PATENT DOCUMENT

Publication Number: US-8766099-B2
Application Number: US-56987109-A
Country: US
Kind Code: B2

Title: Component mounting structures for electronic devices

Abstract:
Sensitive electronic components can be mounted on a printed circuit board within an electronic device. To isolate a sensitive component from stresses that may arise during an unintended impact event, the electronic component can be isolated using a groove in the printed circuit board. The electronic component may be mounted to a component mounting region using solder balls. The component mounting region may be surrounded on some or all sides by the groove. Flex circuit structures that bridge the groove or a portion of the rigid printed circuit board may be used to hold the component mounting region in place. The flex circuit structures may be provided in the form of separate structures or may be provided as an integral portion of the printed circuit board.

Claims:
What is claimed is: 
     
       1. Component mounting structures for mounting an electronic component in an electronic device, comprising:
 a rigid printed circuit board, wherein the rigid printed circuit board comprises a component mounting region on which the electronic component is mounted; 
 a first opening in the printed circuit board that at least partly surrounds the component mounting region, wherein the rigid printed circuit board comprises a given rigid region that at least partly surrounds the first opening; 
 a second opening in the printed circuit board that at least partly surrounds the given rigid region, wherein there is only a first rigid portion of the rigid printed circuit board that extends between the component mounting region and the given rigid region and wherein there is only a second rigid portion of the rigid printed circuit board that extends between the given rigid region and the rigid printed circuit board. 
 
     
     
       2. The component mounting structures defined in  claim 1  wherein the first rigid portion of the rigid printed circuit board that extends between the component mounting region and the given rigid region is located on a different side of the component mounting region than the second rigid portion of the rigid printed circuit board that extends between the given rigid region and the rigid printed circuit board. 
     
     
       3. The component mounting structures defined in  claim 1  wherein the first opening comprises a contiguous opening that together with the first rigid portion completely surrounds the component mounting region and wherein the second opening comprises a contiguous opening that together with the second rigid portion completely surrounds the given rigid region. 
     
     
       4. The component mounting structures defined in  claim 1 , further comprising:
 a conductive trace that extends from the rigid printed circuit board, over the second rigid portion of the rigid printed circuit board that extends between the given rigid region and the rigid printed circuit board, over the first rigid portion of the rigid printed circuit board that extends between the component mounting region and the given rigid region, and onto the component mounting region. 
 
     
     
       5. Mounting structures for mounting an electronic component, comprising:
 a printed circuit board having a hole that extends through the printed circuit board; 
 a component mounting region within the hole, wherein the component mounting region comprises a rigid board portion; and 
 a flex circuit structure that connects the component mounting region to the printed circuit board, wherein the printed circuit board includes a rigid upper layer and a rigid lower layer, wherein at least a first portion of the flex circuit structure is sandwiched between the rigid upper layer and the rigid lower layer, wherein the component mounting region comprises a rigid upper printed circuit board layer portion and a rigid lower printed circuit board layer portion, and wherein at least a second portion of the flex circuit structure is sandwiched between the rigid upper printed circuit board layer portion and the rigid lower printed circuit board layer portion. 
 
     
     
       6. The mounting structures defined in  claim 5  wherein the component mounting region comprises a rectangular rigid printed circuit board region. 
     
     
       7. The mounting structures defined in  claim 5  wherein the component mounting region comprises a flex circuit region. 
     
     
       8. The mounting structures defined in  claim 5  wherein the component mounting region and the flex circuit structure are both integral parts of a rigid flex structure.

