April 12, 2019 by Sam Holland
Automotive and industrial electronics face challenging environments that can include high temperatures, voltages, currents, and frequencies, as well as exposure to moisture and outdoor conditions.
The same could also be said for many other industrial applications, and both automotive and industrial electronics make extensive use of capacitors.
Fortunately, there are film capacitors on the market today that provide the necessary characteristics for designers while also enduring such harsh conditions.
Film capacitors, which use a very thin polymer film as the dielectric material, are known for their ability to offer low inductance, low cast, and excellent stability.
Depending on the polymeric film used, these capacitors can offer additional benefits such as heat resistance (when using PTFE film) or long-term stability (when using a metalised PE film).
They can be designed to handle extremely high voltages on the order of kV. Another type of film capacitor, known as a power film capacitor, can handle over 200 VAs.
While there are numerous film capacitors available, four specific product lines stand out above the rest because of their ability to withstand the rigours of harsh environments and demanding design, that we touched upon earlier, for automotive and industrial applications.
These include the KEMET F863 series, the Murata high-temperature film capacitor product line, the AVX Accu-P thin film capacitors, and the Panasonic EZP-Q series.
In February 2018, KEMET introduced a line of metalised polypropylene film capacitors, the F863 series.
These film capacitors are designed specifically for the harsh operating conditions found in both automotive and industrial applications, with an operating temperature range from −−−40°C to 100°C.
From the F863 series of film capacitors. Image courtesy of Mouser.
The KEMET F863 series has a 300 VAC rated voltage and 0.1 to 10 µF capacitance range.
They are considered an automotive class and meet AEC-Q200 qualification requirements, working particularly well in capacitative power supplies.
The Murata line of high-temperature film capacitors has a continuous operating temperature of over 125°C, and it can handle a higher ripple current at this high temperature when compared to similar capacitors.
Designed with automotive applications in mind, these capacitors can be used with onboard chargers (OBC), electric compressors, and wireless power transfer systems (WPT). They have a rated voltage of 500V and are available in 10µF, 15µF, and 20µF.
AVX’s Accu-P series of thin film capacitors have been designed especially for rugged automotive applications that involve high frequencies but, at the same time, require ultra-low losses.
Applications include GPs, vehicle alarm systems, matching networks, vehicle location systems, and power applications. This series of capacitors are available in capacitance ranges from 0.05 µF to 68 µF with tolerances on the order of ±0.01 pF. They also remain very stable across varying temperatures and across varying frequencies.
AVX Accu-P Series Thin Film Capacitors. Image courtesy of Mouser.
The Panasonic EZP-Q line of film capacitors use metalised polypropylene (PP) to achieve a highly moisture-resistant capacitor (85°C, 85%RH, 1000h) and are designed for long-term outdoor use, making them ideal for the harsh conditions of automotive electronics.
They have a rated voltage of 250VAC and are available in 12, 22, 36 μF capacitance with a tolerance of ±10%. In addition, the EZP-Q line is known for its excellent reliability and safety.
If you are an electronics engineer facing the challenges of designing a functional circuit that can survive in harsh conditions—all while handling high voltage, current, power, and/or temperature—there are far more solutions than those discussed here.
Thin film capacitors are currently evolving to meet the most demanding of requirements, much like those highlighted in this article.
