Compact optical proximity sensor with ball grid array and windowed substrate

Various embodiments of a compact optical proximity sensor with a ball grid array and windowed or apertured substrate are disclosed. In one embodiment, the optical proximity sensor comprises a printed circuit board (“PCB”) substrate comprising an aperture and a lower surface having electrical contacts disposed thereon, an infrared light emitter and an infrared light detector mounted on an upper surface of the substrate, an integrated circuit located at least partially within the aperture, a molding compound being disposed between portions of the integrated circuit and substrate, an ambient light detector mounted on an upper surface of the integrated circuit, first and second molded infrared light pass components disposed over and covering the infrared light emitter and the infrared light detector, respectively, and a molded infrared light cut component disposed between and over portions of the first and second infrared light pass components.

FIELD OF THE INVENTION

Various embodiments of the inventions described herein relate to the field of proximity sensors, and components, devices, systems and methods associated therewith.

BACKGROUND

Optical proximity sensors, such as the AVAGO TECHNOLOGIES™ HSDL-9100 surface-mount proximity sensor, the AVAGO TECHNOLOGIES™ APDS-9101 integrated reflective sensor, the AVAGO TECHNOLOGIES™ APDS-9120 integrated optical proximity sensor, and the AVAGO TECHNOLOGIES™ APDS-9800 integrated ambient light and proximity sensor, are known in the art. Such sensors typically comprise an integrated high efficiency infrared emitter or light source and a corresponding photodiode or light detector, and are employed in a large number of hand-held electronic devices such as mobile phones, Personal Data Assistants (“PDAs”), laptop and portable computers, portable and handheld devices, amusement and vending machines, industrial automation machinery and equipment, contactless switches, sanitary automation machinery and equipment, and the like.

Referring toFIG. 1, there is shown a prior art optical proximity sensor10comprising infrared light emitter16, light emitter driving circuit51, light detector or photodiode12, light detector sensing circuit53, metal housing or shield18with apertures52and54, and object to be sensed60. Light rays15emitted by emitter16and reflected as light rays19from object60(which is in relatively close proximity to optical proximity sensor10) are detected by photodiode12and thereby provide an indication that object60is close or near to sensor10.

As further shown inFIG. 1, optical proximity sensor10further comprises metal housing or shield18formed of metal and comprising apertures52and54located over light emitter16and light detector12, respectively, such that at least a first portion of light15emitted by light detector12passes through aperture55, and at least a second portion of the first portion19of light reflected from object50in proximity to sensor10passes through aperture57for detection by light detector12. As shown, metal housing or shield18may further comprise first and second modules61and63within which light emitter16and light detector12are disposed, respectively. The first and second modules61and63comprise adjoining optically opaque metal inner sidewalls25to provide optical isolation between first and second modules61and63.

Many optical proximity sensors generally include a metal shield, such as shield or housing18of the type shown inFIG. 1, to provide optical isolation between light emitter16and light detector or photodiode12so that undesired optical cross-talk between emitter16and detector12is minimized. See, for example, the Data Sheets corresponding to the AVAGO TECHNOLOGIES™ APDS-9120 Integrated Optical Sensors Preliminary Datasheet and the AVAGO TECHNOLOGIES™ APDS-9800 Integrated Ambient Light and Proximity Sensors Preliminary Datasheet, each of which is hereby incorporated by reference herein, each in its respective entirety.

FIG. 2shows a prior art optical proximity sensor10with metal shield or housing18. The optical proximity sensor shown inFIG. 2is an AVAGO TECHNOLOGIES™ APDS-9120 Integrated Optical Proximity Sensor, which contains a molded plastic substrate11upon which are mounted LED16and light detector or photodiode12. Single-piece metal shield18covers LED16and light detector or photodiode12and contains a downwardly projecting light barrier65disposed therebetween (not shown inFIG. 2). Electrical contacts17provide a means to establish electrical connections between proximity sensor10and external devices. In the APDS-9120 optical proximity sensor, metal shield18is formed and thinned using conventional metal stamping techniques, and is affixed to the underlying plastic substrate11by gluing. The APDS-9120 sensor has an areal footprint of only 4 mm by 4 mm, and thus is quite small.

