Patent Publication Number: US-8525058-B2

Title: Snorkel for venting a dome switch

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of previously filed U.S. Provisional Patent Application No. 61/310,917, filed Mar. 5, 2010, which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Users can provide inputs to electronic devices using many different approaches. For example, an electronic device can include different input interfaces by which a user can interact with the device. The input interfaces can include, for example, one or more switches, buttons, actuators, or sensors (e.g., touch sensors), the actuation of which the device can detect. In some cases, an electronic device can include a dome switch, which can be depressed to provide a detectable input. The dome switch is typically constructed by placing a conductive dome over a contact pad on a circuit board. When the dome is pressed, the dome can invert such that an inner surface of the dome contacts the contact pad. The dome inversion also provides a tactile ‘click’ that enhances the user&#39;s interaction with the switch. To actuate the dome switch, a user typically presses a cosmetic piece placed over the dome. In response to the user pressing the cosmetic piece, the dome is in turn is depressed and comes into contact with the contact point. 
     A dome switch can enclose a volume of air between the inner surface of the dome and the circuit board to which the dome is mounted. When the dome is depressed, the air within the enclosed volume may need to be displaced so that the center of the dome can contact the circuit board contact pad. To displace the air, a coversheet placed over the dome can include openings connecting the interior volume to the environment in which the dome switch is placed. When the dome is collapsed to close a circuit, air can be expelled from the internal volume through the openings, and remove an air pressure resistance to the dome movement. Air can re-enter the internal volume through the openings when the dome reverts to its initial position. 
     The openings in the dome coversheet, however, can provide a path for debris, water, or other external particles to enter the internal volume of the dome switch. If a conductive particle infiltrates the internal volume, the particle can cause corrosion or promote the formation of substances that prevent the proper operation of the switch. For example, particles can cause rust, oxidation, dendrite growth, or salt, sugar or chemical deposits. As another example, water can infiltrate the internal volume of the dome switch and short the switch. 
     SUMMARY OF THE INVENTION 
     A dome switch that includes a remote venting mechanism is provided. In particular, a dome switch can include a channel through which air can be vented out of the dome switch while preventing debris from migrating to underneath the dome. 
     A dome switch can enclose a volume of air between a dome and a flex circuit. The volume of air can be expelled from the volume when depressed to provide a responsive tactile effect. To prevent contaminants from entering the volume enclosed by the dome when the dome is actuated, the location and size of an opening connecting the volume within the dome to the dome environment can be selected such that the opening is away from the dome itself. In some embodiments, the dome switch can include a channel or tubular structure extending from the dome region and having an opening away from the dome through which air can flow. 
     The channel can be constructed as part of components of the dome switch. For example, the channel can be defined in a spacer positioned between a flex circuit and a film layer of the dome switch (e.g., a film covering the dome to retain the dome to the circuit board), where the spacer defines the channel sides. The distal end of the channel (e.g., the end away from the dome) can have an opening for venting air, which can be defined in any suitable component of the dome switch including, for example, in one or more of the circuit board, spacer, or film. 