Description:
BACKGROUND 
     This relates to electronic devices, and more particularly, to electronic devices with component mounting structures that help the electronic devices withstand damage when subjected to stress. 
     Electronic devices such as computers, media players, and cellular telephones typically contain electronic components. For example, a handheld electronic device might contain an accelerometer module that is used in determining the orientation of the handheld electronic device with respect to ground (e.g., whether the device is in landscape or portrait mode). Accelerometers and other electronic components such as integrated circuits, microphones, speakers, status indicators, and connectors for input-output ports, are typically mounted on printed circuit boards. Conductive traces on the printed circuit boards are used to route signals between the components. 
     Components are often mounted to printed circuit boards using solder balls. For example, a “flip-chip” arrangement may be used to mount an integrated circuit to a printed circuit board. With this type of configuration, an array of solder bumps is interposed between the integrated circuit and the printed circuit board. The solder bumps serve to electrically connect the circuitry of the integrated circuit to the printed circuit board. The solder bumps also serve to physically attach the integrated circuit to the printed circuit board. Components such as accelerometers may also be mounted in this way. 
     Electronic devices and the electrical components within these devices are sometimes exposed to large stresses. For example, a user of a device may inadvertently drop the device on the ground. When the device strikes the ground, the printed circuit board and the components mounted to the printed circuit board are subjected to stress. If the stress is too great, components may become partly or fully detached from the printed circuit board or may become damaged due to internal stresses. 
     One way in which to enhance the robustness of a typical solder ball component mounting scheme involves the use of epoxy underfill. During manufacturing, liquid epoxy is introduced into the gap between a component and the printed circuit board to which the component is mounted. Capillary action draws the epoxy between the component and the printed circuit board. The epoxy is then cured, which helps stabilize the mounted component and prevent inadvertent detachment of the component during a drop event. 
     Underfill arrangements are often satisfactory when mounting robust components to a printed circuit board. However, underfill arrangements are not satisfactory for use with sensitive components such as accelerometers. When components such as these are underfilled, the presence of the underfill disrupts proper operation of the component. Proper operation can be ensured by omitting the underfill when mounting the components, but this tends to increase the risk of component failure during a drop event. 
     It would therefore be desirable to be able to provide electronic devices with improve component mounting structures. 
     SUMMARY 
     An electronic device may have a housing. One or more printed circuit boards may be mounted within the housing. Components may be mounted on the printed circuit board using solder balls. For example, sensitive electronic components such as accelerometers may be mounted to a component mounting region using solder balls. The component mounting region may be separated from other portions of the printed circuit board using an isolating groove. The groove may be formed from an air-filled opening in the printed circuit board. The groove may surround all or part of the component mounting region. 
     To form electrical connections between the component that is mounted to the component mounting region and other circuitry on the printed circuit board, traces may be formed on a portion of the printed circuit board that connects the component mounting region to the rest of the printed circuit board. Flex circuit and rigid flex arrangements may also be used to interconnect the component mounting region to the printed circuit board. If desired, a flex circuit layer may be sandwiched between patterned layers of rigid printed circuit board material to form an integral mounting structure. 
     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 cross-sectional side view of a conventional printed circuit board on which a component has been mounted and underfilled with epoxy. 
         FIG. 2  is a perspective view of an illustrative electronic device that may include a component mounting structure in accordance with an embodiment of the present invention. 
         FIG. 3  is a cross-sectional side view of an illustrative electronic device showing how an accelerometer and other components may be mounted on a substrate such as a printed circuit board within the electronic device in accordance with an embodiment of the present invention. 
         FIG. 4  is a perspective view of an illustrative printed circuit board with an isolation groove surrounding a component on the board in accordance with an embodiment of the present invention. 
