Study on the mechanism of the influence of grain structure evolution on conductivity during copper electrode stamping
Publish Time: 2025-05-13
In the field of modern electronic device manufacturing, copper electrode has become a key functional material due to its excellent conductivity and machinability. As the main method for copper electrode forming, the evolution of metal grain structure during stamping directly affects the final conductivity of the electrode. Understanding the correlation mechanism between this microstructural change and macroscopic electrical properties is of great significance for optimizing stamping process parameters and improving electrode quality.As a face-centered cubic metal, copper undergoes complex plastic deformation in its grain structure during stamping. When copper foil is forcibly deformed under the action of the die, dislocation slip occurs first inside the grain. As the deformation increases, the dislocation density accumulates and forms an entangled structure. Although the proliferation of such microscopic defects enhances the mechanical strength of the material, it also constitutes an electron scattering center. Electrons collide with these lattice defects during directional migration, resulting in an increase in resistivity. It is particularly noteworthy that the relative relationship between the stamping direction and the copper foil rolling direction will induce obvious anisotropy. Grains with different orientations show differentiated responses during the deformation process, and finally form specific texture characteristics. This phenomenon of preferential orientation will further affect the spatial distribution of the electrode's conductive properties.The stamping process parameters have a decisive influence on the evolution of grain structure. Changes in stamping speed will change the thermal activation process of dislocation movement. Under low-speed conditions, dislocations have more time to rearrange and may form a more regular subgrain structure; while high-speed stamping tends to produce a higher density of randomly distributed dislocations. Equally important is the control of deformation. Moderate plastic deformation may promote grain refinement, but excessive deformation will cause grain breakage to form a nanocrystalline structure. Although this ultrafine grain structure has higher strength, the substantial increase in its grain boundary area will significantly enhance the electron scattering effect. In addition, the friction between the mold and the material will introduce an additional surface deformation layer. The degree of grain distortion in this area is often more severe than that of the matrix, becoming a bottleneck area for current transmission.The heat treatment process after stamping is an effective means to regulate the grain structure. During the annealing process, the deformation energy storage drives the recrystallization process, and new equiaxed grains nucleate and grow in the distorted matrix. This process can effectively eliminate the work hardening effect, reduce the dislocation density, and thus restore the electrical conductivity of copper. However, the selection of recrystallization temperature and time requires precise control. Too high a temperature or too long a holding time will cause abnormal grain growth. Although the conductivity is improved, the mechanical properties may not meet the use requirements. Especially for electrode products that require subsequent welding or assembly, the uniformity of grain size is equally important, and local coarse grains may become the origin of mechanical failure.From the application perspective, different electronic devices have different performance requirements for copper electrodes. High-frequency circuits require extremely low resistance loss, which requires maximizing the purity of copper and controlling the number of grain boundaries; while the electrodes in flexible electronic devices need to take into account both electrical conductivity and bending performance, and appropriate grain size distribution and texture orientation may be more favorable. In actual production, it is often necessary to find a balance between electrical conductivity and other performance indicators, and to achieve precise control of the material microstructure by optimizing the stamping-heat treatment process chain.Future research should pay more attention to the combination of multi-scale simulation and experimental verification. Molecular dynamics simulation can reveal the basic laws of dislocation movement, crystal plasticity finite element analysis can predict the texture evolution during macroscopic deformation, and in-situ electron backscatter diffraction technology can observe the dynamic changes of grain structure in real time. The comprehensive application of these methods will deepen the understanding of the "process-structure-performance" relationship and provide theoretical support for the development of a new generation of high-performance copper electrodes. At the same time, the application of artificial intelligence technology in process optimization is also worth looking forward to. By mining massive production data, a more accurate process window prediction model can be established to achieve intelligent control of the copper electrode manufacturing process.In summary, the evolution of grain structure during copper electrode stamping is a complex problem involving multi-physical field coupling. It is necessary to start from the basic theory of materials science, combine advanced characterization methods and numerical simulation methods, and systematically reveal the correlation mechanism between microstructure and conductive properties. The in-depth study will promote the copper electrode processing technology to develop in the direction of higher precision and better performance, and meet the increasing performance requirements of future electronic devices.
