Vishay Precision Group has announced that its VFR (Vishay foil resistors) division has enhanced the RCK and S series of high-precision BMF (bulk Metal foil) resistors. The resistors feature a design and manufacturing process resulting in power dissipation, thermal stabilisation of less than 1s, thermal EMF of 0.05μV/°C, resistance tolerance, and performance in high-moisture, high-temperature, and high-pulse applications, claims the company. In addition, the resistors are available with IPT (improved performance testing) for long-term stability under load and stresses.
The structural design of the resistors employs a pre-planned stress compensation that never exceeds Hooke's constant for the materials. Therefore, the resistors maintain their molecular-level structural integrity.
The resistors provide a military-grade TCR (temperature coefficient of resistance) of ±2ppm/°C from -55 to +125°C, 25°C reference. The S series is also available in a K-alloy version for TCR down to ±1ppm/°C. The resistors provide load-life stability of ±0.005% with 50ppm at 70°C for 2,000h at rated power, and can achieve levels of 50ppm after 10,000h when processed through the IPT protocol. The resistors feature resistance values from 0.5Ω to 1MΩ, with any resistance value within this range available at any tolerance with no additional cost or lead time effect, claims the company. The devices are rated for power levels up to 2W and can withstand ESD in excess of 25kV. Rise time for the resistors is 1ns with no ringing, claims the company.
The resistors are built to handle unconventional environmental conditions with minimal drift, making them suitable for military and space applications according to EEE-INST-002 specifications and MIL-PRF 55182. Each resistor undergoes at least one short-time overload of 6.25 times the rated power during the manufacturing process. The resistors are designed with a coating and molding compound that provides moisture proofing and mechanical damping, as well as a path for heat dissipation.
The resistors offer a voltage coefficient of less than 0.1ppm/V; current noise of 0.010μVrms/V of applied voltage which is less than -40dB; and a non-inductive of less than 0.08μH, non-capacitive design. The resistors are RoHS-compliant.
