The alcap useful life calculation tool provides calculations of useful life for a selected capacitor type under application specific load conditions. The voltage applied to the capacitor.

There have been many reports until now describing that acceleration equation for ceramic capacitor conforms to eyring model. Simply put the law says that life of a capacitor doubles for every 10 degree celsius decrease in temperature within limits. For example if a ceramic capacitor has a code 5 and other has 47 their respective capacitance values are 5 pf and 47 pf. The relationship between life and temperature follows a chemical reaction formula called arrhenius law of chemical activity.

After determining the acceleration factor by the acceleration test at an arbitrary temperature and voltage the life can be estimated by putting your volage and temperature condition into the formula. If the capacitor code consist only 1 or 2 digits it is simply their capacitance value in picofarads pf. Where the combined thermal resistances in axial and in radial direction numerically range in the order of 4 ç û ü á æ ü ø1 3 ä ð. To calculate the failure of a cga2b3x7r1h104k capacitor assuming the customer uses the capacitor at 85 degree celsius and half the rated voltage 25v 60 confidence level with life test conditions 125 c 1 5xrv and 77pcs for 1 000 hours.

Ripple current spectrum or measured temperatures. In general the temperature of the hottest point on the capacitor should not exceed the qualifying temperature of the dielectric typically 125 0c. One unit of fit 1 x 10 9. Below is the equation to illustrate.

Here s a simple table of the multipliers you can use to do this calculation in your head. Please click on one of the series below in order to start the program. Every vendor models the lifetime impact of the voltage applied to a capacitor using a power law of the form where v a is the applied voltage and v r is the rated voltage. Next please specify the capacitor type and select the calculation method you want to use.

Considering the life of ceramic capacitors 1 the applied voltage and the ambient temperature greatly affect to it in general. Operating conditions directly affect the life of an aluminum electrolytic capacitor. What is a capacitor. The core temperature because this is the most important parameter for the lifetime estimation of elcaps.

Let s try a simple example of how this works. Most vendors assume that the lifetime of a capacitor doubles for every 10 c decrease in internal capacitor temperature which i will assume here. Mtbf mttf is the reciprocal of fit. Pulsed heating may be a complex calculation depending on thermal time.

The ambient temperature has the largest effect on life. Ceramic capacitors encoding consists 1 3 digits.