Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
2000-06-06
2003-07-01
Renner, Craig A. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
Reexamination Certificate
active
06587310
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improved electrical interconnect conductor and interconnect assembly for conducting electrical signals to and from a floating head assembly in a head suspension assembly in a dynamic storage device or rigid disk drive. The new interconnect uses traces—substrateless, flat electrical conductors. The present invention simplifies manufacturing of the head suspension assembly and allows flexibility of the head suspension's spring regions.
BACKGROUND OF THE INVENTION
Head suspension assemblies (HSAs) in rotatable data storage devices are spring structures that perform the difficult task of holding and positioning a head assembly nanometers away from the rapidly spinning irregular surface of a rotatable data storage device. The HSA can be part of a magnetic hard disk drive, the most common type of disk drive today, or of another type of drive such as an optical disk drive.
A HSA comprises different elements, the most common being a suspension assembly and a head assembly. A suspension assembly, the spring element, usually includes a load beam and a gimbal, each composed of a carefully balanced combination of rigid regions and flexible spring regions. A typical head assembly includes a “head”, comprising a highly sensitive read/write transducer, that is attached to an air bearing slider.
In a magnetic disk drive, a write transducer transforms electrical pulses to small magnetic fields which it then “writes” on a magnetic disk. A read transducer decodes these magnetic fields back into electrical pulses. The order of the magnetic fields and their subsequent orientation, aligned along the circumference of the disk in north-south configuration, defines a bit code that the transducer detects as the head floats on a cushion of air over the magnetic disk.
A head suspension assembly generally attaches at its proximal end to a rigid arm manipulated by a linear or rotary motion actuator designed to locate the head at any radial position above the disc. The spinning disk coupled with the actuator movement allows the head to gain access to multiple tracks across the disk surface, each track capable of containing large amounts of densely stored data. Positioned at the distal end of a suspension assembly, a gimbal holds the head assembly level and at a constant distance over the contours of the disk.
The closer the head assembly can fly to the surface of a magnetic disk, the more densely can information be stored (the strength of a magnetic field is inversely proportional to the square of the distance, thus the closer the head flies the smaller the magnetic “spot” of information). Today's disk drives strive to reach flying clearances close to 100 nanometers=0.1 micrometers (a human hair is about 100 micrometers thick). Greater data densities allow for greater storage and smaller size. But the head assembly must not touch the disk (“crash”), as the impact with the rapidly spinning disk (rotating at about 3600 rpm or faster) could destroy both the head and the surface of the disk, along with the data stored on it.
In order to achieve this delicate and precise positioning, a suspension assembly must carefully balance the load applied to the head assembly against the upward lift of the air stream on the slider. Since at this microscopic level the seemingly smooth surface of the disk is full of peaks and valleys, the HSA must be very responsive in order to maintain a level flying height. To avoid delays and errors, the HSA must be low in mass and both rigid to resist inertial movement and vibration and flexible to adapt to the undulations on the surface of the disk. Given the minute tolerances involved, even a small unexpected change in the loads or biases within the HSA, and specially in the flexibility of the spring regions, may cause a destructive crash.
As the head writes and reads to and from the disk, it receives and sends electrical pulses of encoded information. These electrical signals are amplified and processed by appropriate circuitry. Signal transmission requires conductors between the dynamic “flying” slider and the static circuitry of the data channels. However, while conductors can be routed fairly easily over the rigid actuator arm, providing the final interconnections through the suspension assembly and to the head is often extremely troublesome with current interconnect schemes.
Specially designed HSA interconnect assemblies are required in order to relay electrical signals accurately while not disturbing the precise balance of the HSA components. The term interconnect assembly refers to the entire interconnect system, including conductors, insulators, and other features. In order to assure data precision, interconnect assemblies must transmit the electrical signals free from interference or signal loss due to high inductance, high capacitance, and/or high resistance. Optimal interconnect conductors must be attached securely in order to reduce movement and vibration which cause varying electrical characteristics and affect mechanical performance. They must have low resistance and be well insulated from electrical ground.
Also, as technology advances, an interconnect system also must be capable of handling a plurality of signals. A basic interconnect assembly for a transducer having a single read/write inductive element calls for two conductors. More complex transducer designs may incorporate a separate magneto-resistive read element and an inductive write element, thus requiring a minimum of 3 conductors if the elements are tied together or a minimum of 4 conductors if the elements are completely separate. Other systems require even more conductors.
The problem is that in a HSA, interconnect assemblies must be planned around competing and limiting design considerations. The interaction of all the elements of an HSA forms a carefully balanced system. An ideal interconnect assembly must satisfy strict mechanical and manufacturing requirements.
First, an interconnect assembly must not impose unpredictable loads and biases which might alter the exact positioning of the head assembly, nor must it detract from the ability of the spring regions to adjust to variations in the surface of the disk, vibrations, and movement. Alterations to the flying height of the head can significantly affect data density and accuracy and even destroy the system in a crash. Neither of these two results would be well received by computer users.
Rigidity increases in relation to the third power of cross-sectional thickness. To respond to air stream changes and to hold a floating head, suspension assemblies are very thin and light, specially around the sensitive spring areas. A thick conductor placed atop of a thin suspension will dramatically increase a spring region's stiffness. Moreover, overshoot errors caused by inertial momentum are also affected by thick, high-in-mass conductors. Therefore, the ideal interconnect assembly must be low in mass and be very thin. As an additional requirement, interconnects placed over spring regions must not plastically deform when the region flexes, since that would hinder the return of the spring to its normal position and apply a load on the suspension assembly.
A second design consideration comes from manufacturing constraints. Like any commercial product, interconnect assemblies must be efficient to manufacture. Additionally, they must mate well and easily with the suspension assembly and the head assembly, be resistant to damage, and have precise manufacturing tolerances. Complex shaping and mounting processes are costly and decrease the reliability of the whole HSA manufacturing process. Fragile electrical conductors or interconnects that have to be added to the suspension assembly early in the manufacturing process are more susceptible to damage by subsequent production steps. They drastically diminish the manufacturing useful output yield.
Exacting tolerances are necessary to avoid defects and unpredictable loads and biases, specially when dealing with such minute measurements and clearan
Bennin Jeffry S.
Boucher Todd
Green Jeffrey W.
Gustafson Gary E.
Jurgenson Ryan
Faegre & Benson LLP
Hutchinson Technology Inc.
Renner Craig A.
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