9.4 Package and System Cooling Technology
199
High-power LED luminous intensity and power dissipation are high, efficient way
of cooling is much needed. In addition, stable encapsulating material and advanced
packaging technology are needed to solve the long-term reliability problems. From
the actual needs of LED lighting applications, the development of power-type packaging technology with low thermal resistance, high reliability, micro, and excellent
optical characteristics, as well as high-power LED packaging and system integration
technology are the key to realize the industrialization of LED lighting. This is also
an important development trend.
The cooling technologies involved in LEDs include a list of methods, which will
be discussed below.
Natural cooling: natural convection cooling is often used for low-power devices
and single high-power devices to dissipate heat. Fin cooling is the most common
method.
Air-cooling: ordinary fans have low noise, high power consumption, and poor
reliability. The rotating magnetic field around the fan drives the normal operation of
the surrounding electronic components due to magnetic leakage or electric spark, so
it is rarely used in LED heat dissipation.
Liquid cooling: it consists of water cooling, microchannel cooling, micro spray
cooling, porous micro heat sink cooling, liquid metal cooling.
Heat pipe cooling: it is a phase change heat transfer element with high thermal
conductivity. It can be also considered as a heat conduction element that relies on
internal working phase transformation for efficient heat transfer. It has a large heat
transfer rate with a small temperature difference, simple structure, and a unidirectional heat conduction. Therefore, there are many advantages to apply heat pipe
technology in SSL. Ordinary aluminum profiles, brazing and other types of heat
sinks could not meet the thermal resistance requirements, and need to adopt a new
type of radiator with superior performance.
Micro-slot group composite phase change heat dissipation technology: this is a
new generation of high-intensity micro-size fine-scale phase-change heat transfer
technology, which is developed on the basis of heat pipe technology. It avoids technical defects of heat pipes, and significantly improves technical capabilities. In microscale micro-groove geometry, there is very small amount of working fluid. The fluid
flows along the micro-groove under the capillary pressure gradient formed by the
micro-groove group’s own structure. No additional power consumption is required
[31].
Semiconductor thermoelectric refrigeration: It is also called thermoelectric refrigeration or heat pump. It has the advantage of no sliding parts and is used in applications where space is limited. The reliability is high, and there is no refrigerant
contamination. Using a semiconductor material Peltier effect, when the galvanic
series into a direct current through two different semiconductor materials, at both ends
of the couples can respectively absorb heat and release heat, cooling purposes can be
achieved. It is a refrigeration technology that produces negative thermal resistance,
which is characterized by no moving parts and high reliability.
199
High-power LED luminous intensity and power dissipation are high, efficient way
of cooling is much needed. In addition, stable encapsulating material and advanced
packaging technology are needed to solve the long-term reliability problems. From
the actual needs of LED lighting applications, the development of power-type packaging technology with low thermal resistance, high reliability, micro, and excellent
optical characteristics, as well as high-power LED packaging and system integration
technology are the key to realize the industrialization of LED lighting. This is also
an important development trend.
The cooling technologies involved in LEDs include a list of methods, which will
be discussed below.
Natural cooling: natural convection cooling is often used for low-power devices
and single high-power devices to dissipate heat. Fin cooling is the most common
method.
Air-cooling: ordinary fans have low noise, high power consumption, and poor
reliability. The rotating magnetic field around the fan drives the normal operation of
the surrounding electronic components due to magnetic leakage or electric spark, so
it is rarely used in LED heat dissipation.
Liquid cooling: it consists of water cooling, microchannel cooling, micro spray
cooling, porous micro heat sink cooling, liquid metal cooling.
Heat pipe cooling: it is a phase change heat transfer element with high thermal
conductivity. It can be also considered as a heat conduction element that relies on
internal working phase transformation for efficient heat transfer. It has a large heat
transfer rate with a small temperature difference, simple structure, and a unidirectional heat conduction. Therefore, there are many advantages to apply heat pipe
technology in SSL. Ordinary aluminum profiles, brazing and other types of heat
sinks could not meet the thermal resistance requirements, and need to adopt a new
type of radiator with superior performance.
Micro-slot group composite phase change heat dissipation technology: this is a
new generation of high-intensity micro-size fine-scale phase-change heat transfer
technology, which is developed on the basis of heat pipe technology. It avoids technical defects of heat pipes, and significantly improves technical capabilities. In microscale micro-groove geometry, there is very small amount of working fluid. The fluid
flows along the micro-groove under the capillary pressure gradient formed by the
micro-groove group’s own structure. No additional power consumption is required
[31].
Semiconductor thermoelectric refrigeration: It is also called thermoelectric refrigeration or heat pump. It has the advantage of no sliding parts and is used in applications where space is limited. The reliability is high, and there is no refrigerant
contamination. Using a semiconductor material Peltier effect, when the galvanic
series into a direct current through two different semiconductor materials, at both ends
of the couples can respectively absorb heat and release heat, cooling purposes can be
achieved. It is a refrigeration technology that produces negative thermal resistance,
which is characterized by no moving parts and high reliability.