PATENT DOCUMENT

Publication Number: US-9335355-B2
Application Number: US-201313787669-A
Country: US
Kind Code: B2

Title: Electronic device with liquid contact sensors

Abstract:
Electronic devices may be accidentally exposed to liquid during operation. To detect liquid intrusion events, an electronic device may be provided with one or more electronic liquid contact sensors. The liquid contact sensors may have electrodes. Control circuitry may make measurements across the electrodes such as resistance and capacitance measurements to detect the presence of liquid. Liquid contact sensor data may be maintained in a log within storage in the electronic device. The liquid contact sensor data can be used to display information for a user of the electronic device or can be loaded onto external equipment for analysis. Liquid contact sensor electrodes may be formed from metal traces on substrates such as printed circuits, from contacts in a connector, from contacts on an integrated circuit, or from other conductive electrode structures.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 an electronic device housing; 
 a liquid contact sensor mounted in the electronic device housing, wherein the liquid contact sensor has first and second electrodes and first and second resistors coupled in series between the second electrode and ground; and 
 control circuitry in the electronic device housing that is coupled to the electrodes, wherein the control circuitry is configured to monitor liquid exposure events with the liquid contact sensor in which moisture enters the electronic device housing, and wherein the control circuitry monitors the voltage across the first resistor. 
 
     
     
       2. The electronic device defined in  claim 1  further comprising:
 storage in which time-stamped liquid contact sensor data from the liquid contact sensor is stored. 
 
     
     
       3. The electronic device defined in  claim 1  wherein the liquid contact sensor is one of a plurality of liquid contact sensors within the electronic device housing, the electronic device further comprising:
 multiplexing circuitry in the control circuitry that is coupled to each of the plurality of liquid contact sensors. 
 
     
     
       4. The electronic device defined in  claim 1  further comprising:
 a printed circuit, wherein the electrodes are formed on the printed circuit. 
 
     
     
       5. The electronic device defined in  claim 4  wherein the electrodes include interdigitated fingers. 
     
     
       6. The electronic device defined in  claim 4  wherein the printed circuit comprises a multilayer printed circuit, wherein the multilayer printed circuit has internal traces that extend to an edge of the printed circuit, and wherein the electrodes are formed from exposed edge portions of the internal traces on the edge of the printed circuit. 
     
     
       7. The electronic device defined in  claim 1  wherein the electrodes include metal traces formed from multiple layers of metal. 
     
     
       8. The electronic device defined in  claim 1  wherein the electrodes are separated by a gap, the liquid contact sensor further comprising a hydrophilic pad in the gap. 
     
     
       9. The electronic device defined in  claim 1  further comprising a printed circuit covered with at least one coating, wherein the coating has an opening, and wherein the electrodes overlap the opening. 
     
     
       10. The electronic device defined in  claim 9  wherein the coating includes a solder mask layer and a hydrophobic layer on the solder mask layer. 
     
     
       11. The electronic device defined in  claim 1  further comprising a flexible printed circuit, wherein the electrodes comprise metal traces on the flexible printed circuit. 
     
     
       12. The electronic device defined in  claim 11 , wherein the flexible printed circuit comprises a curved portion, and wherein the metal traces are formed on the curved portion. 
     
     
       13. The electronic device defined in  claim 1  further comprising a connector having contacts, wherein the electrodes are formed from a pair of the contacts. 
     
     
       14. The electronic device defined in  claim 1  wherein the electrodes comprise integrated circuit contacts that include solder. 
     
     
       15. The electronic device defined in  claim 1  wherein the electronic device housing has a connector port and wherein the liquid contact sensor is mounted adjacent to the connector port. 
     
     
       16. The electronic device defined in  claim 1  further comprising:
 a printed circuit; and 
 an integrated circuit mounted to the printed circuit, wherein the liquid contact sensor is located adjacent to the integrated circuit on the printed circuit. 
 
     
     
       17. The method defined in  claim 1 , wherein the second resistor limits an amount of current that flows between the first and second electrodes when moisture contacts the first and second electrodes. 
     
     
       18. A method, comprising:
 gathering liquid contact sensor measurement data with a plurality of liquid contact sensors in a portable electronic device; 
 storing the liquid contact sensor measurement data in storage in the portable electronic device; 
 based on the liquid contact sensor measurement data from the plurality of liquid contact sensors, determining a location in the portable electronic device that has been exposed to moisture; and 
 based on the determined location in the electronic device, deactivating at least one electronic component in the portable electronic device. 
 
     
     
       19. The method defined in  claim 18  wherein the portable electronic device comprises a device selected from the group consisting of: a portable computer, a cellular telephone, a media player, and a tablet computer, the method comprising:
 providing the stored liquid contact sensor data from the portable electronic device to external equipment for analysis. 
 
     
     
       20. The method defined in  claim 19  wherein the portable electronic device comprises a plurality of liquid contact sensors each of which has a respective pair of the liquid contact sensor electrodes and wherein gathering the liquid contact sensor data comprises using each of the plurality of liquid contact sensors to gather liquid contact sensor data. 
     
     
       21. The method defined in  claim 18  wherein the liquid contact sensor measurement data comprises time-stamped liquid contact sensor measurement data that is periodically gathered, and wherein the periodically gathered time-stamped liquid contact sensor measurement data is stored in storage in the portable electronic device. 
     
