Meaning
Degradation processes in electronic components accelerate rapidly as operating temperatures rise. This temperature-dependent acceleration, called thermal activation, occurs when thermal energy overcomes the energy barrier required to trigger a physical or chemical transition. It governs many common failure mechanisms in semiconductor packages and interconnects, such as intermetallic compound growth and atomic diffusion.
By modeling this behavior, engineers can calculate the rate of component degradation under different operating conditions and thermal budgets.
Reaction Rate
Chemical kinetic equations describe how the rate of these thermally driven transitions increases with temperature. The Arrhenius equation dictates that even a slight temperature increase can produce an exponential surge in the rate of thermal activation. This explains why hot spots on a printed circuit board dramatically reduce the local reliability of solder joints and silicon dies.
Managing these temperatures is therefore a primary focus of thermal design.
Solder Joint Degradation
Intermetallic compound growth at the boundary between copper pads and solder alloys is a prime example of this temperature-sensitive process. Over time, thermal activation drives the diffusion of tin and copper atoms, forming brittle layers that weaken the mechanical strength of the joint. In harsh environments like automotive under-hood systems, this growth can lead to early solder cracking under vibrational loads.
Thermal design must limit the maximum temperature of these joints to control this layer growth.
Cooling Consequence
Active and passive cooling solutions reduce the temperature of critical components, lowering the rate of these degradation processes. This thermal mitigation extends the product’s operational life.
