Optical Mapping
Non-destructive optical testing captures full-field surface deformation maps of electronic assemblies during mechanical and thermal stress testing. Industry laboratories employ digital image correlation to track contrast speckle patterns on printed circuit boards during temperature cycling. High-resolution digital cameras record sequential images as test specimens undergo mechanical bending or thermal expansion.
Computer algorithms compare consecutive image sub-regions to quantify displacement vectors across the entire target area.
Strain Computation
Mathematical cross-correlation of intensity patterns calculates local displacement fields across the active field of view. Software algorithms divide the specimen surface into small sub-sets to track movement with sub-pixel spatial accuracy. Spatial differentiation of these displacement fields yields full-field strain distributions across components and substrate laminates.
Highly localized strain gradients appear clearly near component corners where CTE mismatch induces severe shearing stresses. Real-time deformation mapping identifies out-of-plane warping and localized strain accumulation without attaching physical strain gauges. Thermally induced strain maps validate finite element analysis models by providing direct experimental boundary conditions.
Continuous image capture during reflow profiling reveals exact temperatures where peak warping occurs across ball grid array packages.
Resolution Margin
Measurement fidelity depends on speckle pattern contrast and optical sensor resolution. High-magnification optical setups achieve spatial displacement resolution down to fifty nanometers across miniature surface mount interconnects.
