Film Capacitor Failure Analysis

Film capacitors (polymer film) are generically called “film caps” as well as power film capacitors which are electrical capacitors with an insulating plastic film as the dielectric, sometimes combined with paper as carrier of the electrodes. The dielectric films, depending on the desired dielectric strength, are drawn in a special process to an extremely thin thickness, and are then provided with electrodes. The electrodes of film capacitors may be metallized aluminum or zinc applied directly to the surface of the plastic film, or a separate metallic foil overlying the film. Two of these conductive layers are wound into a cylinder shaped winding, usually flattened to reduce mounting space requirements on a printed circuit board, or layered as multiple single layers stacked together, to form a capacitor body.

Success Stories

Acrylic Film Capacitor Failures

Acrylic Film Capacitor Failures

Gideon Analytical Laboratories received two acrylic film capacitors for electronic failure analysis. Six good capacitors were also provided for comparison. A capacitor is a passive two-terminal electrical component that stores potential energy in an electric field. The effect of a capacitor is known as capacitance. While some capacitance exists between any two electrical conductors in proximity in a circuit, a capacitor is a component designed to add capacitance to a circuit.
IC EMI MKP .33uF Film Capacitors Failures

IC EMI MKP .33uF Film Capacitors Failures

Gideon received six used IC .33uF K MKP X2 MPX film capacitors with lower than expected capacitance for failure analysis. EMI suppression capacitors are used to suppress any noise from an electronic device by reducing the input impedance of the device. These types of capacitors have 2 classifications, X and Y. The X-type connects line to line. X capacitors have three categories; X1, X2, and X3. These are based on voltage.
Failure Analysis on Metallized Film Capacitor

Failure Analysis on Metallized Film Capacitor

Gideon Analytical Labs received one M83421/01-5191S film capacitor with lower than expected capacitance for failure analysis. This device is a fixed metalized paper-plastic dielectric hermetically sealed capacitor in a metal can. Metalized film capacitors are made of two metalized films with plastic film as the dielectric. A very thin vacuum deposited aluminum, tin or zinc metallization is applied to one or both sides to serve as electrodes. This configuration has “self-healing” properties, in that dielectric breakdowns or short circuits electrodes do not necessarily lead to the destruction of the component.
Film Capacitor Failure Analysis

Film Capacitor Failure Analysis

Gideon Analytical Labs received three partial boards with four coupling Vishay MKT 1817 63V ERO 0225 film capacitor failures. After electrical measurements and considerable testing, the ESR was found to be the cause of the failure, however, what caused the ESR to elevate? It was determined the packaging on the capacitor was not adequately protecting the terminal end from the outside environment. Moisture ingress elevated the ESR and with higher ESR, the higher the heat produced in the circuit.
Wima versus Vishay Film Capacitor Comparison

Wima versus Vishay Film Capacitor Comparison

Film capacitors are widely used because of their superior characteristics. This capacitor type is not polarized, which makes them suitable for AC signal and power use. Film capacitors can be made with very high precision capacitance values, and they retain that value longer than other capacitor types. This means that the aging process is generally slower than in other capacitor types, such as the electrolytic capacitor. Film capacitors have a long shelf and service life, and are very reliable, with a very low average failure rate.