Circuits Assembly - March 2008 - (Page 66)

Process Doctor Inline Vs. Batch Cleaning Low volumes support batches; high volumes favor inline. rocesses in the precision cleaning industries are driven by customer requirements and economical efficiency. Published studies have concluded that overall process cost, with all its individual contributors, is essential in calculating the latter. Batch Process Standard Inline Process Cleanliness requirements, on the other Optimized Inline Process hand, depend largely on the cleaning agent technology and equipment employed. And it is here where industry opinions differ, especially when Board amount (Day) one is deciding whether to purchase Figure 1. Inline versus batch cleaning cost analysis. conveyorized inline or batch cleaning equipment. OEMs will showcase bentechnologies include fully biodegradable products that efits and disadvantages of both process technologies minimize the environmental effect. Studies also sugin an attempt to provide a sound platform to facilitate gest the organic content found from chemical isolation decision-making. (It is worth mentioning that during effluents is significantly below 1% by volume. the past few years, significant improvements have been Pb-free solder’s emergence brought about an intermade to both technologies.) esting trend that affects inline cleaning. In the past, the To effectively analyze and compare different cleanuse of OA fluxes coincided with the use of DI water to ing processes, the user has to take into account all the clean. Such machines rely on cascading DI water syselements of pure cost associated with cleaning and tems and do not run effectively with a cleaning agent, rinsing agents, including associated costs for disposal, because of the lack of a chemical isolation section. The electricity, compatibility, labor and equipment mainteincrease in soldering temperatures due to Pb-free opernance. Earlier studies suggest costs per cleaned board ations now makes the removal of OA flux significantly range from $0.20 to more than $1, depending on the harder. Because of equipment limitations, chemical situation (Figure 1). The determinant, then, will be the assistance is not possible, resulting in additional capital number of boards used. In other words, the variable expenditures. As a result, a chemical isolation section as cost aspects for inline processes vary as the number of a simple fallback should be considered (thus providing cleaned assemblies increases. Fixed costs will remain long-term cost savings). steady. Last, the user should consider future production With respect to other mechanical considerations, requirements. A smaller machine might be sufficient at the authors have established that with all professional present, but not so much if production requirements process installations currently available, residues can were to increase. be cleaned successfully, even under most demanding Conveyorized equipment can give specific attention standoff heights or geometries. The same holds true to to each and every board that enters the process. This batch cleaning operations, as their average cycle times minimizes process risks, as changes can be implementare three to five times longer than that of inline cleaned per board, and also leads to a high degree of process ing. Despite historically lower pressure settings, the control. Recent research on nozzle technologies shows prolonged cycle times are ample compensation. promising results, further permitting individualization. Spray pressure innovations have further helped Clearly, a fully automated process is designed for high batch systems compete with conveyorized machines. throughput operations, and it is here where such cleanSuch advancements, for instance, address operating ing equipment will be most economical overall. pressures and mechanisms to minimize spray shadowOne oft-cited limitation is the larger footprint. ing; the latter an often-cited customer concern. Some recent advances in cleaning nozzle efficiency Naturally, batch cleaners require somewhat more have provided shorter, more compact inline machines. laborious interaction, and typically process boards as Another concern is the rinse and wastewater generaa group, not individually. Throughput is beginning tion. Bigger machines generate up to 2 gpm or more to be addressed, but at the cost of a larger footprint. of wastewater. Depending on local requirements, effluent flow must be addressed. Recent cleaning agent $.90 $0.80 Cleaning Cost per board ($) P $1.00 $0.70 $0.60 $0.50 $0.40 $0.30 $0.20 $0.10 $0.0 0 100 200 300 400 500 600 700 800 90 0 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 Ravi Parthasarathy is a senior process engineer at Zestron America (zestron.com); r.parthasarathy@ zestron.com. Continued on pg. 65 66 Circuits Assembly MARCH 2008 circuitsassembly.com http://zestron.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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