The touchpoint embeds an NFC tag that consists of a small system on a chip (Integrated Circuit) and an antenna placed behind a printed icon or sticker for communication with the smartphone.
NFC Tags and chips
The two components, the NFC chip and antenna, work together to form a self-contained functional device.
Different tags may use different types of chips. A chip is tuned for a specific application, it can differ by its memory capacity and its compliance to a given specification.
For instance, STMicroelectronics’ portfolio includes NFC chips dedicated to ticketing (ST25TB) and traceability (ST25TV) as well as others dedicated to wireless pairing or brand recognition (ST25TA and ST25TV).
The assembly of an integrated circuit and an NFC antenna makes the touchpoint different from traditional labels or stickers and may require special attention.
The ST25 series offers a wide range of NFC RFID tags and chips, that can be assembled in labels, stickers or in specific packages. Tags can be ultra-thin, waterproof and/or shock resistant in order to be aesthetically and easily integrated in product shape such as a garment, bottle, or key fob, for instance.
The NFC chip itself embeds specific features dedicated to NFC applications. The ST25T series proposes various features (TruST25 digital signature, passwords, and a robust memory up to 64Kbits) that improve brand interest for consumer engagement applications.
The touchpoint contains an NFC tag and is what is added onto the consumer product.
Recommendations for the physical implementation of an NFC touchpoint
NFC technology offers you a unique opportunity to develop interactive and dynamic mobile applications to enhance the user experience.
Here are some recommendations to consider as you start your NFC project.
An NFC Forum certified tag Integrated Circuit (IC or chip)
This will ensure consistency of behavior across NFC implementations and sets the foundation for interoperability with NFC smartphones, but also with NFC readers which are used to program the tags in production.
The certification programs verify the tag’s responses to all sorts of phone commands and requests (“digital”), and also checks the operating volume of the tag (“analog”).
Moreover NFC-enabled smartphones supporting NFC are NFC Forum certified, so using a tag AND a reader that are NFC Forum certified guarantees interoperability.
STMicroelectronics offers a number of different certified tag ICs offering many options in terms of memory size and features.
Selecting an NFC “Type 5” tag
The NFC Forum defines 5 types of tags, but not all of them have the same performance level.
The technology used in NFC Type 5 tags complies with the ISO/IEC15693 standard as opposed to other types which are based on ISO/IEC14443 technology. Thanks to a high-power reader infrastructure where high data rates are important, ISO/IEC14443 based solutions are mainly used for transportation, contactless payment, passports etc.
Note that for the same operating volume as with NFC Tag Types 1 to 4, Type 5 tags will enable you to design smaller sized antennas.
With Type 5 tags, the rule of thumb for estimating the operating range is that it is approximately the same size as the reader’s antenna.
Then knowing that industrial RFID readers can offer large antennas such as gate or portal readers, the range can go up to around 1 or 11/2 meters between two gates.
This uniquely enables you to combine asset tracking in your factory and enhanced user experience with consumers.
The touchpoint look and feel
The first step is to determine how users will identify the product supporting the NFC technology and where the touchpoint is located. As NFC operates within a few centimeters this is quite important.
Avoiding confusion between touchpoint and information label
It is a good idea to add an informative label to your NFC-enabled products to explain to consumers how to use this newly available technology.
But one should pay attention to not confuse consumers who might not end-up knowing where to tap their NFC phone (on the label or on the product?)
Visual identification of the touchpoint
One option is to use the NFC Forum logo and locate it at the exact position over the tag.
The “N-mark” logo is the recognized international NFC symbol recommended by the NFC Forum, the association driving the NFC ecosystem.
The use of the NFC Forum logo is free-of-charge but requires you to accept their N-Mark Trademark License Agreement * for a consistent user experience.
If the NFC Forum logo does not correspond to your communication graphics, another idea is creating your own logo, suggesting a short-range wireless communication.
Using generic wireless communication pictograms is another good way to indicate the location of the touchpoint.
Determining the optimum touchpoint position on the product
The touchpoint position is where the NFC tag will be located on the product.
To read the tag, the user must be able to place their smartphone within a certain area around the tag; this is known as the operating volume.
The user must have free access to the touchpoint’s operating volume.
The above-mentioned operating volumes are defined with NFC Forum reference readers.
In practice, tags will operate with a wide range of NFC phones with each having different ranges and characteristics. As such, it is recommended to follow these guidelines.
Defining the best touchpoint antenna size
The operating volume is a key factor of the NFC user experience, and as such it should not be compromised.
For that, you need to ensure that the operating volume is as large as possible to help the user easily interact with the touchpoint. With a large operating volume, the transaction can start earlier and saves time for the user.
Using NFC certified tags to ensures the best interoperability and maximum operating volume is also going to contribute to offering a good user experience.
In many cases in consumer product implementations, the NFC tag antenna is tailored and personalized to the application to fit the product and the brand marketing guidelines. In that case, do not compromise on the tag size, use the space available for the antenna as much as possible.
There is no absolute rule in terms of operating volume for a good user-experience. But based on field tests from early adopters, a basic recommendation is to design your tag antenna such as to ensure a 2cm reading distance between NFC smartphones and your in-situ tag.
Finding the best antenna position for transactions
When the smartphone and the touchpoint (tag) are brought close together, both antennas must be face to face for an efficient transaction.
The position of the NFC tag must be carefully chosen to ensure the shortest distance between the touchpoint and the smartphone for best performance.
A concave design such as the surface of a bottle increases the overall distance between the smartphone and touchpoint.
A flatter surface reduces the distance between the tag and smartphone antennas. This provides a better user experience:
Placing the tag on a convex surface is better because the phone can get closer to tag. Using a concave surface is less effective as the additional gap keeps the phone further from the tag, making it more difficult to establish a connection.
Evaluating the impact of the environment on the touchpoint performance
NFC technology works with many types of material, such as plastic, liquids, fabric, glass, wood, paper, and cardboard, as well as metal under certain conditions.
The following material may impact the touchpoint performance:
- Metal: the quality of NFC transactions may be affected by nearby metal surfaces which will distort the magnetic RF communications. To avoid this, it is best to choose a tag with a ferrite protection layer (see figure below)
- Glass and liquids, to a lesser extent, may also reduce the NFC range
Because the touchpoint is made of an integrated circuit (IC) attached to an antenna. Which has its own mechanical constraints, the following environmental factors can damage the tag:
- Mechanical pressure applied on the tag
- Extreme folding or bending of the tag
- Extreme operating temperature, and temperature cycles (washing machine like)
- Other environmental factors such as extreme humidity
You might be surprised during your design to discover that a tag might behave differently in “free air” as opposed to “in-situ”, i.e. final tag attached to your product.
So, when you evaluate your NFC touchpoint performance, always do it under “in-situ” conditions.
Intermediate testing of your NFC touchpoint and smartphones
Your NFC tag is now designed, you chose a large enough antenna to allow the best possible performance, selected the optimal location of the touchpoint but there is one more thing which needs to be done: testing your implementation with a large panel of phones, and under in-situ conditions.
The key points of this real-life operating distance assessment are:
- Focus on tag detection (for instance using tags with a basic URL programmed)
- Use the actual final product and final touchpoint (material, geometry)
- Use various phone makes and models
To illustrate this, here is an example of range measurements for a given tag with various phones.