Many people believe that Light Emitting Diodes (LEDs) don’t emit thermal energy as a by-product of operation. This belief is wrong. Whilst they may not emit radiant heat in the same way that an incandescent light source will, heat is definitely still generated.

Yes, despite being well-intentioned, the belief that light sources which are built using LEDs will remain completely cool when turned on is misinformed. Dangerously so, in fact, as by failing to recognise that LEDs emit thermal energy which must be conducted away from the component itself, retailers, visual merchandisers and interior designers (amongst others) are unknowingly reducing the lifespan of their lighting systems.

With the growth of the LED market showing no signs of slowing down, we find ourselves forced to ask the question: why are so many industry professionals still unaware of the principles of thermal management? Maybe it’s a trend we can attribute to past juxtapositions of LEDs against halogen alternatives or perhaps it’s a result of the correct information not being made readily available outside of specialist circles? Regardless of the reason, it’s crucial for anyone who identifies as a commercial fitout manager, engineer, designer or otherwise to educate themselves on the importance of thermal management when dealing with LED lighting.

After reading this article, you will have a far greater insight into the importance of proper thermal management in LED technologies as well as a deeper understanding of the practical ways in which this should form an integral part of the technology at the core of all LED-based products.

The Science

LEDs are a type of semiconductor that combine a P-type semiconductor with an N-type semiconductor. The P-type layer has a large concentration of holes making it positively charged whereas the N-type layer has a large concentration of electrons making it negatively charged. When sufficient forward voltage is applied to the LED, the electrons and holes are forced together in the space between the two layers (referred to as the ‘P-N junction’) and release energy in the form of light [see Figure 1].

However, it is not only light energy which is released during this process of electroluminescence. The electrical current is also converted into heat energy as a by-product. This heat energy can cause the temperature at the P-N junction to exceed its maximum operating level which, in some cases, leads to catastrophic failure.

Figure 1: Diagram showing the forced interaction between the positively charged and negatively charged semiconductors at the PN junction inside the die.

 

Thermal Management in Practice

Luckily, there are ways to avoid such failures. In well-engineered LED light sources, elements referred to as heat sinks are used to manage unwanted heat energy at the P-N junction and protect the lifespan and performance of the LED itself. These can vary in size, shape and composition, but are often fixed directly onto the back of an LED PCB in order to increase its surface area and maximise the rate at which heat is conducted away from the diode.

One of the most efficient and environmentally friendly materials used in the manufacture of LED heat sinks is aluminium. Moreover, due to its high thermal conductivity, often, only a thin layer of aluminium is needed to manage unwanted heat energy meaning that it is also one of the most cost-effective options.

If excessive heat is allowed to build up within LEDs it can result in visible inconsistencies in colour temperature and reduce the longevity of light output, both of which will greatly impact the quality and cosmetic appearance of the objects being illuminated [see Figures 2 and 3]. This means that designers, visual merchandisers and contractors risk receiving unnecessary customer complaints and hefty rectification pay-outs if they overlook the importance of thermal management.

Figure 2: Graph showing the strong negative correlation between temperature increase and light output decrease.
   

 

Key Points to Remember

  • LEDs DO emit heat as a direct result of operation (anyone who suggests otherwise is not properly informed on LED technology and is likely to create poor-quality products as a consequence).
  • The lifespan of light sources using LEDs can be protected against degradation by integrating effective thermal management methods into the product itself.
  • Aluminium is one of the most efficient materials for thermal management, meaning that light sources built using aluminium frameworks are likely to perform best and have the longest possible lifespans.

At Unibox, our Technical Engineers and Product Developers carry out extensive testing on LED components to ensure that our products perform to the highest standard for as long as possible. In our on-site electronics lab, we are constantly trialling new heat management systems to determine which will be the most efficient, cost-effective method for our clients.

Visit the Unibox website to learn more about our range of LED-based solutions and see how they can be tailored to meet the specific needs of retailers, architects, interior designers and exhibition contractors.