Defect Description

Warpage is the out-of-plane deformation of an artifact (printed wiring board) caused by non-homogenous shrinkage or expansion of elements composing the artifact [1].

Defect Formation Process(s)

During fabrication, solder masking and reflow soldering process, residual stresses caused by coefficient of thermal expansion (CTE) mismatch between different board materials combined with thermo-mechanical effects can result in board warpage [2-3].

List of Tests to Precipitate this Defect

Failure Acceleration

Likelihood to Precipitate this Defect (condition)

Failure Mechanism(s)

Thermal Shock

• Thermal shock overstresses of weak solder joints resulting from automated component placement or insertion on a warped board [3]

• Cyclic thermal mechanical stress causes fatigue cracking of solder joints due to deflections of board over temperature swings [4].

Mechanical fatigue/ overstress

Combined Environment

• Same as Thermal Shock