PATENT DOCUMENT

Publication Number: US-9258906-B2
Application Number: US-201313863264-A
Country: US
Kind Code: B2

Title: Liquid-based pressure sensitive adhesive for grounding applications

Abstract:
An electronic device may be provided with electronic device structures such as housing structures, antenna structures, printed circuits, and structures associated with electrical components. The structures may be attached to each other using adhesive. A liquid pressure sensitive adhesive precursor material is deposited onto one or more surfaces of structures to be bonded. Light or heat can be applied to cure the liquid adhesive material and form pressure sensitive adhesive layers. During curing, chemical bonds are formed between the adhesive material and the structures. Assembly equipment may press the structures together to form pressure sensitive adhesive bonds that can be reworked without disturbing the chemically bonded portions of the adhesive material. The pressure sensitive adhesive may include conductive particles for forming conductive paths.

Claims:
What is claimed is: 
     
       1. A method for assembling structures in an electronic device, comprising:
 applying liquid pressure sensitive adhesive precursor material to a first structure in the electronic device; 
 curing the liquid pressure sensitive adhesive precursor material on the first structure to form a first pressure sensitive adhesive layer; 
 applying liquid pressure sensitive adhesive precursor material to a second structure in the electronic device; 
 curing the liquid pressure sensitive adhesive precursor material on the second structure to form a second pressure sensitive adhesive layer; and 
 pressing together the first and second pressure sensitive adhesive layers to attach the first and second structures. 
 
     
     
       2. The method defined in  claim 1  wherein the first and second pressure sensitive adhesive layers comprise conductive pressure sensitive adhesive. 
     
     
       3. The method defined in  claim 2  wherein the first structure comprises a metal electronic device housing and wherein curing the liquid pressure sensitive adhesive precursor comprises curing the liquid pressure sensitive adhesive precursor material on the metal electronic device housing. 
     
     
       4. The method defined in  claim 1  wherein the first structure includes first metal traces, wherein the second structure includes second metal traces, and wherein pressing together the first and second pressure sensitive adhesive layers comprises forming a conductive pressure sensitive adhesive joint that shorts the first metal traces to the second metal traces. 
     
     
       5. The method defined in  claim 1  wherein curing the liquid pressure sensitive adhesive precursor material comprises applying ultraviolet light to the liquid pressure sensitive adhesive precursor material. 
     
     
       6. The method defined in  claim 1  wherein curing the liquid pressure sensitive adhesive precursor material comprises heating the liquid pressure sensitive adhesive precursor material to a temperature that is elevated above room temperature by at least 40° C. 
     
     
       7. The method defined in  claim 1  wherein pressing together the first and second pressure sensitive adhesive layers forms a pressure-sensitive-adhesive-to-pressure-sensitive adhesive interface, the method further comprising pulling apart the first and second pressure sensitive adhesive layers along the pressure-sensitive-adhesive-to-pressure-sensitive adhesive interface without removing the first pressure sensitive adhesive layer from the first structure and without removing the second pressure sensitive adhesive layer from the second structure. 
     
     
       8. The method defined in  claim 1  wherein the first structure comprises a flexible printed circuit, wherein the second structure comprises a metal housing, wherein the first and second pressure sensitive adhesive layers comprise conductive pressure sensitive adhesive, and wherein pressing together the first and second pressure sensitive adhesive layers comprises forming a conductive pressure sensitive adhesive joint that shorts metal traces in the flexible printed circuit to the metal housing. 
     
     
       9. The method defined in  claim 1  wherein curing the liquid pressure sensitive adhesive precursor material on the first structure comprises forming chemical bonds between the first pressure sensitive adhesive layer and the first structure and wherein curing the liquid pressure sensitive adhesive precursor material on the second structure comprises forming chemical bonds between the second pressure sensitive adhesive layer and the second structure. 
     
     
       10. A method, comprising:
 depositing a conductive liquid pressure sensitive adhesive precursor material on a first conductive structure; 
 curing the deposited liquid pressure sensitive adhesive precursor material on the first conductive structure to form a conductive pressure sensitive adhesive layer that is chemically bonded to the first conductive structure; and 
 shorting a second conductive structure to the first conductive structure through the conductive pressure sensitive adhesive layer, wherein the second conductive structure comprises a ground structure and wherein shorting the second conductive structure to the first conductive structure comprises grounding the first conductive structure to the conductive ground structure through the conductive pressure sensitive adhesive layer. 
 
