Map a Suspect PCB Population Across Stock, Work in Progress, and Shipments

A quality issue may affect boards in several places at once: incoming stock, assembly work in progress, finished goods, and shipments already dispatched. A containment list limited to the original warehouse bin can miss much of the relevant population. Build a traceable map from the suspected cause to current material locations.

Bosch’s problem-solving guidance explicitly includes material in transit and intermediate storage when considering containment. For a particular PCB issue, the actual scope must come from the available traceability and technical evidence.

Define the suspected boundary

Identify the characteristic or event that may connect affected boards: material lot, process period, program revision, equipment condition, or another supported factor. Record what is known and what is only suspected. List the evidence that would permit narrowing the boundary, so later scope reductions have a specific technical basis. Keep the initial boundary conservative enough to accommodate unresolved traceability gaps.

Translate that boundary into board, panel, assembly, and shipment identities as appropriate. One fabrication lot may feed several assembly jobs, and one finished assembly may contain material from several sources. Follow the relevant relationship rather than assuming all identifiers have a one-to-one mapping.

Build a location and status ledger

Reconcile quantities across the ledger, including scrap, consumed samples, and material already reworked. A gap in the total is an investigation item. Do not label it as cleared material simply because it is absent from the current inventory system.

Keep the map current during investigation

1. Identify each affected segment and responsible owner.
2. Record its controlled status and physical location.
3. Track movements and inspection results.
4. Revise the scope when causal evidence changes.
5. Release only the population covered by an explicit disposition.

Separate population identification from the decision about product acceptability. A board can belong to the suspect population yet later be cleared by suitable evidence. Conversely, a board outside an initially narrow list may need inclusion when a traceability assumption proves wrong.

Keep every scope revision with its reason. The final record should explain why material was added, removed, or released, not just show the last spreadsheet state. This makes containment understandable to production teams and supports a later review of whether the affected population was completely accounted for.