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Electronics sourcing & BOM glossary

The vocabulary of electronics sourcing: the terms that decide how a bill of materials gets priced, risk-checked, and quoted. Each definition is written to stand on its own.

Supply chain AI: Artificial intelligence applied to supply-chain decisions: sourcing, pricing, risk, and inventory. In electronics, supply chain AI reads BOMs, RFQs, supplier replies, and market signals, then recommends sourcing paths, substitutes, and quotes instead of leaving the judgment to spreadsheets.
BOM agent: An AI agent that works a bill of materials end-to-end: it cleans and normalizes the BOM, checks lifecycle and EOL risk on every line, finds alternates, ranks supply options, and drafts the quote. A BOM agent acts on the BOM rather than just storing it, the way BOM management software does.
Bill of MaterialsBOM: The structured list of every component, quantity, and reference needed to build an electronic product. In sourcing, the BOM is the input a buyer prices, risk-checks, and quotes against.
Manufacturer Part NumberMPN: The unique identifier a component manufacturer assigns to a specific part. MPN normalization, the work of cleaning inconsistent, abbreviated, or mistyped MPNs into canonical numbers, is the first step in turning a messy BOM into sourceable data.
Approved Vendor ListAVL: The set of manufacturers or suppliers a company has qualified to supply a given part. AVL logic constrains which alternates and sources are allowed when a preferred part is unavailable.
Transistor-Transistor LogicTTL: A family of digital logic chips built from bipolar transistors, and the 5V (or 3.3V LVTTL) signaling levels they set. On a BOM, a line marked TTL points to a specific logic family and voltage, which constrains valid alternates. TTL is also used informally as shorthand for Total when it labels a quantity column.
Reference DesignatorRefDes: The label that ties a BOM line to its place on the board: R for resistors, C for capacitors, U for ICs, and so on (R1, C12, U3). Reference designators let a buyer count how many of each part a build needs and reconcile quantities against the schematic.
Do Not Populate / Do Not InstallDNP / DNI: A BOM annotation marking a component that is listed but intentionally left off the board for this build or variant. DNP lines carry a quantity of zero for purchasing, and mistaking one for a real demand line inflates the buy.
Date code / Lot code: Manufacturer markings that record when and in which batch a component was made. Date and lot codes drive traceability, shelf-life and moisture handling, and recall scope, and they separate fresh stock from aged inventory in the open market.
Restriction of Hazardous SubstancesRoHS: An EU directive that limits lead and other hazardous substances in electronics. A part must be RoHS-compliant to ship into most markets, so RoHS status is a hard filter when choosing alternates on a BOM.
REACH: An EU regulation governing the registration and restriction of chemical substances, including substances of very high concern (SVHC) in components. REACH sits alongside RoHS as a compliance gate every sourced part has to clear.
Moisture Sensitivity LevelMSL: A 1-to-6 rating (per J-STD-020) for how much atmospheric moisture a surface-mount component can absorb before it must be baked or reflowed within a set floor time. MSL decides how parts are packed, stored, and handled, and it affects which stock is usable.
Country of OriginCOO: The country where a component was manufactured. COO drives tariff and duty exposure, trade-compliance rules, and supply-risk decisions, so buyers reconcile it line by line rather than treat it as a shipping formality.
Minimum Package QuantityMPQ: The smallest sealed pack a distributor will break, such as a full reel or tray. MPQ differs from MOQ: even when a supplier will take a small order, packaging forces the quantity up to the next full MPQ, creating excess on a BOM that needs less.
End of LifeEOL: The point at which a manufacturer discontinues a component. Once a part is EOL, buyers must find approved alternates, place a last-time buy, or redesign. In 2025, 621,909 electronic parts went EOL (Z2Data).
Product Change NotificationPCN: A formal notice from a manufacturer that a part is changing or being discontinued. PCNs are the early warning system for obsolescence. But 52% of 2025 EOL events shipped with no PCN at all (Z2Data), so risk must be inferred, not just read.
Last-Time BuyLTB: A final purchase of a component before it goes obsolete, sized to cover forecasted demand over the remaining product lifetime plus a safety margin. Getting LTB quantity right balances obsolescence risk against inventory carrying cost.
