Disk device

A disk device according to one embodiment includes a magnetic disk, a magnetic head, and a flexible printed circuit board. The flexible printed circuit board is electrically connected to the magnetic head. The flexible printed circuit board includes a first layer, a second layer having conductive property, and a third layer having insulation property. The first layer includes a first surface having insulation property. The second layer overlays the first surface, and includes a first conductor and a second conductor spaced from the first conductor. The third layer covers at least a part of the first surface and at least a part of the second layer. The flexible printed circuit board is provided with a first hole that is located between the first conductor and the second conductor with spacing from the second layer and penetrates the third layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-137351, filed on Aug. 25, 2021; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a disk device.

BACKGROUND

In disk devices such as a hard disk drive, information is read and written from and to a magnetic disk with a magnetic head. Such a disk device includes, for example, a flexible printed circuit board that electrically connects a controller and the magnetic head. The flexible printed circuit board is provided with a plurality of conductors such as wiring and pads.

For example, along with improvement in the function of the disk device, the conductors may be mounted at a higher density on the flexible printed circuit board. In such a case, a shortened distance between two adjacent conductors may affect the performance of the flexible printed circuit board.

DETAILED DESCRIPTION

According to one embodiment, a disk device includes a magnetic disk, a magnetic head, and a flexible printed circuit board. The magnetic head is configured to read and write information from and to the magnetic disk. The flexible printed circuit board is electrically connected to the magnetic head. The flexible printed circuit board includes a first layer, a second layer having conductive property, and a third layer having insulation property. The first layer includes a first surface having insulation property. The second layer overlays the first surface and includes a first conductor and a second conductor spaced from the first conductor. The third layer covers at least a part of the first surface and at least a part of the second layer. The flexible printed circuit board is provided with a first hole that is located between the first conductor and the second conductor with spacing from the second layer and penetrates the third layer.

First Embodiment

Hereinafter, the first embodiment is described with reference toFIGS.1to6. Note that, in the present specification, constituent elements according to the embodiments and descriptions of the constituent elements may be described in a plurality of expressions. The constituent elements and description thereof are examples, and are not limited by the expressions of the present specification. The constituent elements may also be identified with names different from those in the present specification. In addition, the constituent elements may be described by using an expression different from the expression of the present specification.

FIG.1is an exemplary perspective view illustrating a hard disk drive (HDD)10according to the first embodiment. The HDD10is an example of the disk device, and may also be referred to as an electronic device, a storage device, an external storage device, or a magnetic disk device. The disk device is not limited to the HDD10.

The RDD10includes a casing11, a plurality of magnetic disks12, a spindle motor13, a plurality of magnetic heads14, an actuator assembly15, a voice coil motor (VCM)16, a ramp load mechanism17, a flexible printed circuit board (FPC)18, and a printed wiring board (PCB)19.

The casing11includes a base21, an inner cover22, and an outer cover23. The base21is a bottomed container made of a metal material such as an aluminum alloy, and has a bottom wall25and a side wall26. The bottom wall25is formed in a substantially rectangular (quadrangular) plate-like shape. The side wall26protrudes from an edge of the bottom wall25. The bottom wall25and the side wall26are integrally formed.

The inner cover22and the outer cover23are made of a metal material such as an aluminum alloy, for example. The inner cover22is attached to an end of the side wall26with, for example, a screw. The outer cover23covers the inner cover22and is airtightly fixed to the end of the side wall26by welding, for example.

The casing11is sealed inside. Inside the casing11, the magnetic disk12, the spindle motor13, the magnetic head14, the actuator assembly15, the VCM16, the ramp load mechanism17, and the FPC18are placed.

The inner cover22has a vent22a. Further, the outer cover23has a vent23a. After components are mounted inside the base21and the inner cover22and the outer cover23are attached to the base21, air inside the casing11is removed through the vents22aand23a. Further, the casing11is filled with a gas different, from air.

The gas filled inside the casing11is, for example, a low density gas having a density lower than that of air, an inert gas having low reactivity, or the like. For example, the casing11is filled with helium. The casing11may be filled with another fluid. The inside of the casing11may be maintained at vacuum, low pressure close to vacuum, or negative pressure lower than atmospheric pressure.

The vent23aof the outer cover23is closed by a seal28. The seal28hermetically seals the vent23ato prevent the leakage of the fluid filled in the casing11from the vent23a.

The magnetic disk12is, for example, a disk having magnetic recording layers provided on an upper surface and a lower surface thereof. The diameter of the magnetic disk12is, for example, 3.5 inches; however, the diameter is not limited to the example. The plurality of magnetic disks12is stacked at intervals.

The spindle motor13supports and rotates the magnetic disks12thus stacked. The magnetic disks12are held in a hub of the spindle motor13by, for example, a clamp spring.

The magnetic head14records and reproduces information on and from the recording layer of the magnetic disk12. Stated differently, the magnetic head14reads and writes information from and to the magnetic disk12. The magnetic head14is mounted on the actuator assembly15.

The actuator assembly15is rotatably supported by a support shaft31disposed at a position spaced from the magnetic disk12. The VCM16rotates the actuator assembly15to place the same at a desired position. When the magnetic, head14moves to the outermost periphery of the magnetic disk12, the ramp load mechanism17holds the magnetic head14at an unload position spaced from the magnetic disk12.

The actuator assembly15includes an actuator block35, a plurality of arms36, and a plurality of head suspension assemblies37. The head suspension assembly37is hereinafter referred to as a suspension37. The suspension37may also be referred to as a head gimbal assembly (HGA).

The actuator block35is rotatably supported by the support shaft31through a bearing, for example. The plurality of arms36protrudes from the actuator block35in a direction substantially orthogonal to the support shaft31. Another configuration is possible in which the actuator assembly15is divided and the arm36protrudes from each of the plurality of actuator blocks35.

