Effect of Interpass Annealing on the Microstructure, Nanoindentation Hardness, and Electrical Conductivity of ۲۰-μm Cold-Rolled Copper Foils

Copper foils play essential roles in electronic technologies, including lithium-ion batteries, printed circuit boards, and electrical interconnects, where microstructure, hardness, and electrical conductivity critically determine performance. Achieving the optimal combination of these properties is therefore central to producing high-quality foils. In this work, ۲۰-μm-thick copper foil was fabricated from tough pitch copper (TPC) through cold rolling, and interpass annealing was applied to tailor and improve these key characteristics.The material was first rolled from ۱۰۰ µm to ۳۰ µm, followed by interpass annealing for all samples except A۰. Rolling was continued to achieve a final thickness of ۲۰ µm. Annealing treatments were performed at ۱۵۰, ۲۰۰, ۲۵۰, and ۳۰۰ °C for ۱۰, ۱۵, ۲۰, and ۳۰ minutes. Microstructure, hardness, and electrical conductivity were characterized using optical microscopy, nanoindentation, and four-point probe measurements.The as-rolled sample (A۰) showed elongated, highly deformed grains (۱۷.۶۴ µm), elevated hardness (۱۲۴.۰۹ HV), and the lowest conductivity (۸۴.۳۹% IACS). Significant improvements were observed in samples B۴ and C۱, where recrystallization produced refined grains (۴.۰۱ µm in B۴ and ۳.۴۷ µm in C۱), reduced hardness (۶۴.۵۶ HV and ۵۵.۳۶ HV, respectively), and enhanced conductivity (۸۸.۹۹% and ۸۹.۷۶% IACS, respectively). Continued annealing led to grain growth, with D۴ exhibiting the highest conductivity (۹۶.۲۹% IACS).Overall, the influence of interpass annealing was evaluated across all processing conditions, and the results indicated that the routes used for samples B۴ and C۱ were optimal for producing ۲۰-µm copper foil suitable for electronic applications. Depending on available equipment, either route can be selected for industrial production.

کلیدواژه ها:

Tough pitch copper ، Printed Circuit Board ، recrystallization ، Grain size ، Foil Rolling