Abstract:
A switchable shunt has an insulating layer separating conductive lead and spring metal layers. The shunt includes a base region formed on the spring metal layer, one or more arms formed in the conductive lead layer and at least one of the insulating and spring metal layers, one or more pad regions electrically coupled to an arm and formed in at least the conductive lead layer, and one or more gaps. Each arm extends through a gap and is resiliently biased toward a shunted state with the pad region in electrical contact with the base region. The shunt is movable to an electrically open state where the pad and base regions are electrically isolated. A method of making the shunt includes etching the shunt from laminated material and pushing the arm and pad through the gap. The shunt may be operated by applying a force to the arm.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims the benefit of U.S. Provisional Application Serial No. 60/152,175, filed on Sep. 2, 1999 and entitled “Switchable Shunts For Integrated Lead Suspensions.” This application also claims the benefit of U.S. Utility application Ser. No. 09/652,958, filed Aug. 31, 2000 and entitled “Switchable Shunts For Integrated Lead Suspensions.” 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to electrical shunts in integrated lead suspensions.  
         BACKGROUND OF THE INVENTION  
         [0003]    Integrated lead suspensions and components (such as flexures) for supporting read and/or write heads in disk drives are well known and in widespread use. So-called “subtractive” type integrated lead suspensions and associated methods for manufacturing the suspensions from laminated sheets of material are disclosed, for example, in the Bennin et al. U.S. Pat. Nos. 5,598,307 and 5,844,751.  
           [0004]    Magneto restrictive (MR) and giant magneto restrictive (GMR) heads are commonly mounted to the suspensions. Heads of these types are very sensitive to damage due to “blown fuse” syndrome and electrostatic discharges (ESD). To minimize this damage, the leads of the heads themselves and/or the integrated leads on the suspensions can be electrically shunted (i.e., interconnected or shorted) during manufacturing operations. The stainless steel (i.e., spring metal) layer of the suspension or flexure also is sometimes electrically interconnected to one of the integrated leads to couple the stainless steel layer to ground potential.  
           [0005]    It is sometimes necessary to conduct tests of the integrated leads and/or the heads. Any shunts on the leads must typically be removed before the tests can be performed. The leads and heads must be reshunted following the tests if it is again desired to protect the heads from damage. A number of approaches for shunting and reshunting MR and GMR heads, or otherwise electrically coupling the leads to the stainless steel layer during the various stages of the head suspension assembly manufacturing operations are known and disclosed, for example, in the following references.  
                                                   Inventor   Document No.                           Bajorek et at.   U.S. Pat. No. 5,465,186           Arya et al.   U.S. Pat. No. 5,710,682           Johansen et al.   U.S. Pat. No. 5,877,933           Kanda   U.S. Pat. No. 5,991,121           Zarouri et al.   U.S. Pat. No. 6,034,851           Albrecht et al.   U.S. Pat. No. 6,052,258           Hiraoka et al.   U.S. Pat. No. 6,075,676           Yim et at.   U.K. 2,343,304                      
 
           [0006]    There remains a continuing need for improved shunts. To be commercially viable, the shunts should be efficient to manufacture and use. Shunts which can be conveniently reused would be especially desirable. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a top view of a disk drive head suspension with an integrated lead flexure having a switchable shunt in accordance with a first embodiment of the present invention.  
         [0008]    [0008]FIG. 2 is a side view of a portion of a laminated sheet of material from which the shunt shown in FIG. 1 can be manufactured.  
         [0009]    [0009]FIG. 3 is a detailed view of the proximal section of the flexure tail shown in FIG. 1, illustrating the terminal pads and shunts.  
         [0010]    [0010]FIG. 4 is a sectional side view of a shunt in its pre-activated state, taken along lines  4 - 4  in FIG. 3.  
         [0011]    FIGS.  5 A- 5 C are sectional side views of the shunt shown in FIG. 4 as it is driven from its pre-activated to its activated state.  
         [0012]    [0012]FIG. 6A is an isometric view of a shunt in accordance with a second embodiment of the present invention in its electrically open state.  
         [0013]    [0013]FIG. 6B is an isometric view of the shunt shown in FIG. 6A in its shunted state.  
         [0014]    [0014]FIGS. 7A and 7B illustrate a method by which the shunt shown in FIGS. 6A and 6B can be fabricated.  
         [0015]    [0015]FIG. 8 is an isometric view of a shunt in accordance with a third embodiment of the present invention.  
