MELBOURNE, Fla. Multilayer varistors have been made surface-mountable through a nickel barrier-termination technology that to date has been the province of chip capacitors, resistors and inductors. Harris Semiconductor said that its Terminator surge suppressors provide the optimized solderability required in harsh wave-solder environments.
Standard terminations for voltage suppressors are silver-based and generally achieve solder-fillet heights of 30 percent to 50 percent of the overall device height. Harris' nickel/tin process prevents solder leaching of silver-based terminations while improving solder-fillet heights to 50 to 70 percent, said Steve Cowman, director of suppression products at the company.
The devices in the ML and MLE series are available in a range of operating voltages (3.5 to 120 V for the ML series) and provide bidirectional clamping to IEC 1000-4-2 (ESD) and IEC 1000-4-4 (EFT) standards to protect on-board ICs and transistors. They can replace larger surface-mount zener and resistor-capacitor combinations in many applications.
The response time of the Terminator's zinc-oxide dielectric is less than 1 ns, according to Harris. The devices are rated for a nonrepetitive surge current of 30 to 250 A for an 8/20-microseconds waveform (8 microseconds to peak value, 20 microseconds fall to half value), and a nonrepetitive surge energy of 0.1 to 1.2 J (10/1,000-microseconds waveform) with rated dc or rms voltage applied.
When nonconducting, the device appears essentially as an open circuit; leakage current at maximum rated voltage is said to be less than 50 microamps (typically below 25 microamps).
The varistors are supplied in 0603 and 0805 device sizes and shipped in 13-inch reels (10,000-piece quantities), 7-inch reels (2,500 pieces) or bulk packs (100 pieces). They are priced at 28 cents each in 10,000-piece quantities.
Call (407) 724-7000
EETInfo No. 617