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Written By Louis Sirico
“O tag, where art thou?” That is the question your RFID reader keeps asking thousands of times per second. Most of the companies that supply RFID-tagged products to the major retailers or the US Department of Defense have realized that simply slapping tags on their products isn't going to be enough to keep their customers happy. When tagged products arrive at the distribution center, some of the tags fail to read, even though the tags are functioning properly. What's the secret to producing stellar read-rates? Location, location, location.
RFID tags are not like bar codes. Just because you see a tag doesn't mean your RFID equipment will see it. Contrarily, if you can't see a tag, it doesn't mean your RFID equipment won't read it. Confused yet?
Successful suppliers understand some basic concepts about tag placement and have taken the time to consider the complex journey of a product from manufacturer to retailer and the different ways a tag's readability may be affected. They have chosen their real-estate wisely and placed their tags with care and precision. It is time and money well spent because if your tagged product doesn’t read, either your customer will catch it and charge you a handling fee, or worse yet, they won’t catch it so you’ll loose the cost of the product, your customer’s inventory will be wrong, AND you’ll have to send a replacement. Exception handling is by far the more costly scenario. Either way – you’re gonna pay.
Your customer’s environment is different than yours.  Yes, this is stating the obvious, but up until now, you probably didn’t care. Now, you need to care. Retailers have an extremely different design approach to their RFID solutions than their suppliers because they are dealing with thousands of companies shipping a wide range of products. Therefore, they will optimize their equipment configuration for the average product, not your specific product the way you will.
While the physical layout of your distribution center and the retailer's may be similar, there are several complicating factors that can negatively impact the readability of your tags. First, it's at this point in the supply chain that your product may come in contact with other products – either on a conveyor or as part of a mixed pallet. This means that your case could be next to one that includes metal or water - elements that can affect readability. Second, some retailer's distribution centers move cases on high-speed conveyors that operate at 600 feet per minute and the retailers expect tags to be read at that rate. However, few manufacturers have tested their tags on conveyors that run above 300 feet per minute. But wait, the complications don't end there. The biggest infrastructure challenge is the retail store itself. Stores receive loose cases of products piled into the truck (like in the picture above). Once unloaded from the trailer, products may be placed on push carts, hand carried, and conveyed. The problem lies in the lack of conformity of movement. Retailers are most interested in what direction products are moving. They want to know as products come in through the dock doors, move from the backroom to the sales floor, leave through exterior doors, and finally when the case is put in the trash. Many manufacturers have only taken into consideration how cases are moving in one direction - out. In simple terms this means that your choice of tag and tag placement must be suited for the most challenging environment, which is most likely outside your facility and scope of control. Since your retail customer has little control over what RFID tag is used and where it is placed, they are relying on you to tag products correctly. You want to tag it right? Here’s the stuff you need to know: What RFID Tag To Use?  Most likely, your current bar code label is going to be replaced by a label with an RFID tag in it, also known as a smart-label - like the one pictured left. The characteristics of the tag in your label are very important.
The Standard - The global standard for RFID tags used in the supply chain is EPCglobal™ Class 1 Gen 2 also known as ISO-180006-c. You can narrow down your shopping list by only considering tags that are certified by EPCglobal™. The complete list is published and can be found here. The certified tags come in a variety of shapes, sizes, and prices. At this point, you need to select a few different tags for testing with your products. You may decide to use different tags for items, case/cartons, or pallets.
In What Geographic Areas Will The Tag Operate? Different regions of the world have different standards regulating the use of radio frequency (RF) emitting products. If you are tagging in the US and shipping to a US destination, then a tag suited for North America is fine. However, if you’re tagging in Asia and shipping products to both Europe and the US, then you require a tag suited for international operations.
Tag Size - Size DOES matter - a larger tag antenna normally provides greater read range and better overall performance. However, a 4” x 4” tag will not fit on a bottle of aspirin.
Orientation Insensitivity - Remember, your product may be flipped in any direction once it leaves your facility. The tag may even end up facing down on a conveyor. Some tag antennas are designed for operation in environments where orientation is not controlled, such as airline baggage handling.
Temperature and Humidity - Be sure to note the temperature and humidity extremes that your products are exposed to and make sure that the tags you select are rated to operate within those extremes. More importantly, double-check the type of adhesive used to affix the tag on the product. If your tag is going to get frozen or wet, you don’t want it to come off because it no longer sticks. A special coating on the label face may also be needed to resist water.
Additional Memory - There are tags that have additional memory capacity that may be used to store information such as date of manufacture or expiration, but that don’t affect tag placement so we’ll save that for another discussion.
Cost - A better performing tag may cost a little more, but it could result in huge savings later on. For example, if you’re debating between the 10¢ tag vs. the 12¢ tag, consider this: a 2¢ difference adds up when you consider thousands, if not millions of products, but look at what you’re paying per year for replacing lost orders. One supplier was losing $3 million per year in lost product before implementing RFID using a 12¢ tag. They tested the 10¢ tag, but it didn't perform as well. Using he higher priced tag, they only lost < $500,000 per year - a savings of $2.5 million per year. That paid for 20,833,333 tags.
