MFF Series Metal Foil Low-Resistance Chip Resistors
The MFF Series is a range of lead-free, halogen-free, RoHS-compliant metal foil low-resistance chip resistors built on an alumina ceramic substrate with a manganese copper (MnCu) alloy resistive element, designed for high-precision current sensing and voltage division in compact surface-mount assemblies. Power ratings span 0.33W to 4W across five case sizes — MFF0306, MFF0612, MFF1225, MFF2139, and MFF1206 — and resistance values cover 0.5mΩ to 100mΩ. Tolerance options are ±0.3%, ±0.5%, and ±1.0%, and the operating temperature range is −55°C to +155°C.
TCR is tightly controlled by resistance value and ranges from ±30ppm/°C at 10mΩ to 100mΩ in the MFF1206 up to ±150ppm/°C at 0.5mΩ to 0.75mΩ in the MFF0612. Rated continuous currents range from 8.12A for the MFF0306 at 5mΩ to 25mΩ up to 63.24A for the MFF2139 at 1mΩ to 4mΩ. The metal foil construction simultaneously achieves low resistance, low TCR, low electromotive force (EMF), and low inductance — a combination of properties that distinguishes foil technology from both thick-film and metal alloy strip alternatives. All variants are supplied on tape and reel for automated surface-mount assembly.
What are the MFF Series Metal Foil Low-Resistance Chip Resistors?
The MFF Series uses metal foil technology to deliver a level of precision and stability that standard metal alloy strip or thick-film resistors cannot match at low resistance values. In a metal foil resistor, the resistive element is a thin, photolithographically patterned sheet of MnCu alloy bonded with epoxy adhesive to an alumina ceramic substrate. The alumina substrate provides electrical isolation, dimensional stability, and a controlled thermal expansion coefficient that is matched to the MnCu foil to minimise thermally induced mechanical stress on the element over the operating temperature range.
The foil construction geometry is the source of several simultaneous performance advantages. The planar, meander-pattern element has extremely low self-inductance — a critical property in high-frequency switching circuits where an inductive shunt would introduce reactive impedance that distorts the current waveform and compromises measurement accuracy. The same geometry produces very low thermoelectric EMF between the MnCu element and the copper terminal electrodes, which is important in precision DC measurement applications where even microvolt-level thermoelectric offsets can degrade the accuracy of low-level current sensing. The MnCu alloy itself is selected for its inherently low and stable TCR, which keeps the resistance value close to its nominal across the full −55°C to +155°C operating range without requiring external compensation.
The component structure layers the MnCu foil element between the alumina substrate below and a flame-retardant epoxy protective coating above, with terminal electrodes formed from copper, nickel, and tin in sequence. The protective coating meets UL-94-V0 flame-retardant requirements. Short-time overload is rated at 2.5 times rated power for five seconds, with resistance change not exceeding ±1.0% plus 0.5mΩ. This lower overload multiplier compared to metal alloy strip resistors reflects the thinner element geometry of foil construction, which trades some overload headroom for the superior precision and stability characteristics that define the technology.
Environmental qualifications follow JIS C5201-1 and MIL-STD-202 methods, covering 1000-hour high-temperature storage at +155°C, 1000-hour low-temperature storage at −55°C, soldering heat resistance at 260°C, 100-cycle temperature cycling from −55°C to +155°C, 1000-hour moisture load life at 40°C and 90–95% RH, 1000-hour load life at rated current, mechanical shock at 100G for 11ms, and substrate bending with a 2mm deflection over a 90mm span. The MFF0306 and MFF0612 packages are supplied without body marking due to their small size; the MFF1225, MFF2139, and MFF1206 carry laser-marked four-digit resistance codes.
MFF Series Metal Foil Low-Resistance Chip Resistors Specifications
A practical overview for engineers and procurement teams evaluating resistive solutions.
