Advanced Ceramic Resistors Yield Higher Power System Density

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Shrinking product designs have one more component hero in the quest to improve power system density. Prevalent in all types of electronic applications, power resistors serve the very useful purpose of withstanding and dissipating large amounts of power in the form of electric resistance. Engineers today are asked to design applications with increasing power densities, which directly correspond to the demand for resistors. Leading manufacturers of these mighty passive components are answering current application requirements with new power resistor designs that can tolerate higher amounts of power in small and smaller form factors.

Power resistors serve two primary functions: to absorb the inrush current caused by the switching action of a power device such as a MOSFET or IGBT, or as a shunt to measure and control current such as in a power supply. Today’s advanced resistors are made of thick film on ceramic technology. They are constructed using a resistive paste that is a mix of metal oxides, a carrier and a binder placed on a ceramic substrate. The process continues with resistive layers that are added sequentially based on the device’s required resistance pattern and value. The resistive pattern is printed onto the substrate at a high temperature to form a glass-like exterior that protects it from moisture or contaminants. Resistance is determined by the resistor track dimensions and the film resistivity.

Using thick film on ceramic technology gives resistors an inherent low inductance advantage, which is quite useful in circuits where switching frequencies of 50kHz are common. Thick film resistor technology has other benefits too. It is typically lower cost, can absorb and handle large amounts of power, can provide a wider range of resistance values and is capable of withstanding high surge conditions and ESD events. These capabilities make them ideal solutions in meeting power system density improvement goals.

An important consideration in selecting a high power thick film resistor for applications in harsh or demanding conditions is that they be AEC-Q200 compliant. AEC-Q200 is a global automotive standard for passive components to ensure temperature, pressure resistance, and safety consistency. AEC-Q200 qualified components must pass a stringent set of stress tests contained within the standard.

What developer wouldn’t want standards-based peace of mind in specifying components for more rugged environmental applications? Understanding this ongoing need, Bourns recently introduced its Model PWR247T-100 high power resistor series. Offered in a compact TO-247 package, it is engineered with a thick film resistive element on a white alumina ceramic substrate to deliver exceptionally low inductance benefits. Because this type of element enables heat sink contact that is electrically isolated from the resistive element, Bourns’ latest resistor can absorb power up to 100W when properly mounted to a heat sink.

Bourns offers one of the industry's broadest portfolios of AEC-Q200 compliant products consisting of resistors, magnetic and circuit protection products fully tested and qualified for the automotive market and beyond. Does your next design require the high and mighty benefits that new compact AEC-Q200 compliant high power resistors can deliver?