FREQUENTLY ASK QUESTIONS ON RFID TAGS AND INLAYS (FAQs):
1. Will one of the systems using one of the frequencies of 13.56 MHz, 915 MHz and 2450 MHz be used in all applications?
- 915 and 2450 MHz are preferred for its longer read distance of 10 feet or more in free space. But each has its limitations.
- 915 MHz RFID tags are typically larger with tag area in the range of 2-inch by 3-inch and thus making them not suitable for smaller items.
- Both 915 and 2450 MHz are higher in frequency with deleterious effect when placed against water or liquids with water, or even substrates with excessive water or moisture.
- Both 915 and 2450 MHz are negatively affected by falling rain and snow and limit their usefulness for applications with high probability of outside exposure.
- UHF and Microwave frequencies may also cause user health concerns.
- 13.56 MHz RFID tags can be engineered for any size larger than 0.5 inch. It is not sensitive to moisture, water and snow.
- 13.56 MHz RFID tags has maximum read distance of 5-foot. It requires more elaborate effort to tag and track larger boxes.
- It is unlikely that one of the technologies based on anyone of the frequencies can provide the full solution.
- May be a combination tags with a 13.56 MHz chip and either one of the 915 or 2450 MHz chip will working together is the best solution for the larger boxes.
2. What are the advantages of SOLDERED interconnected RFID tags and compression-formed and adhesive bonded tags?
- Soldered tags uses pure copper rather than screen-on silver inks to provide the most consistent conductance and thus higher performance by approximately 10-20% depending on the frequency of operation.
- Silver conductive inks while has the advantage of the “additive” technology, but at the cost of conductivity variation, fine-line limitation and less conductive and thus shorter read distance. It is not usable for the 13.56 MHz RFID applications.
- Silver conductive ink antenna typically uses conductive adhesive bonding of chip (some uses Z-axis conductive adhesive) in a flip-chip mode. The process is typically higher in cost and slower in processing. It is only useful for 915 and 2450 MHz RFID tags.
- Soldering using the patent-pending “chip-jumper” approach is an industrial standard printed wiring board approach that have been proven for the ultimate fast surface mounting assembly with lower cost equipment at extreme high rate of 72,000 units per hour per assembly station. There is no major capital requirement as required by flip-chip process.
- Soldering is intrinsically higher temperature operation and thus tags are also useful for all operating conditions below the soldering temperature.
3. What are the limitations of thick-film printed antenna RFID tags?
- Printing can be a fast process but is limited for the very fine features. Thus printed antenna traces work better in the 915 to 2450 MHz tags that typically require only one single loop. It is particularly difficult for the smaller area RFID tags for 13.56 MHz.
- Conductive inks must be precious metals so that oxidation will not occur. This is intrinsically more expensive than copper films used in subtractive process.
4. Why are soldered tags so rarely used?
- Soldering is performed at temperature exceeding 250°C and requires substrate film to be able to withstand that temperature. Polyimide laminate with copper conductor and similar substrates are expensive (sometimes over $100 per pound vs $6 per pound for polyester substrate) and are used only for extreme applications requiring such substrate flexibility.
- AVANTE solves this problem with a proprietary low cost yet high temperature stable and moisture stable substrate for the RFID applications. This enables the use of soldering interconnections for RFID applications at lower cost than silver thick film process.
- A combination of inlay patterns can be used to optimize the copper laminates with minimal waste.
- In addition, AVANTE developed the patent-pending “chip-jumper” approach for mass production with this easy to handle form factor for soldering.
5. Why is relational check-code important for RFID applications?
- RFID tags are ISO 14443 or 18000 protocols that allowed open architecture in reading and encoding. That is, anyone can write onto the tags once the tags left the installation operation. When used by proper users, this is one of the important advantages of RFID over the barcode.
- Relational check-code is devised to tell if encoded data in the tag are authentic and made by authorized users.
- Additional relationship can be built-into the code to document who encoded specific data. Any additional encoded data by another users will create another traceable relational codes to provide an audit trail.
- Any encoding or modification by an unauthorized user can be easily recognized.
- This patent-pending application of the relational check was created to enable this technology for use in mission-critical applications.
6. What is the cost of the RFID inlays made with soldered interconnection?
- The cost of RFID tag (based on 13.56 MHz) has been dropping dramatically. At this time (June of 2007), the costs range from $0.25 to $1.0 depending on the volume.
- Instead of more expensive for its performance and reliability, the costs are actually less than all of the other methods of making RFID inlays and tags.
- The same costs applied to the 915 MHz and lower for 2450 MHz tags if the chips are priced the same at $0.10 to $0.20 each depending on volume.
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