Conformal coating line from Nordson Asymtek has optimal efficiency

Camille Sybert, Product Marketing Engineer, Nordson Asymtek

In the automotive and mobile electronics industries, meeting the standards and requirements for high reliability has become critical. With an increased emphasis on Industry 4.0 and automation, there is a pressing need to address the entire conformal coating process as one system. Not only must the system be able to apply conformal coating, but it also must support overall process tracking and traceability. Everything that goes into the assembly of these electronic systems must be recorded and monitored so the process can be researched retrospectively and the specific source of the problem can be identified if an issue arises.

Process as a whole

When talking about conformal coating, the tendency is to focus on the conformal coating machine, but conformal coating is an entire process in itself. This includes maintaining the coating quality, choosing the correct curing process for that coating, and inspecting the coating so that it is applied correctly before the printed circuit board or device heads to the next part of the assembly process. Increasingly, manufacturers are moving to full conformal coating line solutions that combine coating, curing, and inspection capabilities with closed-loop process controls and traceability to meet demand and deliver consistent product reliability.

Closed-loop controls, or the move to more automated operator-less factories, are based on requirements for equipment to be more independent and self-monitoring. Corrections and adjustments are made internal to the machine or system without operator intervention. With automated coating inspection, a lot of operator subjectivity can be removed by setting pass/fail criteria around what is being inspected. There is verification that the coating material is placed where intended and not placed where it’s not intended, and that the final product is within the accepted tolerance. The same is true with ovens and other systems having closed-loop controls to make sure that temperature is being appropriately regulated to avoid an incomplete cure that may potentially cause other concerns and considerations. The benefit of a complete line is that not only can these pieces of equipment collect data and gather information, but that they‘re able to share this data and information with other equipment in the line, so the system can take action on that information.

Choosing the optimal conformal coating line configuration is determined by the type of board and application, the desired cycle rate, and the coating material. The quality of the process is influenced by the edge definition, coating thickness, and adhesion of the material to the substrate. Eliminating coating problems starts with a high-quality conformal coating system. Some requirements to consider are the materials being used and the type of applicators to best apply them.

Closed-loop system

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. Viscosity control is especially important because the fluid must remain at a constant consistency and thickness for proper flow rate and application, despite viscosity fluctuations due to the manufacturing environment. For example, Qadence flow control, a closed-loop system that combines conformal coating hardware and software, automatically compensates for viscosity changes related to temperature, humidity, and batch-to-batch variation, maintaining stable fluid application, flow rates, and performance. Fluid delivery methods, such as atomized, non-atomized, and precision jetting and whether the application needs single or multiple applicators with simultaneous and/or toggling capabilities, should be taken into account.

The type of curing system selected should be based on factors such as desired cycle rate, temperature constraints for the board or part, and the curing mechanism needed. Conformal coating inspection considerations are the ability to verify coating thickness, to inspect coated and non-coated areas within defined limits 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 considered.

There are many advantages to having a conformal coating line. First and foremost is improved quality and reliability. Process controls and monitoring occur at every process step – coating, coating inspection, and curing. Quality increases because an automated line with process controls and closed-loop feedback replaces physically handling the product and variations in manual inspection results, makes adjustments to coatings and settings, and reduces operator intervention. Process feedback is redundant — every process has some level of control and multiple control systems are in place along the line.

Coating inspection

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 on-the-fly adjustments. There is more flexibility in configuring the line, so inspection can be done before cure, after cure, or both. By inspecting before cure, issues can be fixed in the coating process, making rework easier. Rework is more difficult if inspection is done after curing, but after cure inspection catches problems that may have occurred in the curing step.

Many of the solvent-based materials 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 process. 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 development team lets you develop a program and check the process before coating begins. Having a single source for maintenance, repair, and support also streamlines the operation and is more cost efficient. Working with a single supplier eliminates time spent communicating and coordinating between suppliers. Instead, efforts can be focused on overseeing the process, ensuring the equipment is installed to your requirements, and ramping up production. It eliminates finger-pointing between upstream and downstream equipment suppliers and there is technical support across the entire line when and where it’s needed.

Automated coating line

With the many advantages and industry emphasis on conformal coating as a process, and as a logical extension of its existing conformal coating systems and lines, Nordson Asymtek introduced the Panorama S-Line, the first fully automated conformal coating line. A flexible, modular system, it enables you to select the equipment and layout you need today and scale the system as demand increases. It also provides a turn-key coating solution with a single supplier with global support for the entire process. The line delivers conformal coating process control in a compact footprint, with overlapping line processes, such as heated return or flash-off in the lower compartment of each piece of equipment, minimizing manufacturing floor space use up to 50 %. The closed-loop systems within the line stabilize and track the process, eliminate variations, validate coating results, and capture up-to-the-minute process data with FIS/MES integration.

Panorama S-Line includes a Select Coat SL-940 conformal coating system with an exhaust conveyor or IR-9 module in the lower deck area. EasyCoat 6 software enables intuitive, visual programming as well as off-line programming capabilities. Included in the line is an FX-940UV ACI module to confirm in real time that the conformal coating is being properly applied. It, too, is fully integrated with the FIS/MES data capture system.

The Select Cure IR-9 module performs both top and bottom material curing and can handle mid- to high-volume production environments. It is the final step in conformal coating automation and ensures that the applied coating doesn’t migrate, remains unblemished, and that damage wasn’t introduced through handling. Failures such as shrinkage, solvent entrapment, orange peel, and bubbles can occur if the coating material isn’t appropriately cured. Curing, however, takes time and can impact operator safety. The Panorama line addresses these concerns by introducing ovens that “dry” boards, safely vent VOCs, block UV light, and support high production throughput. Having a flash-off capability in each module eliminates bubbles by allowing time for excess solvent to evaporate before a coated board enters the curing oven. Ventilation for flash-off can be incorporated within the line, distancing operators from fumes and fluids. 

To optimize the Panorama line, modules for loading/unloading, board flipping, and lifting are available. Using a line loader/unloader module, operators can feed new PCBs into the process line and unload finished products simultaneously. The module is available in different lengths and can be equipped with an operator touchscreen and an exhaust or IR-9 module in the lower deck. The boards are loaded in the middle of the coating line, giving a single operator the ability to load and unload production products from one location. The flip module flips boards automatically to allow both sides of a board to be coated without operator intervention, reducing board-handling requirements and increasing yield. The boards are then transported efficiently between the upper and lower decks in the line using the lift module. This modular system can be configured for each specific application and location.

Summary

A fully automated, configurable, conformal coating line solution offers a synergistic approach to stabilizing coating variations. It provides control and ensures an efficient and accurate process from beginning to end. It streamlines the coating process, is cost efficient, and increases throughput and yield. Incorporating coating, curing, and inspection in one conformal coating line provides the right balance of equipment and process control for optimal conformal coating efficiency. Panorama fulfills the speed, throughput, and stringent quality demands of today’s electronics applications and Industry 4.0 requirements.

productronica, Booth A2-345

www.nordsonasymtek.com