Buying obsolete parts without getting burned: a buyer's checklist

The obsolete component market rewards patience and punishes shortcuts. A part that looks right in a photograph can still fail incoming inspection, and a broker that quotes a rock-bottom price on a hard-to-find MCU is almost always telling you something about the parts you're about to receive.

This is the checklist we run on every incoming lot before it gets a Hybrid label. Use it — or something like it — before you wire money for anything discontinued.

1. Match the date code to the story

Every obsolete part has a plausible date-code window. A 74LS-series logic chip in a JEDEC tube with a 1998 date code is normal. The same part in a 2019 tube is either factory-fresh new-old-stock (rare, high-value) or remarked (worthless and probably counterfeit). If the date code doesn't fit the part's production history, ask the seller to explain it before you go further.

2. Look at the packaging, not just the part

Original manufacturer packaging tells you almost as much as the part itself. What we check on every incoming lot:

• Reel and label integrity — factory-sealed reels with intact humidity-indicator cards and matching lot codes on both reel and box.
• Tube caps and rails — original tube caps, no mismatched colors or replacement plugs.
• Tray and JEDEC matrix labels — matrix trays with legible date/lot markings, not photocopies over old labels.
• Moisture bags — for MSL-rated parts, an intact bag with an in-date HIC card and a legible bake-date sticker.

Repackaged parts are not automatically bad — sometimes an OEM breaks a reel to consume half of it — but repackaging always deserves a conversation.

3. Know the storage history

An obsolete part is only as good as where it lived for the last twenty years. The questions to ask:

• Where has this lot been stored, and for how long?
• Was it in climate-controlled conditions or a warehouse in Guadalajara with no HVAC?
• For MSL 3+ parts, was the moisture bag opened? When was it last baked?
• Has the lot changed hands, and how many times?

Every additional intermediary between the OEM stockroom and your dock adds a chance to break the humidity seal, mix in a suspicious reel, or lose the traceability paperwork.

4. Ask for the three documents

Before we buy an obsolete lot, we want to see three pieces of paper:

1. Certificate of Conformance (C of C) from the current holder, referencing the manufacturer lot code.
2. A traceability chain — invoices or transfer documents showing how the parts moved from OEM overstock (or authorized channel) to the current seller. Two hops is normal, five is a red flag.
3. Inspection or test report if available — real, dated, and signed. A one-line "visually inspected, appears functional" note doesn't count.

If a seller can't produce any of the three, that isn't automatically fraud — a lot of legitimate excess stock has thin paperwork — but the price should reflect the risk you're taking on.

5. Run the counterfeit-detection basics

The most common counterfeit tell on obsolete semiconductors is a remarked top surface: sanded down, re-blacked, and re-lasered with a newer date code or different part number. What we look at:

• Surface uniformity — under a microscope, remarked parts show sanding scratches or coating pooling around pins.
• Marking depth and font — laser marking is crisp and consistent lot to lot. Ink marking that rubs off with acetone is a common failure.
• Lead condition — reflow tinning, uneven solder on gullwings, or tin whiskers on parts marked as new stock.
• X-ray die comparison — for high-value or safety-critical parts, a die X-ray against a known-good sample catches replacement dies and empty packages.

For MIL-spec and JAN parts destined for hi-reliability programs, we test to the applicable slash sheet or specification. Anything less isn't traceable.

6. Match the price to the risk

Obsolete-part prices span three or four orders of magnitude. When something is priced far below the working broker market, it usually means one of these things:

• The lot has questionable packaging or paperwork.
• The date code is outside the part's normal production window.
• The seller is trying to move stock before another buyer inspects it.

None of those are automatically deal-breakers — but they should all show up in the quote or in the conversation.

7. Buy from someone who owns the risk

The last question is the one that separates a two-year relationship from a one-shot transaction: who eats the loss if the parts fail incoming inspection? A real distributor will replace the lot or refund the money. A pure broker won't, and often can't.

When we buy an obsolete lot for our shelves, we take that risk ourselves — and that's why the checklist runs on every incoming shipment before it gets a Hybrid label on the outside of the box.

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