FIG. 3shows a prior art optical proximity sensor10with a more complicated metal shield or housing18than that ofFIG. 2. The optical proximity sensor shown inFIG. 3is an AVAGO TECHNOLOGIES™ APDS-9800 Integrated Ambient Light and Proximity Sensor, which contains a printed circuit board (“PCB”) substrate11upon which are mounted LED16, light detector or photodiode12, and ambient light sensor14. The two-piece metal shield18covers LED16, light detector or photodiode12, and ambient light sensor14and contains a downwardly projecting light barrier65disposed therebetween. In the APDS-9800 optical proximity sensor, metal shield18, being of a considerably more complicated shape and geometry than that ofFIG. 2, is formed and thinned using more advanced progressive metal stamping techniques, and must be hand-fitted and attached to the underlying PCB by gluing to ensure proper alignment and fit.

As will now be seen, at least some optical proximity sensors of the prior art rely upon the use of an externally mounted metal shield18, which is required to reduce the amount of crosstalk or interference that might otherwise occur between LED16and light detector12, as well as to help increase the detection distance of the device. Metal shields18are quite small, however, making them difficult to manufacture in high volumes, and thus expensive to fabricate. Such metal shields18also generally require expensive automated equipment to attach same to sensors10in a mass production setting. Moreover, the quality of metal shields18often varies, and issues commonly arise with suppliers being unable to meet the tight dimensional tolerances required for such small devices. Metal shields18can also detach from sensor10, thereby adding another failure point for sensor10.

In addition, the commercial marketplace demands ever smaller portable electronic devices. This of course means there exists a motivation to make optical proximity sensors ever smaller. As optical proximity sensors become smaller, it becomes increasingly difficult to manufacture and attach the aforementioned metal shields to the sensors in a mass production setting. The metal shields themselves also add to the bulk and volume of the resulting sensor or package.

What is need is an optical proximity sensor design that eliminates the need to include a metal shield18, but which retains high crosstalk and interference rejection characteristics so that an optical proximity sensor can be provided that features improved performance, lower cost, increased manufacturability and improved reliability. What is also needed is a smaller optical proximity sensor.

SUMMARY

In some embodiments, there is provided an optical proximity sensor comprising a printed circuit board (“PCB”) substrate comprising an aperture and a lower surface having electrical contacts disposed thereon, an infrared light emitter and an infrared light detector mounted on an upper surface of the substrate, an integrated circuit located at least partially within the aperture, a molding compound being disposed between portions of the integrated circuit and substrate, an ambient light detector mounted on an upper surface of the integrated circuit, first and second molded infrared light pass components disposed over and covering the infrared light emitter and the infrared light detector, respectively, and a molded infrared light cut component disposed between and over portions of the first and second infrared light pass components.

In other embodiments, there is provided a method making an optical proximity sensor comprising providing a printed circuit board (“PCB”) substrate comprising an aperture and a lower surface having electrical contacts disposed thereon, mounting an infrared light emitter and an infrared light detector on an upper surface of the substrate, positioning an integrated circuit at least partially within the aperture, placing a molding compound between portions of the integrated circuit and substrate, mounting an ambient light detector on an upper surface of the integrated circuit, molding first and second infrared light pass components over and covering the infrared light emitter and the infrared light detector, respectively, and molding an infrared light cut component between and over portions of the first and second infrared light pass components.

Further embodiments are disclosed herein or will become apparent to those skilled in the art after having read and understood the specification and drawings hereof.

The drawings are not necessarily to scale. Like numbers refer to like parts or steps throughout the drawings, unless otherwise noted.

