As demand for LED (light emitting diode) luminaries continues to grow, new thermal management technologies are allowing manufacturers to produce LEDs that have higher light output and longer lifespan. led street light Manufacturer offer many advantages including low energy consumption, long service life (bulbs can last up to 40,000 hours or more), and environmental safety (they contain no mercury). The disadvantages of LEDs, such as higher prices than incandescent or fluorescent lighting, will dissipate as new manufacturing techniques make LEDs less expensive to produce and better able to handle heat fluctuations.
. Thermal management is one of the most important aspects of successful LED systems design, according to the US Department of Energy’s Office of Energy Efficiency and Renewable Energy LEDs convert only 20- to 30-percent of their electric power into visible light; the remainder is converted to heat that must be conducted from the LED die to the underlying circuit board and heat sinks. Excess heat can reduce LED light output and shorten lifespan. Therefore, managing thermal output to dissipate heat is crucial to maximizing the LED’s performance potential.
A Thermal Substrate Alternative
Currently, for high power / high brightness applications, the LED package or module is soldered to a metal-core printed circuit board (MCPCB), thermally enhanced PCB or a ceramic substrate, which is then bonded to a heat sink. Although this configuration is used widely in the LED industry, it does not offer the best method for managing heat conductivity and can be expensive to produce.
MCPCBs and thermally enhanced PCBs offer good thermal performance but have limited design flexibility and can become expensive when high thermal performance is required due to additional costs for machining thermal vias and the high cost of expensive thermally conductive dielectric materials. Ceramic substrates are made from lower thermally conductive, but cheaper ceramics, such as alumina, or higher thermally conductive but very expensive ceramics like aluminum nitride. Overall, ceramic substrates are relatively more expensive than MCPCBs and thermally enhanced PCB substrates.
As an alternative to the substrates discussed above, LED manufacturers are testing the concept of building circuits directly on aluminum substrates, which offer excellent thermal conductivity. Although the LED industry is interested in using aluminum due to its advantages, LED circuits built on aluminum require an insulation layer on the substrate. Now, advances in thick-film technology are allowing the LED industry to reap the benefits of using aluminum substrates.
IAMS, an Insulated Aluminum Material Systems developed by Heraeus Materials Technology, a supplier of products for thermal management applications, is a low-temperature firing (less than 600 ° C), thick-film insulating system that can be printed and fired on aluminum substrates . The IAMS material set consists of dielectric pastes, conductors, solder masks, and resistors. All the materials are compatible with 3000, 4000, 5000 and 6000 series aluminum substrates.
IAMS Advantages
“IAMS is designed as an insulation system for aluminum substrates,” said Mitsuru Kondo, Global LED Project Manager for the Thick Film Materials Division of Heraeus. “Aluminum can not handle temperature higher than 660 ° C, and standard thick-film products are ceramic- based and must be fired at very high temperatures of 800 ° C to 900 ° C.
“Because the IAMS pastes can be fired at less than 600 ° C, the system is compatible with aluminum processing conditions,” Kondo explained. “Also, IAMS ‘unique glass system minimizes bowing on aluminum while providing high dielectric breakdown strength and excellent thermal conductivity . ”
Most thick-film pastes have a CTE (Coefficient of Thermal Expansion) adjusted for use on high- temperature, low-CTE ceramic substrates. However, if you are using aluminum substrates, which have a very high CTE, and a paste designed for ceramics , the substrate will “bow” due to the differences in CTE. The CTE on IAMS is designed to match the CTE of the aluminum, minimizing any bowing.
Making modifications to the led street lighting fixture design is simple with IAMS. “Thick-film technology allows the LED circuit design to be screen printed directly onto the aluminum substrate,” noted Kondo. “The screen pattern can be easily changed to accommodate circuit design changes by simply changing the screen and reprinting. “This flexibility can be advantageous during prototyping and design stages.
In addition, because the printing process used to deposit the IAMS pastes is an additive process with selective deposition capability, costs are low. The insulating pastes are deposited only where the conductive circuit is located and, with the proper design, thermal vias are easily connected directly to the high thermal conductivity aluminum. There is minimal material waste during the circuit manufacturing compared to etched MCPCBs and thermally enhanced PCBs where sheets of copper are chemically etched to create the circuit. With the IAMS system, the conductor paste is deposited only where the circuit needs to be formed.
IAMS technology also allows the customer to use only one insulating paste. While other thick-film technologies require two different types of glass pastes for each insulation layer, only one paste is needed when using IAMS. Finally, all IAMS pastes meet RoHS requirements.
