Standard RFID tags have undergone great levels of cost reduction. RFID tag cost is at the cent level. Can that be replicated in RFID sensor tags?
RFID tag cost has always been a major issue in RFID technology implementation. Since it has always been thought as a high volume product – a tag per container, box or even item – tag price needed to be kept as low as possible.
Cost effectiveness of RFID inlays
RFID inlays are the cheapest version due to both the electronics simplicity – a single RFID IC bonded to the RFID tag antenna. No extra electronics, the IC is in die format, no casing at all, and the substrate is basically paper. Most inlays use a protective film but that’s all included in standard RFID inlays. Pretty cost effective – can be found in the market starting at around USD 0.05. This video shows part of the inlay assembly process.
RFID inlays vs. RFID sensors
Moving to RFID sensor tags, the idea for low cost products would be fairly similar: the less electronics the better, all of them in dies if possible and a paper-like substrate. However, there are certain challenges here.
Sensors are expensive by themselves
You can’t think about sensors for USD 0.05. There’s simply no way. Standard digital temperature sensors can be found starting at half a dollar, 3 axis accelerometers can start at around a dollar and you can move up to a hundred dollars for specific load cells.
When you move into analog sensors to monitor specific magnitudes – you may want to use strain gages, thermistors or other analog sensors – you need the appropriate electronics for a conditioning circuit which of course has a cost, even if small, depending on the sensor and performance required.
The fact that these components are much more expensive than the RFID tag itself requires a mind shift from RFID tag cost of USD 0.05 to RFID tag cost of at least over a dollar for sensor tags.
Technology limitations for the substrate
While RFID inlay manufacturing machines are very well developed for a single die attached to an antenna, the technology is not ready to implement multiple dies in a single inlay. Picking and placing multiple dies – RFID IC, sensor and possibly other electronics – is still a challenge so the standard substrate to use is a PCB.
This of course increases RFID tag cost and size, two things you will never want in your products. Unluckily, this is where the technology stands at the moment. New processes and products are being researched so keep an eye on them (find here an interesting example).
In summary, even though battery-free sensors will continue to evolve in technology, sizes and cost, you will never have a sensor for the price of just the identification. Comparing ID tags with sensor tags and thinking the cost will be similar is a mistake as the communication is not the expensive part but the sensor is.