Product Information: PMLCAP

Polymer Multi-Layer Capacitors(PMLCAP) Technical Notes


The digitalization of electronic equipment is accelerating the miniaturization of electronic components while at the same time increasing the requirements for performance and reliability.
Due to their importance in every type of electronic circuit, capacitors are subject to ever-increasing performance requirements: greater capacities in smaller packages, improved frequency characteristics and heat resistance, and lower ESR and impedance.
To meet these needs, Rubycon offers an entirely new type of surface-mount film capacitor, the PMLCAP.

What are PMLCAP s?

PMLCAP is the abbreviation for Polymer Multi-Layer Capacitor, a surface-mount capacitor made up of multiple polymer layers. Although surface-mount film capacitors already exist, the PMLCAP differs from these in the type of dielectric used and in the manufacturing method.
The PMLCAP achieves a dielectric thickness of less than 1μm, which is difficult to achieve by conventional film manufacturing methods. Rubycon has established a new technology for forming a very thin dielectric layer, which allows it to manufacture miniaturized film capacitors with revolutionary capacity levels.

Manufacturing Technology

Electron microscope photoThe PMLCAP differs from conventional film capacitors not only in the thickness of the dielectric but also in the dielectric material. Conventional film capacitors are manufactured by evaporating metal onto a film such as PET, OPP, PPS, or PEN (metalized type), by setting metal foil on one of these raw films (foil type) and either coiling or layering the result to make lead wire, can, or chip type capacitors. However, as all of these methods use standard commercial films, they are limited in the extent to which they can achieve miniaturization. In its efforts to resolve the deficiencies in these manufacturing methods, Rubycon pursued alternative technologies, electing to develop the technology for manufacturing the dielectric layer in-house. The new technology was successfully employed for mass production in 2006.
The new technology uses radiation curable resin as the dielectric and employs vapor deposition polymerization in the manufacturing method. Specifically, a vacuum chamber is used to polymerize the dielectric layer, onto which the inner electrode layers (aluminum) are formed in patterns. These processes are continuously alternated to build up the layered structure that will be used as the element for capacitors. This element is cut to the requisite product size, and the electrode layer is formed to complete the product. Using the vapor deposition polymerization method allows the dielectric layer to remain pinhole free and evenly layered, even at sub-micron thickness. The number of layers is also high, ranging from several thousand to more than 10,000 layers.

PMLCAP Structure

StructureThe internal structure of a PMLCAP is comprised of only the dielectric and the inner electrodes. The external electrodes are formed from several layers of metal, with tin plating used for the outermost layer so as to allow for completely lead-free soldering. The PMLCAP complies with the RoHS Directive. Because the dielectric material used is highly heat resistant, the PMLCAP guarantees reflow soldering can be performed twice at a 260℃ peak. In addition, the PMLCAP offers the same self-healing effect as conventional film capacitors, allowing the failure mode to be open mode.

PMLCAP characteristics and uses

Notable characteristics of the PMLCAP include the following: low variation in capacity due to factors such as temperature changes or the application of bias voltage, superior characteristics in the high temperature range, and low noise resulting from the ripple current seen in the piezoelectric effect. The PMLCAP structure is also resistant to instantaneous pulse overcurrent. These characteristics make the PMLCAP suited for diverse uses, in devices that must be designed for quietness, for improved sound quality in audio equipment, and as components in automotive accessories. They can also be used in place of multilayer ceramic capacitors (MLCC) and tantalum capacitors.

Frequency Characteristic
Frequency Characteristic

Bias Characteristic
Bias Characteristic



Product line-up

The PMLCAP offers little variation in characteristics over a broad temperature range, from -55℃ to 125℃, while achieving significant miniaturization. In addition, the PMLCAP is very light, at 1/4 of the weight of a multilayer ceramic capacitor of equivalent size.
The ST series comprises six sizes (JIS), from 3216 to 8271, and a rated voltage range from 16V to 63V.

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