Tuesday, July 10, 2012

LED Sign Killers: Heat & how to protect against it.

-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.

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