PATENT DOCUMENT

Publication Number: US-9044898-B2
Application Number: US-201213438605-A
Country: US
Kind Code: B2

Title: Methods for joining electronic device housing structures using heat activated thermoset film

Abstract:
An electronic device may have electronic components enclosed within a plastic housing. The plastic housing may include housing members that are joined using heat activated thermoset polymer film. The heat activated thermoset polymer film may be heated using a metal structure such as a strip of metal that is placed along a joint between the housing members. The temperature of the metal strip and associated layers of the thermoset polymer film may be raised by applying current to the metal strip using an external tool or the electronic components within the housing. Heat activated thermoset polymer film may be heated using a reactive multilayer metal foil. Heat sink layers of metal may be interposed between the reactive multilayer metal foil and the thermoset polymer film. A heated metal ring or a heated edge portion of a plastic housing member may also be used to heat the thermoset polymer film.

Claims:
What is claimed is: 
     
       1. A method for joining plastic electronic device housing members, comprising:
 forming structures that include heat activated thermoset film and a metal layer; and 
 while the structures that include the heat activated thermoset film and the metal layer are interposed between the plastic electronic device housing members, applying current to the metal layer to raise the heat activated thermoset film to an elevated temperature, wherein the plastic electronic device housing members have edges that define a cavity, and wherein forming the structures comprises cutting the structures to form a loop that runs along at least some of the edges of the plastic electronic device housing members and surrounds the cavity. 
 
     
     
       2. The method defined in  claim 1  wherein forming the structures comprises attaching a layer of heat activated thermoset film to the metal layer. 
     
     
       3. The method defined in  claim 1  wherein cutting the structures comprises cutting the structures using a tool selected from the group consisting of: a laser and a die press. 
     
     
       4. A method for joining plastic electronic device housing members, comprising:
 forming structures that include heat activated thermoset film and a metal layer; and 
 while the structures that include the heat activated thermoset film and the metal layer are interposed between the plastic electronic device housing members, applying current to the metal layer to raise the heat activated thermoset film to an elevated temperature, wherein forming the structures comprises forming the metal layer and a layer of heat activated thermoset film on a release liner. 
 
     
     
       5. The method defined in  claim 2  wherein forming the structures comprises forming structures that include a metal layer interposed between first and second layers of heat activated thermoset film. 
     
     
       6. A method for joining plastic members, comprising:
 forming structures that include heat activated thermoset film and a metal layer; and 
 while the structures that include the heat activated thermoset film and the metal layer are interposed between the plastic members, applying current to the metal layer to raise the heat activated thermoset film to an elevated temperature, wherein the plastic members comprise electronic device housing members, the method further comprising enclosing electronic components within the electronic device housing members while applying the current. 
 
     
     
       7. The method defined in  claim 6  wherein applying the current comprises using an external tool to apply the current. 
     
     
       8. The method defined in  claim 6  wherein applying the current comprises applying the current using circuitry in the electronic components that are enclosed within the electronic device housing members. 
     
     
       9. A method of attaching first and second plastic electronic device housing members, comprising:
 heating a metal structure to an elevated temperature; and 
 while the metal structure is at the elevated temperature, compressing the metal structure and heat activated thermoset film between the first and second plastic electronic device housing members to form a joint that attaches the first and second plastic electronic device housing members, wherein the metal structure comprises a metal ring and wherein compressing the metal structure and heat activated thermoset film comprises compressing the metal ring between the first and second plastic electronic device housing members. 
 
     
     
       10. A method of attaching first and second plastic electronic device housing members, comprising:
 heating a metal structure to an elevated temperature; and 
 while the metal structure is at the elevated temperature, compressing the metal structure and heat activated thermoset film between the first and second plastic electronic device housing members to form a joint that attaches the first and second plastic electronic device housing members, wherein compressing the metal structure and heat activated thermoset film between the first and second plastic electronic device housing members comprises enclosing internal electrical components within the first and second plastic electronic device housing members while compressing the metal structure and heat activated thermoset film between the first and second plastic electronic device housing members. 
 
     
     
       11. A method for forming an electronic device, comprising:
 placing structures that include heat activated thermoset polymer and a metal structure along a joint between first and second plastic electric device housing members; and 
 attaching the first and second plastic electronic device housing members by applying current to the metal structure that raises the metal structure and the heat activated thermoset polymer to an elevated temperature, wherein attaching the first and second plastic electronic device housing members comprises enclosing electronic components within the first and second plastic housing members while applying the current to the metal structure. 
 
