Patent Application
20060050429
This invention relates to making electrical connections, and some embodiments relate to making electrical connection in a hard disk drive.
Some electrically operated devices, such as data storage devices, are housed in protective enclosures. Some enclosures, also referred to as housings, may be sealed for various reasons, such as to keep out contaminants. Another reason an enclosure may be sealed is to maintain an alternate atmosphere. Some alternate atmospheres may be used to obtain certain performance advantages for some electrical, mechanical, or electro-mechanical devices.
Data storage devices that may be housed in sealed enclosures include disk drives that store data on magnetic or optical disks. For example, a hard disk drive (HDD) may store data on a magnetic disk. An HDD typically includes a base into which various components of the disk drive may be installed. A top cover cooperates with the base to form an enclosure that houses electronic and electromechanical components of the disk drive. These components include, for example, a spindle motor, which rotates one or more disks at high speed. Information may be written to and read from tracks on the disks through the use of an actuator assembly. The actuator assembly may include actuator arms, which extend towards the disks, with one or more suspensions or flexures extending from each of the actuator arms. Mounted at the distal end of each of the flexures is a read/write head, which may include an air bearing slider that enables the head to fly in close proximity to the corresponding surface of the associated disk.
The actuator assembly may receive power, control, and data signals through a flexible interconnect called a flex assembly (and may also referred to as a flexible flat circuit cable, a printed circuit cable, flex circuit, or flat wiring harness). A proximal end of the flex assembly may be secured to the actuator arm near the pivot point of the actuator. The head conductors may be soldered, for example, to exposed contacts on the flex assembly. The flex assembly may also route conductors that carry currents to a voice coil motor assembly (VCMA) that may be used to position the actuator arm. Typically, the flex assembly is coupled to a preamplifier drive circuit (preamp) that may generate write currents during a write operation and pre-amplify read back signals during a read operation.
In a sealed HDD, such power, control and data signals may be coupled through a bulkhead connector extending through an aperture in the base. Internally, the bulkhead connector may be electrically coupled to a distal end of the flex assembly. Externally, the bulkhead connector may be electrically coupled to an externally-mounted printed circuit board assembly (PCBA).
In an enclosure, electrical connections to a bulkhead connector may be made using a flex spring. The flex spring may have a frame and one or more spring members supported at their proximal ends by the frame. At their distal ends, the spring members may be configured to apply a distributed load to compress a set of contacts on a flex assembly against a corresponding set of contacts on a bulkhead connector. The pressure applied by the flex spring may be distributed to make reliable electrical connection between the corresponding sets of contacts.
In one embodiment, the frame of the flex spring may be attached to a flex bracket. The flex bracket may mount to a wall of a base to which the bulkhead connector is mounted. Accordingly, the flex bracket may be used to align the flex spring to the bulkhead connector so that the loads applied by the flex spring may be distributed over the set of contacts on the bulkhead connector. In another embodiment, the flex bracket may also include one or more locating features configured to align the flex assembly with the flex bracket.
In a further embodiment, the flex bracket may include a pocket for receiving a portion of the frame of the flex spring. In some examples, the flex spring being received within the pocket of the hex bracket may reduce the height profile of the system.
In another example, the bulkhead connector may be flat. In various examples, the bulkhead connector may be a printed circuit board made of conventional materials, or a printed circuit board made using ceramic materials. In one embodiment, the flat connector (FC) may be made using a low temperature co-fired ceramic (LTCC) process.
As such, the flex spring may provide an easily manufactured, low-profile, low-cost, electrical connection to a bulkhead connector in an enclosure, such as a sealed enclosure for an HDD.
Certain embodiments may provide one or more of the following advantages. For example, the flex spring may facilitate a low profile bulkhead interface. This low profile may be compatible with, for example, robotic tooling that may be used in certain assembly operations. In addition, the flex spring may make the assembly of an apparatus with a sealed enclosure simpler and faster. A low profile bulkhead interface may also enable the sealed enclosure to contain an increased volume of other components, such as an environmental control module. Furthermore, the flex spring may be configured to exhibit low cross-talk between signals that pass through the electrical interface. Moreover, the flex spring may enable the electrical interface to exhibit reduced susceptibility to electrostatic discharge (ESD) and other forms of electromagnetic interference (EMI).
