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5.1 Traceability Standards (IPC-1782)

Traceability is not an archive of what happened; it is the active defense against liability. In the event of a field failure, the granularity of your data determines the scope of your recall. If your traceability is weak, you recall 100% of production. If it is robust, you recall the 0.1% actually affected. Adopt the IPC-1782 standard to define the "Resolution" of your data, transforming traceability from a cost center into an insurance policy.

Defining the Traceability Level (IPC-1782 Tiers)

Do not apply the same data burden to a $5 toy and a $5,000 pacemaker. The IPC-1782 standard defines four distinct levels of granularity. Select the level based on risk, not convenience.

Level 1: Basic (Lot Traceability)

Level 2: Standard (Serialized Assembly)

  • Scope: Links Serial Number (SN) to Work Order + Test Results.
  • Granularity: "Unit SN-123 passed test on Date X." (Components are still Batch-level).
  • Use Case: White Goods, Industrial Controllers.

Level 3: Advanced (Component Serialization)

  • Scope: Links Serial Number (SN) to Key Component Lots.
  • Granularity: "Unit SN-123 contains CPU Lot Y and Memory Lot Z."
  • Use Case: Automotive (Safety Critical), Medical Class II.

Level 4: Precision (Full Process Traceability)

Selection Logic

  • If Product Liability Cost > Production Cost → Adopt Level 3 or 4.
  • If Regulatory Requirement (FDA/IATF) exists → Follow the mandated Level.

The Chain of Custody (Forward & Backward)

A traceability system must answer two specific questions instantly. If it takes > 1 hour to query, it is broken.

Forward Traceability (Containment)

  • Question: "We found a bad Reel of Resistors (Lot 999). Where are they?"
  • Action: Input Lot 999 → Output List of Parent Serial Numbers.
  • Goal: Quarantine specific units before they ship.

Backward Traceability (Root Cause)

  • Question: "Unit SN-123 failed in the field. How was it built?"
  • Action: Input SN-123 → Output Bill of Materials (Lots) + Process History.
  • Goal: Identify the common factor (e.g., all failures used Lot 999).

Pro-Tip: Test your "Recall Velocity" annually. Give a Lot Number to the Quality Engineer and measure how many minutes it takes to generate the list of affected Serial Numbers. Target: < 15 minutes.

Data Retention & Immutability

Data that expires before the warranty does is useless. Data that can be edited is fraudulent.

Retention Policy

  • Standard: Product Lifetime + 2 Years (or 7 Years for Tax/Audit).
  • Medical/Aero: Indefinite (or 15+ Years).

Immutability Logic

  • If a record is written → It is Read-Only forever.
  • If a correction is needed → Append a new record.
  • Storage: Use WORM (Write Once, Read Many) storage or Blockchain-verified logs for Level 4 systems.

The "Genealogy" Tree Structure

Traceability data is hierarchical. The MES must build a parent-child relationship tree as the product moves down the line.

Structure

  • Root: Finished Good SN.
    • Branch 1: PCB SN.
      • Leaf: CPU Lot.
      • Leaf: Capacitor Reel.
    • Branch 2: Housing Lot.
    • Branch 3: Firmware Version.

Assembly Logic

  • If Sub-Assembly (Branch 1) is scrapped → Invalidate the Parent.
  • If Sub-Assembly is swapped (Repair) → Update the Tree instantly.

Final Checklist

Category

Metric / Control

Threshold / Rule

Strategy

Level Selection

Level defined per Product Family (L1-L4)

Speed

Query Latency

Forward/Backward Trace Report < 15 Mins

Scope

Components

Critical Components (Class A) tracked to Lot/SN

Integrity

Edit Access

0 Users have "Update/Delete" permission on Trace Logs

Process

Parameter Link

Level 4 links Process Data (Temp/Torque) to SN

Validation

Mock Recall

Perform 1 Mock Recall per Year

Archive

Backup

Off-site Immutable Backup verified quarterly

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