February, 2020


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Page 89


Optimal Conformal Coating: Balancing Equipment and Process Control


Continued from page 87


to consider are the conformal coating material being used and the type of applicators to best apply it. Other process controls relate to


fan width, temperature and flow. Laser fan width control maintains coating width, independent of fluid viscosity, and provides data logging for statistical process control.


settings and reduces operator inter- vention. Process feedback is redun- dant — every process has some level of control and multiple control sys- tems are in place along the line. The system works as one unit.


The results from automated coating inspection (ACI), for example, help operators monitor the process in real time and enable them to make adjust- ments on the fly. There is more flexibil- ity in configuring the line, so inspection can be done before curing, after curing or both. By inspecting before curing, issues can be fixed in the coating process, making rework easier. Re -


work is more difficult if inspection is done after curing, but after curing, inspection catches problems that may have occurred in the curing step. Many of the solvent-based mate-


rials used in coating have high volatile organic compounds (VOCs). There is an initiative in the industry to make conformal coating a safer, more environmentally friendly pro - cess. Having one line makes it easier to address environmental needs by managing and removing the VOCs. Creating the configuration for


the coating process line with a devel- opment team lets the user develop a


program and check the process before coating begins, and having a single source for maintenance, repair and support streamlines the opera- tion and is more cost efficient. Working with a single supplier


eliminates time spent communicat- ing and coordinating between suppli- ers. Instead, efforts can be focused on overseeing the process, ensuring the equipment is installed correctly and ramping up production. It eliminates finger-pointing between upstream and downstream equipment suppli- ers. There is also technical support


Continued on page 91


Nordson ASYMTEK’s Select Coat SC-350 is designed to deliver superior edge definition and uniform coating thickness at high speeds.


Viscosity control is especially impor- tant, because the fluid must remain at a certain consistency and thick- ness for proper flow rate and applica- tion, despite viscosity fluctuations in the manufacturing environment. For example, Qadence™ flow


control, a closed-loop system that combines conformal coating hard- ware and software, automatically compensates for viscosity changes related to temperature, humidity and batch-to-batch variation, main- taining stable fluid application, flow rates and performance. Fluid deliv- ery methods, such as atomized, non- atomized and precision jetting, and whether the application needs single or multiple applicators with simulta- neous and/or toggling capabilities, should be taken into account.


Conformal Coating Line The type of curing system select-


ed should be based on factors that include desired cycle rate, tempera- ture constraints for the board or part and the curing mechanism needed. Conformal coating inspection consid- erations are the ability to verify coat- ing thickness, to inspect coated and non-coated areas within defined lim- its and around fillets, selective bubble detection, and the ability to inspect the sides of the components. Facility requirements, such as available floor space and ventilation, should also be taken into account. There are many advantages to


having a conformal coating line. First is improved quality and relia- bility. Process controls and monitor- ing occur at every process step — coating,


Quality increases, because an auto- mated line with process controls and closed-loop feedback replaces physi- cal handling of the product and vari- ations in manual inspection results, makes adjustments to coatings and


Active tip technology


Incorporates an integral sensor located deep inside of the tip for optimal performance and quick recovery times while increasing productivity and delivering consistent results.


Patented tip and grip design Fast and hassle-free tip changing without needing any tool.


One intelligent WX platform


Run any RT tip from one WX station, meeting all operational hand soldering needs such as motion sensing or traceability with digital data storage in the soldering tool and station.


Precise control, ergonomic grip


The boomerang handle design allows for precise handling while providing an ergonomic and secure grip


inspection and curing.


Learn more at: weller-tools.com/nocompromise/


See at IPC APEX, Booth 1845


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