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Resistors

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Precautions to Use Resistors

Please click here for precautions of common matters for all products.

Precautions to use fixed resistors

	General in fixed resistors			Chip resistor array and networks
	Fixed wirewound type resistors			Fixed fusing resistors


		General in fixed resistors


		For basic precautions of using resistors, refer to the technical report "EIAJ RCR-2121A Guideline of notabilia for fixed resistors for use in electronic equipment" issued by JEITA.
		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.
		Flame retardant resistors may emit smoke or cause red heat when overload is applied but unlikely to emit flame or fire.
		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 KOA for the performance and reliability specifications in advance. NOTE: that resin absorbs moisture which may deteriorate resistance to moisture and corrosion.
		When the resistor is coated, potted and molded by resin materials, protective coat may be peeled and a crack at the solder fillet may be caused, leading to resistance change or disconnection. Use the resin with small stress at curing and confirm reliability. 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.
		When exceeding the rated power to a product in short time, we can not ensure safety. Contact KOA to advise of your surge voltage or current waveform.
		Cylindrical film resistors have spiral trimming and thus inductance. Pay Attention when you use them in a high frequency circuit.
		Due to the special coating, damage will occur to the protective coating of the flame retardant resistors by shock and vibration or by pinching with pliers or tweezers. Do not give any external force to protective coating until drying is fully completed after washing.


		Chip resistor array and networks


		Be careful for misalignment of mounting, the solder amount and the loading direction in flow soldering, to avoid solder bridge neighbor terminations.
		Adhesive of ionic residuals on the resistor or board may cause migration between neighbor terminations.


		Fixed wirewound type resistors


		Fixed wirewound type resistors have the structure where resistive wires are wound in the shape of coil, which are likely to oscillate and cause unusual phenomenon by inductance and capacitance at high frequencies.


		Fixed fusing resistors


		Confirm in advance about the overload conditions of abnormal moment are within the fusing area.
		Contact KOA in advance when you continuously apply the excess overload of rated voltage, for damage may be accumulated in the resistor.
		The arc phenomenon may occur under special circuit where higher voltage is applied again after fusing by over current. Make sure to use the product below the maximum open circuit voltage.
		Contact KOA about the maximum open circuit voltage for it varies depending on product type and resistance.
		Pay attention to the change of fusing characteristics, when the resistors are coated, potted and molded by resin materials.

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