Abstract:
A control aperture for an IR sensor includes a die; an IR sensor disposed on the die and an IR opaque aperture layer on the die having an IR transmissive aperture aligned with the IR sensor for controlling the field of view and focus of the IR sensor.

Description:
RELATED APPLICATIONS 
     This application claims benefit of and priority to U.S. Provisional Application Ser. No. 60/877,305 filed Dec. 27, 2006 incorporated herein by this reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to an improved, integral control aperture for an IR sensor. 
     BACKGROUND OF THE INVENTION 
     Generally, infra-red (IR) sensors employ a metal can containing a silicon chip containing the IR sensor. There is a hole in the can which defines the IR aperture and the hole is typically sealed with a silicon window transparent to IR wavelengths. These tend to be expensive, large and cumbersome units, which can suffer from alignment issues and are limited in the types of mountings with which they can be used. 
     BRIEF SUMMARY OF THE INVENTION 
     It is therefore an object of this invention to provide an improved integral control aperture for an IR sensor. 
     It is a further object of this invention to provide such an improved integral control aperture for an IR sensor which can be manufactured using existing package structure, materials and techniques. 
     It is a further object of this invention to provide such an improved integral control aperture for an IR sensor in which the spot:distance ratio can be better controlled. 
     It is a further object of this invention to provide such an improved integral control aperture for an IR sensor in which the control aperture can be on either side of the die. 
     It is a further object of this invention to provide such an improved integral control aperture for an IR sensor which the control aperture layer provides protection for micro etched focusing elements. 
     It is a further object of this invention to provide such an improved integral control aperture for an IR sensor which provides increased accuracy in aligning the control aperture with the IR sensor. 
     It is a further object of this invention to provide such an improved integral control aperture for an IR sensor which can be achieved on even smaller package parts, e.g. bumped packages. 
     It is a further object of this invention to provide such an improved integral control aperture for an IR sensor which permits mounting on a ported mounting plane, e.g. circuit board. 
     The invention results from the realization that an improved integral control aperture for an IR sensor which better controls the spot:distance ratio can be fabricated using existing structure, materials, and techniques. This can be achieved with an IR sensor mounted on a die and an IR opaque aperture layer on or proximate to the die having an IR transmissive aperture aligned with the IR sensor for controlling the field of view and focus of the IR sensor. 
     The subject invention, however, in other embodiments, need not achieve all these objectives and the claims hereof should not be limited to structures or methods capable of achieving these objectives. 
     This invention features a control aperture for an IR sensor including a die and an IR sensor disposed on the die. An IR opaque aperture layer on the die has an IR transmissive aperture aligned with the IR sensor for controlling the field of view and focus of the IR sensor. 
     In a preferred embodiment the IR may be on one side of the die and the aperture layer may be on the other and the die is transparent to IR. The aperture layer may include a paddle bonded to the die. The aperture layer may include a copper alloy material. The die may include a base supporting the IR sensor and a cap covering the IR sensor. The die and paddle may be mounted in a molded package. The die may include silicon. The aperture layer may include an IR opaque coating bonded to the die. The die may include solder bumps. The solder bumps may be on the side opposite the aperture layer. The aperture layer may be on the cap portion of the die covering the IR sensor on one side of the base of the die and the solder bumps may be on the other side of the die. The IR sensor may be on one side of the base of the die covered by the cap and the aperture layer may be on the other side of the die which contains solder bumps. The IR sensor may be on one side of the base of the die covered by the cap and the aperture layer may include a laminated layer bonded to the die on the other side from IR sensor. The laminate may carry solder bumps. The die may be disposed in a mold which together with the laminate layer forms a laminate package. The die may be disposed in a mold which constitutes the aperture layer on the cap portion of the die. The other side of the die may be supported by a lead frame. The die may be disposed in the mold which exposes at least a portion of the cap and the aperture layer may be disposed on the cap. The other side of the die may be supported by a lead frame. There may be a coating on the other side of the die. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which: 
         FIG. 1  is a schematic side sectional view of the control aperture for an IR sensor according to this invention in an exposed paddle package; 
         FIG. 2  is a schematic side sectional view of the control aperture for an IR sensor according to this invention on a bumped part with the aperture and sensor on opposite sides; 
         FIG. 3  is a schematic side sectional view of the control aperture for an IR sensor according to this invention on a bumped part with the aperture and sensor on the same side; 
         FIG. 4  is a schematic side sectional view of the control aperture for an IR sensor according to this invention on a bumped part with the aperture and sensor in a laminate package, and the aperture defined by the laminate; 
         FIG. 5  is a schematic side sectional view of the control aperture for a plastic IR sensor using the mold compound as the control aperture; and 
         FIG. 6  is a schematic side sectional view of the control aperture for a plastic IR sensor using a separate layer as the control aperture. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Aside from the preferred embodiment or embodiments disclosed below, this invention is capable of other embodiments and of being practiced or being carried out in various ways. Thus, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. If only one embodiment is described herein, the claims hereof are not to be limited to that embodiment. Moreover, the claims hereof are not to be read restrictively unless there is clear and convincing evidence manifesting a certain exclusion, restriction, or disclaimer. 
