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LEDs that don’t comprise bonding wires?

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treez

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Hello,
We have LED luminaires which have long series strings of LEDs. Therefore, if one LED fails, then the entire bank goes out. Bond wire breakage is a major cause of LED failure. As such, do you know of any types of Surface Mount LEDs which don’t have bond wires?
Our LEDs in this product dissipate from about 1 to 2W each.
We mount them on MCPCB which sits on an earthed heatsink.
 

I don't know of any but a trick to keep the remainder on is to parallel them with a Zener diode that has slightly higher than LED Vf. If a LED goes open circuit the Zener keeps the remainder working. I has an extra use of giving reverse voltage protection.

Brian.
 
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Somebody makes an IC that detects a series LED that is open and bypasses it.
 
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Thanks, the open led protectors of onsemi are great, unfortunately we dont have room for them. And our technology is not so tolerant of the reduced vf that becomes of using them when a led fails.
 

I would insert a few more equal LEDs in series to the string to the point their luminosity still satisfies you and evaluate the new durability.

The manufacturer design may have pushed the LEDs current to the limit, a common bad practice for reliability. At 70% or even less ratings they may still shine satisfactorily and last forever. The brightness decrease from current is somewhat compensated by the extra LEDs added.

Or rethink the power supply.
 
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Externet said:
I would insert a few more equal LEDs in series to the string to the point their luminosity still satisfies you and evaluate the new durability. .
Click to expand...

Often the simplest solution is the most elegant. Roughly speaking, a 10% reduction in current with roughly increase the life expectancy by a factor of 2. Also the sensitivity to high voltage spikes will be reduced somewhat. I suspect the major cause of the premature deaths are unpredictable voltage spikes.
 
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Apart from the question if bond wire breakage is actually major LED failure cause with those LEDs that have bond wires, you seem to have missed the fact that many recent LEDs are using bond wire less flip chips, e.g. the chip scale WICOP LEDs you are addressing in a parallel thread. Look at the microsection photo in the application note.
 
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Apart from the question if bond wire breakage is actually major LED failure cause with those LEDs that have bond wires, you seem to have missed the fact that many recent LEDs are using bond wire less flip chips, e.g. the chip scale WICOP LEDs you are addressing in a parallel thread. Look at the microsection photo in the application note.
Click to expand...

http://acrich.tw/_upload/Goods_Spec/Wicop_Application_Note_EN_Rev4.3(1).pdf
…thanks, but I didn’t see where they say it doesn’t have bond wires (WICOP2 Z8 Y19 LED).
You’d think they’d brag about that because bond wire failure is the biggest failure cause in leds
 

There are numerous articles online about Wicop led construction. They are chip and phosphor only. I'm not able to give a direct link but if you search " do wicop leds have bond wires " you will find this information.

- - - Updated - - -

I did not see anything in app note either that suggest that there are no bond wires. It's probably there, I just don't know what to look for.
 

Can't say what there advertising strategy is. I don't think you will be seeing billboards on the highway anytime soon though.
In most cases it takes a while before a product is widely accepted. Individuals can be leary of a product that is new and doesn't have a proven track record established. Speaking for myself I seldom go out and buy the latest and greatest until I've received some positive feedback about the product. I would think some manufacturers would feel the same. The ones that can afford it would probably do extensive testing before they put there reputations at risk. I am not in that business so this is by no means and expert opinion. You would be better off getting the opinion of others that do have business experience.
 

Flip-chip LEDs may expose other failure mechanisms than classical packages. Reliability has to prove in real applications.

It's O.K. to wish for better performance of new product generations, but don't jump into conclusions.
 

...bond wire breakage is the single biggest led failure mode
Click to expand...

It is possible but unlikely. If it were so, it would have been easy to replace the bonding wire with a thicker gauge.

Going by the classical experience with junction transistors, the degradation of the diode junction may be the real cause of failure. I may be wrong but the junction is under significant thermal stress. As the junction anneals, performance degrades.

With my limited personal experience with domestic LED lamps, the electronics is the first point of failure.
 

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