PCB Technical - SMT NADCAP AC7120 audit requirements

NADCAP is a certification system for special engineering management systems for national aerospace and defense contractors or authorized projects. AC7120 is a standard for auditing printed circuit board components, covering all processes of the printed circuit board assembly manufacturing process, such as CAD ( Computer -Aided Design) data, programming, component placement, AOI (Automated Optical Inspection) or X-ray machine inspection, wave soldering, reflow soldering, manual soldering, assembly, cleaning, coating and sealing, Final test (flying probe, needle bed, boundary test, functional test), rework, etc.

AC7120 audit is mainly divided into two parts: document audit, mainly to check whether the working procedures and specifications meet the requirements of the audit clauses, and whether they are complete and sufficient; the effectiveness of the implementation is mainly to check whether the effective implementation and compliance with the requirements of the documents are conducted through model making (Customer requirements, industry requirements).

2.1 Basic audit requirements

Although AC7120 is an audit requirement for the process compliance of the PCB assembly manufacturing process, there are some basic requirements that can be universally used for other production line control, such as:

a) Personnel requirements: IPC for operators and inspectors, proof of vision inspection; familiarity with various specifications and positions; work as required.

b) Material requirements: specified in the design drawings; in compliance with ESD (Electro-Static discharge)/MSD (moisture sensitive device) control; use expiration date, opening expiration date, subcontract expiration date identification and control; entering the institute Acceptance required; periodic testing in use.

c) Equipment requirements: maintenance checklist; authorized personnel to operate the equipment; configuration of various monitoring devices; test and save every shift;

d) Process requirements: meeting international or industry standards; confirmation and testing after each process; procedure control; rationality of process methods;

e) Environmental requirements: temperature, humidity, ESD requirements in EPA (Electrostatic Protected Area), noise, illuminance, and cleanliness.

These required documents will be reviewed by the auditor during the audit and will be verified item by item during the on-site audit.

2.2 Quality control requirements

2.2.1 Pay attention to the quality system

AC7120 professional audit is always based on the implementation of the unit's quality management system requirements, which specifically involves: quality manuals, procedures and document control, personnel qualifications, environmental requirements, material control, supplier control, first article appraisal, non-conforming product management and corrective measures, QA (Quality Assurance, quality assurance) personnel, internal audit effectiveness, combined with process audit requirements will be audited, and require implementation evidence.

2.2.2 Pay attention to the effectiveness of corrective measures

Pay attention to the effective implementation of corrective measures for non-conformities in the previous review process and the verification of the results. If the corrective measures are not effectively implemented and maintained for a long time, the AC7120 professional audit will issue 2 serious non-conformities: one is a duplicate problem, and the other is that the system cannot maintain the effectiveness of the corrective measures.

2.2.3 Pay attention to traceability

Any material must be traceable to the original manufacturer’s batch number, especially the COC must be attached to the first article report. All materials on site must have sub-packaging labels, indicating: material name and specification, original packaging validity period, batch number, opening validity period, subcontractor, and the material batch number must be transplanted with the work order. The files of all products are kept permanently, and all on-site production records are kept for more than 5 years.

2.3 Process professional requirements

2.3.1 ESD control

Static control is first of all the control of the EPA area: the hardware facilities in the area (floor, table mats, chairs, etc. must be made of anti-static materials), equipment grounding, and other objects should be made of anti-static materials (turnover boxes, trash cans, tweezers, Suction pen). If there is no condition to use anti-static materials, an ion fan should be configured during operation.

Static control of ESD materials, anti-static pockets, wear anti-static wrist straps when taking and putting them away.

Static control of personnel, daily inspection of anti-static shoes and wrist testing.

2.3.2 MSD control

Humidity-sensitive devices need to identify the level, dry according to the original factory prompts before assembly, and follow the assembly and use within the life of the workshop.

2.3.3 PCBA cleaning

Because PCBA involves many processes, there is still some time to finalize the assembly after the first side is soldered. For manufacturers who deliver the complete machine, PCBA needs to be cleaned after single board debugging, and PCBA is often cleaned after more than 8 hours after soldering. At this time, the cleaning effect can no longer remove the flux on the PCBA most effectively, so NADCAP AC7120 stipulates that the PCBA needs to be cleaned within 8 hours after soldering. If water cleaning or semi-aqueous cleaning is used, a drying time of 4 hours will be required, which will greatly restrict the process cycle of the production line, so vapor phase cleaning can be considered.

2.3.4 Rework and repair control

In the industry standard, there is only a limit on the number of rework and repairs, but NADCAP AC7120 emphasizes that rework is not allowed, and customer opinions must be obtained for repairs.

Process professional requirements mainly review the effectiveness of the on-site execution, which is also the focus of the AC7120 audit. During the on-site audit, attention will be paid to whether each regulation has the correct traceability, whether the execution in the process is accurate and in place, whether the records are complete, and whether the operators can Obtain current and effective guidance documents. All stipulated requirements are the promises of the organization and must be fulfilled in the process.