Modeling Kirkendall Vacancy Flux in Ternary SAC Solder Interfaces
Modelling vacancy transport in ternary SAC interfaces enables precise prediction of Kirkendall microvoid growth, preventing latent failure in high-reliability packaging.
Ternary SAC Alloys
Meaning
Metal alloys measured against their melting points and mechanical properties define the global standard for high-reliability lead-free electronics assembly. Most modern devices utilize ternary sac alloys to achieve a reliable electrical connection without using lead, mercury or cadmium. These compositions consist of tin, silver, copper and trace additives that improve the wetting behavior of the molten metal.
They are selected for their balance of thermal resistance and processing ease in high-speed production lines.
Melting Point
The temperature at which the alloy becomes fully liquid is typically between two hundred and seventeen and two hundred and twenty degrees Celsius. Using ternary sac alloys requires reflow ovens to operate at higher temperatures than those used for older tin-lead systems.
Mechanical Strength
The addition of silver increases the hardness and the fatigue life of the joint compared to pure tin.
Wetting Performance
Copper is included in the mix to slow down the dissolution of the copper pads on the circuit board during the soldering process. This chemical balance ensures that the solder spreads evenly over the pads and creates a smooth fillet. Procurement teams must verify the silver content of the alloy because it is the most expensive component and directly influences the cost of the raw material.
Each batch is tested for purity to ensure that no contaminants are present that could weaken the final joint.