Defect Characterization
Dynamic inspection technique measures the rate of temperature change across a surface to identify internal structural flaws. In the context of electronic assembly, transient thermal imaging detects delamination and poor thermal contact between a component and the board. A brief pulse of energy is applied to the sample and a high-speed infrared camera records the subsequent cooling or heating pattern.
This method reveals hidden defects that are not visible to steady-state thermal scans. Because the heat flow is time-dependent, the resulting data provides a three-dimensional perspective of the internal thermal resistance. Unlike static methods, this approach isolates the properties of the layers rather than the environment.
Capturing the thermal response in real time allows for the precise location of voids in advanced packaging.
Heat Physics
Thermal diffusion through different materials dictates the timing of the observed temperature profile. When using transient thermal imaging, a void in a solder joint acts as a barrier that slows down the flow of heat. This resistance causes a localized temperature difference on the surface that peaks at a specific time after the pulse.
Analysts use the decay curves to calculate the depth and size of the thermal obstruction.
Production Application
Inspection speed and non-destructive nature make this process suitable for high-volume manufacturing. Transient thermal imaging provides a way to verify the integrity of large power semiconductors and heat sinks without mechanical stress. It identifies issues that would lead to premature failure in the field due to thermal fatigue.
The results allow for the adjustment of reflow profiles to improve the quality of the thermal interface.