         FIG. 5  is a top view of an illustrative printed circuit board with a pair of isolation grooves for isolating a component on the board in accordance with an embodiment of the present invention. 
         FIG. 6  is a top view of an illustrative printed circuit board with an L-shaped isolation groove for isolating a component on the board in accordance with an embodiment of the present invention. 
         FIG. 7  is a top view of an illustrative printed circuit board with a U-shaped isolation groove for isolating a component that is substantially surrounded by the groove in accordance with an embodiment of the present invention. 
         FIG. 8  is a top view of an illustrative printed circuit board with a curved isolation groove for isolating a component on a printed circuit board in accordance with an embodiment of the present invention. 
         FIG. 9  is a top view of an illustrative printed circuit board in which multiple components have been provided with isolation using a groove in the printed circuit board in accordance with an embodiment of the present invention. 
         FIG. 10  is a top view of an illustrative printed circuit board in which a component has been isolated by multiple concentric grooves in the printed circuit board in accordance with an embodiment of the present invention. 
         FIG. 11  is a top view of an illustrative printed circuit board in which component isolation has been provided using grooves surrounding printed circuit board mounting posts and a groove adjacent to a mounted component on the printed circuit board in accordance with an embodiment of the present invention. 
         FIG. 12  is a top view of an illustrative component isolation arrangement in which a component that has been mounted on a printed circuit board is isolated using a groove formed in the printed circuit board and using a rigid ring-shaped stiffening structure on the surface of the printed circuit board in accordance with an embodiment of the present invention. 
         FIG. 13  is a cross-sectional side view of an illustrative component isolation arrangement of the type shown in  FIG. 12  in which a component that has been mounted on a printed circuit board is isolated using a groove formed in the printed circuit board and using a rigid ring-shaped stiffening structure on the surface of the printed circuit board in accordance with an embodiment of the present invention. 
         FIG. 14  is a perspective view of an illustrative component mounted within a hole in a printed circuit board using a rigid flex structure in accordance with an embodiment of the present invention. 
         FIG. 15  is a cross-sectional side view of an illustrative component of the type shown in  FIG. 14  mounted within a hole in a printed circuit board using a rigid flex structure in accordance with an embodiment of the present invention. 
         FIG. 16  is a cross-sectional side view of an illustrative component mounted within a hole in a printed circuit board using a flex circuit that bridges the hole in accordance with an embodiment of the present invention. 
         FIG. 17A  is a perspective view of an illustrative component on a printed circuit board showing how the component may be isolated using a groove in the circuit board and showing how conductive traces on the circuit board may be routed to the component through a gap between opposing portions of the groove in accordance with an embodiment of the present invention. 
         FIG. 17B  is a cross-sectional side view of an illustrative component mounted on a portion of a printed circuit board using solder balls in accordance with an embodiment of the present invention. 
         FIG. 18  is a perspective view of an illustrative component on a printed circuit board showing how the component may be isolated using a groove in the circuit board and showing how conductive wire-bond wires may be used to form electrical connections from the component to traces on the circuit board that are routed through a gap in the groove in accordance with an embodiment of the present invention. 
         FIG. 19  is a perspective view of an illustrative component on a printed circuit board showing how the component may be isolated using a groove in the circuit board and showing how a flex circuit may be used to form electrical connections from the component to traces on the circuit board in accordance with an embodiment of the present invention. 
         FIG. 20  is a perspective view of an illustrative printed circuit board with a hole in which a component has been mounted using a rigid flex structure having multiple flexible tails that extend into the printed circuit board in accordance with an embodiment of the present invention. 
         FIG. 21  is a cross-sectional side view of a component mounted in a hole in a printed circuit board using an arrangement of the type shown in  FIG. 20  in accordance with an embodiment of the present invention. 
