PATENT DOCUMENT

Publication Number: US-10300658-B2
Application Number: US-201213628568-A
Country: US
Kind Code: B2

Title: Crack resistant plastic enclosure structures

Abstract:
Electronic device housing structures and other structures may be formed from molded plastic. Plastic structures such as injection molding housing structures and other structures may be provided with openings. An opening may have sidewall surfaces. Machining operations and other techniques may be used in forming the openings. Openings may be processed to enhance resistance to stress-induced cracking of the plastic structures along the sidewall surfaces. Cracking resistance may be obtained by activating the surface using heat or laser treatment and by electroplating the activated surface to form a metal liner structure. Surface treatments using applied liquid chemicals or heat may form a treated layer on the surface of an opening with enhanced cracking resistance. A plastic sleeve or other insert may form a liner structure in an opening that resists cracking. Liner structures may also be formed by applying heat or light to a coating in an opening.

Claims:
What is claimed is: 
     
       1. A method comprising:
 molding a plastic housing structure for an electronic device that has an outer surface which defines an exterior surface of the electronic device and an opposing inner surface; 
 machining an opening having a depth in the molded plastic housing structure using a cutting tool to define an outer opening edge at the outer surface, an inner opening at the opposing inner surface, and an opening sidewall extending substantially from the outer opening edge to the inner opening edge, the opening is configured to receive a component selected from the group consisting of: a button, a status indicator light, a sensor, and a plug; 
 thermally activating the opening sidewall with a laser or with the cutting tool while machining the opening; 
 forming a metal liner structure directly along the thermally activated opening sidewall by electrochemically depositing metal, the metal bonding to the plastic housing structure, such that the metal liner structure connects the outer surface and the opposing inner surface and is of a height substantially equal to the depth of the opening, and wherein a first end of the metal liner structure is positioned in line with the outer opening edge and a second end of the metal liner structure opposite the first end is positioned with the inner opening edge; and 
 mounting a display in the plastic housing structure wherein the display has pixels. 
 
     
     
       2. The method defined in  claim 1 , wherein the display is a touch screen. 
     
     
       3. The method defined in  claim 1 , wherein the opening is configured to receive the button, and wherein the button is configured to receive user input. 
     
     
       4. The method defined in  claim 1 , wherein the opening is configured to receive the status indicator light. 
     
     
       5. The method defined in  claim 1 , wherein the opening is configured to receive the sensor. 
     
     
       6. The method defined in  claim 1 , wherein the opening is configured to receive the plug, and wherein the plug is a digital signal plug. 
     
     
       7. The method defined in  claim 1 , wherein:
 the opening is configured to receive the plug; and 
 the plug is an audio plug. 
 
     
     
       8. The method defined in  claim 1 , wherein:
 the opening is exposed to the exterior of the electronic device. 
 
     
     
       9. The method defined in  claim 1 , wherein machining the opening using the cutting tool to thermally activate the opening sidewall further comprises applying the cutting tool on the opening side wall for a determined dwell time to apply heat to the opening sidewall. 
     
     
       10. The method defined in  claim 1 , wherein the cutting tool comprises a cutting tool selected from the group consisting of a drill bit, a saw blade, a milling machine cutter, and a grinder. 
     
     
       11. The method defined in  claim 1 , wherein molding the plastic housing structure comprises injection molding the plastic housing structure. 
     
     
       12. The method defined in  claim 1 , wherein the metal liner structure comprises a metal selected from the group consisting of copper and nickel. 
     
     
       13. The method defined in  claim 1 ,
 wherein the opening sidewall is thermally activated with a laser after machining the opening using the cutting tool and before forming the metal liner structure. 
 
     
     
       14. A method for forming a plastic housing structure for an electronic device, comprising:
 molding the plastic housing structure including an exterior surface and an opposing interior surface, wherein the exterior surface defines an exterior surface of the electronic device; 
 drilling an opening in the molded plastic housing structure, wherein: 
 the opening in the molded plastic housing structure has a depth and is defined by a wall surface that extends substantially from an interior edge at the interior surface to an exterior edge at the exterior surface; 
 the opening is configured to receive at least one of: a button, a status indicator, a sensor, or a plug; and 
 a dwell time of a cutting tool on the wall surface is selected to apply sufficient heat to the wall surface to activate the wall surface for forming a metal liner structure; 
 forming the metal liner structure on the wall surface from the exterior edge to the interior edge using electrochemical deposition directly on the plastic of the wall surface, the metal liner structure having a height substantially equal to the depth of the opening, and wherein a first end of the metal line structure is positioned in line with the exterior edge and a second end of the metal liner structure opposite the first end is positioned with the interior edge; and 
 mounting a display with pixels in the plastic housing structure of the electronic device.

