Abstract:
A disk drive suspension comprising a flexible circuit electrical connector and a steel load beam has a second dielectric layer free of conductive traces and not part of the flexible circuit positioned and maintained between the flexible circuit and the load beam.

Description:
REFERENCE TO RELATED APPLICATION 
     This application is a continuation in part of my application Ser. No. 09/384,466, filed Aug. 27, 1999, now U.S. Pat. No. 6,233,122 issued May 15, 2001, which application claims the benefit of U.S. Provisional Application Serial No. 60/139,311 filed Jun. 15, 1999. 
    
    
     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 maintained 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 across an air gap to the load beam, the dielectric film being a first dielectric film, and a second dielectric film free of trace conductors and maintained between the load beam and the electrical connector. 
     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 film, 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, typically 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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be further described in conjunction with the attached drawings in which: 
     FIG. 1 is an oblique view of the invention suspension; 
     FIG. 2 is a view taken on line  2 — 2  in FIG. 1; and, 
     FIG. 3 is a view like FIG. 2 but of a PRIOR ART suspension. 
    
    
     DETAILED DESCRIPTION 
     With reference to FIGS.,  1  and  2 , the invention disk drive suspension is shown at  10  and comprises a stainless steel load beam  12  having a rigid portion  14  with left and right edge rails  16 ,  18 . The suspension  10  further includes an electrical connector  22  comprising a flexible circuit  24  of a dielectric plastic film layer  26  and trace conductors  28  disposed thereon in capacitive coupling proximity across an air gap  32  to the load beam  12 . Electrical connector  22  is electrically connected to slider  20 . The dielectric film layer  26  is a first dielectric film and has a thickness, typically, of about 0.001 inch, sufficient to provide the electrical connector  22  predetermined mechanical properties but inadequate to block capacitive coupling of the trace conductors  28  with the load beam  12  across the air gap  32 . Thus, the invention suspension  10  has a second dielectric film layer  34  interposed in the air gap  32  between the load beam  12  and the flexible circuit  24 . Second dielectric film layer  34  has a thickness, typically, in the range of 0.002 to 0.006 inch, and preferably about 0.002 inch, and adequate to block the capacitive coupling. The second dielectric film layer  34  is sandwiched between the load beam  12  and the electrical connector  22 , essentially filling the gap  32 . The increased dielectric barrier resulting from the presence of the second dielectric layer effectively blocks capacitive coupling between the load beam  12  and the trace conductors  28 ; achieving this result without increasing the thickness of the first dielectric film layer  26  or thereby varying the predetermined mechanical properties. 
     Preferably, the electrical connector flexible circuit  24  has its distal portion  36  shaped to define a slider-supporting flexure  38 . The flexible circuit distal portion  36  is free of the second dielectric layer  34  so as to have the predetermined mechanical properties essential to the flexure function, including the flexibility associated with only the thinner first dielectric layer  26 . Inward of the flexible circuit distal portion  36  the flexible circuit  24  is adhered to the second dielectric layer  34  with a suitable adhesive  42  such as Acrylic R/Flex 2000 ex Rogers Corp., Chandler, Ariz. The second dielectric layer  34  is further similarly adhered to the load beam with adhesive  44 . 
     As noted above, the first and second dielectric film layers typically comprise a polyimide plastic film. 
     The second dielectric layer  34  is used where there is a portion of load beam  12  opposite the trace conductors or trace conductors  28  and capacitive coupling takes place. Those areas are collectively termed herein a capacitance zone, that is a volume or zone  46  where capacitive coupling can take place. Zone  46  does not extend to the distal portion  36  of the flexible circuit  24 , and thus neither does the second dielectric layer  34 .