Proposed Standard for Ink Antennas

Precisia, a company that develops conductive inks for RFID antennas, promotes a standardized way to test such products.
Published: October 15, 2003

By Jonathan Collins

Oct. 16, 2003 – Precisia, a company formed by Flint Ink to develop conductive inks for RFID tag antennas, is pushing for rival vendors and RFID standards organizations to work together to develop a standard for testing and rating conductive inks and the antennas that are made from them.

Precisia’s Lawrence

“Accurate testing of these new technologies will help speed up its time-to-market and provide assurance that investments in RFID solutions are not wasted,” says Dan Lawrence, director of technology and commercialization at Precisia. “But vendors and end users have to find common ground on testing.”

Ann Arbor, Mich.-based Precisia recently spelled out the conductive ink tests it has developed. These tests include ways to establish the electrical resistivity, crease resistance, temperature, humidity, hardness and ink adhesion of different inks in antennas of different sizes and shapes.

Conductive inks have to perform well—that is, they have to provide enough conductivity to enable the chip to receive power from the reader and send back a signal. The ink antennas may also have to have a certain appearance if they are used on the exterior of boxes. So Precisia has developed ways to measure the color, optical density and rub resistance of any ink.

It has also developed ways to measure resistance that has to take into account the length, width and thickness of the ink sample. “The bulk properties of copper [antennas] are understood and copper strips have the same thickness each time,” says Lawrence. “With ink, we are still developing different thicknesses for different results.”

Another key factor to be measured is the effect of creasing on the electrical performance of an ink. In Precisia’s test, a standard weight is rolled along a loop with the ink so that a crease is formed. In addition to testing and rating the effect of the crease on electrical performance, the company also tests the number of creases an ink can take before failing.

Another test developed to determine the adhesive qualities of the conductive inks also rates their performance. After cross hatching samples, the ink is rated according to the level of flaking the cuts create. Precisia’s classification scale runs from 0, where no flaking occurs, to 5, where more than 65 percent of the ink surface flakes.

Additional tests assess the read range of any ink antenna to rate the function of distance and directionality on the antenna, as well as the effects of differing orientations.

The Auto-ID Center has already established a packaging special interest group that could develop testing benchmarks of its own, but Lawrence believes that that is not the only way to achieve standards. “Over the next year or so, industry de facto standards could also develop,” he says.

What is vital, maintains Lawrence, is that ink vendors work closely with the final customers for their antennas: “We have to keep end users involved to understand the constraints of the packaging the ink is to be used on.”

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