An LED lamp assembly reportedly “flickered”, meaning there was likely an intermittent high resistance in the LED circuit.
Here are summaries of the destructive physical analysis of three suspect LEDs.
The analysis results for all three samples were similar. Thermal-mechanical damage was found including (1) thermal decomposition of the lens material mid-span on the anode bond wire on Sample A & Sample C, (2) adhesive failure (separation) between the phosphor-filled-die-encapsulant and the cup on all samples, and (3) fracture of the phosphor-filled-die-encapsulant that intersected the cathode ball bond of Sample B. All of these observations are consistent with the thermal-mechanical effects of electrical overstress.
The client reported that the LEDs were being operated at 150% of the maximum forward current, which likely was the primary factor causing premature failure.
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