Abstract:
A method of manufacturing a motor including a rotating portion and a stationary portion including a stator, a base portion, and a circuit board preferably includes the steps of: a) arranging the stator at a predetermined position on the base portion, and arranging a lead wire of a coil of the stator at a position on a far side of an imaginary cylindrical surface centered on a central axis and which touches top surfaces of teeth of a stator core with respect to the top surfaces; b) arranging a shield between a land portion of the circuit board and the top surfaces; c) soldering the lead wire to the land portion, the lead wire extending along an upper surface of the circuit board through a gap between the shield and the circuit board; d) removing the shield; and e) attaching the rotating portion to the stationary portion.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electric motor and more specifically, to an electric motor for use in a hard disk drive. 
     2. Description of the Related Art 
     Disk drive apparatuses, such as hard disk drives, typically have spindle motors arranged to rotate disks installed therein. An example of a conventional spindle motor is disclosed in JP-A 11-218128 and includes a motor frame, a housing, a stator, and flexible printed wiring. The housing is cylindrical in shape and is defined integrally with the motor frame. The stator is press fitted and thereby fixed to an outer circumference of the housing. Terminals of coil wires of coils included in the stator are connected to the flexible printed wiring, which is arranged on an upper surface of the motor frame, through solder. 
     An interior space of a disk drive disclosed in JP-A 2006-40423 is filled with a low-density gas, such as helium, hydrogen, or the like. This contributes to preventing vibrations of a disk and a head, thereby enabling highly accurate data recording. 
     In the case where lead wires of coils are connected to a circuit board through a solder at positions radially outward of a stator, the solder may come into contact with a rotor magnet of a motor. In the case where the coil wires and the flexible printed wiring are connected to each other through the solder under an outer edge portion of a stator core as described in JP-A 11-218128, the operation of performing the soldering may be cumbersome. Moreover, it is very likely that fumes or flux will be adhered to the stator during the soldering operation. 
     SUMMARY OF THE INVENTION 
     According to a preferred embodiment of the present invention, a method of manufacturing a motor preferably including the following steps a), b), c), d), and e) is provided. The motor manufactured in accordance with the present preferred embodiment preferably includes a rotating portion and a stationary portion including a stator, a base portion, and a circuit board. In step a), the stator is arranged at a predetermined position on the base portion, and a lead wire of a coil of the stator is arranged at a position on a far side of an imaginary cylindrical surface centered on a central axis and which touches top surfaces of teeth of a stator core with respect to the top surfaces. In step b), a shield is arranged between a land portion of the circuit board and the top surfaces. In step c), the lead wire is soldered to the land portion, with the lead wire extending along an upper surface of the circuit board through a gap between the shield and the circuit board. In step d), the shield is removed. In step e), the rotating portion is attached to the stationary portion. 
     According to another preferred embodiment of the present invention, a motor that is preferably used in a disk drive apparatus is provided. The motor preferably includes a stationary portion, a rotating portion, and a bearing mechanism. The stationary portion includes a stator. The rotating portion includes a rotor magnet. The rotor magnet is arranged radially outward of the stator. The bearing mechanism is arranged to support the rotating portion such that the rotating portion is rotatable about a central axis with respect to the stationary portion. The stationary portion preferably includes a base portion and a circuit board. The base portion is arranged to define a portion of a housing of the disk drive apparatus. The circuit board is preferably arranged on an upper surface of the base portion. A lead wire of a coil of the stator preferably includes an inclined portion arranged to extend between the stator and the circuit board while being inclined radially outward with decreasing height; a tip portion arranged to extend radially outward along an upper surface of the circuit board, and to be soldered onto the circuit board outside of a stator core of the stator; and a bent or curved portion preferably defined between the inclined portion and the tip portion, and arranged below an outer circumferential surface of the stator core. At least a portion of a solder portion on the circuit board is preferably arranged to overlap with the rotor magnet in an axial direction. 
     The present invention makes it possible to prevent fumes and/or flux from being adhered to the stator, and also to prevent the lead wire of the coil and the rotor magnet from interfering with each other. 
     The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a disk drive apparatus according to a preferred embodiment of the present invention. 
         FIG. 2  is a plan view of a first housing member according to a preferred embodiment of the present invention. 
         FIG. 3  is a cross-sectional view of a motor according to a preferred embodiment of the present invention. 
         FIG. 4  is a plan view of a stator core according to a preferred embodiment of the present invention. 
         FIG. 5  is a cross-sectional view of the motor according to a preferred embodiment of the present invention. 
