is a High-tech products, which led chip is its core components, heat dissipation is a high-power led packaging must focus on solving the problem. As the effect of heat dissipation directly affects the life and luminous efficiency of LED lamps, it effectively solves the problem of high-power led package heat dissipation, which plays an important role in improving the reliability and life of LED package.
So what is the main factor affecting the cooling of the LED package.
The first major factor: encapsulation structure
The package structure is divided into two types: micro-jet structure and flip chip structure.
1, micro-spray structure In the sealing system, the fluid in the flow cavity forms a strong jet at the micro-nozzle at a certain pressure. The jet directly impact the surface of the LED chip substrate and take away the heat generated by the LED chip, under the action of the micro-pump, the fluid is heated into a small fluid cavity to release heat to the external environment, so that its temperature drops,Again into the micro-pump to start a new cycle.
Advantages: The micro-spraying structure has high heat dissipation performance and the temperature distribution of the LED chip substrate is even.
Disadvantage: Because of the reliability and stability of the micro-pump, the system has a great influence on it, and the structure of the system is more complicated and the operating cost is increased.
2. Flip Chip structure
Flip chip for the traditional chip, the electrode is located in the light-emitting surface of the chip, thus shielding part of the light-emitting, reduce the efficiency of the chip's luminescence.
Advantages: This kind of structure of the chip, light from the top of the sapphire out, eliminating the electrode and lead shading, improve the luminous efficiency, while the substrate using high thermal conductivity of silicon, greatly improve the chip cooling effect.
Disadvantage: The structure of the PN generated by the heat through the sapphire substrate, the sapphire has a low thermal conductivity and long heat transfer path, so the structure of the chip thermal resistance, heat is not easy to send out.
Second major factor: packaging materials
LED packaging materials are divided into thermal interface materials and substrate materials two species.
1, thermal interface materials
Current LED packaging commonly used thermal interface materials have heat conduction adhesive and conductive silver glue.
(a) Thermal conductive adhesive
The main component of the commonly used heat conductive adhesive is epoxy resin, so its thermal conductivity is small, thermal conductivity is poor, thermal resistance is big.
Advantages: Thermal conductive adhesive has the characteristics of insulation, heat conduction, shockproof, easy installation, simple process and so on.
Disadvantage: Due to the low thermal conductivity, it can only be applied to the thermal requirements of the LED packaging devices.
(b) Conductive silver glue
Conductive silver Glue is a geas, sic conductive substrate led, with the back of the electrode of red, yellow, yellow-green chip led seal decoration or glue to prepare the key packaging materials in the process. Advantages: With fixed bonding chip, conductive and heat conduction, heat transfer function, and the LED device heat dissipation, light reflection, VF characteristics, etc. have an important impact.As a kind of thermal interface material, the conductive silver glue is widely used in the LED industry.
2. Base board material LED packaging device of a certain heat dissipation path from the LED chip to the bonding layer to the internal heat sink to the thermal substrate finally to the external environment, we can see the importance of heat dissipation substrate to the LED package, so the heat dissipation substrate must have the following characteristics: conductivity heat, insulation, stability, flatness and high strength.