     In some embodiments, a protective film can be placed over an opening of a dome switch. The protective film can include holes large enough to allow air to pass, but small enough to prevent contaminants (e.g., liquids or debris) from passing through the protective film. In some embodiments, the protective film can include a treatment or coating to enhance the film&#39;s ability to repel contaminants. For example, the protective film can include a hydrophobic coating. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features of the present invention, its nature and various advantages will be more apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic exploded view of an illustrative dome switch having a channel for venting in accordance with one embodiment of the invention; 
         FIG. 2  is a schematic view of an illustrative dome switch having an open channel in accordance with one embodiment of the invention; 
         FIG. 3  is a schematic view of an illustrative dome switch having a channel with an open bottom surface in accordance with one embodiment of the invention; 
         FIG. 4  is a schematic view of an illustrative dome switch having a flex extension for venting in accordance with one embodiment of the invention; 
         FIG. 5  is a schematic view of an illustrative dome switch having a tube connected to a channel in accordance with one embodiment of the invention; 
         FIG. 6  is a schematic view of an illustrative dome switch having a step in accordance with one embodiment of the invention; 
         FIG. 7  is a schematic view of an illustrative dome switch having a protective film over a channel opening in accordance with one embodiment of the invention; 
         FIG. 8  is a schematic view of an illustrative dome switch having a protective mesh over vents adjacent to the dome in accordance with one embodiment of the invention; 
         FIG. 9  is a flowchart of an illustrative process for constructing a dome switch having a channel for remote venting in accordance with one embodiment of the invention; and 
         FIG. 10  is a flowchart of an illustrative process for providing a remotely venting dome switch in accordance with one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device can include several input interfaces for detecting inputs provided by a user including, for example, one or more buttons, switches, actuators, sensors, or combinations of these. In one implementation, an electronic device can include one or more dome switches that can be actuated to close a circuit. For example, an electronic device can include one or more dome switches associated with a device button (e.g., a home button or a key pad), a device housing, a region of a device housing, or combinations of these. In one implementation, a dome switch can be integrated within a device housing such that deformation of the device housing can cause the dome switch to invert at least partially and close a circuit in which the dome switch is integrated. 
       FIG. 1  is a schematic exploded view of an illustrative dome switch having a channel for venting in accordance with one embodiment of the invention. Switch  100  can include dome  112  and film layer  110  placed over spacer  120 , which in turn can be coupled to flex circuit  130 . Film layer  110  can provide an impermeable seal around portions of switch  100 . For example, film layer  110  can include an adhesive applied to one surface of the film layer, such that the adhesive can adhere the film layer to the spacer and trap dome  112  between the film layer and the flex circuit. It will be understood, however, that spacer  120  may not be necessary, and that a single layer of adhesive can instead or in addition be placed on the circuit to adhere to the dome or to the film layer. Flex circuit  130  can provide a support structure for receiving dome  112 . In some embodiments, flex circuit  130  can include one or more components for providing an electrically conductive path between the flex circuit and the dome. For example, flex circuit  130  can include one or more exposed conductive pads to be put into contact with one or more regions of dome  112 . The one or more exposed pads can be electrically isolated such that a circuit including the pads remains open unless the dome is at least partially inverted and connects the pads. 
     In some embodiments, dome switch  100  can include release liner  140  that can serve to assemble the components of dome switch  100  and to secure dome switch  100  within an electronic device. Release liner  140  can include one or more layers of adhesive to connect a portion of dome switch  100  to the electronic device. For example, release liner  140  can include a layer of adhesive (e.g., a glue layer), a tape layer (e.g., double sided tape), or a layer of adhesive coupled to a sheet. Release liner  140  can include alignment tabs  142  for ensuring a proper placement of the switch. The alignment tabs can include one or more targeting features including, for example, one or more holes to be aligned with corresponding features of an electronic device component on which dome switch  100  is placed. 
     Dome  112  can be constructed such that at least an inner surface of the dome (e.g., a concave surface of the dome) includes a conductive path. For example, dome  112  can be constructed from a conductive material (e.g., sheet metal) or a non-conductive material having an inner conductive surface (e.g., a plastic material with a conductive coating applied to the inner surface of the dome). Layer  110  can extend beyond the periphery of dome  112  by any suitable amount. In one implementation, layer  110  can extend beyond dome  112  by at least a minimum amount for ensuring a hermetic seal between dome  112  and flex circuit  130  (e.g., via an adhesive applied to layer  110  and connecting the layer to the flex circuit). This seal may be important, for example, to prevent debris or liquids from entering the space enclosed by dome  112 . In some embodiments, in some regions, layer  110  can extend beyond dome  112  by an amount far exceeding the minimum amount required for ensuring a seal. For example, layer  110  can include extension  114  forming an arm extending from the periphery of dome  112 . In some embodiments, the size, position and shape of extension  114  can be determined from the size, position and shape of another component of dome switch  100 . For example, extension  114  can be selected to match channel  122  of spacer  120 , or to match the shape of flex circuit  130 . 
