An LED lamp assembly reportedly “flickered”, meaning there was likely an intermittent high resistance in the LED circuit.

LED lamp 1

Here are summaries of the destructive physical analysis of three suspect LEDs.

LED lamp 2

LED lamp 3

LED lamp 4

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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