DETAILED DESCRIPTIONS OF SOME PREFERRED EMBODIMENTS

Referring toFIG. 4, there is shown a conventional optical proximity sensor known in the prior art which comprises substrate11and metal shield18. Integrated circuit35, ambient light detector14, infrared light detector12and infrared light emitter16are mounted on substrate11. Optically transmissive molding material1is molded over integrated circuit35, ambient light detector14, infrared light detector12and infrared light emitter16. Slot72separates first portion of substrate11from second portion of substrate11. When metal shield18is placed over and attached to the lower assembly containing substrate11, integrated circuit35, ambient light detector14, infrared light detector12and infrared light emitter16, barrier25fits within slot72and inhibits the transmission of light originating from infrared light emitter16from reaching infrared light detector12. Optical proximity sensor10shown inFIG. 4suffers form many of the problems and drawbacks discussed above in connection with the prior art devices shown inFIGS. 1 through 3.

FIG. 5shows an optical proximity sensor10comprising light emitter16mounted on substrate11and separated from light detector12by optically transmissive material21, which is a single mold two-part epoxy or transfer molding compound. As shown inFIG. 4, while light rays15are transmitted through material21, other reflected, diffracted or refracted IR radiation19can leak across to light detector12through single mold compound21, which manifests itself as undesired crosstalk or interference between light emitter16and light detector12, thereby degrading the performance of proximity sensor10.

As further shown inFIG. 6, the amount of reflected, diffracted or refracted IR radiation19and undesired crosstalk or interference between light emitter16and light detector12is typically exacerbated by the presence of window23, which in some applications is provided as part of the portable or other type of electronic device in which proximity sensor10is housed and mounted.

As shown inFIG. 7, the problems arising from undesired crosstalk or interference caused by reflected, diffracted or refracted IR radiation19may be reduced by disposing a metal light barrier25between light emitter16and light detector12. Providing such a metal barrier25in proximity sensor10, however, presents problems respecting increased manufacturing costs and complexity.

Referring now toFIGS. 8 through 19, there is shown one embodiment of optical proximity sensor10and its various components during various stages of assembly. The complete optical proximity sensor of such an embodiment is shown inFIGS. 17,18and19. As will become apparent, the embodiment of optical proximity sensor10shown inFIGS. 17,18and19overcomes many of the problems associated with prior art optical proximity sensors by completely eliminating the need for a metal shield, reducing the overall size, volume and footprint of optical proximity sensor10, and reducing manufacturing and material costs associated therewith. Many other advantages of the embodiment of the optical proximity sensor10illustrated inFIGS. 8 through 19will become apparent to those skilled in the art upon having read, understood and considered the present specification and drawings.

Referring now toFIG. 8, there is shown a printed circuit board (“PCB”) substrate11having central aperture65formed therethrough. Tape63having a lower sticky or adhesive surface is placed over upper surface67of substrate11and attached temporarily thereto as shown inFIG. 9. Next, substrate11is flipped over and integrated circuit35, which is preferably configured to fit conformably within aperture65, is placed within aperture65such that an upper thereof engages and is held in contact with the sticky or adhesive lower surface of tape63. In such a manner, integrated circuit35is held within aperture35while wires73are bonded to integrated circuit35and corresponding wire bond pads74disposed on lower surface69of substrate11.

Note that while in one embodiment substrate11comprises conventional PCB materials and structure, substrate11may also comprise any one or more of KAPTON™, fiberglass, glass, ceramic, polyimide, polyimide film, a polymer, an organic material, a flex circuit material, epoxy, epoxy resin, a printed circuit board material, PTFE and glass, PTFE and ceramic, glass and ceramic, thermoset plastic, and plastic. In one embodiment substrate11is a printed circuit board having traces, wire bond pads and/or vias disposed thereon or therein.

FIG. 11shows proximity sensor10after bottom portions of integrated circuit35and corresponding wires73and wire bond pads74have been encapsulated, overmolded or covered with appropriate molding compound75such as DuPont™ KAPTON™ polyimide, epoxy, plastic, a polymer or any other suitable molding compound. Molding compound75covers and protects the underside of integrated circuit35and the various electrical connections located thereon, and additionally fixedly or rigidly attached integrated circuit35to the underside of substrate11.