     
     
       11. The method defined in  claim 10  wherein shorting the second conductive structure comprises pressing a metal trace on a flexible printed circuit against the conductive pressure sensitive adhesive layer. 
     
     
       12. The method defined in  claim 11  wherein depositing the conductive liquid pressure sensitive adhesive comprises screen printing the conductive liquid pressure sensitive adhesive precursor material. 
     
     
       13. The method defined in  claim 12  wherein the flexible printed circuit includes an antenna formed from metal structures that are at least partly covered with the deposited liquid pressure sensitive adhesive material and wherein curing the deposited liquid pressure sensitive adhesive precursor material comprises applying light to the deposited liquid pressure sensitive adhesive precursor material on the metal structures. 
     
     
       14. The method defined in  claim 13  further comprising:
 depositing conductive liquid pressure sensitive adhesive precursor material on the second conductive structure; and 
 curing the deposited liquid pressure sensitive adhesive precursor material on the second conductive structure to form a conductive pressure sensitive adhesive layer that is chemically bonded to the second conductive structure, wherein shorting the second conductive structure to the first conductive structure comprises grounding the first conductive structure to the conductive ground structure through the conductive pressure sensitive adhesive layers on the first and second conductive structures.

Description:
BACKGROUND 
     This relates generally to adhesives and, more particularly, to pressure sensitive adhesives formed from liquid that can be used for coupling structures in electronic devices. 
     Adhesives are widely used to attach structures to each other. As an example, electronic devices such as computers and cellular telephones often contain adhesives for mounting components to housing structures, for attaching housing structures to each other, and for otherwise assembling structures within a completed device. 
     Liquid adhesives can be applied between parts to be joined. Heat or ultraviolet light can be applied to cure a liquid adhesive and form an adhesive joint between the parts. Liquid adhesive joints of this type can be difficult to control and may not be reworkable. 
     Pressure sensitive adhesives form bonds under pressure. The use of pressure sensitive adhesives is often preferred over liquid adhesives due to ease of assembly and, in some situations, an ability to rework assembled parts. Metal particles can be included in pressure sensitive adhesives to promote conduction. A conductive pressure sensitive adhesive may be used to form a ground path in an electronic device. 
     Pressure sensitive adhesive joints can be formed from pressure sensitive adhesive tape. Pressure sensitive adhesive tape includes a plastic carrier film that it typically die cut to form pressure sensitive adhesive areas in desired patterns. Assembly of parts using tape-based pressure sensitive adhesive tape can be cumbersome. Tape-based joints are also sometimes difficult to rework, because they tend to tear unpredictably and leave unwanted residues on disassembled parts. 
     It would therefore be desirable to be able to provide improved pressure sensitive adhesive joints for electronic devices. 
     SUMMARY 
     An electronic device may be provided with electronic device structures such as housing structures, antenna structures, printed circuits, and structures associated with electrical components. The structures may be attached to each other using adhesive. The adhesive may be pressure sensitive adhesive that is deposited in liquid form. 
     A liquid pressure sensitive adhesive precursor material can be deposited onto one or more surfaces of structures to be bonded using screen printing equipment or other liquid dispensing equipment. Light or heat can be applied to cure the liquid adhesive material and form pressure sensitive adhesive layers. During curing, chemical bonds can be formed between the adhesive material and the structures. The pressure sensitive adhesive layers that are formed in this way can be assembled manually or using automated equipment. 
     For example, assembly equipment may press structures together to form pressure sensitive adhesive bonds. In joints with multiple layers of pressure sensitive adhesive joined along an interface, rework is possible. The multiple layers can be pulled apart along the interface without removing the adhesive from the structures. Ferromagnetic material in the adhesive can provide shielding. The adhesive may also be provided with metal particles to form conductive pressure sensitive adhesive. Conductive pressure sensitive adhesive may be used to short together the structures that are being joined. 
     The use of liquid-based pressure sensitive adhesive in forming adhesive joints may help ensure good coverage of structures being bonded, may reduce dependency of bonds to bonding conditions such as pressure, temperature and time, and may help minimize the amount of pressure that is required to form joints. 
     Further features, their nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device of the type that may contain structures that are attached to each other with adhesive in accordance with an embodiment. 
