BOMs & fabrication outputs
The Bill of Materials (BOM) is the complete shopping list: every component on the board with its reference designators, value, package, and a specific manufacturer part number. “10 kΩ resistor” isn’t enough for someone else to buy the right part. “Brand X, 10 kΩ, 1%, 0603” is. The BOM is also where availability bites. Designing in a part that turns out to be unobtainable is a rite of passage you can skip by checking stock early.
Gerber files are the manufacturing drawings: one file per layer (each copper layer, solder mask, silkscreen) plus drill files listing every hole’s position and size. Together they describe the bare board completely. The fab never opens your design software; it only sees these exports. The format is decades old and remains the industry’s common language.
If a factory is also assembling the board, two more outputs join the package: the pick-and-place file, which gives each part’s position and rotation for the placement machines, and usually the paste layer for laser-cutting the solder-paste stencil. BOM, Gerbers, drill, and pick-and-place together form a complete, unambiguous description of your product.
Key points
- The BOM lists every part with exact part numbers, precise enough for someone else to buy.
- Check part availability while designing, not after. Stock-outs force redesigns.
- Gerber and drill files fully describe the bare board. They’re all the fab ever sees.
- Assembly adds the pick-and-place file and stencil data to complete the package.
Practice
0 of 2 answered · Not startedWrong answers just let you try again, and hints are there if you want them. Answering every question first time, without hints, is what earns mastery.
- 1
Which file tells the assembler where each part goes and how it is rotated?
- 2
What most commonly stalls a board order?