     Spacer  120  can be placed between layer  110  and flex circuit  130  to create a gap around the periphery of dome  112 . Spacer  120  can have any suitable shape including, for example, a portion having cutouts or other features for receiving other elements of the dome switch. For example, a portion of spacer  120  positioned near dome  112  can include an opening in which dome  112  can lie. The opening can be sized to be larger than the dome, such that there may be free space around the dome. The free space can be used to direct air from within the dome switch out from underneath the dome when the dome is actuated. In some embodiments, the spacer can be positioned around the dome to serve as a barrier preventing debris, particles or liquid from seeping underneath dome  112  and into the volume enclosed between the dome and the circuit (e.g., where an electrical contact occurs). In some embodiments, spacer  120  may not extend around the entirety of the periphery of dome  112 . Instead, spacer  120  can be limited to a portion of flex circuit  130  that extends away from the dome (e.g., the spacer is only used to define channel  122 , described below). 
     Spacer  120  can have any suitable size. For example, spacer  120  can have a small thickness (e.g., 0.1 mm), a large thickness (e.g., (0.5 mm), or a variable thickness. The thickness of the spacer can be selected such that dome  112  can be inverted and connect with contact pads of circuit  130  without the spacer adversely affecting the operation of the dome. In particular, the thickness of the spacer can be at most equal to the height of the dome. 
     Spacer  120  can be secured between layer  110  and flex circuit  130  using any suitable approach. For example, an adhesive, mechanical connector, hook and fastener material, tape, or combinations of these can be used couple the spacer to one or both of the layer and flex circuit. In one implementation, spacer  120  can include adhesive applied to one or both surfaces of the spacer to couple the spacer to the flex circuit and layer. In an alternative approach, a piece of double sided tape can be used to couple the spacer to one or both of the layer and flex circuit. 
     Because air is expelled from dome switch  100  when dome  112  is at least partially inverted (e.g., the air enclosed in the volume between dome  112  and flex circuit  130  must be expelled to maintain a crisp tactile feedback), a path can be provided for the air to escape the dome to the device environment. To distance the opening at which air enters dome switch  100  from the flex circuit contact pads and from the conductive interior surface of the dome, spacer  120  can include a portion having side walls placed apart from each other to define channel  122  extending from a region adjacent to dome  112  to a region away from dome  112 . The channel can be in fluid communication with air underneath or around dome  112 . Channel  122  can be positioned such that an open end of channel  122  is located in a portion of the electronic device that is known to have or likely to have clean air (e.g., air that does not include any contaminants or debris). For example, the open end of channel  122  can be placed in an internal region of a device that is away from openings, ports or interfaces of the device (e.g., away from buttons or openings for audio). In this manner, it can be unlikely that foreign contaminants will reach the open end of the channel and find their way to the dome. 
     Channel  122  can be delimited by side walls  123  and  124 , which can be spaced apart to define a region into which air can flow out from underneath dome  112 . Channel  122  can extend between distal channel end  125  and proximal channel end  126  (e.g., near dome  112 ). Channel  122  can have any suitable height including, for example, a height substantially equal to that of spacer  120  (e.g., when channel  122  is defined within the spacer). Channel  122  can have any suitable width including, for example, a width determined from the volume of air to expel from underneath dome  112 . For example channel  122  can have a width in the range of 0.10 mm to 0.50 mm, such as 0.30 mm. 
     In some embodiments, a portion of layer  110  (e.g., extension  114 ) can serve as a top or upper boundary for channel  122 , while flex circuit  130  can serve as a bottom or lower boundary. Alternatively, channel  122  can be defined in spacer  120  such that portions of the spacer form one or both of the top and bottom boundaries of the channel. By providing upper and lower boundaries coupled to side walls  123  and  124 , air can be directed through proximal end  126  towards distal end  125  of the channel and away from dome  112 . Once air has reached end  125  of channel  122 , the air can escape from within dome switch  100 . In one implementation, the air can escape through the top surface of the channel (e.g., through layer  110 ). For example, the tip of extension  114  corresponding to end  125  of channel  122  can include opening  116  in communication with the channel. Opening  116  can be in communication with an internal volume of an electronic device in which dome switch  100  is placed, such that when dome  112  is depressed, air can flow in or out of the volume enclosed by dome  112  and flex circuit  130  through channel  122  and opening  116 . Opening  116  can have any suitable size including, for example, a size determined from the volume of air to expel from underneath dome  112  (e.g., a size similar to the width of channel  122 ). 