     
       22. The method defined in  claim 18 , wherein the plurality of electronic liquid contact sensors comprises a first electronic liquid contact sensor having a first sensitivity to moisture mounted at a first location in the electronic device and a second electronic liquid contact sensor having a second sensitivity to moisture mounted at a second location in the electronic device. 
     
     
       23. A portable electronic device, comprising:
 a housing; 
 a display in the housing; 
 a plurality of electronic liquid contact sensors in the housing; 
 an external connector port mounted in the housing, wherein at least one of the plurality of electronic liquid contact sensors has electrodes that are integrated into the external connector port; and 
 control circuitry coupled to the plurality of electronic liquid contact sensors, wherein the control circuitry and the electronic liquid contact sensors are configured to monitor for liquid intruding into the housing. 
 
     
     
       24. The portable electronic device defined in  claim 23  wherein the electronic liquid contact sensors each comprise electrodes and wherein at least some of the electrodes comprise metal traces on a printed circuit. 
     
     
       25. The portable electronic device defined in  claim 23  wherein the electronic liquid contact sensors each comprise electrodes and wherein at least some of the electrodes comprise pins in the external connector port. 
     
     
       26. The portable electronic device defined in  claim 23  further comprising:
 a flexible printed circuit; and 
 electrodes for the electronic liquid contact sensors that are formed on the flexible printed circuit. 
 
     
     
       27. The portable electronic device defined in  claim 23  wherein the electronic liquid contact sensors each comprise electrodes and wherein the electrodes are formed from exposed edge portions of metal traces embedded within a multilayer printed circuit. 
     
     
       28. The portable electronic device defined in  claim 23  wherein the control circuitry is configured to display information on the display in response to detecting liquid. 
     
     
       29. The portable electronic device defined in  claim 28  wherein the display comprises a cellular telephone touch screen display. 
     
     
       30. The portable electronic device defined in  claim 23  wherein the electronic liquid contact sensors each comprise electrodes, wherein at least some of the electrodes comprise metal traces on a printed circuit, and wherein at least some of the metal traces are covered by a layer of encapsulant. 
     
     
       31. The method defined in  claim 23 , wherein the external connector port is configured to mate with a corresponding external connector.