         [0016]    [0016]FIG. 9A is an isometric view of a shunt in accordance with a fourth embodiment of the present invention in its electrically open state.  
         [0017]    [0017]FIG. 9B is an illustration of the shunt shown in FIG. 9A in its shunted state.  
         [0018]    [0018]FIG. 9C is an illustration of the shunt shown in FIG. 9A in its pre-activated state.  
         [0019]    [0019]FIG. 10 is a top view of a shunt in accordance with a fifth embodiment of the present invention in its pre-activated state.  
         [0020]    FIGS.  11 A- 11 D are detailed cross sectional illustrations of the shunt shown in FIG. 10 as it is driven from its pre-activated to its activated state.  
         [0021]    [0021]FIG. 12 is a detailed side view of the shunt shown in FIG. 10 in its shunted state. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    A suspension flexure  8  (i.e., a suspension component) which includes a plurality of switchable shunts  10  in accordance with a first embodiment of the present invention is illustrated in FIG. 1. In the embodiment shown, the flexure  8  is an integrated lead-type component which is manufactured as a separate unit and mounted to a load beam  12 . The load beam  12  is shown mounted to an actuator arm  14 .  
         [0023]    Shunts  10  are located on a tail  16  at the proximal end of the flexure  8 . Also located on the tail  16  are terminal pads  18 . Each terminal pad  18  is connected to an integrated lead section  20  which extends from the terminal pad to head terminals  21  at a head slider mounting region  22  on a distal end of the flexure  8 . Although not shown, head sliders having magneto restrictive (MR) or other heads will be mounted to the slider mounting region  22  and electrically connected to the head terminals  21 . Each of the shunts  10  is electrically connected to one of the terminal pads  18  by an integrated lead section  24 .  
         [0024]    [0024]FIG. 2 is a cross sectional view of a portion of a laminated sheet of material  30  from which the flexure  8  and shunts  10  can be manufactured. The sheet of material  30  includes a copper or copper alloy layer  32  (i.e., a conductor layer) and a stainless steel layer  34  (i.e., a spring metal layer) separated by a polyimide layer  36  (i.e., an insulator layer). As described in greater detail below, certain electrical signal-conducting features of the flexure  8  and shunts  10 , including the integrated leads  20  and  24 , are formed in the copper alloy layer  32 . Certain structural features of the flexure  8  and shunts  10 , including the head slider mounting region  22  and a base of the shunts, are formed in the stainless steel layer  34 . Polyimide layer  36  is formed into sections which electrically isolate signal-conducting features in the copper alloy layer  32  from each other and from the stainless steel layer  34 . Conventional or otherwise known photolithographic and etching techniques can be used to form the flexure  8  and shunts  10  from laminated sheets of material  30 .  
         [0025]    [0025]FIG. 3 is a detailed illustration of the proximal section of the flexure tail  16  at which the terminal pads  18  and shunts  10  are located. As shown, each of the terminal pads  18  is connected to one of the lead sections  20 . Similarly, each of the shunts  10  is connected to an associated terminal pad  18  by a lead section  24 . The shunts  10  are shown in their pre-activated state in FIG. 3.  
         [0026]    [0026]FIG. 4 is a detailed sectional view of a portion of one of the shunts  10  in its pre-activated state. As shown, the shunt  10  includes a contact arm  40 , contact pads  44  and contact base  48 . Contact arm  40  extends into a gap  42  and is electrically connected to an associated lead section  24 . The contact arm  40  includes an enlarged test pad  46  in the embodiment shown. The upper or first surface of the contact arm  40 , contact pad  44  and test pad  46  are all formed as unitary or integral features from the copper alloy layer  32  of a laminated sheet of material such as  30 . In the embodiment shown, the contact arm  40  and test pad  46  also include features formed from the polyimide layer  36  and stainless steel layer  34 . Other embodiments have a contact arm  40  and test pad  46  having features formed from only the copper alloy layer  32 , or formed from the copper alloy layer and polyimide layer  36 , but not the stainless steel layer  34 . Generally, whether the contact arm  40  or test pad  46  include features formed from the polyimide layer  36  and/or the stainless steel layer  34  will depend upon factors such as whether the amount of bias force created by the features in the other layers (e.g., the copper alloy layer  32 ) is sufficient to enable the shunt  10  to operate in the manner described below.  
