Patent ID: 8505192

Claim:
A manufacturing method of common mode filters comprising the steps of: Step A: manufacturing a composite substrate that includes a base layer, an adhesive layer over the base layer, and a first magnetic material layer coated over the adhesive layer; the base layer and the first magnetic material layer sintered and connected by the adhesive layer so as to form the composite substrate; a particle size of magnetic material of the first magnetic material layer is smaller than 10 μm and a thickness of the first magnetic material layer ranges from 20 μm to 80 μm; Step B: forming a common mode choke layer over the composite substrate; the common mode choke layer having a plurality of inductive coils and a plurality of insulated layers while the inductive coil including at least a pair of leading-out terminals; a second magnetic material layer is coated over an upper surface of the common mode choke layer for forming a plurality of common mode filters on the same composite substrate; a particle size of magnetic material of the second magnetic material layer ranges from 34 μm to 80 μm and a thickness of the second magnetic material layer is about 50 μm to 150 μm; Step C: performing a first cutting by means of a cutting tool to form a groove between two common mode filters; the cutting tool cuts the second magnetic material layer and the common mode choke layer so that the leading-out terminals are located on sides of the common mode choke layer; Step D: forming external electrodes in the groove by sputtering, lithography and electroplating sequentially and allowing the external electrodes connected to the leading-out terminals of the inductive coils; the external electrode extending to an upper surface of the second magnetic material layer so as to form a conductive part; and Step E: cutting the composite substrate along the groove by a cutting tool to complete production of a plurality of single common mode filters.