The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.
In one embodiment, a flex spring may be used to make electrical connection between a flex assembly and a bulkhead connector. The bulkhead connector may pass electrical signals through an aperture in an enclosure. In some examples, the bulkhead connector may sealably encompass the aperture to inhibit the escape of a low density gas, such as helium, for a long period of time.
In one embodiment, the flex spring provides a compressive force to make electrical connection between a set of contacts on a flex assembly and a corresponding set of contacts (i.e. exposed pads) on a bulkhead connector that is arranged as a flat printed circuit board. A bulkhead connector that is arranged as a flat printed circuit board may be referred to herein as a flat connector (FC). In combination with the flex spring, such an FC may provide a cost-effective solution for passing electrical signals through, for example, an aperture in an electrically conductive, environmentally-sealed enclosure.
One exemplary application in which a flex spring may be used to make electrical connection between a flex assembly and an FC is an environmentally-sealed data storage device. In one example, the sealed data storage device includes a helium-filled hard disk drive (HDD). Although helium-filled HDDs are described herein in various examples, these examples are merely illustrative and not intended to be limiting. The methods and devices may be applied to a wide range of electronic, electrical, mechanical, and electromechanical applications for which environmental sealing is desired. By way of example, such devices and applications may include computer systems, servers, computer peripheral devices, avionics, industrial controllers, and military electronics.
Filling disk drives with low density gasses other than air may enhance certain drive performance characteristics. For example, a low density gas, such as helium, may reduce the aerodynamic drag experienced by the spinning disks within the drive. One benefit of this may include reduced power requirements for the spindle motor. Thus, a helium-filled drive may require substantially less power than a comparable, air-filled disk drive. Moreover, reduced drag forces within the helium-filled drive may also correspond to aerodynamic turbulence experienced by the drive components, such as the actuator arms, the suspensions, and the heads.
Other benefits may accrue to some helium-filled HDDs. The reduced power requirements and “air” turbulence may allow helium-filled drives to operate at higher speeds than equivalent air-filled drives (i.e., at the same percentage of read/write errors). Because there may be less turbulence within the helium-filled drive, the heads may fly closer to the disk surface. As a result, helium-filled drives may also enable higher storage capacities (i.e., higher recording densities).
Despite the potential advantages of helium-filled drives, such drives have not been widely used. One reason for this may relate to maintaining the helium (or other low density gas) atmosphere within the enclosure for the service life of the drive. If helium leaks out of the enclosure and is replaced by air, the performance advantages associated with the helium atmosphere may be lost and may lead also to premature drive failure. For example, the increased concentration of air may lead to increased turbulent forces on the drive heads due to the increased drag forces within the drive. This may cause the heads to fly too far away from the disk, thereby increasing the rate of read/write errors.
One way to retain the advantages of a low density atmosphere in a disk drive is to hermetically seal the drive enclosure. One challenge with hermetically sealing a disk drive enclosure relates to the cost of hermetically sealing the bulkhead connector. The bulkhead connector passes electrical signals (e.g., power, control, and data) through a wall of the enclosure.
For purposes of illustration, the use of a flex spring in an electrical interface will be described in the exemplary context of a helium-filled HDD. An exemplary HDD will first be introduced in
By way of introduction, an exemplary HDD 100 is shown in
During a seek operation, a voice coil motor 124 controls the track position of the heads 118. The voice coil motor 124 typically includes a coil 126 attached to the actuator assembly 110, as well as one or more permanent magnets 128. As the coil 126 moves, the actuator assembly 110 pivots about the bearing shaft assembly 112, the heads 118 move across the surfaces of the disks 108.
