Meaning
Thermal distribution across a printed circuit assembly often exhibits directional temperature variation between different points on the board. This spatial temperature gradient arises from the uneven distribution of heat-generating components and non-uniform thermal dissipation paths. It induces localized mechanical stresses due to differential expansion and can degrade the accuracy of temperature-sensitive components like reference oscillators.
The effect is analyzed across the surface area of the circuit board under maximum load conditions.
Thermal Stress
Mechanical tension accumulates in multi-layer boards when adjacent regions experience different temperatures. The spatial temperature gradient generates shear stresses at the interfaces between the layers of the substrate. This can lead to solder joint fatigue or copper trace failure over repeated thermal cycles.
Designers use continuous ground planes to distribute heat and minimize these localized stresses.
Sensor Calibration
Frequency stability in reference oscillators depends on uniform temperature across the package. If a spatial temperature gradient exists between the crystal and the temperature sensor, the frequency correction algorithm receives inaccurate data. This mismatch causes frequency drift and degrades receiver performance.
Position of the sensor relative to the heat source is finalized during board layout.
Infrared Evaluation
Thermal imaging is used to map the board surface and identify severe temperature differentials. This scan ensures the design limits hotspots and maintains gradients within acceptable ranges.
