warpage

Warpage refers to permanent distortion of a component away from its nominal geometry, typically caused by internal stresses and nonuniform temperature, moisture, or chemical changes during fabrication or service. It can manifest as bowing, twisting, or camber and may compromise fit, function, or appearance.

Warpage is common across many materials, including plastics (injection-molded parts and thermoformed sheets), metals (castings, weldments, forgings, and heat-treated items), ceramics and glass, composites, and printed circuit boards. In these contexts, warpage can arise from uneven shrinkage, differential cooling, or anisotropic material behavior, leading to localized or global geometry changes.

Causes of warpage include residual stresses from forming, curing, or welding; thermal gradients during processing; moisture uptake or chemical shrinkage; mismatches in thermal expansion or stiffness between bonded layers; and external constraints or unloading conditions after fabrication. The specific mechanism depends on the material system and processing history.

Effects and measurement: Warpage can cause dimensional inaccuracy, misalignment of assemblies, leaks, or functional failures. It is measured with metrology tools such as coordinate measuring machines, optical profilometry, laser scanning, or micrometer-based methods, often expressed as an amount of deformation in millimeters or as an angle of distortion (warp angle). In electronics, PCB warpage can lead to solder joint issues or component damage.

Prevention and control: Strategies include design for manufacturability, balanced materials and tooling, controlled cooling and temperature profiles, stress-relief heat treatments or annealing, proper fixturing during processing, and post-processing flattening or straightening when feasible. Process optimization aims to minimize residual stresses and ensure dimensional stability.