A flex assembly 130 provides electrical connection paths for the actuator assembly 110 while allowing pivotal movement of the actuator assembly 110 during operation. The flex assembly 130 includes a flex circuit 132 to which head wires (not shown) are connected. The head wires are routed along the actuator arms 114 and the flexures 115 to the heads 118. The flex circuit 132 typically includes circuitry for controlling the write currents applied to the heads 118 during a write operation, and a preamplifier for amplifying read signals generated by the heads 118 during a read operation. The flex assembly 130 is held in place by a flex bracket 134. The flex assembly provides communication through the base 102 to a disk drive printed circuit board assembly (PCB assembly) 630 shown in
The HDD 100 may be configured to operate in a helium-filled atmosphere within its enclosure. While it is possible to provide internal helium reservoirs or other systems for periodically refilling the HDD 100 with helium, a different solution to the problem of sealing enclosures is to provide a long-lasting hermetic seal that substantially maintains the helium environment during the service life of the HDD 100.
The examples described herein may illustrate such a hermetic seal through the use of a sealing cover 150. In one example, the sealing cover 150 may be welded or brazed to the base 102 or to the structural cover 104. In another example, a bottom cover may first be adhesively bonded to seal any leakage paths in the bottom of the base 102. Then, the sealing cover 150 may be sealably bonded, by welding or adhesive bonding, to the bottom cover to seal any leakage paths in the top of the base 102. In the latter example, the bottom cover and the sealing cover 150 may provide, in effect, a conductive skin that sealably envelops the base, except for an aperture for making electrical connection to the bulkhead connector.
The sealing cover 150 may be a thin-walled metal cover having a flat top surface and downward-depending sides. In some examples, the sealing cover 150 may be formed of aluminum or brass. For example, a low-profile sealing cover 150 may be formed of aluminum or brass having a thickness of approximately 0.010 inches. Such materials are characterized by a low permeability to helium or other low density gasses. In other examples, the sealing cover 150 may be formed of other materials, such as stainless steel, that are characterized by low permeability to helium.
To provide for reworkability during manufacturing and to also provide for a long-term hermetic seal, the HDD 100 may first be temporarily sealed and then be permanently sealed. The temporary seal permits rework to be readily performed if necessary. The bottom cover 220 and the structural cover 104 provide a temporary seal that maintains the helium atmosphere long enough to conduct certification testing (e.g., 1-10 days). The bottom cover 220 may be welded or adhesively bonded to the base 102. Prior to screwing the cover 104 to the base 102, a seal 170 (
The structural cover 104 may, in some examples, include a valve (not shown) for filling the HDD 100 with a low density gas, such as helium. In another example, the HDD 100 may receive a sealing cover 150 without a structural cover 104. In that case, the sealing cover 150 may be sealably attached to the HDD 100 in an appropriate environment, such as a helium environment.
According to the embodiment shown in
The base 102 and the bottom cover 220 each have an aperture 230 through which electrical signals pass between the exterior and interior of the enclosure. For example, the PCB assembly 630 (see
A new system that provides an electrical interface for hermetically sealed enclosures is shown in
The FC 400, in one example, is similar to a circuit board having multiple metallization layers. The FC 400 does not use spring-finger type contacts to conduct power, data, and control signals. Using low noise PCB design techniques, (e.g., loop area minimization, separating noisy traces from high impedance trances, etc.), traces on the FC 400 may be configured to minimize antenna structures that could contribute to cross-talk between signal conductors. Such cross-talk may increase the likelihood of read/write errors. As such, the FC 400 provides a low-profile design in which signal cross-talk and susceptibility to electromagnetic interference (EMI) and electrostatic discharge (ESD) may be minimized.
Moreover, the low-profile of the FC 400 is compatible with some robotic tooling that may be used during the assembly process, for example, to assemble the head disk assembly (HDA). Furthermore, the low-profile of the FC 400 may enable additional components to be assembled into the HDD 100. For example, an environmental control module (ECM) may be installed in the region around the FC 400 to improve the atmospheric conditions within the sealed enclosure 200.
In
The seal may be formed around the periphery of the FC 400 so as to encompass the aperture 230 (not shown). In one example, the FC 400 is adhesively bonded to the interior surface of the bottom cover 220. In another example, the FC 400 may be soldered or brazed to the interior surface of the bottom cover 220. In one example, solder paste is applied to a peripheral exposed metal ring 720 (as will be described in
The enclosure and FC 400 may be soldered using, for example, a reflow process such as may be performed in a vacuum or a neutral atmosphere reflow oven. The peripheral metal ring 720 may be plated to facilitate soldering to the base 102 or to the bottom cover 220. In one example, the peripheral metal ring and/or the base 102 may be nickel-plated. In one embodiment, tin plating may be used in addition to nickel plating.
