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98 PCB007 MAGAZINE I FEBRUARY 2021 Feature by Bob MacRae EASTERN REGIONAL SALES MANAGER, TAIYO AMERICA, INC. Everyone wants a smooth-running solder mask process with high productivity and mini- mal rejects, but to achieve this you really need a firm understanding of what your current pro- cess is capable of, what its limitations are, and what you want to improve. Process capability benchmarking is a great way to identify and im- plement improvements within your process. ere are six primary process steps involved with a typical LPI solder mask process: • Surface prep • Solder mask coat • Tack dry • Exposure • Development • Cure But, within each of these segments of the process, there are a vast number of sub-process steps and variables that will influence your suc- cess; their impact on the entire process needs to be completely understood before the pro- cess can be fully optimized. For example, if you increase the tack dry temperature, exam- ine how it will impact exposure, hole clearing, and sidewall definition. Others include variables such as the type of surface you are applying the solder mask to (Cu vs. Au), panel design, circuit trace height, mixed solder mask pot life, solder mask coat- ing application method, the associated coat- ing parameters, the type of equipment used to expose the solder mask, and the exposing parameters used. Even the type and color of solder mask (and many, many more) can have a major impact on each individual process, as well as the overall solder mask end results. ere are also many external process steps be- fore and aer solder mask, such as copper pat- tern plating, resist strip, solder strip, and final finish; these can all impact the capabilities of your solder mask process. A thorough under- standing on how each variable impacts your Benchmarking With Your Suppliers: What to Know About Solder Mask

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