FIGS. 12A and 12Bshow top perspective and top plan views of substrate11of optical proximity sensor10after tape63has been removed or delaminated from upper surface67. As shown, an upper surface of integrated circuit35is flush with upper surface67of substrate11. Because integrated circuit35is located within aperture65of substrate11and is not mounted atop substrate11in conventional fashion, substantial volume reduction is achieved in proximity sensor10with respect to prior art devices. As further shown inFIGS. 12A and 12B, upper surface67of substrate11has mounting pads or regions77and79formed thereon, which are configured to receive infrared light detector12and infrared light emitter16thereon, respectively.FIG. 13shows substrate11and optical sensor10after infrared light detector12and infrared light emitter16have been die-attached or otherwise mounted on pads or regions77and79, respectively, which is most preferably accomplished using electrically conductive epoxy, more about which is said below.

FIG. 14shows substrate11and optical proximity sensor10after first and second infrared pass, optically transmissive, or optically clear components, compounds or materials31and32have been molded over infrared light emitter16and infrared light detector12, respectively. Note that lenses27and29may also be formed over infrared light emitter16and infrared light detector12during the overmolding process, where lenses27and29are configured to increase the efficiency of collimating outwardly transmitted or received light, as the case may be. While first and second infrared pass components31and32are most preferably formed using transfer molding techniques, other suitable molding techniques may also be employed such as compression molding methods. Following molding of components31and32, infrared light pass components31and32are cured.

FIG. 15shows optical proximity sensor10after ambient light detector14has been die-attached to the upper surface of integrated circuit, and after wires78have been wire bonded to ambient light detector14and wire bond pads76on substrate11. Die attachment of ambient light detector14is most preferably accomplished using electrically conductive epoxy, more about which is said below.

Referring now toFIG. 16, there is shown optical proximity sensor10after infrared cut optically non-transmissive component, compound or material33has been molded between first and second infrared pass components31and32and between infrared light emitter16and infrared light detector12, as well as over portions first and second infrared pass components31and32such that apertures52and54are formed in component33. After molding, infrared light cut component, compound or material33is cured. Infrared light cut component33is configured to permit a first portion of light emitted by light emitter16to pass through infrared light pass component31and first aperture52such that at least a second portion of the first portion of light reflected from an object of interest in proximity to sensor10passes through second aperture54and infrared light pass component31for detection by infrared light detector12. Infrared light cut component33is further configured to be disposed between infrared light emitter16and infrared light detector12in each of devices10so as to substantially attenuate or block the transmission of undesired direct, scattered or reflected light between infrared light emitter16and infrared light detector12and thereby minimize optical crosstalk and interference between infrared light emitter16and infrared light detector12.

FIGS. 17,18and19show top perspective, bottom perspective and side view, respectively, of optical proximity sensor10after ball grid array83has been attached to the underside of sensor10on electrical contacts71(see, for example,FIGS. 10 and 11). Optical proximity sensor10is now ready for mounting to another device, and for establishing electrical interconnection therewith, through ball grid array83in a manner well known in the art.

According to one embodiment, light emitter16is a semiconductor infrared LED such as a Model No. TK116IRA TYNTEK™ AlGaAs/GaAs Infrared Chip, the data sheet for which is included in an Information Disclosure Statement filed on even date herewith and the entirety of which is hereby incorporated by reference herein. Light detector12may be, by way of example, a TYNTEK™ Si Photo-diode Chip No, TK 043PD, the data sheet for which is hereby incorporated by reference herein in its entirety. Ambient light detector14may be, by way of example, an AVAGO TECHNOLOGIES™ APDS-9005 Miniature Surface-Mount Ambient Light Photo Sensor, the data sheet for which is hereby incorporated by reference herein in its entirety. Integrated circuit35may be, by way of example, an AVAGO TECHNOLOGIES™ APDS-9700 signal conditioning IC for optical proximity sensors, the data sheet for which is hereby incorporated by reference herein in its entirety.

