Influence of the Process Parameters on the Properties of Cu-Cu Ultrasonic Welds

Abstract

Ultrasonic welding (USW) is a solid-state welding process based on the application of high frequency vibration energy to the workpiece to produce the internal friction between the faying surface and the local heat generation required to promote the joining. The short welding time and the low heat input, the absence of fumes, sparks or flames, and the automation capacity make it particularly interesting for several fields, such as electrical/electronic, automotive, aerospace, appliance, and medical products industries. The main problems that those industries have to face are related to the poor weld quality due the improper selection of weld parameters. In the present work, 0.3 mm thick copper sheets were joined by USW varying the welding time, pressure, and vibration amplitude. The influence of the process variables on the characteristics of the joints and weld strength is investigated by using the analysis of variance. The results of the present work indicate that welding time is the main factor affecting the energy absorbed during the welding, followed by the pressure and amplitude. The shear strength, on the other hand, resulted mostly influenced by the amplitude, while the other parameters have a limited effect. Regardless the welding configuration adopted, most welds registered a failure load higher than the base material pointing out the feasibility of the USW process to join copper sheets.

Determination of proper parameters for ultrasonic welding of copper plate with copper wire strands

“…Based on the literature survey [14]- [16], the predominant process variables such as clamping pressure, amplitude of vibration of the sonotrode, weld time, and weld specimen part dimensions are considered for experimentation. In our experiment, we determined three parameters have the most influence on the quality of the weld: pressure, amplitude, and energy.…”

Local Plastic Deformation and Quality of Cu-Cu Joints Obtained by Ultrasonic Welding

“…Most frequently, ultrasonically welded samples exhibit a shear strength that is less than 50% of the shear strength of the parent metal, and its values show a large scatter [1,3,4,6,[17][18][19][20]. In addition, as Muller et al [17] noted, the USW process "is prone to a large number of disturbances, leading to fluctuating joint quality without apparent change of boundary conditions".…”

“…Therefore, USW parameters are determined experimentally. Based on the data obtained, numerous attempts have been made to optimize the USW parameters [3,9,[17][18][19][20] so that the temperature and deformation at the interface required for the formation of a metallic bond are achieved in a short time, and a joint with high strength is obtained.…”

“…An increase in both of these parameters to optimum values leads to an increase in the strength of joints [1][2][3][4][5][6]. However, long-term USW under the action of a large clamping force leads to excessive penetration of the ridges of the tip and anvil into the sheets to be joined and their thinning [8][9][10][11][12][13][20][21][22][23]. In such cases, the failure of joints occurs by the pull-out mode taking place in the thinnest, "weakest" section of a sheet under stress, which is less than the actual strength of the joint.…”