     
     
       12. The method defined in  claim 11  further comprising:
 generating the current using the enclosed electronic components. 
 
     
     
       13. The method defined in  claim 10  wherein the heat activated thermoset film is characterized by an activation temperature and wherein heating the metal structure comprises heating the metal structure to a temperature that is above the activation temperature and is insufficient to visibly damage the first and second plastic electronic device housing members. 
     
     
       14. The method defined in  claim 11  wherein attaching the first and second plastic electronic device housing members comprises pressing the first and second plastic electronic device housing members together while applying the current to the metal structure. 
     
     
       15. The method defined in  claim 9  wherein the heat activated thermoset film is characterized by an activation temperature and wherein heating the metal structure comprises heating the metal structure to a temperature that is above the activation temperature and is insufficient to visibly damage the first and second plastic electronic device housing members.

Description:
BACKGROUND 
     This relates generally to electronic devices, and, more particularly, to assembling housing parts for an electronic device. 
     Electronic devices may include printed circuit boards and other internal components. These components may be mounted in a housing. With some devices, it may be desirable to form the housing from mating plastic housing structures. 
     Mating housing structures can be attached to each other using screws. However, screws may be unsightly. Other techniques may therefore be used that secure plastic housing structures without visible fasteners. For example, techniques for bonding plastic housing structures together such as ultrasonic welding, adhesive, and temperature bonding film may be used to avoid visible fasteners. These techniques may, however, pose manufacturing challenges. Ultrasonic welding can be used to join mating plastic parts, but may produce inconsistent results. Adhesives can be flammable. Temperature bonding film (TBF), which is a low melting temperature thermoplastic polymer, may become weakened when an electronic device is operated at elevated temperatures. 
     It would therefore be desirable to be able to provide improved ways in which to join plastic structures for electronic devices. 
     SUMMARY 
     An electronic device may have electronic components enclosed within a plastic housing. The electronic device may include a power converter circuit or other circuitry. 
     The plastic housing may include first and second mating housing members. The housing may be formed by joining edge portions of the first and second mating housing members. 
     The housing members may be joined using heat activated thermoset polymer film. Heat activated thermoset polymer material may be heated using a metal structure such as a strip of metal that is placed along the joint between the housing members. The temperature of the metal strip and associated layers of the heat activated thermoset film may be elevated by applying current to the metal strip using an external tool or by applying current to the metal strip using the electronic components within the housing. Heat activated thermoset polymer film may be heated using a reactive multilayer metal foil. Metal heat sink layers may be interposed between the reactive multilayer metal foil and the heat activated thermoset polymer film. A heated metal ring or a heated edge portion of a plastic housing member may also be used to heat the thermoset polymer film. 
     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 perspective view of an illustrative electronic device of the type that may have multiple mating housing structures in accordance with an embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of the illustrative electronic device of  FIG. 1  showing how the electronic device may have left and right housing members that are joined along a seam and that enclose internal device components in accordance with an embodiment of the present invention. 
         FIG. 3  is a diagram showing how housing structures of the type shown in  FIGS. 1 and 2  may be joined with a heat activated thermoset film in accordance with an embodiment of the present invention. 
         FIG. 4  is a cross-sectional side view of a joint between two opposing housing members before heating of a heating element to elevate the temperature of a heat activated thermoset film in accordance with an embodiment of the present invention. 
         FIG. 5  is a cross-sectional side view of the joint between the two opposing housing members of  FIG. 4  following heating of the heating element to elevate the temperature of the heat activated thermoset film in accordance with an embodiment of the present invention. 
         FIG. 6  is a cross-sectional side view of a joint between two opposing housing members showing how the joint may have an angled portion in accordance with an embodiment of the present invention. 
         FIG. 7  is a cross-sectional side view of a joint between two opposing housing members showing how the edges of the housing members may have mating engagement features such as a protrusion and associated recess in accordance with an embodiment of the present invention. 
         FIG. 8  is a cross-sectional view of the illustrative electronic device of  FIG. 1  showing how internal device circuitry may be used in applying current to a heating element to elevate the temperature of heat activated thermoset film along the joint between first and second housing members in accordance with an embodiment of the present invention. 
         FIG. 9  is a cross-sectional view of a joint between opposing housing members showing how a reactive multilayer foil may be used to elevate the temperature of heat activated thermoset film along the joint in accordance with an embodiment of the present invention. 
