BOM Cost Review Skill

A BOM is a list of promises: that each part will be buyable, at that price, at your volume, for the life of the product. This skill reviews a BOM the way a sourcing veteran does — Pareto the cost, flag the single-source and end-of-life traps before they become line-down events, and separate real cost-down candidates from wishful thinking.

What This Skill Produces

• A cost rollup by commodity class with % of total
• Top-10 cost drivers (they usually carry 70–80% of BOM cost)
• Risk flags per line: single-source, lifecycle (EOL/NRND), MOQ mismatch, long lead time
• A prioritised cost-down candidate list with realistic savings and effort
• Tariff and logistics sensitivity notes

Required Inputs

Ask for these if not provided; work with a partial BOM if that's all there is, labelling gaps [missing — request from EE/sourcing]:

• The BOM — part numbers, descriptions, quantities, unit costs (any format; structure it)
• Annual forecast volume — needed for MOQ math and price-break realism
• Target BOM cost — what "good" looks like
• Sourcing detail if available — approved vendors, country of origin, lead times, lifecycle status
• Product stage — EVT-stage BOMs get design-out suggestions; MP-stage BOMs get negotiation/resourcing ones

Review Framework

1. Rollup. Group into commodity classes (PCBA/semiconductors, passives, display, battery, mechanicals/enclosure, cables & connectors, packaging & accessories). Show cost and % per class, and total vs target with the gap.

2. Pareto. Rank the top-10 lines by extended cost (unit × qty). Everything after these is noise until the big ten are handled.

3. Risk flags — apply per line, worst flag wins:

Flag	Trigger	Why it matters
🔴 Single-source	One qualified vendor, no drop-in alternate	One factory fire from line-down
🔴 EOL / Obsolete	Lifecycle status EOL or last-time-buy announced	Forced redesign or LTB cash outlay
🟠 NRND	Not recommended for new design	Fine now, redesign within product life
🟠 MOQ mismatch	MOQ > ~13 weeks of forecast demand	Cash tied up, scrap risk on ECO
🟠 Long lead	Lead time > 16 weeks	Forecast error becomes shortage
🟡 Custom/tooled part	Custom silicon, tooled mechanical	Switching cost locks the vendor in

4. Cost-down candidates. For each: the lever (negotiate at volume break / second-source and dual-run / value-engineer spec — e.g. tighter-than-needed tolerance, over-spec'd connector / design-out entirely), estimated saving per unit, effort, and earliest cut-in (which build or ECO).

5. Tariff & logistics sensitivity. Note country of origin concentration, HTS-code exposure for high-value lines, and what a duty change or freight spike does to landed cost.

Output Format

BOM review: [product / revision]

1. Summary — total BOM cost vs target, gap, one-line verdict
2. Cost rollup — table by commodity class (cost, % of total)
3. Top-10 cost drivers — table: part, qty, unit cost, extended cost, % of BOM, flags
4. Risk register — every 🔴/🟠 line with flag, evidence, and recommended action + owner
5. Cost-down candidates — ranked table: lever, est. saving/unit, effort, cut-in point, confidence
6. Tariff/logistics sensitivity — exposure summary and scenarios
7. Data gaps — lines missing cost, lifecycle, or sourcing data [missing — request]

Quality Checks

• Rollup total reconciles with the sum of lines — no silent arithmetic drift
• Every top-10 line has a lifecycle and sourcing note, even if [missing — request]
• Each cost-down candidate names the lever, the saving, and the cut-in build/ECO
• MOQ flags are computed against the stated forecast, not gut feel
• Single-source flags distinguish "no alternate exists" from "alternate not yet qualified"

Anti-Patterns

• Do not quote unit prices without a volume — a price without its quantity break is fiction
• Do not chase pennies on passives while a top-10 line is single-sourced and EOL
• Do not claim a cost-down saving without naming the lever and who has to act
• Do not treat distributor stock as supply security for a single-source part
• Do not ignore custom/tooled parts in risk review — they are the hardest to move
• Do not fabricate costs for missing lines — label them and carry the uncertainty into the total