The advances in resistor technology extend in many directions, following the varied requirements of the many diverse industries that use these critical components. Sizes shrink, operating temperatures expand and power ranges broaden.
As these diverse changes occur, passive component designers also have to worry about one of the key challenges in today’s high- speed, high-power consumption systems, removing heat. “Package designs must increase the resistor’s ability to dissipate heat, as well as its ability to withstand pulses of longer duration,” says Jim Rieley, sales director for BI Technologies’ SMT Division.
All these changes are happening amidst the backdrop of changes driven by environmental regulations. But while many industries struggled to eliminate lead and other banned materials, passive suppliers have moved forward with few missteps.
Even though resistor technologies have been around for several decades, chemical engineers, metallurgists and electronic engineers continue to come up with techniques that let these small, yet critical components keep pace with the changing demands of today’s circuit board developers.
Ultracapacitors are ecologically friendly
Ultracapacitor users can now get environmentally clean parts from United Chemi-Con. The company’s DLCAP Electric Double Layer Capacitors are lead-free, cadmium-free and use a non-acetonitrile electrolyte with activated carbon electrodes. The line come in eight different energy and power types. They have a capacitance range of 350 to 3,100F, and a voltage range of 2.3-2.5V. Internal resistance is typically 0.7 milliohms at 2,400F. DLCAPs also withstand over 1 million charge/discharge cycles. DLCAPs are also available in 5 to 500V banks.
Resistors withstand high temperatures
TT electronics IRC Advanced Film Division is offering a tantalum nitride chip resistor line rated up to 200C. The PFC-HT Series uses IRC’s proprietary TaNFilm self-passivating resistive element technology. Parts feature a wraparound non-leaching termination style, with either gold-plated or 100 percent tin (lead-free) versions. The entire package is designed to operate at elevated temperatures such as down-hole oil drilling sensing equipment, automotive engine compartments, and aerospace applications.
“These terminations will not reflow at 200C,” says Jerry Seams, applications engineering manager for IRC’s Advanced Film Division.
Available in industry standard 0603, 0805 and 1206 chip sizes, the PFC-HT line has voltage and power ratings of 33.3V/62.5 mW, 50V/100 mW and 100V/125 mW, respectively. Resistance range is from 10Ù to 85KÙ, with tolerances to ±1 percent. The resistors have absolute TCRs from ±25 ppm/C to 100 ppm/C.
Pricing is $0.30 each in quantities of 10,000.
Power resistors coverbroad range
A line of non-inductive high-density power resistors now offers a broader range, helping power electronics engineers specify more accurate wattages. BI Technologies SMT Division has further extended its range of.
The BHPR Series resistors from the TT electronics company now ship in a TO-227 style, RoHS-compliant package and are now available in power ratings of 100W, 150W, 250W, 300W and 600W.
They have a resistance range of 1Ù to 1KÙ, with tolerances to ±5 percent and TCRs to 100 ppm per C. Operating temperatures are from -55 to 155C. Low-volume pricing for the TO227-style packages starts at $17.69.
Current sensing resistors have small size
The Power Metal Strip resistor line from Vishay Intertechnology Inc. brings 1-W current sensing resistor to the very small 1206 package size. The WSLP1206 features a low 2-mÙ to 50-mÙ resistance value range, with high-temperature performance up to 170C.
The compact resistor can replace larger current sensing resistors, saving space on circuit boards that require current sensing and pulse applications in dc-to-dc converters. The resistor, which sells for $0.25 in lots of 100,000, offers low inductance values of 0.5 to 5 nH, with frequency response to 50 MHz. Thermal EMF is less than 3ìV/C.