The company based this choice on the product's cleaning performance and the ability to meet company environmental guidelines. "We required an aggressive cleaner to remove residual silicone from the equipment, yet one that was also environmentally friendly," says Mark Henger, coating process engineer.

The automated dispensing equipment at the Elma facility is computer-controlled and programmable to coat specific areas of the PCBs. Components include two spray valves, a dispensing valve, dispensing needle and seat, and an air cap. Every component that comes in contact with the conformal coating is cleaned with OS-120 fluid.

The dispensing valves, which have interior threads, are immersed in the fluid and thoroughly flushed. The fluid breaks down the silicone, softening it for easy removal. On other equipment components, the excess conformal coating is removed by hand-wiping with the OS-120 fluid. The facility also uses the fluid to clean PCB samples and the wet thickness gauge, which is used to verify coating coverage.

When a production run is arranged for a particular PCB, a sample with no components is sent through to ensure the spray pattern is compliant. After the coating has been applied to the test board, the wet thickness gauge measures the depth of the silicone material to confirm the correct amount is being dispensed.

For more information on OS-120 cleaning fluid, call Dow Corning Corp. at 800-346-9883, visit www.dowcorning.com or Reply 5.