Model: MFF
Resistor type: Metal foil
Description: Low resistance chip
Power Rating: 0.33W~4W
Resistance (Ω): 0.5m~100m
Tolerance (%): ±0.3, ±0.5, ±1
TCR (ppm/C): 30-100
Applications of the MFF Series Metal Foil Low-Resistance Chip Resistors
Where RARA metal clad resistors are deployed in the field.
High-precision current sensing in power supplies — output and input current measurement in regulated power supplies where the combination of tight tolerance, low TCR, and low EMF is required to maintain sensing accuracy across supply and ambient temperature variations.
Battery management systems — charge and discharge current measurement in lithium-ion and other battery chemistries where the low TCR of the MnCu foil element minimises measurement drift as battery temperature varies during charge and discharge cycles.
Measuring instruments and precision test equipment — reference shunt elements in current meters, power analysers, source-measure units, and calibration equipment where the low thermoelectric EMF of the foil construction avoids DC offset errors that would otherwise compromise measurement traceability.
High-frequency switching power conversion — inductor current sensing and switch current monitoring in switching regulators and DC-DC converters operating at high switching frequencies, where the low inductance of the foil element preserves the accuracy of instantaneous current waveform sampling.
Entertainment electronics — current sensing in audio power amplifier supply rails and high-current consumer electronics power circuits where component stability and accuracy contribute to consistent performance over product lifetime.
Industrial control and automation — current feedback in precision process controllers, servo amplifiers, and field instruments where the long-term stability of the foil element ensures that calibration remains valid over extended service intervals without drift-related recalibration.
Motor drive circuits — phase current sensing in brushless DC motor drives and stepper motor controllers where low-inductance sensing avoids measurement artefacts at the PWM switching frequency and during fast current transients.
Voltage division and ratio measurement — precision resistive dividers in instrumentation and measurement circuits where the MFF1206, covering the widest resistance range in the series at up to 100mΩ, supports accurate ratiometric sensing over temperature with its ±30ppm/°C TCR at the higher resistance values.
Related Products of the MFF Series Metal Foil Low-Resistance Chip Resistors
Model: LR
Resistor type: Metal alloy
Description: Low resistance
Power Rating: 0.5W~5W
Resistance (Ω): 0.2m~300m
Tolerance (%): ±0.5, ±1, ±2, ±5
TCR (ppm/C): 25-175
Model: LR2512H
Resistor type: Metal alloy
Description: Low resistance
Power Rating: 2W~3W
Rated Current: 17.3A
Resistance (Ω): 10m~80m
Tolerance (%): ±1, ±2, ±5
TCR (ppm/C): 50
Model: LRE
Resistor type: Metal alloy
Description: Low resistance
Power Rating: 1/6W~1W
Resistance (Ω): 0.2m~300m
Tolerance (%): ±0.5, ±1, ±2, ±5
TCR (ppm/C): 1-175
Model: MR
Resistor type: Metal alloy
Description: Low resistance
Power Rating: 2W, 3W, 5W
Resistance (Ω): 4m~100m
Tolerance (%): ±1, ±2, ±5
TCR (ppm/C): 50, 75, 200
Why Choose RARA Current Sensing Resistors
What sets RARA apart for engineers and procurement managers in industrial and automotive markets.
01
8 Sub-Categories
No other single supplier covers AEC-Q200 chip shunts, milliohm precision types, four-terminal Kelvin shunts, power metering, and 12,000A panel shunts under one ISO-certified roof.
02
Extreme Precision
HPS, UHPS, and PSS precision shunts deliver ±0.05% tolerance and 3 ppm/°C TCR — meeting the accuracy demands of EV battery coulomb counting, precision power analyzers, and billing-grade energy metering.
03
Automotive Qualified
Multiple AEC-Q200 certified models (BCS, LRA, ECS, BWR, TCS, PCBS) with IATF 16949 manufacturing certification — covering EV battery management, motor control, and charging applications.
04
Global Track Record
Trusted by Tesla, GM Korea, Proterra, Siemens, Rockwell, and Schneider Electric — deployed in EV powertrains, industrial drives, and utility metering systems across six continents.