     There is shown in  FIG. 1  an exposed paddle lead frame package  10  including a silicon die  12  having a base  14  and cap portion  16 . Cap  16  and base portion  14  may both be made of silicon. Cap  16  covers IR sensor  18  forming space or volume  20 ; volume  20  within cap  16  may be e.g. an air space or a vacuum. Silicon die  12  is mounted in a mold compound  22 , such as Sumitomo G770, which also contains copper alloy component leads  24  and  26 , interconnected with die  14  by means of gold bond wires  28  and  30 . Silicon die  12  is placed on a lead frame paddle  34 , typically fabricated from a copper alloy, which may be a prior art paddle. That paddle incorporates the control aperture  36 . Initially such a paddle functions to support the silicon but here it does double service as the aperture layer. The aperture  36  in aperture layer  34  is aligned with and on the other side of die  14  from sensor  18 . Aperture layer or paddle  34  may be bonded to silicon die  12  by means of an adhesive  38  such as Ablestik 8290. There may be etched silicon focusing elements  40  on die  12  within aperture  36 . For an even more accurate aperture placement, a metalized layer  42  may be employed between die  12  and aperture layer  34 . The metalized layer  42  will also be IR opaque as is the aperture layer  34  but in this case the aperture  44  in it may be more precisely deposited on the silicon  14 , and etched for more accurate alignment with the sensor  18 . The invention can be employed in any exposed paddle lead frame package and provides the added benefit of some protection against handling damage for the etched focusing features  40  on the exposed silicon die  12 . The etched silicon focusing elements are explained in greater detail in U.S. patent application Ser. No. 11/045,910, filed Jan. 26, 2005 entitled SENSOR AND CAP ARRANGEMENT, incorporated in its entirety herein by this reference. 
     In the following  FIGS. 2-6  similar parts have been given like numbers accompanied by a lower case letter. 
     A control aperture for an IR sensor on a bump part  10   a ,  FIG. 2 , uses aperture layer  34   a , typically 5-25 microns thick which can be made of a filled organic polymer or could also be a metalized, typically sputtered, layer. As usual the aperture layer is IR opaque and contains an aperture  36   a , which is aligned with sensor  18   a  on the other side of die  12   a  on the die base  14   a  covered by die cap  16   a . In aperture  36   a  again there may etched silicon focusing elements  40   a . Solder bumps  24   a ,  26   a  may be mechanically and electrically connected to die base  14   a . This makes a smaller, lighter and less expensive package and can be accomplished with any bumped die part by coating the back of the wafer and creating the required aperture by exposing/etching/rinsing in the usual way. An added benefit here again is that the coating provides some protection against handling damage for the etched focusing features on the exposed silicon. While the aperture layer and aperture are on one side of die  12   a  and the IR sensor  18   a  is on the other in  FIG. 2 , this is not a necessary limitation of the invention for as shown in  FIG. 3 , IR sensor  18   b  and cap or cover  16   b  may be on the same side as aperture layer  34   b  with aperture  36   b . Alternatively,  FIG. 3 , as shown in dashed lines for contrast and clarity, solder bumps  24   b  and  26   b  may be mounted on a laminated layer  50 , such as a printed circuit board, which is ported  52  to pass IR radiation  54 . In this construction the aperture layer  34   bb  may be placed on the underside of die base  14   b  providing aperture  36   bb  in aperture layer  34   bb  and again there may be etched silicon focusing elements  40   bb  positioned there aligned with IR sensor  18   b  and aperture  36   bb  which is in turn aligned with port  52  in laminated layer  50 . In  FIG. 3 , cap  16   b  has aperture layer  34   b  only on top and so the sidewalls  17   b  may allow some spurious IR radiation to reach sensor  18   b . Coating processes such as dispensed coatings can deal with this if required. 
     A control aperture for an IR sensor according to this invention may be used in a laminate package,  10   c ,  FIG. 4 , where the aperture layer  34   c  may actually be a laminate board with conductor layers having an aperture  36   c  aligned with sensor  18   c  on the other side of die  12   c  covered by cap  16   c . The die as well as gold wire bonds  28   c  and  30   c  are contained in a molded body  22   c  typically using the type of mold compound as cited before, e.g. Sumitomo G770. Silicon  14   c  may be adhered to the laminate aperture layer  34   c  by an adhesive  42   c  such as Ablestik 8290. The control aperture for an IR sensor of this invention may also be practiced in a plastic package  10   d ,  FIG. 5 , in which the mold compound  22   d  also functions as the aperture layer  34   d  containing aperture  36   d . Also disposed with mold  22   d  there may be a copper lead frame  60  which includes copper alloy component leads  24   d ,  26   d . Silicon die  12   d  may be bonded to lead frame  60  by adhesive  42   d , such as Ablestik 8290. 
     Alternatively, as shown in  FIG. 6 , plastic package  10   e  may be made with the mold  22   e  reduced to be more or less flush with the top of cap  16   e  so that an aperture layer  34   e  such as a metalized layer or a polymer is used having its own aperture  36   e . These approaches can be accomplished in any plastic package by pre-coating the wafer cap with an opaque layer, for example sputtered metal, and then etching the aperture  36   e.    
     Although specific features of the invention are shown in some drawings and not in others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention. The words “including”, “comprising”, “having”, and “with” as used herein are to be interpreted broadly and comprehensively and are not limited to any physical interconnection. Moreover, any embodiments disclosed in the subject application are not to be taken as the only possible embodiments. 
     In addition, any amendment presented during the prosecution of the patent application for this patent is not a disclaimer of any claim element presented in the application as filed: those skilled in the art cannot reasonably be expected to draft a claim that would literally encompass all possible equivalents, many equivalents will be unforeseeable at the time of the amendment and are beyond a fair interpretation of what is to be surrendered (if anything), the rationale underlying the amendment may bear no more than a tangential relation to many equivalents, and/or there are many other reasons the applicant can not be expected to describe certain insubstantial substitutes for any claim element amended. 
     Other embodiments will occur to those skilled in the art and are within the following claims.