Abstract:
An uncooled high-resolution 12 micron pixel pitch 3D-stacked component thermal camera including an electronics board, a camera circuit card assembly (CCA) with an application-specific integrated circuit (ASIC), a synchronous dynamic random access memory (SDRAM), flash memory, a spacer, a wafer level packaged Focal Plane Array (FPA) wafer with a lens housing attach ring on the FPA, and a window.

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention was made with United States Government support under Contract No. HR0011-11-C-0126 awarded by the Defense Advanced Research Projects Agency (DARPA). The United States Government has certain rights in this invention. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to uncooled thermal imagers and more particularly relates to high-resolution thermal chip cameras. 
     BACKGROUND OF THE INVENTION 
     Traditional uncooled thermal imager cost is prohibitive for mass-production. In addition, the size, weight, power requirements (and cost) of these imagers may not be well-suited for Unmanned Arial Vehicles (UAV) and man-portable applications. 
     A need exists for uncooled cameras which are small, light-weight, power efficient, and inexpensive enough to be well-suited for UAV and man portable applications. 
     SUMMARY OF THE INVENTION 
     An embodiment provides an uncooled high-resolution 12 micron pixel pitch 3D-stacked component thermal camera device comprising a camera circuit card assembly (CCA) comprising an application-specific integrated circuit (ASIC); a synchronous dynamic random access memory (SDRAM); a flash memory wafer; and a wafer level packaged Focal Plane Array (FPA) wafer. In embodiments, the CCA comprises a small circuit board with the FPA on one side, the ASIC, the SDRAM memory and the flash memory and other supporting circuits and output connector on the back side of the CCA. In other embodiments, the configuration of the camera comprises the FPA and electronics adjacent to each other on a same side of a circuit board of the CCA. In subsequent embodiments, the wafer level packaged FPA comprises a focal plane and a window, a lens integrated with the camera by a lens housing attach ring on the FPA, and a spacer between the SDRAM memory and flash memory. For additional embodiments, the CCA comprises Surface Mount Technology (SMT) devices. In another embodiment, the camera operates at 15 Hz, 30 Hz, and 60 Hz with a slow frame rate of about 7.5 Hz to about 8.33 Hz. For a following embodiment, the ASIC, the SDRAM, and the flash memory wafers comprise full thickness substrates. In subsequent embodiments, the ASIC, the SDRAM, and the flash memory wafers are thinned. In additional embodiments, at least one of the ASIC, the SDRAM, and the flash memory has a full thickness substrate and at least one is thinned. 
     Another embodiment provides a method for preparing a bare die for a 12 micron pixel pitch uncooled high-resolution thermal camera using 3D-stacking implementation comprising dicing an application-specific integrated circuit (ASIC) wafer; dicing synchronous dynamic random access memory (SDRAM) wafer; dicing flash wafer; dicing a wafer level packaged Focal Plane Array (FPA) wafer; assembling a circuit card assembly (CCA); die attaching the ASIC; die attaching the SDRAM; die attaching a spacer; die attaching the flash; wire bonding the SDRAM to the ASIC; wire bonding the flash to the ASIC; wire bonding the ASIC to the CCA; wire bonding the SDRAM to the CCA; wire bonding the flash to the CCA; die attaching the FPA; wire bonding the FPA to the CCA; and filling backside whereby the ASIC stack wire bonds are protected. In included embodiments, the CCA assembly comprises attaching standard Surface Mount Technology (SMT) devices. In yet further embodiments, the camera operates at 15 Hz, 30 Hz, and 60 Hz. In related embodiments, the diced ASIC wafer, the diced SDRAM wafer, and the diced flash wafer are full thickness substrates. For further embodiments, the diced ASIC wafer, the diced SDRAM wafer, and the diced flash wafer are thinned. In ensuing embodiments, at least one of the diced ASIC wafer, the diced SDRAM wafer, and the diced flash wafer has a full thickness substrate and at least one is thinned. For yet further embodiments, the CCA comprises a small circuit board with the FPA on one side, the ASIC, the SDRAM memory and the flash memory and other supporting circuits and output connector on a back side of the CCA. For more embodiments, a configuration of the camera comprises the FPA and electronics adjacent to each other on a same side of a circuit board of the CCA. In continued embodiments, the wafer level packaged FPA comprises a focal plane and a window, a lens integrated with the camera by a lens housing attach ring on the FPA, and a spacer between the SDRAM memory and flash memory. For additional embodiments, the camera operates with a slow frame rate of about 7.5 Hz to about 8.33 Hz. 
     A yet further embodiment provides an uncooled 12 micron pixel pitch high-resolution thermal camera system using 3D-stacking comprising a camera circuit card assembly (CCA); an application-specific integrated circuit (ASIC), the ASIC comprising an imaging engine to operate a Focal Plane Array (FPA) and provide pixel corrections and calibration; a synchronous dynamic random access memory (SDRAM); a flash memory wafer, wherein the SDRAM memory and the flash memory are stacked on the ASIC; and a wafer level packaged FPA wafer comprising the FPA, wherein the FPA comprises alignment pixels and buffer pixels and a partition architecture; a lens comprising an f-number of about 1.2, a Field Of View (FOV) of about 42°×26°, and an Instantaneous Field Of View (IFOV) of about 400 μrad; a Cameralink input output adapter; a Mobile Industry Processor Interface (MIPI) format adapter; and dual row biasing for large arrays whereby adequate pulse time and sensitivity are maintained. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a VGA FPA configured in accordance with an embodiment of the invention. 
