Functional Test Fixtures Owned by the Factory or the Buyer
Buyer-owned test fixtures require explicit PO line items, complete source files, and calibrated limit audits to prevent factory lock-in.
Micro-Crack Flexure
Structural Fracture
Material degradation in the form of tiny breaks occurs when a printed circuit board is subjected to excessive bending or twisting. Micro-crack flexure refers to the internal failure of ceramic components, such as multilayer capacitors, caused by the strain of the board substrate. These cracks are often invisible to the naked eye and may not cause an immediate electrical failure.
The phenomenon is measured by the degree of board deflection and stops applying once the mechanical stress is removed.
Strain Mechanism
Ceramic materials are brittle and cannot stretch when the copper and resin layers of the board expand or flex. During micro-crack flexure, the stress concentrates at the solder fillets and pulls the ceramic layers apart. This often happens during the panel de-tabbing process or when a technician manually inserts a board into a tight chassis.
The result is a latent defect that may only appear after the product has been in the field for months. As the board undergoes thermal cycling, the crack can grow until it eventually breaks the circuit. To prevent this, manufacturers use specialized routing tools that minimize the force applied to the board edges.
Inspection Limit
Traditional visual inspection cannot find these internal fractures within the component body. Testing for micro-crack flexure usually requires x-ray analysis or cross-sectional microscopy in a laboratory setting. This identifies the root cause of intermittent failures in high-stress environments.