Description:
This application claims the benefit of provisional patent application No. 61/642,426, filed May 3, 2012, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to plastic structures, and more particularly, to forming plastic structures that resist cracking. 
     Electronic devices such as portable computers and cellular telephones are often provided with plastic structures such as plastic housings. To accommodate ports for connectors and components such as buttons, openings must be formed in these plastic structures. Openings that are formed as part of a plastic molding operation may exhibit poorly defined edges. Machining operations can be used to form openings with crisp edges, but may impart residual stress. Residual stress in a plastic structure may lead to premature cracking during use of a device. If care is not taken, cracks may become unsightly or may compromise the structural integrity of a housing for an electronic device. 
     It would therefore be desirable to be able to provide improved plastic structures with openings such as improved plastic housing structures. 
     SUMMARY 
     Electronic device housing structures and other structures may be formed from molded plastic. Plastic structures such as injection molding housing structures and other structures may be provided with openings. Machining operations and other techniques may be used in forming the openings. 
     Openings in the plastic structures may have sidewall surfaces. The openings may be processed to enhance resistance to stress-induced cracking of the plastic structures along the sidewall surfaces. Enhanced cracking resistance may be obtained by activating the surface using heat or laser treatment and by electroplating the activated surface to form a metal liner structure. Surface treatments such as treatments involving the application of chemicals or heat may be used to form a treated layer on the surface of an opening that exhibits an enhanced cracking resistance. A plastic sleeve or other insert may form a liner structure in an opening to help resist cracking. Liner structures may also be formed by depositing a coating on a sidewall surface and applying heat or light to the coating. 
     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. 1  is a front perspective view of an illustrative electronic device of the type that may have a plastic structure with an opening such as a plastic housing structure in accordance with an embodiment of the present invention. 
         FIG. 2  is a diagram of a tool for performing machining operations in accordance with an embodiment of the present invention. 
         FIG. 3  is a diagram of a tool for applying energy to a structure in the form of light, acoustic signals, or other types of energy in accordance with an embodiment of the present invention. 
         FIG. 4  is a diagram of a tool for applying substances such as liquids and pastes to a structure in accordance with an embodiment of the present invention. 
         FIG. 5  is a diagram of illustrative deposition equipment for depositing material onto a structure in accordance with an embodiment of the present invention. 
         FIG. 6  is a diagram of illustrative heating equipment in accordance with an embodiment of the present invention. 
         FIG. 7  is a diagram of illustrative water-jet cutting equipment in accordance with an embodiment of the present invention. 
         FIG. 8  is a diagram of illustrative electrochemical deposition equipment in accordance with an embodiment of the present invention. 
         FIG. 9  is a side view of an illustrative plastic structure prior to forming an opening in the plastic structure in accordance with an embodiment of the present invention. 
         FIG. 10  is a cross-sectional side view of the plastic structure of  FIG. 9  after forming an opening in the plastic structure in accordance with an embodiment of the present invention. 
         FIG. 11  is a graph showing how hole formation operations may impart residual stress into a plastic structure in accordance with an embodiment of the present invention. 
         FIG. 12  is a cross-sectional side view of plastic structures of the type that may be provided with an electroplated metal liner structure in accordance with an embodiment of the present invention. 
         FIG. 13  is a cross-sectional side view of the plastic structures of  FIG. 12  following formation of an opening in accordance with an embodiment of the present invention. 
         FIG. 14  is a cross-sectional side view of the plastic structures of  FIG. 13  showing how the exposed inner surface of the opening may be treated with light to activate the exposed inner surface for subsequent metal plating operations in accordance with an embodiment of the present invention. 
         FIG. 15  is a cross-sectional side view of the plastic structures of  FIG. 14  following electroplating operations to grow a layer of metal on the inner surface of the opening in accordance with an embodiment of the present invention. 
         FIG. 16  is a flow chart of illustrative steps involved in forming plastic structures having an opening that is coated with plated metal to reduce stress-induced cracking in accordance with an embodiment of the present invention. 
         FIG. 17  is a cross-sectional side view of plastic structures of the type that may be used in forming an opening that is provided with a surface treatment to reduce stress-induced cracking in accordance with an embodiment of the present invention. 
