3.4 FAI Build Evidence Pack and MP Release

First Article Inspection (FAI) is the forensic audit of the manufacturing process. It does not merely prove that a product can be built; it proves that the process is robust, repeatable, and statistically capable of scaling to Mass Production without exponential cost growth or quality escapes. The FAI Build Evidence Pack is the mechanism that transforms a physical build event into the hard data required for the final “Go/No-Go” decision. Without this concrete evidence, launching Mass Production (MP) is taking unnecessary inventory risk.

The FAI Evidence Pack Requirements

The Evidence Pack must be submitted as a single, consolidated PDF or digital archive containing the following validated datasets. Accepting scattered emails, chat messages, or verbal confirmations from the factory floor should be avoided.

1. Yield Summary and Defect Pareto

The assembly line yield data must be aggregated to identify systemic process weaknesses.

First Pass Yield (FPY): The exact percentage of units that passed all manufacturing and inspection processes (SPI, AOI, X-Ray, ICT, FCT) on their very first attempt, with zero rework, must be reported. A high final yield combined with a low FPY indicates a hidden, expensive rework cost structure.
Defect Pareto: The top failure modes must be categorized.
- When Solder Bridges are the top defect, engineering must review stencil aperture reduction and solder paste print pressure.
- When Part Misalignment is the top defect, engineering must review SMT nozzle selection, placement speed, and vision recognition data.

2. The “As-Built” Configuration (Traceability)

Early NPI builds rarely match the initial documentation perfectly. The Evidence Pack must capture the reality of what actually occurred on the shop floor.

Redline BOM: The Bill of Materials must be submitted with clear markings showing any alternative components used, temporary substitutions, or value changes that were required to make the board function.
EQ/ECO Log: All Engineering Queries (EQ) raised by the factory during the build must be compiled and all resulting Engineering Change Orders (ECO) must be documented.
Reflow Profile: The measured thermal profile (temperature vs. time) must be attached, directly overlaid onto the solder paste manufacturer’s specified tolerance window.

3. Test and Programming Proof

Programming Verification: A log summary confirming that the correct checksums and firmware versions were successfully loaded into the devices must be provided.
Test Data: Actual parametric test results (voltage, current, and frequency readings) must be submitted, rather than just Pass/Fail booleans. This establishes the baseline statistical quality distribution (Cₚₖ) for the product.

Pro-Tip: Accepting “NFF” (No Fault Found) as a root cause during the FAI stage should be avoided. When a unit failed a test and then subsequently passed on a retest without modification, the test process itself is unstable. These instances must be labeled as “Process Instability” and the test fixture contact reliability or measurement tolerances must be investigated.

The MP Release Gate

The transition from NPI into Mass Production is a formal “Gate Review.” This transition requires a strict, binary freeze of the Golden Data Pack.

Sign-off Authority

Three distinct signatures are mandatory to unlock Mass Production:

Manufacturing Engineering: Confirms the manufacturing process capability and fixture stability.
Quality Assurance: Confirms all critical dimensions and cosmetic standards meet the Acceptable Quality Limit (AQL).
Product/Design Engineering: Confirms the device functions as intended by the design.

The Frozen State

Upon official MP Release, the following elements become Read-Only:

Gerber and ODB++ Fabrication Files.
Pick & Place Centroid Data.
The Approved Vendor List (AVL).
Test Limits and Firmware Checksums.

Any modification to these files after this point, no matter how minor, requires a formal Process Change Notification (PCN).

Re-FAI Triggers

While continuous improvement is necessary, uncontrolled changes introduce severe risk. Clear triggers must be defined that formally invalidate the previous FAI and mandate a new qualification build.

Trigger Logic:

When a Critical Component (MCU, Sensor, PCB Laminate) changes manufacturer, a Delta-FAI (partial qualification focused on the change) must be performed.
When production is moved to a New Facility or a new SMT Line with different equipment capabilities, a Full FAI must be performed.
When the product has been dormant and unbuilt for ≥ 12 months, a “Refresher” FAI must be performed to validate the integrity of expired solder paste, aging components, and drifted machine settings.

Final Checkout: FAI build evidence pack and MP release

Parameter	Critical Requirement	Control Method
FPY Target	≥ 95% (or the agreed-upon target)	Auto-generated yield report from the MES.
Documentation	100% match to the physical “As-Built” state.	Redline BOM signed off by engineering.
Defect Analysis	The root cause must be identified for the Top 3 defects.	Pareto Chart & formal 8D Report.
Process Window	Cₚₖ ≥ 1.33 for all critical tests.	Parametric data statistical analysis.
Gate Status	Configuration is locked and frozen.	Formal MP Sign-off Document.