Description:
BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with liquid intrusion sensing capabilities. 
     Electronic devices such as computers and cellular telephones are often accidentally exposed to moisture. For example, a portable device may become wet when exposed to rain or when accidentally dropped in water. 
     It can be difficult to troubleshoot damaged electronic devices without knowledge of whether or not a device has been exposed to liquid. If care is not taken, wasteful repair attempts may be made on a permanently damaged device or a device that has not been exposed to damaging liquids may be needlessly scrapped without identifying a reparable fault. 
     Liquid contact indicators are available that are formed from dye-impregnated paper. When exposed to moisture, the dye will diffuse into the paper and give rise to a visible mark such as a red spot. This type of dye-based liquid contact indictor may be installed within an electronic device in a location that is visible from the exterior of a device, thereby allowing a technician to easily inspect the status of the indicator to determine whether or not the electronic device has been exposed to liquid. 
     Dye-based liquid contact indicators provide only limited information about liquid contact events and exhibit irreversible state changes. This can make it difficult or impossible to troubleshoot failures. It is also not possible for a device to take actions in real time in response to a state change in a dye-based liquid contact indictor. 
     It would therefore be desirable to be able to provide electronic devices with improved liquid contact detection capabilities. 
     SUMMARY 
     Electronic devices may be accidentally exposed to liquid during operation. To detect liquid intrusion events in which moisture enters the housing of an electronic device, the electronic device may be provided with one or more electronic liquid contact sensors. The liquid contact sensors may have electrodes. Control circuitry may make measurements across the electrodes such as resistance and capacitance measurements to detect the presence of liquid. 
     Liquid contact sensor data may be maintained in a log within storage in the electronic device. The liquid contact sensor data can be used to display information for a user of the electronic device and can be loaded onto external equipment for analysis. Corrective actions may be taken in real time in response to liquid detection. For example, sensitive electronic components within the electronic device can be powered down in response to liquid detection to prevent component damage. Liquid detection information may also be used for debugging. For example, information from liquid contact sensors can be used in determining whether an electronic device is reparable or should be replaced and can be used in improving future device designs for enhanced immunity to liquid exposure damage. 
     Liquid contact sensor electrodes may be formed from metal traces on substrates such as printed circuits. For example, a pair of electrodes may be formed on the surface of a rigid or flexible printed circuit. Electrode structures may be provided with interdigitated fingers to enhance sensitivity. In multilayer printed circuits, electrodes may be formed from exposed edge portions of embedded metal traces. In electronic devices with connectors such as data port connectors, liquid contact sensor electrodes may be formed from connector pins. Integrated circuit contacts may also be used as liquid contact sensor electrodes. 
     Further features, their nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device such as a laptop computer with liquid contact sensor structures in accordance with an embodiment. 
         FIG. 2  is a perspective view of an illustrative electronic device such as a handheld electronic device with liquid contact sensor structures in accordance with an embodiment. 
         FIG. 3  is a perspective view of an illustrative electronic device such as a tablet computer with liquid contact sensor structures in accordance with an embodiment. 
         FIG. 4  is a perspective view of an illustrative electronic device such as a computer display with liquid contact sensor structures in accordance with an embodiment. 
         FIG. 5  is a schematic diagram of an illustrative electronic device of the type that may be provided with liquid contact sensor structures in accordance with an embodiment. 
         FIG. 6  is a diagram of an illustrative electronic liquid contact sensor and associated control circuitry for use in an electronic device in accordance with an embodiment. 
         FIG. 7  is a circuit diagram showing how sensing and analog-to-digital converter circuitry in an integrated circuit may be used in monitoring an electronic liquid contact sensor in an electronic device in accordance with an embodiment. 
         FIG. 8  is a circuit diagram showing how capacitance-to-voltage converter circuitry may be used in processing signals from an electronic liquid contact sensor in an electronic device in accordance with an embodiment. 
         FIG. 9  is a perspective view of an illustrative substrate such as a printed circuit having sensing circuitry coupled to liquid contact sensor electrodes in accordance with an embodiment. 
         FIG. 10  is a perspective view of an illustrative substrate such as a printed circuit having sensing circuitry coupled to a liquid contact sensor structure having sensor electrodes with interdigitated fingers in accordance with an embodiment. 
         FIG. 11  is a cross-sectional side view of an illustrative liquid contact sensor electrode formed from multiple layers of conductive material on a substrate such as a printed circuit board in accordance with an embodiment. 
         FIG. 12  is a perspective view of an illustrative liquid contact sensor structure having two electrodes and a hydrophilic coating covering a portion of a substrate that is located between the two electrodes in accordance with an embodiment. 
         FIG. 13  is a cross-sectional side view of an illustrative liquid contact sensor structure having a hydrophilic coating and sensor electrodes formed in openings in a solder mask layer and a hydrophobic overcoat layer in accordance with an embodiment. 
         FIG. 14  is a perspective view of an illustrative liquid contact sensor having sensor electrodes formed from portions of embedded metal traces that are exposed along the edge of a substrate such as printed circuit in accordance with an embodiment. 
         FIG. 15  is a perspective view of an illustrative liquid contact sensor structure formed from interdigitated sensor electrodes on a substrate such as a flexible printed circuit substrate mounted on a support structure in accordance with an embodiment. 
         FIG. 16  is a perspective view of an illustrative connector of the type that may have connector contacts that serve as liquid contact sensor electrodes for a liquid contact sensor in accordance with an embodiment. 
