6.7 Shelf-life, lot traceability & recall readiness

Granular traceability provides essential risk mitigation. In the event of a supplier component recall or a field failure, detailed traceability allows you to identify and isolate only the specific affected products, rather than conducting a blanket recall of an entire production run. The granularity of your warehouse data directly determines your ability to manage quality incidents efficiently.

The scope of control (tiered traceability)

The level of traceability required must be determined based on component criticality and chemical volatility, rather than applying the highest level of control to every item.

• Tier 1 (Deep Lot Control):
  • Active Silicon: ICs, Custom Modules, Sensors (Track Manufacturer Date Code & Lot Code).
  • Process Chemistry: SMT Solder Paste, Wave Flux, Structural Adhesives, Conformal Coating (Track Batch ID + Expiration Date).
  • Safety Critical Hardware: Lithium Batteries, High-Voltage capacitors.
• Tier 2 (Batch Level Visibility):
  • Standard Passives (Resistors/Caps) from approved manufacturers.
• Tier 3 (Commodity Flow):
  • Standard mechanical hardware (screws, standoffs). Standard FIFO (First-In, First-Out) is usually sufficient unless specific industry regulations (like AS9100 or ISO13485) require otherwise.

FEFO logic (first expired, first out)

For shelf-life sensitive materials and chemicals, FEFO must be implemented rather than relying solely on FIFO.

• The Guideline: The WMS/ERP system should allocate physical stock based on the Expiration Date, not the receipt date.
• The Execution: If Batch A (Expires Jan 1st) is received today, but Batch B (Expires Feb 1st) is already in stock, the system should prompt the picking of Batch A first.
• The Expiry Lockout: The ERP should prevent the picking of any lot that has exceeded its expiration date, ideally triggering a warning on the operator’s RF scanner.

Data capture points (the chain of custody)

Traceability relies on consistent data capture at every handling node.

1. At Receipt (Data Input):
   • The Manufacturer Lot Number and the Date Code (DC) must be recorded into the ERP.
   • The Expiration Date for all chemical materials must be recorded.
   • The Protocol: Mixing different supplier lots in the same physical bin must be avoided unless they are clearly segregated and individually tracked.
2. At Issue (The Digital Link):
   • The specific Reel Lot Number must be scanned against the active Work Order (WO) during kitting.
   • The Split Protocol: If issuing a partial reel, it must be ensured the system records which specific split went to which specific Work Order.
3. On Line (Consumption):
   • For SMT: The feeder setup validation system should link the specific Reel ID to the exact feeder slot on the Pick & Place machine.
   • For Chemicals: Operators should scan the paste jar/cartridge ID against the Work Order before applying it to the stencil.

Shelf-life governance

Component solderability and process chemistry degrade over time. Shelf-life limitations must be closely monitored and adhered to.

• Component Date Codes:
  • Standard industry practice typically limits active component age to 2 Years.
  • The Protocol: If the age exceeds the limit, the material should be held. Extending the shelf life generally requires formal solderability testing (per IPC/JEDEC standards) by a lab; visual inspection alone is usually insufficient.
• Process Chemicals (Solder Paste/Adhesives):
  • The Expiry Rule: Once the calendar expiration date passes, the chemical flux activity or polymer stability is compromised.
  • The Disposal: Expired process chemicals must be treated properly, often requiring specialized disposal as Hazardous Waste. Using expired solder paste based on a “quick test print” must be avoided, as the underlying chemistry may be degraded.

The mock recall drill

The traceability system must be regularly tested to ensure data accuracy and retrieval speed.

• The Exercise: Periodically (e.g. every 6 months) select a random Lot ID from a component received several months prior.
• The Target: Attempt to trace the component’s full history within a set timeframe (e.g. 4 hours).
• The Output: The resulting report should identify:
  1. Which Work Orders consumed that specific lot.
  2. Which Finished Good Serial Numbers contain that lot.
  3. The current geographical location of those Serial Numbers (e.g. WIP, Finished Goods, or Shipped to a specific customer).
• The Evaluation: The results must be used to identify and close gaps in the traceability process.

Final Checkout: Shelf-life, lot traceability & recall readiness

Control Point	Process Requirement	Operational Impact
Receipt Data	Lot Code and Date Code are captured for Tier 1 materials.	Enables containment of defective parts.
FEFO Logic	Material with the earliest expiration is picked first.	Prevents chemical materials from expiring unnecessarily in storage.
System Block	The WMS prevents picking of expired items.	Prevents the use of compromised adhesives or solder pastes.
Chemical Tracking	Track Solder Paste/Flux with the same rigor as active components.	Helps prevent widespread weak solder joints.
Extension Rules	Extensions require formal testing, not just visual checks.	Maintains reliability in the SMT reflow soldering process.
Digital Linkage	Ensure a 1-to-1 link between Lot ID and the consuming Work Order.	Facilitates fast, surgical recalls when required.