-Deacon Wardlow
Heat can kill your display’s performance and longevity. High heat can shorten the lifetime of LEDs and decrease the performance of the system overall.
Heat buildup in the system can be resolved with a series of engineered solutions. Thermostatic fans, proper conformal coating, thermal management of the systems, and overall engineering should ensure the system not only distributes and pulls heat away from critical components (Power Supplies and LEDs) but also keeps the system performing optimally throughout its lifetime.
Thermostatic Fans:
Thermal switches placed with high-grade industrial fans are a key component for increasing the longevity of the fan and ensuring the best-use of vented cooling on a system. The thermal switch should be preset at certain thresholds to ensure fans only run when additional venting/cooling is required to keep your LED message center running at its best. This reduces wear and (eventual) part replacement cost to the end user and keeps the fans lasting as long as the full sign system; circulating air through the system to avoid heat buildup.
Thermal Management:
Each and every cabinet should be forward-engineered for optimal heat management. Components need to be carefully laid out in the initial design stage to ensure heat is evenly displaced throughout the cabinet and air flow is optimized to avoid any thermal buildup.
Conformal Coating Controls:
Conformal Coating of components (see my previous blog article and the Vantage LED white paper on power supplies) should be carefully controlled in the build-phase for LED modules and circuit boards. Different PCBs (Printed Circuit Boards) have different coating requirements. Matching the CTE (Coefficient of Thermal Expansion) to the PCB ensures the right amount of coating for the different components. CTE is volume-dependent and the thicker the coating, the greater the likelihood these changes can cause heat buildup in a system which can damage heat-sensitive components (like LEDs).
Conformal Coating materials:
Materials need to be carefully evaluated to ensure the right material is matched with the coated surface. A material like silicone can have a high CTE and low modulus (expansion or compressive forces). As a result, silicones in general do not cause significant stresses on sensitive components. On the other hand, silicones trap heat and could cause other issues (see previous blog article on silicone coating). Urethanes and epoxies have been historically high modulus materials and don’t have as many heat problems. Thus it's important to understand why the manufacturer chose the coating type and they are able to justify their choice.
It’s important to ensure every step and stage of the build process is monitored for quality control. From initial engineered concept to completed component/system, the build line needs to be carefully controlled to ensure the highest quality components, protection and engineering is utilized. The result, a system which performs optimally regardless of the heat and environment its placed in.
* Always feel free to comment here and/or email me directly with requests at deacon@vantageled.com. Vantage has white paper resources and more educational material on the website (http://www.vantageled.com), please check it out when you have a moment. Advertisements/promotion for your business and inappropriate comments will be deleted.. Thank you!
**Note all posts/thoughts/writings are strictly the viewpoint of me and me alone and do not reflect nor speak for Vantage LED’s beliefs, attitudes, thoughts, etc. unless specifically stated.
-Deacon Wardlow
Imagine the hot sun beating down on a dry July afternoon. The temperature is up past 95 and that’s in the shade. Now imagine grabbing a big rubber rain jacket, boots and rubber pants and putting them on. Not likely something anybody would want to do in the middle of a heatwave, right? Some people disagree and coat the back of LED module with a layer of black silicone insulating material to “protect” the system.
It’s easy to see why someone would want to use silicone insulation:
· Operational temperatures from -148F to 600F
· Inherently good electrical insulation qualities
· High level of functionality regardless of types weather (rain/snow/wind)
· Low permeability (resistant to moisture and exposure to condensation buildup)
However, while the low permeability is great for the back of an LED module (no corrosion or exposure to the elements for the electrical connections) the low permeability causes issues. While some types of silicone are made to manage heat (thermal grease used on computer CPUs is one example), silicone used on the backing of LED tiles is an insulator material made to protect the tile components from water, chemical, ESD (electro static discharge) and other environmental hazards.
Unfortunately, insulators trap heat and will minimize the potential long-term optimal performance of the LEDs which make up the tile. LEDs do not radiate heat but rather hold the heat in and this leads to a breakdown in the material components, causing the LED to dim and lose color prematurely. To deal with this heat, manufacturers take great pains to draw heat away from the LED light fixture. In this case, the fixture is the LED panel itself.
