UV Curable Conformal Coatings: THIN IS IN!

Posted by Dan Griffin on Jul 12, 2023 2:29:52 PM
Dan Griffin
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HumiSeal development specialists have been designing high-performance, UV-curable conformal coatings for approximately three decades. Compared to legacy solvent-borne and silicone technologies, UV- curable coatings provide some unique properties that can be of great value such as- 

  • Nearly instantaneous, consistent curing 
  • Superb moisture and environmental protection
  • Little or no VOC content

These coatings also lend themselves well to high-speed and high-volume applications due to manufacturing advantages such as- 

  • Minimal WIP due to immediate cure capability 
  • Low material cost due to 100% solids chemistry
  • Smaller manufacturing footprint due to much smaller curing equipment

A Customer and Market Need Has Been Identified 

As a market leader, HumiSeal continues to canvass customers as well as the PCB market in general to anticipate and address problems or needs for improvements. This regular process of collaboration has highlighted a desire for specific evolution in a property which is- 

1. Lower Viscosity 

Screen Shot 2023-07-11 at 11.49.37 AM

UV-curable conformal coatings, as noted above, have many advantages over traditional coatings, especially in high-speed and volume applications. However, mainly due to their 100% solids composition and lack of solvent thinners, the viscosity of these coatings can tend to be higher than their counterparts. 

So why does this higher viscosity matter? The answer is, in part, that in most cases it really does not create any problems. Modern selective coating equipment which is most often used for these materials is more than capable of producing excellent spray patterns and coating performance with viscosities between about 300 and 800 CPS.  

Related blog: Complete Guide to Viscosity: Part 1 and Part 2


2. "Film Coating"

The exception to this, in some cases, is encountered when high-speed film coating is the desired application method.  

Film Conformal Coating -non-atomized-1 Atomized Conformal Coating
Image: “Film” Coater (Non-Atomized)

Image: Atomized Coater 

Film coating is a method of conformal coating where the coating is extruded through a valve without the additional application of pressurized air assist. This results in a flow of coating that emerges in a fan pattern similar in appearance to a waterfall in appearance. In atomized spray, for comparison, this same flow of coating is broken into microscopic droplets similar to what you would expect in appearance to that of an aerosol can approach. 

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Why Does Film Coating Require Lower Viscosity? 

Overlap ridges

Film coating, sometimes called curtain or fan coating, can at times be the preferred approach to conformal coating when high speeds and precise edge or border control are critical. As can be imagined, atomized spray can in certain instances be inferior due to the difficulty in completely controlling with accuracy where each and every droplet may land. 

On the other hand, one disadvantage of film coating can be the challenges involved in getting an even thickness across multiple passes of the coating head. Each pass of the valve head lays down a consistent amount and thickness of the coating, but due to the need to overlap the passes, there will be small areas or ridges that contain nearly double the desired thickness. In order to alleviate or eliminate this effect, it is desirable that the coating be very low in thickness or viscosity to allow it to quickly flow and self-level before reaching the curing unit. 

The Solution: Humiseal UV80 and UV80LED

HumiSeal has developed a number of low-viscosity, UV-curable conformal coatings that are suitable for film coating as well as for other applications where thinner coatings are appropriate. UV80 and UV80LED (Technical Data below) are provided at a viscosity of 80CPS to allow for sufficient flow and self-leveling to result in a uniform coating thickness and minimize overlapping ridges when film coating. UV80 requires a full spectrum UV curing bulb, while UV80LED was designed recently to fully cure with single wavelength LED type lights. These products provide the superior protection the industry has come to expect from all Humiseal conformal coatings with the high flow characteristics required of film coating. 

Learn more: UV80LED LV
UV80LED Technical Data Sheet

As a supplier of all major forms and chemistries of conformal coatings, Chase Corporation and HumiSeal® can help you with an unbiased approach to evaluating your application and process. We’ll show you how to maximize efficiency, minimize cost, and improve product reliability. Our outstanding manufacturing and technical support groups can provide your organization with reliable global supply, unmatched quality, and superior technical support. 

Do you have any questions?

Contact Us

Topics: UV Curable (Type AR/UR), conformal coating, conformal coating application, UV Curing

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