PATENT DOCUMENT

Publication Number: US-9456508-B2
Application Number: US-79073210-A
Country: US
Kind Code: B2

Title: Methods for assembling electronic devices by internally curing light-sensitive adhesive

Abstract:
Assemblies of structures such as electronic device assemblies may be connected using light-cured liquid adhesive such as ultraviolet-light-cured adhesive. Light sources such as ultraviolet-light light-emitting diodes may be mounted to a substrate such as a printed circuit board substrate. The substrate may be mounted to an assembly formed from a plurality of structures. The structures may be connected to each other to form an interior cavity within which the substrate and light-emitting diodes are contained. A connector may be included in the assembly. The connector may have input-output pins. Conductive paths may couple the input-output pins to the light-emitting diodes in the cavity. A tool may be used to apply signals to the light-emitting diodes to activate the light-emitting diodes. The light-emitting diodes produce light that cures the adhesive. The light-emitting diodes may be disabled by blowing a fuse after the adhesive has been cured.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a first housing structure; 
 electronic components within the first housing structure including an ultraviolet light-emitting diode; 
 a second housing structure that is connected to the first housing structure and that forms an interior cavity within the electronic device in which the ultraviolet light-emitting diode is located; and 
 ultraviolet-light-cured epoxy that is contained within the interior cavity and that attaches the first and second housing structures. 
 
     
     
       2. The electronic device defined in  claim 1  further comprising a connector having input-output pins and conductive lines that couple at least some of the input-output pins to the ultraviolet light-emitting diode. 
     
     
       3. The electronic device defined in  claim 2  further comprising a fuse interposed in at least one of the conductive lines. 
     
     
       4. The electronic device defined in  claim 1 , wherein the interior cavity is an enclosed interior cavity, and wherein the ultraviolet-light-cured epoxy is completely contained within the enclosed interior cavity. 
     
     
       5. The electronic device defined in  claim 1 , wherein the ultraviolet light-emitting diode is not in direct contact with the ultraviolet-light-cured epoxy. 
     
     
       6. An electronic device, comprising:
 a first component; 
 a second component; 
 a substrate; 
 light-cured adhesive interposed between the first and second components, wherein the light-cured adhesive is in contact with the first and second components; and 
 a plurality of light sources on the substrate, wherein the light-cured adhesive has been cured using the plurality of light sources on the substrate, wherein the first and second components and the substrate remain a part of the electronic device after the light-cured adhesive has been cured. 
 
     
     
       7. The electronic device defined in  claim 6 , wherein the substrate comprises a printed circuit board. 
     
     
       8. The electronic device defined in  claim 7 , further comprising:
 a connector; and 
 a conductive path on the substrate interposed between the connector and the plurality of light sources on the substrate. 
 
     
     
       9. The electronic device defined in  claim 8 , further comprising at least one current control component on the conductive path. 
     
     
       10. The electronic device defined in  claim 9 , wherein the at least one current control component comprises a fuse. 
     
     
       11. The electronic device defined in  claim 10 , wherein the fuse comprises a blown fuse. 
     
     
       12. The electronic device defined in  claim 11 , wherein the connector comprises at least one input-output pin coupled to the conductive path and wherein the blown fuse is located on the conductive path between the input-output pin and the plurality of light sources. 
     
     
       13. The electronic device defined in  claim 7 , further comprising at least one integrated circuit on the printed circuit board. 
     
     
       14. The electronic device defined in  claim 7 , wherein the plurality of light sources comprises a plurality of light-emitting-diodes. 
     
     
       15. The electronic device defined in  claim 7 , wherein the printed circuit board has first and second opposing surfaces and wherein the plurality of light sources comprises a first plurality of light sources attached to the first surface and a second plurality of light sources attached to the second surface. 
     
     
       16. The electronic device defined in  claim 7 , wherein the first component comprises a portion of a housing and wherein the portion of the housing includes an opaque portion and a transparent portion. 
     
     
       17. The electronic device defined in  claim 16 , wherein at least one of the plurality of light sources is mounted to the printed circuit board adjacent to the transparent portion of the portion of the housing. 
     
     
       18. The electronic device defined in  claim 17 , wherein the light-cured adhesive is formed in contact with the transparent portion of the portion of the housing. 
     
     
       19. The electronic device defined in  claim 6 , wherein at least one of the first and second components comprises a transparent structure configured to transmit light emitted by at least one of the plurality of light sources to the light-cured adhesive. 
     
