In 2012, the LED industry entered its third growth cycle: General lighting. This new phase was markedly different from the second phase (TV backlighting) as it required LEDs to match the lumen output of traditional incandescent light bulbs. To create enough light to meet the requirements of the general lighting market LEDs had to be considerably higher powered.
Although LEDs are far more efficient then incandescent lamps they still only convert around 40% of the power put in to visible light. The rest is converted to heat – and needs removing as efficiently as possible.
LEDs need to be packaged to both protect them from the environment and provide the electrical connections needed to power them. There are several approaches to LED packaging with most High-Power LEDs (HP LEDs) being packaged individually so they can be surface mounted.
HP LEDs are packaged onto thermally conductive substrates which enable the intense heat of the LED to be conducted away from the LED die to ensure the junction temperature is kept within a safe regime. The substrates need to be circuitised on both the top and the bottom sides with interconnects between them to provide power to the LED die. This limits the material that can be used to a dielectric – generally to ceramics such as aluminium nitride and alumina, although silicon and other materials are used by some LED manufactures.
The restriction of using either aluminium nitride or alumina presents a conundrum for LED manufacturers: aluminium nitride is a good conductor of heat, around 140-170W/mK for sintered substrates, whilst alumina is quite poor, around 25W/mk. But alumina is far, far cheaper – aluminium nitride is around six times more expensive than alumina.
Up until now there have been very few alternatives which offer a similar thermal performance that fit standard processing. Many of the more esoteric materials and cooling solutions need specialist handling or other technology to complete the system. This has meant a sacrifice of either cost, performance or availability.
Now Nanotherm offers a new approach, Nanotherm DM (Direct Metalized). Nanoceramic substrates provide a similar thermal profile to aluminium nitride but at a far more compelling price/performance ratio. Copper circuits are simply sputtered onto a super-thin dielectric of nano-crystalline alumina on an aluminium foil or plate.
As the aluminium can be drilled before the nanoceramic layer is formed it means that electrically isolated interconnects can be created to connect the top and bottom circuits.
This game changing development gives LED manufacturers a material with the thermal and dielectric properties of aluminium nitride but with the manufacturability and robustness of a metal core PCB (MCPCB). Replacing ceramic substrates with an advanced sandwich of copper, Nanoceramic and aluminium not only offers a cost advantage; the material can also be significantly thinner. As it does not suffer from the brittleness that plagues conventional sintered ceramic substrates production yields are far higher and new methods of mounting, like bolts and direct water cooling are possible.
If you’d like details of how Nanotherm DM can meet your LED packaging requirements please call us on +44 (0)1440 765 520 or send us an email.