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Know what you are buying. All RFID tags are not the same.

 RFID 401: Tag quality and reliability

RFID systems for libraries are a great benefit. When they work well they can contribute to a libraries’ efficiency and enhance customer service. However, RFID systems don’t always work the way they should. Some libraries may have recognized the problem, but may not take the necessary action to do something about it. This may be because of the difficulties to diagnose the original problem, or maybe because of the disturbing thought that a strongly recommended system has defects.

The reason for these problems has been that RFID tags performance weakens over time. The read range shortens and in the end the tags do not work at all so the whole system fails.

But why is this so? The tags have been bought from a reliable supplier and they are compliant with the requirements of an ISO standard. The result is that all the tags are not the same, not even when they are compliant with an ISO standard. This shows that an ISO standard does not define quality and reliability. There are also tags with purposes that do not require several years of durability, for example tickets for ski resorts or tagging on clothes in retail stores.

Tag reliability is based on the tags design, materials and construction methods. The choice of the materials in these components can have a large impact on long-term reliability. Over time, for example some adhesives can introduce or accelerate corrosion in the bond between the chip and antenna. Therefore it is important that the tag manufacturer pay close attention to the choice of tag components.

A Non-Working Tag

RFID tags fail in several ways. High electrical resistance between the chip and antenna, cracks on integrated circuits, the attachment between the chip and the antenna can fail and metal fatigue can cause tag failure in which mechanical stress is usually the main reason for tag failure. Library items with the tags attached to them are often bent, twisted and subjected to pressure.

What happens when the tag does not work? Usually tag failure can be discovered when the tag read-range weakens or drops off. The detection system or hand reader cannot read the tag. Errors can also occur during the reading of multiple items showing not reliable performance.

Tag Tests

How do you know which tag can be used for years? The most reliable test is to see how it performs over time, but who will wait for 15 years to see if a tag has a needed reliability. An alternative is the accelerated aging tests which are routinely used in the electronics industry.

What has been done in such a test? Tags are subjected to various configurations of heat and humidity over 15 weeks, after which they are tested and inspected. These experiments are closely monitored and can be reproduced with some precision, so that the performance of one sample can be compared to another.

At 3M, tests for tag durability have been done for years. 3M has field data from 8 years of installed tags which provide us with a high level of confidence that our tags will last significantly longer than 8 years. At the same time we have done comparative tests for tags from different RFID suppliers.

Next time you are acquiring RFID tags for your library, ask from your supplier, are the tags they are selling tested for long-time reliability, which test methods have been used and have the tests lasted longer than one week?

Please read also RFID white paper 401 with detailed information about the quality and reliability of RFID tags.

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