4.6 Change control and deviations

The “Golden Process” validated during the initial qualification phase logically represents the exclusively approved method for manufacturing a part. Any variation from this established baseline—whether intentional (managed via a Change Request) or accidental (handled as a Deviation)—introduces significant unknown variables into the final product. A “No Surprises” policy must be operated under: suppliers cannot alter the “4M” variables (Man, Machine, Material, Method) without prior, formal written approval. History repeatedly shows that uncontrolled change in the supply chain is the primary driver of severe field failures.

Supplier change control (PCN)

A Process Change Notification (PCN) is not merely an “FYI” email sent late on a Friday; it is a formal request from the supplier to modify the commercial and technical contract for a permanent process shift.

Trigger Events (What Requires a PCN?):

Material changes: Using a new resin grade, switching to a different solder paste type, or changing a sub-tier raw material source.
Machine changes: Implementing a new mold, transferring production to a new SMT line, or replacing a critical reflow oven.
Method changes: Altering cure time/temperature, changing inspection logic, or aggressively updating critical test software.
Location changes: Moving production to a new building or to an entirely different geographic region.

The 90-Day Rule:

Suppliers are generally required to formally issue a PCN at least 90 days prior to their planned implementation date. This mandatory window is not arbitrary; it allows the engineering team the necessary time for:

Risk Assessment: Reviewing and updating the internal FMEA to account for the new supplier variables.
Validation: Asking the supplier to run a new Cₚₖ study and executing a 3-Lot Safe Launch program (involving 100% Inspection at IQC) to prove the new process is stable.
Approval: Securing formal sign-off from both Engineering and Quality teams. Silence is NEVER implied approval for a supplier to proceed.

Deviation and concession control

A Deviation is a temporary, conditionally approved permission to deviate from the established specification. It is essentially a short-term allowance that comes with a very firm expiration date. It should be utilized pragmatically to keep the production line moving during a minor crisis, not used as a loophole to permanently lower quality standards.

Decision Logic:

When the defect impacts Safety or Regulatory compliance, the deviation is Denied. There are zero exceptions to this rule.
When the defect marginally impacts functional performance, Conditional Approval may be granted (This requires 100% screening at the Supplier’s expense to secure only the clean parts).
When the defect is purely cosmetic (e.g. a slight color shift), a Concession may be granted (This is approved against signed Limit Samples, and is often accompanied by a commercial discount from the supplier).

Binding Constraints:

Time/Quantity Bound: Every approved deviation must have a hard stop clearly defined (e.g. “Approved for a maximum of 500 units” or “Expires on 01-Nov”).
Visual Flag: Every physical box shipped under an active deviation must be prominently labeled (e.g. “DEVIATION #XXXX”) in high-visibility neon or bold text so the receiving dock knows what to expect.
Expiry: Once the stated limit is reached, the permission automatically revokes. Any subsequent shipments bearing the defect will be swiftly rejected at Incoming Quality Control (IQC).

Unauthorized changes (the “silent killer”)

Altering a validated process without notification is a fundamental breach of contract and an act of extreme engineering negligence by the supplier.

Examples of “Silent Changes”:

Introducing “Regrind” (recycled plastic) > 20% into the molding process to save cost without explicit approval.
Swapping a specified, brand-name capacitor for a “cheaper equivalent” without submitting validation testing to prove it performs identically under load.
Skipping or truncating a mandatory thermal cure cycle simply to speed up their production throughput.

Consequences of Silent Changes:

Immediate Business Hold: The supplier’s status is instantly downgraded to “Do Not Source” for any new projects until trust is re-established.
Liability: The supplier must legally assume 100% liability for all subsequent validation costs, expensive field recall operations, and the resulting scrap.
Audit: A mandatory “For Cause” on-site audit is mobilized to aggressively re-qualify their entire manufacturing line from scratch.

Final Checkout: Change control and deviations

Control Point	Guiding Principle
PCN Timeline	Ninety Days prior to the physical change are expected. “Retroactive” PCNs are not accepted.
Sub-Tier Lock	It must be ensured changes at sub-tier suppliers are controlled. The Prime Supplier fully owns the quality of their own supply chain.
Deviation Scope	Deviations must always be bound by a specific Quantity or Date. Open-ended deviations are risky and void.
Traceability	A Deviation Label affixed to the exterior Box is required. No exterior label = Immediate rejection at the Dock.
Validation	Hard data must objectively prove equivalence. It must be remembered that “We think it’s okay” is an opinion, not engineering data.