Meaning
Reliability testing procedure involving the continuous exposure of a component to elevated temperatures accelerates the natural degradation of materials. A thermal aging sweep allows engineers to observe the growth of intermetallic layers and the loss of solder joint strength over a compressed timeframe. This process identifies potential long term failures without waiting for years of normal product use.
Degradation Rate
Chemical reactions at the bond interface follow an Arrhenius relationship where higher heat increases the speed of atomic diffusion. During a thermal aging sweep, the circuit board is typically held at one hundred and twenty five degrees Celsius for several hundred hours. This environment causes the intermetallic compounds to thicken, which can eventually lead to a brittle interface that fails under mechanical shock.
Structural Drift
Changes in the grain structure of the solder alloy occur as the metal is held near its melting point. Results from a thermal aging sweep show that the solder becomes softer and more prone to creep as the internal stresses are relieved. This transition can be problematic for joints that must maintain a specific tension to keep a component in place.
Lifetime Estimation
Data gathered from these tests is used to build mathematical models that predict when a product will likely fail in the field. A successful thermal aging sweep provides the evidence needed to guarantee a product for a specific number of years. Manufacturers use these findings to refine their material choices and reflow profiles for better durability.