The plurality of arms36is placed at intervals in a direction in which the support shaft31extends. Each of the arms36is formed in a plate-like shape which allows the arm to enter an interval between the adjacent magnetic disks12. The arms36extend substantially in parallel.

The actuator block35and the arms36are integrally made of, for example, aluminum. Note that the material of the actuator block35and the arms36is not limited to the example.

A voice coil of the VCM16is provided on a protrusion protruding from the actuator block35to the other side of the arm36. The VCM16includes a pair of yokes, the voice coil disposed between the yokes, and a magnet provided on the yoke.

The VCM16rotates the actuator assembly15as described above. In other words, the VCM16rotates (moves) the actuator block35, the arm36, and the suspension37together.

The suspension37is attached to an end of the corresponding arm36and protrudes from the arm36. Thereby, the plurality of suspensions37is placed at intervals in the direction in which the support shaft31extends.

Each of the suspensions37includes a base plate41, a load beam42, and a flexure43. Further, the magnetic head14is mounted on a tip of the suspension37.

The base plate41and the load beam42are made of, for example, stainless steel. Note that the materials of the base plate41and the load beam42are not limited to the example. The base plate41is formed in a plate-like shape and is attached to the end of the arm36. The load beam42is formed in a plate-like shape thinner than the base plate41. The load beam42is attached to an end of the base plate41and protrudes from the base plate41.

The flexure43is formed in an elongated belt shape. Note that the shape of the flexure43is not limited to the example. The flexure43is a stacked plate including a metal plate (backing layer) made of stainless steel or the like, an insulating layer formed on the metal plate, a conductive layer formed on the insulating layer and constituting a plurality of wirings (wiring patterns), and a protective layer (insulating layer) covering the conductive layer.

A gimbal part (elastic support part) that is positioned on the load beam42and is displaceable is provided in one end of the flexure43. The gimbal part is provided in the tip of the suspension37and the magnetic head14is mounted on the gimbal part. The other end of the flexure43is connected to the FPC18. This allows the FPC18to be electrically connected to the magnetic head14through the wiring of the flexure43.

The PCB19is, for example, a rigid board such as a glass epoxy board, and is a multilayer board, a build-up board, or the like. The PCB19is provided external to the casing11and is attached to the bottom wall25of the base21. The PCB19is attached to the bottom wall25with, for example, a plurality of screws.

For example, an interface (I/F) connector51, a controller52, and a relay connector53are mounted on the PCB19. Other components may be mounted on the PCB19.

The I/F connector51is a connector conforming to an interface standard such as serial ATA (SATA), and is connected to an I/F connector of a host computer. The HOD10receives power supply from the host computer through the I/F connector51, and sends and receives various pieces of data to and from the host computer.

The controller52is, for example, a system-on-chip (SoC), and includes a read/write channel (RWC), a hard disk controller (HDC), and a processor. Note that the RWC, the HDC, and the processor may be separate components.

The processor of the controller52is, for example, a central processing unit (CPU). The processor performs overall control of the HDD10according to firmware stored in advance in the ROM, for example. For example, the processor loads the firmware of the ROM into the RAM, and controls the magnetic head14, the RWC, the HDC, and other parts according to the firmware thus loaded.

The relay connector53is electrically connected to various components placed inside the casing11, for example, through a connector provided on the bottom wall25. This allows the PCB19to be electrically connected to the spindle motor13, the magnetic head14, the actuator assembly15, the VCM16, and the FPC18placed inside the casing11.

FIG.2is an exemplary plan view schematically illustrating the FPC18of the first embodiment. As illustrated inFIG.2, the FPC18is formed in a substantially L-shaped belt shape in a natural state where the FPC18is detached from the other components and no external force acts. Note that the shape of the FPC18is not limited to the example. The FPC18includes a first connection part61, a second connection part62, and an intermediate part63.

The first connection part61is provided, for example, in one end of the FPC18in a direction in which the FPC18extends. The first connection part61is attached to the actuator block35with, for example, a screw. The first connection part61is electrically connected to the VCM16and the flexure43.

The first connection part61has a plurality of insertion holes64. The insertion holes64penetrate the first connection part61. For example, the screw inserts through the insertion hole64to attach the first connection part61to the actuator block35. Note that the insertion hole64is not limited to the example. For example, a pin attached to the actuator block35through the insertion hole64may be fixed to the first connection part61by soldering.

The second connection part62is provided, for example, in the other end of the FPC18in the direction in which the FPC18extends. The second connection part62is attached to the bottom wall25with, for example, a screw. The second connection part62is electrically connected to the PCB19through, for example, a connector provided on the bottom wall25.

The intermediate part63is provided between the first connection part61and the second connection part62. The intermediate part63extends in a belt shape and bends between the first connection part61and the second connection part62in accordance with rotation of the actuator block35.

As illustrated in the drawings, in the present specification, an X-axis, a Y-axis, and a Z-axis are defined for convenience. The X-axis, the Y-axis, and the Z-axis are orthogonal to one another. The X-axis is along the width of the intermediate part63in the natural state. The Y-axis is along the length of the intermediate part63in the natural state. The Z-axis is along the thickness of the FPC18in the natural state.

Further, in the present specification, an X-direction, a Y-direction, and a Z-direction are defined. The X-direction is a direction along the X-axis and includes a +X-direction indicated by an arrow of the X-axis and a −X-direction which is an opposite direction of the arrow of the X-axis. The Y-direction is a direction along the Y-axis and includes a +Y-direction indicated by an arrow of the Y-axis and a −Y-direction which is an opposite direction of the arrow of the Y-axis. The Z-direction is a direction along the Z-axis and includes a +Z-direction indicated by an arrow of the Z-axis and a −Z-direction which is an opposite direction of the arrow of the Z-axis.

