Laser Structuring Method Embeds RFID Tag Antennas in Goods

By Claire Swedberg

German company LPKF says its technology can make tag manufacturing faster, is more versatile by enabling software changes to an antenna design, and is capable of creating small tags embedded in plastic items or parts.

Some RFID label manufacturers, as well as vendors of goods tracked via radio frequency identification, are taking advantage of a new technology developed by LPKF Laser & Electronics AG that enables the laser-printing of an antenna and circuit board for RFID transmission.

LPKF's Laser Direct Structuring (LDS) technology, the German company reports, can reduce the size of RFID tags, thereby making the tag manufacturing process less expensive, while also making it possible for a tag to be incorporated directly onto an item being tracked—even if that product's surface is three-dimensional. Initially, says Stephan Krause, LPKF's LDS strategic product manager, the LDS technology is being employed by Swiss electronics firm Harting Mitronics, as well as by at least one mobile phone manufacturer, to print RFID circuit boards and antennas with laser printers. Krause's company may now move into the Near Field Communication (NFC) RFID market, he adds, as mobile phone manufacturers begin incorporating the technology into their products for contactless payments and other NFC-based applications.

LPKF's Stephan Krause

The LDS process consists of first designing a hard plastic item, such as a hearing aid, automotive part or mobile phone handset; molding that piece of plastic from granulated plastic containing a special additive; and then placing the molded plastic item into a laser machine, which then writes the circuitry onto the part's surface by activating particles of the plastic additive. This can be accomplished on a three-dimensional shape or item, such as a ball, Krause explains. Metalization of the laser-printed structure is performed in a copper or other metal bath, in order to create plating.

LPKF utilizes a variety of RFID chips supplied by NXP Semiconductors. Each chip is laid with the laser-structured antenna, and is then soldered in place, resulting in either a very small RFID tag integrated directly into a product, or a small RFID label.

"The advantage is you can now put circuitry on a three-dimensional part," Krause states, by printing the antenna onto something that may not have a flat surface. "The whole process reduces components, such as screws or glue that would be used to attach a label to a product or asset." Compared with the traditional method of manufacturing RFID tags, he explains, the LDS process eliminates the need to affix a tag to a part, ensuring that tags will not fall off or lose adhesion.

LPKF first investigated the laser printing process on circuits in 2000, and gained a patent prior to commercializing the solution in approximately 2009. The process is commonly used to manufacture smartphone antennas, and to produce components for light-emitting diode (LED) lighting systems, as well as in the automotive industry. A year later, the firm began offering the technology as a means to create RFID tags. The company sells the LDS equipment necessary to accomplish the laser printing, and also handles chip application. Some smaller companies, however, have asked LPKF to design and apply the tags at its German facility.

Harting Mitronics, the earliest adopter, has been using LPKF's LDS technology since 2004 for a variety of applications that required an antenna and a circuit board, according to Albert Birkicht, Harting's managing director, but it began utilizing LDS to create ultrahigh-frequency (UHF) RFID tags only during the past few years. Harting makes custom products for customers in the railroad, factory-automation, wind-energy and telecommunications industries. In recent years, Birkicht says, the firm looked into employing RFID to track its work-in-progress, but determined that in order to do so, it needed to deploy a laser-printed solution rather than applying tags to those items, in part because such tags were difficult to read when placed on metal.

Harting had already been using molded interconnect device (MID) technology to integrate electronic circuits into injection-molded parts, Birkicht says. This technology is deployed in areas where space or weight may be a problem for electronics. The LDS method is one version of the MID process, he notes, but specifically provides laser-printed antennas for incorporating a tag into an item.

"LDS is flexible," Birkicht says, "and allows us to make quick software changes" to a design.

LPKF may offer an NFC-based solution for the mobile phone industry, Krause reports, though the firm has yet to determine any concrete plans to do so. He declines to compare the process' cost to that of a standard RFID or NFC tag production, noting that information calculated by customers is not typically shared with LPKF.