     
       20. An electronic device, comprising:
 a first housing structure; 
 electronic components within the first housing structure including an ultraviolet light-emitting diode; 
 a second housing structure that is connected to the first housing structure and that forms an interior cavity within the electronic device in which the ultraviolet light-emitting diode is located; 
 ultraviolet-light-cured epoxy that is contained within the interior cavity and that attaches the first and second housing structures; and 
 a light pipe that guides light emitted by the ultraviolet light-emitting diode to the ultraviolet-light-cured epoxy.

Description:
BACKGROUND 
     This relates generally to manufacturing techniques, and more particularly, to methods for forming assemblies using adhesive. 
     Adhesives are widely used in manufacturing. For example, electronic devices often include housings and structures that are attached to each other with pressure sensitive adhesive. In some situations it is difficult to use pressure sensitive adhesive to attach structures to each other. For example, if two parts must slide past each other during assembly, it may be necessary to attach the parts to each other using liquid adhesive rather than a layer of pressure sensitive adhesive. The liquid adhesive can flow during the assembly process and will not cause the two parts to bind to each other prematurely, whereas a layer of pressure sensitive adhesive might cause the two parts to become stuck before they have reached their proper positions. 
     A variety of liquid adhesives are available. Some glues cure chemically. For example, two-part epoxies and methyl methacrylate (MMA) adhesives cure upon mixing resin with hardener. Cyanoacrylate (CA) adhesive is activated by exposure to moisture. Other glues are cured by application of elevated temperatures. Curing mechanisms such as these often produce undesirable outgassing and can be difficult to control. 
     Satisfactory control and minimal outgassing can be achieved by using adhesives that are cured by application of ultraviolet (UV) light. For example, ultraviolet-light-cured (UV) epoxy can be used to attach metal and plastic parts in an electronic device. In a typical manufacturing process, uncured UV epoxy is applied to structures that are to be attached to each other. Once the structures are in their desired positions, UV light from a UV lamp is applied to the UV epoxy. This cures the UV epoxy. 
     In some product designs, it is awkward or impossible to expose the UV epoxy using a UV lamp. For example, if the UV epoxy is located in an interior portion of an assembly, the walls of the assembly will block light from the UV lamp. 
     To allow UV epoxy to be used to assemble parts where the UV epoxy is located in the interior of the assembly, holes are formed in the parts. During manufacturing, a technician can insert a UV light wand into the interior portion of the assembly through the holes. The internal application of UV light using a UV wand requires the use of holes in the assembly that are large enough to accommodate the UV wand. The holes may be unsightly and may reduce the ability of the assembly to withstand environmental exposure to dust and moisture. 
     It would therefore be desirable to be able to provide improved techniques for assembling structures using light-sensitive adhesives. 
     SUMMARY 
     Assemblies of structures such as electronic device assemblies may be formed using light-cured liquid adhesive such as ultraviolet-light-cured adhesive. Light sources that are part of the assemblies may produce light for curing the light-cured adhesive. 
     The light sources that are used in curing the adhesive may be ultraviolet-light light-emitting diodes that are mounted to a substrate. The substrate may be mounted to an assembly formed from a number of structures. The structures that are used to form the assembly may be housing structures, internal device members, subassemblies, or other structures. 
     The structures may be connected to each other to form an assembly having an interior cavity within which the substrate and light-emitting diodes are mounted. The light-emitting diodes may also be connected to other portions of an assembly. 
     A connector may be included in the assembly. The connector may have input-output pins. Conductive paths may couple the input-output pins to the light-emitting diodes in the cavity. 
     A tool may be used to apply signals to the light-emitting diodes to activate the light-emitting diodes through the connector. The light-emitting diodes may produce light that cures the adhesive inside the cavity. After the adhesive has been cured, the light-emitting diodes may be disabled by blowing a fuse in the assembly. 
     Further features of the invention, its 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. 1A  is an exploded cross-sectional side view of an illustrative assembly having internal components that include a light source for curing adhesive in accordance with an embodiment of the present invention. 
         FIG. 1B  is a cross-sectional side view of an illustrative assembly of the type shown in  FIG. 1A  showing how a tool may be connected to the assembly and showing how a light source within the assembly may produce light internally that cures adhesive within the assembly in accordance with an embodiment of the present invention. 
         FIG. 2  is a cross-sectional side view of a tool connected to an assembly showing how the tool may deliver signals to a light source within the assembly through a connector to which the tool is engaged to produce light that cures adhesive within the assembly in accordance with an embodiment of the present invention. 
