Analysis of Five Misunderstandings of LED Heat Dissipation and Seven Solutions

With the wide application of LEDs, more and more attention has been paid to the heat dissipation of LEDs. The heat dissipation performance of LEDs will directly affect the life of LED products.

Analysis of Misconceptions in LED Heat Dissipation

Low internal quantum efficiency

When electrons and holes recombine, not all of them generate photons at 100%. This is commonly referred to as "current leakage," which reduces the recombination rate of carrier particles in the PN region. 

The power of this portion is the leakage current multiplied by the voltage, resulting in thermal energy conversion. 

However, this component does not constitute the main factor, as the internal photon efficiency is already close to 90% nowadays.

Inability to fully emit internally generated photons outside the chip, leading to heat conversion

This is the main issue because the external quantum efficiency, which represents the portion of photons that can escape the chip, is only about 30%. The majority of the photons are converted into heat.

Excessive reliance on thermal conductive materials

There is a misconception that any high-tech material can effectively dissipate heat. In reality, using ordinary aluminum heat sinks, after multiple tests, the temperature difference between the heat sink and the bottom of the sink is only about 3-5 degrees Celsius. 

In other words, even if an extremely efficient thermal conductive material were to be used, assuming zero thermal resistance, the temperature could only be reduced by 3-5 degrees Celsius.

Blind faith in heat pipes

Heat pipes indeed have excellent thermal conductivity, which is undeniable. However, the heat transferred from the heat sink through the heat pipe ultimately needs to be dissipated through air convection. 

If there are no heat-dissipating fins, the heat pipe will quickly reach thermal equilibrium, causing the temperature to rise along with the heat sink. 

Even if heat-dissipating fins are added to the heat pipe, the heat will still be dissipated by the fins. 

Moreover, the contact between the fins and the heat pipe is not as effective as other contact methods. 

As a result, the cost increases without improving the heat dissipation effect. 

However, heat pipes can still be useful for thermal management in integrated LEDs, provided they are used in a well-designed structure. 

Overreliance on nano-radiation materials promoted by some manufacturers

At present, in LED luminaires operating at around 50 degrees Celsius, the proportion of heat dissipation through radiation is negligible. 

Even if the radiation coating promoted by manufacturers exhibits excellent radiation properties, assuming it achieves the radiation capability of a blackbody, its contribution to heat dissipation is only a few percentage points. 

Furthermore, the coating itself can hinder heat dissipation through convection by impeding heat transfer, thereby affecting overall heat dissipation.

Methods for Addressing LED Heat Dissipation Issues

Aluminum heat fins

This is the most common method of heat dissipation, where aluminum heat fins are used as part of the housing to increase the heat dissipation surface area.

Thermal conductive plastic casing

Using LED-insulated thermal conductive plastic instead of aluminum alloy for heat dissipation bodies can significantly improve thermal radiation capability.

Aerodynamics

By designing the shape of the lamp housing to create airflow, convection cooling can be achieved. This is the most cost-effective method to enhance heat dissipation.

Liquid-filled bulb

Using liquid-filled bulb encapsulation technology, a transparent liquid with high thermal conductivity is filled inside the lamp bulb. This is the only technique that utilizes both light reflection and LED chip surface heat conduction for heat dissipation.

Utilizing the lamp base

In small power LED lamps for household use, the internal space of the lamp base is often utilized to house the heat-generating driver circuit, either partially or entirely. 

This allows heat dissipation through the lamp base, which has a large metal surface in close contact with the lamp socket's metal electrode and power line. Therefore, a portion of the heat can be dissipated through this method.

Insulated thermal conductive plastic replacing aluminum alloy

By using LED-insulated thermal conductive plastic instead of aluminum alloy for heat dissipation bodies, the thermal radiation capability can be increased 4-8 times while maintaining comparable heat dissipation performance to aluminum alloy. 

LED heat dissipation bodies made from this material can significantly improve overall heat dissipation effectiveness.

Integration of thermal conductivity and heat dissipation - Application of high thermal conductivity ceramics

The purpose of lamp housing heat dissipation is to reduce the working temperature of the LED chip. Due to the significant difference in thermal expansion coefficients between LED chips and commonly used metal thermal conductive and heat dissipation materials, direct soldering of LED chips is not feasible to prevent high and low-temperature thermal stress from damaging the LED chips.

The latest high thermal conductivity ceramic materials have a thermal conductivity close to that of aluminum, and their thermal expansion coefficients can be adjusted to synchronize with the LED chips. This allows for the integration of thermal conductivity and heat dissipation, reducing intermediate links in heat conduction.