July 21, 2016: With each passing day, LED lighting is becoming popular and stronger. However, there are still some challenges that need to overcome. And, thermal challenge is one of the most vital among other challenges. LED lighting has to match the lumen output of conventional halogen and incandescent bulbs in order to fulfil the increasing demands of the market. The average high-brightness (HB) LED only converts about 45% of the energy put in to detectable photons, while the rest is merely heat.
Different LED packaging options
In order to overcome the thermal management challenge, manufacturers should pay attention to LED packaging which provides physical safety to the LED die and the process to fix the LED onto the luminaire. However, it also means the LED die is then in a preserved enclosure, which mostly averts heat loss by radiation and convection. The only solution to ward off the heat is by transmission from the back of the package.
This truth has resulted in the use of thermally conductive substrates to aid in reducing the thermal path between LED and heat sink. Hence, the ideal solution is a material that is thermally conductive as well as dielectric. The manufacturers of LED are continually pushing to expand solutions to decrease cost, by using more reasonable materials and removing procedures.
Effective packaging options for thermal mitigation in LEDs
There are generally two approaches to HB LED packaging. Firstly, manufacturers have the option to package a solitary big LED die, or bunch of die such as one red, one green, and one blue, into a machine that can be amassed with the help of surface-mount technology (SMT). Secondly, they can package numerous die directly onto what is fundamentally a printed-circuit board (PCB) – the chip-on-board (COB) approach.
Apparently, COB LEDs are a no-brainer. By mounting the uncovered LED die directly onto a PCB, instead of packaging the die before surface mounting them onto a PCB downstream, an entire procedure step gets eliminated which, clearly makes COB devices a more reasonable alternative.
HB LED, Ceramics & nonoceramics
A chief prerequisite for directional HB LED packaging is that both sides of the packaging substrate require to be circuitized, with copper tracks via the substrate, offering connection between the two sets of circuits. This requirement is significant since the packaging substrate will be mounted onto a luminaire circuit that need to give power to the die.
Ceramics are a good choice since they are capable of going through extremely high resolution direct-plated copper (DPC) circuitization processes. DPC is a preservative process where the copper tracks are sputtered onto the ceramic to put up the circuit.
At present, a third option has come to the limelight and that is nanoceramics. The nanoceramic materials are known to bring the best of aluminum and ceramic. It is manufactured with the patented high-voltage electrochemical-oxidation (ECO) procedure that converts the surface of aluminum into an aluminum oxide (Al2O3). Nanoceramic also beats the two problems that stop standard MCPCBs from being used.
Use cases for ceramics and nanoceramics
So what are the uses of ceramics and nanoceramics? Let’s have a look at the HB LED circumstances where different substrates would be deemed appropriate. There is single large-die packaged HB LED. Since the manufacturers can continue to drive up LED power, 1W packaged LEDs are now debatably in the mid-power camp. The chief factor when determining what substrate to use here will be based around power density. Where the package size is larger, the power density will fall as the quantity of heat that will need removing is permanent.
Then, there is multiple large die, where the manufacturers place several HB LED die into a single package to create an extremely powerful device. These can effortlessly push up to 10W. On the basis of the footprint, AlN or copper pedestal territory of such devices can be measured.
At the end of it all, it can rightly be said that thermal management of HB LEDs is completely not a case of one size fits all. Every design requires to be reviewed and materials chosen to match the needs and hence, the manufacturers need to act accordingly and choose the ideal packaging option for LED lighting.