         FIG. 3  is a cross-sectional end view of an assembly showing how multiple light sources mounted on a substrate such as a printed circuit board may deliver light to cure adhesive within the interior of the assembly in accordance with an embodiment of the present invention. 
         FIG. 4  is a diagram showing how signals can be delivered to a light source on a substrate such as a printed circuit board using input-output pins coupled to the printed circuit board in accordance with an embodiment of the present invention. 
         FIG. 5  is a diagram showing how a light source on a printed circuit board can be controlled by delivering signals to the light source through control circuitry on the printed circuit board in accordance with an embodiment of the present invention. 
         FIG. 6  is a cross-sectional side view of a portion of a structure that may be formed from an opaque first shot of plastic in accordance with an embodiment of the present invention. 
         FIG. 7  is a cross-sectional side view of the structure of  FIG. 6  after a second shot of plastic such as a shot of transparent plastic has been added to the structure in accordance with an embodiment of the present invention. 
         FIG. 8  is a cross-sectional side view of a portion of an assembly that has an internal light source that delivers light through a transparent structure such as a light guiding structure formed from the second shot of plastic of  FIG. 7  in accordance with an embodiment of the present invention. 
         FIG. 9  is a cross-sectional side view of a portion of an assembly that includes an internal light source and a transparent member that delivers light from the light source to cure adhesive within the assembly in accordance with an embodiment of the present invention. 
         FIG. 10  is a cross-sectional side view of an illustrative assembly that includes an internal light source and a transparent member though which light from a light source reaches a layer of adhesive to attach structures together within the assembly in accordance with an embodiment of the present invention. 
         FIG. 11  is an exploded view of parts of an illustrative electronic device containing a printed circuit board on which light sources have been mounted to internally cure adhesive when assembling the parts in accordance with an embodiment of the present invention. 
         FIG. 12  is an exploded perspective view of an illustrative electronic device of the type shown in  FIG. 11  showing an end cap housing structure that may be attached to the electronic device using adhesive that is internally cured by a light source on an internal substrate such as a printed circuit board in accordance with an embodiment of the present invention. 
         FIG. 13  is a perspective view of an electronic device of the type shown in  FIG. 12  after the end cap has been attached to the electronic device using adhesive cured with an internal light source in accordance with an embodiment of the present invention. 
         FIG. 14  is a flow chart of illustrative steps involved in using adhesive that is cured from internal light sources to assemble structures in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Adhesive is widely used in connecting structures together. For example, electronic devices such as computers, cellular telephones, media players, and other electronic equipment often contains parts that are connected to each other using layers of liquid adhesive. Liquid adhesive allows parts to be moved relative to each other as part of the assembly process. For example, parts may slide with respect to each other before the adhesive has cured. Once the adhesive has cured, the parts become secured to one another and can be used in a finished product. 
     Adhesives can be activated chemically, thermally, or using light. For example, chemically activated two-part adhesives are available that have a hardener and a resin. When the hardener is mixed with the resin, a chemical reaction is created that cures the adhesive. Thermal curing typically involves raising an adhesive above room temperature. This type of curing process often produces undesirable outgassing and can be difficult to control. 
     As a result, adhesives are sometimes used that are cured by application of light. In a typical arrangement, ultraviolet (UV) light is applied to a UV-cured adhesive such as UV epoxy. It can be difficult or impossible to use this approach when the UV epoxy is located on the inside of an assembly. UV light wands can sometimes be inserted through holes in an assembly to reach the interior of the assembly. This allows UV light to be applied to UV adhesive within the assembly, but requires that holes be formed. The presence of the holes in parts of a device can adversely affect device aesthetics and structural integrity. 
     To overcome these shortcomings of conventional adhesive curing techniques, an assembly may be provided with an internal light source. Liquid adhesive may be applied to the structures that make up the assembly. When the liquid adhesive and the structures that make up the assembly are in proper position, the internal light source may be turned on to produce light. The light can cure the adhesive from within the assembly. This obviates the need to from holes in the assembly to accommodate an external light source such as a UV wand. Once the adhesive has been cured, the light source can be deactivated. If desired, a fuse may be blown or a device may otherwise be altered to prevent subsequent activation of the light source. 
