Patent Application
20130048347
This relates generally to electronic devices, and, more particularly, to flexible structures in electronic devices.
Electronic devices such as portable computers and handheld electronic devices are becoming increasingly popular. Devices such as these are often provided with wireless communications capabilities. For example, electronic devices may use long-range wireless communications circuitry to communicate using cellular telephone bands. Electronic devices may use short-range wireless communications links to handle communications with nearby equipment. Electronic devices are also often provided with sensors and other electronic components.
It can be difficult to incorporate antennas, sensors, and other electrical components successfully into an electronic device. Some electronic devices are manufactured with small form factors, so space for components is limited. In many electronic devices, the presence of conductive structures can influence the performance of electronic components, further restricting potential mounting arrangements for components.
It would therefore be desirable to be able to provide improved ways in which to incorporate components in electronic devices.
An electronic device may have integral antenna resonating element and proximity sensor capacitor electrode structures formed from conductive structures such as conductive flexible printed circuit (“flex circuit”) structures.
The flex circuit structures may include first and second flex circuit layers. The first and second flex circuit layers may include metal antenna structures and metal proximity sensor electrode structures. Solder may be used to attach electrical components such as surface mount technology (SMT) components to the flex circuit layers. Solder may also be used to electrically connect metal structures on the first and second flex circuit layers to each other. The solder may be formed from a patterned solder paste or from solder ball structures that are held in place with solder resin before solder joint formation.
The first and second flex circuit layers may be laminated together using a compressive fixture. The compressive fixture may have a first fixture with a convex surface and a second fixture with a corresponding concave surface. The first fixture may be formed from a rigid material. The second fixture may be formed from an elastomeric material. The flex circuit layers may be laminated together between the convex and concave surfaces using adhesive. The adhesive may be patterned to form air gaps. The air gaps may allow gas to escape during solder joint formation. The bent shape of the convex and concave surfaces may be used to form a bend in the laminated flex circuit layers.
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.
Electronic devices may be provided with antennas, sensors, and other electronic components. It may be desirable to form these components from flexible structures. For example, it may be desirable to form components for electronic devices from flexible printed circuit structures. Flexible printed circuits, which are sometimes referred to as flex circuits, may include patterned metal traces on flexible substrates such as layers of polyimide or other flexible polymer sheets. Flex circuits may be used in forming antennas, capacitive sensors, assemblies that include antenna and capacitive sensor structures, other electronic device components, or combinations of these structures.
An illustrative electronic device in which electronic components may be used is shown in
As shown in
Device 10 may have user input-output devices such as button 59. Display 50 may be a touch screen display that is used in gathering user touch input. The surface of display 50 may be covered using a dielectric member such as a planar cover glass member. The central portion of display (shown as region 56 in
A layer of material such as an opaque ink or plastic may be placed on the underside of display 50 in peripheral regions 54 (e.g., on the underside of the cover glass). This layer may be transparent to radio-frequency signals. The conductive touch sensor electrodes in region 56 may tend to block radio-frequency signals. However, radio-frequency signals may pass through the cover glass and opaque layer in inactive display regions 54 (as an example). In the opposite direction, radio-frequency signals may pass through antenna window 58. Lower-frequency electromagnetic fields also pass through window 58, so capacitance measurements for a proximity sensor may be made through antenna window 58.
Housing 12 may be formed from one or more structures. For example, housing 12 may include an internal frame and planar housing walls that are mounted to the frame. Housing 12 may also be formed from a unitary block of material such as a cast or machined block of aluminum. Arrangements that use both of these approaches may also be used if desired.
Housing 12 may be formed of any suitable materials including plastic, wood, glass, ceramics, metal, fiber-based composites such as carbon fiber composites, other suitable materials, or a combination of these materials. In some situations, portions of housing 12 may be formed from a dielectric or other low-conductivity material, so as not to disturb the operation of conductive antenna elements that are located in proximity to housing 12. In other situations, housing 12 may be formed from metal elements. An advantage of forming housing 12 from metal or other structurally sound conductive materials is that this may improve device aesthetics and may help improve durability and portability.