         FIG. 22  is an exploded perspective view showing how component mounting structures of the type shown in  FIGS. 20 and 21  can be formed from patterned layers of rigid and flexible printed circuit boards in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices often contain one or more printed circuit boards. For example, an electronic device may include one or more rigid printed circuit boards and one or more flexible printed circuit boards. Rigid printed circuit boards are formed using rigid printed circuit board substrates such as fiberglass-filled epoxy. Flexible printed circuit boards (“flex circuits”) are formed using flexible printed circuit board substrates such as substrates based on thin flexible polymer films. A typical flex circuit substrate material is polyimide. Hybrid boards of “rigid flex” are also sometimes used. A printed circuit board that is formed from rigid flex has both flexible and rigid portions. The flexible portions are formed from flex circuit. The rigid portions are formed from the same flex circuit, but include additional rigid printed circuit board layers. 
     Printed circuit boards contain patterned conductive traces formed from copper or other conductive materials. The conductive traces can be used as data signal and power wires for electrical components that are mounted to the printed circuit boards. 
     In a typical electronic device, for example, a circuit board may be used to mount a microprocessor, a memory chip, audio chips, communications circuits, application-specific integrated circuits, digital signal processing circuits, power management circuits, and other integrated circuits. Discrete components such as resistors, inductors, and capacitors can also be mounted on the printed circuit board. Microphones, speakers, light-emitting diodes, and sensors such as light and pressure sensors are additional examples of components that may be mounted on a printed circuit board. To facilitate connections with other boards in the device and peripheral components, connectors may be mounted on a printed circuit board. Non-electrical features such as plastic posts can be mounted to the board among the electrical components. 
     Some components on a printed circuit board are relatively robust. For example, a connector may be formed from a metal part such as a stainless steel bracket. The bracket and other portions of the connector may be formed from sturdy materials that can withstand the forces typically associated with use of the connector. 
     Other components on a printed circuit board may be sensitive. An example of a sensitive component is an accelerometer formed using microelectromechanical systems (MEMS) technology. An accelerometer is sometimes used to detect the orientation of an electronic device. For example, an accelerometer may be used to measure the direction of the earth&#39;s gravity and thereby determine which direction is “up” relative to the surface of the earth. Accelerometers are considered “sensitive” because accelerometers will not produce accurate results in the presence of excessive stress. Care must therefore be taken when mounting an accelerometer on a printed circuit board. 
     Accelerometers and other MEMS components are generally mounted in packages. A typical package may have a rectangular (box) shape and may have exposed pads on its underside. These pads may be connected to traces on a printed circuit board using solder balls. Component mounting arrangements that rely solely on solder balls may not be sufficiently robust to withstand the stresses that are encountered during normal use of an electronic device. For example, a user of an electronic device may inadvertently drop the electronic device. Drop events and other abrupt stress-inducing events can dislodge weakly mounted components from printed circuit boards, leading to undesired failures. 
     To help stabilize component packages on printed circuit boards and thereby enhance the ability of the components to withstand stresses, components are often stabilized using an underfill process. A conventional underfill arrangement is shown in  FIG. 1 . As shown in  FIG. 1 , component  10  may be mounted on printed circuit board  12  using solder balls  14 . Component  10  may be, for example, an integrated circuit. To enhance the robustness of the mounting arrangement, epoxy  16  may be introduced around the periphery of component  10 . Through capillary action, the epoxy may wick into the gap between the underside of component  10  and the upper surface of printed circuit board  12 . Following curing, this epoxy will form a strong bond that will help hold component  10  on circuit board  12 . 
     Although conventional underfill arrangements of the type shown in  FIG. 1  are satisfactory for mounting integrated circuits to printed circuit boards, difficulties arise when mounting sensitive components such as accelerometers. This is because the underfill process itself introduces stresses that can cause the accelerometer to perform poorly. 
