Abstract:
An assembly comprises a flex circuit including a first set of electrical contacts on a first side of the flex circuit and a compliant support backing adjacent a second side of the flex circuit and opposite the set of electrical contacts. The first set of electrical contacts is configured to connect to a second set of electrical contacts on an electronic component. The compliant support backing includes a set of support elements that individually support the first set of electrical contacts to increase the contact pressure between the first set of electrical contacts and the second set of electrical contacts when the flex circuit is connected to the electronic component. Embodiments may provide robust electrical contracts which provide a reliable connection useful for testing electronic components, such as head gimbal assemblies.

Description:
TECHNICAL FIELD 
     The invention relates to electrical contacts for electrical circuits. 
     BACKGROUND 
     Testing of electrical components for electronic devices is often performed to ensure the components are functional and perform within specified limits. During such testing, electric components that fail to meet the specified limits may be removed from the supply of electrical components used in the assembly of an electric device. Testing the functionality of electrical components can require reliable and repeatable electric connection between a testing device and a multitude of electrical components. 
     For example, in the disc drive industry, head gimbal assemblies (HGAs) may be individually tested prior to installation in a disc drive. Testing requires a reliable high bandwidth electric interconnect with an HGA. The electric interconnect generally includes a connection between a set of electrical contacts on the HGA and a corresponding set of electrical contacts on a testing module. As disc drives become smaller, electrical contacts of HGAs also become smaller, which complicates the ability to form a reliable connection with an HGA during testing. 
     SUMMARY 
     The electrical contacts on a testing module that connect to head gimbal assemblies (HGAs) may become unusable as a result of repeated use. Electrical contacts may degrade analog signals from HGAs thereby preventing accurate testing of the HGAs. For example, a broken solder joint that connects one of the electrical contacts to a trace on a circuit of the testing module would make the electrical contacts unusable. As another example, worn electrical contact surfaces may significantly degrade signals passing over electrical contacts. Worn-out or broken electrical contracts on a testing module can prevent accurate testing of HGAs. 
     In general, the invention is directed to techniques for reliably forming an electrical connection between two sets of electrical contacts. One set of electrical contacts is part of a flex circuit. A compliant support backing provides stiffness to the portion of the flex circuit including the set of electrical contacts. The electrical contacts may include over plating on pads such that the electrical contacts are raised relative to other traces on the flex circuit. In some embodiments, a compliant support backing that supports electrical contacts includes a plurality of fingers to support each electrical contact separately. This may increase the reliability of a connection that utilizes the electrical contacts on the flex circuit. 
     In one embodiment, the invention is directed to an assembly comprising a flex circuit including a first set of electrical contacts on a first side of the flex circuit and a compliant support backing adjacent a second side of the flex circuit and opposite the set of electrical contacts. The first set of electrical contacts is configured to connect to a second set of electrical contacts on an electronic component. The compliant support backing includes a set of support elements that individually support the first set of electrical contacts to increase contact pressure between the first set of electrical contacts and the second set of electrical contacts when the flex circuit is connected to the electronic component. 
     In another embodiment, the invention is directed to a circuit comprising a substrate, a set of traces that terminate near an edge of the substrate and a set of plated electrical contacts that connect to the set of traces, wherein the set of plated electrical contacts is located near the edge of the substrate. 
     In another embodiment, the invention is directed to a method comprising positioning a flex circuit having a first set of electrical contacts to connect the first set of electrical contacts with a second set of electrical contacts of a head gimbal assembly (HGA). The flex circuit is part of an assembly that further includes a compliant support backing adjacent to the flex circuit and opposite the first set of electrical contacts. The compliant support backing supports the flex circuit to allow increased contact pressure between the second set of electrical contacts and the first set of electrical contacts. The method further includes positioning the HGA adjacent to a rotating disc such that the HGA is supported by an air bearing between the rotating disc and the HGA. 
