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.
Nickel Trace Addition
Meaning
Chemical modifications involving the introduction of small quantities of nickel into lead-free solder alloys refine the grain size and improve the stability of the joint. Using nickel trace addition prevents the excessive growth of intermetallic compounds at the interface of the joint and the copper substrate. This process enhances the resistance of the solder to thermal fatigue and reduces the dissolution of the copper pads during the soldering process.
It is a common technique used to improve the performance of standard tin-silver-copper alloys in high-reliability applications.
Grain Refinement
The presence of nickel atoms in the molten alloy provides nucleation sites that lead to a smaller and more uniform grain structure upon cooling. This effect of nickel trace addition makes the resulting solid metal more resistant to the stresses of thermal expansion and contraction.
Intermetallic Growth
Controlling the chemical reaction between the tin and the copper is necessary for long-term reliability.
Thermal Stability
Joints modified with these trace amounts maintain their mechanical properties even after being exposed to high temperatures for extended periods. This stability is particularly beneficial for electronics used in automotive engine compartments or industrial power supplies. Procurement specifications often mandate the inclusion of these dopants to ensure the longevity of the final assembly.
The cost of the additive is minimal compared to the gain in mechanical durability.