         FIG. 18  is a cross-sectional side view of the plastic structures of  FIG. 17  following formation of an opening in accordance with an embodiment of the present invention. 
         FIG. 19  is a cross-sectional side view of the plastic structures of  FIG. 18  showing how a surface treatment may be used to provide the inner surface of an opening with a treated layer having enhanced resistance to cracking in accordance with an embodiment of the present invention. 
         FIG. 20  is a flow chart of illustrative steps involved in forming plastic structures having an opening with walls that are provided with a surface treatment to reduce stress-induced cracking in accordance with an embodiment of the present invention. 
         FIG. 21  is a cross-sectional side view of plastic structures such as plastic electronic device housing structures in which an opening may be formed in accordance with an embodiment of the present invention. 
         FIG. 22  is a cross-sectional side view of the plastic structures of  FIG. 21  following formation of an opening in accordance with an embodiment of the present invention. 
         FIG. 23  is a cross-sectional side view of the plastic structures of  FIG. 22  showing how a sleeve structure may be inserted into the opening in accordance with an embodiment of the present invention. 
         FIG. 24  is a cross-sectional side view of the plastic structures of  FIG. 23  in which the sleeve structure of  FIG. 23  has been mounted in the opening to serve as a liner structure that provides the inner surface of the opening with enhanced resistance to cracking in accordance with an embodiment of the present invention. 
         FIG. 25  is a flow chart of illustrative steps involved in forming plastic structures having an opening with walls that receive a sleeve that serves as liner structures in accordance with an embodiment of the present invention. 
         FIG. 26  is a cross-sectional side view of plastic structures such as plastic electronic device housing structures in which an opening may be formed in accordance with an embodiment of the present invention. 
         FIG. 27  is a cross-sectional side view of the plastic structures of  FIG. 26  following formation of an opening in accordance with an embodiment of the present invention. 
         FIG. 28  is a cross-sectional side view of the plastic structures of  FIG. 27  in which a material has been used to coat the inner surface of the opening in accordance with an embodiment of the present invention. 
         FIG. 29  is a cross-sectional side view of the plastic structures of  FIG. 28  following treatment of the coating material on the inner surface of the opening to provide the inner surface of the opening with liner structures that enhance resistance to cracking in accordance with an embodiment of the present invention. 
         FIG. 30  is a flow chart of illustrative steps involved in forming plastic structures that are coated with a material and treated to provide an inner opening surface with enhanced resistance to cracking in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as electronic device  10  of  FIG. 1  and other electronic equipment may be provided with plastic housing structures and other plastic structures. Electronic device  10  may be a tablet computer, a cellular telephone, a media player, a portable computer, a computer integrated into a computer display, a desktop computer, a television, a wristwatch or other miniature device, or other electronic equipment. As shown in  FIG. 1 , device  10  may include a housing structure such as housing  12 . A display such as display  14  may be mounted in housing  12  (as an example). Display  14  may be a touch screen or may be a display that is insensitive to touch. 
     Housing  12 , which may sometimes be referred to as a case or enclosure, may be formed from one or more materials such as internal metal frame structures, optional peripheral conductive members such as metal housing wall structures and display bezels, internal support structures, carbon-fiber composites and other composite materials, glass, ceramics, etc. With one suitable arrangement, which is sometimes described herein as an example, structures in device  10  such as external housing structures  12  may be formed from plastic (e.g., a rigid polymer). Examples of plastics that may be used for forming housing structures  12  include polycarbonate (PC), acrylonitrile butadiene styrene (ABS), and PC/ABS blends (as examples). Other plastics may be used for forming portions of housing  12 , for forming other housing structures, and for forming other plastic structures associated with device  10 . 
     Housing  12  may have one or more openings such as openings  16 . Openings  16  may have circular shapes, rectangular shapes, overall shapes, shapes with curved edges, shapes with straight edges, shapes with combinations of curved and straight edges, or other suitable outlines. Openings  16  may be used to form ports for connectors. For example, openings  16  may include circular holes that receive audio plugs, rectangular holes to receive digital signal plugs, and openings of other shapes to receive other connectors. Openings  16  may also be used to accommodate buttons and other user input devices, openings to accommodate status indicator lights, openings to accommodate sensors, and openings to accommodate other components in device  10 . In the illustrative example of  FIG. 1 , openings  16  have been formed on sidewall portions of housing structures  12 . This is merely illustrative. Any suitable plastic structures in device  10  may be provided with openings such as openings  16  if desired. 
