Patent Publication Number: US-2006003483-A1

Title: Optoelectronic packaging with embedded window

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application is a continuation-in-part of U.S. patent application Ser. No. 10/613,089, filed Jul. 7, 2003 by the same inventors, now pending. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates to the packaging of optical semiconductor or optoelectronic devices.  
     BACKGROUND OF THE INVENTION  
      Optical semiconductors are key components in a wide variety of electronic devices. Because optical semiconductors are fragile and subject to damage by impact, abrasion, contaminants, moisture, heat, and other factors, each optical semiconductor is typically encased in a protective package. However, unlike the protective packages used to encase most other electronic components, the package for an optical semiconductor must incorporate a region that is transparent to light.  
      It has been a common practice to create an optoelectronic sensor package by mounting a sensor within a ceramic container with embedded conductive leads, then sealing the container with a window made of optical glass. The window does not directly contact the sensor, instead leaving some air space between the window and the sensor.  
      While this method can produce a relatively rugged sensor package with good optical properties, the enclosed space between the window and the die may contain moisture that can condense within the package. The enclosed space also adds at least two boundary layers to the light path, possibly resulting in unwanted reflection, refraction, or dispersion of light. These undesirable effects may be intensified if the plate is not parallel to the die surface.  
      Therefore, the requirements for extremely clean manufacturing conditions, humidity control within the container, and precise sensor die positioning with respect to the window often result in a packaged sensor that is bulky and expensive, sometimes accounting for half the total cost of a finished product.  
      Recent improvements in adhesives and manufacturing technology have made possible the simultaneous fabrication of large numbers of identical sensor packages in which the window is bonded directly to the die, thereby eliminating enclosed air space. This is accomplished by bonding a single sheet of suitable window material to an array of optical semiconductors, then cutting the sheet to separate the individual packages. Low-cost plastic encapsulation material may be used to seal portions of the die that remain exposed.  
      While this method mitigates many of the problems arising from inclusion of an air space between a window and a die, the resulting package may retain a considerable amount of unusable window material, which, being heavy and expensive relative to plastic encapsulation materials typically used to complete the package, adds unwanted weight and cost to the finished product. Further, every window produced in a given production run is essentially the same, limiting the manufacturer&#39;s ability to adapt to market demands by economically producing small numbers of sensor packages with windows having different characteristics.  
      What is needed, then, is a method for manufacturing a packaged optoelectronic sensor that reduces the bulk and cost of the packaged sensor while providing adequate protection for the die and mitigating the problems arising from space between the window and die. Windows should be placed and bonded individually, allowing flexibility in the manufacturing process. The method should utilize standard manufacturing equipment and raw materials.  
     SUMMARY OF THE INVENTION  
      The present invention is a manufacturing method that utilizes standard manufacturing equipment and raw materials to produce compact, low-cost packaged optoelectronic components such as Erasable Programmable Read Only Memory (EPROM) chips, Electrically Erasable Programmable Read Only Memory (EEPROM) chips, Charge-Coupled Device (CCD) chips, Complementary Metal Oxide Semiconductor (CMOS) chips, and other optical semiconductor devices that are known in the art.  
      In a preferred embodiment of the present invention an aperture member is created from optical glass, plastic, or other materials that are transparent to the radiation spectra of interest. The material may be selected to absorb or pass specific radiation frequencies. An aperture member is typically cut from a plate of suitable material by a sawing, dicing, or scribing process, although other known processes may be used. The aperture member may be shaped, scored, or otherwise modified to refract, diffract, or diffuse light passing through. The aperture member may be sized and shaped to cover any portion of a semiconductor die, but is preferably sized to cover only the optically-sensitive portion of the die. Since the aperture member is individually manufactured, it may be of any suitable thickness and may have a horizontal cross-section of any suitable shape.  
      A semiconductor die with an optically-sensitive portion is then mounted on a lead frame. A computer-controlled pick-and-place machine selects an aperture member with desired characteristics. Pick-and-place machines are standard semiconductor manufacturing devices and may be programmed to select and precisely place a different component from one operation to the next. A transparent adhesive is applied to the aperture member, or to the die, or to both, then the pick-and-place machine positions the aperture member over the optically-sensitive portion of the die. The aperture member is pressed against the die, allowing the transparent adhesive to bond the aperture member to the die. The transparent adhesive may be an epoxy, silicon, tape, or other adhesive materials that are known in the art.  
      Since the aperture member is attached directly to the die, no intervening air space remains to produce condensation or unwanted reflection, refraction, or diffusion. Since the aperture member is pre-sized and pre-shaped to cover the optically-sensitive portion of the die, the surfaces of the aperture member are automatically made parallel to the die surface upon installation and require no further cutting. Both the aperture member material and the transparent adhesive may be selected for desired refractive index, absorption, or other physical characteristics. The assembly is encapsulated with an epoxy molding compound or other encapsulate as is known in the art, leaving the leads and the upper portion of the aperture member exposed.  
      In an alternate embodiment of the present invention, a semiconductor die with an optically-sensitive area may be mounted with an adhesive material on a Printed Circuit Board (PCB) or ceramic substrate. The adhesive material may be a silver-filled epoxy, a polyimide epoxy, a thermally-conductive epoxy, a thermally or electrically non-conductive epoxy, an adhesive tape, or a metal alloy.  
      Metal wires such as gold, aluminum, or copper are bonded between the semiconductor die and the active circuitry on the substrate. A transparent adhesive is applied to the semiconductor die or to an aperture member made of borosilicate glass or another suitable material known in the art. The aperture member is placed on the optically-sensitive portion of the die by a pick-and-place machine. The assembly is baked. The die, aperture member, and substrate are encapsulated with an epoxy molding compound. Finally, the individual die package is separated from any attached frame or substrate and visually inspected. 
    