     An illustrative assembly of the type that may be provided with an internal adhesive-curing light source is shown in  FIG. 1A . As shown in the exploded view of illustrative assembly  10  of  FIG. 1A , assembly  10  may contain multiple structures such as structures  12 A and  12 B and components  14 . 
     In general, any suitable number of structures may be assembled together using adhesive (e.g., two structures, more than two structures, three structures, more than three structures, four structures, more than four structures, etc.). The structures can be attached together to form a completed device (e.g., a product that is sold to an end user) or may be used to form a part of a device (e.g., a structure to which additional components are added before the structure is complete and ready to be sold to a user). Structures that are attached together with adhesive are sometimes referred to herein as parts, members, structures, pieces, components, housings, etc. The resulting assemblage of parts may sometimes be referred to as an assembly, a device, a product, an electronic device (e.g., a completed assembly), a structure, etc. 
     The structures from which assembly  10  is formed may include a light source (shown as part of components  14  in  FIG. 1A ). During manufacturing, adhesive may be applied to the structures of assembly  10 . The light source in components  14  may then be activated to cure the adhesive. After curing, the light source may remain as part of the assembly. 
     In the  FIG. 1A  example, structures  12 A and  12 B are structures that, when assembled, form an enclosure that surrounds internal components  14 . Structures  12 A and  12 B may, for example, be housing structures or other structures that have sidewalls. When structures  12 A and  12 B are attached to each other, the sidewalls of structures  12 A and  12 B may form a substantially enclosed internal cavity. Light source  14  may be located within the internal cavity and may remain within the internal cavity after the adhesive has been cured. The shapes and sizes of structures  12 A and  12 B are merely illustrative. In general, the structures from which assembly  10  is formed may have any suitable configuration. 
     If desired, the light source may be located on an external portion of an assembly or may be used in curing adhesive in an assembly that does not contain a fully enclosed cavity. Because internally located light sources can be particularly helpful in curing light-cured adhesive in internal cavities (because other arrangements may be impossible to use), illustrative arrangements in which adhesive-curing light sources  14  are located in internal locations are sometimes described herein as an example. This is, however, merely illustrative. Light source  14  may be mounted on an interior or an exterior surface of an assembly and the assembly in which light source  14  is included may or may not have an internal cavity. 
     Illustrative assembly  10  of  FIG. 1A  is in an unassembled state because structures  12 A and  12 B have not been attached to each other.  FIG. 1B  shows assembly  10  of  FIG. 1A  in an assembled state in which structure  12 A has been mounted within structure  12 B. In the  FIG. 1B  example, the sidewalls of structures  12 A and  12 B have formed enclosed cavity  24  within which components and light source  14  have been mounted. Adhesive  20  may be placed in contact with both of structures  12 A and  12 B (e.g., along a seam between structures  12 A and  12 B, within a gap between opposing planar surfaces of structures  12 A and  12 B, etc.). Adhesive  20  may, for example, be placed on one or both of structures  12 A and  12 B when structures  12 A and  12 B are in an unassembled state (as shown in  FIG. 1A ). Because uncured adhesive  20  is in liquid form, structures  12 A and  12 B may be assembled to form the structure shown in  FIG. 1B  by sliding structure  12 A into structure  12 B. 
     As shown in  FIG. 1B , tool  16  may supply signals to components and light source  14  over path  18 . For example, tool  16  may provide signals to a light source that cause the light source to generate light  22 . Light  22  may be directed towards adhesive  20  to cure adhesive  20 . Power for turning on light  22  may be supplied internally (e.g., using a battery in cavity  24  or elsewhere in assembly  10 ) or may be supplied externally from tool  16 . 
     Adhesive  20  may be a light-cured adhesive such as ultraviolet (UV) epoxy or other UV adhesive (sometimes referred to as ultraviolet-light-cured liquid adhesive, ultraviolet-light liquid adhesive, or ultraviolet liquid adhesive). UV epoxy and other UV adhesives are liquid until exposed to UV light. The light source in components and light source  14  may be based on one or more light-emitting diodes (LEDs). For example, the light source may include one or more UV LEDs. Light-emitting diodes may be mounted on a rigid printed circuit board (e.g., a circuit board formed from a rigid substrate such as FR4 or other fiberglass-filled epoxy), a flexible printed circuit board (e.g., a flex circuit formed from a sheet of flexible polymer such as a sheet of polyimide), a rigid flex substrate, or a plastic part or other dielectric structure that serves as a support. 
     Multiple components may be mounted on a common substrate in assembly  10 . For example, components  14  may include integrated circuits, switches, capacitors, inductors, resistors, and other circuitry that are mounted to the same printed circuit board to which the UV LED light source is mounted. The substrate may be mounted to structures such a structures  12 A and  12 B (e.g., using support structures such as frame structures to which the substrate may be attached with screws, other fasteners, or adhesive, etc.). 