         FIG. 6  is a cross-sectional view of the motor according to a preferred embodiment of the present invention. 
         FIG. 7  is a flowchart illustrating a procedure of manufacturing the motor according to a preferred embodiment of the present invention. 
         FIG. 8  is a cross-sectional view of a stationary portion in a process of being assembled according to a preferred embodiment of the present invention. 
         FIG. 9  is a plan view of the stationary portion in the process of being assembled according to a preferred embodiment of the present invention. 
         FIG. 10  is a diagram illustrating a shield according to a preferred embodiment of the present invention. 
         FIG. 11  is a diagram illustrating a stationary portion of a motor according to a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     It is assumed herein that a vertical direction is defined as a direction in which a central axis of a motor extends, and that an upper side and a lower side along the central axis in  FIG. 1  are referred to simply as an upper side and a lower side, respectively. It should be noted, however, that the above definitions of the vertical direction and the upper and lower sides should not be construed to restrict relative positions or directions of different members or portions when the motor is actually installed in a device. Also note that a direction parallel or substantially parallel to the central axis is referred to by the term “axial direction”, “axial”, or “axially”, that radial directions centered on the central axis are simply referred to by the term “radial direction”, “radial”, or “radially”, and that a circumferential direction about the central axis is simply referred to by the term “circumferential direction”, “circumferential”, or “circumferentially”. 
       FIG. 1  is a cross-sectional view of a disk drive apparatus  1  including a spindle motor (hereinafter referred to simply as a “motor”)  12  according to a preferred embodiment of the present invention. The disk drive apparatus  1  is a so-called hard disk drive. The disk drive apparatus  1  preferably includes a plurality of disks  11 , the motor  12 , an access portion  13 , a connector  15 , and a housing  16 , for example. Each disk  11  is in the shape of a disc, and is arranged to store information therein. Each disk  11  is attached to the motor  12 . The access portion  13  is arranged to perform at least one of reading and writing of information from or to each disk  11 . The number of disks  11  is preferably three in the present preferred embodiment, for example. Note, however, that the number of disks  11  may be any desirable number other than three. 
     The housing  16  preferably includes a first housing member  161  and a second housing member  162 . The first housing member  161  preferably has a shape of a box without a lid. The second housing member  162  is preferably provided in the shape of a plate. The disks  11 , the motor  12 , and the access portion  13  are contained in the housing  16 . The second housing member  162  is joined to the first housing member  161  preferably through welding, for example, or by another joining method to define the housing  16  of the disk drive apparatus  1 . An interior space  163  of the housing  16  is preferably thereby hermetically enclosed. The interior space  163  is arranged to contain extremely little dirt or dust. In addition, an interior of the housing  16  is preferably filled with a low-density gas, such as, for example, helium, a mixture of helium and air, or the like. 
     The disks  11  are preferably arranged at regular intervals in an axial direction through spacers  172 . In addition, the disks  11  are preferably clamped to the motor  12  through a clamper  171 . The access portion  13  preferably includes a plurality of heads  131 , a plurality of arms  132 , and a head actuator mechanism  133 . Each arm  132  is arranged to support a separate one of the heads  131 . Here, the number of heads  131  is preferably six, however, any other desirable number could be used. The number of arms  132  is also preferably six, however, any other desirable number could be used. The head actuator mechanism  133  is arranged to actuate each arm  132  to move a corresponding one of the heads  131  relative to a corresponding one of the disks  11 . The above arrangement enables each head  131  to make access to a desired location on the corresponding disk  11  while being arranged in close proximity to the rotating disk  11 , to perform the reading and the writing of information. 
       FIG. 2  is a plan view of the first housing member  161 . In  FIG. 2 , a rotating portion  3  and a circuit board  14  of the motor  12 , the disks  11 , the access portion  13 , and the connector  15  are all represented by chain double-dashed lines. A bottom portion  61  of the first housing member  161  preferably includes a base portion  21 , a disk-accommodating recessed portion  62 , an access portion-accommodating recessed portion  63 , and a through hole  64 . The base portion  21  is arranged to define a portion of the motor  12 . The disk-accommodating recessed portion  62  preferably includes a portion which is arranged substantially in the shape of the letter “C” and centered on a central axis J 1 . The disk-accommodating recessed portion  62  is arranged to accommodate large portions of the disks  11 . 