The first connection part61is connected to an end of the intermediate part63in the +Y-direction and extends in the +Y-direction from the end. The second connection part62is connected to an end of the intermediate part63in the −Y-direction and extends in the +X-direction from the end. Note that the first connection part61and the second connection part62are not limited to the example.

The HDD10further includes a plurality of preamplifiers65, a relay connector66, a sensor67, and a plurality of reinforcing plates68. The preamplifier65is an example of a component and may also be referred to as a head amplifier. The reinforcing plate68is an example of a wall.

The preamplifier65is mounted on the first connection part61. The preamplifier65is electrically connected to the flexure43, for example, through a wiring and pads of the FPC18. In addition, the preamplifier65is electrically connected to the magnetic head14through the flexure43. The preamplifier65amplifies a write signal to send the write signal to the magnetic head14, and amplifies a read signal sent from the magnetic head14.

The preamplifier65is fixed to the FPC18with an underfill69. The underfill69is provided and extends between the preamplifier65and the FPC18. A part of the underfill69is attached to an edge of the preamplifier65and is located outside the space between the preamplifier65and the FPC18.

The relay connector66and the sensor67are mounted on the second connection part62. The relay connector66is electrically connected to the relay connector53of the PCB19, for example, through a connector provided on the bottom wall25. The second connection part62is thereby connected to the PCB19. The relay connector66may be directly connected to the relay connector53of the PCB19. The sensor67detects, for example, temperature and humidity inside the casing11, and acceleration and angular acceleration of the HOD10.

The reinforcing plate68is made of, for example, a metal such as aluminum or a synthetic resin, and is formed in a plate-like shape. Note that the reinforcing plate68is not limited to the example. The reinforcing plates68are attached to the first connection part61and the second connection part62. The reinforcing plates68improve rigidity of the first connection part61and the second connection part62.

FIG.3is an exemplary plan view schematically illustrating a part of the first connection part61of the first embodiment.FIG.4is an exemplary cross-sectional view illustrating a part of the first connection part61of the first embodiment taken along the line F4-F4ofFIG.3.FIG.5is an exemplary cross-sectional view illustrating a part of the first connection part61of the first embodiment taken along the line F5-F5ofFIG.3.FIG.6is an exemplary cross-sectional view illustrating a part of the first connection part61of the first embodiment taken along the line F6-F6ofFIG.3.

As illustrated inFIG.4, the FPC18includes a base layer71, a conductive layer72, a cover layer73, ground layer74, and a cover layer75. The base layer71is an example of a first layer. The conductive layer72is an example of a second layer. The cover layer73is an example of a third layer.

The base layer71is made of, for example, an insulating material such as polyimide, and has insulation property. In a case where the FPC18is a multilayer FPC, the base layer71may have a plurality of insulating layers and a plurality of conductive layers.

The base layer71has an upper surface71aand a lower surface71b. Note that “upper” and “lower” in the present specification are convenient expressions on the basis of the vertical direction inFIG.4, and are not intended to limit the direction, Position, and other conditions. The upper surface71ais an example of a first surface.

The upper surface71ais a surface of the base layer71facing the Z-direction. The lower surface71bis located on the opposite side of the upper surface71aand is a surface of the base layer71facing the −Z-direction. Since the base layer71is made of an insulating material, the upper surface71ahas insulation property. For example, in a case where the FPC18is a multilayer FPC, a conductor may be exposed on the upper surface71a.

On the lower surface71b, the ground layer74made of a conductor such as copper is provided. The cover layer75is made of, for example, an insulating material such as polyimide to cover the ground layer74. In a case where the FPC18is a multilayer FPC, the ground layer74may be provided inside the base layer71.

The conductive layer72is made of, for example, a conductor such as copper and has conductive property. The conductive layer72overlays the upper surface71aof the base layer71. An adhesive layer may be provided between the conductive layer72and the upper surface71a.

The conductive layer72includes a plurality of pads81,82,83, and84, a signal wiring85, a power supply wiring86, two gimbal micro actuators (GMA) wirings87and88illustrated inFIG.3, and a conductor89illustrated inFIG.6. Further, the conductive layer72includes a plurality of ground wirings91,92, and93illustrated inFIG.3.

The pads81and82and the GMA wiring87are an example of a first conductor. The pads83and84, the power supply wiring86, and the GMA wiring88are an example of a second conductor. The GMA wiring87is an example of a first wiring. The GMA wiring88is an example of a second wiring. The pads81,82,83, and84may also be referred to as lands, terminals, or electrodes.

Each of the pads81and82is one of pads to which the preamplifier65is connected. As illustrated inFIG.4, a terminal65aof the preamplifier65is connected to the pad81. As illustrated inFIG.6, a terminal65bof the preamplifier65is connected to the pad82. The terminals65aand65bare, for example, solder balls. Note that the terminals65aand65bare not limited to the example.

The pad83illustrated inFIG.4is connected to a terminal of the voice coil of the VCM16. The pad83is connected to the VCM16through solder95. That is, the solder95is attached to the pad83. The pad83is spaced from the pads81and82.

As illustrated inFIG.3, the pad84is provided in a substantially annular shape along an edge of the insertion hole64. The pad84is covered with the solder96and protected by the solder96. Note that the pad84is not limited to the example. The pad84is spaced from the pads81and82.

The signal wiring85extends along the upper surface71abetween the relay connector66and the preamplifier65, for example. The signal wiring85is connected to the pad81or another pad to which the preamplifier65is connected, and sends a read signal and a write signal. Note that the signal wiring85is not limited to the example. The signal wiring85is spaced from the pads83and84.