Where do you stick it?For most products, you can’t just put a tag anywhere on the product and expect it to read 100% of the time. There are several reasons for this:
 1) The composite materials of both product and the product packaging - Radio frequency waves can easily pass through certain types of materials; while other materials can reflect or absorb the RF. You can’t see this with your eyes, because light waves (and therefore bar-codes) reflect differently. The image to the left illustrates how your RFID reader “sees” a box with a flash-light in it. The red color means the RF waves are not passing through the product, while the green areas show strong signal. The tag will read better in the green areas than the red areas. Click the picture to enlarge it.) |
 2) The position of the products inside the packaging.
The picture to the left shows an open box with a DVD player in it. The metal components of the DVD player will reflect the RF waves of the tags used in supply chain operations. If you look closely, you can see there is card-board packing between the side of the box and the actual player. Since card-board is a RF-friendly material (something that lets RF waves pass through it easily), it provides a better location for the tag than the area near the metal. |
 3) How products sit in the case/carton.
For supply chain RFID tags, products that contain water can be challenging. Water will absorb some of the RF signal therefore making it difficult for tags to be read. The tag is less affected when there is an air gap between it and the water. Take the case of water (pictured left) as an example. The air gaps between items can be used to improve tag performance. By placing the carton tag at the top on the outside of the box, read performance is good.
There are some tags that work with both far field and near-field antennas. By using a near field antenna and tag combination it is much easier to overcome the water problem. |
 4) How the cases/cartons build a pallet.
When cases and cartons are stacked on top of each other, it can be very challenging to read all the tags, especially with pallets of mixed goods. The picture (left) illustrates how your RFID reader “sees” through the boxes on this pallet. The darker green, the better the readability. Some cases are missing entirely, which means they cannot be read at all while other cases are white showing they are read very little. As you can see, there are areas that RF waves can not pass through. That’s why it’s important to consider RFID when building pallets. When receiving pallets, the retailers are focused on reading the single pallet tag that describes the contents. But if all of the case/carton tags can be read as well, the retailer can verify that all the products are there. One simple way to help is to have as many tags facing out as possible. |
Test, Record, Re-position, Test, Record…Now that you know the main factors that affect tag performance, it’s time to start testing your tags in different positions. This can be a very monotonous process. The tags that you selected earlier in the process now get affixed to your products and then (hopefully) read by your RFID equipment. When you consider all the different tags, tag placements, orientations, and hardware configurations, there can be literally hundreds of different test scenarios, each with different results. (That's why we said to only select a few tags.) Ultimately, what you want to know is what tag to use and where does it go on the item, case/carton, and pallet.
 Let’s look at the example pictured right - a case of deodorant (click picture to enlarge). You’ll note that when the tag is placed on the bottom right, it gets only 20%, yet the same tag placed in the top left gets a 100%. The water in the product is concentrated at the bottom and absorbs the RF signal. At the top, there is an air gap that lets the RF waves travel through.
A couple rules of thumb to remember :
- Place the tag on the exterior of packaging. It makes it easier to replace failed or poor performing tags.
- Avoid crush/fold points of the box. If a RFID tag is "slapped" on the box just as it goes out the door, and if the tag is on the crush point, the tag readability may be compromised because the antenna can become separated from the integrated circuit.
- Consider the packaging graphics. You don’t want to put a tag over instructions or other valuable consumer information.
- Club stores sell cases/cartons of products as items, so the last bullet applies here too.
- A tag will not read if it's placed on packaging that uses metallic ink.
- Don’t be afraid to redesign the packaging to be more RFID friendly. If you don’t change it, your marketing department will, eventually.
Understand Your Options Now that you know about proper tag placement, how do you go about doing it? There are several options:
1) Bring in outside consultants
Outside consultants can be costly, but the right one can get you started fast, especially if you’re facing a deadline.
2) Use a RFID Lab
The labs have environments similar to retail customers: very fast conveyors and dock door portals. Working with a lab can help you know what kind of performance can be expected once the tagged products leave your facility.
3) Tag it yourself
Do you think you can do it?
For the first two options, you have to consider how many SKU’s you have: ten, twenty, a hundred? Are you going to pay consultants or test labs to tell you where the tag goes on all of them? That will cost thousands of dollars. Plus, you’ll have to pay again for new products or changes to product packaging. Since RFID is not going away, understanding tag placement should ultimately become a core competency for you and your company.
Get Started: Step-By Step
Start by bringing in outside expertise on tag placement to help with a few products. Work side-by-side with the experts so you can learn the techniques and eventually take on the responsibility of tag placement. This will get you up to speed quickly. Examine your highest volume SKU’s and the most physically challenging SKUs (those that contain metal and water). The information provided in this article should give you enough education to intelligently interview applicants. We are also happy to recomend an expert that specializes in this area. Send an e-mail to
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. Please be sure to mention you are looking for help with tag placement testing. We will get back to you ASAP.
Even if you're working with an expert, if you’re not 100% confident about a SKU, send it to a RFID lab. We can also help you to select a quality lab.
Finally, purchase a tag placement tool for yourself. All the experts use them and the picture above shows why you need one. Members of the our community get a DISCOUNT on the product that created these graphics – epcHOTSPOT. You can even download a full working version to try for 15 days. Click here for details.
Don’t forget, you’re going to need to educate operations personnel since they are the people that have to apply the tags. The importance of proper tag placement must be clearly communicated. Some companies have already implemented quality assurance measures to ensure the right tag is being put in the right place – every time. Your customer may not thank you for doing this, but at least they won't charge you - and you'll gain some appreciation of that investment. |