     Openings  16  or part of openings  16  may be formed during molding operations (e.g., by injection molding plastic into a die that contains mold structures for forming at least part of openings  16 ). If desired, machining tools or other equipment for removing material from plastic structures  12  may be used in forming openings  16  (e.g., to form openings  16  from a solid piece of plastic or to widen openings that have been partly formed during a molding process). To help prevent cracks from forming in the portions of plastic structures  12  in the vicinity of openings  16 , openings  16  may be exposed to surface treatment, may be supported by forming ancillary liner structures in openings  16 , or may otherwise be processed to resist cracking. 
       FIGS. 2-8  show illustrative equipment  18  of the type that may be used in forming openings  16  and in processing openings  16  to form liner structures and other structures that help openings  16  resist cracking. 
     As shown in  FIG. 2 , equipment  18  may include a machining tool having a computer-controlled positioner such as positioner  20  and a cutting structure such as structure  22  that is manipulated using positioner  20 . Positioner  20  may include a motor for rotating a shaft to which a cutter  22  is coupled, may include one or more linear actuators for adjusting the position of cutter  22 , or may include other positioning equipment. Cutter  22  may be rotated in direction  24  by positioner  20  (as an example). Cutting structures such as cutter  22  may include drill bits, saw blades, milling machine cutters, grinders, and other machining equipment. 
     As shown by equipment  18  in the example of  FIG. 3 , equipment  18  may include a source of energy  28  (e.g., a beam of localized energy or other localized energy) such as source  26 . Energy  28  may be electromagnetic energy (e.g., radio-frequency electromagnetic signals), light (e.g., laser light such as a laser beam), heat (e.g., infrared light in the form of lamp light or laser light), acoustic energy (e.g., ultrasonic acoustic signals for forming ultrasonic welds), or may be other forms of energy. Source  26  may be an ultrasonic acoustic signal generator (e.g., an ultrasonic welder), a light source such as a lamp that produces lamp light, a light source such as a laser that produces laser light, or other source of energy  28 . As an example, source  26  may be a laser that produces infrared light  28 , visible light  28 , or ultraviolet light  28 . The position of source  26  and energy  28  may be controlled using computer-controlled positioner  20 . 
       FIG. 4  is a diagram of equipment  18  in an illustrative configuration in which equipment  18  includes a nozzle or other dispensing equipment for dispensing material  32  from reservoir  34 . Equipment  18  may use computer-controlled positioner  20  to control the positioner of dispensing head  30  as material  32  is being dispensed. Material  32  may include liquid chemicals such as solvents, liquid adhesives, ultraviolet-light-cured liquid adhesive, liquid polymer precursors, solder paste, paint, or other suitable materials. 
     As shown in  FIG. 5 , equipment  18  may include deposition equipment  36  for depositing material  38 . Equipment  36  may include physical vapor deposition equipment, painting equipment, spraying equipment, screen printing equipment, pad printing equipment, inkjet equipment, dipping equipment, plastic injection molding equipment and other equipment for depositing material  38 . Material  38  may include polymeric materials such as thermoset and thermoplastic plastics, adhesive, solder paste, paint, metals, glass, ceramics, and other suitable materials. 
     As shown in  FIG. 7 , equipment  18  may include cutting equipment such as water-jet cutting equipment having a computer-controlled positioner such as positioner  20  and a water-jet nozzle such as nozzle  42 . As the position of water-jet nozzle  42  is controlled using positioner  20 , water-jet nozzle  42  may emit a jet of water such as water  44 . Abrasives or other materials in water jet  44  may facilitate the use of equipment  18  in cutting plastics and other materials. 
       FIG. 8  shows how equipment  18  may include electrochemical deposition equipment such as equipment  46 . Equipment  46  may be used to deposit metal. For example, equipment  46  may include a chemical bath for electroless plating of metals such as copper, nickel, or other metals or may include equipment for forming electrochemically deposited materials. 
     With equipment of the type shown in  FIGS. 2-8  and/or other suitable manufacturing equipment, openings such as openings  16  may be formed in housing  12  or other plastic structures. Consider, as an example, the arrangement of  FIGS. 9 and 10 . As shown in  FIG. 9 , plastic structures  12  (e.g., a housing wall in device  10 , other planar plastic structures, or other plastic material) may initially be free of holes. 
     Using equipment  18 , an opening such as opening  16  of  FIG. 10  may be formed in plastic structures  12 . Opening  16  may have a circular shape, a rectangular shape, or other suitable shape. As shown in the cross-sectional side view of  FIG. 10 , opening  16  may extend between opening sidewall surfaces  48 . Opening sidewall surfaces  48  may, for example, define a cylindrical opening shape (e.g., a cylindrical sidewall) for opening  16 . Opposing sidewalls  48  of  FIG. 10  run parallel to each other and perpendicular to outer surface  50  and inner surface  52  of plastic structures  12 , forming crisp right-angled outer edges such as edges (edge)  54 . This is, however, merely illustrative. In general, opening walls  48  may be tapered, may be flared, may have edge treatments that form a rounded feature along periphery  54 , or may have other suitable shapes. 
