Thermal problems are high-power LED packaging must focus on solving the problem. As the cooling effect directly affects the life and luminous efficiency of LED lights, so effectively solve the problem of high-power LED package cooling, LED packaging to improve the reliability and life plays an important role. So what is the main factor affecting the LED package cooling.
The first major factor: the package structur
The encapsulation structure is divided into micro-spray structure and flip chip structure.
1, micro-spray structure
In this sealing system, the fluid in the fluid chamber creates a strong jet at the micro-ejection under a certain pressure, which directly impacts the surface of the LED chip substrate and carries the heat generated by the LED chip, , The heated fluid enters the small fluid chamber and releases heat to the outside environment, lowering its temperature and flowing into the micropump to start a new cycle.
Advantages: micro-spray structure with high heat dissipation and LED chip substrate temperature distribution.
Disadvantages: Due to the reliability and stability of the micropump on the system a great impact, and the system structure is more complex to increase the operating costs.
2, flip chip structure
Flip chip for the traditional mounted chip, the electrode is located on the chip's light-emitting surface, which will block part of the light, reducing the chip's luminous efficiency.
Advantages: the structure of the chip, the light from the top of the sapphire removed, eliminating the electrode and lead shading, improve the luminous efficiency, while the substrate with high thermal conductivity of silicon, greatly improving the chip heat dissipation.
Disadvantages: the structure of the PN generated by the heat generated by the sapphire substrate, sapphire thermal conductivity is low and the heat transfer path is long, so this structure of the chip thermal resistance, heat is not easy to emit.
The second major factor: packaging materials
LED packaging materials are divided into two kinds of thermal interface materials and substrate materials.
1, thermal interface materials
The current LED package commonly used thermal interface materials are thermal plastic and conductive silver paste.
(A) Thermal glue
Commonly used thermal conductive adhesive is the main component of epoxy resin, and thus its thermal conductivity is small, poor thermal conductivity, thermal resistance.
Advantages: thermal plastic with insulation, thermal conductivity, shock, easy installation, simple process and so on.
Disadvantages: because the thermal conductivity is very low, and therefore can only be applied to the heat dissipation is not demanding on the LED package device.
(B) conductive silver paste
Conductive silver plastic is GeAs, SiC conductive substrate LED, with the back electrode of the red, yellow, yellow and green chip LED packaging dispensing or preparation of the key packaging materials in the process.
Advantages: with a fixed bond chip, conductive and thermal conductivity, heat transfer effect, and the LED device heat dissipation, light reflectivity, VF characteristics have an important impact. It is a thermal interface material, the current conductive silver paste in the LED industry has been widely used.
2, the substrate material
LED packaging device, a cooling path from the LED chip to the bonding layer to the internal heat sink to the heat sink Finally to the external environment, you can see the heat dissipation of the substrate on the importance of LED package cooling, and thus the cooling substrate must have the following characteristics: high Thermal conductivity, insulation, stability, flatness and high strength.