Different tests answer different questions
Optical inspection examines visible circuit features. Bare-board electrical testing checks connectivity and isolation against a reference. Neither alone establishes complete mechanical durability or final product function.
Impedance and construction verification
Controlled impedance work needs an agreed target, tolerance, coupon design and measurement method. Cross-sections and dimensional checks can provide evidence about selected construction features. Define sampling and acceptance criteria in the purchase specification.
Flex reliability validation
For moving circuits, specify bend geometry, motion profile, environmental conditions and failure criteria. A representative validation fixture should reproduce the important installed constraints. Do not infer service life from an unrelated bend test.
Close the evidence loop
Link reports and nonconformance records to the part revision and manufacturing lot. Clarify which reports are included with each shipment and which are qualification deliverables. Retain the approved data package so measurements can be interpreted correctly.