Circuits Assembly - March 2008 - (Page 24)

Screen Printing Printing Verification and Traceability Tools Used together, each product can be traceable to the board level. s much as we would like to believe a clear set of instructions ensures an error-free result, most of us are also realists and understand mistakes happen. It’s inevitable. And, while goofs are OK sometimes, in manufacturing environments where improper setup can result in low yield (read: lost revenue) or, worse, put someone’s safety at risk, input control is essential. This is especially true for the front-of-the-line printing process where errors during setup can proliferate down the line. Through the use of modern verification and traceability tools, many unnecessary mistakes can be eliminated and human error can become less of a concern. Without question, verification technology has been driven by the automotive industry, where safety is paramount. Other markets, though, such as biomedical and, to some degree, EMS, are also beginning to use verification tools within their processes. Verifying consumables and settings loaded by operators are consistent with those parameters specified in the product file delivers a level of process control not feasible with manual crosschecks. With automatic setup verification, screen-printing setup variables are compared to corresponding values specified in the product file. An operator scans each process input (see list) to confirm parameters and consumable identities before production commences. Management can decide what action to take if an improper input is selected; a simple warning can be generated or the machine can be halted completely, preventing the start of production. Another alternative is to simply record the data in the standard format of your choice so that analysis can occur offline. Process inputs for verification include: • Screen or stencil identity. • Paste identity. • Enclosed head or squeegee identity. • Solvent identity. • Understencil cleaning cassette identity (when applicable). • System temperature. • System humidity. • Operator identity. • Batch identity. • Line identity. With most current verification systems, a barcode procedure (generally with either 1-D or 2-D barcode standards supported) is used where each item is coded and then scanned before use. For EMS firms, this technology is quickly becoming an analysis tool to better understand process inputs and the resulting outputs so that operations can A Clive Ashmore is global applied process engineering manager at DEK (dek.com); cashmore@dek.com. His column appears bimonthly. be optimized. As we know, pennies per board can mean the difference between winning or losing an order, so employing verification systems not only delivers foolproof process control but also offers cost analysis benefits. Biomedical companies are also migrating toward this technology and, in fact, are helping us forge new ground beyond traditional barcode systems. To that end, our company has been investigating the use of RFID tags as a method of input verification. In the case of biomedical production for certain products, high-precision screens are used and because a screen’s lifespan is limited with screen degradation adversely affecting product yield, manufacturers have set a limit on the number of times each screen can be used. Though current technology permits artwork-specific screen identification to occur on each machine, it doesn’t prevent artwork-identical screens from being used on different printers. To the machine, the screens are the same. So, if an operator were to inadvertently move a screen with 100 prints left in its lifecycle from one machine into a printer that was beginning a production run, current technology wouldn’t be able to identify the number of prints expired and the number of prints that remain. For many biomedical firms, that’s just not acceptable: They want a unique way to identify the number of prints left on each screen. We think an RFID system can deliver just that. Similar to inventory management, the RFID will register each print excursion and notify the operator of the number of prints remaining for that particular screen. When verification is used in tandem with traceability software, each product is traceable to the board level. For certain industry sectors – namely automotive – traceability data are required, and compliance with well-known standards, such as ISO/TS 16949 or QS9000 that trace product to the component level, is mandatory. Many advanced printers offer fairly sophisticated traceability data capabilities, enabling individual board identity scanning upon machine entry. Each board’s identity is recorded with the applicable setup verification data and is time- and datestamped. In the event of a field failure, the manufacturer can go back through the entire supply chain, identify the problematic batch and, ultimately, locate the source of the problem, which might range from improper paste blending to an error in the stencil used. Clearly, this is most often used for products with safety liability and not mainstream consumer electronics, but we are starting to see adoption outside traditional automotive and medical sectors. Sure, mistakes are going to happen. But with today’s verification and traceability technologies, errors can be significantly reduced and profits improved. ■ circuitsassembly.com 24 Circuits Assembly MARCH 2008 http://www.dek.com http://circuitsassembly.com

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Circuits Assembly - March 2008 Caveat Lector Letters Industry News Market Watch Talking Heads Focus on Business On the Forefront Screen Printing What Drives the Crowd? Mastering ESD Control in Automated Handling Systems Beating the RoHS Heat Trade Secrets True to Its Roots The Road Abroad - Strategic Alliance or Greenfield Facility? Tech Tips Wave Soldering Test and Inspection Process Doctor Pb-Free Lessons Learned Getting Lean Materials World Equipment Advances Apex Product Preview Ad Index Assembly Insider Technical Abstracts

Circuits Assembly - March 2008

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