The heat dissipation problem is a difficult problem that must be solved in high-power LED packages. Since the heat dissipation effect directly affects the life and luminous efficiency of the LED lamp, it effectively solves the heat dissipation problem of the high-power LED package, and plays an important role in improving the reliability and the service life of the LED package. So bright color electronic today for everyone to explain the main factors affecting the LED package cooling.
The first major factor: package structure
The package structure is divided into two types: micro-spray structure and flip-chip structure.
1, micro spray structure
In the sealing system, the fluid in the fluid cavity forms a strong jet at the micro-nozzle under a certain pressure, and the jet directly impacts the surface of the LED chip substrate and takes away the heat generated by the LED chip, which acts on the micro-pump. Next, the heated fluid enters the small fluid chamber to release heat to the outside environment, causing its temperature to drop, again flowing into the micropump and starting a new cycle.
Advantages: The micro-spray structure has high heat dissipation performance and uniform temperature distribution of the LED chip substrate.
Disadvantages: As the reliability and stability of micro-pumps have a great impact on the system, and the system structure is more complex and increases operating costs.
2, flip chip structure
Flip Chips For conventional positive-fit chips, the electrodes are located on the light-emitting surface of the chip, and thus block part of the light emission and reduce the light-emitting efficiency of the chip.
Advantages: The structure of the chip, the light is removed from the top of the sapphire, eliminating the electrode and lead shielding, to improve the luminous efficiency, while the substrate with high thermal conductivity of silicon, greatly improving the chip's cooling effect.
Disadvantages: The heat generated by the PN of the structure is led out through the sapphire substrate. The sapphire has a low thermal conductivity and a long heat transfer path. Therefore, the thermal resistance of the chip is large and the heat is not easily emitted.
The second largest factor: packaging materials
LED packaging materials are divided into thermal interface materials and substrate materials.
1, thermal interface materials
Thermal interface materials commonly used in current LED packages include thermal conductive adhesives and conductive silver adhesives.
(a) Thermal plastic
The main component of the commonly used thermal plastic is epoxy resin, so its thermal conductivity is small, thermal conductivity is poor, and thermal resistance is large.
Advantages: thermal plastic has the characteristics of insulation, heat conduction, shockproof, easy installation and simple process.
Disadvantages: Because the thermal conductivity is very low, it can only be applied to LED packages that do not require high heat dissipation.
(b) Conductive silver paste
The conductive silver paste is a GeAs, SiC conductive substrate LED, a key package material in a red, yellow, yellow green chip LED package dispensing or backing process with backside electrodes.
Advantages: It has the function of fixed-bonded chip, conduction and heat conduction, and heat transfer, and has an important influence on the heat dissipation, light reflectivity, and VF characteristics of LED devices. As a thermal interface material, conductive silver paste is widely used in the LED industry.
2, substrate material
A certain heat-dissipation path of the LED package device is from the LED chip to the bonding layer to the internal heat sink to the heat-dissipating substrate and finally to the external environment. It can be seen that the heat-dissipating substrate is important for the heat dissipation of the LED package, so the heat-dissipating substrate must have the following features: high Thermal conductivity, insulation, stability, flatness and high strength.
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