Molded ferrite sheet, sintered ferrite substrate and antenna module

A method of preparing molded ferrite sheet having opposing surfaces and a thickness in a range of 30 μm to 430 μm, comprising subjecting at least one surface to sandblasting with a polishing material thereby roughening said surface, wherein

• at least one surface of said opposing surfaces having the following surface roughness characteristics (a) to (c):
• (a) a center line average roughness is in the range of 170 nm to 800 nm,
• (b) a maximum height is in a range of 3 μm to 10 μm, and
• (c) an area occupancy rate of cross-sectional area taken along a horizontal plane at a depth of 50% of the maximum height in a square of said 100 μm is in a range of 10 to 80%.

A method of preparing molded ferrite sheet having opposing surfaces and a thickness in a range of 30 μm to 430 μm, comprising subjecting at least one surface to roughening said surface, wherein

• at least one surface of said opposing surfaces having the following surface roughness characteristics (a) to (c):
• (a) a center line average roughness is in the range of 170 nm to 800 nm,
• (b) a maximum height is in a range of 3 μm to 10 μm, and
• (c) an area occupancy rate of cross-sectional area taken along a horizontal plane at a depth of 50% of the maximum height in a square of said 100 μm is in a range of 10 to 80%,
• comprising preparing said molded ferrite sheet by molding under pressure using a mold or calender roll having a roughened surface so that the roughness of the roughened surface of said mold or calender roll is transferred to a surface of said molded ferrite sheet in contact with the roughened surface of said mold or calender roll.

A method of preparing molded ferrite sheet having opposing surfaces and a thickness in a range of 30 μm to 430 μm, comprising subjecting at least one surface to roughening said surface, wherein

• at least one surface of said opposing surfaces having the following surface roughness characteristics (a) to (c):
• (a) a center line average roughness is in the range of 170 nm to 800 nm,
• (b) a maximum height is in a range of 3 μm to 10 μm, and
• (c) an area occupancy rate of cross-sectional area taken along a horizontal plane at a depth of 50% of the maximum height in a square of said 100 μm is in a range of 10 to 80%,
• comprising preparing said molded ferrite sheet by applying a coating of a ferrite-dispersed coating liquid to a surface of a plastic film, and drying the applied coating, and wherein said surface of said plastic film has been roughened by sandblasting so that the roughness of said plastic film is transferred to a surface of the dried coating in contact with the roughened surface of said plastic film.

A method of preparing molded ferrite sheet having opposing surfaces and a thickness in a range of 30 μm to 430 μm, comprising subjecting at least one surface to roughening said surface, wherein

• at least one surface of said opposing surfaces having the following surface roughness characteristics (a) to (c):
• (a) a center line average roughness is in the range of 170 nm to 800 nm,
• (b) a maximum height is in a range of 3 μm to 10 μm, and
• (c) an area occupancy rate of cross-sectional area taken along a horizontal plane at a depth of 50% of the maximum height in a square of said 100 μm is in a range of 10 to 80%,
• comprising preparing said molded ferrite sheet by applying a coating of a ferrite-dispersed coating liquid to a support and drying the applied coating, wherein the ferrite has been obtained by adjusting a particle size of a ferrite powder having an average particle diameter of 0.1 to 10 μm so that the surface roughness characteristics are imparted to a surface of the dried coating in contact with said support.