With one suitable arrangement, housing 12 may be formed from a metal such as aluminum. Portions of housing 12 in the vicinity of antenna window 58 may be used as antenna ground. Antenna window 58 may be formed from a dielectric material such as polycarbonate (PC), acrylonitrile butadiene styrene (ABS), a PC/ABS blend, or other plastics (as examples). Window 58 may be attached to housing 12 using adhesive, fasteners, or other suitable attachment mechanisms. To ensure that device 10 has an attractive appearance, it may be desirable to form window 58 so that the exterior surfaces of window 58 conform to the edge profile exhibited by housing 12 in other portions of device 10. For example, if housing 12 has straight edges 12A and a flat bottom surface, window 58 may be formed with a right-angle bend and vertical sidewalls. If housing 12 has curved edges 12A, window 58 may have a similarly curved surface.
A cross-sectional view of device 10 taken along line 1300 of
The antenna resonating element formed from structures 200 may be based on any suitable antenna resonating element design (e.g., structures 200 may form a patch antenna resonating element, a single arm inverted-F antenna structure, a dual-arm inverted-F antenna structure, other suitable multi-arm or single arm inverted-F antenna structures, a closed and/or open slot antenna structure, a loop antenna structure, a monopole, a dipole, a planar inverted-F antenna structure, a hybrid of any two or more of these designs, etc.). Housing 12 may serve as antenna ground for an antenna formed from structure 200 or other conductive structures within device 10 may serve as ground (e.g., conductive components, traces on printed circuits, etc.).
Conductive structures 200 may form one or more proximity sensor capacitor electrodes. With one suitable arrangement, structures 200 may be formed from a flex circuit structure. The flex circuit structure may include at least first and second layers of patterned conductive material. The first and second layers of patterned conductive material may be formed on opposing sides of the flex circuit structure (e.g., top and bottom sides). At frequencies associated with antenna signals, the first and second layers may be effectively shorted to each other and may form an antenna resonating element. At lower frequencies, the first and second layers may serve as first and second proximity sensor capacitor electrodes (e.g., an inwardly directed electrode and an outwardly directed electrode).
Structures 200 may be implemented by laminating together two or more flex circuit layers to form a composite flex circuit structure. By incorporating multiple flex circuit layers into structures 200, potentially complex patterns of conductive traces (e.g., traces on three or more different metal layers) may be formed. Components may be mounted on the flex circuit layers and interconnected to the patterns of conductive traces. Lamination tools may be used in forming the composite flex circuit structure. The lamination tools may bend the flex circuit layers prior to lamination to help minimize built-in stress relative to flex circuit structures formed by bending a single layer of flex circuit material.
If desired, structures 200 may include integrated circuits, discrete components such as resistors, inductors, and capacitors, and other electronic devices. Structures 200 may also include conductive traces for forming antenna resonating element patterns, transmission lines, and proximity sensor electrode patterns (as examples).
Structures 200 may be formed from a first flex circuit layer and a second flex circuit layer. A first layer of patterned conductive material in structures 200 may be formed from one or more conductive trace layers in the first flex circuit layer. A second layer of patterned conductive material in structures 200 may be formed from one or more conductive trace layers in the second flex circuit layer. Conductive paths may be formed between the first and second layers using solder or other conductive materials (e.g., anisotropic conductive film, etc.).
The first layer of patterned conductive material may face outwards in direction 300 and the second patterned conductive layer may face inwards into housing 12 in direction 302 (as an example). The two layers of patterned conductive material may be electrically isolated from each other by interposed dielectric to form a parallel plate capacitor. At frequencies below about 1 MHz, the parallel plate capacitor may have a relatively high impedance (e.g., forming a DC open circuit), so that the patterned coating layers may serve as independent first and second proximity sensor capacitor electrodes. At frequencies above 1 MHz (e.g., at frequencies above 100 MHz or above 1 GHz), the impedance of the parallel plate capacitor is low, so the patterned conductive layers may be effectively shorted together. This allows both of the layers to operate together as a unitary patterned conductor in an antenna resonating element.
