4. Conclusions
a) Allthe ultrasonic-treated Cu/SAC305/Cu samples exhibited finer
solder matrix microstructure, thinner interfacial Cu6Sn5 IMC
layer, improved solder matrix hardness and better mechanical
strength as compared to the control sample.
b) By comparing themorphology ofthe phases presentin the solder
matrix,the effect of USV time from 1 s to 6 s was more significant
on the -Sn phase than the eutectic phase.
c) The interfacial Cu6Sn5 IMC layer at the top and bottom
Cu/SAC305 interfaces was generally larger at longer USV time.
The difference of IMC thickness between these two interfaces
was found to increase with USV time.
d) The obtained solder matrix hardness exhibited an increasing
trend with USV time, indicating that the Cu/SAC305/Cu sample
is less ductile when treated with USV at longer duration.
e) The shear strength of the ultrasonic-treated samples was not
affected by the effect of USV time. However, the yield strength
of these samples exhibited a decreasing trend with increasing
USV time from 1 s to 6 s.