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Mains switch & circuitry Mains switch & circuitry

Summary

  • Failure mode Unsuitable switches of poor quality and poor soldering.
  • Durability feature Use of better quality switches and gold plated connectors.
  • Cost

Good practices

  • Good practicesUse tested switches
  • Good practicesInspect PCB quality

Bad practices

  • Bad practicesTin plated connectors

Key facts

  • 28% of vacuum cleaners failed to meet customers’ expectation of a 5-year lifetime.
  • Which? surveys show that the most common faults are loss of suction, blocked filters and brushes.

Icon key

  • Failure mode Failure mode
  • Durability features Durability features
  • Cost saving Cost saving
  • Low cost Low cost
  • Cost neutral Cost neutral
  • High cost High cost

Key failure modes

Early life

Switches and electrical circuitry should function for many years if designed and assembled correctly, using good manufacturing quality control. However early defects can occur:

  • Unsuitable type of mains switch. An arc occurs every time these open so the materials must survive the expected lifetime of the cleaner.
  • Poor soldering quality on circuit boards.
  • Poor manufacturing quality.

Later in lifetime

Failures after a few  years of use can also occur for many reasons:

  • Mains switch electric contacts are of an unsuitable size, material or the switch contacts exacerbate arcing.
  • No arc suppression for mains switch.
  • Printed circuit boards can fail because of vibration  - poor design can make this more likely.
  • Connectors need to be a suitable type and design for vacuum cleaners, otherwise the cleaner will stop working.
  • Defective components – poor quality counterfeit parts are an increasingly common problem  in products where there is less visibility and control in the supply chain.

Specification for improved performance

The specification below provides the recommended improvements needed to improve product durability. They are ranked from bronze to gold based on the effectiveness of the change in improving durability, with bronze being the minimum and gold being the maximum.

Test mains switch; IPC-610E inspection

  • Electrical switches need to last the expected life of the cleaner.
  • Printed circuit board designs allow for the vibration that occurs with vacuum cleaners and test to ensure reliability.
  • Monitor production quality by inspection and function testing and use IPC-610E for visual assessment of soldering quality.
  • Circuit boards should be tested to ensure that they are able to survive the expected lifetime by specifying that they are fully functional after vibration testing.

Gold plated connector coatings

  • Tin plating is a poor choice because vibration causes fretting that will cause early failure. Specify that contacts in both plugs and sockets have gold plated coatings. This will make only a small increase to production cost, but should eliminate early returns from fretting.
  • Permanent solder connections can be used if their use does not prevent maintenance, such as changing drive belts.
  • Keep internal wires as short as possible to avoid flexing, as this can exacerbate fretting of connectors and could also cause fracture of the wires.

Testing to demonstrate performance

  • Test using the methods in standards as follows: EN 60335-1 for main switch testing under mains power for 10,000 cycles.
  • EN 60068-2-6 and EN 60069-2-64 for vibration resistance for circuit boards.
  • Connectors can be tested using the methods in EN 60512-6-4 Connectors for Electronic Equipment - Tests and Measurements - Part 6-4: Dynamic Stress Test 6d: Vibration (Sinusoidal)

Cost implications

Improved reliability of components can reduce early returns and improve brand reputation which, in turn, can lower business costs and increase long-term sales.

To calculate overall cost savings for your business, use the WRAP cost/benefit analysis tool (currently in draft form and available on request).

Saving

Neutral

Low cost

Quality PCBs

Additional cost for better quality and IPC-610 inspection to prevent early returns due to PCB defects.

Gold-plated connectors

Additional cost for gold plating that will prevent early returns due to connector failure.

Reliable switches

Additional cost for better quality component.

High cost