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72 SMT007 MAGAZINE I AUGUST 2019 lized to determine if the composition of the foggy material on the steel coupon was identi- cal to the clear coating on the other coupons. Luckily, there was no difference between the chemical composition of the hand-sprayed clear steel and fiberglass coupons (Samples 2 and 3) compared to the auto-sprayed foggy coupon (Sample 4) [3] . The slight fogginess that was observed was determined to be caused by the fiberglass coupons being an ivory color while the steel coupons were reflective, which caused the slight fog to be visible when the conformal coating was thicker. Meanwhile, Sample 5 appeared clear because the coat was much thinner at the end of the pot life due to the thickening of the material causing a reduc- tion in material flow rate, which resulted in the fogginess being minimized. What was most interesting was that the FTIR analysis showed there was a difference between the clear end of pot life auto-sprayed coupon (Sample 5) and the rest of the coupons that were sprayed within the pot life limit [3] . This result from the FTIR analysis showed the importance of the pot life as a critical parameter that will require process control for the final automated-spray- ing process. To allow for circuit cards to be processed through the machine, it was necessary to design fixtures that would be able to run on machine conveyor rails. The fixtures that were created allow multiple circuit card assemblies to be processed at the same time. Per the cus- tomer drawing requirements, certain areas of the circuit card assembly are required to be free of conformal coating. To meet the drawing requirements for these keep-out zones, a hand- masking process is currently used where oper- ators manually apply tape, covers, or other masking material to the CCA in the areas that must be free of coating. When designing these fixtures, an easy way to reduce manual mask- ing time and increase throughput capabili- ties was to incorporate as much of the mask- ing requirements as possible into the fixture design. The fixture is a clamshell type of design that covers certain areas as required per the cus- tomer drawing. The operator can easily place circuit cards into the fixture and secure a lid on top, and the fixture masks the majority of the required areas. By designing the masking into the fixtures, the operator time required for applying and removing masking was reduced by about half. Utilizing the fixtures that incor- porate masking has been a significant improve- ment on the current masking process and reduced significant touch time to help increase production throughput capabilities at these critical conformal coating operations. Analyzing the Current Process Evaluating the current hand-spraying pro- cess to assess the material behavior was nec- essary to ensure a sufficient understanding of the material before selecting a machine. The material was being applied with high atom- izing air pressure with a handheld air gun. The dexterity of the operator was essential for proper component coverage with the operator being able to maneuver around the circuit card assemblies to spray the sides of leads and com- ponents as necessary. This process was yield- ing very good results despite batch-to-batch and operator-to-operator variation. During the evaluation of the current hand- spray process, the material began to thicken after approximately three-quarters of the data- sheet recommended pot life and was typically being disposed of by the operator at that time. Understanding these important key facts about the current process was essential to determin- ing what machine requirements would be nec- essary. The short pot life makes it difficult to automate the process, especially since most To allow for circuit cards to be processed through the machine, it was necessary to design fixtures that would be able to run on machine conveyor rails.