3.1 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, your ability to surgically recall only the affected units—rather than the entire month's production—determines whether the recall costs $50,000 or $5,000,000.

We adopt IPC-1782 (Standard for Manufacturing and Supply Chain Traceability of Electronic Products) as the architectural baseline.

The Four Levels of Traceability

Do not apply "Nuclear Grade" traceability to a cable tie. Balance risk vs. cost using the IPC-1782 hierarchy. Define the level for every BOM item.

Level 1 (Basic): Lot/Batch Traceability.

• Target: Passives (Resistors, Capacitors), Mechanicals (Screws, Housings).
• Record: "Lot A123 was used on Line 1 between 08:00 and 12:00."

Level 2 (Process): Sequence Traceability.

• Target: PCBs, Standard ICs.
• Record: "Unit SN:123 passed Solder Paste Inspection at 09:05."

Level 3 (Component): Serialized Matching.

• Target: High-value silicon (CPU, FPGA), Wireless Modules, Batteries.
• Record: "Child SN:ABC was placed on Parent SN:123 at Ref Des U4."

Level 4 (Parametric): Process Data.

• Target: Safety-critical joints, Torque specs, Press-fit force.
• Record: "Screw J1 tightened to 4.5Nm with angle 12°."

Minimum Viable Record (The Data Payload)

For every production event, the MES must commit a transaction containing these five immutable dimensions. If any dimension is missing, the record is legally void.

1. Who (Actor)

• Field: User_ID
• Requirement: Must map to a specific human or service account. "Admin" is forbidden.

2. What (Subject)

• Field: Unit_Serial_Number (The Parent) + Component_Lot_Or_SN (The Child).
• Requirement: The Parent SN is the Primary Key of the Genealogy Tree.

3. Where (Location)

• Field: Resource_ID (Machine) + Slot/Feeder_ID.
• Requirement: Granularity must match the risk. Knowing it was "On the SMT Line" is insufficient; we must know it was "Feeder Slot 4, Nozzle 2."

4. When (Timestamp)

• Field: UTC_Timestamp.
• Requirement: Synchronized via NTP (See Chapter 2.4). Resolution: Milliseconds (YYYY-MM-DD HH:MM:SS.ms).

5. How (Context)

• Field: Process_Outcome (Pass/Fail) + Parametric_Data (Volts, Temp, Torque).
• Requirement: Link to the specific Recipe_ID used.

The Linkage Keys

The database schema must enforce referential integrity. A collection of logs is not traceability; a Linked Graph is traceability.

• The Golden Thread: Every child component record must have a Parent_ID field pointing to the PCBA or Sub-assembly.
• The Work Order Bridge: Every Parent_ID must link to a Work_Order_ID. This connects the physical unit to the financial ERP record.
• The Material Bridge: Every Component_Lot must link to a Goods_Receipt_ID. This connects the shop floor usage back to the Supplier Invoice.

Validation Logic

• If Component X is scanned → Then Check: Is Component X valid for this BOM?
• If Valid → Then Create Link: INSERT INTO Genealogy (Parent, Child, Time) VALUES (...).

Retention Requirements (Business Rules)

The retention period is dictated by the product class and liability profile, not by disk space.

• Consumer Class: Warranty Period + 1 Year.
• Industrial/Medical: Product Lifecycle + 10 Years (Statute of Repose).
• Aerospace/Automotive: Perpetual (Life of Vehicle).

Rule: The MES must prevent any manual deletion of records that have not met their defined retention policy.

Final Checklist

Category	Metric / Control	Threshold / Rule
Granularity	IPC Level	All Critical Components (CPU, Battery) = Level 3 (Serialized).
Integrity	The 5 Dimensions	Records drop if Who, What, Where, When, or How is missing.
Time	Sync	Timestamps must be UTC and NTP synced.
Linkage	Graph Check	100% of Serial Numbers link to a Work Order.
Suppliers	Inbound	No Lot entering the floor without a Date_Code and Manufacturer record.
Audit	Retrieve Time	"Reverse Genealogy" (Component → Finished Goods) query < 5 minutes.