         FIG. 17  is a perspective view of an illustrative component such as an integrated circuit having contacts such as solder pads with solder ball joints that may be used as liquid contact sensor electrodes in a liquid contact sensor in accordance with an embodiment. 
         FIG. 18  is a circuit diagram of an illustrative array of liquid sensors and associated multiplexing circuitry that may be used to route signals from the sensors to control circuitry within an electronic device in accordance with an embodiment. 
         FIG. 19  is a top view of an electronic device in which liquid contact sensors have been located adjacent to areas that may potentially experience moisture intrusion and areas that contain sensitive components in accordance with an embodiment. 
         FIG. 20  is a diagram showing how external equipment such as a computer may be used to gather liquid contact sensor data from electronic liquid contact sensor structures in an electronic device over wired or wireless paths in accordance with an embodiment. 
         FIG. 21  is a flow chart of illustrative steps involved in gathering and processing liquid contact sensor data from one or more electronic liquid contact sensors in an electronic device in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Illustrative electronic devices having one or more electronic liquid contact sensors are shown in  FIGS. 1, 2 ,  3 , and  4 . 
     Electronic device  10  of  FIG. 1  has the shape of a laptop computer and has upper housing  12 A and lower housing  12 B with components such as keyboard  16  and touchpad  18 . Device  10  has hinge structures  20  (sometimes referred to as a clutch barrel) to allow upper housing  12 A to rotate in directions  22  about rotational axis  24  relative to lower housing  12 B. Display  14  is mounted in upper housing  12 A. Upper housing  12 A, which may sometimes referred to as a display housing or lid, is placed in a closed position by rotating upper housing  12 A towards lower housing  12 B about rotational axis  24 . 
       FIG. 2  shows an illustrative configuration for electronic device  10  based on a handheld device such as a cellular telephone, music player, gaming device, navigation unit, or other compact device. In this type of configuration for device  10 , housing  12  has opposing front and rear surfaces. Display  14  is mounted on a front face of housing  12 . Display  14  may have an exterior layer that includes openings for components such as button  26  and speaker port  28 . 
     In the example of  FIG. 3 , electronic device  10  is a tablet computer. In electronic device  10  of  FIG. 3 , housing  12  has opposing planar front and rear surfaces. Display  14  is mounted on the front surface of housing  12 . As shown in  FIG. 3 , display  14  has an external layer with an opening to accommodate button  26 . 
       FIG. 4  shows an illustrative configuration for electronic device  10  in which device  10  is a computer display or a computer that has been integrated into a computer display. With this type of arrangement, housing  12  for device  10  is mounted on a support structure such as stand  27 . Display  14  is mounted on a front face of housing  12 . 
     The illustrative configurations for device  10  that are shown in  FIGS. 1, 2, 3, and 4  are merely illustrative. In general, electronic device  10  may be a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. 
     Housing  12  of device  10 , which is sometimes referred to as a case, is formed of materials such as plastic, glass, ceramics, carbon-fiber composites and other fiber-based composites, metal (e.g., machined aluminum, stainless steel, or other metals), other materials, or a combination of these materials. Device  10  may be formed using a unibody construction in which most or all of housing  12  is formed from a single structural element (e.g., a piece of machined metal or a piece of molded plastic) or may be formed from multiple housing structures (e.g., outer housing structures that have been mounted to internal frame elements or other internal housing structures). 
     Display  14  may be a touch sensitive display that includes a touch sensor or may be insensitive to touch. Touch sensors for display  14  may be formed from an array of capacitive touch sensor electrodes, a resistive touch array, touch sensor structures based on acoustic touch, optical touch, or force-based touch technologies, or other suitable touch sensor components. 
     Display  14  for device  10  includes display pixels formed from liquid crystal display (LCD) components or other suitable image pixel structures. 
     A display cover layer may cover the surface of display  14  or a display layer such as a color filter layer or other portion of a display may be used as the outermost (or nearly outermost) layer in display  14 . The outermost display layer may be formed from a transparent glass sheet, a clear plastic layer, or other transparent member. 
     A schematic diagram of device  10  is shown in  FIG. 5 . As shown in  FIG. 5 , electronic device  10  includes control circuitry such as storage and processing circuitry  40 . Storage and processing circuitry  40  includes one or more different types of storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  40  is used in controlling the operation of device  10 . The processing circuitry may be based on a processor such as a microprocessor and other integrated circuits. 
     With one suitable arrangement, storage and processing circuitry  40  is used to run software on device  10  such as internet browsing applications, email applications, media playback applications, operating system functions, software for capturing and processing images, software for implementing functions associated with gathering and processing sensor data, etc. 
     Input-output circuitry  32  is used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. 
     Input-output circuitry  32  can include wired and wireless communications circuitry  34 . Communications circuitry  34  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Input-output circuitry  32  of  FIG. 5  includes input-output devices  36  such as buttons, joysticks, click wheels, scrolling wheels, a touch screen such as display  14 , other touch sensors such as track pads or touch-sensor-based buttons, vibrators, audio components such as microphones and speakers, image capture devices such as a camera module having an image sensor and a corresponding lens system, keyboards, status-indicator lights, tone generators, key pads, and other equipment for gathering input from a user or other external source and/or generating output for a user. 