     This problem with conventional underfill arrangements can be addressed using component isolation structures based on the formation of one or more grooves in a printed circuit board. These grooves, which are also sometimes referred to as channels, holes, or air-filled openings, can be used to reduce the amount of stress that is transferred from an electronic device housing to the portion of the circuit board on which the accelerometer or other component is mounted. With this type of isolation scheme, stresses that arise from inadvertent drop events are attenuated before they affect the component. Because the amount of stress that is transmitted to the component during a drop event or other impact event is reduced, the need to underfill the component is eliminated or reduced. 
     Component mounting structures with isolation features may be formed on any suitable type of printed circuit board. Most typically, at least some of the printed circuit board is formed from a rigid substrate. Examples in which rigid printed circuit substrates are provided with isolation grooves are therefore sometimes described as an example. This is, however, merely illustrative. Isolation structures may be formed in any suitable substrate. Moreover, the type of component that is isolated using the isolation structures need not be an accelerometer. Any suitable components may be isolated using the isolation structures. The formation of isolation structures suitable for isolating sensitive electrical components such as accelerometers or other components constructed using MEMS technology is merely illustrative. 
     Component mounting structures with isolation features such as printed circuit board grooves can be used in desktop computers, televisions, and other relatively large electronic devices. Because portable electronic devices are more often subject to unwanted impacts, it may be advantageous to form component mounting structures with isolation features in the printed circuit boards that are used in portable electronic devices. As an example, the component mounting structures may be used in connection with printed circuit boards in laptop computers, tablet computers, cellular telephones, media players, global positioning system units, gaming devices, handheld computers, wristwatch or pendant devices, or other portable computing equipment. 
     An illustrative electronic device that may include component isolation structures is shown in  FIG. 2 . As shown in  FIG. 2 , electronic device  18  may include a housing  20 . Housing  20 , which is sometimes referred to as a case, may be formed from metal, composites, plastic, other suitable materials, or combinations of these materials. Components such as display  22  and input-output devices such as button  25  may be mounted in housing  20 . 
     The interior of housing  20  may be used to house printed circuit boards, electronic components, batteries, etc. A cross-sectional side view of a typical device such as device  18  of  FIG. 2  is shown in  FIG. 3 . As shown in  FIG. 3 , printed circuit board  28  may be mounted on housing portions such as posts  24  using screws such as screws  26 . Printed circuit board  28  may have holes through which screws  26  pass. Posts  24  may have threaded bores that receive the threaded ends of screws  26 . When screws  26  are tightened, printed circuit board  28  may be held against posts  24  and thereby secured in the interior of device housing  20 . 
     Components  30  may be mounted on printed circuit boards  28  using solder balls. This type of component mounted arrangement is sometimes referred to as ball grid array (BGA) packaging or flip-chip mounting. Although solder balls tend to form good electrical connections between the conductive pads of components  30  and the mating conductive traces on printed circuit board  28 , solder ball joints can fail when subjected to excessive stress. 
     Stress levels can be reduced by forming grooves around some or all of a given component. An isolation structure of this type is shown in  FIG. 4 . As shown in  FIG. 4 , component  30  may be mounted on printed circuit board  28 . Holes  34  in printed circuit board  28  may be used to accommodate screws  26  ( FIG. 3 ). Isolation groove  32  is formed around some or all of component  30 . This reduces the mechanical coupling between the peripheral portions of printed circuit board  28  (e.g., the corners near holes  34  where an impact event is felt) and the portion of printed circuit board on which component  30  is mounted (e.g., component mounting region  36  in the example of  FIG. 4 ). The reduction in mechanical coupling between the edges of board  28  and component mounting region  36  isolates component  30  from stress and helps reduce or eliminate the need for underfill. 
     It is not necessary to form groove  32  around all four edges of component  30 . In the  FIG. 4  example, three of the four sides of component  30  are isolated by respective segments of groove  32 . This is, however, merely illustrative. 
