Heraeus: best of the thick film technology of high power LED

With LED (light emitting diode) lighting demand continues to grow, new cooling technology to enable the manufacturer to light emitting diode LED light output production larger and longer life. LED offers many advantages, including low power consumption, long service life (can be used for 40000 hours or longer bulbs) (excluding mercury) and environmental protection. With the advent of new manufacturing technologies to reduce LED production costs and enhance its ability to heat, the shortcomings of LED (such as the price is higher than incandescent or fluorescent) will gradually disappear.

According to the information provided by the Department of energy efficiency and renewable energy, the heat dissipation is one of the most important factors in the successful design of LED system. Led only 20% to 30% of the electrical energy into visible light, the rest must be converted into heat from the LED chip into the circuit board and the heat sink. Excess heat will reduce the LED light output, shorten its life. Therefore, the improvement of heat transfer efficiency is very important for optimizing the performance potential of LED.

With the replacement radiating substrate

At present, for high power / high brightness uses LED substrate or module is welded to a metal base printed circuit board (MCPCB), enhanced cooling type printed circuit board or a ceramic substrate, the substrate is then received sticky heat sink. Although this configuration in the LED industry are widely used, but it is not the best cooling method, and the manufacturing cost can be very high.

MCPCB and enhanced cooling type printed circuit board has good heat dissipation performance, but the design flexibility is limited, and if you need to improve the radiating efficiency, cost is high, the reason is the need to spend extra cooling holes processing cost and expensive cost of thermal insulation materials. Ceramic substrates can be used in the ceramic with low thermal conductivity and low price (such as aluminum oxide ceramic), but also can be used with high thermal conductivity, but the price is very expensive. All in all, the cost of ceramic substrate is higher than that of MCPCB and enhanced heat dissipation PCB substrate.

In order to replace the substrate, LED manufacturers are testing the method of making the circuit directly on the aluminum substrate, because this method can provide excellent thermal conductivity. Because of its advantages, the LED industry is interested in the use of aluminum, but the production of aluminum substrate on the LED circuit requires insulation. Now, the development of thick film technology allows the LED industry access to the benefits of using aluminum substrates.

With the development of thick film material system of aluminum plate cooling slurry technology company Heraeus materials suppliers (IAMS) is a kind of low temperature sintering (lower than 600 DEG C) thick film insulation system, can be printed and sintered in the aluminum substrate. The IAMS material system comprises a dielectric paste, a silver conductive paste, a glass protective layer and a resistance paste. These materials are suitable for 3000, 4000, 5000 and 6000 series aluminum substrate.

The advantages of IAMS

Heraeus thick film material of global LED Project Manager Kondo Mitsu said: "IAMS is for aluminum plate insulation system design. Aluminum can not withstand temperatures above 660 degrees Celsius, the standard thick film products based on ceramics, must be sintered at high temperatures, temperatures up to 800 degrees Celsius to 900 degrees.

Kondo Mitsu explained: "because the IAMS slurry can be sintered at temperatures below 600 degrees Celsius, the system is suitable for aluminum processing conditions. In addition, the unique IAMS glass system can reduce the deformation of the aluminum warpage, but also can provide a high Break down voltage and excellent thermal conductivity. "

The thermal expansion coefficient (CTE) of most thick film paste is adjusted to the ceramic substrate which can be used for high temperature and low expansion coefficient. However, if the use of a high coefficient of thermal expansion of aluminum substrate and ceramic design of the slurry, the substrate will be due to the difference in thermal expansion coefficient of "deformation and warpage". According to the design, the thermal expansion coefficient of IAMS is matched with the coefficient of thermal expansion of aluminum, which can minimize the warpage.

Through the use of IAMS, it is easy to modify the design of the LED substrate. Mr Kondo Mitsu said: "through thick film technology, the LED circuit pattern can be printed directly onto the aluminum substrate. Screen design is easy to modify according to the changes in the circuit design, just modify the screen and then re printed. "This flexibility is helpful in making prototypes and design phases.

In addition, due to the printing process of printing IAMS slurry used in the process is to choose the printing area of the process, so the cost is low. The insulation slurry is printed only in the position of the conductive circuit. As long as the design is appropriate, the heat sink is easy to connect directly to the high thermal conductivity of aluminum. Compared with the etched MCPCB and the enhanced heat dissipation printed circuit board, this method wastes very little material (the first two plates are made of copper by chemical etching method). When the IAMS system is used, the conductor paste is printed only in the position where the circuit needs to be formed.

In addition, the use of IAMS technology, customers only need to use an insulation slurry. Other thick film techniques require the use of two different types of glass paste for each insulation. In addition, all IAMS slurry are in accordance with the provisions of RoHS.

Mature technology

The key to the performance of the LED is the effective heat dissipation; keeping the LED low temperature helps to increase the brightness and extend the life. In order to prove that IAMS can provide the cooling characteristics of LED manufacturer, Heraeus company invited third party tested. VTT technology research center of Finland Oulu company Heraeus please makes a comparative study on MCPCB and IAMS.

VTT researcher Aila Sitomaniemi said: "we compared the use of MCPCB