5 Reasons Why Ceramic PCBs are the Best Choice for UVC LED Modules

UVC LED modules are devices that emit ultraviolet light in the C range (200 to 280 nm), which has germicidal properties and can be used for disinfection, sterilization, and purification. UVC LED modules have many advantages over conventional UV lamps, such as lower power consumption, longer lifespan, and environmental friendliness and studies suggest reduced health risks.

However, these modules also pose some challenges for the circuit board design, as they require high thermal conductivity, high reflectivity, and high reliability. In this article, we will list 5 reasons why we believe ceramic PCBs are the best choice for UVC LED modules and offer some design tips and tricks to start designing your own.

Advantages of Ceramic Circuits for UVC LED Modules

Ceramic PCBs are circuit boards that use ceramic materials as the substrate, instead of the traditional FR4 or metal core. Ceramic PCBs have several advantages for UVC LED modules, such as:

1. High Temperature Conductivity and Resistance: Ceramic PCBs can conduct heat and withstand higher temperatures than traditional materials, making them ideal for high power UVC LED modules that generate significant heat as they still have a relatively low efficiency. This means that ceramic PCBs can reduce the thermal stress and improve the thermal management of the LED modules. The thermal conductivity varies with the ceramic material from 20-24 w/mK for alumina 96% to >170 W/mK for Aluminum Nitride.

2. Improved Lifetime: The durability and robustness of ceramic materials can lead to a longer lifespan for the LED modules, reducing maintenance and replacement costs. Ceramic PCBs have a low coefficient of thermal expansion, which means they do not expand or contract as much as other materials when exposed to heat. This reduces the risk of cracking, delamination, and solder joint failure. Ceramic PCBs also have a high dielectric strength, which means they can resist high voltages and prevent electrical breakdown.

High reflective UV mask - CERcuits

Photo: Alumina circuits with copper metallization and white UVC reflective mask

3. Increased Miniaturization: Ceramic circuits allow for a more compact design, enabling chip-on-board designs to be smaller and more efficient. Chip-on-board (COB) is a technique that directly mounts the LED chips on the PCB, eliminating the need for packaging. This reduces the size, weight, and cost of the LED modules, as well as the parasitic capacitance and inductance. Ceramic PCBs can have a high density of vias and pads, which allows for a finer pitch and a higher integration and array layout of the LED chips.

4. Harsh Environment Suitability: Ceramic PCBs are resistant to harsh environmental conditions, including high humidity and chemical exposure. Ceramic PCBs have a low-to-none moisture absorption rate, which means they do not swell or degrade when exposed to water or moisture. Ceramic PCBs can also have a high corrosion resistance, which means they do not react with acids, alkalis, or solvents. This makes ceramic PCBs suitable for UVC LED modules that are used in outdoor, medical, or industrial applications.

5. Reflective Mask for UVC: CERcuits has developed the process to apply a special mask solution for ceramic circuits that can reflect over 80% of UV-C light, increasing efficiency, output and uniformity and reducing surrounding material degradation. Read about the UV-C mask here.

LED starboard printed circuits in AlN ceramic with a UV reflective white coating and gold finish.

Photo: LED Starboard PCB for 3535 footprint LED with ENIG finish and UVC reflective mask

Design Tips and Tricks

To maximize the benefits of ceramic PCBs for UVC LED modules, it is important to follow some design tips and tricks, such as:

1. Choose the right ceramic material:

There are different types of ceramic materials that can be used for PCBs, such as alumina, aluminum nitride, sapphire, zirconia, … . Each material has its own properties and characteristics, such as thermal conductivity, dielectric constant, and cost. For UVC LED modules, the most commonly used ceramic materials are:

Alumina 96 (Al2O3 96%) which is a very good reflector of UV-C light by itself, hermetic, and resistant to most chemical hazards and mechanical wear. It has a good balance of performance and affordability.