Electronics Manufacturing ServicesEMS: Companies that manufacture electronic assemblies for other brands (contract manufacturing). EMS providers quote from customer BOMs and RFQs, making fast, accurate BOM sourcing central to their margin.
Original Equipment ManufacturerOEM: A company that designs and sells the end product under its own brand, often outsourcing assembly to an EMS. OEMs own the BOM and the approved-vendor decisions.
Request for QuoteRFQ: A buyer’s request for pricing and availability on a set of parts, usually a BOM. RFQ intake, turning inconsistent emails, spreadsheets, and PDFs into structured, sourceable records, is where most quoting time is lost.
Non-Cancellable, Non-ReturnableNCNR: Order terms under which a component cannot be cancelled or returned once placed. NCNR parts concentrate risk: a wrong quantity or a substituted part becomes a write-off rather than a return.
Minimum Order QuantityMOQ: The smallest quantity a supplier will sell of a part. MOQs drive excess inventory and complicate pricing when a BOM needs only a fraction of the MOQ.
Cross-reference / alternate part: A different manufacturer part that is form-, fit-, and function-equivalent to a specified component. Finding valid cross-references is how sourcing teams keep a build alive when the preferred part is out of stock, on long lead time, or EOL.
Should-cost modeling: Estimating what a component or assembly ought to cost based on materials, process, volume, and market conditions, rather than only on quoted price. Should-cost gives buyers a baseline to negotiate against and to flag over-priced quotes.
BOM scrubbing: Cleaning and validating a raw BOM so it can be priced and quoted accurately: normalizing MPNs and manufacturers, resolving quantities and alternates, and flagging lifecycle risk. Also called BOM cleanup or normalization.
Lead time: The time between placing an order for a component and receiving it. Long or volatile lead times force substitutions, last-time buys, and quote assumptions that decide whether a bid is profitable.
Bid / no-bid: The decision of whether to quote a given RFQ at all, weighing cost, availability, lifecycle risk, inventory fit, and margin. Disciplined bid/no-bid focuses effort on the opportunities most likely to win at an acceptable margin.
Complementary Metal-Oxide-SemiconductorCMOS: A logic family and process technology using paired p- and n-type MOSFETs, drawing almost no static power. On a BOM, CMOS and TTL parts differ in voltage thresholds and power draw, so a CMOS line is not a drop-in for a TTL one without checking logic levels.
Low-Voltage Differential SignalingLVDS: A high-speed signaling standard that carries data as the voltage difference across a wire pair, resisting noise at low power. An LVDS line on a BOM implies differential routing and matched pairs, which constrains which parts are valid substitutes.
Logic level: The voltage ranges a digital pin reads as logic 0 and logic 1, set by the part's family (TTL, CMOS, LVCMOS, LVDS). Mismatched logic levels between connected parts make a design fail, so level compatibility is checked before any cross-reference is accepted.
Metal-Oxide-Semiconductor Field-Effect TransistorMOSFET: A voltage-controlled switching transistor used for power switching, regulation, and logic. MOSFET lines are specified by voltage, current, and on-resistance (Rds(on)), the parameters an alternate has to match to be valid.
Insulated-Gate Bipolar TransistorIGBT: A power switching device that pairs a MOSFET gate with a bipolar output, used in motor drives and high-power conversion. IGBTs are high-value, often long-lead BOM lines where obsolescence and allocation risk concentrate.
Low-Dropout RegulatorLDO: A linear voltage regulator that holds its output with a very small input-to-output difference. LDO lines are specified by output voltage, current, dropout, and the quiescent current that matters in battery designs.
Microcontroller UnitMCU: A single-chip computer combining a processor, memory, and peripherals, at the center of most embedded products. MCUs are the BOM lines most exposed to long lead times, allocation, and EOL, so second sources and lifecycle status matter most here.
Field-Programmable Gate ArrayFPGA: A reconfigurable logic chip programmed after manufacture. FPGAs are high-cost, long-lead BOM lines with few drop-in alternates, so availability and lifecycle status decide whether a build can proceed.
Operational amplifierop-amp: An analog building block that amplifies the voltage difference between its two inputs. Op-amps are specified by parameters such as bandwidth, input offset, and supply range, which define which parts are valid cross-references.