     Sensors  38  of  FIG. 5  may include an ambient light sensor for gathering information on ambient light levels, a proximity sensor, an accelerometer, and other sensors. As shown in  FIG. 5 , sensors  38  may include one or more electronic liquid contact sensors  42 . Liquid contact sensors  42  may include electrodes that are coupled to control circuitry in device  10  such as circuitry  40 . The control circuitry may include resistance measurement circuitry for making resistance measurements across the electrodes, circuitry for making capacitance measurements across the electrodes, circuitry for digitizing analog sensor measurements, multiplexing circuitry that allows sensor signals to be gathered from more than one sensor  42 , communications circuitry for transmitting sensor data to other circuitry that is internal or external to device  10 , and/or processing circuits for processing sensor data and taking suitable action. 
     Using liquid contact sensors  42 , device  10  may detect situations in which circuitry within device  10  should be shut down to minimize or avoid potential damage due to the presence of excessive moisture and/or may detect situations in which moisture has likely damaged components within device  10 . Information on moisture damage may be used to troubleshoot damaged devices, may be used to improve future device designs, etc. 
       FIG. 6  is a diagram of an illustrative liquid contact sensor being used to detect moisture in device  10 . Liquid contact sensor  42  of  FIG. 6  has electrodes  44  and  46 . Electrodes  44  and  46  are formed from conductive materials such as metal. As an example, electrodes  44  and  46  may be formed from patterned metal traces on a substrate such as a plastic carrier, glass or ceramic layer, or a printed circuit substrate such as a rigid printed circuit board (e.g., a printed circuit formed from fiberglass-filled epoxy) or a flexible printed circuit (e.g., a printed circuit formed from a flexible layer of polyimide or other sheet of flexible polymer). Electrodes  44  and  46  may also be formed using other conductive structures in device  10  such as housing structures, brackets, connectors, contacts in connectors (e.g., pins in a data port connector or audio jack connector), or other conductive structures. 
     Control circuitry  48  (e.g., circuitry such as circuitry  40  of  FIG. 5 ) may be coupled to liquid contact sensor electrodes  44  and  46  using paths such as conductive lines  50  and  52 . Electrodes  44  and  46  may be separated by a gap G. Air, plastic, printed circuit board material, or other dielectric may be present in gap G between electrodes  44  and  46 . Control circuitry  48  may measure a resistance value, a capacitance value, or other electrical parameter associated with electrodes  44  and  46  to determine whether moisture is present in sensor  42 . For example, in the absence of moisture, a resistance of R 1  may be present across electrodes  44  and  46 . In the presence of a drop of liquid such as liquid  56  that bridges gap G, control circuitry  48  may measure a reduced resistance value of R 2  across electrodes  44  and  46 . As another example, control circuitry  48  may detect a change in capacitance across electrodes  44  and  46  when moisture is introduced (e.g., when moisture drop  56  bridging gap G is present and/or when a drop such as drop  54  on electrode  44  is present). By making periodic electrical measurements such as resistance and/or capacitance measurements on liquid contact sensor electrodes  44  and  46 , device  10  can monitor device  10  for exposure to moisture. 
       FIG. 7  is a circuit diagram showing illustrative control circuitry  48  for making resistance-based liquid contact sensor measurements. With the configuration of  FIG. 7 , power (e.g., direct-current power supply voltage Vcc) may be applied to electrode  44  through circuitry  62  (e.g., a diode and a control transistor or other suitable circuitry). In the absence of liquid, the resistance between electrodes  44  and  46  will be high (essentially infinite). In the presence of liquid, a reduced finite resistance value may be measured across electrodes  44  and  46  by circuitry  48 . 
     As shown in  FIG. 7 , electrode  46  may be coupled to integrated circuit  72  by current limiting resistor R 2 . Resistor R 2  may limit the maximum amount of current that flows between electrodes  44  and  46  in the presence of moisture, thereby preventing damage to circuitry  48 . If desired, components such as current limiting resistor R 2  may be incorporated into an integrated circuit such as integrated circuit  72 . The configuration of  FIG. 7  in which current limiting resistor R 2  has been implemented as a stand-alone discrete electrical component is merely illustrative. 
     Integrated circuit  72  may be an application-specific integrated circuit, a processor, or other suitable integrated circuit in device  10  (e.g., circuit  72  may be part of storage and processing circuitry  40 ). Integrated circuit  72  may receive power supply voltage Vcc from power management unit  58  (e.g., a power management unit integrated circuit) or, if desired the circuitry of power management unit  58  may be included in integrated circuit  72  as indicated schematically by power management unit circuitry  58 ′ of  FIG. 7  (i.e., circuitry  48  can be incorporated into a power management unit integrated circuit or other integrated circuit in device  10 ). 
     Sensing and analog-to-digital converter circuitry  66  may be coupled across current sensing resistor R 1 . When moisture is present across electrodes  44  and  46 , a current Is will flow through electrodes  44  and  46  and across resistor R 1 , producing a voltage drop of Is*R 1  across resistor R 1 . Circuitry  66  may include an amplifier or other circuitry coupled across resistor R 1  for measuring the voltage drop. Analog-to-digital converter circuitry within circuitry  66  may be used to digitize this measured voltage, thereby producing a digital output that is indicative of the resistance between electrodes  44  and  46 . 
     When no liquid is present on sensor  42 , the resistance measured by circuitry  48  will be high. When liquid is present on sensor  42 , the measured resistance will be low. Liquid contact sensor data (e.g., resistance measurements) from circuitry  66  may be passed to output path  70  using communications circuitry  68 . Output path  70  may be coupled to control circuitry  40  for internal processing in device  10  and/or may be coupled to communications circuitry  34  for conveying the liquid contact sensor data to external equipment. Communications circuitry  68  may be circuitry for handling serial communications (e.g., I 2 C serial bus circuitry or Universal Serial Bus circuitry), circuitry for handling parallel bus communications and/or other circuitry for transmitting liquid contact sensor measurements from circuitry  48  of  FIG. 7  (e.g., integrated circuit  72 ) to other circuitry in device  10 . 
       FIG. 8  is a circuit diagram of an illustrative liquid contact sensor circuit that makes capacitance measurements between electrodes  44  and  46  in sensor  42 . With the configuration of  FIG. 8 , integrated circuit  82  is coupled to sensor  42  using paths  50  and  52 . Integrated circuit  82  may be an application-specific integrated circuit, a processor, or other suitable integrated circuit in device  10  (e.g., part of storage and processing circuitry  40 ). If desired, multiple integrated circuits may be used in implementing the circuitry of circuit  82 . 