         FIG. 2  is a side view of structures in an electronic device such as a flexible printed circuit and metal housing member that are being joined using adhesive in accordance with an embodiment. 
         FIG. 3  is a side view of structures in an electronic device such as a pair of printed circuits that are being joined using adhesive in accordance with an embodiment. 
         FIG. 4  is a diagram of equipment and operations involved in forming an adhesive joint between structures in an electronic device in accordance with an embodiment. 
         FIG. 5  is a diagram of equipment and operations that may be used to disassemble and repair an electronic device having an adhesive joint in accordance with an embodiment. 
         FIG. 6  is a diagram of equipment and operations involved in forming a pressure sensitive adhesive joint in which liquid adhesive for forming a layer of pressure sensitive adhesive is applied to one of a pair of surfaces to be joined in accordance with an embodiment. 
         FIG. 7  is a diagram of equipment and operations involved in curing liquid adhesive material to form pressure sensitive adhesive layers on structures to be joined in accordance with an embodiment. 
         FIG. 8  is a diagram of equipment and operations involved in using conductive pressure sensitive adhesive bonds to form electrical connections between conductive structures such as metal traces on dielectric carriers in accordance with an embodiment. 
         FIG. 9  is a diagram of equipment and operations involved in forming a ferrous electromagnetic shielding layer in an electronic device from a layer of liquid material in accordance with an embodiment. 
         FIG. 10  is a flow chart of illustrative steps involved in forming adhesive joints using pressure sensitive adhesive that is applied to the structures to be joined in liquid form in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Adhesive may be used to join structures formed from metal, ceramics, glass, plastic, and other conductors and dielectric materials. An illustrative device of the type that may include structures joined using adhesive is shown in  FIG. 1 . Electronic device  10  may be a computer such as a computer that is integrated into a display such as a computer monitor, a laptop computer, a tablet computer, a somewhat smaller portable device such as a wrist-watch device, pendant device, or other wearable or miniature device, a handheld device such as a cellular telephone, a media player, a tablet computer, a gaming device, a navigation device, a computer monitor, a television, or other electronic equipment. 
     As shown in  FIG. 1 , device  10  may include a display such as display  14 . Display  14  may be a touch screen that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components or may be a display that is not touch-sensitive. Display  14  may include an array of display pixels formed from liquid crystal display (LCD) components, an array of electrophoretic display pixels, an array of plasma display pixels, an array of organic light-emitting diode display pixels, an array of electrowetting display pixels, or display pixels based on other display technologies. 
     Display  14  may be protected using a display cover layer such as a layer of transparent glass or clear plastic. Openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button such as button  16 . An opening may also be formed in the display cover layer to accommodate ports such as speaker port  18 . 
     Device  10  may have a housing such as housing  12 . Housing  12 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. 
     Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). The periphery of housing  12  may, if desired, include walls. For example, housing  12  may have a peripheral conductive member such as a metal housing sidewall member that runs around some or all of the periphery of device  10  or may have a display bezel that surrounds display  14 . Housing  12  may have sidewalls that are curved, sidewalls that are planar, sidewalls that have a combination of curved and flat sections, and sidewalls of other suitable shapes. One or more openings may be formed in housing  12  to accommodate connector ports, buttons, and other components. 
     It may be desirable to join internal housing structures, electrical components in device  10 , housing  12 , mechanical structures in device  10 , and other structures in device  10  using adhesive. The adhesive that is used in joining the structures of device  10  or that is used in joining other structures may be formed from a liquid adhesive (sometimes referred to as liquid pressure sensitive adhesive precursor material) that is applied to one or more surfaces of the structures to be joined. Using thermal or ultraviolet light curing, the applied liquid adhesive may be cured to form one or more layers of pressure sensitive adhesive. As part of the curing process, the pressure sensitive adhesive forms chemical bonds with the surface to which the liquid adhesive was applied. Following formation of one or more layers of pressure sensitive adhesive in this way, the structures that are to be joined may be pressed together. The pressing process compresses the pressure sensitive adhesive and forms a pressure sensitive adhesive joint. The pressure sensitive adhesive joint may be pulled apart to rework or repair the structures being joined, generally without breaking the chemical bonds at the interface between the pressure sensitive adhesive and the structures on which the pressure sensitive adhesive was cured. 