         FIG. 10  is a cross-sectional diagram showing how a heat source may heat a ring of metal or other structure for use in elevating the temperature of heat activated thermoset film along a joint between opposing housing members in accordance with an embodiment of the present invention. 
         FIG. 11  is a cross-sectional side view of opposing housing members in the vicinity of a joint that has not yet been formed showing how a ring of metal or other structure that has been heated may be placed between layers of heat activated thermoset film for forming a bond along the joint in accordance with an embodiment of the present invention. 
         FIG. 12  is a cross-sectional side view of the opposing housing members of  FIG. 11  after being attached to each other using heat activated thermoset film and a heated member such as a ring-shaped strip of metal in accordance with an embodiment of the present invention. 
         FIG. 13  is a cross-sectional side view of a housing member showing how an edge portion of the housing member may be raised to an elevated temperature using a heat source in accordance with an embodiment of the present invention. 
         FIG. 14  is a cross-sectional side view of a pair of opposing housing members including the housing member of  FIG. 13  showing how the elevated temperature of the housing member may be used to activate a heat activated thermoset film for attaching the housing members to each other in accordance with an embodiment of the present invention. 
         FIG. 15  is a flow chart of illustrative steps involved in attaching housing members to each other to form an electronic device housing or other electronic device structure in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may include polymer structures such as plastic housing structures. These structures may be joined using ultrasonic welding, adhesives, temperature bonding film (e.g., heat activated thermoplastic film), or heat activated thermoset film. Ultrasonic welding may leave visible artifacts along a joined seam. Adhesives may be flammable and therefore may be undesirable when used in products that operate at an elevated temperature. Thermoplastic polymers may become weakened when raised to an elevated temperature during operation of an electronic device. 
     To overcome these challenges, at least some of the polymer structures in an electronic device such as plastic housing structures may be joined using thermoset polymers. Thermoset polymers may be raised to an elevated temperature to allow the polymer material to soften and form a bond with other polymers. Unlike thermoplastic polymers, which can become soft if returned to an elevated temperature during use, thermoset polymers are generally heat resistant after they have been returned to room temperature following bonding. It may therefore be advantageous to use thermoset polymers such as heat activated thermoset films when forming bonds between respective plastic housing structures. 
     To form a polymer bond that attaches plastic housing portions to each other, heat activated thermoset polymer material can be raised to a temperature that is above the activation temperature of the thermoset polymer material (e.g., a temperature in the range of about 160-220° C.), while being sufficiently low to avoid damaging the plastic housing portions (i.e., by eliminating or at least minimizing heating of the plastic housing significantly above the glass transition temperature of the plastic housing and thereby avoiding visible damage to the plastic housing). To ensure that heat-induced artifacts such as plastic discoloration are not visible from the exterior of device  10 , heat may be generated from within the joint that is formed where opposing edges of the plastic housing portions meet each other. 
     An illustrative electronic device of the type that may have plastic structures that are joined using heat activated thermoplastic film is shown in  FIG. 1 . As shown in  FIG. 1 , electronic device  10  may have a housing such as housing  12 . Housing  12  may have multiple structures such as housing member  12 A and housing member  12 B. Members  12 A and  12 B may be, for example, mating housing halves for a clamshell enclosure. If desired, more than two housing members may be attached to one another to form housing  12 . The use of two opposing housing members such as housing members  12 A and  12 B of  FIG. 1  is merely illustrative. 
     Device  10  may have a portion such as portion  14  that contains a plug configured to plug into an alternating current (AC) wall outlet. The interior of device  10  may contain alternating current to direct current (DC) power converter circuitry (AC/DC power converter circuitry) for converting AC power from the wall outlet into DC power. Cable  16  may be used to route DC power to an associated device such as a tablet computer, a laptop computer, a desktop computer, a cellular telephone, a media player, a display, a display that includes a computer, a television set-top box, a wireless router, a television, or other electronic equipment. If desired, device  10  may be a computer, telephone, media player, or other electronic equipment. The example of  FIG. 1  is merely illustrative. 
     Housing members  12 A and  12 B may be joined along a seam such as joint  18  using a thermoset material such as a heat activated thermoset film. A cross-sectional side view of device  10  of  FIG. 1  taken along line  20  and viewed in direction  22  is shown in  FIG. 2 . As shown in  FIG. 2 , housing members  12 A and  12 B may be joined along joint  18  to form a cavity that encloses internal components  24 . Components  24  may include integrated circuits, discrete components such as resistors, inductors, and capacitors, switches, connectors, and other circuitry. The circuitry of components  24  may be used to perform functions such as alternating current (AC) to direct current (DC) power conversion (as an example). Components such as components  24  may be mounted on one or more substrates such as rigid printed circuit boards (e.g., fiberglass-filled epoxy boards), flexible printed circuits formed from sheets of polyimide or other flexible polymer layers, dielectric support structures such as structures formed from plastic, glass, ceramic, or other suitable substrate materials. Conductive traces (e.g., metal lines) may be used in interconnecting the circuitry of components  24 . 