     An illustrative configuration in which groove  32  has too distinct segments ( 32 A and  32 B) is shown in  FIG. 5 . In this example, groove portion  32 A covers the right-hand side of component  30  and groove portion  32 B covers the left-hand side of component  30 . Grooves  32 A and  32 B also each have small extending arms that run partway along the upper and lower edges of component  30  to help maximize isolation. Grooves  32 A and  32 B of  FIG. 5  (and the other grooves described herein) are typically devoid of material (i.e., the grooves are air filled). Flexible membranes or other pliable materials may, if desired, be used to fill some or all of the grooves, although this will tend to reduce mechanical isolation. The portions of board  28  that are not removed (i.e., the upper and lower portions  38  in  FIG. 5  that remain in the regions between the gaps in groove  32 ) hold component mounting portion  36  of printed circuit board  28  in place. 
     In some configurations, it may not be desirable to form grooves around the entire periphery of component  30 . In this type of situation, an L-shaped groove such as groove  32  of  FIG. 6  may be used (as an example). 
       FIG. 7  shows an illustrative arrangement in which only a relatively small amount of printed circuit board material remains in region  38  between the two opposing ends of groove  32 . This helps maximize the isolation of inner board portion  36  (and component  30 ) from the rest of board  28 , although less material is available for holding inner region  36  in place. 
     Groove  32  need not be straight. For example, groove  32  may form a circular arc shape, as shown in  FIG. 8 .  FIG. 8  also shows how component  30  need not be rectangular. In general, groove  32  and component  30  can have any suitable shapes with curve edges, straight edges, combinations of curved and straight edges, etc. 
     As shown in  FIG. 9 , multiple components  30  may be isolated within the same isolating opening in printed circuit board  28 . In the  FIG. 9  example, there may be two or more components that are surrounded by a single groove  32 . When isolating multiple components in this way, groove  32  may have a curved shape, may have one or more separate segments, may extend partly around component  30 , may extend around substantially all of component  30 , or may use other suitable groove configurations. 
     To provide additional isolation for component  30 , multiple grooves may be nested within each other. An example of a configuration in which multiple nested grooves  32  are used to isolate a component is shown in  FIG. 10 . As shown in  FIG. 10 , component  30  may be isolated using outer groove  32 ′ and inner groove  32 ″. Electrical connections to component  30  may be made using printed circuit board traces  40 . Traces  40  of  FIG. 10  and the other traces on printed circuit board  28  may be formed on the surface of printed circuit board  28  and in one or more buried interconnect layers. Copper, gold, copper plated with gold, and other metals and conductive materials may be used in forming printed circuit board traces such as traces  40 . To accommodate solder ball connections, parts of the ends of traces  40  (i.e., the portions under component  30 ) may be patterned to form an array of square contact pads or other suitable contact pad structures. Mating contacts may be formed on the underside of component  30 . 
       FIG. 11  shows how isolation grooves  32  may be used to isolate the corners of board  28 . These grooves may be rectangular, may have L-shapes, may have curved shapes, or may have any other suitable shapes. Each corner isolation groove may surround or isolate a separate screw hole  34 . When isolation structures (i.e., grooves  32 ) are used to isolate screw holes  34 , the entire interior surface of board  28  may be isolated from stress. It may therefore not be necessary to separately isolate component  30  using a groove. As shown in the  FIG. 11  example, however, additional isolation may be provided by surrounding some or all of component  30  with a groove (groove  32 ) while using grooves  32  in the corners of board  28  to simultaneously provide isolation from screw holes  34 . 
     Mechanical isolation (stress reduction) can also be provided by adding mechanical stiffening members to board  28 . An illustrative configuration of this type is shown in the top view of board  28  in  FIG. 12 . As shown in  FIG. 12 , rigid stiffing structure  41  may be formed around some or all of component  30 . Rigid stiffening structure  41  may have a ring shape (e.g., a rectangular or circular ring shape). A gap such as gap  43  may be used to accommodate traces. Other configurations, such as configurations in which rigid stiffening structure  41  has multiple segments or different shapes may also be used. Rigid stiffening structure  41  may be formed from ceramic, glass, metal (e.g., stainless steel), printed circuit board material, or other stiff materials that can provide increased rigidity and strength to the vicinity of the portion of printed circuit board  28  on which component  30  is mounted. Stiffening structure  41  may be used in place of groove  32  or, as shown in  FIG. 12 , may be used in connection with groove  32 . 
