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76 DESIGN007 MAGAZINE I NOVEMBER 2019 As assemblies become ever more densely populated, and housing/casing designs become more permeable to save weight, the use of con- formal coatings is becoming essential to protect the assembly from its operating environment and ensure acceptable reliability for the appli- cation intended, especially when op- erating in hostile environments. In our previous columns, we have covered some of the fundamental consider - ations of conformal coating selection and performance, ex- amined key ben- efits of different types of coatings, and explored their limitations. In this month's column, I am going to con - centrate on essential factors regarding the challenges board de- signs can pose on design- ers to help you implement a more successful coating opera- tion. Let's look at issues that may arise with coating coverage, cycle time, and coating flow. Board Design Challenges The design of the board can have a huge im- pact on a successful coating operation, both by determining which methods can actual- ly be used, as well as the degree of coverage that can be achieved within the required cycle time. I'm going to focus on selective coating, being the most common application method, where masking is minimised if not eliminated, but most of the principles will translate to oth- er coating application methods. In Lean manufacturing, the coat- ing cycle time is often the key requirement, ensuring the production takt time can be met, thus maintain - ing a balanced line. Given that coating is often one of the lat- ter processes in the production line, it is often advanta- geous for the coat- ing cycle time to be faster than the overall line takt time to ensure any accumulated produc - tion can be cleared as rapidly as possible, should any previous opera- tions suffer a stoppage. In general, the fewer areas there are on a board that must be free from coat- ing, the faster the coating cycle time will be. Should the coating cycle time be too long, then a decision can be made to either deter- mine the most vulnerable parts of the assem- bly and focus on that area in the available cy- cle time, or to split the coating across several workstations. Design Challenges and the Impact on Coating Success Sensible Design by Phil Kinner, ELECTROLUBE