What is the "article" on the heat dissipation structure that needs to improve the life of white LEDs?

In the past, in order to profit from the full white LED beam, the LED industry has developed large-size LED chips in an attempt to achieve the desired goal. However, when the power applied by the white LED continues to exceed 1 W, the beam will decrease and the luminous efficiency will decrease relatively. ~30%, in other words, if the brightness of white LEDs is several times larger than that of traditional LEDs, and the power consumption characteristics are expected to surpass fluorescent lamps, it is necessary to overcome the following four major problems, including suppressing temperature rise, ensuring service life, and improving illumination. Efficiency, and luminescence characteristics are equalized.

The specific method for temperature rise is to reduce the thermal impedance of the package; the specific method for maintaining the service life of the LED is to improve the shape of the chip and use a small chip; the specific method for improving the luminous efficiency of the LED is to improve the chip structure and use a small chip; The specific method is an improved packaging method for LEDs, and these methods have been developed one after another.

Solving the heat dissipation problem of the package is the fundamental method

As the increase of power will cause the thermal impedance of the package to drop to below 10K/W, foreign companies have developed high-temperature resistant white LEDs to try to improve the above problems. However, the heat of high-power LEDs is actually higher than that of low-power LEDs. More than ten times, and the temperature rise will also cause the luminous efficiency to drop sharply. Even if the packaging technology allows high heat, the bonding temperature of the LED chip may exceed the allowable value. Finally, the operator finally realized that solving the heat dissipation problem of the package is the fundamental method.

The service life of LEDs, such as the use of silicon packaging materials and ceramic packaging materials, can increase the lifetime of LEDs by a single digit, especially the white LED's emission spectrum contains short wavelengths of light below 450nm, traditional epoxy packaging The material is easily destroyed by short-wavelength light, and the large amount of high-power white LED accelerates the deterioration of the packaging material. According to the test results of the industry, the continuous lighting is less than 10,000 hours, and the brightness of the high-power white LED has been reduced by more than half. The basic requirements for long life of lighting sources.

Regarding the luminous efficiency of the LED, the chip structure and the package structure can be improved to the same level as the low-power white LED. The main reason is that when the current density is increased by more than 2 times, it is not easy to extract light from a large chip, but the result is luminous efficiency. It is not as good as the low-power white LED. If the electrode structure of the chip is improved, the above-mentioned light extraction problem can be solved theoretically.

Try to reduce thermal impedance and improve heat dissipation

Regarding the uniformity of the luminescent characteristics, it is generally considered that the above-mentioned problems should be overcome as long as the uniformity of the phosphor material concentration of the white LED and the fabrication technique of the phosphor are improved. While increasing the applied power as described above, it is necessary to reduce the thermal impedance and improve the heat dissipation problem. The specific contents are: reducing the thermal impedance of the chip to the package, suppressing the thermal impedance of the package to the printed circuit board, and improving the heat dissipation of the chip.

In order to reduce the thermal impedance, many foreign LED manufacturers set the LED chips on the surface of the heat sink made of copper and ceramic materials, and then connect the heat-dissipating wires on the printed circuit board to the cooling fan by soldering. Forced air-cooled fins, according to the results of the German OSRAM Opto Semiconductors Gmb experiment, the thermal impedance of the LED chip to the solder joint of the above structure can be reduced by 9K/W, which is about 1/6 of the conventional LED, and the packaged LED applies 2W. When the power is applied, the bonding temperature of the LED chip is 18K higher than the solder joint. Even if the temperature of the printed circuit board rises to 500C, the bonding temperature is only about 700C at most. When the thermal impedance is lowered, the bonding temperature of the LED chip will be lower. Under the influence of the temperature of the printed circuit board, it is necessary to reduce the temperature of the LED chip, in other words, reduce the thermal impedance of the LED chip to the solder joint, which can effectively reduce the burden of cooling the LED chip. Conversely, even if the white LED has a structure that suppresses the thermal impedance, if the heat cannot be conducted from the package to the printed circuit board, the luminous efficiency of the LED will rise sharply as a result of the rise in the temperature of the LED. Therefore, Matsushita Electric develops a printed circuit board and package integration technology. The company encapsulates a 1mm square blue LED in a flip chip package on a ceramic substrate, and then pastes the ceramic substrate on the surface of the copper printed circuit board. According to Panasonic, the thermal impedance of the module including the printed circuit board is about 15K/W. about.

Introduction

SCOTECH manufactures a full range of cast resin dry type transformers ,they are designed primary as an MV insulation system, cast resin technology provides excellent insulation and environmental protection, this together with the foil winding technology inside the resin offers the ultimate Dry Type Transformer in terms of dielectric performance and short circuit withstand and ensures long term reliability for both distribution and special applications. Cast resin transformers can be supplied with either aluminum or copper windings together with possibility of class F or class H resin system.

 

Advantages

Fire resistant /Self-extinguishing(F1)

Environmental class(E2) and climatic class (C2)

From IP00-IP56 enclosure with AN, AF, ANAF or AFWF cooling

Free maintenance

Environmental friendly ,>90% of material recyclable

 

Scope of supply

Voltage level: up to 35KV

Rating level: up to 20MVA

 

Standards

SCOTECH`s cast resin dry type transformers are designed and manufactured in accordance with all major international standards (IEC, ANSI, UL, CSA etc.) 

 

Why SCOTECH

Long history- Focus on transformer manufacturing since 1934.

Technical support – 134 engineers stand by for you 24/7.

Manufacturing-advanced production and testing equipment, strict QA system.

Perfect service-The complete customer service package (from quotation to energization).


Cast Resin Dry Type Transformer

Dry Transformer,Cast Resin Transformer,Resin Encapsulated Transformer,Cast Resin Dry Type Transformer

Jiangshan Scotech Electrical Co.,Ltd , https://www.scotech.com