Infrared light cut component33does not extend over apertures52,54which are configured to permit the passage of direct, reflected and ambient light therethrough, respectively. Infrared light cut component33does extend and is molded between a first portion and a second portion of substrate11so as to attenuate or absorb undesired scattered, reflected or direct light rays that might otherwise propagate between light emitter16and light detectors12and14. That is, infrared light cut component33is configured and molded to substantially attenuate or block the transmission of undesired direct, scattered or reflected light between light emitter16and light detector12, and thereby minimize optical crosstalk and interference between light emitter16and light detector12. Infrared light emitter16is operably connected to integrated circuit35and is driven by a light emitter driving circuit contained therein. Similarly, light detector12is operably connected to integrated circuit35, which comprises a light detector circuit incorporated therein. Ambient light detector or sensor14is also operably connected to integrated circuit35, which contains an ambient light sensing circuit incorporated therein.

Infra-red rays emitted by light emitter or LED16exit sensor10and return to light detector12as rays, thereby permitting detection of the nearby object that is to be detected. Light rays reflected from the surface of molded component31are blocked from reaching light detector12by molded substantially optically non-transmissive infrared light cut component33. Light rays reflected from a window interposed between optical sensor10and object to be detected60are also blocked by molded substantially optically non-transmissive infrared light cut component33. Total Internal Reflection between components31and33helps improve the performance of proximity sensor10. As will now be seen, the embodiment of sensor10shown inFIGS. 8 through 19eliminates the need to provide a metal shield, while improving the optical performance of sensor10by reducing crosstalk and interference, as undesired reflected, refracted or diffracted light rays cannot penetrate and travel through to light detectors12or14.

According to one embodiment, molded optically transmissive infrared light pass component, compound or material is formed using an infrared-pass and optically transmissive transfer molding compound such as NITTO DENKO™ NT-8506 clear transfer molding compound 8506 or PENCHEM Technologies™ OP 579 infrared pass optoelectronic epoxy. Other suitable optically transmissive epoxies, plastics, polymers or other materials may also be employed. See Technical Data Sheet NT-8506 entitled “Clear Transfer Molding Compound NT-8506” dated 2001 and PENCHEM OP 579 IR Pass Optoelectronic Epoxy Data Sheet, Revision 1, dated April, 2009, both of which documents are hereby incorporated by reference herein, each in its respective entirety.

In one embodiment, molded substantially optically non-transmissive infrared light cut component33is formed using an infrared-blocking, filtering or cutting transfer molding compound such as NITTO DENKO™ NT-MB-IRL3801 two-part epoxy resin material or PENCHEM Technologies™ OP 580 infrared filter optoelectronic epoxy, either of which preferably contains an amount of an infrared cutting material that has been selected by the user to achieve acceptable infrared light blocking performance while minimizing the amount of such infrared cutting material employed to keep costs to a minimum. Other suitable optically non-transmissive epoxies, plastics, polymers or other materials may also be employed. See Technical Data Sheet NT-MB-IRL3801 published by DENKO™ dated 2008 and PENCHEM OP 580 IR Filter Optoelectronic Epoxy Data Sheet, Revision 1, dated April, 2009, both of which documents are hereby incorporated by reference herein, each in its respective entirety.

Referring now toFIG. 20, there are shown steps corresponding to one embodiment of method100for making optical proximity sensor10. As shown inFIG. 20, the assembly process begins at step101and by laminating tape63on upper surface67of substrate11. Next, integrated circuit35(which in a preferred embodiment is an AVAGO TECHNOLOGIES™ 9700 ASIC) is die-attached to the adhesive underside of tape63at step103after being mounted in aperture65. Wire bonding is then conducted at step105at a bonding temperature of 150 C. After wire bonding, 100% visual inspection is conducted at step107to verify the integrity and robustness of the connections established by wire bonding. After visual inspection at step107, plasma cleaning step109is conducted.

First transfer molding process111is carried out using a black IR cut component, compound or material such as NT8570 at a molding temperature ranging between about 150 C and about 160 C. At step113post-mold curing is carried out at 150 C for about 3 hours. At step115laminating tape63is removed form substrate11. In a die attachment process at step117, infrared light emitter16(e.g., an LED TK116IR IC) is attached to substrates11using an electrically conductive epoxy such as FDP5053 or FDP5100, which is then cured at step119at 180 C for 30 minutes.

