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KOA Corporation > Product > Common matters for all products

Common matters for all products

Common precautions for all products

All product specifications and data are subject to change without prior notice. Be sure to request and confirm the latest technical specifications before you order and/or use.

Common matters in all products

General

  • For precautions in general, refer to the "EIAJ RCR-1001A Safety application guide for electronic parts" issued by JEITA.

Applications

  • The products are intended for use in general electronic equipment. If you use the products in equipments requiring extremely high reliability such as automotive, medical, nuclear power generation, aerospace, satellite, etc., please contact us in advance.
  • Consider sufficient fail-safe design if the products are used in applications requiring high reliability. Ensure safety of a whole system by setting proactive circuits and redundant circuits to avoid the single-failure of the part leading to unsafety of the product.

Environment for use

  • The products are not to be used in special environments unless otherwise specified. Examine and confirm the performance and reliability before you use the products under the following environments:

    1. Under direct sunlight, outside exposure and in dust.
    2. In liquids such as water, oil, organic solvent and chemicals and in areas where these liquids are used.
    3. In places where the products are exposed to sea breeze or corrosive gases including SO2, H2S, Cl2, NH3, NO2, etc.
    4. In places with large static electricity and strong electromagnetic waves.
    5. In places subject to dew condensation.
    6. When the products or printed circuit boards are sealed and coated by resin or other coating materials
    7. In places where the products are exposed to the mist from lubricant oil.

Sulfuration

  • >Products with silver electrodes may increase the resistance value under sulfur atmosphere such as sulfide gases (H2S, SO2, etc.) or by attaching sulfide compounds. Take anti-sulfur measures under these conditions.

Anti-pulse characteristics

  • If transient overload (voltage, current and power) such as pulse and surge are applied to the products, the performance and reliability may be degraded. Contact KOA if you need anti-pulse characteristics data.
  • Pay attention to the discharge between terminations when high voltage is applied.

Storage

  • Store the products in dust free areas and keep them away from extremely high and low temperature, moisture, dew condensation, direct sunlight, sea breeze, corrosive gases such as SO2, H2S, Cl2, NH3, NO2, etc. or mist from a lubricant oil. Use the desiccant if necessary.
  • Consult us about the conditions and period of storage.

Storage of products with Pb-free terminations.

  • Avoid damage and physical shock to the product by nipping them with hard tools like pliers and tweezers or by imperfect adjustment of the mounting machine, which may affect the characteristics or lead to disconnections and cracks.

Mounting

  • Avoid damage and physical shock to the product by nipping them with hard tools like pliers and tweezers or by imperfect adjustment of the mounting machine, which may affect the characteristics or lead to disconnections and cracks.
  • If the bottom point of nozzle on the mounting machine is too low, the product may be knocked on to the printed board, which may deteriorate the characteristics or lead to cracks. Decelerate the nozzle just before mounting and mount the product after correcting a deformation of the printed circuit board.
  • Do not use the products which have fallen when mounting, or which have been removed from the printed circuit board.
  • Contact us if the printed circuit boards after mounting are molded and sealed by coating materials.
  • Do not stack the printed circuit boards after mounting, for this may damage the products.
  • Characteristics of the film type resistors and sensors may be changed by overvoltage from electrostatics. Keep electrostatics away from products while assembling and handling (monitors of insertion machine and inspection machine, human contact and etc.).
  • Prevent or eliminate adhesion of ionic substances such as salts, salinity and sweat, as they may degrade the resistances to moisture or corrosion.

Soldering

  • Perform soldering within the temperature, time and the number of cycles, specified in technical specifications or precautions for each product. If the products are exposed to high temperature for long periods of time, the color and characteristics may change or disconnection may occur.
  • Prevent any external force on the products until solder is cooled.
  • Handle carefully to prevent mechanical stress on solder fillet, which may result from the warping of printed circuit board.
  • Confirm the residues of the flux in solder do not affect the product.
  • Confirm the products are corresponding to conductive adhesive when used in place of solder.