     In some embodiments, the air can instead or in addition escape along the axis of the channel.  FIG. 2  is a schematic view of an illustrative dome switch having an open channel in accordance with one embodiment of the invention. Dome switch  200  can include film layer  210 , spacer  220 , and flex circuit  230 , each of which can include some or all of the features of the corresponding elements of dome switch  100  ( FIG. 1 ). Spacer  220  can include channel  222  extending from proximal end  226  adjacent to dome  212  to distal end  225 . To allow air to escape from the volume between dome  212  and flex circuit  230 , channel  222  can include opening  227  through a wall of channel  222  near end  225 . For example, opening  226  can extend along an axis of channel  222  (e.g., as a prolongation of channel  222 ). As another example, opening  227  can extend through a side wall of channel  222  (e.g., when end  225  of the channel is closed). 
     Opening  227  can have any suitable size relative to the width of channel  222 . For example, opening  227  can have the same width as channel  222 . As another example, opening  227  can include a larger opening than the width of channel  222  (e.g., a funnel-like shaped opening). As still another example, opening  227  can be smaller than the width of channel  222 . The particular size of opening  227  and the width of channel  222  can be selected based on any suitable criteria including, for example, properties of the particular dome and flex circuit used for the dome switch (e.g., the size of the dome, the volume of internal air enclosed, or the travel of the dome when it is depressed). 
     In some embodiments, the air can instead or in addition escape through a bottom surface of the channel.  FIG. 3  is a schematic view of an illustrative dome switch having a channel with an open bottom surface in accordance with one embodiment of the invention. Dome switch  300  can include film layer  310 , spacer  320 , and flex circuit  330 , each of which can include some or all of the features of the corresponding elements of dome switch  100  ( FIG. 1 ). Spacer  320  can include channel  322  extending from proximal end  326  near dome  312  to distal end  325 . In particular, channel  322  can be defined by layer  310  serving as a top surface, flex circuit  330  serving as a bottom surface, and spacer  320  forming side walls and end  325  of the channel. To allow air to escape from the volume between dome  312  and flex circuit  330 , flex circuit  330  can include opening  337  in communication with channel  322  (e.g., with a portion of channel  322  adjacent to end  325 ). Opening  337  can extend through the thickness of flex circuit  330  such that air can escape from channel  322  into an internal volume of an electronic device in which dome switch  300  is installed. Opening  337  can have any suitable size including, for example, a size determined from the volume of air to expel from underneath dome  312  (e.g., a size substantially matching the width of channel  322 ). 
     Although the channels of  FIGS. 1-3  were shown as substantially straight channels extending from the dome, it will be understood that the channels can have any suitable shape, or follow any suitable path (e.g., a curved channel extending from the dome). In some embodiments, the shape or path of a channel extending from a dome can be determined from the shape of a flex circuit, from the position of other components of the dome switch (e.g., other components or stiffeners coupled to the flex), or from the position of components of the electronic device in which the dome switch is placed. In some embodiments, a dome switch can include several channels extending in the same or different directions (e.g., two channels extending from a single region of the dome switch or toward a single region of the electronic device, or two channels extending in different directions). In some embodiments, a single channel can include several openings (e.g., a top opening and an end opening). The openings can be distributed along any suitable portion of the channel including, for example, near the dome (e.g., a small hole in the film layer), along the channel length (e.g., a hole in the side wall), and near the end of the channel (e.g., through the flex circuit). In some cases, the channel size (e.g., width and height) can vary based on the position and size of different openings in the channel. 