     Capacitance-to-voltage converter  74  or other capacitance sensing circuitry may be coupled across electrodes  44  and  46 . During operation, capacitance-to-voltage converter  74  measures how much capacitance is exhibited across electrodes  44  and  46  and will produce a corresponding voltage output. The capacitance across electrodes  44  and  46  will rise and fall depending on the moisture content in sensor  42 , thereby allowing circuitry  48  to determine whether or not sensor  42  has been exposed to liquid. 
     The voltage output of capacitance-to-voltage converter circuitry  74  is provided to analog-to-digital converter  76 . Analog-to-digital converter  76  digitizes the analog voltage output of circuitry  74  and provides a corresponding digital capacitance measurement signal to communications circuitry  78 . Liquid contact sensor data (e.g., capacitance measurements) from circuitry  76  may be passed to output path  80  using communications circuitry  78 . Communications circuitry  78  may be circuitry for handling serial communications (e.g., I 2 C serial bus circuitry or Universal Serial Bus circuitry), circuitry for handling parallel bus communications and/or other circuitry for transmitting liquid contact sensor measurements from circuitry  48  (e.g., integrated circuit  82 ) to control circuitry  40  and/or communications circuitry  32  in device  10 . 
     Sensor electrodes  44  and  46  may, if desired, be formed as metal contact pads on the surface of a substrate. This type of arrangement is shown in  FIG. 9 . As shown in  FIG. 9 , electrodes  44  and  46  may be formed on substrate  82 . Lines  50  and  52  electrically couple electrodes  44  and  46  to circuitry  48 . Lines  50  and  52  may be formed from surface traces on substrate  82  and/or from internal interconnect traces embedded within substrate  82 . 
     Substrate  82  may be formed from dielectric such as plastic, ceramic, glass, or other insulating material. For example, substrate  82  may be a plastic carrier, a rigid printed circuit board, or a flexible printed circuit. Sensors  44  and  46  may be formed from one or more layers of patterned metal on the surface of substrate  82 . For example, sensors  44  and  46  may be formed from one or more layers of metal traces patterned using photolithographic patterning equipment. If desired, multiple components such as one or more integrated circuits for circuitry  32  and  40  of  FIG. 5  may be mounted on substrate  82 . 
     As shown in  FIG. 10 , electrodes  44  and  46  may have interdigitated fingers to help enhance the sensitivity of liquid contact sensor  42 . In the example of  FIG. 10 , liquid contact sensor electrode  44  has four fingers  44 F that are interleaved with four corresponding fingers  46 F in liquid contact sensor electrode  46 . Liquid contact sensors with other numbers of fingers and/or fingers with different shapes (e.g., bends, etc.) may be used if desired. 
     Electrodes  44  and  46  may be formed from one or more layers of metal. Metal with high conductivity such as copper may be used to reduce electrode resistance. Metals such as gold may exhibit high corrosion resistance and may therefore be suitable for use in forming an exposed outer electrode layer. 
     A cross-sectional side view of a metal structure of the type that may be used in forming electrodes  44  and  46  and/or for conductive paths  50  and  52  is shown in  FIG. 11 . As shown in  FIG. 11 , metal trace  84  (e.g., electrode  44 , electrode  46 , conductive line  50 , and/or conductive line  52 ) may be formed from multiple metal layers such as metal layers M 1 , M 2 , and M 3 . Layers M 1 , M 2 , and M 3  may be deposited using physical vapor deposition, chemical vapor deposition, electrochemical deposition, or other suitable metal deposition techniques. Traces such as trace  84  may be patterned using photolithography (as an example). 
     Trace  84  may be formed on a substrate such as substrate  82  (e.g., a rigid printed circuit board, a flexible printed circuit, a plastic carrier, etc.). With one suitable arrangement, trace layer M 1  may be a high-conductivity metal such as copper, trace layer M 3  may be an inert metal coating such as gold, and trace layer M 2  may be formed from a metal such as nickel that serves as a barrier layer to prevent the gold of layer M 3  from migrating into the copper of layer M 1 . 
     If desired, electrodes formed from metal traces such as trace  84  or other conductive electrode structures may be encapsulated using a covering layer of insulating material such as a polymer layer (sometimes referred to as encapsulant or an encapsulant layer). The encapsulation layer may be formed from a dielectric material that conforms to the surface shape of the electrodes or may have other suitable shapes. Encapsulant may be dispensed in liquid form, by spraying, using spin-on processes, using physical vapor deposition, etc. Organic and/or inorganic materials may be used. As an example, layer M 3  of trace  84  may be formed from an organic or inorganic dielectric encapsulation layer instead of from a metal layer. The presence of an encapsulation layer on the surface of the electrode may help prevent the electrode from becoming damaged (e.g., due to oxidation from exposure to air, moisture, or other environmental contaminants). Even though the electrodes are covered with dielectric, control circuitry  48  such as capacitance-to-voltage converter  74  of  FIG. 8  may still make capacitance measurements using the electrodes to detect the presence of liquid. 
     As shown in  FIG. 12 , liquid contact sensor  42  may include structures such as pad  86 . Pad  86  may be located adjacent to electrodes  44  and  46 . For example, pad  86  may be located in gap G between electrodes  44  and  46 . Pad  86  may be formed from a hydrophilic material such as polyurethane. The presence of hydrophilic structure  86  may help enhance the sensitivity of liquid contact sensor  42  to moisture by ensuring that any moisture that is present in the vicinity of sensor  42  will be drawn between electrodes  44  and  46  for detection. If desired, part of the hydrophilic structure may be formed on top of portions of electrodes  44  and  46 . 
       FIG. 13  is a cross-sectional side view of sensor  42  in a configuration in which part of the metal traces used in forming electrodes  44  and  46  has been covered with a coating. As shown in  FIG. 13 , optional hydrophilic structure  86  may be located in gap G between electrodes  44  and  46 . Coating  88  may be formed from one or more layers of dielectric material. Electrodes  44  and  46  overlap opening  90  in coating  88 . Opening  90  in coating  88  may allow moisture to reach hydrophilic structure  86  and bridge electrodes  44  and  46 . 