         [0027]    Contact pads  44  extend from an end of the arm  40  across the gap  42 . The contact pads  44  in the embodiment shown in FIGS. 3 and 4 include features formed from only the copper alloy layer  32 . Other embodiments of the contact pads  44  (not shown) also include features formed from the polymide layer  36  and/or the stainless steel layer  34 . A pad support portion  45  of the flexure tail  16  over which the contact pads  44  lay when the shunt  10  is in the pre-activated state shown in FIGS. 3 and 4, (i.e., the area opposite the gap  42  from the contact arm  40  and under the contact pads) has the copper alloy layer  32  removed (or conductor otherwise not present) to electrically isolate the contact pads from electrical features other than the associated contact arm and lead section  24 . Although the contact pads  44  are shown as a pair of elongated elements in the embodiments illustrated in FIGS. 3 and 4, the one or more than two contact pads can be incorporated onto each shunt  10 . Similarly, the contact pads  44  can be formed as different shapes.  
         [0028]    Contact base  48  is located on the stainless steel layer  34  on the side opposite from the location of the contact pads  44  when the contact pads are in the pre-activated state. The contact base  48  is effectively located on a second or lower side of the shunt  10 .  
         [0029]    The operation of switchable shunts  10  can be described with reference to FIGS. 4 and 5A- 5 C. When in the pre-activated state shown in FIG. 4, the contact pad is electrically isolated from all electrical components of the flexure  8  and load beam  12  other than the associated lead sections  20  and  24 , terminal pad  18  and head terminal  21 . The shunt  10  is activated by forcing the contact arm  40  (e.g., by a tool  50 ) through the gap  42  toward the lower side (i.e., the side with the stainless steel layer  34 ). The activation force is applied to bend the contact arm  40  within its range of elastic deformation (i.e., against the bias force created by the material layers  32 ,  36  and  34 ). As shown in FIG. 5A, this activation motion causes the contact pads  44  to bend from their generally linear state (e.g., within their range of elastic deformation) and move through the gap  42 . With continued activation motion the contact pads  44  will pass completely through the gap  42  and resiliently return (at least partially) to their linear state as shown in FIG. 5B. After the contact pads  44  have passed completely through the gap  42 , the activation force is removed (e.g., by retracting the tool  50 ), thereby allowing the bias force of the contact arm  40  to return the arm toward its pre-activated state. This return motion will stop when the shunt is in the shunted state shown in FIG. 5C with the contact pads  44  engaged with the contact base  48 . When the shunt  10  is in the shunted state shown in FIG. 5C, the associated lead sections  20  and  24 , terminal pad  18  and head terminal  21  of the shunt are electrically interconnected to the stainless steel layer  34  of the flexure  8 . A head (not shown) mounted to the flexure  8  is thereby effectively grounded to the load beam  12 .  
         [0030]    When it is desired to perform an electrical test on the integrated lead flexure  10  (e.g., lead sections  20  and  24 , terminal pad  18  and/or head terminal  21 ) or a head (not shown) mounted thereto, a probe can be engaged with the test pad  46  to bend the contact arm  40  within its range of elastic deformation in the direction of the lower surface to force the shunt  10  into its electrically open state with the contact pads  44  disengaged from the contact base  48  (e.g., as shown in FIG. 5B). The electrical test system probe (not shown) can be manipulated to move the shunt to the electrically open state while the electrical test is being performed. When the electrical test is completed, the shunt  10  is returned to its shunted state (shown in FIG. 5C) by removing the force applied to the test pad  46  by the probe.  
         [0031]    Shunt  110 , a second embodiment of the invention, is illustrated in FIGS. 6A and 6B. Shunt  110  is similar in many respects to shunt  10  described above, and similar features are identified by corresponding reference numbers. The shunt  110  is shown in its electrically open state in FIG. 6A, and in its shunted state in FIG. 6B. Shunt  110  has only one contact arm  140  on which a plurality of leads  124  and associated contact pads  144  are located. No stainless steel layer  134  is present on the contact arm  140  in the embodiment shown. The overlap between the contact pads  144  on the contact arm  140  and the contact base  148  is caused by bends  160  in the side arms  162  in the stainless steel layer  134 . The bends  160  effectively shorten the distance between the contact arm  140  and the contact base  148 . Through the actuation of the one contact arm  140 , all the leads  124  can be effectively simultaneously switched between their shunted and electrically open states.  