A sign is an business’ image. The sign you sell to your clients reflects back on you and your hard earned reputation. Don’t take a chance, make sure you get all the facts up front. While it’s cool to see LED tiles functioning under water, shouldn’t the seal around the tiles keep water from getting to the back of the LED modules in the first place? Don’t let a poor coating choice get your clients hot and bothered.
* Always feel free to comment here and/or email me directly with requests at deacon@vantageled.com. Vantage has white paper resources and more educational material on the website (http://www.vantageled.com), please check it out when you have a moment. Advertisements/promotion for your business and inappropriate comments will be deleted.. Thank you!
**Note all posts/thoughts/writings are strictly the viewpoint of me and me alone and do not reflect nor speak for Vantage LED’s beliefs, attitudes, thoughts, etc. unless specifically stated.
-Deacon Wardlow
Heat kills LEDs. The death knell of a typical Red-Green-Blue (RGB) full color LED display is seen in depreciated light quality, poor color quality and eventually a dim, dying sign. Typical lights dissipate heat by radiating the heat outward from the source. LEDs unfortunately hold the heat in and high temperature slowly breaks down the components causing a multitude of problems. Red LEDs burn out faster and this is usually seen on a message center when “clean white” turns to a bluish hue because of the lack of strong Red LED components.
Thermal (heat) management is critical to the longevity and continued high-level of performance for a message center. Manufacturers tend to deal with thermal management in a variety of ways:
- Heat sinks (metal spread out and “finned” to allow for heat to draw away from the LED and let passive/active airflow over the fins dissipate heat buildup
- MCPCB (Metal Core Printed Circuit Board) – a rare option due to increased expense
- Separation – a popular method, LEDs are separated from the circuit board using longer “legs” which allows for air flow to draw heat from the LED through the extended legs, unfortunately proper placement/setting of LEDs is difficult and can result in bad contacts which leave “dead pixels” on a sign.
All the above methods serve to draw heat away from the LED source thus keeping the LED relatively cool and ensuring the highest performance and longest life possible. With this in mind, here are LED killers to watch for on an LED module (also known as a driver/board):
1. ANY type of heavy/dark silicone coating on the back of an LED PCB (Printed Circuit Board: Silicone coatings have the benefit of reducing exposure to condensation which can oxidize metals, but it’s better to use a light conformal PCB coating. Heavy silicone coatings trap heat and don’t leave any place for the heat to be drawn away. Be wary of modules with “heat sinks” as the heat sinks often don’t have trace leads (metal pathways from the LED to the heat sink) and thus do not work to reduce heat on the overall module.
2. LEDs which have no louvered (shaded) protection: the louvers on a face plate for an LED module act like an umbrella at the beach. They serve a dual purpose of allowing LEDs to shine their brightest in daylight conditions while also giving them some protection from direct overhead sun exposure. If you see a face plate with exposed silicone, be especially wary. The silicone acts as a sealant to protect the LED module face from weather elements, but an exposed silicone coating is prone to UV (Ultra Violet) solar radiation which will crack the sealant and cause eventual exposure to the elements which will kill the module over time.
3. LED modules which are “fully enclosed” from the rear: Picture a medieval knight in full armor standing in the summer sun, that knight is likely more than a little warm. While the rear seal plating looks great on an LED module and it sounds good to have a “waterproof” LED module, the plating doesn’t ultimately protect the LED, it harms the LEDs in a module because heat has no source to vent off to. If the manufacturer is using a rear-face module, have them show you a cutaway or internal view to see how they’re drawing heat to the back plate. If they aren’t drawing heat from the LEDs to the back plate, they’re slowly killing your sign.
Ask the manufacturer how they protect your investment. How do they deal with heat in the message center? If they do any of the three “killers,” be VERY wary of investing your name, brand and reputation with them…
*Always feel free to comment here and/or email me directly with requests at deacon@vantageled.com. Vantage LED has white paper resources and more educational material on the website (http://www.vantageled.com), please check it out when you have a moment. Advertisements/promotion for your business and inappropriate comments will be deleted.. Thank you!
**Note all posts/thoughts/writings are strictly the viewpoint of me and me alone and do not reflect nor speak for Vantage LED’s beliefs, attitudes, thoughts, etc. unless specifically stated.
