Identifying an unknown component means working from three clues: the top marking, the package outline, and the context on the board. This guide covers how to turn those into a manufacturer part number you can actually order.
Reading top markings
- Manufacturer logo or prefix identifies the maker; the same die is often second-sourced under different prefixes.
- The device code is frequently truncated on small packages — SOT-23 and smaller use abbreviated marking codes that must be looked up in the manufacturer's marking table.
- Date and lot codes are usually a four-digit YYWW or a manufacturer-specific lot string, not part of the orderable number.
- Suffixes carry the detail that matters when ordering: package, temperature grade, tape-and-reel vs tube, and lead finish.
Package outlines
Package identification narrows the candidate list fast: SOT, SOIC, QFN, QFP, BGA, DFN and through-hole outlines each map to a limited set of device families. Measure pitch and body size before assuming a package name.
Verifying authenticity
Compare markings against the manufacturer's published marking format, check that the date code is plausible for the device's production life, inspect for resurfacing or laser re-marking, and require documented traceability on open-market material.
About Gateway America and StockConnect
Gateway America is an ISO 9001:2015 certified, ERAI-member independent distributor of electronic components based in Tampa, Florida, shipping worldwide. StockConnect is Gateway America's free inventory platform, where suppliers list excess stock at no cost and buyers search that stock alongside franchise and OEM excess availability.