1.6 Engineering Queries, ECO and Deviation Control

Informal agreements via instant messaging, email threads, or verbal confirmations are non-existent during a liability dispute. Ambiguity in the Golden Data Pack leads to production stops, scrap, or latent field failures. A formal Engineering Query (EQ) process converts ambiguity into a traceable, contractual manufacturing specification and ensures the "As-Built" configuration matches the "As-Approved" documentation.

The EQ Workflow

The Engineering Query is the primary mechanism to resolve discrepancies between the documentation (BOM, Gerbers, Assembly Drawings) and the physical reality of manufacturing.

1. Initiation & Definition

Do not raise open-ended questions. An EQ must drive a decision.

• Problem Statement: Clearly identify the discrepancy. Reference specific component designators (e.g., R45), file names, and revision levels.
• Evidence: Attach screen captures, photos of physical fitment issues, or conflicting datasheet excerpts.
• Proposed Disposition: Engineering must propose a technical solution based on DFM analysis. Do not ask "What should we do?"; ask "Is X acceptable to resolve Y?"

2. Disposition Logic

Categorize the resolution based on impact to form, fit, function, and longevity.

• If the query resolves an ambiguity in documentation without changing the physical product (e.g., clarifying text orientation), Then disposition is Clarification / Update Documentation.
• If the material is non-compliant but functionally acceptable for a specific quantity (e.g., alternative capacitor brand due to shortage), Then disposition is Deviation (Concession).
• If the product requires additional processing to meet the specification (e.g., manual soldering of a lifted pad), Then disposition is Rework.
• If the design is fundamentally flawed and requires a permanent change to the Golden Data Pack (e.g., wrong footprint for a connector), Then disposition is Engineering Change Order (ECO).
• If the issue poses a safety risk or unrecoverable functional failure, Then disposition is Stop-Build.

Pro-Tip: Always include a specific "Effective From" date or Serial Number range in the disposition. An open-ended approval implies a permanent design change, which requires an ECO, not just an EQ.

ECO vs. Deviation Control

Distinguish between temporary allowances and permanent changes to maintain configuration control.

Deviation (Temporary)

Use a Deviation to authorize a departure from the established requirements for a specific number of units or a specific time period.

• Scope: Limited to a specific Batch ID or Date Code.
• Expiration: The authorization automatically expires once the limit is reached.
• Traceability: The deviation number must be recorded in the device history record of affected units.

Engineering Change Order (Permanent)

Use an ECO to permanently alter the Golden Data Pack.

• Scope: Applies to all future production builds until the next revision.
• Requirement: Requires a revision roll of the top-level assembly or affected sub-assemblies.
• Implementation: Must define cut-in strategy (e.g., "Scrap old stock," "Rework old stock," or "Running change").

Final Checklist