Wireless bonded LEDs are more robustly designed than traditional LEDs. Wireless bonded LEDs offer superior heat dissipation and are more adverse to shock and vibration. The most striking benefit of bonded LEDs is that they are shadowless, resulting in more uniform, even light performance.
Enhanced heat dissipation
Compared to traditional LEDs, wireless bonded LEDs can withstand higher temperatures without compromising performance. The first reason for this is that wireless bonded LEDs have a greater surface area for heat dissipation. Whereas a standard LED die measures 12mil by 12mil, a wireless bonded LED die is larger, often about 10mil by 23mil.
At the same time, wireless bonded LEDs are more efficient at removing heat. In traditional LEDs, heat can travel down the 1mil wide wire bond. In wireless bonded LEDs heat is dissipated faster since the two contact pads are on the bottom and the chip is much closer to the PCB/heatsink.
Together, these two characteristics mean that heat has up to five times more surface space for dissipation in wireless bonded LEDs. Consequently, heat dissipation is up to 30 percent more efficient in wireless bonded LEDs than in traditional LEDs.
The enhanced shock and vibration resistance of wireless bonded LEDs compared to traditional LEDs stems from more durable design. Because the wire bond used in traditional LED is attached at two junctures, the ball bond and wedge bond, there is a greater opportunity for malfunction at these two sensitive points. It requires only 7 grams of force to sever the wire bond and create performance failure.
With wireless bonded LEDs however, the LED is bonded with a silver epoxy and cured to the die. The die itself is then attached to PCB pads. This approach leads to much more durable performance as it requires 25 to 30 grams of force to sever the connection.
This makes wireless bonded LEDs over three times more vibration and shock resistant than traditional LEDs.
Superior light performance
Finally, wireless bonded LEDs provide superior light performance when compared with traditional LED technology. Higher light output is achieved in a more compact space and the light performance is unencumbered by shadows or other obstacles to consistent performance.
The larger die used in wireless bonded LEDs provides higher light output – from 8 percent to 10 percent brighter in intensity. At the same time, real estate savings are possible as high intensity light can be achieved using a single wireless bonded LED rather than a larger array of traditional LEDs.
For example, to achieve the same 9W level of brightness, it would be possible to use a single module wireless bonded LED with a footprint of 41.5mm instead of an array of traditional LEDs with a footprint of over 65mm.
In addition to providing greater brightness in reduced space, wireless bonded LEDs provide more consistent, evenly distributed light performance. Traditional LED chips emit light from the side of the LED. That light is then bounced through a reflector over the wire bond which generates a shadow and can cause unevenness with light distribution. With a wireless bonded LED the chip can directly emit light from the top and the side with no wire bond casting shadows or creating uneven light distribution.
Several drawbacks of this article:
1. Misnomer of calling flipchip as wireless! The latter term is deeply entrenched in mobile communications as is the former term in the chip interconnect industry!! You need to call a spade a spade...
2. Preaching to the choir! Most readers of EE Times are already familiar to flip chip which has been around for decades now. What I would have liked to see is a cross-section of an actual device and not cartoons.
3. Better, quantified data to backup claims made -the authors makes comments about LED arrays but does not show any data to backup. Irrespective of the interconnect method, thermal cross talk between LEDs joined at the substrate is always going to be a problem and I don't see this proven by data.
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