Electrical contacts with compliant supports

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.

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.

DETAILED DESCRIPTION

FIGS. 1A-1Cillustrate a wide view of assembly100. Assembly100includes flex circuit102with electrical contacts112A-112E (“contacts112”). Assembly100also includes top cover104with compliant support backing120and bottom cover106. In this description, the terms top and bottom are merely relative and are not meant to indicate any particular orientation of assembly100or its components. For reference,FIG. 1Aillustrates an exploded view of assembly100, andFIG. 1Billustrates a collapsed view of assembly100.FIG. 1Cillustrates a close-up view of electrical contacts112and compliant support backing120.

Flex circuit102is sandwiched between bottom cover106and top cover104. Bottom cover106includes recess121, which is sized to hold flex circuit102. In particular, recess121provides clearance for electrical components on flex circuit102. Bottom cover106also includes slot124to allow electrical contacts112to fit outside recess121and slot122to allow flex circuit tail116to fit outside recess121. Bottom cover106substantially covers the bottom side of flex circuit102except for a portion adjacent to electrical contacts112. Top cover104substantially covers the top side of flex circuit102and includes compliant support backing120adjacent to electrical contacts112. Bottom cover106and top cover104may be made from metal, such as aluminum or stainless steel, plastic or other material. As shown inFIG. 1B, bottom cover106and top cover104combine to substantially enclose flex circuit102.

Flex circuit102includes electrical contacts112, which are configured to connect to electrical contacts on a separate electronic component, such as a head gimbal assembly (HGA). Flex circuit102comprises a flexible substrate. For example, the flexible substrate may comprise plastic, thin-metal film and/or other flexible material. Traces118are formed on top of the substrate. Traces118, which provide electrical connections either directly or through additional electronic components (not shown) between electrical contacts112and flex circuit tail116. Traces118terminate at electrical contacts112, which are located near an edge of the substrate. In one embodiment, traces118may be continuous copper traces.

In a typical embodiment, read/write interface device114is connected to traces118adjacent to electrical contacts112. The location of read/write interface device114minimizes distortion of a signal transferred over electrical contacts112by minimizing the electrical length of the unamplified signal between read/write interface device114and contacts112. Additionally, traces118and electrical contacts112can be designed in such a way as to provide a controlled impedance signal path (transmission line). Flex circuit102may further include additional electronic components (not shown), e.g., components to process signals received via electrical contacts112.

As shown inFIG. 1C, electrical contacts112include raised pads113A-113E (“pads113”). Pads113are part of electrical contacts112and comprise an electrically conductive material, such as copper. Pads113are higher than traces118and the other portions of electrical contacts112. As an example, pads113may be formed using plating techniques. In such an example, pads113may be formed from one or more layers over plated directly on top of electrical contacts112. One advantage of plating techniques is that no solder is required to attach pads113to the remaining portions of electrical contacts112, which prevents mechanical stress problems associated with a solder joint.

Electrical contacts112are separated by slits117A-117D (“slits117”). Slits117are reliefs that allow each of electrical contacts112to move independently on separate fingers119A-119E (“fingers119”). This may improve connections between electrical contacts112and electrical contacts on a device that connects to assembly100via electrical contacts112. For example, as shown inFIGS. 2A-2C, an HGA may connect to assembly100via electrical contacts112.

Electrical contacts112are supported by compliant support backing120, which is part of top cover104. Compliant support backing120is stiffer than the substrate of flex circuit102. Generally, compliant support backing120is the same material as top cover104. For example, compliant support backing120may be made from metal, such as aluminum or stainless steel, plastic or other material. Compliant support backing120includes support elements121A-121E (“support elements121”). Support elements121individually support electrical contacts112. The stiffness of support elements121provides a consistent contact pressure between contact pads113and a corresponding set of electrical contacts that connect to contact pads113. 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 inFIG. 2C.

FIGS. 2A-2Cillustrate perspective views for testing head gimbal assembly240(HGA240). As shown inFIG. 2C, assembly100ofFIG. 1provides connection218between HGA240and test module290. HGA240includes head241, which flies above the surface of a disc and contains read and write transducers. The operation of transducers on head241is controlled via electrical contacts242. Head241is supported by load beam249. Load beam249provides a spring force to hold HGA240adjacent to a rotating disc such as test disc260. For example, load beam249may be a thin, metal structure.