     Consider, as an example, the cross-sectional side view of  FIG. 2 . In the example of  FIG. 2 , an adhesive joint formed from pressure sensitive adhesive  24  is being used to join structures in device  10  such as structures  20  and  22 . Structures  20  and  22  may be portions of housing  12 , brackets and other internal housing structures, display structures, cables, flexible printed circuits, rigid printed circuits, optical components, electrical components, conductive structures, or other electronic device structures. As an example, structure  20  may be a metal member such as a metal housing member or other conductive structure that serves as an electrical ground and structure  22  may be a printed circuit such as a flexible printed circuit. Flexible printed circuit  22  may contain patterned metal traces such as metal traces  28  for forming signal lines that convey signals or for forming structures such as antenna structures. One or more layers of dielectric substrate material such as polyimide or other polymers may be used in forming flexible printed circuit  22 . Surface contacts such as metal trace  26  may be used to form electrical contact with adhesive  24 . Metal trace  26  may, as an example, form a rectangular contact pad on the lower surface of flexible printed circuit  22  that is facing the opposing upper surface of metal housing structure  20 . 
     Examples of metals that may be used in forming some or all of the traces for flexible printed circuit  22  include copper, gold, and aluminum. Metal housing  20  may be formed from stainless steel or aluminum (as examples). Pressure sensitive adhesive  24  may be nonconductive or may, if desired, contain conductive materials such as metal particles  30 . In configurations for pressure sensitive adhesive  24  in which pressure sensitive adhesive  24  has been provided with metal particles, pressure sensitive adhesive  24  may be conductive. Conductive pressure sensitive adhesive  24  may be used to form electrical pathways between the structures that are being joined. For example, conductive pressure sensitive adhesive  24  may be used to electrically couple pad  26  and trace  28  of flexible printed circuit  22  to metal housing  20  or may be used to short together and ground other conductive structures. To ensure satisfactory electrical contact between flexible printed circuit  22  and housing  20 , portion  32  of metal housing member  20  may be laser etched or otherwise treated to remove any oxides that are present in other areas on the surface of metal housing  20 . 
     Pressure sensitive adhesive  24  may be deposited as a liquid (e.g., conductive liquid pressure sensitive adhesive precursor) and cured on the surfaces of respective structures such as structures  20  and  22 . For example, a screen printing process or other liquid deposition process may be used to form layer  24 B in a particular area on surface  34  of housing structure  20 . A screen printing process may also be used to form layer  24 A in a particular area on surface  38  of flexible printed circuit  22 . For example, liquid for layer  24 A may be deposited in a pattern having a footprint that overlaps and covers contact pad  26 . 
     After depositing liquid pressure sensitive adhesive precursor material in desired patterns on surfaces  34  and  38 , the liquid material may be cured. For example, an elevated temperature (e.g., a temperature that is 30° C. or more, 40° C. or more, 50° C. or more or 60° C. or more above room temperature) may be applied to the liquid to drive off any solvents in the liquid. As another example, ultraviolet light from an ultraviolet light source such as an ultraviolet lamp or ultraviolet laser may be used to cure the liquid pressure sensitive adhesive precursor material. Visible light curing may also be used. Following curing, there will be two pressure sensitive adhesive layers—one on surface  34  of metal housing  20  and one on surface  38  of flexible printed circuit  22 . During curing, chemical bonds may form between the adhesive material and structures  20  and  22 . For example, chemical bonds  36  may form between the lower surface of pressure sensitive adhesive layer  24 B and surface  34  of metal housing member  20 . Chemical bonds  40  may form between surface  38  of flexible printed circuit  22  (i.e., the surface of metal pad  26 ) and the upper surface of pressure sensitive adhesive layer  24 A. 