Transient Voltage SuppressorTVS: A diode that clamps voltage spikes to protect a circuit from surges and ESD. TVS parts are chosen by working and clamping voltage, and are common, low-cost BOM lines where broad alternates exist.
Multilayer Ceramic CapacitorMLCC: The most common capacitor type in electronics, built from stacked ceramic layers. MLCCs are the highest-line-count and most allocation-prone parts on many BOMs, specified by value, voltage, case size, and dielectric.
Equivalent Series ResistanceESR: The small internal resistance of a capacitor that limits ripple current and causes heating. ESR decides whether one capacitor can replace another in a power supply, so it is checked before a cross-reference is accepted.
Ferrite bead: A passive component that suppresses high-frequency noise on a power or signal line. Ferrite beads are specified by impedance at a test frequency and by current rating, the parameters an alternate must match.
Metal-Oxide VaristorMOV: A voltage-dependent resistor that absorbs surges by dropping its resistance above a threshold. MOVs protect inputs from transients and are selected by clamping voltage and energy rating.
Negative Temperature Coefficient thermistorNTC: A resistor whose resistance falls as temperature rises, used for temperature sensing and inrush current limiting. NTCs are specified by resistance at 25C and by the beta value that sets the response curve.
Surface-Mount DeviceSMD / SMT: A component mounted onto the surface of a board rather than through holes. Most modern BOM lines are SMD, and mounting type must match the board, so a through-hole alternate is not a valid substitute.
Case size (0402 / 0603 / 0805): The standardized footprint of a surface-mount passive, given in imperial code (0402 is 0.04 by 0.02 inch). Case size is a hard constraint on a BOM: an alternate resistor or capacitor has to fit the same land pattern.
Quad Flat No-leadQFN: A surface-mount IC package with connection pads under the body and no extended leads. The same die often ships in several packages, and package is part of the orderable part number, so it constrains alternates.
Ball Grid ArrayBGA: An IC package with solder balls in a grid underneath the chip, used for high pin-count devices. BGA parts need specific assembly capability, and package is a fixed attribute of the BOM line.
SOT-23: A common small surface-mount package with three to six leads, used for transistors and small ICs. Package codes like SOT-23 are part of the orderable part number and decide which alternates fit the footprint.
Lead pitch: The center-to-center distance between adjacent pins or balls on a component. Pitch determines assembly feasibility and footprint compatibility, so it is checked when qualifying an alternate package.
Substance of Very High ConcernSVHC: A chemical on the EU REACH candidate list that triggers disclosure and, above thresholds, restriction. Buyers track SVHC content per part because it gates whether a component can be sold into regulated markets.
Conflict minerals3TG: Tin, tungsten, tantalum, and gold from conflict-affected regions, regulated under Dodd-Frank and reported with the CMRT template. A part's compliance status feeds the manufacturer's conflict-minerals reporting obligation.
Export Control Classification NumberECCN: The code that classifies a product under US export rules and decides what licenses a shipment needs. ECCN sits alongside HTS code and country of origin as trade-compliance fields buyers reconcile per part.
Harmonized Tariff Schedule codeHTS: The classification code that sets the import duty and tariff for a part. With country of origin, the HTS code drives landed cost, which increasingly decides sourcing between otherwise equal suppliers.
Automotive qualificationAEC-Q100 / Q200: The AEC stress-test standards for automotive-grade ICs (Q100) and passive components (Q200). A part marked AEC-qualified meets automotive reliability, and a non-qualified alternate is not valid for an automotive BOM.
Lead-free finish: Component terminations free of lead solder, required by RoHS for most markets. Lead-free status and the specific finish affect solderability and compliance, so both are checked when substituting a part.
Temperature grade: The rated operating temperature range of a part: commercial, industrial, or automotive. A build specifies a grade, and an alternate rated for a narrower range is not a valid substitute even if it is otherwise identical.
Not Recommended for New DesignsNRND: A manufacturer status meaning a part is still made but should not be designed into new products, an early warning of coming obsolescence. On a BOM, an NRND line signals that a second source or redesign should be planned before an EOL notice forces it.