     A diagram showing equipment and operations involved in assembling electronic device  10  using heat activated thermoset film is shown in  FIG. 3 . 
     Initially, coating equipment  27  may be used to deposit a layer of material to form heat activated thermoset film  29  on release liner  26 . Release liner  26  may be a sheet of release liner material such as a sheet of silicone or other polymer (e.g., polyamide, polyethylene terephthalate, polyethylene, polycarbonate, polymethylmethacrylate, etc.), paper, or other materials. Coating equipment  27  may, for example, receive a liquid precursor for film  29  and may contain spraying equipment, rolling equipment, or other equipment for depositing the liquid onto the surface of release liner  26 . Heat treatment may be used to cure the deposited material to form film  29 . Once cured, film  29  may be solid at room temperature. 
     Following formation of layer  29  on release liner  26 , coating equipment  28  may be used to form conductive material layer  30  on layer  29 . Coating equipment  28  may be a tool such as roller equipment for rolling a layer of conductive metal (e.g., conductive foil) onto the top of layer  29 . If desired, coating equipment  28  may form other conductive materials (e.g., conductive polymers, metal silicides, etc.) on the surface of layer  29 . The conductive material may be in sheet form (e.g., aluminum foil or copper foil) or may be a foil or structure that is used as a substrate for the heat activated thermoset film. The use of roller-based equipment to attach a sheet of metal to form conductive metal layer  30  is merely illustrative. 
     Following the formation of metal layer  30  on heat activated thermoset film  29 , coating equipment  32  (e.g., equipment such as equipment  27 ) may be used to deposit and cure a layer of material to form heat activated thermoset film  34 . 
     Films  34  and  29  may be characterized by an activation temperature of about 120° C. to 130° C. (or, if desired, about 100-150° C.). Housing members  12 A and  12 B may be formed from a polymer or other material that has the ability to remain solid at temperatures above the activation temperature of film  34  (e.g., housing members  12 A and  12 B may be characterized by a glass transition temperature above 150° C.). Housing members  12 A and  12 B may, as an example, be formed from a polymer such as polycarbonate (PC), acrylonitrile butadiene styrene (ABS), or a PC/ABS plastic blend. 
     During the process of forming film  34  on layer  30 , film  34  may be patterned to form coated areas such as area  36  and uncoated areas such as uncoated area  38 . 
     After forming layer  34  on layer  30  to form heat activated thermoset film structures  39 , cutting tool  40  may be used to cut structures  39 . Cutting tool  40  may, for example, include die cutting equipment such as a die press or laser cutting equipment such as computer-positioned laser cutting equipment that can pattern structures  39  to form a loop of heat activated thermoset film. Patterned heat activated thermoset film structures  42  may, for example, include a portion such as ring shaped (loop shaped) portion  44  in which layer  34  coats conductive layer  30  and may have a portion such as terminals  46  and  48  in which conductive layer  30  is uncoated by heat activated thermoset film  34 . 
     Assembly tools  50  may be used to attach structures  42  to device housing structures  52  such as structures  12 A and  12 B. For example, tools  50  may include robotic positioning equipment or other equipment for placing loop  44  of heat activated thermoset film structures  42  face down on the edge of member  12 A and peeling away release liner  26  so that layers  29 ,  30 , and  34  remain in place on the edge of member  12 A. In this configuration, the strip of material that makes up loop  44  runs along the edges of housing members  12 A and  12 B. Assembly tools  50  may include a press or other equipment for pressing and holding member  12 B in position on mating housing member  12 A (e.g., so that layers  29 ,  30 , and  34  are held between opposing mating edges of members  12 A and  12 B along joint  18 ). 
     Assembly tools  50  may also include a power supply for contacting terminals  46  and  48  (e.g., power supply equipment that is external to housing  12 ). Once electrical contacts have been formed with terminals  46  and  48 , the power supply may supply current through loop  44  of structures  42 . Film  30  may be formed with a sufficiently small thickness T (e.g., 100 microns or less or 1 micron or less as examples) to allow film  30  to serve as an Ohmic heating element. As current passes through film  30  in loop  44  from the power supply, film  30  will heat due to Ohmic heating. This will cause adjacent heat activated thermoset films  29  and  34  in loop  44  to form a bond between member  12 A and  12 B along joint  18 . Internal electrical components  24  may be sealed within the cavity formed by members  12 A and  12 B during the use of tools  50  to form finished electronic device  10 . 
     If desired, heat may be applied using electromagnetic induction. With this type of arrangement, power supply  50  may include a radio-frequency signal generator that produces radio-frequency electromagnetic signals at a given frequency. Structure  44  may be implemented in the form of a metal loop, a metal strip, or other conductive structure that is configured to exhibit a resonance at the given frequency (i.e., a structure having a size and shape that exhibits an electromagnetic coupling resonance at the given frequency). When radio-frequency wireless signals are supplied by equipment  50  at the given frequency, the electromagnetically coupled structures will rise in temperature, thereby heating adjacent heat activated thermoset films  29  and  34 . 
