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Fixed Resistors' Safety Application Note

Writer:Microhm Page View:Date:2019-05-24
When the resistors are operated in ambient temperature above the rated temperature, the power rating must be derated according to the derating curve. Resistors in general may emit flame, fire, smoke or red heat when overload is applied.
When a power exceeding the rated power is applied in a short time, we can not guarantee the safety only that the average power is below the rated power. Please contact Microhm with the surge voltage or current waveform for advise.

Flame retardant resistors may emit smoke or cause red heat when overload is applied but unlikely to emit flame or fire. The flame retardant resistors are weak against mechanical stress compared with the general resistors due to the special coating. Please do not apply impact, vibration or pinching with pliers or tweezers to the resistor body. Do not apply any external force to the protective coating until drying is fully completed after washing.
Cylindrical film resistors have inductance due to the spiral trimming. Please be aware when using in a high frequency circuit.

When the resistors are sealed and coated by coating materials such as resin, deterioration of the resistor by thermal stress or resin may affect the characteristics. Confirm with Microhm for the performance and reliability specifications in advance. When the resin absorbs moisture, the resistance to moisture and corrosion of the resistor may deterorate, so be aware. When the resistor is coated, potted and molded by resin materials, the curing stress could cause peeling of protective coating and crack of solder fillet, resulting the resistance change and disconnection. Do not coat nor seal the flame retardant coated resistors nor metal oxide film resistors.

Allow enough intervals for cooling after mounting metal film resistors, before washing the flux. Residues of ionic substances may deteriorate resistances to moisture and corrosion.

Keywords:Fixed Resist

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