CMF7061R900BERE

FAQFrequently Asked Questions

• Can the CMF7061R900BERE handle continuous operation at 175°C, and what derating factors should I apply for reliability in industrial environments? The CMF7061R900BERE is rated to 175°C maximum, but continuous operation near this limit accelerates aging and reduces service life. Vishay Dale metal film resistors typically require 20–30% power derating above 70°C for long-term stability. At 175°C continuous, consider limiting actual dissipation to 1.2–1.4W and verify thermal cycling performance in your specific enclosure. For mission-critical industrial designs, operating below 150°C ensures margin against tolerance drift and parametric creep over 10+ year lifecycles.
• What is the actual TCR (temperature coefficient of resistance) behavior of the CMF7061R900BERE across its full -55°C to 175°C range, and how does this affect precision measurement circuits? The CMF7061R900BERE specifies ±25ppm/°C, which is typical for metal film resistors but assumes linear behavior. In precision analog circuits—such as transimpedance amplifiers or Wheatstone bridges—the actual TCR may exhibit slight nonlinearity at temperature extremes (-55°C and above 150°C), causing cumulative error beyond simple linear prediction. For designs requiring <0.1% accuracy over temperature, select matched pairs from the same manufacturing batch and perform bench verification across your operating range, or consider active temperature compensation instead of relying on the nominal TCR alone.
• Is the CMF7061R900BERE suitable as a replacement for older 1/2W carbon film 62Ω resistors in legacy military or aerospace equipment? The CMF7061R900BERE is not a direct drop-in replacement for carbon film resistors, despite similar part values. Key differences include: the CMF7061R900BERE is 1.75W (higher power capability), metal film (lower noise and better TCR), axial package with different lead stiffness, and flame-retardant coating. RoHS non-compliance and REACH-affected status may trigger qualification obstacles in aerospace/military programs. If migration is necessary, perform full electrical, thermal, and mechanical re-qualification, including EMI baseline testing, vibration endurance, and thermal cycling validation per applicable specifications (MIL-PRF-55182 or equivalent).
• How does the moisture-resistant coating on the CMF7061R900BERE affect solderability and long-term reliability in salt-spray or high-humidity environments? The moisture-resistant coating on the CMF7061R900BERE reduces surface corrosion on the wire leads and body but does not eliminate susceptibility to ion migration or dendrite formation under high humidity and bias voltage. In salt-spray (ASTM B117) or tropical environments (>85% RH, >40°C), the resistor remains functional, but residual flux, PCB contamination, and voltage stress at lead terminations become the limiting factors. Use a conformal coating (acrylic or silicone) over the entire assembly and maintain <50V/mm electric field at the resistor body to mitigate risk. Periodic humidity-bias testing (IPC-A-610 or IEC 60068-2-30) is recommended for mission-critical designs.
• What is the frequency response and high-frequency behavior of the CMF7061R900BERE, and can it be safely used in RF or switching power supply circuits? The CMF7061R900BERE is a passive film resistor with parasitic inductance and capacitance typical of axial through-hole components (~2–5nH series inductance, pF-level shunt capacitance). This makes it unsuitable for high-frequency RF circuits (>100MHz) or as a primary current-sense element in fast switching regulators (>500kHz), where inductive ringing and frequency-dependent impedance cause measurement errors and EMI coupling. For switching supplies, use this resistor only in low-frequency bias networks or as a load resistor after filtering. For RF applications, consider chip resistors with lower parasitic inductance or wire-wound designs optimized for the target frequency band.
• The CMF7061R900BERE is RoHS non-compliant—what are the practical implications for design approval and supply chain risk? RoHS non-compliance means the CMF7061R900BERE may contain lead or other restricted substances and cannot be used in products subject to EU RoHS Directive 2011/65/EU (most consumer and industrial electronics in Europe). Check your end-market regulations and customer requirements before design-in. If RoHS compliance is mandatory, source an equivalent metal film resistor from Vishay's RoHS-compliant CMF70 series (e.g., CMF70 with lead-free terminations) or substitute a chip resistor alternative. Supply chain: RoHS non-compliant stock may face restriction of sale in certain regions and logistics complications, potentially extending lead times or triggering sudden obsolescence.
• Can the CMF7061R900BERE be used in a high-voltage divider circuit, and what precautions are necessary for voltages above 500V? The CMF7061R900BERE is not rated for high-voltage applications. Although the 1.75W power rating allows modest dissipation, the axial package and coating are optimized for moderate-voltage environments (<250V typical). For dividers above 500V, surface tracking, arc initiation, and corona discharge become risks, especially in humid or contaminated conditions. If high-voltage division is required, select a resistor with explicit HV ratings (e.g., wirewound or special film types rated to kV levels), increase spacing on the PCB, and use conformal coating or potting. For designs below 250V, the CMF7061R900BERE is acceptable but verify thermal dissipation and creepage distance per IEC 60950 or equivalent safety standard.
• What are the lead-time and obsolescence risks for the CMF7061R900BERE, and how does its REACH-affected status impact availability? The CMF7061R900BERE is a REACH-affected component, which imposes tracking and documentation obligations on suppliers and may restrict sourcing to qualified distributors. Lead times for specific part numbers in Tape & Reel packaging can extend 8–16 weeks if out of stock, particularly during supply-chain disruptions. REACH registration updates or substance substitutions by Vishay may trigger part number changes or allocation freezes. For long-term programs, maintain a qualified alternatives list (e.g., other CMF70 tolerance/wattage variants or second-source metal film resistors) and confirm availability with your distributor at design kick-off. Consider a 12-month buffer stock for critical applications.
• How should the CMF7061R900BERE be mounted and what thermal management is required to reliably dissipate 1.75W in a confined space? The CMF7061R900BERE is an axial through-hole resistor requiring PCB drilling and wave or hand soldering. At full 1.75W dissipation, the resistor surface temperature rises significantly above ambient (typically 50–100°C rise, depending on air flow). In confined enclosures (< 10cm³/W thermal mass), mount the CMF7061R900BERE vertically with clearance from the PCB surface to enable natural convection, or provide forced-air cooling. If PCB space is limited, transition to a higher-power chip resistor or consider a parallel arrangement to split power. Verify final temperature with an IR camera or thermocouple; if the resistor exceeds 150°C in your assembly, reduce applied power or add thermal management to avoid premature failure.
• What is the noise performance of the CMF7061R900BERE in precision instrumentation or data acquisition circuits, and how does it compare to wirewound alternatives? Metal film resistors like the CMF7061R900BERE exhibit low noise (typically 15–20µV/V noise density) compared to carbon film, making them suitable for precision instrumentation. However, they are not as low-noise as specialized thin-film or wirewound precision types (5–10µV/V), and axial geometry adds some EMI coupling compared to surface-mount equivalents. In sensitive analog front-ends (sub-µV resolution ADCs or lock-in amplifiers), use the CMF7061R900BERE for non-critical bias networks but rely on thin-film or chip resistors with Kelvin terminations for the main signal path. If space and thermal budget allow, verify noise floor in your circuit with bench measurements before committing to production.