Will contact failure occur when flux enters?

ID: FAQE10084E



In the flux application process, contact failure occurs when flux enters the relay and adheres to the contact. In addition, if it adheres to the driving part or electromagnet part of the relay, it may cause malfunction.



  • In the flux coating of a flux-resistant relay, when the flux level is higher than the fitting part of the relay base and the case, the flux enters the inside of the relay. Infiltrated flux moves inside the relay by the heat of the solder and adheres to the contact part, causing contact failure.
    Flux coating of a flux-resistant relay
  • When a plastic-sealed relay is used to mount on a PCB and the relay is accidentally dropped during mounting, the epoxy resin (bond) that seals and adheres the base, case, and terminals may crack, resulting in a failure of the contact or relay itself.


  • Check and control the liquid level in the flux application process.
  • Do not use dropped relays.

For more information, refer to The SOLUTIONS [General-purpose Relay Edition]: case 07 Faulty Operations by Entering of Flux.

Quick tips

If it is necessary to clean the PCB in the mounting process, consider using a plastic-sealed relay.

Product category Relays Signal Relays Power Relays
Classification Trouble shootings
Related keywords
  • Signal relay
  • Power relay
  • Flux penetration
  • Contact failure

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