     A channel used to vent air from a dome switch can have any suitable length. In the examples of  FIGS. 1-3 , the channel extends along the length of the flex circuit until the channel reaches a stiffener (e.g., stiffener  160 ,  260 ,  262 ,  360  or  362 ). The stiffener can include a relatively rigid component coupled to the flex circuit in a region opposite one or more electrical components coupled to the flex (e.g., electrical components are soldered to a first surface of the flex, and the stiffener is coupled to the opposite surface of the flex to protect the interface between the component and the flex). The stiffener can have any suitable thickness including, for example, a thickness at least equal to or larger than the thickness of the spacer. This may prevent the channel from following the flex past the spacer. 
     In some cases, however, it may be desirable to vent a dome switch in or through areas in the vicinity of the stiffener. Any suitable approach can be used to divert a channel away from or around a stiffener. In some cases, the channel can be partially or entirely separated from the flex circuit to provide an unobstructed path for venting the dome switch.  FIG. 4  is a schematic view of an illustrative dome switch having a flex extension for venting in accordance with one embodiment of the invention. Dome switch  400  can include any of the features of dome switch  100  ( FIG. 1 ), described above. Dome switch  400  can include flex circuit  430  providing contact pads for the dome switch, and supporting one or more electrical components (e.g., resistors). To protect the electrical components from damage caused by bending or displacing flex circuit  430 , dome switch  400  can include stiffener  460  placed on flex circuit  430  opposite the electrical components. Spacer  420  can be placed over flex circuit  430  to provide channel  422  through which air can be expelled from underneath the dome. Because of stiffener  460 , however, the length of channel  422  can be restricted. 
     In some embodiments, flex circuit  430  can include arm  432  extending around stiffener  460  and providing an alternate path for spacer  420  (e.g., a non-linear path or curved path). Arm  432  can include a conductive flex circuit section (e.g., if another electrical component is coupled to arm  432  at a further distance from the dome), or a non-conductive flex circuit section. Arm  432  can extend around stiffener  460  at any suitable distance from the dome. For example, arm  432  can extend directly from a portion of the flex circuit other than the portion of flex circuit  430  having stiffener  460 . As another example, arm  432  can extend from the region of flex circuit  430  that is between the dome and stiffener  460 . Arm  432  can have any suitable length including, for example, a length that exceeds the length of the other portions of flex circuit  430 . Alternatively, arm  432  can form a bridge around stiffener  460  such that arm  432  reconnects with flex circuit  430  after the stiffener. 
     Channel  422  can extend along arm  432  in much the same way as channel  422  is formed on flex circuit  430 . For example, spacer  420  can match the shape of arm  432 , while a film layer can also match the shape of arm  432  and spacer  420 . The spacer can adhere to both arm  432  and the film layer using any suitable approach including, for example, using one or more adhesives. 
     In some embodiments, the channel can instead or in addition be coupled to a tube that directs the channel away from the flex.  FIG. 5  is a schematic view of an illustrative dome switch having a tube connected to a channel in accordance with one embodiment of the invention. Dome switch  500  can include some or all of the features of dome switch  100  ( FIG. 1 ). In particular, dome switch  500  can include flex circuit  530  having stiffener  560  limiting the range of spacer  520  that defines channel  522  for directing air expelled from the dome switch away from the dome. Instead of defining an additional flex circuit arm for extending the channel, as shown in  FIG. 4 , tube  524  can be coupled to channel  522 . For example, an opening can be formed in one or more of a top, bottom or side surface of the channel (e.g., in a flex circuit, in a film layer, or in a side wall or end wall of the spacer) to which tube  524  can be connected. Tube  524  can be coupled to the opening in channel  522  using any suitable approach including, for example, an adhesive, tape, heat staking, a fastener, or combinations of these. In some embodiments, the coupling approach can be selected to provide a hermetic seal between channel  522  and tube  524 . Tube  524  can extend from channel  522  to any suitable location. For example, tube  524  can extend to a portion of an electronic device having air likely to have no contaminants (e.g., a portion of the device away from openings or holes in the device housing). In some embodiments, tube  524  can have one or more openings for venting air from channel  522 . 
