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Compact surface mount capacitors for low-profile power supplies

17th May 2017

Alice Matthews

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A series of surface mount, Y1 safety certified ceramic capacitors for low-profile power supplies has been launched by Murata. The DK1 capacitors are useful for any AC/DC switching power supply where a low-profile is needed for use in compact AV equipment, LED illumination, or 1U rack mounted equipment. Safety certified capacitors are deployed at the input side of a power supply line in order to suppress noise that builds up primarily in commercial AC power lines.

Such capacitors are usually of the leaded type, however that configuration can be problematic where there is limited height above the PCB surface, hindering efforts to make low-profile equipments and limiting component layout. In addition, because lead type capacitors are through-hole mounted, the lead wires are exposed on the underside of the circuit board. A fixed amount of insulating distance between the exposed lead wires and the metal components of the device is required by safety standards, compounding the problem and complicating the spatial layout within a device.

Murata’s new DK1 series Y1 capacitors use a structure of plate-shaped terminals on a disc-shaped ceramic dielectric placed within a plastic mold to reduce the terminal thickness that is present with lead type capacitors, resulting in a mounted height of 2.5mm or less for the product. Compare this with a leaded type Y1 capacitor that would typically stand 11mm high, and even laid on its side it would be 7mm and still the insulation clearance problem on the underside of the PCB exists.

Furthermore, the component format enables reflow surface mounting, and there is no longer a need to provide an insulating distance at the underside of the PCB. This advances profile reduction for power supply devices subject to size limitations in compact AV equipment, LED illumination and 1U rack mounted equipment, for which spatial design has been difficult in the past.

Connected from line to chassis, Y1 capacitors are a subclass of capacitor with the highest performance requirements as classified by insulation type in the standard IEC 60384-14, an international standard that regulates the withstanding pressure and combustion resistance of capacitors connected to commercial power supplies from the standpoint of preventing fires and electric shock from electrical leakage. The capacitors also meet the requirements of certification standards UL (UL 60384-14), ENEC (EN 60384-14), CQC (IEC 60384-14) and KTC (KC 60384-14)

Measuring 11.4x6x2.5mm the capacitors feature a useable temperature range of -40 to 125ºC. Available capacitance values are in the range 10-1,500 pF, and Y1 rated voltages of 250 and 300VAC RMS are available. Mass production of the capacitors begins in May 2017.