Method of manufacturing coil unit in thin film type for compact actuator
Provided is a method of manufacturing a coil unit in a thin film type for a compact actuator, and more particularly, a method of manufacturing a coil unit in a thin film type for a compact actuator in which a buffer layer is formed on a coil layer to prevent cracks in the coil layer and a substrate. According to the method of manufacturing the coil unit in a thin film type for a compact actuator of the present invention, the buffer layer is formed on the coil layer so that an impact to the coil layer during a back-grinding process for thinning a substrate is absorbed, thereby preventing the substrate and the coil layer from breaking due to the back-grinding process and compensating for a difference of deformation between the coil unit and the substrate according to a difference of coefficients of thermal expansion. Further, according to the present invention, as the substrate is thinned by performing a back-grinding process, a gap which is a distance between a permanent magnet and the coil layer is reduced, and therefore sensitivity of the compact actuator can be improved.
1. A method of manufacturing a coil unit in a thin film type for a compact actuator, comprising:
a first step of laminating one or more coil layers on a substrate;
a second step of forming a buffer layer on the one or more coil layers;
a third step of forming an adhesive layer on the buffer layer to fix the coil unit on the adhesive layer and back-grinding a back surface of the substrate; and
a fourth step of removing the adhesive layer and mounting the coil unit manufactured by cutting a portion of a side of the substrate on a surface of a flexible printed circuit board (“FPCB”).
2. The method of claim 1 , wherein:
a material of the coil included in the coil layer in the first step includes a metal conductor formed of copper as a main component;
the metal conductor has a height in a range of 10 μm to 80 μm;
the metal conductor has a line width in a range of 5 μm to 50 μm;
the metal conductor is formed to be spaced apart by an insulating layer; and
the insulating layer has a thickness in a range of 1 μm to 10 μm.
3. The method of claim 1 , wherein, when a plurality of coil layers are laminated in the first step, an insulating layer is formed between a lower coil layer and an upper coil layer and the insulating layer has a thickness in a range of 1 μm to 30 μm.
4. The method of claim 1 , wherein:
one or more bump pads are formed on a portion of an upper part of the coil layer to cause the coil layer to conduct between the first step and the second step; and
the buffer layer is applied on the upper part of the coil layer except a space at which the bump pads are formed using a filler.
5. The method of claim 4 , wherein the coil layer is a patterned coil, and the filler is applied and cured in the same pattern as the coil.
6. The method of claim 4 , wherein a height of the filler is equal to or less than a height of the bump pads.
7. The method of claim 1 , wherein the substrate is back-ground to a thickness of 1 μm to 40 μm.