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Process Cleaning Magazine
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PC FEATURE
After testing with two different cleaning agents, the aerospace manufacturer selected Speedline’s AS100Ci (shown here) to replace its existing spray-in-air inline machine.
Along with new, improved technology, the constantly changing landscape of environmental regulations requires manufacturers to always be on alert for ways to improve their cleaning processes. With four locations in the U.S., one subsidiary of a global commercial and military aerospace manufacturer located in Milwaukee, Wis., recently made the move to evaluate the performance of its existing cleaning operations in an effort to better ensure the quality and consistency of its products.
Established in 1959, the company has been a global leader in the design, development, manufacture and integration of state-of-the-art equipment, electronics and systems for air, space, land and sea applications. Its products can be found in more than 150,000 aircraft to date and range from integrated avionics and flight controls to navigation systems, displays and computer systems for aircraft, helicopters and missiles.
Prior to the recent study, the company had been successfully cleaning with Zestron’s fast technology based cleaning agent Atron AC 205 in a spray-in-air inline machine. The substrates cleaned are printed circuit boards that are specifically designed for high-reliability aerospace applications. As failures in these types of applications are not an option and long-term product reliability is a must, the cleanliness levels sought have been defined according to IPC-TM 650 J-STD-001D.
In order to ensure continued product quality, management decided to evaluate the performance of the inline cleaner by comparing it with Speedline’s Aqua-storm AS200 and the new AS100Ci. While evaluating the two machines in the experiments, the company used two different cleaning agents—Atron AC 205 and a competitor’s alkaline cleaning agent.
Methodology
The cleaning trials of the AS200 and AS100Ci inline cleaners were performed at Speedline’s facility in Camdenton, Mo. The test vehicles were standard double-sided test boards (printed circuit boards) populated with 1825 and 1210 components. The test boards were soldered with a leaded, mildly activated resin-based solder paste on the top and an RMA flux on the bottom side, reflowed according to customer selected profiles.
The wash temperatures as well as the belt speeds were pre-selected by the customer and the most appropriate cleaning solution concentrations were recommended by Zestron and the competing chemistry supplier accordingly for its products. The company suggested a 10% concentration for its Atron AC 205, while the competing product was used at 15% concentration. Atron AC 205 is specifically designed to remove flux residues from electronic assemblies and was developed to improve the cleaning performance and bath life of traditional surfactant-based cleaners. The cleaning agent’s mild formulation is particularly compatible with most sensitive materials, as well as solder joints, and can be used as a drop-in replacement for high and medium pressure, inline and batch cleaning systems. The competitor’s cleaning agent is an aqueous chemistry designed for cleaning the latest lead-free residues.
The same process settings (concentration, wash temperature, belt speed and pressure settings) were used during the cleaning trials in both AS200 and AS100Ci inline cleaners to ensure proper comparison. Six individual sets of tests were performed for both cleaning agents in both inline cleaners. Multiple test boards were used during each trial to ensure the repeatability of the cleaning results. Table 1 shows the test parameters.
The boards were visually inspected to evaluate the presence of flux residues on the surface as well as underneath the components. All components were removed from the board surfaces before inspection. The visual inspection was performed by two independent individuals to average the subjective cleanliness assessment. Additionally, one set of boards was also subjected to ionic contamination testing to further validate the results.
Trials with AS200 – Visual Inspection
The first set of tests was performed with boards populated with 1210 and 1825 components, which had been cleaned with both cleaning agents in the AS200 inline cleaners. All tests were conducted at various belt speeds (low, medium, high) and with two different board orientation combinations (SMT side up/flux side down and flux side up/SMT side down). Six data points were collected for both board orientations.
The visual inspections of the 1210 chip capacitors showed that the tests conducted at low belt speeds provided the most drastic differences between the two cleaning agents. The percent of flux removed was found to be 90% (SMT side up) and 50% (wave side up) for Atron AC 205 versus 75% (SMT side up) and 30% (wave side up) for the competitive cleaning agent.
For the 1825 capacitors, similar results were obtained. However, the overall cleanliness levels were higher. Atron AC 205 at low belt speeds was able to remove more than 90% of flux residues for assemblies with the SMT side facing up, whereas the competitive product achieved slightly lower levels with 75% flux removal in the same orientation. Increasing the belt speed to medium and high showed a cleanliness level of 70% on average for Atron AC 205 compared with a 58% average for the competitive cleaning agent. The results for the wave side facing up were slightly lower with an average of 68% cleanliness (across all belt speeds) compared with an average of 58% for the competitive product.
Trials in AS100Ci – Visual Inspection
The second set of tests was conducted in the AS100CI inline cleaner. Although all process settings apart from the cleaning agent concentration remained constant, the results continued to show significant differences.
When cleaned with Atron AC 205, almost 100% cleanliness for the 1210 packages was achieved at low belt speeds (SMT side up) and an average level of 40% cleanliness at medium to high belt speeds. The competitive product achieved 78% cleanliness (SMT side up) at low belt speeds and an average of 26% cleanliness for medium and high belt speeds. For the wave side facing upwards, the results showed again significant differences during this DOE study. The competitive product was able to achieve an average cleanliness of 30% across all belt speeds, whereas Atron AC 205 was able to achieve 40% for low, medium and high belt speeds.
Overall, higher cleanliness levels could be achieved for all 1825 chip capacitors, similar to the results observed for the AS200 inline cleaner. These differences may be attributable to the higher standoff height of this particular component type. At low belt speeds, Atron AC 205 accomplished 92% flux removal and 74% on average for medium and high belt speeds. The competitive product produced 78% flux removal (SMT side facing up) for low belt speeds and 64% for medium and high conveyor belt speeds. The results for the wave soldered side facing up led to 62% cleanliness for the competitive product and 69% for Atron AC 205.
Trials in AS200 and AS100Ci – Ionic Contamination
To further substantiate the above findings and compare the performance of Atron AC 205 in the new machines with the current cleaning process, the customer decided to clean one additional set of test boards in both cleaning systems. Subsequently, the boards were subjected to an ionic contamination test. As required by the customer, the internal pass-fail limit was set at 14 µg/sq.in. The ionic contamination results yielded lower values than the current process in both systems. The result was less than 1 µg/sq.in.
Implementation
The overall test results showed a significantly better performance of Atron AC 205 at 10% concentration when compared to the performance of the competing cleaning agent at 15% concentration. This represented a 30% reduction in active concentration, which would lead to substantial process savings for this aerospace manufacturer.
Based on the cleaning results and the overall product performance, the aerospace manufacturer decided to continue using Atron AC 205 in their new inline cleaner (AS100Ci). With Zestron’s help, the company has completed a smooth cleaning process implementation for further business
success.
For more information about Speedline Electrovert, call 573-346-3341 or visit speedlinetech.com.
Harald Wack, Ph.D., is the president and Umut Tosun, M.S.Ch.E., is the application technology manager at Zestron. For more information about the company, call 703-393-9880 or visit zestron.com.