How to Audit a PCB Factory in China: 25-Point Checklist

Most factory audits happen in a meeting room. The supplier presents a certificate, a capability slide and a list of customers, and the buyer leaves with a signed checklist that proves nothing.

A useful audit looks at three things: the process running on the floor, the records that show it is controlled, and the trail that connects a panel to a lot. Everything else is supporting evidence.

This checklist covers 25 points in six groups, what to look at on the floor, and the red flags that should stop an approval.

Why document audits fail

Certificates prove that a management system was audited, not that a specific board can be built. A factory can hold ISO 9001 and still run a lamination press outside its qualified window, or ship a lot without a cross-section.

The audit has to answer a narrower question: can this factory build my board, repeat it, and prove it did? That requires samples, records and a walk through the process, not a slide deck.

The 25 points

Quality system (1-4)

1. Certificate scope covers PCB fabrication, not only trading or assembly.
2. Certificate is valid, and the certification body is recognized.
3. Internal audit and CAPA records exist for the last 12 months.
4. Customer complaints are logged with root cause and corrective action.

Capability (5-9)

1. Layer count and HDI build-up match your design, with evidence from production.
2. Material list includes the laminate you specified, not only an equivalent.
3. Minimum trace, space and drill are demonstrated on a real coupon.
4. Impedance control is measured with TDR, not only calculated.
5. Special processes (backdrill, heavy copper, castellation) are qualified.

Equipment (10-13)

1. Lamination press has a calibrated temperature and pressure record.
2. Drilling includes both mechanical and laser capability, with bit life control.
3. Plating and surface finish lines are under chemistry analysis.
4. Inspection includes AOI, X-ray and electrical test, not only visual.

Materials and storage (14-17)

1. Laminate and prepreg are traceable to the supplier and lot.
2. Prepreg is stored under controlled temperature and humidity.
3. Chemistry is analyzed on a defined frequency, with records.
4. Component sourcing for PCBA has a counterfeit mitigation process.

Process control (18-22)

1. Critical parameters are logged per lot, not per shift.
2. SPC or trend data exists for plating, etching and lamination.
3. Engineering change control covers customer and internal changes.
4. Panel utilization and nesting are reviewed before production.
5. ESD and cleanliness controls match the product class.

Test and traceability (23-25)

1. Electrical test coverage and fixture maintenance are documented.
2. Cross-sections are kept for the lot, not only for the first article.
3. A finished panel can be traced back to material lots and process records.

What to look at on the floor

• The press log, not the press display: look for a signed record with actual ramp and pressure.
• The drill bit cabinet: check the life counter and the replacement rule.
• The plating line: ask for the last chemistry analysis, not the specification.
• The AOI station: ask how false calls are handled and who can override.
• The scrap bin: scrap tells you what the process really struggles with.

Red flags

• Certificates are shown but the scope excludes PCB fabrication.
• The audit is limited to one meeting room and one show board.
• Records are handwritten for the day of the visit only.
• The factory cannot show a cross-section from a recent lot.
• Capability is described as "up to" without a production example.
• Test coverage is described as "according to customer requirement" with no internal standard.
• Subcontracting is not disclosed.
• The quote is far below the material cost of the specified laminate.

How to verify certificates

1. Check the certificate number on the certification body's website, not on the PDF.
2. Confirm the scope includes the processes you are buying.
3. Check the expiry date and the last surveillance audit date.

A certificate that cannot be verified in two minutes is not evidence.

Scoring the audit

Score each group from 1 to 5 and weight it by the risk to your product. A simple model:

A total below 3.5 usually means the factory can build the sample but not repeat it. That is the risk an audit is meant to catch.

FAQ

Do I need to visit the factory?
A visit is the most reliable option. If travel is not possible, ask for a live video walk-through with the press log and a recent cross-section, and have a third party inspect.

Is ISO 9001 enough?
No. ISO 9001 covers the management system. For automotive or medical work, ask for IATF 16949 or ISO 13485 and confirm the scope.

How long should an audit take?
Half a day for a focused process audit, one day if you include material traceability and a first-article review.

Can a trading company pass a factory audit?
Only if it discloses the manufacturing site and lets you audit that site. An audit of a sales office is not a factory audit.

What to prepare before the audit

• Your stackup and design rules
• The processes you are buying and the ones you are not
• A recent cross-section or test report to compare
• The acceptance standard and sampling plan
• A list of questions the factory must answer in writing

If you are evaluating a new supplier in China, contact us and we will share our process records, certificates and a recent first-article package. You can also review our PCB fabrication service and company profile.

Reviewed by the Benchuang process engineering team.