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In the manufacture of NAND flash (to my understanding):

  1. Wafer is produced
  2. Dies are probed for testing
  3. Dies that pass testing are configured as Tier-1 chips, then packaged.
  4. Dies that fail Tier-1 testing are modified (if possible) so they have reduced capacity, for example a 128 gigabit die has defective sections configured as unavailable yielding a die with 64 gigabit capacity.
  5. Successfully downgraded dies are packaged (for example in TSOP-48) but not marked with the manufacturer logo, part number or serial number.
  6. Finished ICs are sold to manufacturers for use in inexpensive USB Flash Drives.

My question: What is the proper term for these downgraded NAND Flash ICs?

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  • \$\begingroup\$ Well, the process is called binning, not sure if there is a name for the salvaged chips though. \$\endgroup\$ – alex.forencich Feb 29 '16 at 20:56
  • \$\begingroup\$ #5 sounds extremely suspicious to me. Selling a reduced-capacity die is believable, but not putting a logo or a part number on it? Sounds like counterfeit to me. \$\endgroup\$ – Adam Haun Feb 29 '16 at 21:17
  • \$\begingroup\$ IMO, the proper term is "trash". If parts of the array are already failing, their lifetime was way to the low end of the distribution. Since other parts of the same die resulted from the same production processes, it's likely that they have greatly reduced lifetime as well. For arithmetic circuits, degradation due to messed up dopant concentrations might mean the circuit needs higher voltages or can support lower clock speeds, but runs a normal life with those modifications. Flash circuits might merely have reduced speed (acceptable), but reduced lifetime seems very problematic. \$\endgroup\$ – Ben Voigt Feb 29 '16 at 22:56
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The process is called "binning". Production line binning is how things get graded. #1, #2, and #3 are correct, but I've never had experience with #4 on. Also, I don't believe this applies to NAND. In the case NAND, you expect only about 100k writes per gate (or I do anyway), so you move pages as the writes fail.

You can probably find information about this in a "design for test" course that's floating around.

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  • \$\begingroup\$ Helpful, thank-you: I used your keywords and found a document describing "Grade B" for NAND Flash. No manufacturer markings, smaller capacity, but still functional as the specific chip. \$\endgroup\$ – K-Thx-Bye Feb 29 '16 at 21:16

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