Circuits Assembly - April 2008 - (Page 31)

Benchtop Cleaning Another option is not to clean with a brush, as described by Munson, but to rinse the board with an aerosol flush. This is a very good option and delivers fast and reliable cleaning, especially using today’s fast-drying, ozone-safe solvents. The problem is that techs will run through a lot of cans in fairly short order. It’s a sloppy, wasteful and often expensive process, but it will deliver clean boards, if the customer can afford it. The best option is to use some form of dispensing system on an aerosol solvent to control the flow of the cleaning fluid. In this process, the brush’s mechanical scrubbing action is complemented by a controlled spray from an aerosol container. It forces the technician to implement “wet, scrub, rinse and dry” every time. It also allows the technician to clean better, more consistently and thoroughly, with far less solvent. Because the solvent is fresh and pure (“virgin” is the term in the cleaning industry), it will deliver far better cleaning than some tired, contaminated alcohol sitting in a dirty pump bottle. In one study conducted by a major New England OEM, a benchtop aerosol cleaning system produced SIR results of 12.5E-9 to 13.5E-9 across four different solvents. So we see it’s not the solvent that matters; it’s how you use it. The conclusion of that customer was that manual PCB cleaning can be quick, affordable and reliable at the benchtop, provided the technician is equipped with the proper cleaning tools that permit rinsing the board without waste. Munson did us a favor by highlighting the problems with dip-and-brush cleaning, which has been the conventional circuit cleaning process since the dawn of the space age. What must be emphasized, though, is the crucial factoid: If you can’t rinse, you can’t clean. Engineers should review their benchtop cleaning processes to make sure they are using all four steps. If not, call some cleaning experts and see how they can boost your quality and save you money at the same time. ■ References 1. T. Munson, “The Big Brush Off,” Circuits Assembly, December 2007. Mike Jones is vice president of sales and marketing at MicroCare Corp. (microcare.com); mikejones@microcare.com. Coating Performance Under Your Control The NEW SelectCoat SL-940E Series from Asymtek ® The Most Accurate Conformal Coating System Available • • • • • • Traceability Closed-loop process controls Vision system Advanced integrated electronic controls and software Proprietary jetting and coating technology Excellent edge definition Increased Productivity with 30-50% Faster Throughput • 1,000 mm/sec. coating speed and 1g peak acceleration Lower Cost-of-Ownership Supported by International, Award-Winning Service Network HEADQUARTERS 2762 Loker Avenue West Carlsbad, CA 92010-6603 USA U.S. Toll Free: 1-800-ASYMTEK Tel: (760) 431-1919 Fax: (760) 431-2678 Email: info@asymtek.com INTERNATIONAL SALES Europe: +31 (0) 43-352-4466 China, Guangzhou: +8620-8554-9996 China, Shanghai: +8621-5854-2345 Japan: +81 (0) 3-5762-2801 Korea: +82-31-765-8337 S.E. Asia: +65 6796-9514 Taiwan: +886-229-02-1860 www.asymtek.com/products/sl_940 Recipient of Intel Corporation’s SCQI Award: 2003-2006. Visit Asymtek at APEX booth #511 and at NEPCON China circuitsassembly.com Circuits Assembly APRIL 2008 31 http://microcare.com http://www.asymtek.com/products/sl_940 http://circuitsassembly.com

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Circuits Assembly - April 2008 Contents Caveat Lector Industry News Market Watch Talking Heads Screen Printing Better Manufacturing Design and Modeling of High-Speed, High-Density 3-D CSPs and Memory Modules The ‘Big Brush Off’ Revisited Impact of Soldering Atmosphere on Solder Joint Formation Beyond Moore’s Law ESD Control For Class 0 ESDS Devices Growing Your Brand This Year’s Model Tech Tips Reflow Soldering Process Doctor Pb-Free Lessons Learned Getting Lean Equipment Advances Apex Product Preview Ad Index Assembly Insider Technical Abstracts

Circuits Assembly - April 2008

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