What Sensor Calibration Is and Why Readings Drift
Calibration maps sensor error against traceable standards, while drift stems from physical aging, mechanical strain, and environmental stress over time.
Thermal Packaging Stress
Mechanical Tension
Semiconductor assemblies consist of multiple materials such as silicon, copper, gold and epoxy that are bonded together. Thermal packaging stress arises during the cooling phase of the manufacturing process or during normal operation when these materials expand at different rates.
Reliability Impact
The mismatch in the coefficient of thermal expansion creates forces that can lead to the cracking of the die or the shearing of wire bonds. Because thermal packaging stress concentrates at the corners of the chip, manufacturers often use specialized underfill materials to distribute the load more evenly. If the stress is too high, it can also cause the silicon to warp, which changes the electrical characteristics of sensitive analog components and leads to measurement drift.
Design Mitigation
Selecting materials with matched expansion rates reduces the risk of latent defects in the field. Simulation tools help engineers predict where thermal packaging stress will be most severe so they can modify the layout before production begins.
Lifecycle Failure
Repeated heating and cooling cycles during the life of the product can cause these stresses to fatigue the solder joints. Understanding thermal packaging stress is essential for designing electronics that must survive the harsh environments of the automotive or aerospace industries.