In a die attachment process at step121, infrared light detector12(e.g., a PD-TK043PD IC) is attached to substrate11using an electrically conductive epoxy such as FDP5053 or FDP5100, which is then cured at step123at 180 C for 30 minutes. Next, at step125plasma cleaning is conducted to clean the surface of substrate11, and especially the wire bonding surfaces thereof. Wire bonding is then conducted at step127at a bonding temperature of 150 C. After wire bonding, 100% visual inspection is conducted at step129to verify the integrity and robustness of the connections established by wire bonding. After visual inspection at step129, a plasma cleaning step131is conducted.

At step133, integrated circuit35is partially encapsulated by a clear transparent compound such as PT1002AB clear casting component, compound or material, followed by curing at step135. Next, at step137ambient light detector14(which in a preferred embodiment is an AVAGO TECHNOLOGIES™ APDS-9005 Miniature Surface-Mount Ambient Light Photo Sensor) is die-attached to integrated circuit35using an electrically non-conductive epoxy such as ABLESTK™ 2025. Next, at step139plasma cleaning is conducted to clean the surface of substrates11, and especially the wire bonding surfaces thereof. Wire bonding is then conducted at step141at a bonding temperature of about 150 C. After wire bonding, 100% visual inspection is conducted at step143to verify the integrity and robustness of the connections established by wire bonding. After visual inspection at step143, a plasma cleaning step145is conducted.

At step147, a second encapsulation process147is conducted using a clear IR cut casting component, compound or material such as NT-MB-IRL 3801 at a molding temperature ranging between about 150 C and about 160 C, followed by post-molding curing at step149at about 135 C for about 1 hour. At step151solder balls for ball grid array83are attached to electrical contacts71on the underside of optical proximity sensor10. Solder reflow is then carried out at step153, followed by singulation of individual packages or sensors10. Baking is carried out at step157at about 150 C for about 30 minutes. Sensors10which have passed inspection and testing are packed onto a tape and reel at step159for baking and shipping at step161.

Those skilled in the art will understand that many different variations in, and permutations or combinations of, the steps disclosed above can be made without departing from the scope of the invention such as by, for example, modifying steps, changing the order of steps, omitting steps, adding steps, and so on.

The transfer molding processes described above include methods where thermosetting materials are softened by heat and pressure in a transfer chamber, and then forced at high pressure through suitable sprues, runners, and gates into a closed mold for final curing.

Included within the scope of the present invention are methods of making and having made the various components, devices and systems described herein.

Those skilled in the art will understand that the various embodiments of the proximity sensor disclosed herein may be incorporated into portable electronic devices such as mobile telephones, smart phones, personal data assistants (PDAs), laptop computers, notebook computer, computers and other devices.

Various embodiments of the invention are contemplated in addition to those disclosed hereinabove. The above-described embodiments should be considered as examples of the present invention, rather than as limiting the scope of the invention. In addition to the foregoing embodiments of the invention, review of the detailed description and accompanying drawings will show that there are other embodiments of the invention. Accordingly, many combinations, permutations, variations and modifications of the foregoing embodiments of the invention not set forth explicitly herein will nevertheless fall within the scope of the invention.

Included within the scope of the present invention are methods of making and having made the various components, devices and systems described herein.

Those skilled in the art will understand that the various embodiments of the proximity sensor disclosed herein may be incorporated into portable electronic devices such as mobile telephones, smart phones, personal data assistants (PDAs), laptop computers, notebook computer, computers and other devices.

Various embodiments of the invention are contemplated in addition to those disclosed hereinabove. The above-described embodiments should be considered as examples of the present invention, rather than as limiting the scope of the invention. In addition to the foregoing embodiments of the invention, review of the detailed description and accompanying drawings will show that there are other embodiments of the invention. Accordingly, many combinations, permutations, variations and modifications of the foregoing embodiments of the invention not set forth explicitly herein will nevertheless fall within the scope of the invention.