     Opening  16  may be formed using laser cutting equipment  18  of  FIG. 3 , water-jet cutting equipment such as equipment  18  of  FIG. 7 , or other suitable equipment for forming opening  16 . As an example, opening  16  may be formed using machining equipment such as machining equipment  18  of  FIG. 2  (e.g., a computer numerical control or CNC machine that uses a cutting tool to remove material from structure  12  during the process of forming opening  16 ). The use of a machining tool such as tool  18  of  FIG. 2  and other equipment may give rise to residual stress in material along the surfaces of opening  16  such as walls  48 . As shown in  FIG. 10 , opening  16  may be characterized by a depth along dimension X. A graph showing illustrative amounts of compressive and tensile stress that may be imparted along walls  48  as a function of distance X from outer edge  54  of opening  16  is shown in  FIG. 11 . As shown by curve  56 , walls  48  may be characterized by different amounts of stress at different corresponding values of distance X. This stress (e.g., regions such as region  56 ′ in which wall  48  is under considerable tensile stress) may serve to initiate the formation of cracks in direction  58  of  FIG. 10  such as crack  60 . Cracks such as crack  60  may extend over some or all of the height of walls  48  and may extend into structures  12 , causing cracking that may be visible along exterior surface  50  and potential structural weakness in plastic structures  12 . 
     To prevent cracks such as crack  60  from forming, opening  16  may be coated with a layer of a material that is less prone to stress cracking such as a layer of a material that exhibits more ductility than plastic  12 . An example of a ductile material that may be used to coat opening  16  and thereby help prevent the formation of stress cracks in opening  16  is metal (e.g., copper, nickel, etc.). Other suitable materials may be used to enhance the ability of opening  16  to withstand cracking if desired (e.g., a thermoset or thermoplastic plastic layer that is more ductile than plastic structures  12 , etc.). 
       FIGS. 12-15  show how opening  16  may be lined with a material such as plated metal to help prevent stress-induced cracking. Initially, plastic structures  12  may appear as shown in  FIG. 12 . Plastic structures  12  of  FIG. 12  may be, for example, planar injection molded housing structures characterized by a wall thickness T. The value of thickness T may be, for example, less than 5 mm, less than 4 mm, less than 3 mm, less than 2 mm, less than 1 mm, or less than 0.5 mm. In the illustrative configuration of  FIG. 12 , plastic structures  12  are free of coatings. This is merely an example. Plastic structures  12  may, if desired, be covered with paint, one or more additional layers of plastic, or other coatings. 
     As shown in  FIG. 13 , one or more openings such as opening  16  may be formed in plastic structures  12 . Openings such as opening  16  may be formed by using machining equipment such as machining equipment  18  of  FIG. 2  or other cutting equipment  18 . If desired, the dwell time of cutter  22  on surface  48  of opening  16  may be selected to impart sufficient thermal energy into plastic structures  12  to activate surface  48  for subsequent metal plating. Surface  48  may also be activated for subsequent metal plating (electrochemical metal growth) by shining light  28  on surface  48  as shown in  FIG. 14 . For example, equipment  18  of  FIG. 3  may be used to apply laser light  28  (e.g., infrared laser light or laser light of other wavelengths) to surface  48  or other surfaces associated with opening  16  that may be susceptible to stress-induced cracking. If desired, metal complexes may be incorporated into plastic structures  12  to enhance the ability of heat from cutting tool  22  and/or light such as laser light  28  to selectively activate surface  48  for subsequent electroplating. 
     Following activation of surface  48  using laser light  28  or activation of surface  48  by adjusting the dwell time of machining equipment such as equipment  18  of  FIG. 2  or otherwise selectively treating surface  48  with equipment  18 , electrochemical deposition equipment (e.g., electroless metal plating equipment) such as equipment  18  of  FIG. 8  may be used to form a metal layer such as metal layer  62  of  FIG. 15  on surfaces  48  of opening  16 . If desired, portions of outer surface  50  and/or inner surface  52  of plastic structures  12  may also be coated in this way. Metal  62  may be more ductile than plastic structures  12  and may therefore be more resistant to formation of stress-induced cracks in its surface. This may help eliminate the formation of stress-induced cracks in plastic structures  12  in the vicinity of opening  16 , even when the machining operations that were used to form opening  16  (e.g., the machining operations performed using machining equipment  18  of  FIG. 2 ) have the potential to introduce stresses into plastic structure  12 . Examples of metals that may be plated onto surface  48  of opening  16  include copper and nickel. Metal  62  may be formed from other metals or combinations of metals, if desired. 
