CircuiTree - January 2009 - (Page 32) PCB Tracking With RFID: Speed, Efficiency, and Productivity Made Simple Chris Cook and Hank Tomarelli T racking goods through the manufacturing process was originally accomplished with pencil, paper, and human input. Barcodes introduced an automated, machine-readable tracking mechanism that streamlined all types of manufacturing. But modern PCB assemblies are running into limitations because of barcode labels. The relatively large labels have to find increasingly scarce real estate on high density boards. Additionally, flexible manufacturing processes that create dozens or hundreds of models derived from a base design must be replaced with a barcode label in the final stages of product production. Today, PCB tracking can be streamlined using radio frequency identification (RFID) technology. RFID is a proven technology and asset racking implementations in other industries have provided significant ROI. RFID not only overcomes many of the problems associated with barcodes including board real estate, automation, and human intervention, but it is reprogrammable and can be updated at any point in the manufacturing, stocking, or shipping process. And devices are now available that are among the smallest components produced. These benefits add flexibility, increase throughput, improve quality traceability, and reduce manufacturing costs. For example, should there be a problem at any point while assembling a product, RFID enables the manufacturer to isolate where the problem is and it can identify those units that may have been affected. It can be likened to finding a needle in a January 2009 • circuitree.com Figure 1 Surface Mount Technology Device With Slot Antenna haystack, without disassembling the entire haystack. The benefits can extend beyond manufacturing to the entire lifecycle. In fact, service, warranty, and recall costs could all be reduced with RFID-enabled circuitry. Limitations of Barcodes Barcodes have served electronics manufacturers well since the 1980s, but they have limitations and, in many cases, no longer meet the needs for tracking and managing manufactured goods. Perhaps more relevant is that technology, such as RFID, has evolved in parallel with business trends and requirements. Some barcode proponents argue that standard linear barcode labels and scanners are simple and inexpensive. Unfortunately, their information density is low and it takes over 500 mm2 to get a dozen or so characters on a label. Therefore, placement flexibility is very low, and virtually every manufacturer has its own standard barcode labels with no ability to change it for fear of missing reads or slowing down the production line. The two-dimensional barcodes, or data matrices, that allow hundreds of bits of information to be placed in tens of square millimeters make an attempt to solve the density problem. However, it comes with a tradeoff for the high scanner cost, read reliability, and reduced flexibility. Typically, expensive, high-resolution cameras that require precise registration are needed to read a data matrix label. The high precision requires the assembly line cameras to be repositioned every time a new label position is processed and the background environment can change the accuracy of the reads. Read rates of 80 to 90 percent are typical for data matrix labels on high-speed manufacturing lines. Both types of barcodes require line of sight between the label and reader. This adds more restrictions on PCB component placement and many times the design and placement of large heat sinks or mounting brackets are affected by barcode restrictions. Another disadvantage of line of sight is that labels are unreadable once the PCB is in the final enclosure. 32 http://www.circuitree.com
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