How to Check Electronic Part Availability Before PCB Order

Availability means enough of the exact orderable part

A search result for a component family is not proof that your board can be built. The useful question is narrower:

Can an approved source supply enough units of the exact manufacturer part number, in the required package and packing, for this build and its expected attrition?

“In stock” can refer to another package suffix, another regional warehouse, an unpriced marketplace listing, or fewer pieces than the build needs. A distributor may show a family page with inventory while the particular orderable variant in your BOM has a 26-week lead time. An assembly provider’s internal stock can also differ from the inventory shown by its affiliated component storefront.

Do this check before committing to a footprint, again when the layout is nearly frozen, and once more immediately before release. Stock is a snapshot, not a property of the schematic.

Start with an exact-MPN BOM

Every fitted line item needs at least these fields:

• manufacturer;
• complete manufacturer part number (MPN), including suffixes;
• quantity per board;
• footprint/package;
• one or more supplier SKUs, if the purchasing channel is fixed;
• lifecycle state and datasheet URL;
• approved alternate MPNs, when already qualified.

100 nF, 0402 is a design value, not a purchasable identity. It omits voltage rating, dielectric, tolerance, and manufacturer. STM32, ESP32, or USB-C connector is even less actionable. The KiCad BOM setup guide explains how to put sourcing fields on symbols rather than maintaining a disconnected spreadsheet.

KiCad 9 can export explicit custom fields from a schematic. Adapt the names to those used in your project:

mkdir -p build/bom
kicad-cli sch export bom \
  --fields 'Reference,Value,Footprint,Manufacturer,MPN,Supplier,Supplier PN,${QUANTITY},${DNP}' \
  --labels 'Refs,Value,Footprint,Manufacturer,MPN,Supplier,SupplierPN,Qty,DNP' \
  --group-by 'Value,Footprint,Manufacturer,MPN' \
  --exclude-dnp \
  -o build/bom/procurement.csv \
  board.kicad_sch

Grouping by MPN matters. Two 10 kΩ resistors with different voltage ratings or technologies must not collapse into one line merely because their displayed values match.

Calculate the quantity the build really consumes

For each BOM line, calculate:

required quantity =
  boards to assemble × quantity per board
  + assembler attrition
  + setup/minimum-purchase allowance
  + engineering spares

Attrition is not a universal percentage. Assembly houses publish or quote different rules by package, packing type, and placement quantity. Tiny passives supplied on cut tape may need more leader or surplus than tray-packed ICs. Ask the assembler rather than adding an arbitrary blanket margin.

For hand-built prototypes, spares still matter. Add extra inexpensive passives, connectors vulnerable to rework, and at least one spare of critical ICs when the budget permits. If a supplier sells only full reels or fixed multiples, compare its minimum order to the calculated need.

Check that inventory exceeds the required quantity with sensible margin. A listing of 43 pieces is not a robust source for a 40-piece need when carts are not reservations and other customers can buy concurrently.

Check four independent signals

1. Manufacturer status

Open the manufacturer’s current product page, not only a distributor listing. Look for lifecycle terms such as active, production, not recommended for new designs, last-time buy, or obsolete. Search the manufacturer’s product-change and discontinuance notices when longevity matters.

Active does not mean currently stocked; obsolete does not mean unavailable today. Lifecycle and inventory answer different questions. For a new design, a well-stocked last-time-buy part still creates future risk.

2. Authorized distributor inventory

Search the complete MPN at two or more authorized distributors. Confirm:

• on-hand quantity, not “available to order” quantity;
• warehouse region and expected ship date;
• minimum order and order multiple;
• cut-tape, reel, tray, tube, or bulk packaging;
• unit price at the required break;
• whether the manufacturer lists the seller as authorized.

For high-value or safety-relevant parts, traceability is more important than saving a small amount through an unknown broker. Marketplace inventory can be legitimate, but it needs a separate counterfeit and date-code risk decision.

3. Assembly-provider inventory

If the PCBA vendor buys and places the parts, search its own assembly library. Confirm the internal part code maps to the exact MPN and package. Note whether it is a standard/basic part or incurs feeder/loading charges. Make sure there is enough stock in the assembly channel, not merely the retail catalog.

If you will consign parts, confirm accepted packaging, labeling, moisture handling, customs route, and surplus policy before shipping anything.

4. Lead time and replenishment credibility

A future date is not equivalent to physical stock. Distinguish manufacturer lead time, distributor expected-receipt date, and a customer-specific confirmed allocation. Dates can move. For a near-term prototype, base the release on inventory you can actually reserve or purchase, not a best-case replenishment estimate.

Qualify alternates before the shortage

An alternate is not “the first parametric-search result with similar numbers.” Compare function, pinout, absolute maximums, recommended operating conditions, timing, analogue performance, power-up behavior, firmware-visible IDs, package drawing, land pattern, and qualification grade. The strict process in MPN matching for assembly applies to alternates too.

Classify each option:

A: same footprint and pinout; no design change after full verification
B: same footprint, but BOM/firmware/component-value change required
C: different footprint or layout constraints; board revision required
D: functionally different; architectural redesign required

Do not put a category C part in an “alternate MPN” cell and expect purchasing to solve it. If two footprints can genuinely be supported, design and validate a documented dual-footprint before release.

Save a sourcing snapshot with the release

For each critical line, record the timestamp, source, observed stock, price break, lifecycle, required quantity, approved alternates, and reviewer. A small CSV is sufficient:

MPN,Required,Source,ObservedStock,CheckedUTC,Lifecycle,Decision
EXACT-MPN-A,24,Distributor A,138,2026-07-14T10:30Z,Active,approved
EXACT-MPN-B,12,Assembler library,75,2026-07-14T10:35Z,Active,approved

This snapshot is evidence of the release decision, not a live promise. Automate fresh queries when APIs and terms permit, but retain the result used for approval.

Make availability part of the manufacturing gate: no missing MPNs, no unapproved lifecycle states, sufficient quantity, and no BOM/footprint mismatch. If a part fails that gate, follow the controlled response in what to do when a part goes out of stock. Finding the issue before ordering boards preserves every option; finding it after fabrication turns sourcing into rework.