An infrared IR reflecting film and IR soldering seem for the moment to be the only way out as long as we deal with traditional PET films. The film manufacturer has altered the thermo-mechanical properties to reduce shrinkage when used as a dielectric in SMD capacitors. The shrinking effects are best controlled by ESR measurements at the resonance frequency before and after soldering; see C 2. Capacitors with this dielectric often are presented under the title polyester.
The material attracts the interest mostly for SMD designs. They are manufactured in stack technology with a film thickness of down to 1. According to some papers such chips are able to stand up to both wave and IR soldering but only IR and vapor phase soldering is recommended.
However, recent developments and film improvements indicate a considerable step upwards in the temperature range. Specified measurement points have been inserted as ovals in the diagrams Figure C and — The following diagrams are more common and easy to interpret. In some of them there are curves inserted for a PEN , i. Among the curves over the frequency dependencies of impedance there are shown typical resonance frequency ranges. Because there are comparatively small changes of capacitance and the losses are rather small impedance diagrams get a pliable bend downwards into a sharp tip around the resonance frequency.
Examples of resonance frequencies are shown in Figure C Area for typical capacitance versus temperature of PET capacitors. A typical PEN curve is also shown. The temperature dependence of capacitance is influenced also by its magnitude, by the dielectric thickness and the design of the winding.
This is reflected in the distribution at higher temperatures. The frequency dependence of capacitance is ruled not only by the material but, to some extent, also by its magnitude and capacitor construction foil or metallized design. Sometimes there are shown examples of series capacitance measurements according to Formula C where an apparent increase occurs at higher frequencies. This increase is hinted by the dotted line in Figure C Typical curve range for loss versus temperature of PET capacitors.
Also the frequency dependence of losses is ruled by the capacitance magnitude and by the design. While the dotted curve may represent a metallized design MKT in the magnitude of some hundred nF the foil capacitor KT is localized in the lower part of the curve area. Example of resonance frequencies for 2 modules MKT capacitors. Other manufactures and other module distances give other resonance frequencies.
The seemingly sharp points in the impedance curve look in another magnification somewhat more round. Bump, vibration and temperature cycling may in, above all hermetic cans, cause interruption in internal termination leads or in the connecting link terminal lead — spray metal compound — metallizing.
Types that are molded into epoxy run less risk. If the casing on the other hand consists of plastic humidity will diffuse into the component. Humidity, however, impairs primarily only in the state of liquid for example at a condensation which will cause electrolysis, especially in the presence of a DC load.
When the moisture content outside of the component decreases the humidity diffuses out of the winding and the capacitance increase goes back. If the component on the other hand operates in a jungle climate for months the IR will decrease until the leakage current starts electrolysis in the metallization.
It will end in an open circuit. Remember Me. Home News by Category. Reading Time: 7 mins read. The molecular memory of the initial location before the elongation is deleted in a heat and pressure process during manufacture. This is mainly due to the fact that they have high long term stability, can be produced relatively cheaply and are heat resistant. One of the main characteristics of our film capacitor comes from the fact that they are not polarized.
Due to this design element, they are available for use in both AC power and signal applications. They are also designed to have high precision capacitance values, which means that they can retain their value for a much longer period of time than capacitors of other types.
The aging process of these types of capacitors is generally much slower than it would be if a different type of material were being used during construction.
Military film capacitors are tested and qualified to military standards, with more than 30 military qualified products. A wide selection of packaging designs are available such as film-wrapped, pre-molded epoxy cases, and hermetically sealed metal cases. Exxelia continues to research and develop film caps with new methods in capacitor manufacturing to provide durable designs and packaging schemes for special environmental use.
Your browser is not up to date and you won't be able to benefit from all the features on the site. We recommend that you update your browser or use Google Chrome or Mozilla Firefox. Main Features. Typical Applications. Contact Download Datasheet. Technical Characteristics. Dielectric PET. Voltage AC Not supported. Terminations Axial.
Notes No special note. Related Standards. Related Documents. Frequently Asked Questions. Q: Plastic Film Capacitors. Q: Durable Capacitors for Exceptional Performance. See more products. Temperature Not supported.
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