Fatigue Life
Mathematical relationships between plastic strain and fatigue cycles provide a model for solder joint reliability. Structural analysis uses coffin-manson mechanics to predict how many thermal cycles a board assembly can survive before a crack forms. This formula accounts for the displacement caused by the different expansion rates of components and the substrate.
Accuracy in this model requires precise data on the material properties of the solder alloy.
Thermal Strain
Temperature fluctuations induce mechanical stress as the metal and laminate expand at different rates. Engineers apply coffin-manson mechanics to evaluate the impact of power cycling on surface mount devices. This approach calculates the damage accumulated in each cycle.
Such calculations help designers choose materials that minimize the risk of early failure.
Predictive Reliability
Long-term stability of a circuit board depends on the durability of its interconnections. Simulations based on coffin-manson mechanics allow manufacturers to estimate the lifetime of a product without running a five-year test. These results guide the selection of underfill or stiffeners to reduce the load on vulnerable joints.
The model is a standard tool for qualifying boards in aerospace or automotive applications. Reliable predictions prevent field returns by identifying weak points during the design phase.
