Speaker
Description
The concept of nanocomposite lead-free solders has provided a promising approach to improve mechanical reliability of solder joint. Minor additions of metal nanoparticles into the commonly used Sn-Ag-Cu solder impact on the morphology of both the solder alloy and solder/Cu joint.
The present research is the follow-up of our previous studies and summarises the influence of nano-sized metal (Co, Ni) and bimetallic (Co-Pd, Ni-Sn) admixtures on structure-sensitive properties of the SAC/Cu solder joints. The samples were produced by cold pressing and by the planar flow casting methods. The electrical conductivity of nanocomposite SAC305 and SAC387 alloys with different percentages of nanoparticles was measured over a wide temperature range of the solid and liquid states. The effects of nanoparticles were investigated by means of DTA, XRD both in the liquid and solid states, and SEM. The DTA data are compared with available literature data to check the capability of minor nano-inclusions to decrease the melting temperature. The combination of structural data in liquid and solid states provided important information about the structural transformations of liquid SAC alloys caused by minor nanoadditions and the phase formation during solidification. The effect of prolonged heat treatment at moderate annealing temperatures on the Cu-Sn IMC thickness of Cu joints prepared with the SAC modified by minor additions of the nano-sized Co, Ni and Ni-Sn powders has been studied. The shear strength data gave information about a relationship between the microstructure and mechanical properties of the solder joints. The growth kinetics of the interfacial Cu-Sn layer was analyzed based on the classical kinetic energy theory by determination of thickness of IMC layer from SEM images of cross-sections of the solder joints. Minor additions of the nano-sized Ni3Sn or Ni3Sn2 particles decreased the growth rate of both Cu6Sn5 and Cu3Sn interfacial layers in the aged SAC305/Cu joint.
| Speaker Country | Ukraine |
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