     A flow chart of illustrative steps involved in forming a metal-coated opening such as metal-coated opening  16  of  FIG. 15  is shown in  FIG. 16 . 
     At step  64 , an injection molding operation or other operation may be used in forming plastic structures  12 . For example, plastic such as polycarbonate, ABS, PC/ABS, or other thermoplastic materials may be injection molded into a metal mold having a shape of an electronic device housing structure for an electronic device such as electronic device  10  of  FIG. 1 . The plastic material that is used in forming structures  12  may include metal complexes for enhancing the ability of light and/or heat to selectively activate the surface of plastic structures  12  for subsequent electrochemical deposition of metal. The plastic structures that are formed during the operations of step  64  may include electronic device housing walls having a thickness of less than 5 mm, less than 4 mm, less than 3 mm, less than 2 mm, less than 1 mm, or less than 0.5 mm (as examples). 
     At step  66 , machining equipment such as machining tool  18  of  FIG. 2  may be used to form opening  16  of  FIG. 13 . In forming opening  16 , cutter  22  of  FIG. 2  may, if desired, be caused to dwell sufficiently long on surface  48  to activate surface  48  for subsequent metal growth. Alternatively, or in addition to using dwell time activation techniques, surface  48  may be activated by applying laser light  28  to surface  48  using equipment  18  of  FIG. 3  (step  68 ). 
     At step  70 , electrochemical deposition equipment  18  of  FIG. 8  may be used to plate copper, nickel, or other metal  62  onto walls  48  of opening  16 , as shown in  FIG. 15 . 
     If desired, the surfaces of opening  16  may be treated to enhance the ability of opening  16  to withstand stress-induced cracking. An illustrative surface treatment scheme is illustrated in  FIGS. 17, 18 and 19 . 
     Initially, plastic structures  12  may appear as shown in  FIG. 17 . Plastic structures  12  of  FIG. 17  may be planar injection molded housing structures characterized by a wall thickness T (e.g., a wall thickness of 0-5 mm or other suitable thickness), as described in connection with  FIG. 12 . Plastic structures  12  may be, for example, wall structures for a plastic housing for electronic device  10  of  FIG. 1 . 
     As shown in  FIG. 18 , one or more openings such as opening  16  may be formed in plastic structures  12  of  FIG. 17 . Openings such as opening  16  may be formed by using machining equipment such as machining equipment  18  of  FIG. 2  or other cutting equipment  18 . As described in connection with  FIGS. 10 and 11 , hole formation processes such as machining processes have the potential for introducing stresses into the surface of structures  12  along walls  48  of opening  16 . These stresses have the potential to give rise to cracks. To enhance the ability of plastic structures  12  to withstand crack formation on walls  48 , the surface of walls  48  may be treated using chemicals, heat, light, or other surface treatments. For example, a solvent may be applied to the surface of walls  48  to locally soften walls  48  and relieve built-in stresses, laser light may be applied to locally heat and soften walls  48 , ultrasonic energy may be applied to heat and soften walls  48 , or heat from a heated tool or an infrared lamp may be applied to locally soften walls  48 . Following treatment using these techniques or other suitable surface treatment techniques, walls  48  may be lined with a surface-treated layer (e.g., a chemically treated layer, a thermally softened and re-hardened layer, or a melted and re-hardened layer) such as layer  72  of  FIG. 19  that is better able to withstand cracking than untreated surface  48  of  FIG. 18 . 
     A flow chart of illustrative steps involved in treating the surface of opening  16  in plastic structures  12  to enhance the ability of plastic structures  12  to withstand stress-induced cracking is shown in  FIG. 20 . 
     At step  74 , an injection molding operation or other operation may be used in forming plastic structures  12 . For example, plastic such as polycarbonate, ABS, PC/ABS, or other thermoplastic materials may be injection molded into a metal mold having a shape of an electronic device housing structure for an electronic device such as electronic device  10  of  FIG. 1 . The plastic structures that are formed during the operations of step  74  may include electronic device housing walls having a thickness of less than 5 mm, less than 4 mm, less than 3 mm, less than 2 mm, less than 1 mm, or less than 0.5 mm (as examples). 
     At step  76 , equipment such as machining tool  18  of  FIG. 2 , laser cutting equipment (see, e.g., equipment  18  of  FIG. 3 ), water-jet cutting equipment such as equipment  18  of  FIG. 7 , or other equipment may be used to form opening  16  of  FIG. 18 . In forming opening  16 , stress may be imparted to wall  48 . 
     At step  78 , equipment  18  (e.g., equipment  18  of  FIG. 3  or other heating equipment, equipment for applying a solvent or other chemical to the surface of opening  16  of  FIG. 18  such as equipment  18  of  FIG. 4 , or other suitable surface treatment tool) may be used in treating the surface of walls  48  of opening  16 , thereby forming surface-treated layer  72  on the surface of walls  48  in opening  16 , as shown in  FIG. 19 . 