The power supply wiring86extends along the upper surface71abetween the relay connector66and the pad83, for example. The power supply wiring86is connected to the pad83and supplies power to the VCM16. Note that the power supply wiring86is not limited to the example. The power supply wiring86is spaced from the pads81,82, and84and the signal wiring85.

The GMA wirings87and88extend along the upper surface71abetween the relay connector66and the flexure43, for example. The GMA wirings87and88extend substantially in parallel. The GMA wiring88thus extends along the GMA wiring87. Note that the distance between the two GMA wirings87and38may not be constant. The GMA wiring87is closer to the preamplifier65than the GMA wiring88.

The GMA wirings87and88are electrically connected to, for example, the magnetic head14of a microwave assisted magnetic recording (MAMR) system or a heat assisted magnetic recording (HANK) system, and the GMA wirings87and88send a control signal for a laser beam or microwave source. Note that the GMA wirings87and88are not limited to the example.

The conductor89illustrated inFIG.6is located between the pad82and the GMA wiring87. The conductor89is, for example, an inspection pattern used for inspection of the FPC18. Note that the conductor89is not limited to the example, and may be, for example, a wiring.

The ground wirings91,92, and93are electrically connected to the ground. For example, the ground wirings91,92, and93are electrically connected to the ground layer74through a via.

As illustrated inFIG.3, the ground wiring91extends through a region between the pad81and the pad33, a region between the pad81and the pad84, and a region between the pad81and the power supply wiring86. The ground wiring91is thus located between the pad81and the pad83and between the pad81and the pad84. The ground wiring91is also located between the underfill69and the pad83and between the underfill69and the pad84.

The ground wiring92is located between the GMA wiring87and the GMA wiring88. The ground wiring93is located between the pad82and the GMA wiring87. The ground wirings92and93extend substantially parallel to the GMA wirings87and88. Note that the ground wirings92and93may be shorter than the GMA wirings87and88.

As illustrated inFIG.4, the cover layer73covers at least a part of the upper surface71aof the base layer71and at least apart of the conductive layer72. For example, the cover layer73covers the signal wiring85, the power supply wiring86, the GMA wirings87and83, and the ground wirings91,92, and93. The cover layer73has a lower surface73aand an upper surface73b. The lower surface73ais an example of a second surface. The upper surface73bis an example of a third surface.

The lower surface73ais a surface of the cover layer73facing the −Z-direction. The lower surface73afaces the upper surface71aof the base layer71. The upper surface73bis located on the opposite side of the lower surface73aand is a surface of the cover layer73facing the Z-direction. The upper surface73bforms a surface of the FPC18.

The cover layer73includes a cover film101and an adhesive102. The cover film101is made of, for example, an insulating material such as polyimide. The adhesive102is made of, for example, an insulating adhesive. The cover layer73thus has insulation property. In other words, the electrical resistance of each of the base layer71and the cover layer73is higher than the electrical resistance of the conductive layer72.

The adhesive102is interposed between the cover film101and the upper surface71aof the base layer71and the conductive layer72. The adhesive102adheres the cover film101to the upper surface71aof the base layer71and the conductive layer72.

The cover layer73has a substantially constant thickness and covers the upper surface71aof the base layer71and the conductive layer72. Therefore, the cover layer73protrudes (rises) from the upper surface73bat a position where the conductive layer72is provided. As illustrated inFIG.3, the cover layer73has a plurality of protrusions111,112, and113.

As illustrated inFIG.4, the protrusion111is a part of the cover layer73that covers the ground wiring91. The protrusion111protrudes from the upper surface73balong the ground wiring91and extends along the ground wiring91. The protrusion111is thus located between the pad81and the pad83and between the pad81and the pad84in a direction along the upper surface71aof the base layer71. The protrusion111is located also between the underfill69and the pad83and between the underfill69and the pad84.

The protrusion111has two side surfaces111aand111b. The side surface111ais an example of a first protruding surface and a protruding surface. The side surfaces111aand111bprotrude (stick out, rise) from the upper surface73balong the ground wiring91, and face in a direction intersecting the direction in which the upper surface73bfaces.

The side surface ilia is closer to the pad83than the side surface111b, and is closer to the pad84than the side surface111b. The side surface111bis located on the opposite side of the side surface111a. The side surface111bis closer to the pad81than the side surface111a.

As illustrated inFIG.5, the protrusion112is a part of the cover layer73that covers the ground wiring92. The protrusion112protrudes from the upper surface73balong the ground wiring92and extends along the ground wiring92. The protrusion112is thus located between the GMA wiring87and the GMA wiring88in the direction along the upper surface71aof the base layer71.

The protrusion112has two side surfaces112aand112b. The side surfaces112aand112bprotrude from the upper surface73balong the ground wiring92, and face in the direction intersecting the direction in which the upper surface73bfaces. The side surface112ais closer to the GMA wiring88than the side surface112b. The side surface112bis located on the opposite side of the side surface112a. The side surface112bis closer to the GMA wiring87than the side surface112a.

As illustrated inFIG.6, the protrusion113is a part of the cover layer73that covers the ground wiring93. The protrusion113protrudes from the upper surface73balong the ground wiring93and extends along the ground wiring93. The protrusion113is thus located between the pad82and the GMA wiring87in the direction along the upper surface71aof the base layer71.

The protrusion113has two side surfaces113aand113b. The side surfaces113aand113bprotrude from the upper surface73balong the ground wiring93, and face in the direction intersecting the direction in which the upper surface73bfaces. The side surface113ais closer to the GMA wiring87than the side surface113b. The side surface113bis located on the opposite side of the side surface113a. The side surface113his closer to the pad82than the side surface113a.

