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6 Ways to Achieve High Thermal Performance of LED Chips

This month, our Product Manager, Ilia Korovin, discusses six ways to achieve high thermal performance of LED chips including the importance of quality heat paste and a well-designed heat sink.

The light-emitting diode (LED) is today's most energy-efficient and rapidly-developing lighting technology. In the last 5 years LED’s have been getting more and more popular for household, commercial and industrial use. They are replacing incandescent and halogen lamps due to the high energy efficiency, long lifetime and rapidly reducing cost.

Even though LED’s are at the forefront of energy efficient light sources, they still produce anywhere between 60 and 95% heat! Typically, LED’s produce 15% visible light and 85% heat1. This is important to know, because the efficiency and expected lifetime of an LED chip is directly proportional to the ‘junction temperature’ of an LED chip (Figure 1).

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Figure 1 Temperature probe on LED junction

Here are some key facts when it comes to LED junction temperature:

  • LED chip lifetime halves with every 10 degrees increase in junction temperature.
  • Increased junction temperature = decreased light output (reduced efficiency)
  • Increased junction temperature = skewed color temperature

Essentially, correct thermal management of LED chips means LED lights last longer, shine brighter and have the correct color temperature2. Conversely, poor or inconsistent thermal management of LED chips reduces lifetime, reduces lighting efficiency and causes a skewed color output of LED lights.

Light output v LED junction temperature

Figure 2 Light output vs LED junction temperature

So, what can be done to ensure LED chips have high thermal performance and low LED chip junction temperatures? There are a couple of considerations a reputable LED manufacturer should put in place to ensure high quality luminaires with excellent thermal performance:

  1. A high-quality LED chip that has stable thermal management (more on this in another article!).
  2. Well selected heat paste that ensures consistent and efficient thermal transfer between the LED chip and MCPCB (Metal Core Printed Circuit Board) see Figure 3.
  3. A high quality MCPCB with Strong thermal conductivity.
  4. Well selected heat paste that ensures consistent and efficient thermal transfer between the MCPCB and Heat sink (Metal Core Printed Circuit Board) see Figure 3.
  5. A well-designed heat sink that “sucks” away all the heat generated by the LED chip.
  6. A well-designed luminaire shape that maintains its thermal properties over many years.

 

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Figure 3 Heat paste helping deliver greater thermal conductivity1

That’s a lot of information to take in, and the reality is that “the devil is in the details”. A luminaire may look nice and have fancy fins that seem to be impressive, but the ability of the LED chips to stay “cool” will be limited to the weakest link in the thermal conductivity chain.

Perhaps the easiest way to ensure that an LED luminaire is designed correctly and has excellent thermal properties is to request the supplier to provide an “ISTMT Test report”. ISTMT stands for “In Situation Thermal Measurement Test”. ISTMT test reports measure thermal performance of LED chips in their intended use and “project” or “calculate” their expected lifetime given the conditions. More on this in another article!

So don’t forget to ask your LED lighting supplier what they do to ensure proper thermal management of LED chips. An ISTMT test report can provide a higher certainty that they have done their due diligence. Further investigation by asking them how they achieve High Thermal Performance of LED chips as outline above will separate the knowledgeable supplier from the armature.

From left to right we have our ZETTA EKO Mini, ZETTA EKO + and premium ZETTA Highbays. This thermal image shows that our premium ZETTA Highbay runs 10 degrees cooler than our economic ZETTA EKO Mini. 

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Figure 4

Every 5 degrees that we are cooler, lifetime increases by approximately 50%.

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By conducting thorough thermal tests and benchmarking our products we can accurately forecast how long products will last and how well they will perform in different environments. This is standard for all of the products we design and launch because we have made the decision to provide our customers certainty and consistency.

 

How does operating temperature affect your lighting needs? Get in touch and ask us today!

Interested in our ZETTA LED Highbay Range? Enter your email to download the specification sheets. 

 

 (Specification sheets will be sent straight to your inbox - check your junk mail!)

References:

  1. http://www.ledsmagazine.com/articles/2005/05/fact-or-fiction-leds-don-t-produce-heat.html
  2. http://www.lrc.rpi.edu/programs/nlpip/lightinganswers/led/heat.asp

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