     Path  18  may be formed by connecting wires or other conductive paths to the light source of assembly  10 . For example, a cable may be temporarily attached between tool  16  and assembly  10 . Tool  16  may include a power source and control circuitry (e.g., tool  16  may be based on a computer or other control unit that has a controllable output port through which power and control signals may be provided). With one suitable arrangement, path  18  may be formed using a connector port that is part of assembly  10 . The connector port may, for example, have an associated connector such as a 30-pin connector, a universal serial bus (USB) connector, a memory card slot connector, a connector for other removable media or cables, etc. 
       FIG. 2  shows how tool  16  may include control circuitry such as control circuitry  32  that applies signals to assembly  10  during manufacturing operations. Tool  16  may have a power source such as power supply  34 . Power supply  34  may be, for example, an alternating current (AC) to direct current (DC) power converter that produces DC power from an AC line source or a DC-DC converter that produces DC power from a battery (as examples). Control circuitry  32  may supply signals such as power signals from power supply  34  to assembly  10  over path  18 . Path  18  may include path segment  18 A, path segment  18 B, and path segment  18 C. 
     Path segment  18 A may be an internal path in tool  16  that connects control circuitry  32  to connector  30 . Connector  30  may be a male or female connector in the housing of tool  16  or may be a connector located at the end of a cable that is pigtailed to tool  16 . As shown in  FIG. 2 , connector  30  may mate with connector  28  in assembly  10 . 
     Path  18 B may be a path that is associated with connector  28 . Connector  28  may be a 30-pin connector, a USB connector, a media card connector, a cable connector, or any other connector associated with assembly  10 . Connector  28  may be mounted to structures such as structure  12 A and  12 B (e.g., device housings or internal support structures), may be attached to printed circuit board substrates or other connectors associated with assembly  10 , etc.). 
     Path  18 C may be a path that is formed from conductive lines associated with substrate  26 , wires, conductive lines attached to housing structures, conductive paths associated with structures  12 A and  12 B, etc. The conductive lines of path  18 C may be, for example, conductive traces on a printed circuit board substrate or other suitable substrate (e.g., substrate  26 ). 
     As shown in  FIG. 2 , components and light source  14  may include light sources  14 A and components  14 B. Light sources  14 A may be UV LEDs. Components  14 B may be integrated circuits and other circuit components mounted to substrate  26 . Substrate  26  may be a rigid printed circuit board substrate, a flex circuit, a rigid flex, a plastic support, or other suitable support structure. 
     After structures  12 A and  12 B, components  14 , and adhesive  20  have been placed in the position shown in  FIG. 2 , tool  16  may supply signals to assembly  10  that cause LEDs  14 A to supply UV light  22  to adhesive  20 , thereby curing adhesive  20 . Because this curing operation can be performed using light  22  that is generated within interior cavity  24  of assembly  10 , LEDs  14 A may sometimes be referred to as internal light sources and light  22  may sometimes be referred to as being internally generated. Adhesive  20  may sometimes be referred to as being internally cured by light  22 . Once internally generated light  22  or other suitable light has been used to cure adhesive  20 , tool  16  may be removed from assembly  10  (i.e., connector  28  of assembly  10  and connector  30  of tool  16  may be disconnected). 
     There may be one or more light sources such as UV LEDs  14 A within cavity  24 . For example, there may be two LEDs  14 A mounted to upper surface  26 A of substrate  26  and two LEDs  14 A mounted to lower surface  26 B of substrate  26 , as shown in the cross-sectional end view of assembly  10  that is shown in  FIG. 3 . If desired, there may be more LEDs  14 A (i.e., more than four LEDs) or fewer than four LEDs  14 A in assembly  10 . LEDs  14 A may all be mounted to the same substrate within cavity  24  (i.e., a common printed circuit board substrate or other substrate) or may be mounted to different substrates (e.g., multiple printed circuit boards). Structures such as structure  12  of  FIG. 3  may be formed by structures such as structures  12 A and  12 B of  FIGS. 1 and 2  (as examples). 
     Illustrative circuitry that may be provided in assembly  10  to allow adhesive  20  to be cured with internally generated light in assembly  10  is shown in  FIG. 4 . As shown in  FIG. 4 , connector  28  may have one or more input-output terminals. In the example of  FIG. 4 , connector  28  has six input-output terminals (input-output pins P 0 -P 5 ). In general, connector  28  may have any suitable number of terminals. For example, connector  28  may have  30  contacts (e.g., in a 30-pin connector), may have  10  contacts, may have fewer than  10  contacts, may have two contacts, may have more than  10  contacts, or may have any other suitable number of contacts. Contacts in connector  28  may be connected to contact pads formed from planar metal structures, may be connected to pins formed from elongated prongs, or may be connected to other suitable conductive structures. These structures, which are sometimes referred to as input-output pins may serve as inputs, outputs, or both inputs and outputs for connector  28 . When assembly  10  is coupled to tool  16 , connector  30  may be connected to connector  28  and some or all of pins  28  may be electrically connected to respective input-output pins in connector  30 . 