As illustrated inFIG.3, the cover layer73has a plurality of exposure holes121,122,123, and124and a plurality of through holes125,126, and127. The exposure holes123and124are an example of a second hole. The through holes125,126, and127are an example of a first hole.

The exposure holes121,122,123, and124and the through holes125,126, and127penetrate the cover layer73in the Z-direction. The exposure holes121,122,123, and124and the through holes125,126, and127are thus open to the upper surface73band the lower surface73a.

As illustrated inFIG.4, the exposure hole121exposes the pad81. In other words, the cover layer73does not cover the pad81in a part where the exposure hole121is provided. As illustrated inFIG.6, the exposure hole122exposes the pad82. As illustrated inFIG.4, the exposure hole123exposes the pad83. The exposure hole124exposes the pad84.

The through holes125,126, and127are spaced from the conductive layer72in the direction along the upper surface71a. The through holes125,126, and127thus do not expose the conductive layer72. In other words, the through holes125,126, and127do not overlap the conductive layer72in the Z-direction.

As illustrated inFIG.3, the through hole125is located between the pad81and the pad83, between the pad81and the pad84, and between the pad81and the power supply wiring86. In addition, the through hole125is located between the underfill69and the solder95and between the underfill69and the solder96in the direction along the upper surface71aof the base layer71.

The through hole125is located between the ground wiring91and the pad83and between the ground wiring91and the power supply wiring86. Further, the through hole125is located between the side surface111aof the protrusion111and the exposure hole123in the direction along the upper surface71aof the base layer71. Further, the through hole125is located in the vicinity of an end111cof the side surface111ain a direction in which the side surface111aof the protrusion111extends.

The through hole126is located between the GMA wiring87and the GMA wiring88. The through hole126is located between the ground wiring92and the GMA wiring87. Further, the through hole126is located between the side surface112aof the protrusion112and the GMA wiring87in the direction along the upper surface71aof the base layer71.

The through hole127is located between the pad82and the GMA wiring87. The through hole127is located between the ground wiring93and the pad82. Further, the through hole127is also located between the side surface113aof the protrusion113and the pad82in the direction along the upper surface71aof the base layer71.

As illustrated inFIG.6, the through hole127exposes the upper surface71aof the base layer71and the conductor39. In other words, the cover layer73does not cover the conductor89in a part where the through hole127is provided. However, a part of the underfill69fills the through hole127and covers the conductor89. That is, a part of the underfill69is located in the through hole127.

As illustrated inFIGS.4and5, through holes131and132are provided in the base layer71. The through holes131and132are an example of a third hole. The through holes131and132penetrate the base layer71in the −direction. The through holes131and132are thus open to the upper surface71aand the lower surface71b.

The through hole131has substantially the same shape as the through hole125of the cover layer73. The through hole131overlaps the through hole125in the Z-direction and communicates with the through hole125. The shape of the through hole131may be different from the shape of the through hole125.

The through hole132has substantially the same shape as the through hole126of the cover layer73. The through hole132overlaps the through hole126in the Z-direction and communicates with the through hole126. The shape of the through hole132may be different from the shape of the through hole126.

Through holes135and136are provided in the ground layer74and the cover layer75. Each of the through holes135and136penetrates the ground layer74and the cover layer75in the Z-direction.

The through hole135has substantially the same shape as the through hole131of the base layer71. The through hole135overlaps the through hole131in the Z-direction and communicates with the through hole131. The shape of the through hole135may be different from the shape of the through hole131.

The through hole136has substantially the same shape as the through hole132of the base layer71. The through hole136overlaps the through hole132in the Z-direction and communicates with the through hole132. The shape of the through hole136may be different from the shape of the through hole132.

The reinforcing plate68is attached to the FTC18so as to cover the lower surface71bof the base layer71. Thus, the base layer71is located between the cover layer73and the reinforcing plate68. The rigidity of the reinforcing plate68is higher than the rigidity of the base layer71and higher than the rigidity of the cover layer73. The reinforcing plate68has through holes141and142. The through holes141and142are an example of a fourth hole. The through holes141and142penetrate the reinforcing plate68in the Z-direction.

The through hole141has substantially the same shape as the through hole131of the base layer71. The through hole141overlaps the through holes131and135in the Z-direction and communicates with the through hole131through the through hole135. The shape of the through hole141may be different from the shape of the through hole131.

The through hole142has substantially the same shape as the through hole132of the base layer71. The through hole142overlaps the through holes132and136in the Z-direction and communicates with the through hole132through the through hole136. The shape of the through hole142may be different from the shape of the through hole132.

The through holes125,126,131,132,135,136,141, and142are hollowed out and are not filled with a solid or a liquid. Therefore, the inside of the through holes125,126,131,132,135,136,141, and142is filled with gas in the casing11or is in a vacuum. Note that the through holes125,126,131,132,135,136,141, and142are not limited to the example. In addition, it is possible that the through holes131,132,135,136,141, and142are not provided. In such a case, the through holes125and126expose the upper surface71aof the base layer71.

Hereinafter, a method for mounting a component on the FPC18is partly exemplified. The method for mounting a component on the FPC18is not limited to the following method, and other methods may be used. First, solder paste (solder95and96) is supplied to the pads83and84by, for example, printing or coating. Further, the solder paste may be supplied to the pads81and82.

Next, the preamplifier65is mounted on the pads81and82. Further, a terminal of the VCM16is mounted on the pad83. Next, the FPC18is heated in a reflow furnace, so that the solder paste and the solder ball are melted. As a result, the terminals65aand65bof the preamplifier65are bonded to the pads81and82, the terminal of the VCM16is bonded to the Pad83, and the solder96covers the pad84. At this time, as illustrated inFIG.4, flux F mixed with or separately supplied to the solder95and96may flow out of the solder95and96.