         FIG. 2  shows perspective and exploded views of a Stacked Modular Architecture High-Resolution Thermal (SMART) chip camera configured in accordance with an embodiment of the invention. 
         FIG. 3  shows front and rear elevational views of the circuit card assembly (CCA) board configured in accordance with an embodiment of the invention. 
         FIG. 4  shows front and rear views of the CCA board and a perspective view of the lens mount configured in accordance with an embodiment of the invention. 
         FIG. 5  shows views of the integration of the chip camera with a cell phone configured in accordance with an embodiment of the invention. 
         FIG. 6  shows front and rear views of the integration of the chip camera with a flex cable configured in accordance with an embodiment of the invention. 
         FIG. 7  depicts a CHIP camera method configured in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The features and advantages described herein are not all-inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been selected principally for readability and instructional purposes, and not to limit in any way the scope of the inventive subject matter. The invention is susceptible of many embodiments. What follows is illustrative, but not exhaustive, of the scope of the invention. 
     In one embodiment of the invention, the SMART chip camera costs less than $500, presents a volume smaller than 3.5 cubic centimeters, weighs less than 25 grams, and consumes less than 500 milliwatts. Wafer-level technologies are leveraged at multiple levels to accomplish superior achievements such as packaging of the bolometers and calibration of the units. In addition, the electronics board is rendered more compact and less power consumptive by using 3D-stacking implementation. Finally, the IR camera is compatible with Android-based cell phones. 
       FIG. 1  shows a perspective view  100  of the Low Cost Thermal Imager-Manufacturing (LCTI-M) sensor (without lens). For comparison, penny  105  is shown beside sensor  110 . The top side is the wafer level packaged VGA FPA. The back side contains an ASIC imaging engine, memory, supporting electronics, and system flex connector. This module, with a very compact wafer-scale compatible f/1.2 lens, has been demonstrated and integrated into a commercial cell phone displaying the IR image on the cell phone display using a custom Android application. The basic VGA FPA was available early in the LCTI-M program and has seen early insertions into several applications requiring uncooled cameras which are small, light-weight, power efficient, and inexpensive. 
       FIG. 2  shows perspective and exploded views of a SMART chip camera  200 . Depicted are flash  205 , spacer  210 , SDRAM  215 , ASIC  220 , focal plane  225 , window  230 , lens housing  235 , and perspective view  240 . In a camera embodiment, significant components include 1) wafer level packaged FPA (focal plane and window), 2) ASIC for imaging engine to operate FPA and provide pixel corrections/calibration, 3) memory (SDRAM and flash) stacked on ASIC (or in close proximity), 4) small circuit board with FPA on one side and ASIC/memory and other supporting circuits and output connector on back side, 5) lens integrated with 1-4, 6) an alternate configuration with FPA and electronics adjacent to each other on the same side of the circuit board. 
       FIG. 3  shows front and rear elevation views  300  of the circuit card assembly (CCA) board. Depicted components include lens housing attach ring  305 , focal plane array  310  on front side, and power supply SMT  315 , ASIC memory stack  320 , and connector  325  on back side. 
       FIG. 4  shows the assembly of a prototype  400 . Depicted are front side of the wafer level packaged FPA circuit board  405 ; back side of the circuit board with stacked ASIC/memory, connector, and supporting circuits  410 ; and compact lens for mounting on the front side of the CCA  415 . Embodiments have other lens mount methods. 
       FIG. 5  shows the physical integration of the SMART chip camera with a cell phone  500 . Depicted are component arrangement  505 ; lens-side perspective view  510 ; and cell phone device internals  515 . 
       FIG. 6  shows views  600  of the integration of the SMART chip camera with a flex cable showing a service loop. Depicted are view from the lens front side  605  and view from the lens rear side  610 . The flex cable has a chip to convert sensor output to Mobile Industry Processor Interface (MIPI) format (to interface with phone processors or other MIPI devices). 
       FIG. 7  presents device manufacturing steps  700 . CCA manufacturing steps comprise bare die preparation  705 ; ASIC wafer diced  710 ; SDRAM wafer diced  715 ; flash wafer diced  720  (these may be thinned or full thickness substrates); wafer level packaged Focal Plane Array wafer diced  725 ; CCA Assembly  730  comprising: attach standard Surface Mount Technology (SMT) devices  735  (i.e. power supply and decoupling capacitors); die attach ASIC  740 ; die attach SDRAM  745 ; die attach spacer  750 ; and die attach flash  755 ; wire bond SDRAM to ASIC  760 ; wire bond flash to ASIC  765 ; die attach FPA  770 ; wire bond FPA to CCA  775 ; and fill back side to protect ASIC stack wirebonds  780 . 
     The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Each and every page of this submission, and all contents thereon, however characterized, identified, or numbered, is considered a substantive part of this application for all purposes, irrespective of form or placement within the application. This specification is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure. Other and various embodiments will be readily apparent to those skilled in the art, from this description, figures, and the claims that follow. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.