Schneider Electric Lays Groundwork for Tracking Circuit Boards via RFID

By Rhea Wessel

The solution involves the installation of an EPC Gen 2 RFID chip directly onto the printed circuit boards that the company incorporates into its products, with the board's ground plain serving as a tag antenna.

image_pdfimage_print

Schneider Electric, a global energy-management firm that reported €18.5 billion ($25.7 billion) in sales in 2009, says it has laid the groundwork to begin using radio frequency identification to identify and track the production of every printed circuit board (PCB) it manufactures, and that it expects to begin utilizing the technology within the next few months.

Since November 2010, Schneider Electric has been adding a placeholder for an EPC Gen 2 RFID chip onto all of its new PCB designs, in order to pave the way for the project. The placeholder consists of small indentations with specific copper line patterns that also include a pad to which an RFID IC module would be attached. The company expects to begin attaching RFID IC modules once it has finished putting the necessary reader infrastructure and supporting software in place.

Schneider Electric is producing the PCBs with particular line patterns so that each circuit board’s ground plain (consisting of a layer of copper) will function as the antenna of an EPC Gen 2 RFID tag when an IC module is mounted directly onto the PCB. The firm plans to use the Magicstrap RFID IC module, produced by Murata.

The Magicstrap technology will connect the RFID IC with the PCB’s ground plain by way of a 3-D multi-layer impedance matching circuit that provides dual bandwidth. The multi-layer matching circuit includes a chip from NXP Semiconductors, and was designed by Murata, which mounts the chip on ceramics and matches the antenna with that chip.

“A major problem with radio frequency is that you have to have a perfect match between the antenna and the chip,” says Michel Ollive, Schneider Electric’s manager of advanced manufacturing design and technologies. “The trick is adapting different types of boards to the RFID IC, since any change in the board leads to an impedance change and means you need to redesign your matching circuit.”

Schneider Electric first developed the RFID application so that it could track PCBs internally. “We want to associate production parameters with a particular product,” Ollive explains. “If the product fails to work properly, we can quickly find out which PCBs went through the same process.”

Currently, Schneider Electric tracks PCBs by means of serial numbers applied in the form of 2-D laser matrix codes and 2-D matrix stickers. The company employs a laser to etch a matrix code into each PCB during an early stage of the production process, when bar-code labeling would not be feasible due to the high temperatures involved.

A 2-D label is applied on each PCB that receives a spray coating, in order to make it resistant to humidity and acid. The label is necessary since the coatings tend to refract light, making the original etched bar code difficult to read. The product is then assembled in a plastic housing, and a second 2-D bar-code label is applied to the housing’s exterior. Finally, the completed product is packed into a cardboard box, requiring the application of a third 2-D bar-coded label onto the product’s packaging. Each step increases overall production time, Ollive says, thereby driving up costs. For now, the plan is for Schneider Electric to continue using the laser marking until the end of the laser’s life, though eventually, the company says, the tag cost will be recovered from the savings made by not having to etch an ID number onto each PCB and attach three bar-code labels.

Project partners are currently working to set up the reader and software infrastructure at Schneider Electric for a PCB production line. The line will comprise up to 20 readers and associated antennas that will read an ID number encoded to each PCB’s RFID tag, and then write data to the IC module’s memory at multiple production points.

By adding RFID tags to its PCBs, the company hopes to better control its internal PCB production processes and offer its customers a way to better manage electronics throughout their products’ life cycle, as well as a method for identifying and deterring product counterfeiting. Schneider Electric plans to share specific PCB production data with its customers, which could help them reduce their research costs if an individual circuit board must be traced.

To increase quality control and make each production step traceable, for instance, the lot numbers of components mounted on a specific PCB will be stored on a server and linked to the tag ID number encoded to that particular board’s RFID chip. “No process data will be stored on the tag due to its limited memory,” Ollive says. Instead, Schneider Electric will store the information on the server, in addition to the test results from along the production line.

At present, Murata is using NXP’s Ucode RFID chips that have 512 bits of memory. According to Alexander Schmoldt, the business development engineer of Murata’s European division, the read range of a PBC’s tag will be up to 5 meters (16.4 feet), depending on the design of the ground plain antenna.

Once production with RFID IC modules is underway, Schneider Electric plans to test the technology to assess the RFID ICs’ performance, since the environment around the tag constantly changes as the board’s design changes. “We will evaluate how the Murata technology works once mounted on PCBs of different shapes,” Ollive says. “We need to find out if read ranges are consistent.”

Schneider Electric conducted initial tests of the technology to confirm that the electromagnetic emissions of the tagged PCBs do not impact the company’s compliance with regulations, or interfere with the functioning of devices using the PCB. “We found no deviation in electromagnetic waves for tagged or untagged PCBs,” Ollive states.

One problem Schneider Electric did incur involved reading the RFID tags of PCBs stacked three or higher due to RF interference. The firm is consciously avoiding the use of high-power readers in its factory, due to potential human safety concerns from exposure to strong RF transmissions.

“As a hardware engineer, I’m confident that we don’t have any human safety concerns,” Ollive explains, “but as a precaution, we will limit to a read range of few centimeters. As a comparison, the devices emit much fewer signals than a mobile phone.”