PCBA: what to ask before you send Gerbers
Most board problems are decided before the files leave your desk.
Filed under Engineering and services
The short answer: send the assembler a complete package and a short list of questions, and read the answers before you read the price. Gerbers alone are not a build package.
What goes in the package
Gerbers or ODB++, a pick-and-place file, a BOM with manufacturer part numbers and approved alternates, assembly drawings with polarity marked, and the acceptance class you expect the boards to meet.
Questions about the BOM
Which parts are long-lead or single-source? Which alternates will the assembler propose, and who approves them? Who buys the parts, and who carries the risk of a substitution? Those answers are the core of an EMS contract manufacturing agreement, so get them in writing.
Questions about the line
What paste inspection and automated optical inspection run on every board? Is X-ray available for hidden joints? How are moisture-sensitive parts stored and baked?
Questions about test
Who writes the functional test, and who owns the fixture? What happens to a board that fails: rework, scrap or a report back to you?
First article and after
Ask for a first article report against your drawing before the lot runs, and agree how a change on either side is approved. A board that passes once and drifts later is a process question, not a design one.
Straight answers
Are Gerbers enough to quote PCB assembly?
No. A PCB assembler also needs a pick-and-place file, a BOM with manufacturer part numbers and alternates, assembly drawings and the acceptance class you expect.
Who should approve part substitutions on a PCBA build?
You should. Agree in writing that no alternate goes on the board without your approval, and keep the approved alternates on the BOM.
How this note was made: researched and drafted with AI assistance, checked against the sources listed below and edited at JCH Design & Manufacturing.