Thermal Hysteresis and the Settling Time Nobody Budgets
Unbudgeted sensor thermal settling times and hysteresis generate severe measurement errors, demanding mandatory package-level soak protocols to preserve field accuracy.
Thermal Contact Resistance
Interface Impedance
Thermal flow across the boundary between two solid surfaces is impeded by the imperfect alignment of their microscopic structures. The term thermal contact resistance refers to the temperature drop that occurs across this joint when heat is transferred from one material to another. This resistance exists because the actual contact area is only a small fraction of the apparent area, with the remaining spaces being filled by air.
This air layer acts as an insulator, reducing the efficiency of the heat transfer.
Surface Roughness
Microscopic peaks and valleys on the surfaces of metals and plastics prevent flat contact. High surface roughness increases the thermal contact resistance because it reduces the number of contact points and increases the volume of the insulating air gaps. Fine machining or polishing of the surfaces can minimize this effect.
Mitigation Material
Intermediate substances such as thermal grease, phase-change compounds, or pads are applied to fill these microscopic gaps. These materials have a higher thermal conductivity than air, which significantly reduces the thermal contact resistance and improves the heat dissipation from the component.
Contact Pressure
Increasing the force holding the two surfaces together deforms the surface peaks and increases the contact area. This reduces the size of the air gaps and improves the thermal conductivity of the interface.