Next, the underfill69is supplied between the preamplifier65and the FPC13. The underfill69is also supplied to the through hole127to cover the conductor89. At this time, in a case where the flux F is mixed with the underfill69, a substance that may contaminate the HDD10may be generated. For example, a crumbly sponge-like substance may be generated. However, the HDD10according to this embodiment can reduce the mixing of the flux F and the underfill69.

As illustrated inFIG.4, the flux F flows out of the solder95supplied to the pad83, for example, and wets and spreads along the upper surface73hof the cover layer73. The flux F also flows out of the solder96supplied to the pad84. When the flux F reaches the through hole125, which is open to the upper surface73b, the flux F stays at the edge of the through hole125due to surface tension. That is, the through hole125can block the flux F.

The flux F may flow into the through hole125. In such a case, the flux F accumulates in the through holes125,131,135, and141or is discharged through the through holes125,131,135, and141. Thus, the through hole125can block the flux F.

The flux F may go over the through hole125or bypass the through hole125to wet and spread toward the underfill69. However, the flux F is blocked by the side surface111aof the protrusion111.

The flux F that has bypassed the through hole125may flow along the side surface111aof the protrusion111. The flux F spreads from the end111cof the side surface111awhen reaching the end111c. However, since the through hole125is provided in the vicinity of the end111c, the flux F flows into the through hole125. As described above, the side surface111aof the protrusion111and the through hole125between the solder95and96and the underfill69block the flux F.

The through hole127illustrated inFIG.6is formed so as to block the flux F and allow the underfill69to flow in. For example, the angle of the edge of the through hole127is partially different. Thus, of the edge of the through hole127, a part thereof close to the underfill69allows the underfill69to pass therethrough. On the other hand, of the edge of the through hole127, a part thereof close to the solder blocks the flux F. Note that the through hole127is not limited to the example.

Next, the underfill69is cured by, for example, heat. This allows the underfill69to fix the preamplifier65to the FPC18. Next, the FPC18is cleaned by, for example, ultrasonic cleaning, and the flux F is removed. Thus, the mounting of the component on the FPC18is completed.

In the HDD10according to the first embodiment described above, the FPC18includes the base layer71, the conductive layer72, and the cover layer73having insulation property. The base layer71has the upper surface71ahaving insulation property. The conductive layer72overlays the upper surface71aand includes a first conductor (pads81and82, and GMA wiring87) and a second conductor (pads83and84, and GMA wiring88) spaced from the first conductor. The cover layer73covers at least a part of the upper surface71aand at least a part of the conductive layer72. The FPO18is provided with the through holes125,126, and127. The through holes125,126, and127are located between the first conductors81,82, and87and the second conductors83,84, and88with spacing from the conductive layer72and penetrate the cover layer73. For example, the preamplifier65attached to the pad31may be fixed to the FPC18with the underfill69while the pads83and84may be applied with the solder95and96. With the pad81and the pads83and84arranged at short intervals, the flux F may flow out of the solder95and96to the underfill69. In such a case the underfill69may mix with the flux F of the solder95and96, causing a substance that can contaminate the HDD10. However, in the HDD10of this embodiment, the through hole125extends between the pad81and the pads83and84. Thus, the through hole125can work to block the flux F, flowing out of the solder95and96attached to the pads83and84, before reaching the underfill69. As such, in spite of proximity between the pad81and the pads83and84, the HDD10according to this embodiment can prevent the flux F and the underfill69from being mixed, lowering the possibility to contaminate the HDD10. In other words, the HDD10can reduce the influence arising from the close arrangement of the pad81and the pads83and84. In addition, in the HDD10according to this embodiment, the hollow, through holes125,126, and127can insulate the first conductors81,82, and87from the second conductors83,84, and88. Thus, in spite of proximity between the first conductors81,82, and87and the second conductors83,34, and88, the HDD10according to this embodiment can prevent occurrence of short circuit or noise transmission between the first conductors81,82, and87and the second conductors83,84, and88. In other words, the HDD10can reduce the influence arising from the close arrangement of the first conductors81,82, and87and the second conductors83,84, and88.

For example, the potential difference between the two sets of GMA wiring87and88is larger than the potential difference between the signal wiring85and the power supply wiring86. In general, dielectric breakdown may occur in an insulator such as the cover layer73between two interconnections having a large potential difference. In this embodiment, however, the through hole126filled with gas or in a vacuum extends between the GMA wirings87and88. The electrical resistance of the gas or the vacuum space is higher than the electrical resistance of a solid such as polyimide. Because of this, the through hole126can prevent occurrence of dielectric breakdown between the two GMA wirings87and88having a large potential difference. In addition, the gas or the vacuum space has a lower thermal conductivity than a solid such as polyimide. Thus, the through hole126can work to prevent heat transfer between the two sets of GMA wiring87and88.

For example, while traveling across the signal wiring85for a higher-speed signal transmission, the signal is more susceptible to noise from the power supply wiring86caused by parasitic impedance, for example. However, in this embodiment, the through hole125filled with gas or in a vacuum extends between the signal wiring85and the power supply wiring86. Thus, the through hole125can work to prevent noise transmission between the signal wiring85and the power supply wiring86.

The preamplifier65is connected to the pad81. The underfill69extends between the preamplifier65and the FPC18. The solder95and96adhere to the pads83and84. The through hole125is located between the underfill69and the solder95and96. Thereby, the through hole125can block the flux F flowing out of the solder95and96before reaching the underfill69. Consequently, the HDD10according to this embodiment can prevent the flux F and the underfill69from being mixed.

