Resistor designs that meet the performance and assembly requirements including surface mount technology and Restrictions on the use of Hazardous Substance (RoHS), provide engineers new options. Frequently, power applications dictate new approaches to resistor designs. In these instances, other key attributes include low and very stable Temperature Coefficient Resistance (TCR), and low thermal resistance. In all cases, packaging provides a unique capability for the resistors showcased in this section.
SURGE CAPABLE THICK-FILM RESISTORS
Ohmite Manufacturing Co. developed the TFS series resistors to absorb more energy when compared to standard film resistors. This new flat series is offered in six sizes and covers a range from 0.5 to 2W, with energy ratings from 6 to 55 J for a single impulse. Voltages range from 3 to 11 kV, with a resistance range from 100Ù to 100 KÙ and as low as 1 percent tolerance, with a TCR of 100 ppm. Target applications include medical surge protection. These thick film, non-inductive resistors have a low profile, and are RoHS compliant. For more information on Ohmite TFS Series resistors, go tohttp://rbi.ims.ca/4416-649.
THIN FILM RESISTIVE HEATER
Engineers in TT electronics IRC wirewound & film technologies division used thick film resistive elements to design a source of instant heat for cabin air, engine fluids, and other automotive applications. With greater than 95 percent efficiency, the units can also serve as a voltage drop source for daylight running lamps and fan speed controls. The Anotherm Series consists of rugged thick film resistive elements deposited on tubular anodized aluminum substrate material. This construction allows the units to operate in temperatures up to 300C continuously with TCRs of less than 50 ppm/C. Units are offered in diameters from 0.5 to 1.5 inches with 9 inches of printed length. For more information on IRC Anotherm resistors, go tohttp://rbi.ims.ca/4416-648.
POWER RESISTORS IN TO-220 AND TO-247 PACKAGES
Vishay Intertechnology, Inc. has developed thick film power resistors in TO-220 and TO-247 packages with 30, 50 and, 100W ratings. The Vishay Sfernice resistors have values ranging from 0.010Ù to 550 kÙ for the LTO 30 and LTO 50 families, and from 0.015Ù to 1 MÙ for the LTO 100. TCR values are 150 ppm/C for resistors above 0.5V. The resistors mount directly on heatsinks and have a low inductance of less than 0.1 µH, making them ideal for control applications in power conversion. This reduces the printed circuit board space needed and improves heat dissipation. Using printed thick film technology on an alumina substrate, the resistors achieve tolerances as low as ±1 percent and up to ±10 percent. Typical applications include high-powered equipment in industrial controls, automotive, medical, and uninterruptible power supplies. For more information on Vishay's thick film power resistors, go tohttp://rbi.ims.ca/4416-650.
ULTRA PRECISION THIN-FILM CHIP RESISTORS
RCD Components Inc. developed a new ultra thin film resistor intended for applications requiring a tightly controlled TCR as a critical design factor such as measurement and control in medical, industrial communications, and portable electronic systems. The BLU thin film series offers designers low and highly predictable absolute TCR values. Designed for analog and high frequency applications requiring low noise (& -40 dB), these resistors have excellent stability levels when compared with metal foil technology, and offer substantial cost savings. Products are available with pulse resistant design, lead free terminations, matched sets, and burn-in for Hi-Rel applications. For more information on RCD's ultra thin film resistors, go tohttp://rbi.ims.ca/4416-651.
THICK FILM, HEAT SINKABLE RESISTOR
Ohmite Manufacturing developed its TEH70 a 70-W thick film resistor series with a heat sinkable TO-247 package. The TO-247 packaged resistor delivers higher power into less space with a non-inductive thermal resistance of 1.79 C/W. The low resistance is created by the resistor chip's size and use of a thermally conductive copper header. Available in 2 to 10 KÙ ratings, the power resistor is offered in two and three lead terminal configurations. The three-lead version allows grounding the heat sink through the middle terminal and is RoHS compliant. With a maximum working voltage of 500V and TCRs of ±50 and ±100 ppm, the TEH70 targets current sense and snubber applications. For more information on Ohmite thick film power resistors, go tohttp://rbi.ims.ca/4416-652.
CHIP SCALE RESISTOR ARRAYS
TT electronics IRC advanced film division introduced ball grid array (BGA) termination resistors for ceramic substrate applications requiring high frequency performance and a reduced footprint. Characterized for use as transmission line terminators, the CHC series custom arrays operate at frequencies up to 40 GHz. The construction of chip scale termination array uses solder balls on a high purity alumina substrate to achieve low parasitic inductance and capacitance. In addition the construction provides reduced ground bounce and reflections as well as improved signal integrity. Offered in various packaging sizes for the 1.0 mm pitch and 0.65 mm pitch series, units incorporating from 10 to 40 resistors in a wide range of standard and custom resistance values from 22 to 10 KÙ. For more information on IRC's ball grid arrayresistors, go tohttp://rbi.ims.ca/4416-653.