During operation of the antenna formed form structures 200, radio-frequency antenna signals can be conveyed through dielectric window 58. Radio-frequency antenna signals associated with structures 200 may also be conveyed through a display cover member such as cover glass 60. Display 50 may have an active region such as region 56 in which cover glass 60 has underlying conductive structure such as display panel module 64. The structures in display panel 64 such as touch sensor electrodes and active display pixel circuitry may be conductive and may therefore attenuate radio-frequency signals. In region 54, however, display 50 may be inactive (i.e., panel 64 may be absent). An opaque layer such as plastic or ink 62 may be formed on the underside of transparent cover glass 60 in region 54 to block the antenna resonating element from view. Opaque material 62 and the dielectric material of cover member 60 in region 54 may be sufficiently transparent to radio-frequency signals that radio-frequency signals can be conveyed through these structures in directions 70.
Transmission line 44 may be coupled between structures 200 and associated radio-frequency transceiver circuitry. Transmission line 44 may have a positive signal line that is connected to positive antenna feed terminal 76 and a ground signal line that is connected to ground antenna feed terminal 78. Positive antenna feed terminal 76 may be coupled to positive antenna feed terminal 76′ on antenna resonating element branch 200-3 via capacitor Cfp. Ground antenna feed terminal 78 may be coupled to ground antenna feed terminal 78′ on antenna resonating element branch 200-4 via capacitor Cfg.
The capacitance values for capacitors Cfp and Cfg are preferably of sufficient size to ensure that the impedance of these capacitors is low and does not disrupt antenna operation at frequencies associated with wireless signals in device 10. For example, if path 44 is being used to handle signals at frequencies of 100 MHz or more (e.g., cellular telephone signals, wireless local area network signals, etc.), the values of Cfp and Cfg may be 10 pF or more, 100 pF or more (e.g., 100s of pF), or may have other suitable sizes that ensure that transmitted and received antenna signals are not blocked. At lower frequencies, the impedance of capacitors Cfp and Cfg is preferably sufficiently large to prevent interference from reaching the antenna resonating element formed from structures 200.
Proximity sensor circuitry may be coupled to structures 200 through inductor(s) 202. For example, proximity sensor circuitry such as capacitance-to-digital converter circuitry 136 or other control circuitry may be used to make capacitance measurements using one or more capacitor electrodes formed from the patterned conductive layer(s) of structures 200. Inductor(s) 202 may have impedance values (e.g., impedances of 100s of nH) that prevent radio-frequency antenna signals (e.g., antenna signals at frequencies of 100 MHz or more) from reaching capacitance-to-digital converter 136 or other proximity sensor circuitry while allowing AC proximity sensor signals (e.g., signals with frequencies below 1 MHz) to pass between structures 200 and the proximity sensor circuitry.
Capacitors Cfp and Cfg form a high pass filter. By using high-pass circuitry such as capacitors Cfp and Cfg, low frequency noise can be prevented from interfering with antenna operation for structures 200. Inductor(s) 202 form a low-pass filter. By using low-pass circuitry such as inductor(s) 202, radio-frequency noise from antenna signals can be prevented from interfering with proximity sensor operation for structures 200. If desired, other types of high-pass and low-pass filters may be interposed between structures 200 and the radio-frequency transceiver circuitry and proximity sensor circuitry that is associated with structures 200. The arrangement of
When assembled, conductive structures 200 may appear as shown in
As shown in the
To help accommodate shapes for structures 200 that allow structures 200 to fit within housing 12 such as shapes with one or more bends, it may be desirable to form structures 200 using a lamination process. During the lamination process, two or more substrate layers such as two or more flex circuit layers may be attached to each other using adhesive.
Flex circuit layers for forming structures 200 may be formed from sheets of polyimide or other flexible polymer layers. Conductive patterned materials such as traces of metal may be used in forming antenna structures, component interconnects, transmission lines, sensor electrodes, and other conductive structures on the flex circuits. The flex circuits may contain one or more layers of metal traces with one or more layers of intervening dielectric (e.g., one or more intervening layers of polyimide or other flex circuit substrate materials).
During lamination, adhesive, heat, and/or pressure may be used in connecting multiple flex circuit layers together. Solder or other conductive materials (e.g., anisotropic conductive film, etc.) may be used in electrically connecting the metal traces on one flex circuit layer to another. Solder connections may be formed by reflowing solder paste structures in a reflow oven, by reflowing balls of solder in a reflow oven, by heating solder paste or solder balls using a localized heat source such as a heat bar (hot bar) or heat gun, or using other suitable solder reflow techniques.