In one example, the peripheral metal ring 720 may be configured to be electrically coupled to one or more traces on the FC 400 in order to enhance, for example, EMI and ESD protection by providing a conductive path to the metal enclosure.
The FC 400 includes exposed metal pads (i.e., electrical contacts) to which electrical connection may be made. The FC 400 includes a number of exposed metal pads 410 on the interior facing side. These interior facing pads 410 may be used to make connection to the flex assembly 130.
In
In
In
In
In
The flex spring 100 is held in compression by the flex bracket 134. In this example, the flex bracket 134 is mounted to the base 102 using mounting hardware 610. The mounting hardware 610 may include screws, rivets, snap features, and the like.
In this configuration, the flex bracket 134, the flex spring 600, and the flex assembly 130 provide structural support to the FC 400 to counteract the opposing load force from the connector 415. As such, the bonds 605 do not bear the entire load of maintaining the FC 400 in position over the aperture 230. This reduces the requirements, in some examples, for the bond 605 to have adequate strength to support the load on the FC 400 from the connector 415.
The connector 415 makes electrical connection to pads on the exterior facing surface of the FC 400. The connector may be, for example, a surface-mount style connector, or any other board-to-board or board-to-wire electrical connector suitable for making contact to the exposed metal pads of the FC 400. In this example, the connector 415 has surface-mount leads 620 that may be soldered to the pads on the FC 400. The connector 415 may make connection to the PCB assembly 630 by receiving header pins 625 coupled to the PCB assembly 630. In another example, the connector 415 may be electrically coupled to the PCB assembly 630 using, for example, spring type contacts. Other electrical interconnects may be used between the FC 400 and the PCB assembly 630, such as a ribbon cable, a compliant conductor, or a flex circuit (also referred to as a flex assembly).
As used herein, an electrical connection refers to a direct connection between conductive materials. For example, an electrical connection may be made when a copper conductor is brought into direct physical contact with an exposed conductive pad on a circuit board. A contact refers to an exposed conductive surface to which electrical connection may be made. An off-board conductor may be soldered (or otherwise connected to) a contact on a PCB. Each contact on the PCB is typically coupled, through vias or traces, to at least one other contact on the PCB. Thus, contacts on PCBs may be used to facilitate the making of electrical connections between two or more off-board conductors.
Various connector systems may be used to make electrical connection with the contacts, or pads, of the FC 400. For example, pins may be applied to make electrical contact to the exposed conductive pads on the FC 400. In other examples, pads on the FC 400 may be directly soldered to board-to-board or board-to-wire cable assemblies using, for example, surface-mount connectors or wire harnesses, respectively. In addition, the exposed pads on the FC 400 may be made into any suitable shape or configuration to sufficiently encompass the aperture to provide for sealably attaching the FC 400 to a wall of the enclosure.
In
In one embodiment, a thick film ceramic process may be used to make the FC 400. For example, a thick film ceramic process may be used to construct an FC 400 having two metallization layers on at least one layer of a substrate using, for example, a thick film ceramic process. In this example, one sheet of a planar substrate, such as a ceramic, may be sized and shaped to encompass the aperture. In one example, vias may be drilled into the substrate. Metallization may be added to opposing surfaces of each substrate and to the vias to form conductive paths, or signal traces, to make electrical connection between pads (i.e., contacts) formed on the opposing surfaces. In one embodiment, the vias are filled with a conductive metal such that no pin holes are present that would allow a gas to leak through the vias.
In another embodiment, a low temperature co-fired ceramic (LTCC) process may be used to make the FC 400. For example, an LTCC process may be used to construct an FC 400 having three metallization layers on at least two layers of substrate using, for example, the LTCC process. In this example, two sheets of a planar substrate, such as a ceramic, may be sized and shaped to encompass the aperture. In one example, vias are drilled into each substrate according, for example, to the patterns depicted in
In
To further reduce the permeability of the FC 400 to helium, for example, the metallization layers may include “ground fill” areas in which metallization, such as copper, is added to substantially all uncommitted areas of a metallization layer. Ground fill metallization may be added, for example, to surround traces, pads, and vias. Trace-to-trace spacing may be maintained at, for example, 0.010″ or less. As such, the “ground fill” metallization may further lower the permeability of the FC 400 to gasses, such as helium. In examples in which the substrate material, such as ceramic, has very low permeability to helium, such “ground fill” may be optional.
The FC 400 may be mounted to a surface of the enclosure by soldering an exposed metal ring 720 to the enclosure wall. In this example, a metallized ring 720 is not covered by a solder mask 715. No soldermask or other dielectric is placed over the peripheral exposed ring 720. As described above, the FC 400 may be soldered to a surface of the sealed enclosure by, for example, applying solder paste to the exposed peripheral ring 720. To aid in the soldering, soldermask 715 may be provided to confine the molten solder to the peripheral ring 720. On the opposite external layer shown in
In
The flex spring 600 may be made, for example, of plastic or metal. For example, the flex spring may be formed of aluminum, stainless steel, platinum, silver, copper, beryllium copper, and combinations of these and other metals suitable for use in a spring. The flex spring 600 may be made from conventional processes for making springs, some of which may involve stamping, pressing, forging, baking (i.e., for stress relief), or die cutting.
The flex bracket 134 may be made of plastics, polymers, metals, and the like. For example, the bracket 134 may be made using conventional processes for making a bracket, some of which may involve stamping, forging, die casting, machining, drilling, or injection molding.
When the flex bracket 134 is mounted with the flex spring 600 into the base 102, the spring-fingers of this example provide a distributed load to a non-conductive surface of the flex assembly 130. As such, the flex spring 600 is not in the path of the circuit formed by the conductors carrying signals on the flex assembly 130. Because the flex spring 600 does not carry current signals, the flex spring 600 does not contribute significantly to, for example, cross-talk between signals carried by conductors that pass through the FC 400. Moreover, because the flex spring 600 is electrically isolated from the conductors in the flex assembly 130, the flex spring 600 is unlikely to introduce ESD currents into the circuits coupled to the flex assembly 130 or the FC 400.
In this example, the flex bracket 134 includes a recessed pocket for receiving the peripheral frame of the flex spring 600. This pocket allows the flex bracket 134 to control the lateral position of the flex spring, and aligns the flex spring 600 relative to the flex bracket 134. In one example, the compressive load applied by the fingers of the flex spring 600 to the flex assembly may be a function of the depth of the pocket in the flex bracket.
In
According to some of the above-described embodiments, one or more FCs 400 may be used to provide sealed electrical interfaces, or a bulkhead interconnects, in various applications. In addition to the above-mentioned applications, the FC may be used to seal apertures and provide an electrical interface in enclosures such as a computing system. In
In
In one example, the server 930 includes an aperture that is sealed using the FC 400 to provide an electrical interface. In another example, the system 920 includes the server 930 and one or more workstations 940. In that example, each workstation 940 may be coupled to a display device 945 and a keyboard device 950, and use an FC 400 to provide a sealed electrical interface.
A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, high temperature ceramics may be used instead of LTCC ceramics to make a FC that is impermeable to helium. Surface-mount connectors may be used on both the interior facing and the exterior facing sides of the FC. Surface-mount style connectors may be used in various applications having hermetically sealed enclosures, such as, for example, an air-conditioning compressor or an electronic apparatus that has a controlled environment.
In one embodiment, the electrical connections to the spindle motor 106 may be made through a second flex assembly. In some examples, this second flex assembly may make electrical connection to a second bulkhead connector through a second aperture in the base 102. The second bulkhead connector may be, for example, a flat connector similar to FC 400. In one example, a bulkhead connector dedicated to interconnects for the spindle motor 106 may include three or four signal lines for operating and controlling the spindle motor 106.
