More powerful readers combined with transponders that can withstand reflow soldering have resulted in RFID gaining increasing inroads into work-in-process monitoring in electronics manufacturing.
Apart from the traditional areas of RFID deployment, such as security and attendance management, RFID has also gained inroads into work-in-process monitoring.
One such application is the tracking of printed circuit boards (PCBs). This application was, until recently, dominated by barcode and optical character recognition (OCR). The article describes some of the advantages of and requirements for tracking PCBs using RFID and how recent product offerings can make the implementation of PCB tracking throughout the complete production process economical and practical.
Electronics manufacturers want to be able to automatically identify individual PCBs in the production process. Being able to do so is valuable for a range of different tasks; such as configuration management, i.e., the ability to manage several product variants and revisions in the same production process. It is also valuable for production testing and calibration.
The introduction of RFID for this purpose has taken some time. Even today, much of the tracking of PCBs in production is still done via barcodes or, in some cases, OCR. During the 1990s and most of the 2000s the lack of world standards, the cost and complexity of reading devices, the lack of robust performance, and the size and cost of practical transponders for use with PCBs prevented RFID from gaining substantial entry on the manufacturing floor.
However, since the introduction of the ISO 18000-6c standard, a range of new niche applications have emerged, which were not technically or economically viable previously. With RFID readers replacing barcode and OCR scanners and RFID transponders replacing printed labels, at least three major advantages are gained:
- The flexibility in setting up the reading mechanism in the production process is far greater due to less orientation sensitivity and better range. In barcode and OCR, the reader must be aligned and in line-of-sight to the label. Orientation of the label in relation to the scanner is also important. With the ISO 18000-6c standard, the manufacturer has more freedom for placing a transponder. The range has increased from a few inches to several feet. The placement of the transponder can be integrated in the design. Moreover, earlier generations of RFID readers were rather bulky, often requiring installation of separate antennas and additional installation of the antenna cables. The availability of small form factor readers with integrated antennas and networking via WLAN or Bluetooth increases the feasibility and lowers the cost of implementing and maintaining RFID.
- The RFID transponder’s memory can hold more data than a barcode. It also allows for multiple writing. This means information about the product history can be stored, including calibration and test information. Throughout the life-cycle of the product, maintenance data can be added and its maintenance history be retrieved. The availability of a 64-bit unique identifier (UID) along with the ability to secure stored data means a higher security level and the ability to use these features for protective measures against counterfeiting. In addition, the availability of a UID has an environmental and economical perspective. In the 2000s, increasing environmental awareness, increasing cost of materials and regulatory requirements demanded higher recyclability of electronic parts. These requirements dealt with everything from production, distribution, consumption to the disposal of the product; causing the manufacturing industry to manage product life-cycles more precisely.
- Traditional labels cannot be used with electronic equipment manufactured using the reflow process since such labels will not survive the heat and chemical conditions therein. This includes barcodes and labels based on discrete RFID transponders. The introduction of RFID transponders designed for surface mounting technology (SMT) has overcome this problem. These chips can be mounted to the naked PCB from the outset, surviving the reflow process, and thenceforth follow the PCB throughout the complete production line. The chip continues to be useful after production and during the lifetime of the product. Contrary to the inlaid ISO 18000-6c transponders used in retail, supply-chain and document management, the SMT RFID transponder is encapsulated in such a way that it can be handled just like any other SMT component.
Figure 1: An example of a reflow process compliant RFID transponder.
Reading devices for flexible placements
Free2move’s FS901 Gemia™ (Figure 2) is an example of a small sized, cost-effective, RFID reader with sufficient range and wireless interface to allow for flexible placements. Gemia offers good reading performance in a very small form-factor, making it possible to integrate it with various machines and robots along the production line. With a weight of only 200 grams, the Gemia has a built-in antenna with circular polarization characteristics. A range of accessories make it possible to adjust its position according to where the transponder is located. If power is an issue it has battery for up to 24 hours of continuous operation. The Gemia can be interfaced via serial communication via Bluetooth, WLAN, or USB.
Figure 2: Free2move's FS901 Gemia RFID reader.
Another Free2move product, the F2M01SXA Uncord™ (Figure 3) is an extended range RS232 Bluetooth adaptor, providing additional placement flexibility in establishing robust wireless communication to the host system. The Uncord has a complete built-in Bluetooth serial port communication stack and supports the RS232 physical interface. Just like the Gemia, Uncord is powered via mini-USB. Uncord and Gemia offer up to 60 meters (200 feet) range in a typical factory environment.
Figure 3: Free2move's F2M01SXA Uncord extended range RS232 Bluetooth adapter.
There are typically three classes of information that the Gemia will access:
- The transponder’s unique identifier (UID), which is a 32-bit unique identifier provided by the manufacturer of the transponder. The UID is usually stored together with manufacturer and product codes, forming a 64-bit transponder identifier (TID). This identifier cannot be changed but often serves as a secure identifier to make counterfeiting impossible.
- The electronic product code memory (EPC) is typically 96 bits, but other code lengths are common in industry-specific applications. For example, the aerospace industry is using a 128-bit EPC. The EPC memory can be used by the manufacturer to store its own identifier and the serial number of the product. The EPC memory can be protected from erasure or editing once the manufacturer’s identifiers and product serial numbers have been stored. The EPC memory can be used for fast identification.
- The user memory is typically 240 or 512 bits and can be formatted according to the manufacturer’s requirements.
The Gemia offers a range of macro commands, which makes it easy for production applications to read and store information in individual RFID transponders without exposing them to the complexity of the specific tag encodings. The macro commands can be used to easily access industry and manufacturer-specific codes. For example, if a certain calibration record is stored at 14 bits of space in the user memory, the macro command can access it as a single instruction from the application.