3.1 NPI Supply Chain: Consignment, Kitting and Attrition

NPI Supply Chain is not about moving pallets; it is about forensic auditing. In the prototype phase, materials often arrive as "Consignment" (customer-supplied), consisting of loose cut tape, non-standard labels, and last-minute BOM changes. If you feed this raw chaos into the SMT line, machine utilization drops to near zero as operators hand-place components. This chapter defines how to transform a "Engineer’s Desk Kit" into a "Production-Ready Kit."

Consignment Audit: The "Bag of Parts" Verification

Unlike production inventory, NPI materials often lack factory-sealed traceability. The Receiving Inspection must switch from "Box Checking" to "Component Verification."

1. The "Cut Strip" Risk

Customer-supplied cut tape often lacks the leader necessary for the feeder.

• Inspection Rule: Verify the component markings on the physical chip against the BOM, not just the label on the Ziploc bag. Labels are often swapped by engineers during sampling.
• Polarity Check: For diodes and ICs on cut tape, verify the tape orientation matches the standard (Pin 1 quadrant). If the strip was manually cut from a larger reel, the orientation might be ambiguous.

2. Handling Moisture Sensitivity (MSD) in Open Bags

NPI parts often arrive in opened bags.

• The "Reset" Rule: If an MSD component (Level 3+) arrives in a non-vacuum sealed bag or without a humidity card, Then you must bake the components (typically 125°C for 24-48 hours) before reflow to prevent "Popcorning." Do not assume they are safe.

NPI Attrition: The "Rule of 5"

Standard percentage-based attrition (e.g., "1% scrap allowance") fails in low-volume builds. 1% of a 10-unit build is 0.1 components. If you drop one, you cannot finish the build.

The NPI Overage Standard:

You must demand (or purchase) excess material based on absolute integers, not percentages.

• Passives (0402 - 1206): Build Qty + 50 pieces (or min 100mm strip).
  • Reasoning: Feeders require a "waste" leader to advance the tape to the pick point.
• Active ICs (Cheap): Build Qty + 5 pieces.
  • Reasoning: Allows for 1-2 feeder mispicks and 1-2 QC failures.
• Expensive ICs / BGAs: Build Qty + 1 piece (or 0 if Manual Placement is authorized).
  • Constraint: If you have zero overage, the Project Manager must authorize "Manual Load" (Tray feeder) or placement by hand to avoid machine reject risk.

Making "Cut Tape" Machine Ready

Machines cannot pick the last few inches of a cut strip. Sending raw strips to the line forces operators to hand-place parts, destroying cycle time.

The Splicing Mandate:

• Condition: If the supplied strip is shorter than the feeder engagement length, Then the Kitting Department must attach a Leader Extender (dummy tape) or splice it onto a carrier reel.
• Prohibited: Do not tape components to a sheet of paper and send them to the line. This is un-manufacturable.

Managing Shortages & DNI (Do Not Install)

NPI BOMs are fluid. "Missing" parts might actually be "DNI," or they might be critical shortages.

1. The DNI Validation

• Action: The Kit must be cross-referenced against the latest BOM revision immediately before release.
• Visual Aid: Mark DNI locations on the assembly drawing (or use the AOI machine to flag them) so inspectors do not report them as "Missing Components."

2. The "Risk Release" Protocol

Can you build with missing parts?

• Green Release: Kit is 100% Complete. Standard flow.
• Yellow Release (Post-Process Shortage): The missing part is non-critical for reflow (e.g., a mechanical screw or a hand-solder connector).
  • Action: Proceed with SMT. Label the batch "Incomplete - Missing [Part#]."
• Red Release (SMT Shortage): The missing part is a reflow component.
  • Decision: Stop. Do not build "partial" boards and try to reflow the missing part later. Secondary reflow cycles degrade the PCB and existing joints.
  • Exception: If the part is a simple 2-pin passive on the edge of the board, a "Stop-Build" waiver may be signed to allow hand-soldering later.

Final Checklist