Why the Freeze Belongs at EVT
Traceability is usually filed under mass production, but the real cost lands earlier. If EVT samples carry no unique identity and no frozen BOM, none of the performance or reliability data collected afterwards can be attributed to specific components. Across 30 formal models, 10 series and 99 capacity SKU combinations, a single unrecorded component substitution reduces the comparability of the affected data to zero. Model names were fixed on 2026-07-22, and changes to capacity, NAND, controller, firmware and BOM are handled only through SKU, PN, Revision and ECN control, which makes the PN-to-BOM binding a controlled item from product definition onward.
Five Layers That Must Be Bound
- Controller: model, revision and firmware baseline;
- NAND: vendor part number, wafer lot and screening grade;
- DRAM: capacity configuration and die source;
- PCB: revision, stack-up and critical passives;
- Firmware: controlled release version and its parameter table.
NAND lot is the layer most often overlooked. Different lots of the same part number can show systematic differences in initial bit error rate distribution and program time, and firmware read-retry and LDPC parameters are tuned to lot characteristics — mixing lots shows up directly in long-duration burn-in failure rates.
Lot Consistency Comes from Distributions, Not Spot Checks
Consistency cannot be argued from sampled means falling inside spec; it requires comparing distributions. Each lot is measured under identical conditions for sequential and random performance, power draw, power-loss-protection action time and thermal profile, then compared against the baseline lot for distribution shape and spread. Volume burn-in runs on the in-house JH-ZS101 intelligent test system, which handles 600 SATA SSDs or 480 NVMe SSDs per run, integrates five test processes including card initialisation and burn-in, and supports zoned temperature control and remote network power switching — throughput that makes full-lot rather than sampled data collection practical.
The End Use Is Failure Analysis
The system will ultimately prove itself in failure analysis. Faced with a failed drive later on, whether its controller lot, NAND wafer lot, PCB revision, installed firmware version and original burn-in data can be resolved quickly is what decides whether an individual failure can be told apart from a lot-wide issue or a firmware-version defect. With only a serial number and a test report, the analysis degenerates into guesswork. No real samples exist to exercise that path yet, which is exactly why every component substitution during EVT has to leave an ECN record — traceability data can only be built in advance, never reconstructed at the moment it is needed.