     If desired, the surfaces of opening  16  may be lined with an insert structure such as a cylindrical sleeve or a sleeve with other suitable shapes configured to mate with the inner surfaces of walls  48  in opening  16 . Mounting the sleeve structure within opening  16  may form a liner structure to help enhance the ability of opening  16  to withstand stress-induced cracking. An illustrative lining scheme is illustrated in  FIGS. 21, 22, 23, and 24 . 
     Initially, plastic structures  12  may appear as shown in  FIG. 21 . Plastic structures  12  of  FIG. 21  may be planar injection molded housing structures characterized by a wall thickness T (e.g., a wall thickness of 0-5 mm or other suitable thickness), as described in connection with  FIG. 12 . Plastic structures  12  may be, for example, wall structures for a plastic housing for electronic device  10  of  FIG. 1 . 
     As shown in  FIG. 22 , one or more openings such as opening  16  may be formed in plastic structures  12  of  FIG. 21 . Openings such as opening  16  may be formed by using machining equipment such as machining equipment  18  of  FIG. 2  or other cutting equipment  18 . As described in connection with  FIGS. 10 and 11 , hole formation processes such as machining processes have the potential for introducing stresses into the surface of structures  12  along walls  48  of opening  16 . These stresses have the potential to give rise to cracks. 
     To enhance the ability of plastic structures  12  to withstand crack formation on walls  48 , the surface of walls  48  may be lined with an insert structure such as sleeve  80  of  FIG. 23 . Sleeve  80  may have a shape that is configured to mate with opening  16  of  FIG. 22 . For example, if opening  16  of  FIG. 22  has a circular shape, sleeve  80  may have the shape of a cylindrical hollow ring with an outer diameter that matches the diameter of hole  16  of  FIG. 22 . If opening  16  has another shape (e.g., a rectangular shape), sleeve  80  may have the shape of a hollow rectangular ring (as an example).  FIG. 23  shows how sleeve  80  may be inserted into opening  16  in direction  82 . As shown in  FIG. 24 , the center of sleeve  80  is hollow, so that sleeve  80  forms a lining to walls  48  without blocking opening  16 . 
     Sleeve  80  may be attached within opening  16  by welding using equipment  18  of  FIG. 3  (e.g., laser welding, ultrasonic welding, etc.), by applying a chemical such as a plastic solvent or adhesive between sleeve  80  and the surface of walls  48  of opening  16  of  FIG. 22  using equipment  18  of  FIG. 4 , by heating sleeve  80  and/or structures  21  using heating equipment  18  of  FIG. 6  or equipment  18  of  FIG. 3 , or by otherwise attaching the structures of sleeve  80  to plastic structures  12 . Sleeve  80  may be formed from plastic, metal, carbon-fiber composites or other composite materials, glass, ceramic, other materials, or combinations of these materials. If desired, sleeve  80  may be formed in the position shown in  FIG. 24  by injection molding (e.g., by forming sleeve  80  from a shot of plastic on top of existing plastic structures  12 ). 
     A flow chart of illustrative steps involved in lining the surfaces of opening  16  in plastic structures  12  with sleeve structures  80  to enhance the ability of plastic structures  12  to withstand stress-induced cracking is shown in  FIG. 25 . 
     At step  82 , an injection molding operation or other operation may be used in forming plastic structures  12 . For example, plastic such as polycarbonate, ABS, PC/ABS, or other thermoplastic materials may be injection molded into a metal mold having a shape of an electronic device housing structure for an electronic device such as electronic device  10  of  FIG. 1 . The plastic structures that are formed during the operations of step  82  may include electronic device housing walls having a thickness of less than 5 mm, less than 4 mm, less than 3 mm, less than 2 mm, less than 1 mm, or less than 0.5 mm (as examples). 
     At step  84 , equipment such as machining tool  18  of  FIG. 2 , laser cutting equipment (see, e.g., equipment  18  of  FIG. 3 ), water-jet cutting equipment such as equipment  18  of  FIG. 7 , or other equipment may be used to form opening  16  of  FIG. 18 . In forming opening  16 , stress may be imparted to wall  48 . 
     At step  86 , equipment  18  (e.g., laser equipment  18  of  FIG. 3 , an ultrasonic welder, or other equipment that can deposit localized energy to walls  48 , equipment for applying a solvent or other chemical to the surface of opening  16  of  FIG. 18  such as equipment  18  of  FIG. 4 , or other suitable equipment) may be used in attaching sleeve  80  two the inner surface of opening  16 , thereby forming lined opening  16  of  FIG. 24 . If desired, sleeve  80  may be formed by injection molding sleeve structures  80  directly on top of plastic structures  12  using plastic injection molding equipment (e.g., equipment  18  of  FIG. 5 ). 
     The surfaces of opening  16  may, if desired, be provided with a coating that is treated to help enhance the ability of opening  16  to withstand stress-induced cracking. An illustrative lining scheme based on depositing coatings and treating the deposited coatings is illustrated in  FIGS. 21, 22, 23, and 24 . 
     Initially, plastic structures  12  may appear as shown in  FIG. 26 . Plastic structures  12  of  FIG. 26  may be planar injection molded housing structures characterized by a wall thickness T (e.g., a wall thickness of 0-5 mm or other suitable thickness), as described in connection with  FIG. 12 . Plastic structures  12  may be, for example, wall structures for a plastic housing for electronic device  10  of  FIG. 1 . 
