High LED Dead-Light Rate: A 5-Root-Cause Checklist
In short: over 90% of batch dead-light failures can be traced to five links — die grade, bonding process, encapsulant temperature resistance, reflow profile, and burn-in screening. Working through this checklist section by section quickly pinpoints the responsible party.
Root-cause checklist
| # | Link | Typical problem | How to check |
|---|---|---|---|
| 1 | Die | B-grade / project-die leakage, ESD damage | Measure leakage when lit; request the wafer fab shipment certificate from the supplier |
| 2 | Bonding | Alloy wire cold joints, contaminated bonds | Dye penetration test; sample pull testing |
| 3 | Encapsulant | Insufficient temperature resistance of domestic compounds; cracking after reflow | Cross-section inspection; re-test after two reflow cycles |
| 4 | SMT process | Reflow peak exceeds encapsulant tolerance (typically 260°C/10s max) | Measure with a reflow profiler |
| 5 | Burn-in screening | No high-temperature burn-in at the factory; early failures shipped out | Request burn-in records and PPM failure-rate data |
Three hard requirements for buyers
- Failure rate: require a PPM-level (parts per million) commitment written into the contract;
- Reflow tolerance: at least two reflow cycles (simulating rework) with zero dead lights;
- Batch traceability: every batch traceable to die lot, bonding machine, and BIN rank.
※ Hongcheng Optoelectronics runs high-temperature burn-in and reliability sampling before shipment, with failure rates controlled at PPM level. All five processes (die bonding / wire bonding / encapsulation / sorting / burn-in) run on fully automatic ASM lines with full traceability.
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