     A cross-sectional side view of the component isolation structures of  FIG. 12  taken along line  42 - 42  of  FIG. 12  is shown in  FIG. 13 . As shown in  FIG. 13 , component  30  may be mounted on inner printed circuit board component mounting region  36 . Region  36  of  FIG. 13  (and the other FIGS.) may be formed from a rigid rectangular sheet of printed circuit board material, a rectangular region of flex circuit, or other suitable mounting structures. Groove  32  may form an isolating gap between region  36  and the remainder of printed circuit board  28 . Stiffening structure  41  may be connected to portion  36  adjacent to component  30  using adhesive  45  (e.g., pressure sensitive adhesive). 
     A flex circuit or rigid flex structure may be used to mount component  30 . With this type of arrangement, flexible polymer portions of the flex circuit or rigid flex can bridge groove  32  without introducing significant mechanical coupling between interior printed circuit board region  36  and exterior region  28 . 
     An illustrative mounting arrangement that is based on use of rigid flex is shown in  FIG. 14 . As shown in  FIG. 14 , component  30  may be mounted on rigid portion  36  of a rigid flex member. Flexible (flex circuit) tails  44  may from integral portions of the rigid flex member and may extend outwardly from inner layers in rigid printed circuit board portion  36 . Flexible tails  44  may contain conductive lines (traces). At the inner ends of tails  44  (i.e., at end  46  of the right-hand tail in  FIG. 14 ), the conductors in the tails may make contact with interconnect conductors in rigid portion  36 . At the outer ends of tails  44  (i.e., at end  48  of the right-hand tail in  FIG. 14 ), the conductors in the tails may make contact with traces  50  on printed circuit board  28 . Electrical connection between flex tails  44  and traces  50  may be make using connectors, conductive pressure sensitive adhesive, etc. 
     A cross-sectional side view of the component isolation structures taken along line  52 - 52  of  FIG. 14  is shown in  FIG. 15 . As shown in  FIG. 15 , flex circuit tail sections  44  of the rigid flex may be used to bridge groove  32 . Rigid printed circuit board portion  36  may include one or more rigid upper board layers such as layer(s)  36 A and one or more rigid lower board layers such as layer(s)  36 B. One or more layers of flex circuit are sandwiched between layers  36 A and  36 B and have tails  44  that extend outwardly across groove  32 . Conductive adhesive  54  may be used to form a pattern of contacts at the ends of tails  44 . These contacts may electrically interconnect the conductive flex circuit traces of tails  44  to corresponding traces on printed circuit board  28 . 
     If desired, a flex circuit may be used as a mounting structure for component  30  (i.e., without using rigid printed circuit board portions as in a rigid flex scenario). As shown in the cross-sectional side view of  FIG. 16 , for example, flex circuit  56  may be used to form a mounting structure for component  30 . Opening  57  may be, for example, a rectangular opening in printed circuit board  28 . Flex circuit  56  may hold component  30  in place within opening  57 . In this configuration, flex circuit  56  bridges opening  57  and thereby bridges groove  32 , as shown in  FIG. 16 . 
     As shown in the perspective view of component  30  and board  28  of  FIG. 17A , traces such as conductive printed circuit board traces  58  may be routed from component  30  to other components and circuitry on board  28  through region  38 . In this type of configuration, contact pads (terminals) on component  30  may be mounted face down on portion  36  using solder balls  60 . 
     The cross-sectional side view of  FIG. 17B  shows how component  30  may have contact pads  62  that correspond with mating contact pads  64  on component mounting region  36 . Solder balls  60  may electrically and mechanically connect component  30  to region  36  (and thereby board  28 ) without the need for underfill. 
     As shown in  FIG. 18 , wire bonds such as wire bonds  66  may be used to connect contact pads  62  and  64 . In this type of arrangement, some or all of contact pads  62  may be formed on the top (exposed) surface of component  30  rather than the bottom (face-down) surface of component  30 . 
       FIG. 19  shows an illustrative configuration in which flex circuit cable  68  is used to form electrical connections between component  30  and traces  58  on board  28 . Flex circuit cable  68  may bridge groove  32  and may be connected to contact pads on the top of component  30  (as shown in  FIG. 19 ) or may be connected to contact pads formed in region  36 . 
       FIG. 20  is a perspective view of an illustrative component isolation configuration in which there are four flex circuit tails  44  protruding from a common rigid printed circuit board portion  36  (i.e., a rigid flex configuration). In arrangements of the type shown in  FIG. 14 , tails  44  are connected to contact pads on the surface of printed circuit board  28  (e.g., using conductive adhesive). In arrangements of the type shown in  FIG. 20 , flex circuit tails  44  may be formed as an integral portion of board  22 . This type of arrangement may provide good support for component  30 , while mechanically decoupling component  30  from vibrations due to the flexible nature of tails  44 . 
