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Quick, precise and completely reliable – Rehm is developing a new curtain nozzle for highly selective conformal coating

Circuit board coating is not just about complete reliability. Precise application procedures are required to cope with the constant miniaturisation in the electronics industry and the associated narrower tolerances between the areas to be lacquered and the areas which must remain free of lacquer. Electronics manufacturers are increasingly confronted with an ever-growing range of product and material mixes. To this end, flexible systems are necessary which can achieve a high throughput without setup changes. To specifically address these requirements, Rehm Thermal Systems has improved the well-established coating methodology and has developed the new VarioFlex curtain nozzle for highly selective conformal coating processes with the Protecto system.

The manufacturer of thermal system solutions for the electronics and solar industry has already considered the topic of conformal coating in 2013. With Protecto, Rehm has successfully established a versatile system for highly selective coating and dispensing processes in the market. The application procedure consisting of dispensing, spraying, jetting and curtain casting can be realised with the ‘on-the-fly’ system without difficulty, so that almost every component receives optimal protection with the appropriate lacquer.

The new VarioFlex curtain nozzle from Rehm for lacquering large surfaces in a quick and precise manner (Photos: Rehm Thermal Systems).

Ideal for high-speed and precision applications

How does the process change when the throughput is particularly high or a very slow cycle time is required? For curtain coating, Rehm has developed its own applicator, the VarioFlex curtain nozzle, which is specially designed to meet the requirements of high-speed and precision applications. Thanks to the slim extension arm with a diameter of only 12 mm and a length of 60 mm, densely populated assemblies can also be processed without difficulty. The ‘lacquer curtain’ is applied as a closed film – without spray mist and with a very precise edge sharpness. Thanks to the integrated turning unit, the lacquer curtain is automatically turned by 90° at the lacquer program’s request. An internal sensor query supports the applicator’s exact angular positioning (0° and 90°) so that typical process speeds of 300 – 800 mm/s can be achieved.

Easy to maintain thanks to a clever cleaning system

The VarioFlex curtain nozzle is extremely easy to maintain. The applicator is furnished with a special PTFE coating for this purpose. As a result, the adherence of lacquers to the applicator surface is significantly worse which means that they can be removed more easily. The applicator’s elaborate design also contributes to this ease of maintenance. Thanks to the self-centring nozzle receptacle, the nozzle can be dismantled and then reassembled again in exactly the same way without complicated readjustment. A special solvent bath with integrated brushes and fill level monitoring is available for the optimal process run. This can be initiated periodically during the process or automatically during an interruption in production. Semi-automatic cleaning during material exchange is possible within only a few minutes. All technical control elements, including the cleaning equipment, are integrated into the system in a compact manner and are easily accessible for maintenance activities.

Intuitive operation and easy software programming

In addition to its excellent mechanical properties, the system also impresses with numerous advantages for the operator. Thus, the curtain width can be easily programmed using an automatic pressure regulator and a high-precision sensor. Up to five different parameter sets with beam widths of three to 20 millimetres can be retrieved during the application of an assembly without having to initiate the measuring unit again. Due to the possibility of offline programming, the operator can also create the coating program far away from the system at an external workstation and then upload the coating program to the machine as needed.

Protecto and RDS dryer using the line concept (Photos: Rehm Thermal Systems).

If you would like to become more familiar with the new VarioFlex curtain nozzle or are interested in the protective coating of sensitive electronics, you can look at the extensive application possibilities of Protecto at the Rehm Technology Centre in Blaubeuren near Ulm and experience the various coating processes for yourself on site with professional advice. You are welcome to make an appointment with us at applikation@rehm-group.com.

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