Dynamic magnetic information storage or retrieval – Head mounting – For shifting head between tracks
Reexamination Certificate
1998-09-16
2001-04-03
Tupper, Robert S. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head mounting
For shifting head between tracks
Reexamination Certificate
active
06212046
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to an arm assembly for a disk drive device, in which a plurality of arms are stacked on each other, one end of each of the arms is fixed to each other, and the other end of the arms supports a read/write head, and relates to a method for fabricating the arm assembly.
A magneto resistive (MR) head has been used as a read/write head of a disk drive device. The MR head requires four connecting wires. As the number of data recording disks is increased, and a size of the disk drive device becomes small, a wiring process for connecting the four wires of each of the MR heads to pads on a flexible cable becomes time consuming work.
FIG. 1
shows a wiring process of a prior disk drive device. As an example, three rotating data recording disks
1
, and six arms
2
each of which supports a head/slider assembly
3
are shown. The four discrete connecting wires
4
of the MR head mounted in the head/slider assembly
3
are covered by a tube
5
, and the four wires are connected to pads
6
on a flexible cable
7
, respectively. Since a width W
F
of the flexible cable is very small in a recent disk drive device, the pads
6
are arranged in two columns, and the four wires
4
of the first arm
2
are connected to the four pads
6
in the first column, the four wires
4
of the second arm
2
are connected to the four pads
6
in the second column, and so on. The wires
4
are manually positioned to the pads
6
, and connected by solder.
The prior structure as shown in
FIG. 1
has caused the following problems. A first problem is that the manual wiring process is a time consuming job, and it increases the fabrication cost of the disk drive device, and the reliability of the entire electrical connection is lowered. A second problem is that since the MR head is easily damaged by electrostatic charges, the wiring should be made with great care. A third problem is that it is difficult to replace a bad MR head with a new MR head since the connections of the discrete wires
4
to the pads
6
are made in the small connecting space.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an arm assembly with an improved structure of the wiring system which solves the problems in the prior disk drive device, and an improved method for fabricating the arm assembly.
An arm assembly for a disk drive device in accordance with the present invention comprises:
a plurality of arms arranged in parallel to each other with a space, one end of each of the arms supporting a read/write head, and each of the arms having an extended plate which cantilevers from one of side edges of the arm, the extended plate being capable of deflecting in a direction which is vertical to a plane of the arm, and rotationally gimbal to a limited degree about two axes in the plane of the arm,
a plurality of first connecting pads provided on each of the extended plates, the first connecting pads being connected to the read/write head,
a circuit board which engages with the cantilevered extended plate and is provided with a plurality of second connecting pads characterized in that the plane of the circuit board is approximately orthogonal to the extended plate and is so located with respect to the extended plates of the plurality of arms to align the second connecting pads to the first connecting pads on each of the extended plates.
The configuration geometry of the circuit board deflects the extended plate in a direction which is generally normal to a plane of the arm to cause the extended plate to exert a self bias force which urges the first connecting pads into intimate contacts or near intimate contact with the respective second connecting pads.
The first connecting pads and the second connecting pads are connected by solder.
A solder volume is provided on each of the first connecting pads and the second connecting pads, and the extended plate which is deflected can move towards the solder volumes on the second connecting pads on the circuit board when the solder volumes become molten on both the extended plate and the circuit board, allowing two solder pair on the first connecting pad and the second connecting pad to coalesce as a single solder volume to form a single connecting solder fillet joint with high reliability and yield.
The solder volume on the first connecting pads of the extended plate is created in a fabrication of the extended plate by stenciling a solder paste on each of the first connecting pad, reflowing the solder paste, and flattening all the reflowed solders with a common anvil to form a plateau that is effectively coplanar for all reflowed solders for minimizing any contact gaps in a Z direction perpendicular to the plane of the arm.
An amount of motion and a compliance of the extended plate in the Z direction to allow the molten solder volume of the respective pad pairs to coalesce and form a single volume is equal to approximately 80% of a height of the flattened solder on the first connecting pads.
The circuit board is provided with a plurality of open ended slots to intersect and receive the cantilevered extended plate of each of the arms, a plurality of the second connecting pads are provided on a surface portion of each of edges of the open ended slots, and the edge of the open ended slot is not exactly parallel to a plane of the arm, but slopes at a low angle that conforms to the natural and deflected state of the extended plate.
A support plate is attached on a back surface of the circuit board, the support plate having side edges along the edges of the open ended slot, the side edge of the support plate being retreated from the edge of the open ended slot by a predetermined distance.
The support plate is made of an electrically nonconductive material, such as plastic.
The first connecting pads are provided on the extended plate along the X axis direction which is substantially parallel to a longitudinal direction of the arm, and a width of the first connecting pad along the X axis direction differs from a width of the second connecting pad along the X axis direction.
A width of the first connecting pad along the X axis direction is preferably wider than a width of the second connecting pad along the X axis direction.
The first connecting pad has a length along Y axis direction which is parallel to a direction along a width of the arm, the first connecting pad has a surface defined by the width and a length, a cross sectional portion of the second connecting pad is intimately adjacent and in close proximity to the surface of the first connecting pad.
The cross sectional portion of the second connecting pad is positioned at a position of about ⅓ of the length along the Y axis of the first connecting pad to accommodate a tolerance of misalignment of the cross sectional portion of the second connecting pad and the first connecting pad in the Y axis or a rotational tilt tolerance of the circuit board about X axis which is a longitudinal direction of the arm.
The first connecting pads are provided on an edge portion of the extended plate along the X axis direction which is substantially parallel to a longitudinal direction of the arm, and a slot is provided in the edge portion of the extended portion to separate the plurality of first connecting pads into two groups, and the first connecting pads and the second connecting pads are tinned with a solder, for providing the extended plate with an enhanced compliance in a direction perpendicular to a plane of the arm to create an intimate contact between orthogonal pad pairs in a pre-reflow state and in a solder reflow state.
An electrically conducive member for shorting the first connecting pads on the extended plate is provided to protect the read/write head from an electrostatic damage, and the electrically conductive member can remain in place until a completion of solder reflow process and can be detached from the extended plate.
Before the formation of the open ended slot is made in the circuit board, the second connecting pads on one edge of
Albrecht David William
Aoyagi Akihiko
Erpelding A. David
Katoh Masahiko
Kobayashi Masaki
International Business Machines - Corporation
Millett Douglas R.
Tupper Robert S.
LandOfFree
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