     As shown in  FIG. 27 , one or more openings such as opening  16  may be formed in plastic structures  12  of  FIG. 26 . Openings such as opening  16  may be formed by using machining equipment such as machining equipment  18  of  FIG. 2  or other cutting equipment  18 . As described in connection with  FIGS. 10 and 11 , the machining process has the potential for introducing stresses into the surface of structures  12  along walls  48  of opening  16 . These stresses have the potential to give rise to cracks. To enhance the ability of plastic structures  12  to withstand crack formation on walls  48 , the surface of walls  48  may be coated with coating  88  of  FIG. 28 . Coating  88  may be solder paste or other precursor to forming a metal layer, may be a polymer precursor such as liquid (uncured) epoxy, or may be other coating materials. 
     After applying a layer of material such as coating  88  to walls  48  of opening  16 , coating  88  may be treated with light or heat to form liner layer  90  of  FIG. 29 . If, for example, layer  88  is a layer of thermally curable epoxy, heat may be applied to cure layer  88  (e.g., using heating equipment  40  of  FIG. 6  or equipment  18  of  FIG. 3 ) to form layer  90 . If layer  88  is formed from ultraviolet-light-curable epoxy, layer  88  may be cured by application of ultraviolet light (e.g., using equipment  18  of  FIG. 3 ). If layer  88  is formed from a solder paste or other metal paste or paint, layer  88  may be heated using heating equipment  18  of  FIG. 18  (e.g., a reflow oven) or other heating equipment to form liner layer  90  of  FIG. 29 . 
     A flow chart of illustrative steps involved in forming lining structures such as structures  90  on walls  48  of opening  16  in plastic structures  12  to enhance the ability of plastic structures  12  to withstand stress-induced cracking is shown in  FIG. 30 . 
     At step  92 , an injection molding operation or other operation may be used in forming plastic structures  12 . For example, plastic such as polycarbonate, ABS, PC/ABS, or other thermoplastic materials may be injection molded into a metal mold having a shape of an electronic device housing structure for an electronic device such as electronic device  10  of  FIG. 1 . The plastic structures that are formed during the operations of step  92  may include electronic device housing walls having a thickness of less than 5 mm, less than 4 mm, less than 3 mm, less than 2 mm, less than 1 mm, or less than 0.5 mm (as examples). 
     At step  94 , equipment such as machining tool  18  of  FIG. 2 , laser cutting equipment (see, e.g., equipment  18  of  FIG. 3 ), water-jet cutting equipment such as equipment  18  of  FIG. 7 , or other equipment may be used to form opening  16  of  FIG. 18 . In forming opening  16 , stress may be imparted to wall  48 . 
     At step  96 , equipment such as equipment  18  of  FIG. 4  may be used to deposit coating layer  88  on walls  48  of opening  16 , as shown in  FIG. 28 . Layer  88  may be formed from a polymeric material (e.g., a thermoset material such as epoxy), solder paste, or other material that may form a liner when treated. 
     At step  98 , equipment  18  of  FIG. 3  may apply light, heat, or other treatment to layer  88  or other heating equipment such as heating equipment  40  may be used to apply heat to layer  88 . Following exposure to light, heat, or other treatment, the material of layer  88  may be converted into liner layer  90  of  FIG. 29 . For example, epoxy or other adhesives may cure to form liner structures  90 , solder paste may reflow to form solder-based liner structures  90 , or other changes may take place to convert coating layer  88  into a solid liner structure for opening  16  such as liner structure  90  of  FIG. 29 . Due to the presence of liner  90  on walls  48  of opening  16 , plastic structures  12  in the vicinity of opening  16  may have a reduced tendency to form stress-induced cracks. Linger structure  90  of  FIG. 29 , liner structure  80  of  FIG. 24 , and liner structure  62  of  FIG. 15  may, if desired, have a ductility that is greater than that of plastic structures  12  in walls  48 . 
     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. Any of the foregoing embodiments may be used alone or in combination with one or more of any of the other foregoing embodiments.

Metadata:
Filing Date: 20120927
Publication Date: 20190528
Grant Date: 20190528
Priority Date: 20120503
Inventors: DINH, RICHARD H.
JARVIS, DANIEL W.
Assignee: APPLE INC
CPC Classifications: [{"code": "B29L2031/3481", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/474", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29L2031/737", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/4998", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C63/34", "inventive": true, "first": true, "tree": "[]"}, {"code": "B29C2793/0018", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C2793/0018", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29L2031/737", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C63/34", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y10T29/4998", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29L2031/3481", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/474", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 49511760