Patent Publication Number: US-2011050011-A1

Title: Motor device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 10-2009-0081507 filed on Aug. 31, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a motor device, and more particularly, to a motor device in which a base plate is electrically connected with a ground pattern of a flexible printed circuit board on the base plate in a way that prevents damage to the flexible printed circuit board. 
     2. Description of the Related Art 
     In general, a spindle motor installed inside an optical disk drive serves to rotate a disk so that an optical pickup can read data stored in the disk. 
     Due to laptop computers or personal computers becoming slimmer and lighter, the optical disk drives used for such computers are also required to be slimmer and lighter. 
     Thus, market demands for slimmer spindle motors, main components of the optical disk drivers, are increasing. 
     In order to cope with such market demands, flexible printed circuit boards (FPCB) with a thickness ranging from 0.08 mm to 0.1 mm are increasingly being used instead of printed circuit boards (PCB) with a thickness ranging from 0.6 mm to 0.8 mm, which are typically used for the spindle motors. 
     A spindle motor is provided with a base plate to support a PCB or an FPCB. In general, a ground pattern of the PCB or the FPCB is electrically connected to the base plate through a screw in order to increase resistance to noise in the optical disk drive. 
     The FPCB, when grounded to the base plate using a screw, easily tears due to its low strength. 
     According to the related art, in order to prevent the FPCB from being torn, the screw coupling between the base plate and the FPCB is performed after providing solders to the entirety of a screw mounting portion of the ground pattern of the FPCB or inserting a washer into the screw mounting portion. 
     When the screw-coupling is performed after providing solders to the entirety of the screw mounting portion, the soldered solders are pushed out by the rotary force of a screw, tearing the FPCB. 
     The process of inserting the washer requires an additional material to be used, thereby increasing motor-material costs and increasing product manufacturing processes. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides a motor device in which a base plate is electrically connected to a ground pattern of a flexible printed circuit board on the base plate in a way that prevents damage to the flexible printed circuit board. 
     According to an aspect of the present invention, there is provided a motor device including: a base plate on which a motor for rotating a disk is disposed; a flexible printed circuit board disposed on the base plate and having a circuit pattern applying power to the motor; and a screw mounting portion provided with a ground pattern of the FPCB, mounted with a screw engaged to electrically connect the ground pattern to the base plate, and having apart on which solders are provided. 
     The solders on the screw mounting portion may be provided in the form of a plurality of dots. 
     The solders on the screw mounting portion may be distributed in any half of the screw mounting portion. 
     The flexible printed circuit board may have a through hole through which the screw is passed, and the screw mounting portion may be provided around the through hole in a ring shape. 
     The screw mounting portion may have an outer circumference greater than that of a head of the screw. 
     According to another aspect of the present invention, there is provided a motor device including: a base plate on which a motor for rotating a disk is disposed; a flexible printed circuit board disposed on the base plate and having a circuit pattern applying power to the motor; a screw mounting portion provided with a ground pattern of the flexible printed circuit board; and a screw engaging the ground pattern of the flexible printed circuit with the base plate through the screw mounting portion, and including a screw head having a bottom surface contacting the screw mounting portion, the bottom surface partially provided with solders. 
     The solders on the screw may be provided in the form of a plurality of dots. 
     The solders on the screw may be distributed in any half of the bottom surface of the screw head. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a plan view illustrating a motor device according to an exemplary embodiment of the present invention; 
         FIG. 2  is a cross-sectional view illustrating the motor device of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view illustrating a first exemplary embodiment of grounding an FPCB to a base plate of the motor device of  FIG. 1 ; 
         FIG. 4  is a plan view illustrating the FPCB of  FIG. 3  partially provided with solders; 
         FIG. 5  is a cross-sectional view illustrating a second exemplary embodiment of grounding an FPCB to a base plate of the motor device of  FIG. 1 ; and 
         FIG. 6  is a partially enlarged perspective view of a screw of  FIG. 5  partially provided with solders. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
     In the drawings, like reference numerals in the drawings denote like elements. 
       FIG. 1  is a plan view illustrating a motor device according to an exemplary embodiment of the present invention, and  FIG. 2  is a cross-sectional view illustrating the motor device of  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , a motor device, according to an exemplary embodiment of the present invention, may include a base plate  50 , a flexible printed circuit board (hereinafter, ‘FPCB’)  70 , and a screw mounting portion (see reference number  72   FIG. 3 ). 
     A motor, according to this embodiment, may include a rotor  20 , a stator  40  and a bearing assembly  60 . 
