LED-curable conformal coatings have gained traction in use cases requiring quick turnaround times, like automotive, white goods, and industrial control products. Besides their high curing rates, LED-curable conformal coatings are highly resistant to environmental and chemical elements. This article takes a deep dive into LED-curable conformal coating as a green approach in the PCB manufacturing process.
An image showing UV-LED to mercury vapor. (Source: Nazdar Ink Technologies)
Before getting into finer details, let’s discuss how traditional UV curing compares with LED-curable conformal coating.
Traditional UV curing
To understand LED-curable conformal coating better, we will go back to the earlier conformal coating methods before the invention of LED-curable conformal coating. Below are some of the pros of the traditional UV-curing conformal process over the older, solvent-borne coating methods:
- Little or no volatile organic content
- Prompt curing
- Short cycle-time potential
- High environmental and chemical resistance
Like other methods, the UV-curing conformal approach also has its disadvantages, such as:
- More energy consumption
- Short light durability
- Contains harmful materials that require sealed designs
- Pollutes the air
- High heat generation
- Heat-cycling problems
LED- curable conformal method
Intensive research was conducted to invent UV-curable coatings cured by high-intensity UVA LED lamps instead of mercury ejection lamps. Below are the benefits of the LED lamp method over the mercury ejection approach:
- Less energy consumption
- Continuous light generation throughout the lamp’s unit lifespan
- Minimal operating temperatures
- No ozone emissions
- No dangerous UVC productions
UVA LED lamps generate single UVA wavelengths ranging from 365 nm to 395 nm. On the other hand, mercury lamps generate multiple wavelengths like UVA, UVB, and UVC bands.
What makes LED- curable green?
The technique of treating conformal coatings with LED is an excellent substitute for solvent-borne and UV-cured coatings. Below are the benefits of LED-curable coating compared with other conformal coatings:
- They are entirely solid.
- They are lightweight, facilitating easy packaging and shipping of products.
- They consume less energy when compared with heat-drying ovens.
- They contain little or no volatile organic content.
When compared with the ancient full-spectrum arc, LED-curing offers the following advantages:
- Fewer power demands
- Minimal maintenance schedules
- Minimal hazardous and ozone emissions
Factors to consider when upgrading from mercury arc to UV LED curing
Every UV-curing technique needs the right match between the spectral immersion of the preparation and the wavelength yield of the ultra-violent curing system. Other process considerations such as component measurements, handling, and manufacturing rates determine the cost of the curing process. Besides, it is essential to partner with process development professionals to conduct a successful LED-curable process with little risk. Let’s have a look at each of these factors.
LED- curable conformal coating formulations
Most UV conformal coatings are highly stable, individual-component, and non-flammable and apply the double-cure technique. After coating, the circuit board is subjected to UV rays for seconds. But a secondary cure, especially moisture and sometimes heat, facilitates the curing process in dim conditions lacking UV energy.
Commercial UV-curable coatings include those that integrate with wide-ranging spectrum arc lamps or LED-curable systems and those that only integrate with the LED-curable system. The first formulation presents the flexibility of two curing methods, while the latter is more effective with quick processing speed. You can also use LED systems to treat thicker coatings and give your board more protection.
Sometimes, you don’t require secondary curing. For instance, if your system contains miniaturized components or discriminatory or high-viscosity coatings, every part can be totally cured by the LED energy through line of sight. LED coating dealers should state the wavelength (395 nm is the standard, but 365 nm, 385 nm, and 405 nm are also available) and whether you require a secondary cure.
Generally, whichever curing process you have used in your current coating can integrate with LED coatings, like automatic discriminatory spray, hand spray, jetting, and brushing. Therefore, the feature of your method remains constant. Some conformal coating manufacturers provide UV LED-curing resins. More resins will be available in the future, as most manufacturers are actively engaging in research and development initiatives.
Low -risk/ high-success process development and qualification
The essential aspect that guarantees success and gives a good return on investment when upgrading to a LED-curable system is finding the right professionals to guide and back your efforts. Even during the first feasibility process, you need support from resin and LED-curable system manufacturers to get authentic and accurate data for your custom application. Besides, you can start evaluating suppliers and creating relationships with the top testing and processing companies.
Look for partners proficient in conformal coating and who can conduct tests internally or loan you their LED-curable devices to carry out pilot studies and validate your process and manufacturing speed. Consider which training and after-sales assistance you may require, like repair services; if you are an international company, look for partners with a global presence.
The LED -curing process and equipment options
Manufacturing rates, PCB processing measurements, flexibility required, vibrant versus motionless cure, height variations, conveyor speed regulation, darkening capacity, UV energy yield, and controls combined with the coating system are examples of the LED-curing process and device alternatives to consider.
Your current method and preferred rates are the ideal factors to base your design requirements for an LED-curable conformal coating. For instance, if your current method applies a motionless cure with batch processing, your preferred manufacturing rates may require the use of a constant method with a flat-line conveyor. However, if your existing process is continuous, you can complement it with the LED-curable machine, considering its small-form aspect.
If you want the flexibility to handle several products, consider UV-curing devices that can easily adjust to multiple production requirements. Basically, a flexible system presents high production flexibility through the curing width and quick conversions to various wavelength yields. You also consider the capacity to cure at different operating distances.
Besides, assess the ownership cost of your LED-curing system, not just the initial expenses. Unlike mercury arc lamps, LED-curing systems demand little maintenance and energy; therefore, their working and downtime expenses are lower. Nevertheless, upgrading to the latest LED chip technique is expensive. A standard LED-curable method with specific measurements may even be more costly to upgrade to the LED chip method, as you need to buy a completely new curing unit. Therefore, go for a system that requires only the LED array replacement while maintaining the other units like the housing, cooling system, and controls.
Applications of LED- curable conformal coatings
LED-curable conformal coatings are ideal for almost all conservative coating applications. They have unique aspects such as minimal UV energy consumption, fewer maintenance schedules, and high production rates, making them more suitable for:
- Automotive circuit boards because of their high capacities and energy demands
- White equipment like refrigerators, microwaves, and dryers
- HVAC control systems
- Electronic automotive applications such as power and safety controls
UV LED-curable conformal coatings have been embraced well in applications dealing with white products and automotive, in which high-volume throughput, minimal energy, and maintenance needs are essential. More industries are also emphasizing the application of eco-friendly PCB materials. UV LED-curable conformal coatings will play a significant role in shaping this green evolution.
As discussed in the article, you should partner with reputable conformal coating suppliers to obtain an impartial tactic to assess your conformal coating application and process. They will help you to maximize efficiency and reduce costs while enhancing the product quality. Your preferred supplier should also have production and technical support experts to offer you reliable borderless supply, high quality, and excellent technical support in case of repairs and maintenance.
>> This article was originally published on our sister site, Power Electronics News.
|Linda Liu is the overseas marketing manager for MKTPCB, a leading PCB manufacturer that offers high-quality PCB products and services. Since 2012, she has established “first-of-its-kind” industry-changing and transformational businesses initiatives that increased revenue growth, brand exposure and market expansion for MKTPCB. Linda graduated from Western University with a bachelors degree in marketing.|
- Top PCB trends and challenges
- Epoxy’s diverse role in IoT device PCB manufacturing
- Integrating chip antennas into a PCB: Understanding antenna matching
- Tech advances behind Industry 4.0 bring new challenges for PCB manufacturing
- PCB design package takes to the cloud
- How to place two or more antennas in one design
For more Embedded, subscribe to Embedded’s weekly email newsletter.