9.1 Group III Nitride LED Packaging Materials
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its thermal conductivity [9–13]. The thermal conductive adhesive has the advantages of low price, simple process, insulation performance, etc. Meanwhile, curing
temperature of the material is low. It can even be cured at room temperature.
Gold tin alloy eutectic soldering is also used as thermal interface material. Adding
a certain component to the metal can lower the overall melting point. The eutectic
bonding, also known as low-melting alloy bonding, has many advantages such as high
thermal conductivity, low electrical resistance, high reliability, and high reliability.
Its basic feature is that two different metals can form alloys at a certain temperature,
which is lower than their respective melting points. There are two main cases in
LED eutectic soldering: one is to make a eutectic pad on the heat sink substrate,
but the substrate production process is complex. The other is to prepare the bottom
of the eutectic alloy directly at the bottom of the chip. Gold tin solder has better
thermal conductivity and higher thermal fatigue resistance than tin-based or leadbased solder, and is an excellent packaging material.
For high-power LED packages, besides the requirement of high thermal conductivity, ideal thermal interface materials would have thermal expansion coefficient and
elastic modulus that match the material of the chip substrate. There are also requirements for good mechanical properties, high operating temperatures, low material
and process costs, and sometimes high requirements for the optical properties of the
materials.
9.1.7 Substrate Material
Ideal material for making package substrate should have high thermal conductivity to
transfer heat from the LED chip, while achieving heat exchange and electrical interconnection. Nowadays, high thermal conductivity material such as metal, ceramic,
graphite and composite materials are widely used. In addition, in LED thermal design
and thermal management, materials with low expansion properties and high thermal
conductivity properties such as W/Cu, Mo/Cu, Cu/Mo/Cu, Cu/Mo70Cu/Cu are used.
By adjusting the composition of the material, a good thermo-mechanical match can
be formed with ceramic material, semiconductor material and metal material [14].
It is also a new type of heat-conducting composite material to evenly fill the
polymer matrix material with heat-conducting filler. Generally, it can be divided into
composite heat-conducting plastics and filling heat-conducting plastics, while filling
heat-conducting plastics can be divided into heat-conducting insulating plastics and
heat-conducting conductive plastics [15].
Due to its high thermal conductivity, silicon carbide matches well with the thermal
expansion coefficient of the LED chip. Meanwhile, thanks to its high thermal conductivity, graphene has great potential to be used as heat dissipation substrate material.
Recently, high thermal conductivity graphene/carbon fiber flexible composite film
has been developed in combination with carbon fiber [16, 17], which has made
important progress in the field of flexible heat dissipation of graphene.
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its thermal conductivity [9–13]. The thermal conductive adhesive has the advantages of low price, simple process, insulation performance, etc. Meanwhile, curing
temperature of the material is low. It can even be cured at room temperature.
Gold tin alloy eutectic soldering is also used as thermal interface material. Adding
a certain component to the metal can lower the overall melting point. The eutectic
bonding, also known as low-melting alloy bonding, has many advantages such as high
thermal conductivity, low electrical resistance, high reliability, and high reliability.
Its basic feature is that two different metals can form alloys at a certain temperature,
which is lower than their respective melting points. There are two main cases in
LED eutectic soldering: one is to make a eutectic pad on the heat sink substrate,
but the substrate production process is complex. The other is to prepare the bottom
of the eutectic alloy directly at the bottom of the chip. Gold tin solder has better
thermal conductivity and higher thermal fatigue resistance than tin-based or leadbased solder, and is an excellent packaging material.
For high-power LED packages, besides the requirement of high thermal conductivity, ideal thermal interface materials would have thermal expansion coefficient and
elastic modulus that match the material of the chip substrate. There are also requirements for good mechanical properties, high operating temperatures, low material
and process costs, and sometimes high requirements for the optical properties of the
materials.
9.1.7 Substrate Material
Ideal material for making package substrate should have high thermal conductivity to
transfer heat from the LED chip, while achieving heat exchange and electrical interconnection. Nowadays, high thermal conductivity material such as metal, ceramic,
graphite and composite materials are widely used. In addition, in LED thermal design
and thermal management, materials with low expansion properties and high thermal
conductivity properties such as W/Cu, Mo/Cu, Cu/Mo/Cu, Cu/Mo70Cu/Cu are used.
By adjusting the composition of the material, a good thermo-mechanical match can
be formed with ceramic material, semiconductor material and metal material [14].
It is also a new type of heat-conducting composite material to evenly fill the
polymer matrix material with heat-conducting filler. Generally, it can be divided into
composite heat-conducting plastics and filling heat-conducting plastics, while filling
heat-conducting plastics can be divided into heat-conducting insulating plastics and
heat-conducting conductive plastics [15].
Due to its high thermal conductivity, silicon carbide matches well with the thermal
expansion coefficient of the LED chip. Meanwhile, thanks to its high thermal conductivity, graphene has great potential to be used as heat dissipation substrate material.
Recently, high thermal conductivity graphene/carbon fiber flexible composite film
has been developed in combination with carbon fiber [16, 17], which has made
important progress in the field of flexible heat dissipation of graphene.