       FIG. 4  is a cross-sectional view of joint  18  before application of heat to layers  29  and  34 . As shown in  FIG. 4 , layers  29 ,  30 , and  34  may form a strip of material that runs along joint  18 . The strip of material that forms conductive layer  30  may serve as an Ohmic heating element. When current is applied to conductive strip  30 , heat will flow to adjacent layers  29  and  34  of heat activated thermoset film. This will raise the temperature of the heat activated thermoset film above its activation temperature, while maintaining adjacent portions of members  12 A and  12 B such as portions  54  and  56  at temperatures below the glass transition temperature of the polymer material used to form members  12 A and  12 B. Elevation of the temperature of heat activated thermoset film  29  and  34  will cause the material of layers  29  and  34  to bond with members  12 A and  12 B and therefore securely join members  12 A and  12 B to each other along joint  18 , as illustrated in  FIG. 5 . Dashed lines  34 ′ and  29 ′ in  FIG. 5  show where heat activated thermoset material may bond with the material of members  12 A and  12 B. As shown in  FIG. 5 , conductive material  30  may remain in place within housing  12  following the joining of members  12 A and  12 B to each other. 
     As shown in  FIG. 6 , the opposing surfaces of members  12 A and  12 B that are associated with joint  18  need not be uniformly planar. For example, these surfaces may be configured so that joint  18  is characterized by a first planar portion such as portion  58  and a second planar portion such as portion  60 . Portions  58  and  60  may be coupled at an angle (bent portion  62 ). As shown in the illustrative configuration of  FIG. 7 , members  12 A and  12 B may have interlocking engagement features. For example, member  12 A may have a protruding portion such as protrusion  66  and member  12  may have a corresponding recessed portion such as recess  64 . The surfaces that form engagement features  64  and  66  may have flat portions, curved portions, combinations of planar and non-planar surfaces, or other suitable shapes for interlocking members  12 A and  12 B. The configuration of  FIG. 7  is merely illustrative. 
     During bonding of housing members  12 A and  12 B using thermoset films  29  and  34 , exposed surfaces such as exterior cosmetic surfaces  19  of housing  12  in  FIGS. 6 and 7  may remain visibly undamaged by avoiding or at least minimizing the application of heat to surfaces  19  (e.g., by applying heat through structure  30 , etc., without using external tools to heat members  12 A and  12 B through surfaces  19 ). 
       FIG. 8  is a cross-sectional view of device  10  of  FIG. 1  taken along line  68  (i.e., along joint  18 ) and viewed in direction  70 . As shown in  FIG. 8 , heat activated thermoset film structures  42  may be placed along the edge of the housing walls in housing  12  (e.g., along the opposing edges of members  12 A and  12 B). In this configuration, loop portion  44  of structures  42  may be used in joining members  12 A and  12 B together. 
     Current may be applied to layer  30  of structures  42  using external equipment such as tools  50  of  FIG. 3  (e.g., using outwardly protruding terminals  46  and  48 ). As shown in the illustrative configuration of  FIG. 8 , terminals  46  and  48  may, if desired, be coupled to internal device circuitry. Internal components  24  such as integrated circuits, discrete components, and other circuitry may be mounted on a substrate such as substrate  72 . Substrate  72  may be, for example, a printed circuit board. Device  10  may have an alternating current (AC) wall plug such as plug  84  that mates with a source of power such as a wall outlet (e.g., power source  86 ). Using paths such as path  82 , power may be distributed from power source  86  to internal components  24 . 
     Terminal  46  of heat activated thermoset structures  42  may be coupled to components  24  at node  74  using conductive paths such as path  76 . Terminal  48  of heat activated thermoset structures  42  may be coupled to components  32  at node  78  using conductive paths such as path  80 . Components  24  may be used to implement control circuitry for device  10 . During manufacturing operations, the control circuitry can use power from source  86  to apply a current to structures  42 . The current that flows through conductive layer  30  of structures  42  may elevate the temperature of layer  30  and the heat activated thermoset material in structures  42  sufficiently to activate the thermoset material and thereby attach members  12 A and  12 B along joint  18 . Access to the functionality of circuitry  24  that permits Ohmic heating of layer  30  may be selectively enabled during manufacturing operations. Fro example, access to the ability to apply current to layer  30  may be secured using digital authentication, using software that is loaded and run on circuitry  24  only during manufacturing operations, or using other schemes to prevent inadvertent heating of layer  30  following manufacturing. 
     If desired, heat activated thermoset film layers  29  and  34  may be heated using a reactive multilayer foil such as foil  92  of  FIG. 9 . Foil  92  may include multiple layers of exothermically reacting materials such as alternating layers of metal. As an example, foil  92  may include alternating layers of aluminum and nickel or alternating layers of aluminum and titanium. 