     The rotor  20  includes a cup-shaped rotor case  22  provided with a magnet  25  having a ring shape and disposed on its inner circumferential portion corresponding to a coil  46  of the stator  40 . The magnet  25  is a permanent magnet having N and S poles alternated in a circumferential direction to generate a magnetic force having a predetermined intensity. 
     The rotor case  22  includes a rotor hub  24  pressingly fitted on a shaft  62 , and a magnet coupling portion  26  having an inner surface on which the annular magnet  25  is disposed. The rotor hub  24  is disposed around the upper portion of the shaft  62  in an axial direction in order to maintain an un-mating force with respect to the shaft  62 . A chucking mechanism  40  for mounting a disk D is coupled to the outer circumferential surface of the rotor hub  24 . 
     The stator  40  includes a support  42  supported outside a sleeve  66 , a plurality of cores  44  fixed to the support  42 , and a winding coil  46  surrounding the core  44 . 
     The magnet  25  provided on the inner surface of the magnet coupling portion  26  faces the winding coil  46 . The rotor  20  is rotated by electromagnetic interaction between the magnet  25  and the winding coil  46 . 
     In addition, the bearing assembly  60  disposed inside the support  42  of the stator  40  includes the shaft  62  supporting the rotation of the rotor  20  and the sleeve  66  installed to render the shaft  62  rotatable. 
     As for terms regarding directions in the description, the axial direction refers to a vertical direction with respect to the shaft  62  in  FIG. 1 , and an outer diameter direction and an inner diameter direction refer to a direction toward the outer edge of the rotor from the shaft  62 , and a direction toward the shaft  62  from the outer edge of the rotor  20 , respectively. 
     The base plate  50  serves as a support on which the motor  10  is disposed. The FPCB  70  is provided on the base plate  50 . The use of the FPCB  70  may achieve a reduction in the thickness of the motor device  10  as compared to the case of using a printed circuit board. 
     The FCPB may have a circuit pattern that supplies power to the motor. 
     A ground pattern (see reference number  74  in  FIG. 3 ) of the FPCB  70  is electrically connected to the base plate  50 . 
     Here, a screw  80  is used to couple and electrically connect the ground pattern of the FCPB  70  to the base plate  50 . 
     Hereinafter, the construction for grounding the ground pattern of the FPCB  70  to the base plate  50  will now be described in more detail. 
       FIG. 3  is a cross-sectional view of a first exemplary embodiment of grounding the FPCB to the base plate of the motor device of  FIG. 1 .  FIG. 4  is a plan view of the FPCB of  FIG. 3  partially provided with solders. 
     Referring to  FIGS. 3 and 4 , solders  30  are provided on the screw mounting portion  72  in the form of a plurality of dots. The solders  30 , provided in the form of dots, are spread to the entirety of the screw mounting portion  72  by the rotary force of the screw  80  rotated and engaged while passing through a through hole  55  of the base plate  50  and a through hole  75  of the FPCB  70  at a time. 
     The screw mounting portion  72  has a ring shape around the through hole  75  of the FPCB  70 . The solders  30  having dot shapes may be distributed in any half of the screw mounting portion  72 . 
     The outer circumference of the screw mounting portion  72  may be greater than that of a head  82  of the screw  80 . This may prevent the solders  30  from flowing from the head  82  into a circuit pattern in the FPCB  70 . 
       FIG. 5  is a cross-sectional view of a second exemplary embodiment of grounding the FPCB to the base plate of the motor device of  FIG. 1 , and  FIG. 6  is a partially enlarged view of a screw of  FIG. 5  partially provided with solders 
     Unlike the embodiment of  FIGS. 3 and 4 , the embodiment of  FIGS. 5 and 6  forms solders  30  on a bottom surface  84  of the head  82  of the screw, rather than on the screw mounting portion  72  of the FPCB  70 . 
     The solders  30  are provided in the form of dots on the bottom surface  84  of the head  82  of the screw  80 , and may be distributed in any half of the bottom surface  84  of the head  82 . 
     Other than the above construction, the embodiment of  FIGS. 5 and 6  is identical to that of  FIGS. 3 and 4 . 
     As set forth above, according to exemplary embodiments of the invention, in the motor device, solders are provided in a part of the screw mounting portion of the FPCB or the bottom surface of the screw, rather than in the entirety of the screw mounting portion of the FPCB. Then, the rotary force of the screw causes the solders to be spread from the part of the screw mounting portion to the entirety of the screw mounting portion, without pushing out the solders outside the screw mounting portion, thereby preventing the FPCB from being damaged. 
     Also, since a washer, which is a separate member, is not used, the material costs can be reduced and the production process can be simplified. 
     While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.