I needed a simplified definition of thermal stress in semiconductors, to understand the braking of crystallizing thin film when heated at certain temperatures.
Residual stress is a process-induced stress, frozen in a molded part, that exists in a body in the absence of external loading or thermal gradients. In a structural material or component, residual stresses exist in the object without the application of services or other external loads. They affect a part similarly to externally applied stresses.
As said M. Abdelnabi Ali, your component does have residual stresses induced during the producing process of your component. It is also present at room temperature.
Moreover if you heat your component, thermal stresses are added and develop between the different materials composing your semiconductor. These thermal stresses are due to different thermal expansion coefficients between each single material.
Arnaud Magnier's answer is correct. I can elaborate, since there are other types of thermal stress.
An unconstrained specimen of a single material heated uniformly* will have no thermal stress. There are three common ways to get thermal stress:
1. There are multiple materials with different thermal expansion or the specimen is otherwise heterogeneous. This was the previous answer.
2. An unconstrained specimen of one material is heated non-uniformly. That will also cause thermal stress.
3. Constrain the specimen when heating.
There are more subtle details and special cases, but those three cases or combinations of them cover the main practical situations.
*In fact, if heated with temperatures that vary linearly through the specimen there will also be no thermal stress.
In my previous answer I read the text, which says "thermal stress," not the title which says "thermal residual stress."
If you restrict the question to residual thermal stress, and Abdelnabi Ali defines residual well above, then those come from differential thermal expansion of multiple materials when cooling from some processing temperature.
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