Meaning
Reliability assessment protocols subject electronic assemblies to alternating high and low temperatures to identify potential mechanical failures. A thermal cycling test accelerates the effects of long-term environmental exposure by forcing the materials to expand and contract repeatedly. This process is used to validate the durability of solder joints and the adhesion of protective coatings.
Fatigue Loading
Repeated mechanical stress caused by temperature changes can lead to the growth of cracks in the metallic interconnects. During a thermal cycling test, the assembly moves between two temperature extremes at a controlled rate. The goal is to induce failures in the laboratory that would otherwise take years to occur in the field.
Temperature Ramp
The speed at which the temperature changes affects the type of stress applied to the components. A typical thermal cycling test specifies the soak time at each extreme and the transition time between them. Managing these parameters ensures that the entire mass of the product reaches the target temperature without causing unnecessary thermal shock.
Failure Identification
Post-test inspection uses electrical checks and cross-sectioning to find any hidden damage within the layers of the board. The results of a thermal cycling test help engineers to choose better material combinations for the enclosure and the substrate. Successfully passing this evaluation is a common requirement for the qualification of modules in the automotive and aerospace industries.