     Coating  88  may include layers such as solder mask layer  94  and conformal coating  92 . Solder mask  94  may be formed from a layer of polymer such as epoxy or polyimide. Conformal coating  92  may be formed from a layer of material such as parylene. Conformal coating  92  may be hydrophobic, which may help drive moisture into opening  90  onto hydrophilic structures  86  and/or electrodes  44  and  46  of liquid contact sensor  42 . 
     There may be limited room available within device  10  for implementing liquid contact sensor  42 .  FIG. 14  shows how substrate area may be conserved by forming sensor  42  from electrode structures on an edge of substrate  82  such as edge  92 . As shown in  FIG. 14 , metal traces  50  and  52  may be formed as internal interconnect lines that are embedded within the interior of substrate  82  (e.g., traces  50  and  52  may be lines on an intermediate layer of a multilayer rigid printed circuit board or a multilayer flexible printed circuit). Electrodes  44  and  46  may be formed from the exposed edge portions of internal traces  50  and  52  that are present along printed circuit edge  92 . 
     In the illustrative configuration of  FIG. 15 , electrodes  44  and  46  for liquid contact sensor  42  have been formed from interdigitated finger structures on a flexible printed circuit substrate (substrate  82 ). Flexible printed circuit  82  of  FIG. 15  is mounted on support structure  94 . Support structures may be a plastic carrier, may be a metal bracket, may be an internal housing structure, may be formed from portions of a printed circuit board, may include an electrical component, may be a metal shielding can (e.g., an electromagnetic signal interference shielding can that covers an integrated circuit on a printed circuit), or may be other suitable structures for supporting flexible printed circuit  82 . 
     If desired, flexible printed circuit  82  may be used as a substrate for other components in device  10 . For example, electrical components such as integrated circuits and discrete components in circuitry  40  and  32  of  FIG. 5  may be mounted on flexible printed circuit  82  of  FIG. 15  in addition to using flexible printed circuit  82  of  FIG. 15  as a substrate for electrodes  44  and  46  in sensor  42 . 
     Electrodes  44  and  46  may be formed from contacts in a connector. Connector contacts, which are sometimes referred to as connector pins, may be formed from metal members, traces on support structures, or other metal contact structures. 
     As shown in  FIG. 16 , device  10  may have a connector port such as connector  102 . Connector  102  may be mounted in an opening such as opening  96  in housing  12 . Connector  102  may have one or more support structures such as protruding tongue member  98 . Tongue  98  may be formed from plastic or other dielectric. Contacts  100  may be formed from strips of metal, metal rods (e.g., cylindrical pins), metal traces on a support, or other connector contact structures. When connector  102  is coupled to a mating external connector, each of contacts  100  may make electrical connect with a corresponding contact in the external connector. 
     During use of device  10 , contacts  100  may serve as sensor electrodes for liquid contact sensor  42 . As an example, one of contacts  100  may serve as electrode  44  and another one of contacts  100  (e.g., an adjacent contact) may serve as electrode  46 . The contacts that are used in forming sensor electrodes may be normally unused contacts in connector  102  (as an example). By using contacts  100  within connector  102  as sensor electrodes, sensor  42  can detect whether connector  102  is being exposed to moisture. 
       FIG. 17  is a perspective view of an integrated circuit having contacts  100  (e.g., metal pads and solder balls or other solder joints coupled to corresponding pads on substrate  82 ). Contacts  100  may be used in forming electrodes in liquid contact sensor  42 . For example, one of contacts  100  may be used in forming electrode  44  and one of contacts  100  may be used in forming electrode  46 . Integrated circuit  104  may be used in forming sensor control circuitry  48  and/or other circuits in circuitry  32  and  40  of  FIG. 5  (as an example). To allow moisture to contact the electrodes formed from contacts  100  of integrated circuit  104 , the contacts  100  that are being used as sensor electrodes may be left exposed to the environment (e.g., by keeping them free of underfill sealant). 
     Different locations within device  10  may be subject to different types of moisture intrusion and may have varying levels of sensitivity to moisture. For example, a connector that is located within a port in housing  12  may sometimes be exposed to small amounts of moisture that can be tolerated without damaging device  10 . Other locations in device  10  such as printed circuit boards populated with electrical components may be sensitive to even minute amounts of liquid. Portions of device  10  near an opening in housing  12  may be subject to more frequent exposures to liquid than portions of device  10  that are located deep within the interior of housing  12 . 
     It may be desirable to gather information on liquid exposure events such as information on the amount of liquid that has entered device  10 , the location at which the liquid has entered device  10 , the time and date of each liquid intrusion, and information on the internal paths within device  10  along which liquid tends to flow. This information may be used in real time to take suitable actions such as turning off a display, turning of a sensitive integrated circuit, turning off other sensitive electrical components, or otherwise deactivating device circuitry  32  and/or  40 . Information on liquid intrusion events may also be logged for use in determining the cause of device failures and improving future product designs. 
     To gather comprehensive liquid intrusion data, it may be desirable to use multiple sensors within device  10 . As shown in  FIG. 18 , device  10  may have multiple liquid contact sensors  42  such as illustrative sensors S 1 , S 2 , S 3  . . . SN. Sensor control circuitry  48  may include multiplexing circuitry  106  that is coupled between liquid contact sensors  42  and sensing and analog-to-digital converter circuitry  108 . Sensing and analog-to-digital converter circuitry  108  may be used to make resistance measurements and/or capacitance measurements using sensors  42  that are indicative of the amount of liquid present at sensors  42 . Sensing and analog-to-digital converter circuitry  108  may digitize these liquid measurements. During operation, multiplexing circuitry  106  can switch each sensor  42  into use in sequence. This allows circuitry  108  to individually measure the amount of liquid present at each of sensors  42 . If desired, each sensor  42  may be provided with a corresponding block of sensor and analog-to-digital converter circuitry  108  and digital liquid readings from the analog-to-digital converter circuitry in each block may be multiplexed digitally. Communications circuitry  110  (e.g., serial and/or parallel bus communications circuitry) may be used to transmit liquid readings from sensors  42  to other control circuitry  40  in device  10  via path  112 . 
