In the mid-1990s, flexible two-dimensional RFID inlays were introduced to label-converting companies as the basis for manufacturing smart labels. Today, smart labels are used to track products in the supply chains of the world's largest retailers and pharmaceutical manufacturers. Wal-Mart, Target, Tesco and many other companies in North America and Europe, as well as the U.S. Department of Defense, are all in the process of changing over their distribution and supply operations to include RFID.

Since the introduction of inlays less than a decade ago, RFID usage has changed considerably. In these few years, volume has grown from hundreds of thousands to hundreds of millions of units. As the industry has grown and matured, so has the need for consumer goods manufacturers and label converters to expand their product offerings. To provide innovative and value-added RFID solutions, RFID label design is moving from the traditional inlay model to a strap form factor that provides lower cost and greater flexibility.

In order to understand straps, one first needs to understand the evolution of RFID labeling, beginning with inlays and smart labels. From this, straps and the benefits associated with straps labeling will become apparent. As a more flexible RFID packaging solution, it enables manufacturers to better accommodate products tracked at the item- and case-levels in the global supply chain. Straps also provide a tool for cost innovation with high-volume tag production in the assembly line through lower per unit and capital costs.

RFID inlays

An RFID tag typically consists of a conductive metallic antenna with a low-power microchip as seen in Figure 1. When passed within range of an active RFID reader, the tag is wirelessly energized by energy transmitted by the reader. It then communicates with the reader.

Today's RFID inlays are typically manufactured on a reel-to-reel process. The thin microchips are directly attached to a web of plastic on which a series of 2-D antennas have been printed with conductive ink or etched from a metal film. Figure 2 shows one typical method for creating inlays. The output of this process is a roll of fully tested inlays.

From inlays to smart labels

The rolled inlays are in an ideal format to be embedded into labels using the reel-to-reel processing equipment typically found in a label-converting operation. The inlay is usually placed on the bottom side of the label, next to the container, or sandwiched between layers of the label. These “smart labels” are then ready to be placed on pallets, boxes, cartons, crates and other containers in the supply chain (See Figure 3). Inlays can also be embedded in tickets, tags and other form factors. Under today's manufacturing processes, smart labels tend to be the most straightforward, cost-effective way of affixing RFID to containers in a manufacturing environment.

While in the supply chain smart labels have proven to be a successful way to use RFID inlay technology, some drawbacks exist. An extra step is required to attach the label to the container. Smart labels require flat surfaces, a minimum surface area and specific materials for attachment; all of which puts constraints on their use if the product to be tracked has an unusual size or shape.

The flexible form factor

Straps are a new way of creating RFID tags (Figure 4). They reduce some of the steps needed to produce smart labels with a more cost-efficient process, which helps to drive higher-volume production. This new form factor and the technique of applying it also provides greater flexibility in the type of label and antenna used for packaging, as well as the type of product that can be labeled. This flexibility can also deliver advantages in item-level tracking. In general, as RFID tags become easier to use, more flexible and inexpensive, the more they can help reduce the total cost of ownership of manufactured goods.

As an example, consider the Gen 2 strap introduced by Texas Instruments. It offers an improved method for creating RFID tags that greatly reduces, and in some cases, eliminates, the need for inlays and smart labels in the high-volume manufacture of many products. The strap technique separates the two components of the RFID tag, the antenna and the chip, until the user brings them together. This gives more control and choices to the consumer goods manufacturer.

The chips are mounted on small (4 mm × 9 mm) plastic surfaces provided in thin tape rolls. Enlarged metallic contacts on both the plastic surface and the antenna simplify placement of the devices by bringing tolerances well within the normal range of automated container manufacturing.

One method of applying straps is to print the antenna using a conductive metallic ink directly on a container such as a cardboard box. The strap containing the chip is then attached to the printed surface, which creates the complete tag.

When straps are used on corrugated cartons, the RFID module is built into the cardboard so that it is not exposed; not even to the goods packed inside the container. The carton manufacturer prints the antenna on the inner liner, attaches the strap and builds the corrugated layers over it with the module inside the corrugation. The resulting smart cartons, or packages, become premium products in the container manufacturer's line, offering built-in intelligence for tracking through the entire process of manufacturing, shipping and warehousing. Figure 5 shows a box with an embedded strap.

For high-volume assembly line production, the use of RFID straps eliminates smart labels and cuts process steps by the manufacturer, thereby helping to minimize handling and lower overall costs. If inlays and smart labels are no longer needed to attach the RFID tags to the package, the manufacturer can bypass several steps in the manufacturing process. Since antenna manufacturing fits into the established process flows for printing the container, the only additional step is attaching the strap. With a small pitch of just 4 mm, straps can be processed much more quickly than inlays, which have pitch measurements an order of magnitude greater.

Meeting needs with flexibility

The greater flexibility inherent in straps enables them to be adapted to a wider range of label and packaging forms. More important, straps also offer more choices in terms of antenna design and placement. Label and box manufacturers can use one strap as the basis for a wide variety of finished products, such as labels, hang tags, embedded tags, and smart packages. Strap attach equipment is intended to support this wide variety of form factors based on a single strap format. This reduces the cost of the capital associated with starting an RFID tagging operation required for inlays.

Straps can be attached, or embedded, at the beginning of the container manufacturing process to create smart packages that bring greater intelligence to every stage of the supply chain. For manufacturers of end products that go into corrugated containers, cartons with embedded RFID straps relieve the problem of attaching RFID altogether. All the manufacturers have to do is write their identifying codes into the tags using RFID readers. This task does not have to take place on the product assembly line, but at any point or points that are appropriate and convenient. Distributors and retailers can continue the tracking process, as they already are doing with RFID, by reading the manufacturer's information and, if desired, adding their own.

In the case of RFID straps that are attached to individual product items, improved inventory management continues all the way to the retail store shelf and checkout counter. Portable readers can count items on the shelf, check the items individually for information such as expiration dates and update pricing. Reordering becomes faster and more cost-efficient, and shrinkage is easier to control. Additionally, at purchase time, merchants can more readily update their inventory and customer loyalty databases.

Consumer goods and label manufacturers can realize many benefits by using RFID straps. First, straps enable efficient, high-volume production that can meet demands in the millions of units and beyond. Second, the strap attach equipment can be compact and versatile, thus lowering capital costs. And third, this format offers more choices in the type of label being used with antenna design for dry and wet goods. All of these benefits now combine to make a compelling case for the use of straps by today's manufacturer.

Tony Sabetti is the director of UHF Retail Supply Chain Solutions at Texas Instruments RFid Systems, a business unit of Texas Instruments Inc. based in Plano, Texas. He is responsible for TI's RFID initiatives in the emerging supply chain management applications. He has a B.S. degree in Electrical Engineering from the University of Rhode Island and an MBA in Management from Bryant College.