BMF resistors
16 August 2011
Vishay Foil Resistors has enhanced the RCK and S series high-precision bulk metal foil resistors.
The devices feature an improved design and manufacturing process resulting in improved power dissipation, fast thermal stabilisation of <1 second, low thermal EMF of 0.05 μV/°C, resistance tolerance to ±0.005% (50 ppm), and increased performance in high-moisture, high-temperature, and high-pulse applications.
In addition, the devices are now offered with Improved Performance Testing (IPT) for increased long-term stability under load and other stresses.
The newly advanced structural design of the RCK and S series 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 and assure resistance stability throughout the load-life and application environments of the resistor; holding resistance change to less than 0.05% throughout the planned life of the equipment.
The RCK and S series provide a military-grade typical TCR of ±2.0 ppm/°C from -55°C to +125°C, +25°C ref. The S series is also available in a K-Alloy version for TCR down to ±1.0 ppm/°C. The devices provide load-life stability of ±0.005% (50 ppm) at +70°C for 2,000 hours at rated power, and can achieve levels of 50 ppm after 10,000 hours when processed through the IPT protocol.
The resistors also feature resistance values from 0.5 Ω to 1 MΩ, with any resistance value within this range available at any tolerance with no additional cost or lead time effect. The devices are rated for power levels up to 2 W at 70°C and can withstand electro-static discharges (ESD) in excess of 25 kV. In addition to their low TCR, tolerance, and load-life stability, the resistors offer a low voltage coefficient of <0.1 ppm/V; current noise of 0.010 μVRMS/V of applied voltage (<-40 dB); and a non-inductive (<0.08 μH), non-capacitive design.
Rise time for the resistors is a nearly immeasurable 1 ns with effectively no ringing. These new benchmark levels of performance provide design engineers with the tools to build circuits not previously achievable. In addition, they reduce costs in the most critical circuits by eliminating the need for corrective circuitry used only for the purpose of stabilising or iterating accuracy in previous stages of the circuit path.
Devices in the RCK and S series are built to handle unconventional environmental conditions with minimal drift, making them suitable for military/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 devices are designed with a coating and moulding compound that provides moisture proofing and mechanical damping, as well as a path for heat dissipation.
The RoHS-compliant resistors are available in matched sets upon request. Samples and production quantities of the improved RCK and S series are available now, with lead times of five days for prototype samples, and from two days to five weeks for standard orders at the catalogue houses (depending on availability).
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