Tin-based solder alloys are used in microelectronic packaging to interconnect components with the copper base material.Excessive growth and coarsening of the intermetallics,particularly those of copper and tin,can result in a severe degradation of the solder joint mechanical performance.To limit the intermetallics growth,a diffusion barrier is introduced between the solder alloy and copper.The need for diffusion barriers has recently become of major concern as a consequence of the perspective banning of lead-containing solder alloys.Tin-silver-copper and tin-silver-bismuth alloys are the candidate alternative to the commonly used eutectic tin-lead alloy.Moreover,to maintain the joint reliability requirements,the electronic industry must try to develop new processes consistent with lead-free alloys improving the mechanical properties of such solders.
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