3.1 APQP & PPAP

Quality cannot be inspected into a product; it must be designed into the process. Advanced Product Quality Planning (APQP) is the architecture of prevention, ensuring that physical reality matches engineering intent before the cash burn of mass production begins. PPAP (Production Part Approval Process) is the forensic evidence that this architecture works at rate. Skipping these steps guarantees a launch defined by line stops, rework, and field failures.

APQP: The Architecture of Prevention

APQP is not a checklist; it is a phased maturity model. You do not proceed to the next phase until the risks of the current phase are neutralized.

The Logic of Phased Gates:

• Phase 1 (Plan): Define the "Voice of the Customer."
  • IF Requirements are ambiguous -> THEN Stop. You cannot build a compliant product against vague targets.
• Phase 2 (Product Design): Freeze the schematic and mechanicals.
  • Output: DFMEA (Design Failure Mode Effects Analysis). Identify what can break.
  • Rule: Critical Characteristics (CC) must be identified here (e.g., voltage rail tolerance, heatsink gap).
• Phase 3 (Process Design): Design the assembly line to handle the Product Design.
  • Output: PFMEA (Process FMEA) and Control Plan. Address how the build process might fail the design (e.g., solder paste volume, screw torque).
• Phase 4 (Validation): Build off-tool, off-process.
  • Action: Run the PVT (Production Validation Test). Collect data for Cp/Cpk and Gauge R&R.
• Phase 5 (Launch): Mass Production (MP).
  • Requirement: Safe Launch Plan (Early Production Containment) is active until exit criteria are met.

Pro-Tip: Do not copy-paste DFMEA failure modes into the PFMEA. The DFMEA asks "Will the capacitor overheat?" The PFMEA asks "Did the machine mount the wrong capacitor?"

PPAP: The Evidence of Capability

PPAP is the "Golden Book." It is the binding contract between Supplier and Customer stating that the process can produce parts that meet specifications at the quoted production rate.

When to Trigger PPAP (The Rules):

• IF New Part / New Product -> THEN Full PPAP.
• IF Engineering Change (ECO) to design or material -> THEN Delta PPAP (affected characteristics only).
• IF Tooling Transfer or Replacement -> THEN Full PPAP (New tool = New process).
• IF Process stopped for >12 months -> THEN Re-validation PPAP.

Submission Levels (The Resolution):

Don't guess; define the level in the purchase order.

• Level 1: PSW (Part Submission Warrant) only. (Low risk / COTS items).
• Level 3: Full submission with samples and all supporting data. (The Default for Custom Parts).
• Level 5: On-site review. (Critical Safety Items).

Critical PPAP Elements

The PPAP package typically contains 18 documents. These are the non-negotiables:

1. Part Submission Warrant (PSW): The cover sheet. Signing this implies legal accountability for the part's compliance.
2. Dimensional Results: Every dimension on the drawing must be measured on randomly selected parts (usually 5 – 30 units).
   • Rule: Global tolerance notes are not suggestions. If the drawing says "unless otherwise specified ±0.1mm," every un-dimensioned feature must be measured.
3. Control Plan: The cheat sheet for the production floor. It maps every inspection step to a tool and a frequency.
4. MSA (Measurement System Analysis): Evidence that your calipers and fixtures tell the truth.
   • IF Gauge R&R > 30% -> THEN Measurement system is Failed. Fix the fixture before fixing the part.

Pro-Tip: "Master Samples" (Golden Units) must be signed and dated. Do not throw them in a drawer; keep them in a controlled cabinet at the Point of Use for visual reference.

Final Checklist