Ultrasonic Welding of Soft Polymer and Metal: A Preliminary Study

Abstract

Joining soft polymers and metals is receiving increasing attention in both industry and academia to enable the manufacturing of innovative products. One motivation arises from the production of next-generation heat exchanges, the structure of which is primarily composed of polymers and metals. Waste heat coming from low temperature exhaust gas stream is significant in industries in the U.S. However, traditional heat exchangers that are available to recover heat in the presence of small temperature difference are large and costly, restricting the wide application of such heat exchangers. To address this challenge, a hybrid materials design is proposed to achieve a balance between thermal conductivity and mechanical strength. High quality requirement induced by the changing operating conditions necessitates a strong bonding between polymers and copper. In this research, the possibility of using ultrasonic welding, which is conventionally employed to join dissimilar or similar metal layers, is explored. Preliminary results from welding experiments and tensile shear tests reveal that two bonding modes exist in the welding of PET and copper. Furthermore, analysis of power signals collected during welding shows that one can potentially monitor and optimize welding processes using monitoring signals. It is concluded from this study that ultrasonic welding has excellent potential in joining soft polymers and metals. Future work is also discussed on the process improvement and mechanism investigation.

Intrinsic thermal interfacial resistance measurement in bonded metal–polymer foils

“…A subtle issue in keeping the polymer intact arises from the lateral heat diffusion through the polymer that must be accounted for in the TIR measurements. We explain the experiment design process in this section for adhesively joined copper-Kapton junctions made from Dupont's double-side clad laminates [40] as a test case; however, it can also be extended to sputter-coated [45], electroplated [46], or welded [47], [48] metal-polymer junctions. The metal on either side of the laminate is patterned as four-point probes that act as heaters and temperature sensors.…”

“…Although we report measurements on adhesively-joined copper-Kapton junctions in this study, this TIR measurement technique is generally applicable to any metal-polymer junction and even certain metal-metal junctions. Such metal-polymer junctions made using sputtering [45], adhesives [40], mechanical fastening [61], or welding [47], [48], find applications in automotive sector [47], [62], flexible electronics [1], [40], and hybrid thermal management devices [6], [63]. Moreover, this TIR measurement technique can be used on metal-metal junctions that are adhesively bonded together, which are used in hybrid heat exchangers [6], [56], and in aircraft industries [64], where high strength-to-weight ratio joints are preferred.…”

“…The main modification is to employ an integrated heater and sensor. Here, we demonstrate the technique using proof-of-concept experiments to measure the intrinsic TIR of copper-Kapton junctions bonded using adhesives but the technique can be used on any metal-polymer junction ( ≫1 μm) made through techniques ranging from sputtering [45] to electroplating [46] to welding (laser [47], friction-stir [43], or ultrasonic [48]). Such metal-polymer junctions are used in emerging applications such as wearable electronics [1], [2], flexible solar cells [49], [50], Li-ion batteries [3], and hybrid heat exchangers [6].…”