Product Discontinuance NoticePDN: A manufacturer's formal notice that a part is being discontinued, setting the last-time-buy and last-ship dates. A PDN is the trigger for sizing a last-time buy or qualifying an alternate before the part goes EOL.
Allocation: A shortage condition where demand for a part exceeds supply and the manufacturer rations output across customers. Allocation stretches lead times and forces substitutions, and it is a supply signal to act on, not a sign a part is obsolete.
Excess & Obsolete inventoryE&O: Stock a company holds that is no longer needed (excess) or no longer usable (obsolete). E&O ties up cash and write-off risk, and accurate BOM demand and lifecycle data are what keep it from building up.
Return Material AuthorizationRMA: The authorization a supplier issues to accept a returned part, usually for a defect or warranty claim. RMA terms decide whether a wrong or bad component can be sent back, which is why NCNR parts carry more risk.
Request for ProposalRFP: A buyer's document soliciting full proposals for a project, broader than an RFQ's request for price and availability. An RFP weighs approach, capability, and terms, not only unit cost.
Stock Keeping UnitSKU: A seller's internal identifier for a distinct, stockable item, including its packaging and options. One manufacturer part number can map to several SKUs, so matching the right SKU is part of turning a BOM into an order.
Franchised (authorized) distributor: A distributor contracted by the manufacturer to sell its parts, with traceable stock and full warranty. Buying franchised is the main defense against counterfeits, so authorized sourcing is preferred wherever stock allows.
Independent distributor / broker: A distributor that sources parts on the open market rather than direct from the manufacturer. Independents fill gaps when franchised stock is out or a part is obsolete, but their stock needs extra inspection because counterfeit risk is higher.
Gray market: Genuine parts sold outside the manufacturer's authorized channel. Gray-market stock can solve an availability crunch but carries traceability and warranty gaps, so it is qualified carefully before it enters a BOM.
Counterfeit components: Parts misrepresented as genuine, whether relabeled, recycled, or outright fake. Counterfeits are the core risk of unauthorized sourcing, countered with authorized channels, traceability, and inspection standards such as AS6081.
Certificate of ConformanceCoC: A supplier document certifying that delivered parts meet the specified requirements. A CoC supports traceability and is often required for regulated or high-reliability BOMs.
Electrostatic DischargeESD: The sudden flow of static electricity that can damage sensitive components. ESD-sensitive parts need controlled handling and packaging, and mishandled stock is a hidden quality risk in the supply chain.
Mean Time Between FailuresMTBF: A reliability metric estimating the average operating time between failures of a part or assembly. MTBF and related FIT rates inform which components meet a product's reliability target.
Original Design ManufacturerODM: A company that designs and builds a product for another brand to sell as its own. ODMs own more of the design, and often the BOM decisions, than a pure contract manufacturer does.
Contract ManufacturerCM: A company that builds products to another firm's design, overlapping with EMS in electronics. CMs quote and buy against customer BOMs, so BOM accuracy drives their cost and lead time.
Original Component ManufacturerOCM: The company that actually manufactures a component, as distinct from the distributors that resell it. OCM part numbers are the canonical identity a BOM normalizes toward.
Supply Chain ManagementSCM: The coordination of sourcing, production, and delivery from raw parts to finished product. In electronics, SCM turns on BOM accuracy, lifecycle risk, and supplier data.
Line card: The list of manufacturers a distributor is authorized to sell. Checking a distributor's line card confirms whether stock for a given part is franchised or open-market.
Waste Electrical and Electronic EquipmentWEEE: An EU directive governing the collection and recycling of electronic waste, a producer obligation alongside RoHS and REACH. WEEE is a compliance dimension that follows a product past its sale.
Printed Circuit BoardPCB: The board that mechanically holds and electrically connects components. The bare PCB is itself a BOM line with its own lead time and fabrication spec, separate from the parts it carries.
Printed Circuit Board AssemblyPCBA: A printed circuit board with its components soldered on, the built product of a BOM. PCBA cost is the sum of the board, the parts, and the assembly, which is what a quote against a BOM estimates.
Design for ManufacturabilityDFM: Designing a board and its BOM so it can be built reliably and at cost, catching issues like unavailable parts or hard-to-place packages early. DFM feedback often drives BOM changes before production.