     A cross-sectional side view of the component isolation structures of  FIG. 20  taken along line  70 - 70  of  FIG. 20  is shown in  FIG. 21 . As shown in  FIG. 21 , a layer of flex circuit such as flex circuit based on polyimide or other flexible polymer materials may be used to bridge groove  32 . In the main portions of printed circuit board  28 , portion  72 A of the flex circuit may be sandwiched between rigid upper printed circuit board layer  28 A and rigid lower printed circuit board layer  28 B. In printed circuit board region  36  (on which component  30  is mounted), portion  72 C of the flex circuit may be sandwiched between rigid upper printed circuit board layer  36 A and rigid lower printed circuit board layer  36 B. Portions  72 B of the flex circuit form tails  44  that span groove  32 . 
     With this type of arrangement, portions  72 A,  72 B, and  72 C are integral flex circuit regions in a single unitary piece of flex circuit material. This material is selectively mounted (sandwiched) between respective rigid printed circuit board layers that make up main board portion  28  and component mounting region  36 . 
     An exploded perspective view that shows how this type of structure can be constructed from patterned layers of rigid printed circuit board material and flex circuit material is shown in  FIG. 22 . As shown in  FIG. 22 , printed circuit board  28  may be formed from an upper rigid printed circuit board layer  28 A and a lower rigid printed circuit board layer  28 B. A component such as component  30  (not shown in  FIG. 22 ) may be mounted on region  36 A of upper layer  28 A. Layer  28 A and layer  28 B may be provided with grooves  32 A and  32 B that form groove  32  when board  28  is fully assembled. Layer  28 A may be provided with breakable tabs  78 A and layer  28 B may be provided with breakable tabs  78 B. These breakable structures may help hold regions  36 A and  36 B in place during assembly. Following the formation of board  28  by sandwiching flex circuit layer  72  between layers  28 A and  28 B, tabs  78 A and  78 B may be severed, thereby allowing region  36  (formed from upper layer  36 A and lower layer  36 B) to float free within groove  32 . Flex circuit portions  72 B form flex circuit tails  44  ( FIG. 20 ) that help hold region  36  in place within groove  32 . Conductive traces such as traces  74  may be interconnected to contact pads  76  on the surface of rigid upper layer  28 A using conductive vias in layer  28 A. Layers  28 A,  72 , and  28 B may be connected to each other using intervening layers of adhesive (as an example). 
     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: 20090929
Publication Date: 20140701
Grant Date: 20140701
Priority Date: 20090929
Inventors: YEATES KYLE H.
Assignee: APPLE INC
CPC Classifications: [{"code": "H05K1/182", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09781", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09072", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/2009", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/141", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/1461", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10734", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09063", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/49175", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10734", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09063", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/2009", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/05554", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/4691", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10409", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09081", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/049", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10409", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/189", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K1/147", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/1461", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/05554", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09072", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/049", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/182", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09081", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/147", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2224/48091", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/4691", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2203/049", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/0271", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L2224/48091", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09781", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/222", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/49175", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2203/049", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/189", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K1/0271", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K1/141", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K3/222", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 43780180