     When it is desired to produce heat to form joint  18 , an initiating electrical pulse may be applied to reactive multilayer foil  92 . Once an exothermic reaction has been initiated in foil  92 , the layers of foil  92  will react with each other and will produce heat. The heat from the foil may be used to elevate the temperature of heat activated thermoset film layers  29  and  34 . If desired, optional layers such as layer  90  may be interposed between foil  92  and heat activated thermoset film layers  29  and  34 . Layers  90  may be formed from a material such as metal or other materials that can serve as a heat sink for the heat generated by reactive multilayer foil structure  92 . Use of this heat sink may help ensure that the heat generated by reactive multilayer foil structure  92  does not burn or otherwise damage heat activated thermoset film layers  29  and (i.e., the heat sink may help prevent an overly rapid rise in temperature and may help sustain an elevated temperature for an amount of time that is sufficient to activate heat activated thermoset film layers  29  and  34 ). As an example, reactive multilayer foil  92  may generate heat in a relatively short time period. Using heat sink layers  90 , the heat that is generated by foil  92  may remain elevated above the activation temperature of heat activated thermoset film layers  29  and  34  for a more extended amount of time. If desired, a reactive process may be used that exhibits heat generation over other time periods (e.g., 1-500 ms, more than 50 ms, more than 500 ms, 0.1 to is or more, etc.). The structures of  FIG. 9  such as heat activated thermoset film  29  and  34 , heat sink layers  90 , and reactive multilayer foil  92  may be formed in a ring shape or other suitable shape that runs along the opposing edges of housing members  12 A and  12 B to form joint  18 . 
     If desired, heat may be applied to heat activated thermoset film using a heated member such as a heated metal ring. This type of arrangement is shown in  FIG. 10 . As shown in  FIG. 10 , metal ring  94  may initially be at room temperature. Using heating tool  96 , the temperature of metal ring  94  may be elevated (e.g., to a temperature above the activation temperature of heat activated thermoset film  29  and  34  and below the glass transition temperature of housing members  12 A and  12 B). Heating tool  96  may be, for example, an oven, a laser, a heated plate, or other heating equipment. 
     As shown in  FIG. 11 , heated metal structure  94  may be placed between opposing edges of members  12 A and  12 B with heat activated thermoset film layers  29  and  34 . Members  12 A and  12 B may then be moved towards each other in directions  98  and  100 . When heat activated thermoset film layers  29  and  34  contact heated metal ring  94 , member  12 A and member  12 B may be attached to each other along joint  18 , as shown in  FIG. 12 . The thermoset material of layers  34  and  29  may form attachment layers that attach metal ring  94  to members  12 B and  12 A, respectively, as shown by dashed lines  102  and  104 . 
       FIG. 13  shows how lower edge portion  106  of member  12 B may be heated using heat source  107 . Heat source  107  may be a laser, heated plate, or other heating source. When heated by heat source  107  as shown in  FIG. 18 , lower portion  106  of housing member  12 B may be raised to a temperature that is below the glass transition temperature of the material that forms member  12  and that is above the activation temperature of heat activated thermoset film material. As shown in  FIG. 14 , members  12 A and  12 B may be pressed together to compress heat activated thermoset film  34  while region  106  is still at its elevated temperature. The heat from region  106  may then be transferred from region  106  to film  34 , to form joint  18 . 
     Illustrative steps involved in using heat activated thermoset films such as films  29  and  34  to join structures such as housing members  12 A and  12 B together are shown in  FIG. 15 . 
     At step  108 , heat actuated thermoset film layers such as layers  29  and  34  may be assembled with other structures along the edges of members  12 A and  12 B that are to be joined. During the operations of step  108 , material may be included in the region between members  12 A and  12 B to heat the heat actuated thermoset film layers. For example, a layer of metal such as metal  30  may be included to form an Ohmic heating element or a reactive metal foil and optional heat sinks may be included in configurations in which heat is to be generated using an exothermic reaction. 
     At step  110 , heat may be applied to elevate the temperature of the heat activated thermoset film and thereby activate the heat activated thermoset film. When applying heat, internal electronic components  24  may be enclosed within the cavity formed inside mating electronic device housing members  12 A and  12 B. Heat may be applied to the heat activated thermoset film by applying current to an Ohmic heating element with an external tool, by using circuitry in the internal electrical components, by triggering an exothermic reaction in a reactive multilayer foil structure, by applying heat to the film from a heated metal ring, by heating a portion of members  12 A and/or  12 B using a heat source prior to pressing members  12 A and  12 B against the heat activated thermoset film, by applying electromagnetic energy (radio-frequency signals) wirelessly that are inductively coupled to a metal ring, strip, or other resonant structure (e.g., a structure such as structure  44  of  FIG. 3  in a loop shape or other shape), or by using any other suitable heat application technique. These techniques may be used to apply heat internally within joint  18 , rather than externally through the exterior walls of housing members  12 A and  12 B, thereby minimizing the potential for damage to the exposed surfaces of members  12 A and  12 B from excessive heat exposure. 
     At step  112 , following formation of housing  12  for device  10  by joining housing members  12 A and  12 B along joint  18  using heat activated thermoset film, final device manufacturing operations may be performed (e.g., to trim excess material, to apply a desired surface finish, etc.). 
     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.

