Thick-film resistors oust wire-wound types

HVC Series thick-film surface-mount resistors exhibit superior power and voltage handling capabilities, making them ideal for use in defibrillators, power supplies and other high-voltage applications.

With the trend towards portable and home use medical devices, the designer faces increased pressure to reduce overall appliance costs, while improving on unit performance and reliability.

With these demands in mind, TT Electronics Welwyn Components has refined a thick-film chip resistor family to handle continuous voltages up to 3kV.

Designated the HVC Series, the thick-film surface-mount resistors exhibit superior power and voltage handling capabilities, making them ideal for use in defibrillators, power supplies and other high voltage applications.

"Design engineers have traditionally used bulky wire-wound and axial film resistors to achieve the required power and functionality, however these are no longer viable options for medical devices.

The HVC offers a small footprint solution for lower cost manufacture and enhanced unit performance", said John Graham, Marketing and Sales Director of Welwyn Components.

The company achieved the higher voltage ratings through a combination of proprietary materials, special resistor element geometry and adjustment techniques.

Because of their robust thick-film construction and wrap-around terminations to prevent leaching, the HVC Series resistors can be immersed in 260C solder for 30s, enabling the resistors to be mounted on one side of a PC board while leaded components are attached to the other side.

The resistors are fully compatible with high-speed placement equipment and all soldering processes.

With the new extended range, the HVC Series resistors are now offered with limiting element voltages of 1000, 2000 and 3000V in 1206, 2010 and 2512 industry standard chip sizes, respectively.

Power ratings for the three chip sizes range from 0.3 to 1W at 70C.

Resistance values range from 100kohm to 1Gohm, with tolerances down to 0.5% and TCRs to 100ppm/C.

Operating temperatures range from -55 to +150C.

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