InFIG. 2A, HGA240is placed on base250. For example, HGA240may be placed on base250using automated pick and place techniques. HGA240includes boss hole247, which lines up boss hole pin251on base250. HGA240may also include one or more alignment holes (not shown) that line up with alignment pins (not shown) on base250. 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 HGA240is placed on base250, HGA tail243is also pushed into position. Base250also includes vacuum slots252, which use suction to hold HGA tail243securely to base250. The described techniques to precisely position HGA240on base250are merely exemplary and other techniques to position HGA240on base250may be used.

InFIG. 2B, after HGA240is placed on base250, assembly100is moved into position to clamps HGA tail243against base250. This forms a connection between electrical contacts112and electrical contacts242. Assembly100clamps HGA tail243against base250. Assembly100may be moved automatically using a linkage, using linear actuators or by using other techniques. Assembly100is lowered adjacent to base250such that electrical contacts112press on electrical contacts242. Support elements121(labeled inFIG. 1C) of support backing120individually support electrical contacts112to provide a consistent contact pressure between electrical contacts112and electrical contacts242on HGA240.

InFIG. 2C, base250is moved to locate HGA240adjacent to test disc260as test disc260rotates. For example, base250may be connected to a mechanism, such as a four-bar linkage, to locate HGA240adjacent to test disc260. The movement of base250may be precisely controlled to prevent head241from contacting test disc260. Once HGA240is adjacent to test disc260, head241is prevented from contacting test disc260by air bearing247, which forms between head241test disc260as a result of the fluid (air) flow created by the rotation of test disc260. Load beam249provides a spring force to hold head241adjacent to test disc260.

Also shown inFIG. 2C, flex circuit tail116is connected to test module290. In some embodiments, flex circuit tail116may be connected to test module290throughout the positioning of assembly100, which in other embodiments flex circuit tail116may be connected to test module290after electrical contacts112are connected to electrical contacts242. Connection218connects test module290to HGA240to allow test module290to control and perform test operations on HGA240. For example, test module290may perform read and write operations on test disc260at one or more radii on test disc260. During testing of HGA240, test module290may determine if HGA240meets defined standards required for including HGA240in a disc drive assembly. The defined standards may include minimum signal strength, fly height and/or other standards necessary to ensure proper operation of HGA240in a disc drive assembly.

FIG. 3illustrates a portion of assembly300, which is substantially similar to assembly100(FIGS. 1A-1C) except that flex circuit302does not include slits. For brevity, details of the assembly including flex circuit302that are the same or similar to assembly100are not discussed in great detail with respect toFIG. 3.

Flex circuit302is mounted between bottom cover306and top cover304. Top cover304includes compliant support backing320. Bottom cover306and top cover304may be made from metal, such as aluminum or stainless steel, plastic or other material. Bottom cover306and top cover304combine to substantially enclose flex circuit302.

Flex circuit302includes electrical contacts312A-312E (“electrical contacts312”), which are configured to connect to electrical contacts on a separate electronic component, such as an HGA. As shown inFIG. 3, electrical contacts312include raised pads313A-113E (“pads313”). Pads313are part of electrical contacts312and comprise an electrically conductive material, such as copper. Pads313are higher than traces318and the other portions of electrical contacts312. As an example, pads313may be formed using plating techniques. In such an example, pads313may be formed from one or more layers over plated directly on top of electrical contacts312. One advantage of plating techniques is that no solder is required to attach pads313to the remaining portions of electrical contacts312.

Electrical contacts312are supported by compliant support backing320, which is part of top cover304. Compliant support backing320is much stiffer than the substrate of flex circuit302. Generally, compliant support backing320is the same material as top cover304. For example, compliant support backing320may be made from metal, such as aluminum or stainless steel, plastic or other material. Compliant support backing320includes support elements321A-321E (“support elements321”). Support elements321individually support electrical contacts312. The stiffness of support elements321provide a consistent contact pressure between electrical contacts312and electrical contacts on a device that connects to assembly300.

Flex circuit302comprises 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 contacts312can move independently in conjunction with support elements321. As compared to flex circuit102, flex circuit302may maintain electrical contact312in a more consistent position than electrical contacts112of flex circuit102because flex circuit312does not include slits117, which may allow fingers119to 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.