The cover layer73has the lower surface73aand the upper surface73b. The lower surface73afaces the upper surface71a. The upper surface73bis opposite the lower surface73a. The cover layer73is provided with the exposure holes123and124. The exposure holes123and124are open to the upper surface73band expose the pads83and84. The FPC18has the side surface111abetween the pad81and the pads83and84in the direction along the upper surface71a. The side surface111aprotrudes from the upper surface73b. The flux F may flow out of the solder95and96attached to the pads83and34and spread over the upper surface73b. The flux F is, however, blocked by the protruding side surface111aon the upper surface73bbefore reaching the underfill69. Thus, the HDD10according to this embodiment can prevent the flux F and the underfill69from being mixed.

The through hole125is located between the side surface111aand the exposure holes123and124in the direction along the upper surface71a. Thereby, the through hole125can block the flux F out of the solder95and96attached to the pads83and84, before the side surface111ablocks. As a result, in the HDD10according to this embodiment, it is possible to prevent the flux F from flowing over the side surface111a, even if it has a relatively low height, to reach the underfill69.

The conductive layer72includes the sets of ground wiring91,92, and93. The ground wiring sets91,92, and93are located between the first conductors81,82, and87and the second conductors83,84, and88, and are electrically connected to the ground. The side surface111aprotrudes from the upper surface73balong the ground wiring91. The side surface111acan be formed on the cover layer73, for example, by stacking the cover layers73on the ground wiring91. This eliminates the necessity to add special steps for forming the side surface111a, which can prevent cost increase in the HDD10of this embodiment. Further, the ground wiring sets91,92, and93can serve to prevent occurrence of short circuit due to dielectric breakdown or noise transmission due to parasitic impedance between the first conductors81,82, and87and the second conductors83,84, and88.

The through hole125is located adjacent to the end111cof the side surface111ain the direction in which the side surface111aextends. Thereby, the through hole125can block the flux F, when blocked by the side surface111a, for example, from flowing further around the end111cof the side surface111a. Thereby, the HDD10according to this embodiment can prevent the flux F and the underfill69from being mixed.

The reinforcing plate68has rigidity higher than the base layer71and is attached to the FPC18. The base layer71is provided with the through hole131extending between the cover layer73and the reinforcing plate68and penetrating the base layer71to communicate with the through hole125. The reinforcing plate68is provided with the through hole141penetrating the reinforcing plate68to communicate with the through hole131. In other words, the through holes125,131, and141form a continuous hole penetrating the base layer71, the cover layer73, and the reinforcing plate68. Since the continuous hole has a volume larger than the through hole125, the continuous hole can store, i.e., block a larger amount of flux F than the through hole125. Thus, the HDD10according to this embodiment can prevent the flux F and the underfill69from being mixed. Further, for cleaning purpose, a cleaning liquid can flow through the continuous hole. As a result, the cleaning liquid can effectively remove the stored flux F from the continuous hole.

The conductive layer72includes the conductor89exposed from the through hole127. The underfill69is partly located in the through hole127to cover the conductor89. In general, supply and reflow of the solder are conducted before supply of the underfill69. Because of this, before supply of the underfill69, i.e., without inflow of the underfill69, the through hole127can block the flux F flowing out of the solder. Further, after the underfill69is supplied, the underfill69covers the conductor89. The underfill69thus can prevent the conductor89from being short-circuited or corroded.

The first conductors81,82, and87include the GMA wiring87extending along the upper surface71a. The second conductors83,84, and88include the GMA wiring88extending along the GMA wiring87. The cover layer73covers the GMA wirings87and88. The through hole126extends between the GMA wiring87and the GMA wiring88. In the HDD10according to this embodiment, the hollow, through hole126can insulate the GMA wiring87from, the GMA wiring88. Consequently, the HDD10according to this embodiment can prevent occurrence of short circuit or noise transmission between the GMA wiring87and the GMA wiring88.

Second Embodiment

Hereinafter, the second embodiment is described with reference toFIG.7. In the following description of the plurality of embodiments, constituent elements having functions similar to those of the constituent elements already described are denoted by the same reference numerals as those of the constituent elements already described, and the description thereof may be omitted. Further, the plurality of constituent elements denoted by the same reference numerals do not necessarily have all the functions and properties in common, and may have different functions and properties according to the embodiments.

FIG.7is an exemplary cross-sectional view illustrating a part of the first connection part61according to the second embodiment. As illustrated inFIG.7, the FPC18of the second embodiment includes a resist200instead of the ground wiring91and the protrusion111.

The resist200has a protrusion201. The protrusion201protrudes from the upper surface73bof the cover layer73. The resist200may be partially provided in the exposure hole121and partially provided on the upper surface73bas illustrated in the example ofFIG.7, or, alternatively, may be provided simply on the upper surface73b.

The protrusion201is located between the pad81and the pad83and between the pad81and the pad84in the direction along the upper surface71aof the base layer71. The protrusion111is located also between the underfill69and the pad83and between the underfill69and the pad84.

The protrusion201has two side surfaces201aand201b. The side surface201ais an example of the first, protruding surface and the protruding surface. The side surfaces201aand201bprotrude (stick out, rise) from the upper surface73b, and face in the direction intersecting the direction in which the upper surface73bfaces.

The side surface201ais closer to the pad83than the side surface201b, and is closer to the pad84than the side surface201b. The side surface201bis located on the opposite side of the side surface201a. The side surface201bis closer to the pad81than the side surface201a. In a case where the flux F flows out of the solder95, the flux F is blocked by the side surface201aof the protrusion201.

The through hole125is located between the side surface201aof the protrusion201and the exposure hole123in the direction along the upper surface71aof the base layer71. Further, the through hole125is located in the vicinity of an end of the side surface201ain a direction in which the side surface201aof the protrusion201extends.