Solder paste may be deposited on the surfaces of substrates 306 and 308 using solder paste patterning tool 310. Tool 310 may include screen printing equipment or other equipment that can deposit a desired pattern of solder paste onto one or more surfaces of each flex circuit substrate. Patterned metal traces in substrates 306 and 308 may be used in forming solder pads. During solder paste deposition operations with tool 310, solder paste may be screen printed or otherwise deposited on top of the solder pads on substrates 306 and 308. In
If desired, integrated circuits, discrete components such as resistors, inductors, capacitors, switches, and other electrical components may be mounted on solder paste 312 and 314 (see, e.g., illustrative electrical component 322 on solder paste 312 on substrate 306 in the example of
Following placement of components 322 on substrate 306 using pick and place tool 320, a heat source such as reflow oven 324 may be used to reflow the solder on substrate 306. During the reflow process, the heat produced by oven 324 or other suitable heat source can convert the solder paste into solder connections with components 322 and/or solder balls on exposed solder pads.
To facilitate the formation of bends in structure 200, substrates 306 and 308 may be bent prior to and/or during the lamination process. In this way, relatively thick structures can be formed with bends without introducing undesirably large amounts of stress. As shown in
After the substrates have been bent into their desired shape, the lamination process can be used to attach substrates 306 and 308 together in their bent shape. Lamination may be performed using adhesive and heat and pressure (as an example). To minimize stress, it may be desirable to slightly over-bend substrates 306 and 308 within compressive fixtures 324. Other configurations may also be used (e.g., bending substrates 306 and 308 to their desired final shape, under-bending substrates 306 and 308, etc.).
Compressive fixtures 324 may include cavities such as rectangular recesses or recess with other shapes to accommodate protruding components (e.g., components such as components 322). Solder joints can be formed between substrates 306 during the use of tools 324. For example, tools 324 may include heat bar equipment, an oven, or other heating equipment for reflowing solder 312, 314, and/or 316, thereby electrically connecting the traces in substrates 306 and 308.
Following lamination of substrates 306 and 308 using tool 324, substrates 306 and 308 have a desired bent shape and form structures 200. Structures 200 may, if desired, be attached to a support structure such as carrier 326. Carrier 326 may, for example, be formed from a dielectric such as plastic (e.g., to accommodate structures such as antenna structures, capacitive proximity sensor structures, and other structures that might potentially be affected by the presence of conductive support structures). Structures 200 may be attached to carrier 326 to form mounted structures 330 using adhesive or other suitable attachment mechanisms.
An illustrative set of material layers that may be used in forming substrates such substrate layers 306 and 308 of
As shown in
In the arrangement for layers 306 and 308 that is shown in
As shown in
Posts 374 of fixture 376 may protrude through holes 372. When substrate layer 306 is placed over layer 308 for lamination, holes 364 may fit over posts 374 or other tool alignment structures. By providing layers 306 and 308 with matching alignment holes or other alignment features and by providing the compressive fixtures with mating alignment posts or other mating alignment features, layers 306 and 308 may be aligned with respect to the compressive fixtures and to each other during lamination.
Fixture 376 may have a concave surface with a bend radius that is slightly larger than the desired bend radius for layers 306 and 308. Fixture 378 may have a convex surface with a bend radius equal to the desired bend radius for layers 306 and 308 (i.e., a bend radius slightly smaller than the desired final bend radius for the bend in structures 200). When fixture 378 is pressed against fixture 376 in direction 380, layers 306 and 308 are compressed against each other while the elastomeric material of fixture 376 allows the concave surface of fixture 376 to conform to the convex surface of fixture 378. During the compression process, layers 308 and 306 are initially compressed together at the tip of fixture 378. Following additional compression, the rest of layers 308 and 306 are compressed together. In this way, layers 306 and 308 are progressively compressed together starting at their centers and moving towards their peripheries. This progressive lateral compression arrangement helps to avoid formation of air bubbles between layers 306 and 308 during lamination.
If desired, the compressive fixtures may be provided with cavities to accommodate protruding components on structures 200. As shown in
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.
