Metal foil on ceramic chip resistors reduce form factor
A range of metal foil chip resistors for current sensing duties in power electronics applications has been launched by TT Electronics, the MFC series. The resistors’ small size makes them a suitable choice for designers of highly compact power conversion circuits in industrial and medical applications. Providing a combination of high power density, tolerance of surge conditions and stability, the parts are useful for power supplies, DC/DC convertors, small motor drives, actuator drives and lighting drives with current sense requirements in the 1-10A range.
Factors driving the demand for this type of component are the growth in distributed power management and motion control in industrial and automated systems, and pressure to reduce the form factor in such systems, leading to the demand for smaller component sizes.
MFC resistors are 0603 size rather than the much larger 1206 or 2010 size required for a thick-film product of the same rating, thus saving valuable PCB space. The resistors measure just 1.6x0.8x0.6mm, and they feature wrap around terminations on three faces that have an electroplated nickel barrier and tin finish.
For versatility, standard values of 5, 7, 9, 10 and 20mΩ are available, featuring a tolerance figure of ±1%, and a 0.5W power rating at 70°C. The resistors’ operating temperature is -55 to 155°C, and their low TCR of ±50ppm/°C maintains accuracy over a range of operating currents and ambient temperatures.
The MFC resistors’ metal foil resistance material is bonded onto a 96% alumina substrate and features a protective coating that is resistant to all normal industrial cleaning solvents suitable for printed circuits. Metal foil on ceramic technology has better surge tolerance than thick-film, offering improved reliability in the presence of current surges. It also features lower self-heating than thick-film or metal strip construction thus obviating hot spots, improving both product and host equipment reliability.
TT Electronics claims that its MFC metal foil chip resistors provide the smallest footprint in a stable current sensing resistor in the 1-10A range.