Design for AssemblyDFA: Designing a product so it can be assembled quickly and with fewer errors. DFA choices, such as package and footprint selection, feed back into which parts sit on the BOM.
Automated Optical InspectionAOI: Camera-based inspection that checks a populated board for placement and solder defects. AOI is where wrong or substituted parts on a BOM are often caught on the line.
First Article InspectionFAI: A full inspection of the first unit off a new build to confirm it matches the BOM and drawings before volume runs. FAI catches BOM and sourcing errors before they multiply.
Non-Recurring EngineeringNRE: The one-time setup cost of a build, such as tooling, stencils, and programming. NRE is quoted separately from per-unit part cost and shapes the economics of small runs.
Panelization: Grouping multiple boards onto one manufacturing panel for efficient assembly. Panelization affects per-unit cost and is part of translating a BOM into a manufacturable, quotable build.
Integrated CircuitIC: A chip that packs many electronic functions onto one piece of semiconductor. ICs are the highest-value, most lifecycle-sensitive lines on most BOMs, where sourcing effort concentrates.
Dual In-line PackageDIP: A through-hole IC package with two rows of leads. DIP is one packaging option for a given die, and the package is part of the orderable part number that a BOM specifies.
Small Outline Integrated CircuitSOIC: A surface-mount IC package with gull-wing leads on two sides. Like other package codes, SOIC is fixed in the part number, so an alternate has to match the footprint.
Dielectric class (X7R / X5R / C0G): The ceramic material class of an MLCC, coded by stability over temperature (C0G/NP0 most stable, X7R and X5R higher capacitance). Dielectric class is a hard match requirement when substituting a capacitor.
Crystal / oscillator: Frequency-reference parts: a crystal is a passive resonator, an oscillator is a powered module with a fixed output. Both are specified by frequency, tolerance, and load, and mismatched timing parts break a design.
Tantalum capacitor: A capacitor using a tantalum anode, offering high capacitance in a small size but sensitive to overvoltage and surge. Tantalum lines are chosen by value, voltage derating, and ESR, and carry their own supply and compliance considerations.
TO-220: A through-hole power package with a metal tab for heat-sinking, used for regulators, MOSFETs, and rectifiers. Its surface-mount equivalent is the D2PAK, so package must match when substituting a part on a BOM.
D2PAK (TO-263): The surface-mount equivalent of the TO-220 power package, soldered to a board pad that spreads heat. D2PAK and TO-220 can share a die but not a footprint, so they are not interchangeable on a BOM without a layout change.
DPAK (TO-252): A compact surface-mount power package for medium-power MOSFETs and regulators, smaller than the D2PAK. Package code is fixed in the orderable part number, so an alternate has to match the same footprint.
Quad Flat PackageQFP: A surface-mount IC package with gull-wing leads on all four sides, in pin counts from tens to hundreds. Variants like TQFP differ by thickness and pitch, and the exact package is part of the BOM line.
Thin Small Outline PackageTSOP: A thin surface-mount IC package with fine lead pitch, common for memory. Like every package code, TSOP is fixed in the part number and constrains which alternates fit the footprint.
Dual Flat No-leadDFN / SON: A small surface-mount package with pads under two sides and no extended leads. DFN (also called SON) trades board space for tighter assembly tolerances, and package is a hard match when sourcing an alternate.
Schottky diode: A diode with a low forward voltage drop and fast switching, used in power and RF circuits. Schottky parts are specified by forward voltage, current, and reverse voltage, the parameters a valid cross-reference must match.
Zener diode: A diode that conducts in reverse at a precise breakdown voltage, used for voltage reference and protection. Zeners are selected by their zener voltage and power rating, which fix which alternates are valid.
Light-Emitting DiodeLED: A diode that emits light when forward-biased, used for indication and illumination. LEDs are specified by color, forward voltage, current, and package, all of which constrain substitution on a BOM.
Bipolar Junction TransistorBJT: A current-controlled transistor used for switching and amplification. BJTs are specified by polarity (NPN or PNP), voltage, current, and gain, which decide which parts are drop-in alternates.
