Accelerated Thermal Cycling

Strain Rate Dynamics

Rapid temperature shifts generate transient thermal gradients across complex assemblies that amplify local mechanical shear. During accelerated thermal cycling, differential expansion between copper plating and organic resin matrices causes microvia barrel cracking or corner cracked vias. The rate of temperature change dictates whether mechanical fatigue or creep damage dominates the degradation path.

Creep Saturation Limit

Dwell times extended beyond thirty minutes yield diminishing fatigue acceleration because solder strain relaxation reaches completion. Excessively steep thermal ramps introduce unrealistically high thermal shocks that trigger delamination modes absent during field operation. Qualification thresholds require continuous resistance monitoring during thermal testing to capture transient open circuits before cooling reseals cracks.