     Assembly  10  may include circuitry  36 . For example, assembly  10  may be an electronic device or part of an electronic device such as a computer, cellular telephone, media player, or other electronic equipment. Circuitry  36  may include components such as integrated circuits and other components (shown as components  14 B in  FIG. 2 ) that are mounted to one or more substrates such as printed circuit board  26 . Conductive lines (e.g., traces on printed circuit board  26 ) may be used to form conductive paths  46  between circuitry  36 , the input-output pins of connector  28 , and LEDs  14 A. 
     As shown in  FIG. 4 , light-emitting diodes such as LED  14 A may be coupled to input-output pins in connector  28 . If, for example, there is a single LED  14 A in assembly  10 , that LED may be coupled between a pair of the input-output pins in connector  28 . If more LEDs are included in assembly  10 , more input-output pins may be connected to the LEDs or the LEDs may be wired in parallel or in series. In the  FIG. 4  example, LED  14 A has a first terminal that is connected to pin P 0  by conductive line  40  and second terminal that is connected to pin P 2  by conductive line  38 . Optional fuse  42  has been interposed in path  38 . When tool  16  and assembly  10  are connected to each other, tool  16  can use circuitry  32  to apply signals to pins P 0  and P 2 . The signals that are applied to pins P 0  and P 2  may be, for example, power supply signals (e.g., a positive power supply voltage and a ground power supply voltage) that are produced by power supply  34  and routed to pins P 0  and P 2  by control circuitry  32 . When power is applied to the terminals of LED  14 A, LED  14 A produces UV light  22 . 
     The input-output pins of connector  28  to which tool  16  applies signals for controlling LED  14 A may be normally unused input-output pins. If for example, normal operation of circuitry  36  involves the use of pins P 1 , P 3 , P 4 , and P 5 , but does not involved the use of pins P 0  and P 2 , input-output pins P 0  and P 2  can be used to power LED  14 A during UV curing operations, while remaining unused during normal operation of circuitry  36  (e.g., when circuitry  36  is being operated as an integral part of an electronic device that is in use by a user). Because unused pins are not needed by circuitry  36  during normal operation, paths such as paths  44  may remain unconnected (i.e., pins P 0  and P 2  can be electrically disconnected from circuitry  36 ). 
     To ensure that LED  14 A is not inadvertently activated after UV adhesive curing operations are complete, fuse  42  may be blown after LED  14 A has been used to cure adhesive  20 . For example, control circuitry  32  may apply a current to path  38  that exceeds the fuse threshold for fuse  42 . When this threshold has been exceeded, fuse  42  will become permanently open circuited, thereby preventing subsequent activation of LED  14 A. 
     Pins P 0  and P 2  need not be unused pins. For example, pins P 0  and P 2  may be attached to data input-output terminals in circuitry  36  using conductive lines where indicated by dashed lines  44  of  FIG. 4 , provided that these data input-output terminals are sufficiently robust to withstand damage when control circuitry  32  supplies pins P 0  and P 2  with signals during operation of LED  14 A. 
     As shown in  FIG. 5 , LED  14 A may be supplied with signals from connector  28  by routing signals through circuitry  36 . Paths  46  may be used to connect some or all of input-output pins P 0 , P 1 , P 2 , P 3 , P 4 , and P 5  (or other suitable input-output pins) to circuitry  36 . Circuitry  36  may be connected to LED  14 A using paths  38  and  40 . In response to signals from control circuitry  32  in tool  16  that are received via paths  46 , circuitry  36  may supply signals to LED  14 A over paths  38  and  40  that turn on LED  14 A. To prevent LED  14 A from being activated after adhesive  20  has been cured, circuitry  36  may blow a fuse, set a non-volatile memory bit, or otherwise disconnect paths  38  and  40  from connector  28  after LED  14 A has been used to cure adhesive  20 . Inadvertent operation of LED  14 A may also be prevented by providing circuitry  36  with a security mechanism (e.g., by requiring that circuitry  36  be activated by a particular pattern of signals from connector  28  before signals will be applied by circuitry  36  to LED  14 A). 
     In a typical scenario, tool  16  may supply LEDs such as LED  14 A of  FIGS. 4 and 5  with power (e.g., from power supply  34 ). If desired, power may also be supplied from a power supply that is internal to assembly  10  or that is otherwise associated with a device or structure into which assembly  10  is being incorporated. For example, assembly  10  (or a device into which assembly  10  is incorporated), may include a battery such as battery  48  that is coupled to circuitry  36  by power supply paths  50 . During normal operation of assembly  10  in a device, battery  48  may power circuitry  36  (e.g., to display images for a user on a display, to play audio for a user, to control other operations in an electronic device, etc.). During assembly operations in which structures such as structures  12 A,  12 B, components and light source  14 , and adhesive  20  are being assembled to form a finished assembly, circuitry  36  may route battery power from battery  48  to LED  14 A over paths  38  and  40 . 