         [0032]    [0032]FIGS. 7A and 7B illustrate several steps in the process by which the shunt  110  can be fabricated. As shown in FIG. 7A, following the formation of the gap  142 , the contact arm is formed by severing the adjacent sections of the leads  124  at a location adjacent to the contact pads  144 . When the contact arm  146  is forced downwardly against the bias force provided by the insulating layer  136  and copper alloy layer  132  as shown in FIG. 7B, the bends  160  can be formed in the arms  162 .  
         [0033]    Shunt  210 , a third embodiment of the present invention, is illustrated in FIG. 8. Shunt  210  is similar to shunt  110  described above, and similar features are identified with similar reference numbers. As shown, the contact base  248  includes a section  249  of added conductive material to function as a common ground. Conductive material section  249  can be an extension from the base load beam material, carrier strip or a separate component. Shunt  210  offers many of the advantages of shunt  110 , but does not require the vertical space needed for the bent side arms  162  of the shunt  110 .  
         [0034]    Shunt  310 , a fourth embodiment of the present invention, is illustrated in FIGS.  9 A- 9 C. Shunt  310  is similar to shunt  10  described above, and similar features are identified with similar reference numbers. As shown, the contact base  348  is located on a tab  351  which extends into the gap  342  from a location opposite the contact arm  340 . The shunt  310  is shown in its electrically open state in FIG. 9A, in its shunted state in FIG. 9B, and in its pre-activated state in FIG. 9C.  
         [0035]    Shunt  410 , a fifth embodiment of the present invention, is illustrated in FIG. 10. Features of shunt  410  which are structurally and/or functionally similar to those of shunt  10  described above are identified with similar reference numbers. The shunt  410  is shown in its pre-activated state in FIG. 10. As shown, the shunt  410  includes a contact arm  440  having two shunt elements  482 . Unlike the contact arm  40  of shunt  10  described above, arm  440  is connected to the flexure tail  416  at both ends and is not a cantilever structure. Each of the shunt elements  482  performs a shunting function for one associated lead  424 , and is T-shaped with a pair of opposed contact pads  444 A and  444 B extending from a central connection  441  which couples the contact pads to the associated lead. Shunt  410  also includes a pair of contact bases  448 A and  448 B associated with the contact pads  444 A and  444 B, respectively. As shown, the contact bases  448 A and  448 B are located on tabs  451  A and  451 B which extend into the gaps  442  toward the associated contact bases  448 A and  448 B, respectively.  
         [0036]    FIGS.  11 A- 11 D illustrate the activation of shunt  410  through the use of tool  450 . As shown, when the tool  450  engages and forces the contact arm  440  toward its activated state, both contact pads  444 A and  444 B of both shunt elements  482  pass through the gap  442 . When activated, the contact pads  444 A and  444 B are bent through a range of plastic deformation and are permanently bent toward the contact bases  448 A and  448 B, respectively. However, motion of the contact pads  444 A and  444 B in the range of elastic deformation causes the contact pads to extend under the contact bases  448 A and  448 B, respectively, when the force on the contact arm  440  is removed. FIGS. 11D and 12 illustrate the engagement of contact pads  444 A and  444 B with the contact bases  448 A and  448 B when the shunt  410  is in its shunted state. Both leads  424  which are shunted by shunt  410  can be switched between their shunted and electrically open states by the actuation of the contact arm  440 . An advantage of shunt  410  is the minimization of the bending or bowing of the flexure tail  416  when the shunt is in its shunted state as a result of the balancing of the forces caused by the engagement of the contact pads  444 A and  444 B with the contact bases  448 A and  448 B, respectively.  
         [0037]    The switchable shunts described above offer important advantages. They are effectively and conveniently switchable, allowing tests to be performed on the suspension or heads and the suspension or heads subsequently reshunted. Probes of test instruments can be urged into contact with the test pads, and at the same time move the shunt to its open state to permit the test to be performed. In effect, the deshunting step is performed automatically when the test instrument probe is applied. When the instrument probe is withdrawn, the shunt is returned to its shunted state. In the shunted state the shunt has low resistance. The shunt can be formed in a laminated structure-type suspension or component using conventional manufacturing processes (i.e., etching) without additional (i.e., shunt-specific) steps. The shunts can also be formed by so-called “additive” and other processes. They are compact structures which take up little space on the suspension or component. The shunts or portions thereof can be cut from the suspension (detabbed) following completion of manufacturing and test operations to “permanently” deshunt the suspension, without interfering with the terminal pads on the leads.  
         [0038]    Although the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention.