Patent Abstract:
The present invention provides a multilayer tape for simultaneously providing shielding of electromagnetic interference (EMI) and evidence of tampering with an electronic device to which it is applied. The multilayer tape can be attached to an electronic device to cover a seam or other opening in the electronic device. An embossed surface provides evidence of the disruption of the tape, and the tape includes a conductive adhesive to provide EMI shielding. The multilayer tape is particularly useful for sealing the seams of a disk drive device.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional Patent Application Ser. No. 60/772,333, filed on Feb. 10, 2006, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of electronic devices and in particular relates to an adhesive tape that combines the functionality of electromagnetic interference (EMI) shielding with tamper detection. The tape is particularly useful to provide tamper detection and EMI shielding for electronic components such as disk drives for the storage of data. 
     BACKGROUND 
     Security devices in the form of a multilayer tape that is adhered to the seam of an enclosure, such as a DVD case or an enclosure for electronic components, have been used where the tape includes a hologram or diffraction grating. When attempts to open the enclosure occur, the structure of the tape is disrupted and the image or pattern on the tape shows evidence of the attempt. 
     EMI shielding devices such as EMI shielding tapes are also known. EMI shielding tapes can be used to prevent electromagnetic interference between different components of an electronic device. Increasing device frequencies create decreasing electromagnetic wavelengths that can penetrate very small cracks or openings that may exist in an enclosure surrounding the electronic components. Device failures caused by EMI are increasing as the electronic components become more sensitive. Such tapes can be applied to seams, slots or gaps on the device to reduce EMI by creating a Faraday Cage around the electric components. 
     Recently, magnetic disk drives for the storage of data have been significantly reduced in size and have found use in myriad devices such as cellular telephones and personal digital assistance (PDAs). In such devices, the electromagnetic interference caused by operation of the disk drive can significantly affect the performance of the device. At the same time, disk drive manufacturers also desire to inhibit users from tampering with the device and then making false warranty claims. 
     SUMMARY OF THE INVENTION 
     According to one embodiment of the present invention, a multilayer tape that is adapted to provide evidence of tampering and also provide electromagnetic shielding is provided. The tape includes a substrate having first and second opposed surfaces where the first surface is an embossed surface. An electrically conductive material layer is disposed over the embossed surface and an electrically conductive adhesive layer is disposed on the conductive layer. The tape can advantageously be applied to an electronic device such as a disk drive by adhering the adhesive layer to the surface of the device. By virtue of the electrically conductive adhesive layer and the electrically conductive material layer, the tape advantageously provides EMI shielding when the tape is applied over a gap or seam in the device enclosure. In addition, the embossed surface can provide evidence of tampering with the electronic device when someone attempts to open the enclosure. 
     According to another embodiment, a disk drive device is provided that includes a base plate, a cover connected to the base plate to define an enclosure for housing disk drive components, and a multilayer tape that covers at least a portion of a seam between the base plate and the cover. The multilayer tape includes a security layer adapted to indicate if the base plate and cover have been disconnected, a conductive metallic layer disposed between the security layer and the seam and an electrically conductive adhesive disposed between the conductive metallic layer and the seam. The seam can be disposed around the perimeter of the disk drive device and the multilayer tape preferably covers substantially the entire seam, providing a continuous electrical connection between the cover and the base plate. 
     According to another embodiment of the present invention, a method for the manufacture of a multilayer tape structure is provided. The method includes the steps of providing a polymer substrate having first and second opposed surfaces, embossing the first surface to form an embossed surface, depositing a metallic layer onto the embossed surface and depositing a conductive adhesive onto the metallic layer. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a cross-sectional view of a multilayer tape according to an embodiment of the present invention. 
         FIG. 2  illustrates a disk drive device. 
         FIG. 3  illustrates a perspective view of an assembled disk drive device. 
         FIG. 4  illustrates a perspective view of an assembled disk drive device including a multilayer tape according to the present invention. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     A cross-sectional view of a multilayer tape  100  according to the present invention is illustrated in  FIG. 1 . The tape  100  includes a substrate  102  upon which an embossed surface  104  is formed to create a security layer. An electrically conductive material layer  106  is disposed on the embossed surface  104  and a conductive adhesive layer  108  is disposed on the conductive material layer  106 . In use, the tape  100  is adhered to an electronic device by virtue of the adhesive layer  108 . When adhered to the seam of an enclosure that surrounds the electronic device, the multilayer tape  100  advantageously provides EMI shielding and also deters unauthorized users from opening the enclosure. 
     The substrate  102  is preferably an organic polymer, for example, a polyester such as polyethylene terephthalate (PET), polypropylene, polyvinyl chloride, polyethylene naphthalate, polymethylpentene (PMP) or polyimide. The substrate should be sufficiently thin such that the substrate  102  is not opaque, thereby permitting the embossed layer  104  to be viewed when observed through the substrate  102 . In one embodiment, the substrate  102  has a thickness of at least about 10 μm and not greater than about 30 μm. 
     An embossed surface  104  is formed on one of the two opposed surfaces of the substrate  102 . An embossed surface  104  is one that includes structural discontinuities sufficient to create an optically variable surface that can be readily observed by a viewer. Thus, when the tape  100  is viewed through the substrate  102 , the viewer will see the pattern corresponding to the embossed surface  104 . The embossed surface  104  can be formed by etching the substrate  102 , such as by a laser or other application of heat. 
     Deposited on the embossed surface  104  on the opposite side of the substrate  102  is an electrically conductive material layer  106 . The electrically conductive material layer  106  can include any electrically conductive and optically reflective material. In one embodiment, the conductive material layer is a metallic layer, such as one that comprises aluminum. The conductive material layer  106  should be sufficiently thick to coat the entire embossed surface  104 , but preferably has a thickness that is less than the thickness of the substrate  102 . Preferably, the conductive material layer  106  has an average thickness of not greater than about 10 μm and more preferably not greater than about 6 μm. The conductive material layer  106  can be deposited by vapor deposition of a metal. 
     An electrically conductive adhesive layer  108  is disposed on the conductive material layer  106 . The conductive adhesive layer  108  is sufficiently electronically conductive to provide electrical conductance between the electronic device to be fitted with the multilayer tape  100  and the conductive material layer  106 , thereby providing EMI shielding to the electronic device. According to one embodiment, the conductive adhesive layer  108  has an electrical resistance of not greater than about 10 −3 Ω. Preferably, the electrical resistance of the conductive adhesive layer is not greater than about 10 −6 Ω and even more preferably is not greater than about 10 −9 Ω. The adhesive is preferably a pressure-sensitive adhesive so that the tape  100  can be applied to an electronic device using only pressure. The conductive adhesive can include an adhesive matrix and a solid electrically conductive material  110  dispersed within the adhesive matrix. For example, the solid conductive material can be selected from the group consisting of carbon, aluminum and nickel. In one preferred embodiment, the solid conductive material includes fibers, such as nickel fibers. Nickel fibers are believed to be advantageous in this application as the electronic conductance of adhesives containing nickel fibers is less sensitive to application pressure than other materials. 
     The tamper evident tape  100  can be applied to an electronic device over the seam that is formed between two portions of the enclosure of the electronic device. By way of example,  FIG. 2  illustrates a disk drive  210 . The disk drive  210  generally includes a base plate  212  and a cover (not shown) that may be disposed on the base plate  212  to define an enclosed housing or space for the various disk drive components. The disk drive  210  includes one or more data storage disks  214  of any appropriate computer-readable data storage media. Each disk  214  is mounted on a hub or spindle  216 , which in turn is rotatably interconnected with the disk drive base plate  212  and/or cover. Multiple data storage disks  214  are typically mounted in vertically spaced and parallel relation on the spindle  216 . Rotation of the disk(s)  214  is provided by a spindle motor  218  that is coupled to the spindle  216  to simultaneously spin the data storage disk(s)  214  at an appropriate rate. 
       FIG. 3  illustrates a perspective view of an assembled disk drive assembly  300 . The disk drive assembly includes a base plate  312  and a cover  314 . The cover  314  is connected to the base plate  312  utilizing threaded fasteners  316  or a similar mechanism to form an enclosure for the disk drive components, as is discussed above. Around the periphery of the disk drive device  300  is a seam  318  that is formed where the cover  314  contacts the base plate  312 . Although the seam  318  is reasonably narrow, EMI, such as that produced by operation of the disk drive motor, is capable of leaking through the seam  318 . This EMI can interfere with the operation of other electrical components that are disposed in close proximity to the disk drive  300 . 
       FIG. 4  illustrates a disk drive device  300  that includes a multilayer tape  320  of the present invention disposed around the seam  318  of the disk drive device. When the conductive adhesive is a pressure sensitive adhesive, sufficient pressure should be applied to ensure an electrically conductive pathway is formed between the enclosure surface and the conductive material layer of the multilayer tape  320 . The multilayer tape  320  preferably covers the entire seam  318  to prevent EMI from leaking out of the enclosure. 
     The tape  320  also provides evidence of tampering, i.e., evidence that the cover  314  has been removed from the base plate  312 . Three interfaces exist after the multilayer tape is applied to an enclosure, namely the substrate-conductive material interface, the conductive material-adhesive interface, and the adhesive-enclosure interface. The multilayer tape of the present invention is designed so that the adhesive strength of the substrate-conductive material interface is the lowest. To open the device and access the internal components, the tape must first be removed from the seam. When a user attempts to remove the multilayer tape, the substrate is peeled away from the underlying conductive material layer, providing evidence of the tampering. The adhesive and conductive material layers remain intact and advantageously continue to provide EMI shielding. 
     While various embodiments of the present invention have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present invention.

Technology Classification (CPC): 6