     The access portion  13  is attached to the access portion-accommodating recessed portion  63 . The range of movement of each arm  132  of the access portion  13  overlaps with the access portion-accommodating recessed portion  63 . A bottom surface  631  of the access portion-accommodating recessed portion is arranged at a level axially lower than that of a bottom surface of the disk-accommodating recessed portion  62 . A portion of each disk  11  is arranged over the access portion-accommodating recessed portion  63 . The inclusion of the access portion-accommodating recessed portion  63  in the disk drive apparatus  1  contributes to preventing each head  131  from coming into contact with the bottom portion  61  of the first housing member  161  while the motor  12  is driven. 
     The access portion-accommodating recessed portion  63  preferably includes a portion which is slightly recessed relative to a surrounding area, and the through hole  64  is preferably defined in this portion. Referring to  FIGS. 1 and 2 , the connector  15  is fitted in the through hole  64  preferably through, for example, an adhesive or the like. The housing  16  of the disk drive apparatus  1  preferably includes only one through hole. The through hole  64  is preferably hermetically sealed with the connector  15 . Therefore, the gas, e.g., helium, with which the interior of the housing  16  is filled is prevented from leaking out through the through hole  64 . 
       FIG. 3  is a cross-sectional view of the motor  12 . The motor  12  is preferably an outer-rotor motor. In the present preferred embodiment, the motor  12  is preferably a three-phase motor, having U, V, and W phases. The motor  12  preferably includes a stationary portion  2 , which is a stationary assembly, the rotating portion  3 , which is a rotating assembly, and a fluid dynamic bearing mechanism  4  (hereinafter referred to as a “bearing mechanism  4 ”). The rotating portion  3  is supported through the bearing mechanism  4  such that the rotating portion  3  is rotatable about the central axis J 1  of the motor  12  with respect to the stationary portion  2 . 
     The stationary portion  2  includes the base portion  21 , an annular stator  22 , and the circuit board  14 . The base portion preferably includes a substantially cylindrical holder  211  arranged in a center of the base portion  21 . The stator  22  is preferably arranged around the holder  211 . The stator  22  preferably includes a stator core  221  and coils  222 . The coils  222  are arranged on the stator core  221 . Each of a common wire and a plurality of (preferably three in the present preferred embodiment) lead wires, which are drawn out from U-phase, V-phase, and W-phase coils, respectively, of the stator  22 , is soldered to the circuit board  14 . Hereinafter, the lead wires and the common wire will be referred to collectively as “lead wires  24 ”. 
     The circuit board  14  is preferably a flexible printed circuit board. Referring to  FIG. 2 , the circuit board  14  is arranged on an upper surface of the bottom portion  61  of the first housing member  161 , and arranged to extend from the rotating portion  3  toward the through hole  64 . 
     Referring to  FIG. 1 , the connector  15  preferably includes a plurality of pins  151 . One end portion of each pin  151  is arranged inside the housing  16 , and connected to the circuit board  14  therein. An opposite end portion of each pin  151  is arranged to project downward from the housing  16 , and is connected to an external power supply. Power is thereby supplied from the external power supply to the motor  12 . Note that supply of electricity to other members, such as the access portion  13 , and control of the other members, are also carried out through the connector  15 . 
       FIG. 4  is a plan view of the stator core  221 . The stator core  221  preferably includes a core back  231  and a plurality of teeth  232 . The core back  231  is preferably arranged in an annular shape and centered on the central axis J 1 . The teeth  232  are arranged to extend radially outward from an outer edge portion of the core back  231 . Each of the teeth  232  includes a winding portion  233  and a top portion  234 . A conducting wire is preferably wound around the winding portion  233  of each tooth  232  to define the coils  222  (see  FIG. 3 ). The top portion  234  of each tooth  232  is arranged to extend to both sides in a circumferential direction from an outer edge portion of the winding portion  233  of the tooth  232 . 
     Referring to  FIG. 3 , the rotating portion  3  preferably includes a rotor hub  31  and a magnetic member  32 . The rotor hub  31  preferably includes a hub body  311 , a cylindrical portion  312 , and an annular disk mount portion  313 . The cylindrical portion  312  is arranged to project downward from an outer edge portion of the hub body  311 . The disk mount portion  313  is arranged to extend radially outward from a bottom portion of the cylindrical portion  312 . A lowermost one of the disks  11  is mounted on the disk mount portion  313  as illustrated in  FIG. 1 . The magnetic member  32  preferably includes an annular rotor magnet  321 , which is centered on the central axis J 1 , and a back iron  322 . The rotor magnet  321  is preferably arranged inside the cylindrical portion  312  with the back iron  322  intervening therebetween. The disk mount portion  313  is arranged radially outside a lower portion of the rotor magnet  321 . The rotor magnet  321  is arranged radially outward of the stator  22 . In the motor  12 , a torque is generated between the rotor magnet  321  and the stator  22 . 