     To form adhesive layer  24  after the liquid pressure sensitive adhesive precursor material has been cured to form pressure sensitive adhesive layers  24 A and  24 B, structures  22  and  20  may be pressed together. This causes layer  24 A to press against layer  24 B along interface  42 , thereby forming a pressure-sensitive-adhesive-to-pressure-sensitive-adhesive joint (joint  42 ). When it is desired to pull apart the joint that is formed between pressure sensitive adhesive layers  24 A and  24 B, flexible printed circuit  22  can be pulled away from housing structure  20 . Chemical bonds  36  and  40  will be stronger than pressure-sensitive-adhesive-to-pressure-sensitive-adhesive bond  42 , so adhesive  24  will tend to pull apart along the interface of bond  42 , leaving adhesive layer  24 B on surface (and leaving adhesive layer  24 A on flexible printed circuit  22 ). If desired, a component such as flexible printed circuit  22  can be replaced with a fresh component to repair faulty structures on flexible printed circuit  22 . Traces  28  may form antenna resonating element structures (e.g., inverted-F antenna resonating element structures or other antennas), may form a communications bus (e.g., a communications path with parallel metal lines for carrying serial and/or parallel data, may form a printed circuit that is populated with integrated circuits and other components, or may form other structures for device  10 . 
     In the illustrative configuration of  FIG. 3 , two flexible printed circuits have been joined using pressure sensitive adhesive  24 . As shown in  FIG. 3 , pressure sensitive adhesive  24  includes a first layer such as upper layer  24 A that is formed on the surface of metal pad  26  on flexible printed circuit  22 . Metal pad (metal trace)  26  may be coupled to other metal structures in printed circuit  22  such as metal traces  28 . Pressure sensitive adhesive  24  also includes a second layer such as lower layer  24 B that is formed on the surface of metal pad  26 ′, which is coupled to metal traces  28 ′ in flexible printed circuit  22 ′. 
       FIG. 4  is a diagram of illustrative equipment and steps involved in forming a pressure sensitive adhesive bond between respective structures using pressure sensitive adhesive  24 . As shown in  FIG. 4 , structures to be bonded together such as structures  20  and  22  may be coated with liquid pressure sensitive adhesive precursor layers using liquid dispensing and curing equipment  44 . Equipment  44  may then cure the deposited liquid layers to form pressure sensitive adhesive layers  24 A and  24 B. Liquid dispensing equipment in equipment  44  may include screen printing equipment, pad printing equipment, spraying equipment, jet printing equipment, slit dispenser equipment, needle dispenser equipment, rollers, and other equipment for dispensing liquid. The liquid adhesive that is dispensed may contain metal particles  30  ( FIGS. 2 and 3 ) so that pressure sensitive adhesive layers  24 A and  24 B are conductive. Metal particles  30  may be, for example, silver particles. Adhesive layers  24 A and  24 B may be silver-filled acrylic polyurethane or polyether with silane-terminated ends (as one example). 
     Curing equipment in equipment  44  may include an oven for supplying heat to elevate the temperature of adhesive  24 . For example, equipment  44  may contain a hot plate or other structure for heating the liquid of adhesive  24 , thereby evaporating solvents in the liquid and forming cured pressure sensitive adhesive layers. As another example, equipment  44  may contain an ultraviolet (UV) light lamp, an ultraviolet laser, or other source of ultraviolet light for UV curing the liquid adhesive material to form pressure sensitive adhesive  24 . Following curing of the liquid material, pressure sensitive adhesive layer  24 A may be formed on structure  22  (e.g., a flexible printed circuit or other structure such as a conductive structure) and pressure sensitive adhesive layer  24 B may be formed on structure  20  (e.g., a metal housing structure or other structure such as a conductive structure). 
     Assembly equipment  46  may contain manually operated and computer-controlled equipment for pressing together structures  20  and  22 . For example, assembly equipment  46  may include computer-controlled positioner  48 . During assembly operations, assembly personnel may manually join structures  22  and  20  or computer-controlled positioner  48  may be used in joining structures  22  and  20  by pressing together structures  22  (and adhesive  24 A) and structures  20  (and adhesive  24 B), thereby forming pressure-sensitive-adhesive-to-pressure-sensitive-adhesive interface  42  in adhesive  24 . 
     Disassembly equipment and operations of the type that may be used in connection with the adhesive bond formed using liquid dispensed pressure sensitive adhesive are shown in  FIG. 5 . As shown in  FIG. 5 , structures  20  and  22  may be bonded using pressure sensitive adhesive  24  (e.g., using techniques of the type shown in  FIG. 4 ). Disassembly equipment  50  may include computer-controlled positioners such as computer-controlled positioner  48 ′. When it is desired to disassemble structures  20  and  22  to replace a faulty structure such as structure  22 , positioner  48 ′ may be used to pull apart flexible printed circuit structure  22  and housing structure  20 , as illustrated by arrow  52 . Because the bond along interface  42  between the two joined pressure sensitive adhesive layers is weaker than the respective bonds formed by the chemical bonds between adhesive  24  and structures  20  and  22 , adhesive  24  will tend to tear apart smoothly along interface  24 . As a result, adhesive such as cured pressure sensitive adhesive  24 B will generally be undamaged and may be used to form part of a new pressure sensitive adhesive joint. 