Although certain examples described herein feature enclosures that are hermetically-sealed, other examples may apply to applications with reduced sealing specifications. For example, an electronic device may employ the FC to inhibit the ingress or egress of air or other gas. In another example, an electronic device may use the FC to control the ingress of contaminants, such as, dust, gasses, liquid water, water vapor, and the like.
Although some examples have been directed to applications involving hermetically-sealed enclosures, the FC may be used effectively to provide electrical connection through an aperture in an enclosure that is not hermetically sealed. For example, some applications may involve a controlled exchange of gasses between the interior of the enclosure and ambient atmosphere. By providing a sealed electrical interface, the enclosure may be configured to control the breathing (i.e. exchange of gasses) to selected locations to mitigate, for example, the negative impact of the breathing.
Various examples have been described generally as having an enclosure comprising a base portion and a cover. These examples are meant as merely illustrative. Sealed or partially sealed enclosures may comprise one or more components that, when assembled, define an enclosure for an electronic, electrical, mechanical, or electromechanical apparatus. A base portion as used herein may refer to any component of the enclosure having a wall in which electrical conductors may pass through an aperture. In general, various embodiments may be applied to seal such apertures. As such, the FC can be used to provide electrical connections to an apparatus within an enclosure without compromising the hermetic seal. As such, the FC provides a bulkhead electrical connector that has a low height profile and low cost without compromising the enclosure's ability to control of the ingress or egress of certain substances, whether in the form of a solid (e.g., dust), a liquid (e.g., water droplets), or a gas (e.g., helium).
The FC may be packaged and shipped either as an individual component, or as a sub-assembly in a kit that is combined with other components. For example, the FC may be packaged in combination with a connector that is soldered to one side of the FC. Alternatively, the FC may be packaged together with an internal wire harness sub-assembly, such as, for example, a flex circuit that may be readily installed into an HDD. As another example, an FC may be packaged in combination with any or all of the following as a kit: a connector, a wire harness sub-assembly, a flex spring, a clamp (flex bracket), mounting hardware (e.g. screws, retaining clips), and a base portion of an enclosure. The base portion of the enclosure may be pre-assembled with the FC already sealably attached over the bulkhead aperture, and any of an internal wire harness, a flex spring, or a clamp may be installed in the base. In addition, a connector, such as an external wiring harness or a surface mount connector, may be soldered to the exterior surface of the FC. In another example, any of the foregoing configurations may include a cover for the enclosure, and the cover may include mounting features (e.g. snap features) and/or mounting hardware. In an example specific to HDDs, a kit may include any of the foregoing, with any of an HDA, VCMA, spindle disk assembly, or environmental control module being installed within the base portion, and or a printed circuit board assembly (PCBA) being mounted external to the base. In the foregoing example, the FC may be electrically connected to the PCB assembly through, for example, the aforementioned external wiring harness or surface-mount connector.
Other examples may be used in a computer system to provide an environmental seal around conductors that pass through an aperture in an enclosure wall. For example, electrical signals may be passed through the wall of an enclosure containing, for example, a computer motherboard and associated components that are to be protected against the ingress of contaminants, such as dust and water. In some examples, a breather system may be included to provide for pressure equalization, and may be used in combination with desiccant and adsorbent systems. In one example, a computer system includes a helium-filled HDD that is hermetically sealed and uses an FC to pass electrical signals through a bulkhead aperture in the HDD enclosure.
In one example, after the cover 104 has been secured to the base 102, a source of helium (or another low density gas) may be connected to a valve (not shown) to fill the interior of the drive with a gas. Without being limiting, the gas could primarily be helium, but may be combined with or replaced by another suitable gas, such as another low density gas. The supply system may provide a method of evacuating the drive before filling the drive with the gas. For example, the enclosure may be filled with helium to a concentration of at least about 95 percent (at standard temperature and pressure). In such a system, an FC may provide a hermetically sealed electrical interface for passing conductors used to operate the HDD 100 in a helium-filled environment within the enclosure.
In accordance with the examples described herein, the storage device may be a magnetic disk storage device. However, other examples may include other types of disk storage devices, such as optical disks, and the like.
Accordingly, other embodiments are within the scope of the following claims.
| Number | Date | Country | |
|---|---|---|---|
| 60545910 | Feb 2004 | US |
