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How to verify date codes on chips — and what they can and cannot tell you
The date code is the easiest data point to get and the most commonly misread: how to read it, how to verify it, and when it proves nothing.
Buying surplus chips, the date code is the easiest data point to get — and the most commonly misread.
What a date code is
Most brands use a 4-digit YYWW format: two digits for the year, two for the week — 2340 means week 40 of 2023. Some brands differ: TI typically year+week, ST mixes fab site into the lot code, Microchip traceability codes need their official lookup. Check the brand’s format before you read anything into the digits.
How to check
One: compare markings. Parts from one reel or tray should carry the same or adjacent date codes; a reel mixing codes two years apart has been consolidated by someone.
Two: compare packaging. The label’s date, quantity and lot code should match the markings; a crisp new label on a yellowed tray deserves a question.
Three: spot-check with the manufacturer or an authorised channel. Most major brands can verify a lot code, or at least confirm the fab line.
What it cannot tell you
A recent date code does not mean the part is genuine: re-marked parts get fresh date codes precisely because buyers look for them. An old date code does not mean unusable: properly stored passives and most logic parts work fine beyond the nominal “2-year shelf life” — moisture sensitivity level and solderability are the things worth testing, and both are testable.
What you may ask for before paying
A line-item manifest should include a date-code column; lot photos should show markings and labels legibly; and pre-payment inspection — yourself, an agent, or a third party such as SGS or BV — is a completely normal request in this trade. A seller who accepts no form of inspection is a bigger warning sign than any date code.