The invention relates to a
copper foil and a preparation method and application thereof, the
copper foil comprises an electrolytic
copper foil layer and secondary long copper
layers located on the surfaces of the two sides of the electrolytic
copper foil layer, the maximum
Feret diameter average value of
crystal grains of the secondary long copper
layers is 2.5-3 microns, and the maximum
Feret diameter average value of
crystal grains of the electrolytic
copper foil layer is 1-2 microns. The maximum
Feret diameter average value of grains of the secondary growing copper layer on the surface of the
copper foil is 2.3-3 microns, the maximum Feret
diameter average value of grains of the internal electrolytic copper foil layer is 1-2 microns, a structure with the grain size of the
surface layer being large and the grain size of the inner layer being small is formed, and when the copper foil is used for transmitting a high-speed high-frequency
electric signal, due to the
skin effect of current, the high-speed high-frequency
electric signal can be transmitted. More electric signals are transmitted along the
surface layer of the copper foil, the grain size of the
surface layer is large, the
grain boundary is correspondingly reduced, and the obstruction to current is reduced, so that the loss of the electric signals is reduced, and the transmission integrity of the electric signals is improved.