As described above, the protrusions111and201can be provided in various modes. For example, as described in the first embodiment, the protrusion111and the side surfaces111aand111bmay be provided by raising a part of the cover layer73due to the presence of a part of the conductive layer72such as the ground wiring91. Alternatively, as described in the second embodiment, the protrusion201and the side surfaces201aand201bmay be provided by placing another member such as the resist200on the upper surface73bof the cover layer73.

Third Embodiment

Hereinafter, the third embodiment is described with reference toFIG.8.FIG.8is an exemplary cross-sectional view illustrating a part of the first connection part61according to the third embodiment. As illustrated inFIG.8, the FPC18of the third embodiment includes a bent part301instead of the ground wiring91and the protrusion111. The bent part301is a bent part of the FPC18.

In the third embodiment, the reinforcing plate68has a bent part302. The bent part302is a part of the reinforcing plate68bent by press working, for example. Further, the reinforcing plate68has a lower surface68a, an upper surface68b, a stepwise lower surface68c, a stepwise upper surface68d, and a slope68e. The upper surface68bis an example of a fifth surface. The slope68eis an example of a second protruding surface.

The lower surface68aand the stepwise lower surface68care surfaces of the reinforcing plate68facing the −Z-direction. The lower surface68aand the stepwise lower surface68care disposed substantially parallel to each other. The stepwise lower surface68cis spaced, by Z, from the lower surface68ain the Z-direction.

The upper surface68band the stepwise upper surface68dare surfaces of the reinforcing plate68facing the Z-direction. The upper surface68band the stepwise upper surface68dface the lower surface71bof the base layer71. The upper surface68bis located on the opposite side of the lower surface68a. The stepwise upper surface68dis located on the opposite side of the stepwise lower surface68c. The upper surface68band the stepwise upper surface68dare disposed substantially parallel to each other. The stepwise upper surface68dis spaced, by f Z, from the upper surface68bin the Z-direction.

The bent part302is provided between the lower surface68aand the stepwise lower surface68cand between the upper surface68band the stepwise upper surface68d. Stated differently, the bent part302bends the reinforcing plate68in a step shape such that the lower surface68aand the stepwise lower surface68care distinguished and the upper surface68band the stepwise upper surface68dare distinguished. Note that the reinforcing plate68is not limited to the example.

The slope68eis provided in the bent part302and is located between the upper surface68band the stepwise upper surface68d. The slope68eextends diagonally with respect to the upper surface68band the stepwise upper surface68dbetween the upper surface68band the stepwise upper surface68d. The slope68emay extend so as to be orthogonal to the upper surface68band the stepwise upper surface68d.

The slope68eprotrudes (sticks out, rises) from the upper surface68balong the bent part302, and faces in a direction intersecting the direction in which the upper surface68bfaces. The bent part302and the slope68eare located between the pad81and the pad83and between the pad81and the pad84in the direction along the upper surface71aof the base layer71.

The cover layer73further includes a stepwise upper surface73dand a slope73e. The slope73eis an example of the first protruding surface. The stepwise upper surface73dis disposed substantially parallel to the upper surface73b. The stepwise upper surface73dis spaced, by +Z direction, from the upper surface73bin the Z-direction. In the third embodiment, the exposure hole121is open to the stepwise upper surface73d. On the other hand, the exposure hole123is open to the upper surface73b.

The bent part301is provided between the upper surface73band the stepwise upper surface73d. Stated differently, the bent part301bends the FPC18in a step shape such that the upper surface73band the stepwise upper surface73dare distinguished. Note that the FPC18is not limited to the example.

The slope73eis provided in the bent part301and is located between the upper surface73band the stepwise upper surface73d. The slope73eextends diagonally with respect to the upper surface73band the stepwise upper surface73dbetween the upper surface73band the stepwise upper surface73d. The slope73emay extend so as to be orthogonal to the upper surface73band the stepwise upper surface73d.

The bent part301of the FPC18is formed by attaching the FPC18to the reinforcing plate68having the bent part302. The bent part301of the FPC18is thus provided along the bent part302of the reinforcing plate68.

The slope73eprotrudes (sticks out, rises) from the upper surface73balong the bent parts301and302, and faces in a direction intersecting the direction in which the upper surface73bfaces. In other words, the slope73eprotrudes from the upper surface73balong the slope68eof the reinforcing plate68.

The bent part301and the slope73eare located between the pad81and the pad83and between the pad81and the pad84in the direction along the upper surface71aof the base layer71. Further, the bent part301and the slope73eare located also between the underfill69and the pad83and between the underfill69and the pad84. In a case where the flux F flows out of the solder95, the flux F is blocked by the slope73e.

In the HDD10of the third embodiment described above, the reinforcing plate68has rigidity higher than the base layer71and is attached to the FPC18. The reinforcing plate68has the upper surface68bfacing the FPC18and the slope68eprotruding from the upper surface68b. The slope73eprotrudes from the upper surface73balong the slope68e. The slope73ecan be included in the cover layer73, for example, by attaching the FPC18to the upper surface68bhaving the slope68e. This eliminates the need to add special steps for forming the slope73e, leading to preventing cost increase in the HDD10of this embodiment.

In the embodiments described above, the preamplifier65is an example of the component; however, the relay connector66, the sensor67, or another component may be an example of the component. The protrusions111,112, and113and the through holes125,126, and127are provided in the first connection part61; however, they may be provided in another part such as the second connection part62.

In the above description, the prevention/reduction is defined as, for example, preventing the occurrence of an event, an action, or an influence, or reducing the degree of the event, the action, or the influence. Further, in the above description, the limit/restriction is defined as, for example, preventing movement or rotation, or allowing movement or rotation within a predetermined range and preventing movement or rotation beyond the predetermined range.