If a relay is coated with urethane or silicon that contains siloxane, will contact failure occur?


If the side of a relay is coated with silicon that contains siloxane (low molecular-weight siloxane reducer) in the coating agent, will contact failure occur? What about urethane coating?



Use a siloxane-free coating agent. Even low molecular-weight siloxane-reduced agents may cause contact failure of relay contacts. Urethane-based coating agents can be used.



If a coating agent, packing resin, etc., enters the relay, contact failure and/or malfunction may occur. Please prevent them from entering the relay. For coating and packing, use a plastic-sealed relay. Use silicon-free coating and packing resin.

Type Usability Features
Epoxy Applicable Excellent Insulation
A little Difficulty in coating workability
Polyurethane Applicable Excellent insulation and coating workability
Don’t allow the solvent to adhere to the relay during work
Silicon Not Applicable Excellent insulation and coating workability
Silicon gas may cause relay contact failure.
  • Siloxane
    Siloxane is highly permeable and penetrates into the interior of plastic-sealed relays.
    Even a siloxane-reduced agent contains siloxane, which only prolongs the time it takes to enter the relay.
    After entry, a silicon oxide film is formed on the contact, causing contact failure. Therefore, silicon-based coating cannot be used, even on only the side of the relay.

  • Urethane/epoxy
    Urethane and epoxy coating agents can be used but they may contain a small amount of siloxane. Please check the ingredients before use.

Silicon (containing siloxane) Coating agent: Prohibited

  • Other coatings
    Please use siloxane-free (silicon-free) resin molding, potting, and packing on the PCB surface.

For more information, see Safety Precautions for All Relays


Quick tips

When a coating (including mold, potting, and packing) is applied, make sure that the insulation property does not deteriorate and that the material (resin or metal) used for the relay is not affected before selecting.


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