Electrolytic capacitor: A polarized capacitor offering high capacitance for bulk storage and filtering, with a life set by temperature. Electrolytics are chosen by value, voltage, ripple current, and rated life, and are sensitive to reverse polarity.
Inductor: A passive component that stores energy in a magnetic field, used in filters and power conversion. Inductors are specified by inductance, current rating, and DC resistance, the parameters an alternate must match.
Connector: A component that joins boards, cables, or modules electrically and mechanically. Connectors are specified by pin count, pitch, mating type, and current rating, and are frequent long-lead, single-source lines on a BOM.
Relay: An electrically operated switch, mechanical or solid-state, that controls a higher-power circuit with a low-power signal. Relays are specified by coil voltage, contact rating, and form, which constrain valid alternates.
Fuse: A protective component that opens a circuit when current exceeds a rating. Fuses are specified by current, voltage, and breaking capacity, and the type (fast or slow blow) has to match for a substitute to be valid.
Resettable fuse (PTC): A polymer device (PTC, also called a polyfuse) that limits current during a fault and resets when it cools. Resettable fuses are chosen by hold and trip current, replacing one-time fuses where self-recovery matters.
International Traffic in Arms RegulationsITAR: US rules controlling the export of defense-related articles and technical data. ITAR-controlled parts carry citizenship and licensing constraints in the supply chain, adding sourcing limits beyond price and availability.
Export Administration RegulationsEAR: US rules controlling the export of most commercial and dual-use items, classified by ECCN. EAR status, with ITAR, decides whether a part can ship to a given destination or customer.
California Proposition 65Prop 65: A California law requiring warnings for products containing listed chemicals. Prop 65 exposure is tracked per component because it drives labeling obligations for products sold into California.
Just-in-TimeJIT: An inventory strategy that receives parts only as production needs them, minimizing stock. JIT lowers carrying cost but raises exposure to lead-time and allocation shocks, so it depends on reliable supplier data.
Material Requirements PlanningMRP: A system that turns a production schedule and BOMs into time-phased part demand and purchase orders. MRP output is only as accurate as the BOM and lead-time data it runs on.
Enterprise Resource PlanningERP: The system of record for orders, inventory, and purchasing across a company. Sourcing decisions feed and draw from the ERP, and BOM and part data have to reconcile with it.
Kanban: A pull-based replenishment method that signals reordering when stock hits a threshold. Kanban keeps line-side inventory low and steady, and works best for stable, short-lead parts.
Consignment inventory: Stock a supplier owns and stores at the customer until it is used, when ownership transfers. Consignment shifts carrying cost to the supplier and is common for high-use BOM lines.
Kitting: Assembling the parts of a BOM into a single ready-to-build kit before production. Kitting turns a sourced BOM into a physical unit and surfaces any missing or wrong lines before the run.
Turnkey: A build model where the provider sources every part and delivers the finished assembly, versus consignment where the customer supplies parts. Turnkey puts full BOM sourcing on the provider, making quote accuracy central.
Dual sourcing / second source: Qualifying two suppliers or two manufacturer parts for the same BOM line. A second source protects a build against allocation, EOL, and single-supplier failure, and is the standard hedge for critical parts.
Vendor Managed InventoryVMI: An arrangement where the supplier monitors and replenishes stock at the customer against agreed levels. VMI smooths availability for steady BOM lines but ties the relationship to accurate demand data.
Safety stock: Buffer inventory held to absorb demand spikes and lead-time variability. Safety stock sizing trades holding cost against stockout and line-down risk, and leans on lead-time and usage data.
Estimated Annual UsageEAU: The forecast quantity of a part a buyer expects to consume in a year. EAU drives pricing tiers, contract negotiations, and last-time-buy sizing on a BOM.
O2 AI: O2 AI (o2tech.ai) is a supply chain AI company based in Berkeley, California, founded in 2025. It builds a BOM agent and decision layer for electronics sourcing, pricing, and quoting. O2 AI is independent and not affiliated with O2 Telefónica or Virgin Media O2, the UK telecommunications brand, or with any other company using the O2 name.

What is a BOM decision layer? Component obsolescence & EOL: 2025 data O2 vs BOM management software

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