IN Brief:
- CHEP resistors cover 20Ω to 120Ω in 0402 and 0603 case sizes.
- 0402 devices operate to 50GHz in flip-chip mounting, while 0603 versions reach 40GHz.
- Mounted according to Vishay's specified conditions, the series supports power ratings up to 1.8W in 0402 and 2.8W in 0603.
Vishay Intertechnology has introduced a thin-film chip-resistor family that combines microwave operation with power ratings reaching 2.8W in standard 0402 and 0603 surface-mount footprints.
The Sfernice CHEP series uses an aluminium-nitride substrate and covers resistance values from 20Ω to 120Ω. In the 0402 case size, Vishay specifies 1.2W standard power and 1.8W when the device is mounted according to its higher-power conditions; the 0603 package is rated at 1.8W as standard and up to 2.8W with the specified mounting arrangement.
Frequency capability depends on package size and terminal configuration. CHEP0402 parts can operate to 50GHz when mounted as flip-chip devices, while wraparound active-face-up mounting is specified to 20GHz. The larger CHEP0603 package supports operation to 40GHz.
The combination is aimed at RF designs that need to dissipate meaningful power without allocating the board area required by a larger microwave resistor. Vishay lists applications including 5G and 6G infrastructure, LEO satellite terminals, remote radio units, antennas, telemetry systems, data links, and phased-array radar.
Aluminium nitride is central to the thermal design because it conducts heat more effectively than the alumina commonly used in thin-film components. That gives the resistive element a lower-impedance thermal path into the board, but the headline power rating still depends on how effectively the PCB removes the heat.
The higher 1.8W and 2.8W figures therefore cannot be treated independently of the recommended land pattern, copper area, ambient temperature, and surrounding layout. More power in a smaller footprint increases local heat flux, making the board part of the component’s thermal system rather than simply the surface on which it is soldered.
RF behaviour introduces a separate constraint. At tens of gigahertz, the parasitic inductance and capacitance of a nominally resistive component can alter its impedance sufficiently to affect matching, attenuation, phase, and gain flatness. Package geometry and the transition from the transmission line into the resistor become part of the electrical design.
Vishay quotes LC values as low as 1 × 10-24 for the CHEP family, with the low internal reactance intended to reduce phase shift and keep the impedance close to its nominal resistive value as frequency increases.
The difference between flip-chip and wraparound performance illustrates how much the current path contributes. Mounting the 0402 device active-side down shortens the RF path into the resistor and reduces package parasitics, enabling the 50GHz rating. The more conventional wraparound arrangement is easier to integrate into some assembly processes but carries a lower frequency limit.
Resistance values are concentrated around the range commonly used for RF termination, attenuation, and matching. Vishay specifies 20Ω to 120Ω, tolerances down to ±1%, and a standard temperature coefficient of ±100ppm/°C, with ±50ppm/°C available on request.
The devices operate from -55°C to +155°C and are available with both flip-chip and wraparound terminals. Samples and production quantities are available now, with Vishay quoting lead times of 16 weeks.
Those specifications make the series relevant to dense multi-channel RF hardware where board area is repeatedly consumed by similar matching and termination networks. In a phased-array design, even a modest reduction in the area required by each channel can accumulate across tens or hundreds of repeated paths.
The thermal trade-off remains considerable. A compact resistor dissipating several watts concentrates heat into a very small region, so RF and thermal layouts cannot be designed independently. Copper dimensions, ground structure, substrate choice, and neighbouring components all affect whether the device can sustain its specified dissipation.
Microwave layout is equally unforgiving. A resistor specified to 50GHz can still underperform if pads, vias, or transmission-line transitions introduce more discontinuity than the component itself. The package provides the necessary operating range, but the surrounding PCB must preserve it.
CHEP therefore addresses two constraints that usually pull in opposite directions: higher dissipation favours a larger thermal structure, while higher frequency favours smaller geometries and shorter current paths. The aluminium-nitride thin-film construction is intended to keep both inside conventional chip-resistor outlines.
At 50GHz and close to 2W in an 0402 footprint, resistance and tolerance are only the beginning of the design exercise. The same component has to be treated as a microwave discontinuity and a concentrated heat source — rather more engineering attention than its physical size might initially suggest.