     Tool  16  may control the application of power from battery  48  to LED  14 A. For example, tool  16  may supply control signals to circuitry  36  using connector  28  and paths  46 . In response to the control signals received from tool  16 , circuitry  36  may supply power from battery  48  to LED  14 A. 
     If desired, circuitry  36  may supply power from an internal power source such as battery  48  to LED  14 A without the need to be connected to an external controller such as tool  16 . For example, a technician may run a program or other code on circuitry  36 . This code may direct circuitry  36  to power LED  14 A from battery  48  for a particular amount of time (e.g.,  30  seconds or several minutes as examples). While LED  14 A is being powered in this way, internally generated UV light  22  is being applied to adhesive  20  to cure adhesive  20 . Once light application is complete, circuitry  36  can deactivate LED  14 A. 
       FIGS. 6, 7, and 8  show how structures such as structures  12 A and  12 B of  FIG. 1  may each be formed using two or more materials. A structure for assembly  10  may, for example, be formed using multiple shots of plastic. Each shot of plastic may, if desired, have different properties. For example, one shot of plastic may be opaque and another shot of plastic may be transparent. The opaque shots of plastic may be used on the exterior of assembly  10  (e.g., to form exterior device housing walls). The transparent shots of plastic may be used as internal light pipe structures that help convey UV light  22  from LED  14 A to adhesive  20 . 
     A first shot of plastic may, for example, be molded into the shape of plastic shot  50 A of  FIG. 6 . Plastic shot  50 A may be opaque. A second shot of plastic such as shot  50 B may be added to plastic shot  50 A (e.g., using an injection molding tool), as shown in  FIG. 7 . Because structures  50 A and  50 B are formed as separate shots in a two-shot molding process, resulting structure  50  is a unitary one-piece part having an opaque portion ( 50 A) and a transparent portion ( 50 B). 
     As shown in  FIG. 8 , structure  50  may be attached to structure  54  in assembly  10  using liquid UV adhesive  20 . During curing operations, LED  14 A on substrate  26  may be activated to produce UV light  22 . Because structure  50 B is transparent, light  22  may be guided within parts of structure  50 B due to the principle of total internal reflection before exiting structure  50 B in the vicinity of adhesive  20 . In this way, transparent structure  50 B may serve as a light pipe that helps to guide and distribute light  22  from light-emitting diode  14 A to adhesive  20 . Upon reaching adhesive  20 , light  22  may be absorbed and distributed within adhesive  20  to cure adhesive  20 . Structures such as structure  50  and  54  may serve as structures  12 A and  12 B of  FIGS. 1A, 1B, and 2 . 
     Transparent light pipe structures may be formed from transparent plastic (e.g., one shot of a multishot injection-molded part or a single piece of transparent plastic), glass, transparent ceramics, etc.  FIG. 9  is a cross-sectional side view showing how light  22  may be distributed using a transparent member such as member  58 . Member  58  may be an internal frame structure, a housing structure, or other structure in assembly  10 . In the example of  FIG. 9 , member  58  is transparent, but member  56  is opaque. In general, the structures that are connected to each other using UV-cured adhesive  20  may both be transparent, may both be opaque, or may include some opaque portions and some transparent portions. As shown in  FIG. 9 , use of a transparent structure such as structure  58  may facilitate distribution of light  22  to adhesive  20  so that adhesive  20  can cure and attach structures  56  and  58  together in assembly  10 . In the  FIG. 9  example, structure  58  serves as a light pipe that distributes light  22  to a variety of internal locations within assembly  10 . Structures such as structure  58  may be elongated or may be compact, may be straight or may have bends, and may or may not have notches and other engagement features (as shown in the  FIG. 9  example), 
     As shown in  FIG. 10 , light  22  from light-emitting diode  14 A may cure adhesive that is being used to join internal members in assembly  10  to each other. Assembly  10  may, for example, have a structure such as structure  12  that serves as a housing. Interior structures such as structure  60  and  62  in interior cavity  24  may be joined using adhesive  20  that is cured by light  22  from LED  14 A. 
     In the  FIG. 10  example, structure  60  is being joined to structure  62  by adhesive  20 . Structure  60  may be opaque or transparent. Structure  62  may also be opaque or transparent. To ensure that light  22  can pass through portion  64  of structure  62 , portion  64  of structure  62  may be provided with one or more openings such as opening  66  (e.g., perforations, holes, or other structures that allow light  22  to pass through structure  62 . Light may also be allowed to pass by forming portion  64  of structure  62  from a transparent material as described in connection with transparent second shot  50 B of  FIG. 8 . If desired, structures  60  and  62  may be external housing structures. 