     Embodiments of the invention may provide one or more of the following advantages. In particular, embodiments of the invention may provide electrical contacts without solder joint or other intermediate connection device between the trace of a flex circuit and a separate electrical contact. In this manner, embodiments may provide robust electrical contacts useful in testing equipment for separately testing electronic components. Furthermore, embodiments of the invention provide sets of electrical contacts wherein each of the electrical contacts is individually compliant. This may provide a consistent connection force between electrical contacts, even if electrical contacts are worn and may increase the speed at which connecting electrical contacts creates useable electrical connections. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS. 1A-1C  illustrate an assembly including a flex circuit mounted between a bottom cover and a top cover. The top cover includes a compliant support backing for a plurality for electrical contacts on the flex circuit. 
         FIGS. 2A-2C  illustrate techniques for testing a head gimbal assembly (HGA) that utilize the assembly of  FIGS. 1A-1C  to provide an electrical connection between the HGA and a test module. 
         FIG. 3  illustrates a flex circuit design that provides an alternative to the flex circuit included in the assembly of  FIGS. 1A-1C . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1A-1C  illustrate a wide view of assembly  100 . Assembly  100  includes flex circuit  102  with electrical contacts  112 A- 112 E (“contacts  112 ”). Assembly  100  also includes top cover  104  with compliant support backing  120  and bottom cover  106 . In this description, the terms top and bottom are merely relative and are not meant to indicate any particular orientation of assembly  100  or its components. For reference,  FIG. 1A  illustrates an exploded view of assembly  100 , and  FIG. 1B  illustrates a collapsed view of assembly  100 .  FIG. 1C  illustrates a close-up view of electrical contacts  112  and compliant support backing  120 . 
     Flex circuit  102  is sandwiched between bottom cover  106  and top cover  104 . Bottom cover  106  includes recess  121 , which is sized to hold flex circuit  102 . In particular, recess  121  provides clearance for electrical components on flex circuit  102 . Bottom cover  106  also includes slot  124  to allow electrical contacts  112  to fit outside recess  121  and slot  122  to allow flex circuit tail  116  to fit outside recess  121 . Bottom cover  106  substantially covers the bottom side of flex circuit  102  except for a portion adjacent to electrical contacts  112 . Top cover  104  substantially covers the top side of flex circuit  102  and includes compliant support backing  120  adjacent to electrical contacts  112 . Bottom cover  106  and top cover  104  may be made from metal, such as aluminum or stainless steel, plastic or other material. As shown in  FIG. 1B , bottom cover  106  and top cover  104  combine to substantially enclose flex circuit  102 . 
     Flex circuit  102  includes electrical contacts  112 , which are configured to connect to electrical contacts on a separate electronic component, such as a head gimbal assembly (HGA). Flex circuit  102  comprises a flexible substrate. For example, the flexible substrate may comprise plastic, thin-metal film and/or other flexible material. Traces  118  are formed on top of the substrate. Traces  118 , which provide electrical connections either directly or through additional electronic components (not shown) between electrical contacts  112  and flex circuit tail  116 . Traces  118  terminate at electrical contacts  112 , which are located near an edge of the substrate. In one embodiment, traces  118  may be continuous copper traces. 
     In a typical embodiment, read/write interface device  114  is connected to traces  118  adjacent to electrical contacts  112 . The location of read/write interface device  114  minimizes distortion of a signal transferred over electrical contacts  112  by minimizing the electrical length of the unamplified signal between read/write interface device  114  and contacts  112 . Additionally, traces  118  and electrical contacts  112  can be designed in such a way as to provide a controlled impedance signal path (transmission line). Flex circuit  102  may further include additional electronic components (not shown), e.g., components to process signals received via electrical contacts  112 . 
     As shown in  FIG. 1C , electrical contacts  112  include raised pads  113 A- 113 E (“pads  113 ”). Pads  113  are part of electrical contacts  112  and comprise an electrically conductive material, such as copper. Pads  113  are higher than traces  118  and the other portions of electrical contacts  112 . As an example, pads  113  may be formed using plating techniques. In such an example, pads  113  may be formed from one or more layers over plated directly on top of electrical contacts  112 . One advantage of plating techniques is that no solder is required to attach pads  113  to the remaining portions of electrical contacts  112 , which prevents mechanical stress problems associated with a solder joint. 