     Tube  524  can have any suitable shape. For example, tube  524  can include a substantially circular or elliptical tube. Alternatively, tube  524  can include a polygonal or arbitrary cross-section, or a variable cross-section. The tube can have any suitable size (e.g., diameter) including, for example, a size that substantially corresponds to the size of channel  522  (e.g., a size that allows a consistent and smooth flow of air between channel  522  and tube  524 ). 
     In some embodiments, the channel can be extended by changing the plane in which the channel lies. For example, another plane co-planar to the plane of the flex or co-planar to the plane that includes the periphery of the dome can be selected. In one implementation, the channel can include a step for passing over a stiffener.  FIG. 6  is a schematic view of an illustrative dome switch having a step in accordance with one embodiment of the invention. Dome switch  600  can include some or all of the features of dome switch  100  ( FIG. 1 ). In particular, dome switch  600  can include film layer  610  placed over spacer  620  that defines channel  622  having closed end  625  (e.g., closed end  625  can be required by a stiffener on a flex circuit). To extend channel  622  beyond closed end  625 , dome switch  600  can include secondary sheet  640  and secondary spacer  642 . Secondary sheet  640  can define a new bottom surface for channel  622 , where the secondary sheet may not be at the same height as the flex circuit. For example, secondary sheet  640  can be placed over the stiffener. As another example, the stiffener can serve as secondary sheet  640 . Secondary sheet  640  can be positioned such that its top surface is substantially aligned with the top surface of spacer  620  (and with the top surface of closed end  625 ). 
     To extend channel  622 , secondary spacer  642  can be overlaid on secondary sheet  640  (and, in some cases, a portion of spacer  620 , such as the portion of spacer  620  near end  625 ) to form a step in channel  622 . Secondary spacer  642  can define secondary channel  644  stepped up from channel  622 . Secondary channel  644  can have any suitable size including, for example, a size that is substantially the same as that of channel  622  (e.g., same height and width). In some embodiments, film  610  can have an initial opening near end  625  to vent some of the air expelled from the dome. This can enable secondary channel  644  to be smaller than channel  622 . 
     Dome switch  600  can have any suitable number of channels at different levels. For example, dome switch  600  can include several increasing levels of channels. As another example, dome switch  600  can include several levels of channels that step up and down (e.g., a first channel at the level of channel  622 , a second channel at the level of channel  644 , and a third channel back at the level of channel  622 ). In some embodiments, each secondary spacer (e.g., secondary spacer  640 ) can include a tapered edge to ensure that film layer  610  can adhere to the spacers without undesired openings in the spacer-film layer interface. 
     Returning to  FIG. 1 , dome switch  100  can include protective film  150  coupled to film layer  110  via adhesive gasket  152 . Protective film  150  can be placed over an opening of channel  122  such that the film can prevent the ingress of debris, liquid (e.g., water, sweat, alcohol, soda, coffee, tea, or milk), or other contaminants into the channel. In some embodiments, protective film can instead or in addition be placed over a vent incorporated in another portion of the dome switch (e.g., one or more vents of the dome). Adhesive gasket  152  can include an opening corresponding to an opening of the channel, such that air can flow from the channel to protective film  150 . 
       FIG. 7  is a schematic view of an illustrative dome switch having a protective film over a channel opening in accordance with one embodiment of the invention. Dome switch  700  can include some or all of the features of dome switch  100 . In particular, dome switch  700  can include film layer  710  placed over spacer  720  and coupled to flex circuit  730 . Spacer  720  can include channel  722  through which air enclosed between dome  712  and flex circuit  730  can be expelled when the dome is depressed. Channel  722  can include opening  726 , shown to be in film layer  710  (though it will be understood that opening  726  can be in any suitable portion of dome switch  700 ) for communicating with the outside of dome switch  700 . Protective film  750  can be placed over opening  726  to prevent foreign particles or contaminants from entering the enclosed volume of dome switch  700 . 