       FIG. 11  is a perspective view of housing structures and internal portions of an electronic device (device  66 ) of the type that may be formed using internally cured adhesive. As shown in  FIG. 11 , device  66  may have a housing shell such as shell  70  that is formed from plastic, metal, composites, ceramics, or other suitable housing materials (e.g., opaque structures). Shell  70  may be used to house internal device components  68 . Components  68  may include integrated circuits and other components (see, e.g., components  14  of  FIG. 1A ). Light sources such as LEDs  14 A may be mounted on components  68  (e.g., on substrate portions  26 ). Connector  72  may be, for example, a 30-pin connector, a USB connector, or other electrical connector. During assembly, UV adhesive  20  may be placed in regions  74  of shell  70  and/or near LEDs  14 A of structures  68 . Structures  68  may then be slid into housing shell  70  in direction  76  to produce the arrangement shown in  FIG. 12 . 
     As shown in  FIG. 12 , device  66  may have a cap such as cap  78 . As part of the process of assembling device  66 , connector  72  may be inserted through hole  80  in cap  78  as cap  78  is inserted into shell  70  in direction  76 . Once cap  78  is in place, connector  72  may be inserted into tool  16  as described in connection with  FIG. 2 . LEDs  14 A may be activated to produce light  22 . Light  22  may cure adhesive  20  to hold the structures of device  66  together. A perspective view of a finished version of device  66  is shown in  FIG. 13 . 
       FIG. 14  shows illustrative steps that may be involved in forming assemblies (e.g., electronic devices, portions of electronic devices, or other groups of structures) by connecting structures with liquid adhesive and applying light from a light source in the assembly. The light source may, for example, be contained in an interior cavity in the assembly such as cavity  24  ( FIG. 1B ). 
     At step  80 , structures for the assembly may be formed (e.g., printed circuit boards and other substrates  26  may be constructed and populated with LEDs  14 A and other components, housing structures and other structures for the assembly may be formed (e.g., using opaque and transparent shots of plastic in an injection molding process, using metal, using composites, etc.). 
     At step  82 , the structures that have been formed may be assembled using UV liquid adhesive  20 . For example, structures such as structures  12 A and  12 B and internal components  14  may be connected together using adhesive  20 . 
     At step  84 , the assembly that has been formed may be connected to tool  16 . For example, connectors  30  and  28  of  FIG. 2  may be coupled together to allow circuitry  32  to supply signals to LEDs  14 A in assembly  10 . 
     At step  86 , circuitry  32  may supply signals to LEDs  14 A to activate LEDs  14 A and thereby produce light  20  that cures adhesive  20 . 
     At step  88 , LEDs  14 A may optionally be disabled (e.g., by blowing a fuse such as fuse  42  of  FIG. 4 ). 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20100528
Publication Date: 20160927
Grant Date: 20160927
Priority Date: 20100528
Inventors: STANLEY CRAIG MATTHEW
Assignee: APPLE INC
CPC Classifications: [{"code": "H05K5/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K5/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K3/321", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/149", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/1406", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C45/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/542", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K5/0004", "inventive": true, "first": true, "tree": "[]"}, {"code": "B29C65/4825", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10106", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/1435", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/4845", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/1122", "inventive": false, "first": false, "tree": "[]"}, {"code": "F16B11/006", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/5326", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C45/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/4845", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/1122", "inventive": false, "first": false, "tree": "[]"}, {"code": "F16B11/006", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/321", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/10106", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/4825", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/5326", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/542", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/1435", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/1406", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/149", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/61", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/1435", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/1406", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/149", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C45/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/4845", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/1122", "inventive": false, "first": false, "tree": "[]"}, {"code": "F16B11/006", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/321", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/10106", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/4825", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/5326", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/542", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/61", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 45021977