Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
1999-08-27
2001-05-15
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
Reexamination Certificate
active
06233122
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to disk drive suspensions, and more particularly to disk drive suspensions using flexible circuit trace conductors for electrical connection of the slider head to the device electronics without the presence of undue capacitive coupling between the load beam and the trace conductors. In a particular aspect, the invention relates to disk drive suspensions having a second dielectric film between the load beam and the trace conductors that serves to reduce or eliminate electrical interference from capacitive coupling, but which is not connected to the flexible circuit at the distal portion thereof. Thus where the flexible circuit defines a flexure there is no second dielectric layer attached to the flexible circuit so that desirable mechanical properties of the suspension are retained while the electrical properties improved.
2. Related Art
Flexible circuit comprising a dielectric layer and a plurality of trace conductors such as copper traces, with or without an added metal layer, are known to be used to provide the electrical connection in a suspension. Typically, the major part of the flexible circuit electrical connector lies juxtaposed with the load beam, the flexible circuit trace conductors being disposed upon the dielectric plastic film base layer and typically covered with dielectric plastic. The flexible circuit is fixed to the load beam at spaced locations along their mutual extents, with an air gap between the load beam and the flexible circuit between the points of attachment. With reference to
FIG. 3
, PRIOR ART, the suspension
8
is shown to include a load beam
9
, and a flexible circuit
11
spaced from the load beam across an air gap
4
. The flexible circuit
11
comprises trace conductors
5
that tend to capacitively couple with the load beam
9
, a dielectric layer
6
that is too thin to effectively block capacitive coupling, e.g. 0.001 inch thick, and a cover of insulating plastic
7
. Increasing the thickness of the dielectric layer
6
is potentially effective to block capacitive coupling but the mechanical properties of the resulting circuit are too compromised. For example, the flexibility of the flexible circuit
11
is decreased by having a thicker dielectric layer
6
to the point that the utility of the flexible circuit to define a flexure at the distal portion of the circuit, as is desirable, is negated.
SUMMARY OF THE INVENTION
The invention uses a second dielectric layer, not attached to the flexible circuit distal portion, but in place to block capacitive coupling between the load beam and the trace conductors.
It is an object, therefore, of the present invention to provide an improved disk drive suspension. It is another object to provide a disk drive suspension having excellent electrical high frequency response through the control and elimination of capacitive coupling between the trace conductors of the flexible circuit electrical connector and the steel load beam without adverse effect on the suspension mechanical properties. A further object is the provision of a disk drive suspension in which the tendency to capacitive coupling between the flexible circuit trace conductors and the load beam is limited or eliminated by the interposition of a capacitive coupling blocking-effective, substantial additional dielectric member between the load beam and the flexible circuit, the added member being attached to the load beam but free of attachment to the flexible circuit distal portion not opposite the load beam so as to affect the electrical but not the mechanical properties of the disk drive suspension assembly.
These and other objects of the invention to become apparent hereinafter are realized in a disk drive suspension comprising a steel load beam and an electrical connector comprising a flexible circuit comprising dielectric plastic film and trace conductors disposed thereon in capacitive coupling proximity across an air gap to the load beam, the dielectric film being a first dielectric film and having a thickness providing the electrical connector predetermined mechanical properties but inadequate to block capacitive coupling of the trace conductors with the steel load beam across the air gap, a second dielectric film interposed in the air gap between the load beam and the flexible circuit, the second dielectric film having a thickness adequate to block the capacitive coupling, the second dielectric film being sandwiched between the load beam and the electrical connector, whereby capacitive coupling between the load beam and the trace conductors is blocked without increasing the thickness of the first dielectric film or varying the predetermined mechanical properties.
In this and the following embodiment, typically, the electrical conductor flexible circuit has a distal portion shaped to define a slider- supporting flexure, the distal portion being free of the second dielectric, the load beam has left and right edge rails, the electrical connector being disposed between the edge rails, the first dielectric film is a polyimide plastic film, the polyimide plastic first dielectric film has thickness of less than about 0.001 inch. the second dielectric film is a polyimide plastic film, adhesively attached to the load beam, the second dielectric film has a thickness of greater than about 0.002 inch, or more particularly, the second dielectric film has a thickness between about 0.002 and 0.006 inch, and the second dielectric film is adhesively attached to the portion of the flexible circuit that is opposite the load beam.
In a preferred embodiment, the invention provides a disk drive suspension comprising a stainless steel load beam and a flexible circuit electrical connector comprising a laminate of dielectric plastic film and a plurality of trace conductor pairs disposed thereon in capacitive coupling proximity to the load beam in a capacitance zone defined by opposing portions of the load beam and the flexible circuit electrical connector, the flexible circuit connector having a distal portion beyond the capacitance zone, the dielectric film being a first dielectric film and having a thickness providing the flexible circuit electrical connector predetermined mechanical properties within and beyond the capacitance zone but inadequate to block capacitive coupling of the trace conductors with the opposing steel load beam in the capacitance zone, a second dielectric film bonded between the opposing load beam and flexible circuit electrical connector portions, the second dielectric film having a thickness adequate to block the capacitive coupling, whereby capacitive coupling between the load beam and the trace conductors is blocked without increasing the thickness of the first dielectric film or varying the predetermined mechanical properties in the flexible circuit electrical connector distal portion.
REFERENCES:
patent: 5995328 (1999-11-01), Balakrishnan
Bachand Louis J.
Magnecomp Corp.
Tupper Robert S.
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