Metadata:
Filing Date: 20120403
Publication Date: 20150602
Grant Date: 20150602
Priority Date: 20120403
Inventors: LOZANO VILLARREAL CESAR
Assignee: APPLE INC
CPC Classifications: [{"code": "H05K5/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/91655", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/3468", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/02", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/1224", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/12463", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K13/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/348", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/3444", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29L2031/3481", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/91431", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/1226", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/3476", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/4835", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/919", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/20", "inventive": true, "first": true, "tree": "[]"}, {"code": "B29C65/5057", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K5/0004", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/54", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T156/1052", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/1142", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/91411", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/12443", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/91945", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/83221", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/20", "inventive": true, "first": true, "tree": "[]"}, {"code": "B29C65/20", "inventive": true, "first": true, "tree": "[]"}, {"code": "B29L2031/3481", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/3444", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/3468", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/348", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/4835", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/5057", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/1142", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/1226", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/12443", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/12463", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/54", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/1224", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/91411", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/3476", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/91945", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/91431", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/91655", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/919", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/83221", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/73921", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/71", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/72321", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/022", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T156/1052", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T156/1052", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/83221", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29L2031/3481", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/3444", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/3468", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/348", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/4835", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/5057", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/1142", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/1226", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/12443", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/12463", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/54", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/1224", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/91411", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/3476", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/91945", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/91431", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/91655", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/919", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/73921", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/71", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/72321", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/022", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 49233290