Characterizing the Soldering Alloy Type Zn-Al-Cu and Study of Ultrasonic Soldering of Al7075/Cu Combination

The aim of the research was to characterize the soldering alloy type Zn-Al-Cu and study the fluxless ultrasonic soldering of the combination of aluminum alloy type Al7075 with copper substrate. The Zn-Al-Cu solder is of the close-to-eutectic type with two phase transformations: the eutectic transformation at 378 degrees C and the eutectoid transformation at 285 degrees C. The solder microstructure is formed of a matrix composed of the solid solutions of aluminum (Al) and zinc (Zn) in which the copper phases CuZn4 and CuAl2 are precipitated. The shear strength of the soldering alloy type Zn5Al with copper addition reaches values from 167 to 187 MPa and it depends on the copper content in the solder. The bond with aluminum alloy type Al7075 is formed due to the solubility of Al in zinc solder at the formation of solid solution Al. Contrary to this observation, the bond with the copper substrate is in this case formed due to the interaction of zinc and aluminum with the copper substrate. Two new intermetallic phases, namely Al(Cu,Zn)(2) and Cu3.2Zn0.7Al4.2, were formed. The average shear strength of Al7075/Zn5Al3Cu/Cu joints attained was 134.5 MPa. For comparison, the Cu/Zn5Al3Cu/Cu joint attained an average shear strength of 136.5 MPa.

Automated summary

The research aimed to characterize the Zn-Al-Cu soldering alloy and study fluxless ultrasonic soldering of Al7075 aluminum alloy with copper substrate. The Zn-Al-Cu solder has a close-to-eutectic type microstructure and two phase transformations. The shear strength of Zn5Al3Cu solder with copper addition depends on the copper content and reaches 167 to 187 MPa for Al7075 joint and 136.5 MPa for Cu joint.