The latest experimental report shows that with a 100W integrated module, the module with pure copper is at a temperature of 75 degrees Celsius, and the module temperature of the diamond-copper composite is only 65 degrees Celsius. However, the coefficient of thermal expansion of copper (about 19) is much larger than the coefficient of thermal expansion of the sapphire substrate (about 5). Therefore, the use of copper as a chip thermal carrier in the harsh environment, there is a risk of chip chipping. The chip size is limited. Nowadays, diamond-copper composite sheets have been developed in China. The thermal conductivity is higher than that of pure copper, and the thermal expansion coefficient is lower than that of copper. It is expected that after mass production, the price can be accepted by manufacturers that produce high-power LED chip integrated blocks.
If the LED chip is not directly bonded to the circuit substrate by COB, a material with fast heat conduction is used as an intermediate medium for connecting the heat sink fins. Copper is a material that is only slightly inferior to silver in metal, and its price is lower, so copper is currently the most common thermal transfer material for high-power LED chips. The improvement of the thermal conductive copper sheet---using the diamond-copper composite material can effectively help the LED chip to dissipate heat. Below is a thermal decomposition of a high power LED luminaire using this technology.
In addition to structural simplicity, high-power LED luminaires integrate the following technologies:
High-efficiency light source conversion enables high-power LED lamps to improve light efficiency and reduce heat consumption. The same power consumption can have higher brightness; if the brightness is equal, it is equal to the heat loss. This is naturally good for LED chips that are afraid of heat. However, since the energy that is actually converted into light energy to emit the illuminant is only about 30%, most of the energy remains in the form of heat on the LED chip, so heat dissipation is still an Achilles heel of LED lamps.
(1) The precision matching technology and the thermal deformation modulus matching technology between different thermal conductive materials make the contact tight and the thermal resistance low; the high-efficiency thermal conductive material is used to reduce the thermal resistance of the contact surface.
(2) The integrated heat dissipation structure of the radiator and the lamp housing, and the single-chip structure, the lamp is completely exposed in the ambient air, and no regenerative cavity exists.
(3) The heat sink of the rare earth alloy material has high thermal conductivity and low thermal resistance. The structure of the rare earth alloy uniform temperature plate makes the heat dissipation uniform and has no high temperature region.
(4) Using aerodynamics and thermodynamic principles to design a perforated three-dimensional grid-like heat sink to form a â€œchimney-typeâ€ heat dissipation method to accelerate air convection circulation, while the through-hole structure allows dust to be attached without any contact, ensuring direct contact between the heat sink and the air. Area; nano-thermal radiation coating increases the thermal radiation capability of the luminaire.
The substrate material and solid crystal mode of the LED chip itself are becoming more and more efficient and heat conduction:
(1) The silicon carbide substrate is the current LED chip substrate with the highest thermal conductivity. The 40x40mil chip can withstand a maximum current of 1000MA. As long as the subsequent heat dissipation does not have this rated 1W power chip, there is no burning concern with 3W. .
(2) Recently, high-power LED chips from Japan, Korea, and Taiwan have also been added with a layer of metal plating on the sapphire substrate. This can also be replaced by silver paste to solidify the crystal. After the silver paste is cured, the thermal conductivity is close to that of pure silver, which is higher than the thermal conductivity of the silver paste. The chip of the traditional sapphire substrate, which does not show weakness, has developed a method of flip chip mounting chip. The two electrodes on the surface are turned to the bottom surface and directly soldered to the metal heat conductive substrate with silver paste. This heat transfer is more straightforward than the conventional use of thermally conductive silver paste.
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