Precautions for soldering with lead-free solder

  • In lead-free soldering, temperature may rise higher compared to eutectic solder. Confirm there is no problem under actual soldering conditions.
  • The lift-off phenomenon may occur for both-sided mounting board with through holes. Confirm the connective strength of solder in the actual board beforehand.

Washing

  • Confirm that the ionic residues in the solder flux do not remain after washing because it may cause deterioration of moisture resistance and corrosion resistance when these substances are attached to the products.
  • Confirm the reliability in advance when using no washing solder, water or soluble agent.
  • Since lead-free solder may contain much of the ionic materials, use the RMA type solder or flux or wash sufficiently.
  • Wash thoroughly after soldering to remove ionic substances like sweat and salinity. Control washing agent appropriately to remove whole ionic substances. Consult KOA when using washing agent such as acid, alkaline, and organic solvent other than alcohols.
  • The ultrasonic washing may destruct the products due to resonance by vibration. High hydraulic pressure may also damage the products. Consult KOA for the washing conditions in advance.
  • Dry the products sufficiently after washing.

Dispose of the products

  • Confirm the related laws and regulations for appropriate handling and disposal of products or packing materials.

Common matters in the products for surface mount devices

Since the distortion of printed circuit board causes stress to the products, pay attention to the following items.

  • Arrange the long side of the chip resistor parallel with the direction of the smaller thermal expansion coefficient of printed circuit board.
  • In cyclic thermal stress, the crack at the solder fillet may occur because of the difference of thermal expansion coefficient between the products and printed circuit board. Design carefully the size of the lands, the amount of solder, and the radiation of heat from printed circuit board. Be especially careful for the large size of resistor more than 5.0x2.5mm.
  • Crack at the solder fillet may occur in the cyclic thermal stress because the thermal expansion coefficient is different between the product and the printed circuit board. The land size, amount of solder and heat radiation from the printed circuit board are needed to be designed carefully. Especially the large size resistors that are larger than 5.0 x 2.5mm needs attention.
  • Make a proper layout to avoid the stress from the warp or deformation of the board. Otherwise, solder cracks may occur or the products may be damaged.

  • Pay attention to the products mounted on the periphery of the board or near the connectors so that no stress is placed on the products when you push/pull the connectors.
  • Pay attention to the layout where the products are mounted near large components to avoid the crack, because the stress works in the direction to large components when the solder solidifies.
  • Design each size of lands to be equal. Different land size may change characteristics or cause cracks and tombstone effect while the solder is cooled down.

Mounting and soldering

  • Imperfect adjustment of mounting machine may cause cracks, chipping and alignment error. Check and inspect the mounting machine in advance.
  • Set the backup pins in proper layout otherwise the components mounted on the backside of the board are damaged. Do not set these pins at the position of the nozzle.
  • Adjust the bottom dead point of dispenser away from the board when you apply adhesive.
  • Confirm that the products are corresponding to flow soldering when you perform it.
  • Pay attention to the amount of solder because improper amount of solder place large stress on the products and cause cracks or malfunctions.

Soldering by soldering iron

  • Solder by soldering iron at the temperature specified in technical specifications or precautions for each product.
  • Perform preheating as much as possible.
  • Keep the tip of the soldering iron away from the body and the termination of the products.
  • Avoid damage and physical shock to the products, when you nip the products with hard tools like pliers and tweezers.

Common matters in axial lead type products

Mechanical stress on axial lead type products

  • Pay attention to resonance by vibration after mounting.
  • Do not add bending or twisting stress to the product body.
  • Fix large size products firmly.
  • Take larger curvature radius to avoid excessive stress on the root of the terminals when you need to bend the lead wires. Excessive stress, if applied, may make the lead wire separate from the electrode cap and damage the product.
  • Do not add excessive stress to the product body when lead wires are cut or clinched by mounting machine.

Temperature rise of axial lead type products

  • Pay attention to the heat radiation and interaction to other components, because large size resistors generate large amount of heat, when the rated power is applied.

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