     Electrical contacts  112  are separated by slits  117 A- 117 D (“slits  117 ”). Slits  117  are reliefs that allow each of electrical contacts  112  to move independently on separate fingers  119 A- 119 E (“fingers  119 ”). This may improve connections between electrical contacts  112  and electrical contacts on a device that connects to assembly  100  via electrical contacts  112 . For example, as shown in  FIGS. 2A-2C , an HGA may connect to assembly  100  via electrical contacts  112 . 
     Electrical contacts  112  are supported by compliant support backing  120 , which is part of top cover  104 . Compliant support backing  120  is stiffer than the substrate of flex circuit  102 . Generally, compliant support backing  120  is the same material as top cover  104 . For example, compliant support backing  120  may be made from metal, such as aluminum or stainless steel, plastic or other material. Compliant support backing  120  includes support elements  121 A- 121 E (“support elements  121 ”). Support elements  121  individually support electrical contacts  112 . The stiffness of support elements  121  provides a consistent contact pressure between contact pads  113  and a corresponding set of electrical contacts that connect to contact pads  113 . An exemplary system that includes a set of electrical contacts individually supported by support elements to increase contact pressure between the electrical contacts and electrical contacts on a separate device is shown in  FIG. 2C . 
       FIGS. 2A-2C  illustrate perspective views for testing head gimbal assembly  240  (HGA  240 ). As shown in  FIG. 2C , assembly  100  of  FIG. 1  provides connection  218  between HGA  240  and test module  290 . HGA  240  includes head  241 , which flies above the surface of a disc and contains read and write transducers. The operation of transducers on head  241  is controlled via electrical contacts  242 . Head  241  is supported by load beam  249 . Load beam  249  provides a spring force to hold HGA  240  adjacent to a rotating disc such as test disc  260 . For example, load beam  249  may be a thin, metal structure. 
     In  FIG. 2A , HGA  240  is placed on base  250 . For example, HGA  240  may be placed on base  250  using automated pick and place techniques. HGA  240  includes boss hole  247 , which lines up boss hole pin  251  on base  250 . HGA  240  may also include one or more alignment holes (not shown) that line up with alignment pins (not shown) on base  250 . Techniques for precisely mounting an HGA are described in United States Patent Publication 2005/020979 by Anderson et al., the entire content of which is incorporated herein by reference. As HGA  240  is placed on base  250 , HGA tail  243  is also pushed into position. Base  250  also includes vacuum slots  252 , which use suction to hold HGA tail  243  securely to base  250 . The described techniques to precisely position HGA  240  on base  250  are merely exemplary and other techniques to position HGA  240  on base  250  may be used. 
     In  FIG. 2B , after HGA  240  is placed on base  250 , assembly  100  is moved into position to clamps HGA tail  243  against base  250 . This forms a connection between electrical contacts  112  and electrical contacts  242 . Assembly  100  clamps HGA tail  243  against base  250 . Assembly  100  may be moved automatically using a linkage, using linear actuators or by using other techniques. Assembly  100  is lowered adjacent to base  250  such that electrical contacts  112  press on electrical contacts  242 . Support elements  121  (labeled in  FIG. 1C ) of support backing  120  individually support electrical contacts  112  to provide a consistent contact pressure between electrical contacts  112  and electrical contacts  242  on HGA  240 . 
     In  FIG. 2C , base  250  is moved to locate HGA  240  adjacent to test disc  260  as test disc  260  rotates. For example, base  250  may be connected to a mechanism, such as a four-bar linkage, to locate HGA  240  adjacent to test disc  260 . The movement of base  250  may be precisely controlled to prevent head  241  from contacting test disc  260 . Once HGA  240  is adjacent to test disc  260 , head  241  is prevented from contacting test disc  260  by air bearing  247 , which forms between head  241  test disc  260  as a result of the fluid (air) flow created by the rotation of test disc  260 . Load beam  249  provides a spring force to hold head  241  adjacent to test disc  260 . 