     The hub body  311  preferably includes a hole portion  311   a  arranged to extend in the axial direction. A portion  5  of the hub body  311  which is arranged in the vicinity of the central axis J 1  and which includes the hole portion  311   a  will be hereinafter referred to as a “sleeve portion  5 ”. The sleeve portion  5  preferably includes a communicating hole  51  arranged to extend in the vertical direction therethrough in the vicinity of the hole portion  311   a.    
     The bearing mechanism  4  preferably includes a shaft  41 , a first cone portion  421 , a second cone portion  422 , a first cover member  431 , a second cover member  432 , and a lubricating oil  44 . The shaft  41  is arranged in the hole portion  311   a  of the sleeve portion  5 . When the motor  12  is in an assembled state, a bottom portion of the shaft  41  is preferably arranged in a non-through hole (i.e., a blind hole) portion  212  defined inside of the holder  211 , so that the shaft  41  remains stationary while being oriented in the vertical direction along the central axis J 1 . 
     The first cone portion  421  is arranged on a lower side of the sleeve portion  5 . The second cone portion  422  is arranged on an upper side of the sleeve portion  5 . The first cover member  431  is arranged on a bottom portion of the sleeve portion  5  to cover a lower portion of an outside surface of the first cone portion  421 . The second cover member  432  is arranged on a top portion of the sleeve portion  5  to cover an upper end and an upper portion of an outside surface of the second cone portion  422 . 
       FIG. 5  is a diagram illustrating the bearing mechanism  4  in an enlarged form. A lower portion of an inside surface  52  of the hole portion  311   a  of the sleeve portion  5  is preferably arranged to be inclined radially outward with decreasing height, while an upper portion of the inside surface  52  is arranged to be inclined radially outward with increasing height. 
     A first inclined gap  45  is defined between the first cone portion  421  and the lower portion of the inside surface  52  of the sleeve portion  5 , and is arranged to be inclined radially outward with decreasing height. A second inclined gap  46  is defined between the second cone portion  422  and the upper portion of the inside surface  52  of the sleeve portion  5 , and is arranged to be inclined radially outward with increasing height. The lubricating oil  44  is arranged to fill a gap  47 , which is defined between the shaft  41  and a middle portion of the sleeve portion  5 , the first inclined gap  45 , the communicating hole  51 , and the second inclined gap  46 . In the bearing mechanism  4 , a surface of the lubricating oil  44  is arranged in a gap  48  defined between the first cover member  431  and the first cone portion  421 , and another surface of the lubricating oil  44  is arranged in a gap  49  defined between the second cover member  432  and the second cone portion  422 . 
     While the motor  12  is driven, a fluid dynamic pressure is generated through the lubricating oil  44  in each of the first and second inclined gaps  45  and  46 . The sleeve portion  5  is thereby supported to be rotatable with respect to the shaft  41 . In the motor  12 , the sleeve portion  5  is arranged to define a portion of the bearing mechanism  4  as a portion supported by the shaft  41 . 
       FIG. 6  is a diagram illustrating a lower portion of the stator  22  and its vicinity in an enlarged form. Each of the lead wires  24  of the coils  222  preferably includes an inclined portion  241  and a tip portion  242 . The inclined portion  241  is arranged to extend between the stator  22  and the circuit board  14  while being inclined radially outward with decreasing height. The tip portion  242  is arranged to extend radially outward along an upper surface of the circuit board  14 . The tip portion  242  is soldered onto the circuit board  14  outside of the stator core  221 . The top portion  234  of each tooth  232  defines a top surface of the tooth  232 . A bent portion  243  of the lead wire  24  which is defined between the inclined portion  241  and the tip portion  242  is preferably arranged below an outer circumferential surface  234   a  of the top portion  234 . 
     Solder portions  141  are preferably arranged on the circuit board  14  at a position radially outward of the stator core  221 , and arranged to overlap with the rotor magnet  321  and the back iron  322  in the axial direction. An upper end of each solder portion  141  is arranged at an axial level higher than that of a lower end  313   a  of the disk mount portion  313 . 
       FIG. 7  is a flowchart illustrating a procedure of manufacturing the motor  12 .  FIG. 8  is a diagram illustrating a portion of the stationary portion  2 , illustrating a situation in which each lead wire  24  has just been soldered to the circuit board  14 . When the motor  12  is manufactured, the circuit board  14  is preferably first attached to an upper surface of the base portion  21 . Next, the stator  22  is preferably arranged around the holder  211  of the base portion  21 . The lead wires  24  are preferably drawn from the coils  222  of the stator  22  to positions outside of the stator  22  (step S 11 ). To describe more precisely, each lead wire  24  is drawn to a position spaced away from and radially outward of an imaginary cylindrical surface  92  which is centered on the central axis J 1  and which touches the outer circumferential surface  234   a  of each top portion  234  of the stator core  221 . 
     A shield  91 , which is preferably cylindrical in shape and is centered on a central axis of the stator  22 , i.e., the central axis J 1 , is arranged between the stator  22  and land portions  14   a  of the circuit board  14  (step S 12 ). Referring to  FIG. 9 , an inner surface  91   a  of the shield  91  is preferably arranged to be in contact with a middle portion of each outer circumferential surface  234   a . In  FIG. 9 , passage lines of the stator  22  are not shown. Referring to  FIGS. 8 and 9 , the inner surface  91   a  of the shield  91  is arranged to be included in the imaginary cylindrical surface  92 . Note that the inner surface  91   a  of the shield  91  does not necessarily need to be arranged to be in contact with each outer circumferential surface  234   a  if so desired. The shield  91  is moved downward from above the stator core  221  along the central axis J 1  to be brought into contact with each lead wire  24 . Referring to  FIG. 8 , a lower end portion of the shield  91  is brought closer to the circuit board  14  while being in contact with the lead wire  24 , until the lower end portion of the shield  91  is brought into indirect contact with the upper surface of the circuit board  14  with the lead wire  24  intervening therebetween. The lead wire  24  is bent as a result. The tip portion  242  is arranged to extend radially outward through a gap between the shield  91  and the circuit board  14 . The inclined portion  241  is located inside of the shield  91 . The bent portion  243  is defined between the tip portion  242  and the inclined portion  241 . Hereinafter, the portion  243  will be referred to as a “bend portion  243 ”. Note, however, that the inclined portion  241  may alternatively be defined by a sagging portion in other preferred embodiments. In this case, the portion  243  defined between the tip portion  242  and the inclined portion  241  is preferably smoothly curved. The bend portion  243  is located below the outer circumferential surface  234   a  of the top portion  234 . Since the shield  91  is cylindrical, the bend portions  243  of the lead wires  24  are arranged on a circle centered on the central axis J 1 . 
     Next, referring to  FIGS. 8 and 9 , the tip portion  242  of each lead wire  24  is soldered to a corresponding one of the land portions  14   a  of the circuit board  14  (step S 13 ). Then, a portion of each lead wire  24  which extends beyond the solder portion  141  is cut off to complete a soldering operation for the lead wires  24 . Next, the shield  91  is removed from the stator  22  (step S 14 ). Then, the bearing mechanism  4  and the rotating portion  3  are attached to the stationary portion  2  as illustrated in  FIG. 3  (step S 15 ). 
     The structure of the disk drive apparatus  1  including the motor  12 , and the procedure of manufacturing the motor  12 , have been described above. When each lead wire  24  is soldered to the circuit board  14  during manufacture of the motor  12 , the shield  91  is arranged around the stator core  221  to prevent fumes and flux from being adhered to the stator  22 . Because the shield  91  is cylindrical in shape, it is easy to arrange the shield  91  around the stator  22 . The solder portions  141  are arranged radially outward of the top surfaces of the teeth  232 . Therefore, the soldering operation can be accomplished easily. 
     The tip portion  242  of each lead wire  24  is arranged to extend radially outward along the upper surface of the circuit board  14  below the outer circumferential surface  234   a  of the stator core  221 . This reduces the likelihood of interference between the lead wire  24  and the rotor magnet  321  as compared to the case where the lead wire  24  is arranged upward away from the circuit board  14  before being led to the land portion  14   a . Each solder portion  141  is arranged radially inward of the disk mount portion  313 . This makes it possible to arrange the lower end  313   a  of the disk mount portion  313  at a level lower than that of the upper end of the solder portion  141 . This makes it possible to ensure a sufficient thickness of the disk mount portion  313 . 
     The housing  16  preferably includes only one through hole, that is, the through hole  64  used for external connection. The housing  16  accordingly achieves a reduction in the probability that helium will leak out through a gap between the through hole and the part arranged in the through hole as compared to the case where the housing member includes a plurality of through holes. 