     As an example, assembly equipment  46  may use computer-controlled positioner  48  to attach replacement flexible printed circuit  22 R to structures  20 . Replacement flexible printed circuit  22 R may have a substrate on which adhesive layer  24 A′ has been formed (e.g., using liquid adhesive dispensing such as screen printing followed by curing). Adhesive joint  24  of  FIG. 5  may be formed by pressing substrate  22 R against metal housing  20 . 
     In the illustrative configuration of  FIG. 6 , pressure sensitive adhesive  24  has been formed on only a single one of surfaces of the structures being joined. Initially, structures  20  and  22  are free of adhesive. Liquid dispensing and curing equipment  44  applies liquid pressure sensitive adhesive material to structure  20  (or to structure  22 ) and cures the applied material to form pressure sensitive adhesive layer  24 B. Assembly equipment  46  may then be used to press structures  22  and structures  20  together, thereby forming an adhesive bond between structures  22  and  20  using adhesive  24 B. In this example, the lower surface of adhesive  24 B forms chemical bonds with structures  20  and the upper surface of adhesive  24 B forms pressure-sensitive adhesive bonds with structures  22 . In the event of disassembly for rework or repair (see, e.g.,  FIG. 5 ), the upper bond formed by pressure sensitive adhesive  24 B will break before the lower bond formed by adhesive  24 B. 
       FIG. 7  is a diagram showing how liquid material (e.g., a liquid polymer such as a liquid pressure sensitive adhesive polymer precursor) may be dispensed and cured. Initially, structure  20  may be free of adhesive. Liquid pressure sensor adhesive material  60  may be dispensed onto the surface of structure  20  to form adhesive layer  24 BU. Liquid dispensing equipment  44 A (e.g., dispensing equipment in equipment  44 ) may include equipment for screen printing patterns of liquid adhesive onto structures to be joined, may include pad printing equipment, may include jet printing equipment slit dispensing equipment, needle dispensing equipment, etc.). Curing equipment  44 B (e.g., curing equipment in equipment  44 ) may use an ultraviolet light source such as light source  44 B- 1  to apply ultraviolet light  62  or other curing light to the adhesive to patterned liquid adhesive  24 BU, thereby curing the liquid adhesive and forming cured pressure sensitive adhesive layer  24 B on structures  20 . If desired, curing equipment  44 B- 2  such as an oven, hot plate, heat gun, heating lamp, or other heating equipment may be used to elevate the temperature of layer  24 BU, thereby curing layer  24 BU and forming pressure sensitive adhesive layer  24 B on structures  20 . 
     Conductive pressure sensitive adhesive structures may, if desired, be used in forming electrical connections between respective signal lines such as metal traces on opposing printed circuits. As shown in  FIG. 8 , a substrate such as printed circuit  22  (e.g., a flexible printed circuit or a rigid printed circuit board) may be provided with signal lines such as metal traces  66  using fabrication equipment  68  (e.g., photolithographic patterning equipment, equipment for depositing metal, etc.). Equipment  68  may include equipment such as liquid dispensing and curing equipment  44  for dispensing liquid pressure sensitive adhesive precursor material and curing the liquid material to form pads of pressure sensitive adhesive  24 A such as pads  24 B- 1 ,  24 B- 2 , and  24 B- 3 . Equipment  68  may also fabricate board  22 ′ and pads of pressure sensitive adhesive  24 B on board  22 ′. Assembly equipment  46  may press printed circuits  22  and  22 ′ together to form a plurality of respective pressure sensitive adhesive joints formed from respective areas of pressure sensitive adhesive  24  (e.g., respective joined pads from upper and lower printed circuits). In this way, each signal line  66  on printed circuit  22  may be electrically shorted to a respective signal line on printed circuit  22 ′ using a respective pressure sensitive adhesive joint. 
     During manufacturing, faults may be revealed in structures such as printed circuit  22 . For example, if printed circuit  22  contains metal traces that form an antenna, antenna performance tests may reveal that an antenna resonating element is not performing satisfactorily. Rather than scrap device  10 , disassembly equipment  50  may be used to pull apart printed circuits  22  and  22 ′, as indicated by arrow  52  of  FIG. 8 . Because pressure sensitive adhesive  24  is configured to pull apart along the pressure sensitive adhesive interface  42 , the pressure sensitive adhesive layers will not be damaged as part of the disassembly process, allowing repair. Following disassembly, assembly equipment  46  may be used to reattach a replacement antenna (i.e., a replacement flexible printed circuit) using pressure sensitive adhesive  24 . 