     To allow air particles to pass through the protective film (e.g., as part of the dome actuation process) while preventing contaminants from passing into channel  722 , protective film  750  can define a mesh having openings through which air can pass. The mesh can be treated to prevent non-air particles from passing through the mesh holds. For example, protective film  750  can include a hydrophobic, oleophobic, or other coating, or a chemical treatment selected for reducing permeability to particular elements. Protective film  750  can be constructed from any suitable material including, for example, plastic, a composite material, or expanded PFTE. The openings in the material (e.g., through which air can pass) can be uniform (e.g., a mesh defined by strands of material overlaid in a regular pattern) or arbitrary, as long as the openings are less than a maximum size selected to prevent particles or contaminants from entering the dome switch. 
       FIG. 8  is a schematic view of an illustrative dome switch having a protective mesh over vents adjacent to the dome in accordance with one embodiment of the invention. Dome switch  800  can include film layer  810  placed over dome  812  and flex circuit  830 . Film layer  810  can include vents  814  for allowing air to escape from underneath dome  812 . To prevent contaminants from entering the dome switch through vents  814 , protective film  850  can be applied over the vents. Protective film  850  can include a permeable mesh that allows air to be expelled from the dome while preventing liquids and other debris from reaching the dome and the flex circuit. 
     Although this discussion described the use of a channel and a protective film in the context of a dome switch, it will be understood that a channel and a protective film can be applied over any suitable electronic component, such as a pressure transducer, microphone, speaker, or other component requiring the displacement of a volume of air to operate. In some embodiments, a channel and a protective film can provide a closed path to a target volume of air or to an acoustic volume. 
       FIG. 9  is a flowchart of an illustrative process for constructing a dome switch having a channel for remote venting in accordance with one embodiment of the invention. Process  900  can begin at step  902 . At step  904 , a flex circuit can be defined. For example, a flex circuit having contact pads for a dome switch can be defined. In some embodiments, the flex circuit can include an extension that may form a portion of a channel used to remotely vent a dome switch. At step  906 , a spacer can be applied to the flex circuit. The spacer can be coupled to the flex circuit using an adhesive, and define an external periphery for the dome switch. For example, the spacer can be provided around the periphery of the dome, and along side portions of a flex circuit extension to form the side walls of a channel. In some embodiments, the spacer can be formed from a double-sided adhesive. At step  908 , a channel can be defined in the spacer. For example, a channel can be cut in the spacer layer. As another example, the channel can be defined as a portion between side walls of the spacer. 
     At step  910 , an impermeable film layer can be applied over the spacer. For example, a plastic film can be adhered to the spacer. In some embodiments, the plastic film layer can be placed over a dome positioned on the flex circuit, or the plastic film can incorporate a dome. At step  912 , an opening can be defined in the channel so that air from the volume between the dome and the flex circuit can be expelled from the dome through the channel when the dome is actuated. The opening can be provided in any suitable component of the dome switch including, for example, in the flex circuit, film layer, or in the spacer. In some embodiments, a channel can include several openings. In some cases, an addition protective layer can be placed over one or more of the openings to prevent contaminants from entering the channel while allowing air to pass through the protective layer. Process  900  can then end at step  914 . 
       FIG. 10  is a flowchart of an illustrative process for providing a remotely venting dome switch in accordance with one embodiment of the invention. Process  1000  can begin at step  1002 . At step  1004 , a dome can be placed over conductive pads of a circuit. For example, a dome can be placed over a circuit, such that a periphery of the dome is in contact with a first conductive pad, and the dome can come into contact with a second conductive pad when it is depressed and partially inverted. At step  1006 , a channel can be aligned with the dome to provide a fluid communication between the channel and the dome. The channel can be constructed using different approaches including, for example, from free space between different spacer elements. The channel can include a proximal opening in the vicinity of the dome, and a distal opening away from the dome. At step  1008 , the dome can be sealed over the circuit to prevent air from reaching underneath the dome except through the channel. For example, a film can be applied to the dome to hermetically seal the dome to the circuit. In some embodiments, the film can be applied over the spacer to provide a single path through the channel between the device environment and the dome. Process  1000  can then end at step  1010 . 
     The above described embodiments of the present invention are presented for purposes of illustration and not of limitation, and the present invention is limited only by the claims which follow.