       FIG. 19  is a top view of device  10  showing how sensors may be located at different locations within housing  12 . In the example of  FIG. 19 , sensor S 1  is located at button  114  (e.g., a ringer switch button or volume button), sensor S 2  is located adjacent to sleep button  116 , sensor S 3  is located near menu button  26  so that liquid intrusion events at menu button  26  can be monitored, sensor S 4  is located at connector  102 , and sensor S 5  is located on printed circuit  82  adjacent to integrated circuit  118 . With this type of arrangement, liquid intrusion events of the type that may cause damage to device  10  can be monitored in detail. For example, a liquid intrusion event that exposes a sensitive component such as integrated circuit  118  to moisture can be detected, a liquid intrusion event that causes liquid to flow past connector  102  and sensor S 4  before reaching button  26  and sensor S 3  can be detected, liquid intrusion events that affect button  114  and sensor  42  without affecting button  116  and sensor S 2  (or vice versa) may be detected, liquid intrusion events in which moisture is detected nearly simultaneously at all sensors S 1 , S 2 , S 3 , S 4 , and S 5  may be detected, and other types of liquid intrusion events can be detected. By analyzing the data from these different types of events, the causes of different types of failures can be determined and design improvements can be made. 
       FIG. 20  is a system diagram showing how data on liquid exposure may be conveyed from device  10  to external equipment  120  using paths such as wired path  122  and wireless path  124 . Path  122  may be a serial bus cable or other wired path. Wireless path  124  may be a wireless local area network path such as an IEEE 802.11 path (as an example). External equipment  120  may be based on a computer (e.g., a portable computer), a tablet computer, a handheld device, or other electronic equipment. Equipment  120  may contain control circuitry  126  such as one or more processors and storage devices. Displays and other input-output circuitry  128  may be used to present information to a user of equipment  120 . For example, external equipment  120  may receive information from device  10  indicating that one of the liquid contact sensors in device  10  has detected exposure of device  10  to liquid. Upon receiving this information, device  10  may use control circuitry  126  and a display or other input-output device  128  to inform a user of equipment  120  (e.g., a technician) that device  10  has experienced liquid exposure. The technician may then take appropriate action (e.g., by repairing the portion of device  10  that was exposed to liquid, by replacing device  10  with a new device, etc.). The received data may also be used in performing failure analysis on device  10 . 
       FIG. 21  is a flow chart of illustrative steps involved in using electrical liquid contact sensors to gather liquid exposure data and taking appropriate actions based on the gathered data. 
     At step  140 , control circuitry in device  10  can use one or more liquid contact sensors  42  to gather data indicative of how much each sensor  42  has been exposed to liquid. In response to detecting liquid exposure, device  10  may take action at step  142 . As an example, device  10  may shut off a display, integrated circuit, or other electrical components that can be damaged when operating while moist. Device  10  (e.g., a cellular telephone with a touch screen or other display) may display a warning message to the user of device  10  such as “device shutting down to prevent damage due to liquid exposure, please have this device serviced”. Device  10  may also take actions such as sounding an audible alert, transmitting a wireless or wired message to computing equipment at a support center or other online destination, informing the user or others of the liquid exposure event using other techniques, etc. 
     At step  144 , the liquid contact sensor data that has been gathered during step  140  may be stored in a sensor log(e.g., by storing the sensor data within storage in circuitry  40 ). The stored data may be time stamped (e.g., time and data information that is indicative of the time and data when the liquid exposure event was detected may be stored in conjunction with the liquid contact sensor data so that a log of time-stamped liquid contact sensor data is maintained for future analysis). 
     As indicated by line  146 , processing may then loop back to step  140  so that additional data can be gathered from the one or more sensors  42  in device  10 . If the sensors dry out (e.g., because moisture exposure levels were sufficiently low to allow the moisture to evaporate from sensors  42 ) and if device  10  was undamaged, device  10  can continue to operate normally and sensors  42  may be used to monitor for subsequent liquid exposure events. 
     When a technician desires to retrieve the logged liquid contact sensor data from device  10 , the technician can use external equipment  120  to form a communications link with device  10  such as link  122  or link  124  of  FIG. 20 . Equipment  120  may then receive the sensor data from the control circuitry in device  10  (step  148 ) for processing. During processing operations, equipment  120  can analyze the liquid contact information from sensors  42  to determine whether device  10  was exposed to liquid, how much liquid device  10  was exposed to at each sensor location, the time and date of each exposure, the path taken by the liquid through device  12  (e.g., the route along which the liquid flowed as determined by mapping out the order of liquid exposure at each sensor), and other information about the nature of the liquid contact within device  10 . This information can be used to determine how to repair device  10 , whether device  10  should be scrapped or repaired, and can be used in enhancing future device designs to resist damage from liquid exposure. If desired, data processing operations at step  148  may be performed using control circuitry  40  in device  10  (e.g., so that data on liquid exposure can be presented to a user on display  14 ). 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20130306
Publication Date: 20160510
Grant Date: 20160510
Priority Date: 20130306
Inventors: MENZEL BRIAN C.
KEELER KEVIN M.
HUANG JIM Z.
MISHKANIAN PARVIZ
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F1/1613", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1613", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R27/2605", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01R27/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1613", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R27/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R27/2605", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 51487083