       FIG. 10  is a diagram illustrating a shield  91  according to another preferred embodiment of the present invention. A lower end portion of the shield  91  includes a plurality of recessed portions  911  which are recessed upward. Each recessed portion  911  is arranged to extend in the radial direction from an inner surface  91   a  to an outer surface of the shield  91 . When the shield  91  is arranged around the stator  22 , each of the lead wires  24  is passed through an inside of a separate one of the recessed portions  911  while the lower end portion of the shield  91  is arranged to be in direct contact with the upper surface of the circuit board  14 . The tip portion  242  of the lead wire  24  is passed through a gap between the recessed portion  911  and the circuit board  14  to reach a position away from and radially outward of the outer circumferential surface  234   a  of the top portion  234  of the stator core  221 . The tip portion  242  is soldered to the land portion  14   a . The recessed portions  911  defined in the shield  91  contribute to preventing any lead wire  24  from moving in the circumferential direction. 
       FIG. 11  is a diagram illustrating a portion of a motor  12  according to yet another preferred embodiment of the present invention. In this motor  12 , each solder portion  141  is covered with a resin material  142 . The resin material  142  is preferably, for example, an adhesive. When the stationary portion  2  is manufactured, each lead wire  24  is soldered onto the circuit board  14  as illustrated in  FIG. 8 . After the shield  91  is removed from the stator  22 , the resin material  142  is applied to each solder portion  141 . The resin material  142  contributes to preventing a gas from being generated from the solder portion  141 , and thereby preventing a gas from affecting any disk  11 . The structure of the motor  12  and a method of manufacturing the motor  12  according to the present preferred embodiment illustrated in  FIG. 11  are otherwise similar to those of the motor  12  illustrated in  FIG. 3 . 
     While preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described preferred embodiments, but a variety of modifications are possible. For example, in a modification of any of the above-described preferred embodiments, the shield  91  may not necessarily be cylindrical in shape, but may be shaped so as to include a portion in the shape of a circular or semi-circular arc and centered on the central axis J 1  in a plan view. In this case, the inner surface  91   a  of the shield  91  is preferably arranged to be included in the imaginary cylindrical surface which touches the outer circumferential surface  234   a  of each top portion  234  of the stator core  221 . This enables the shield  91  to be arranged properly along the outer circumferential surfaces  234   a . The inner surface  91   a  of the shield  91  is preferably arranged to extend over half or more than half a circumference of a circle centered on the central axis J 1 . This makes it easier to arrange the shield  91  around the stator core  221 . In the manufacture of the motor  12 , a shield in the shape of a plate may be used. Also, a shield in the shape of, for example, a polygon, an ellipse, or the like may be used. 
     The number of lead wires  24  may be three or any other number more than four. A portion of each solder portion  141  on the circuit board  14  may be arranged to overlap with a radially inner portion of the disk mount portion  313  in the axial direction as long as at least a portion of the solder portion  141  is arranged to overlap with the rotor magnet  321  in the axial direction. Also, each entire solder portion  141  may be arranged to overlap with the rotor magnet  321  in the axial direction. The first housing member  161  may be a member separate from the base portion  21 . A structure in which a shaft is arranged to rotate with respect to a sleeve portion fixed to a base portion may be adopted for the motor  12 . 
     Methods in accordance with preferred embodiments of the present invention of soldering the lead wires  24  are also applicable to being used in an inner-rotor motor, in which a rotor magnet is arranged radially inward of a stator. A stator core of the inner-rotor motor includes an annular core back and teeth arranged to extend radially inward from the core back. At the time of the soldering of the lead wires  24 , each lead wire  24  is drawn radially inward from the stator  22 . That is, each lead wire  24  is drawn to a position away from and radially inward of an imaginary cylindrical surface which touches top surfaces of the teeth. A cylindrical shield centered on the central axis J 1  is arranged on the top surfaces of the teeth. 
     Instead of helium, hydrogen may be used as the gas filled into the interior of the housing  16 . Also, a mixture of helium and hydrogen or a mixture of air and any one of helium, hydrogen, and the mixture of helium and hydrogen may be used as the gas filled into the interior of the housing  16 . 
     Preferred embodiments of the present invention are applicable to motors for use in disk drive apparatuses, and also to motors for use in other applications than the disk drive apparatuses. 
     Features of the above-described preferred embodiments and the modifications thereof may be combined appropriately as long as no conflict arises. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.