BOM
Understanding BOMs
The BOM is the single source of truth for what goes on a board. It is extracted from the schematic (EBOM) and refined for production (MBOM). Each line item maps a reference designator (e.g., C15) to a specific part number (e.g., GRM155R71C104KA88D), quantity, and placement location. The BOM must be version-controlled alongside the PCB design files.
BOM management is critical for RF products where component tolerances directly affect circuit performance. A 5% capacitor in a filter can shift the passband; specifying 1% or NPO dielectric may be necessary. The BOM captures these requirements unambiguously.
Q = quantity per board
P = unit price at production volume
Typical RF module BOM breakdown:
Active ICs (MMIC, LNA): 40-50%
Passives (caps, res, ind): 10-15%
Connectors: 10-20%
PCB substrate: 15-25%
BOM Types
| Type | Audience | Content | Use |
|---|---|---|---|
| EBOM | Engineering | By subsystem, alternates | Design review |
| MBOM | Manufacturing | Placement coords, process | Production |
| SBOM | Service | Replaceable modules | Field repair |
| Costed BOM | Procurement | Pricing, lead times | Quoting |
Frequently Asked Questions
Contents?
Ref des, qty, MPN, description, package, value, tolerance, alternates, cost, lifecycle status. RF: substrate and connector details too.
EBOM vs MBOM?
EBOM: by subsystem, design notes. MBOM: by assembly sequence, placement coordinates, process specs. Both version-controlled.
Cost optimization?
Consolidate values, standardize packages, specify alternates, track lifecycle. RF: 2-3 ICs are 60-80% of cost.