     If desired, adhesive  24  may incorporate ferrous particles (e.g., iron particles). This allows pressure sensitive adhesive layer  24  to serve as a ferrous electromagnetic shielding layer. Equipment and operations involved in forming a shielding layer using liquid ferrous adhesive precursor material are shown in  FIG. 9 . Initially, structures such as structures  20  are processed to form metal traces  28  using fabrication equipment  68 . Equipment  68  may include tools for depositing metal and for photolithographically patterning the deposited metal to form patterned traces  28 . 
     Traces  28  may be, for example, antenna traces. Structures  22  may be printed circuit structures. The antenna traces may be formed on the surface of printed circuit  22  and/or may be embedded within the layers of polyimide or other dielectric making up printed circuit  22 . Liquid ferrous pressure sensitive adhesive precursor material  69  may be applied to a structure such as housing  12  using liquid dispensing and curing equipment and assembly equipment  70  (e.g., liquid dispensing and curing equipment  44  and assembly equipment  46 ), thereby forming cured pressure sensitive adhesive layer  241 . Printed circuit  22  may be attached to housing  12  (or other electronic device structures) using adhesive layer  241 . Metal traces  28  may be metal antenna traces coupled to radio-frequency transceiver circuitry  72  by transmission line  74 . During operation, antenna traces  28  may generate wireless signals. Ferrous particles  30 ′ in pressure sensitive adhesive layer  241  allow layer  241  to serve as electromagnetic shielding for the antenna formed from traces  28 . 
     The layout of  FIG. 9  is merely illustrative. Ferrous shielding layer  241  may be formed at other locations within device  10  and may be used in providing electromagnetic shielding for other types of components, if desired. 
     Illustrative steps involved in forming electronic devices with liquid-based pressure sensitive adhesive are shown in  FIG. 10 . At step  80 , equipment such as equipment  44  may be used to deposit conductive liquid pressure sensitive adhesive precursor material on the surface(s) of structures to be joined. For example, screen printing or other deposition and patterning techniques may be used to form patterned liquid adhesive material. 
     At step  82 , light or heat for curing the deposited liquid adhesive precursor material may be applied to the liquid material. During curing, chemical bonds are formed between the adhesive and the structures on which the adhesive has been deposited. 
     During the operations of step  84 , the structures that are to be attached to each other are pressed together to form a pressure sensitive adhesive bond. 
     If desired, the bonded structures can be pulled apart (step  86 ). Pressure sensitive adhesive bonding (e.g., the pressure-sensitive-adhesive-to-pressure-sensitive adhesive interface in a system with mating pressure sensitive adhesive layers or the pressure sensitive adhesive bond formed when pressing the pressure sensitive adhesive against a structure to be bonded) is generally less robust than chemical bonding, so the pressure sensitive adhesive will typically come apart along the pressure-sensitive-adhesive-to-pressure-sensitive-adhesive interface or other location without chemical bonds. Because this does not generally damage the underlying pressure sensitive adhesive layers on the structures, the structures can be reworked or repaired, as indicated schematically by line  88 . 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20130415
Publication Date: 20160209
Grant Date: 20160209
Priority Date: 20130415
Inventors: KROGDAHL JAMES R.
POPE BENJAMIN J.
PYPER DENNIS R.
MERZ NICHOLAS G. L.
MYERS SCOTT A.
Assignee: APPLE INC
CPC Classifications: [{"code": "C09J5/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "C09J2203/326", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/323", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K3/386", "inventive": true, "first": true, "tree": "[]"}, {"code": "C09J2201/606", "inventive": false, "first": false, "tree": "[]"}, {"code": "C09J2205/31", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/361", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/31678", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T156/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "C09J5/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "C09J2301/416", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/361", "inventive": true, "first": false, "tree": "[]"}, {"code": "C09J2301/416", "inventive": false, "first": false, "tree": "[]"}, {"code": "C09J2203/326", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "C09J2301/302", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/323", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/31678", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/31678", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T156/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/361", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T156/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "C09J2301/302", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/323", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K3/386", "inventive": true, "first": true, "tree": "[]"}, {"code": "C09J2203/326", "inventive": false, "first": false, "tree": "[]"}, {"code": "C09J5/00", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 51686985