     Also shown in  FIG. 2C , flex circuit tail  116  is connected to test module  290 . In some embodiments, flex circuit tail  116  may be connected to test module  290  throughout the positioning of assembly  100 , which in other embodiments flex circuit tail  116  may be connected to test module  290  after electrical contacts  112  are connected to electrical contacts  242 . Connection  218  connects test module  290  to HGA  240  to allow test module  290  to control and perform test operations on HGA  240 . For example, test module  290  may perform read and write operations on test disc  260  at one or more radii on test disc  260 . During testing of HGA  240 , test module  290  may determine if HGA  240  meets defined standards required for including HGA  240  in a disc drive assembly. The defined standards may include minimum signal strength, fly height and/or other standards necessary to ensure proper operation of HGA  240  in a disc drive assembly. 
       FIG. 3  illustrates a portion of assembly  300 , which is substantially similar to assembly  100  ( FIGS. 1A-1C ) except that flex circuit  302  does not include slits. For brevity, details of the assembly including flex circuit  302  that are the same or similar to assembly  100  are not discussed in great detail with respect to  FIG. 3 . 
     Flex circuit  302  is mounted between bottom cover  306  and top cover  304 . Top cover  304  includes compliant support backing  320 . Bottom cover  306  and top cover  304  may be made from metal, such as aluminum or stainless steel, plastic or other material. Bottom cover  306  and top cover  304  combine to substantially enclose flex circuit  302 . 
     Flex circuit  302  includes electrical contacts  312 A- 312 E (“electrical contacts  312 ”), which are configured to connect to electrical contacts on a separate electronic component, such as an HGA. As shown in  FIG. 3 , electrical contacts  312  include raised pads  313 A- 113 E (“pads  313 ”). Pads  313  are part of electrical contacts  312  and comprise an electrically conductive material, such as copper. Pads  313  are higher than traces  318  and the other portions of electrical contacts  312 . As an example, pads  313  may be formed using plating techniques. In such an example, pads  313  may be formed from one or more layers over plated directly on top of electrical contacts  312 . One advantage of plating techniques is that no solder is required to attach pads  313  to the remaining portions of electrical contacts  312 . 
     Electrical contacts  312  are supported by compliant support backing  320 , which is part of top cover  304 . Compliant support backing  320  is much stiffer than the substrate of flex circuit  302 . Generally, compliant support backing  320  is the same material as top cover  304 . For example, compliant support backing  320  may be made from metal, such as aluminum or stainless steel, plastic or other material. Compliant support backing  320  includes support elements  321 A- 321 E (“support elements  321 ”). Support elements  321  individually support electrical contacts  312 . The stiffness of support elements  321  provide a consistent contact pressure between electrical contacts  312  and electrical contacts on a device that connects to assembly  300 . 
     Flex circuit  302  comprises a flexible substrate. For example, the flexible substrate may comprise plastic, a thin-metal film and/or other flexible material. The flexible substrate has enough flexibility such that electrical contacts  312  can move independently in conjunction with support elements  321 . As compared to flex circuit  102 , flex circuit  302  may maintain electrical contact  312  in a more consistent position than electrical contacts  112  of flex circuit  102  because flex circuit  312  does not include slits  117 , which may allow fingers  119  to overlap or separate. This may increase the reliability of a connection with electrical contacts on a separate electronic device, such as an HGA. 
     Various embodiments of the invention have been described. However, various modifications can be made to the described embodiments. For example, embodiments were described with respect to a flex circuit in conjunction with a compliant support backing. In other embodiments, substrate of a circuit including a set of electrical contacts may be both compliant and sufficiently stiff to provide sufficient contact pressure between the set of electrical contacts an electrical contacts of a separate device. These and other embodiments are within the scope of the following claims.