3.1 NPI Supply Chain: Consignment, Kitting and Attrition

NPI Supply Chain is more than logistics; it is a detailed audit of incoming components. 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 unfiltered mix into the SMT line, efficiency drops as operators are forced to hand-place components. This section defines how to transform an “Engineer’s Desk Kit” into a “Production-Ready Kit.”

Consignment Audit: The “Bag of Parts” Verification

Unlike standard mass production inventory, NPI materials often lack factory-sealed traceability. The Receiving Inspection team must switch from a “Box Checking” mentality to focused “Component Verification.”

1. The “Cut Strip” Risk

Customer-supplied cut tape often lacks the leader necessary to feed into the SMT machine.

• Inspection Rule: Verify the component markings on the physical chip against the BOM, not just the label on the bag. Engineers frequently swap labels during bench testing and 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 in the pocket might be ambiguous or reversed.

2. Handling Moisture Sensitivity (MSL) in Open Bags

NPI parts often arrive in opened or compromised bags.

• The “Reset” Protocol: When an MSL component (Level 3 or higher) arrives in a non-vacuum sealed bag or without a valid humidity indicator card, you should bake the components (typically at 125°C for 24-48 hours) before reflow. This prevents moisture from rapidly expanding and cracking the component during the reflow process (“Popcorning”). Avoid assuming opened parts are safe to solder without validation.

NPI Attrition: The “Rule of 5”

Standard percentage-based attrition (e.g., a “1% scrap allowance”) is less effective during low-volume builds. 1% of a 10-unit build is 0.1 components. If the SMT nozzle drops a single part, you cannot finish the build.

The NPI Overage Standard

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

• Passives (0402 - 1206): Build Qty + 50 pieces (or a minimum 100mm strip).
  • Reasoning: Feeders require a section of “waste” leader tape to advance the components to the pick point.
• Active ICs (Standard): Build Qty + 5 pieces.
  • Reasoning: This allowance covers 1-2 feeder mispicks and 1-2 potential QC rework failures.
• Expensive ICs / BGAs: Build Qty + 1 piece (or 0 if manual placement is authorized).
  • The Constraint: If you supply zero overage, the Project Manager must authorize “Manual Load” via a Tray feeder or direct hand placement to avoid the risk of a machine dropping your only component.

Making “Cut Tape” Machine Ready

SMT machines cannot pick the very last few inches of a cut strip. Sending raw, short strips to the line forces operators to hand-place the remaining parts, which slows down the cycle time.

The Splicing Guideline:

• Condition: When the supplied strip is shorter than the minimum feeder engagement length, the Kitting Department must attach a Leader Extender or splice the strip onto a standard carrier reel.
• Avoid: Do not tape components to a sheet of paper or use standard office tape to send them to the line. This cannot be processed by the SMT equipment.

Managing Shortages & DNI (Do Not Install)

NPI BOMs are highly fluid. “Missing” parts might actually be intentional “DNI” locations, or they might be critical shortages that halt production.

1. The DNI Validation

• Action: The Kitting list must be cross-referenced against the latest BOM revision immediately before it is released to the floor.
• Visual Aid: Mark DNI locations on the assembly drawing (or flag them in the AOI machine program) so inspectors do not incorrectly report them as “Missing Components.”

2. The “Risk Release” Protocol

Can you build a board with missing parts? Follow this protocol:

• Green Release: The Kit is 100% complete. Proceed with the standard flow.
• Yellow Release (Post-Process Shortage): The missing part is non-critical for the initial reflow cycle (e.g., a mechanical screw, a heatsink, or a hand-soldered connector).
  • Action: Proceed with SMT. Label the batch as “Incomplete - Missing [Part#].”
• Red Release (SMT Shortage): The missing part is a primary reflow component (like an IC).
  • Decision: Hold. Avoid building “partial” boards with the intention of running them through the reflow oven a second time later. Secondary reflow cycles can degrade the PCB laminate and existing solder joints.
  • Exception: If the missing part is a simple 2-pin passive component located on the edge of the board, a “Stop-Build” waiver may be signed by engineering to allow hand-soldering that specific part later.

Final Baseline Checklist

Control Point	Critical Requirement
Passives Overage	Build Qty + 50 pcs (or ensuring sufficient leader length).
Active Overage	Build Qty + 5 pcs (Minimum).
Zero Overage	Requires Manual Tray/Placement authorization.
Consignment Check	Verify the MPN directly on the Chip Body, not just the Bag Label.
MSL Reset	Bake all loose/open MSL-sensitive parts before SMT to prevent Popcorning.
Cut Tape Prep	Must include a Leader Extender/Splice for reliable machine feeding.
DNI Status	Clearly marked on the Pick List to prevent false shortage alarms during AOI.
Partial Build Rules	Allowed only if the missing part is a Hand-Load/Mechanical item; Avoid for SMT reflow components.