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This quote is from post number #49 of the above thread.But what we dont know is how they do ORT and how do they know how much margin exists in shearing the Anode connection with the ultrasonically cold-welded micron size gold wire. THIS IS THE MOST COMMON failure mode in LEDs. It can occur for many reasons. Some designs use dual wire bond. But all must survive the extreme thermal stress from different coefficients of material expansion not get "wounded" from shock, vibration, ESD, thermal shock, transient overpower etc etc.
…Thanks…and WOW!!!.....that is ground-breaking, and blows out of the water all the research in to finding ways of being abe to handle mains transients in order to get long-life.
By the way, do you have a paper on that?
We are now wanting to do long life outdoor street lighting.
If there is some issue with bond wires to LED substrate having to be ridiculously thin, and often, as you appear to suggest, it gets cut too thin due to machine tolerance, and that causes LED failure in the field, then there’s not much point in us investing more time in finding ways of surviving every possible mains transient that present itself to the street lights………since the bond wire issue that you speak of is going to give us failures even if we do the best ever transient protection?
Are you sure its the main cause of failure in LED lamps?
Is LED Bond wire failure the "dirty secret" of the LED lighting industry?
Pages 12 to 13 of the following document give details of Electrical Power System faults which can cause large mains overvoltages for periods of milliseconds to minutes. These would kill LED streetlights without doubt.
Thannkyou, i take it this is to protect the scope from possible insulation damage due to the fact that the little audio transformer isn't very well isolated?use an isolating transformer on the scope side if possible.
Thankyou for you #16 comment here, would I be wrong to infer that from this you believe that the vast majority of mains transients are very weak?. –As you know, it wouldn’t take much to turn the LED on in the schematic of post #15. So surely the majority of mains transients must be weak?, and probably most of them wouldn’t make it through the AC filter of most small <75W offline SMPS’s, let alone get to a TVS, say placed downstream of the rectifier bridge?The reason is simply the response time would be too slow to catch many of the spikes.
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