Aluminum Nitride (AlN) is typically chosen for high-power and dense chip-on-board arrays thanks to its extremely good thermal conductivity (170W/mK) and low coefficient of thermal expansion (CTE) matching the chip and many other components. It is also a good electric isolator making it suitable for complex double-sided designs. It is less resistance to hazards or reflective then Alumina but still much better then traditional PCB and thanks to the reflective mask the reflectively can be optimized again..

2. Optimize the heat path:

Ceramic circuits have a great Z-axis thermal conductivity whereas traditional PCB’s or metal core circuits require you to spread the heat on the surface using thick copper layers. This is not necessary for ceramic. Typically, most of the thermal resistance is arising from the interface between the circuit and the heatsink. We therefore advise to use a thermal interface material to improve this or to incorporate the heatsink into the pcb like our PCB-on-heatsink solution.

3. Packaged UVC LEDs versus Chip-on-board arrays:

Depending on the functionality, availability and assembly processes you can decide between using packaged UV-C LEDs or chip on board design.

– Packaged LEDs are typically easier to obtain, the assembly is easier and can be done in one flow with pick-and-place & reflow processes and they might have integrated optics. However, they are bigger so the module will grow, they result in higher thermal resistance (longer heat path) and are more expensive for higher volumes. Note that most of the package and submount material for UVC are also alumina or aluminium nitride ceramic based.

Chip-on-board arrays are superior when you need smaller, yet powerful modules that are cost effective. They enable better thermal management and optimized space utilization. However, they often do require additional (wire)bond & die attach processes that adds initial costs and the availability of chips is very depending on the LED manufacturer. Also you might need to spend more time on the optics that is otherwise provided in the package.

4. Thickness – being sturdy versus a lower thermal resistance

Typical ceramic circuit thicknesses vary between 0.25 & 0.38 mm (10-15mil) until 1mm (39 mil). Thicker circuits are possible but not as common for circuits that use heatsinks for cooling. For single layer designs that are just a few cm long an wide, 0.38mm or 0.5mm are good options as they provide a short path to the cooling block. However, if you have a double layer design, you might want to avoid any tracks running on the backside between the heatsink and the back of the board so better is to move them to the side. In this case, there will be a bit of overhang of the circuit versus the heat dissipator and a thicker, sturdier, circuit is advised like 1mm.

 

If you need support in the design of the ceramic circuit board or if you need a assembly or bonding partner. We have a partner network that we can link you up with.Simply contact us.

 

Conclusion

Ceramic PCBs are the best choice for UVC LED modules, as they offer many advantages over traditional materials, such as high temperature conductivity & resistance, improved lifetime, increased miniaturization and harsh environment suitability, By addind CERcuits’reflective mask for UVC, issues with efficiencies on aluminium nitride are solved.

However, to fully utilize the potential of ceramic PCBs, it is essential to follow some design tips and tricks, such as choosing the right ceramic material, optimizing the heat path to the heatsink, consider the type of LEDs & assembly method, and what thgickness suits your application best. 

By doing so, you can create high-performance, high-efficiency, and high-reliability UVC LED modules that can meet your needs and expectations while remaining cost-efficient for many applications regarding disinfection, curing, water & air purification, food preservation, DNA sequencing, …

CERcuits UVC LED solutions

We are one of the premier producers worldwide for UVC LED ceramic circuits for both packaged LED designs as well as chip-on-board modules. With our own flexible in-house production line, we can supply small batches for development or prototyping on a quick turnaround and we can also ensure a stable supply chain for when you move to production. We also have a growing line of standard circuits design for typical UVC LED from various manufacturers that are available on stock for immediate shipment

If you want to discuss a potential program or are in need of higher volumes or you need a pdf quote. Please do not hesitate to contact us.

 

Aluminium nitride Printed circuit board - LED array with high reflective white solder mask and ENIG surface finish

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Alumina 96% (Al2O3) Aluminum Nitride (AlN)
LED starboard printed circuits in AlN ceramic with a UV reflective white coating and gold finish.

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standard UV PCB

Starboard PCBs
High reflective UV mask - CERcuits

UV Mask

>80% reflectance in UVC spectrum

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