    
     DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a perspective view of an encapsulated optoelectronic device.  
       FIG. 2  shows a cutaway view of the encapsulated optoelectronic device of  FIG. 1 , revealing portions of a lead frame, semiconductor die, and embedded aperture member.  
       FIG. 3  is a cross-sectional view of the encapsulated optoelectronic device of  FIG. 1 .  
       FIGS. 4A through 4E  are cross-sectional views showing the assembly of a Through Hole Device (THD) package.  
       FIGS. 5A through 5E  are cross-sectional views showing the assembly of a Surface Mount Device (SMD) package.  
       FIGS. 6A through 6E  are cross-sectional views showing the assembly of a Plastic Non-Leaded package.  
       FIGS. 7A through 7F  ate cross-sectional views showing the assembly of a package with a substrate, such as a Land Grid Array (LGA) or a Ball Grid Array (BGA) package.  
       FIG. 8A  is a plan view of a die paddle with flexible support strips attached.  
       FIGS. 8B through 8F  are cross-sectional views showing the assembly of a Through Hole Device (THD) package with flexible support strips attached to the die paddle.  
       FIG. 9A  shows a plan view of a portion of a lead frame.  
       FIG. 9B  shows an enlarged view of four adjacent die paddle assemblies.  
       FIG. 9C  shows a cross-sectional elevation view of the die paddle assemblies of  FIG. 9B .  
       FIG. 9D  shows another cross-sectional elevation view of the die paddle assemblies of  FIG. 9B , with the vertical dimensions of the die paddles and metal contacts somewhat exaggerated for clarity.  
       FIG. 9E  shows a cross-sectional elevation view of components assembled on the die paddle assemblies of  FIG. 9D .  
       FIG. 9F  shows a portion of a plan view of a mold tool.  
       FIG. 9G  shows a cross-sectional elevation view of the mold tool of  FIG. 9F .  
       FIG. 9H  shows a portion of a cross-sectional elevation view after component assemblies are enclosed by a mold tool.  
       FIG. 9J  shows a cross-sectional elevation view of a singulated optoelectronic package.  
       FIG. 9K  shows a cross-sectional perspective view of a singulated optoelectronic package.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIGS. 1, 2 , and  3  show different views of an embodiment of the present invention.  FIG. 1  shows a perspective view of an encapsulated optoelectronic device.  FIG. 2  shows a cutaway view of the same device, revealing portions of a lead frame, semiconductor die, and embedded aperture member.  FIG. 3  is a cross-sectional view of the same device. In  FIG. 3 , an optical semiconductor die  32  is secured upon a die paddle  30  with an adhesive epoxy material  31  or other bonding agent known in the art. Metal wires  36  are bonded from semiconductor die  32  to external metal leads  37 , which connect the circuitry of the semiconductor die  32  to external circuitry (not shown).  
      A transparent adhesive  34  is then applied to the optically active upper surface  33  of the semiconductor die  32 . An aperture member  35  made of borosilicate glass or other suitable material known in the art is placed by a pick-and-place machine on the upper surface of transparent adhesive  34 , affixing the aperture member  35  to the transparent adhesive  34  and the optically active upper surface  33  of the semiconductor die  32 , forming a transparent aperture above the optically active upper surface  33 . The pick-and-place machine may according to its programming instructions select an aperture member with any desired characteristics. Since in accordance with the method of the present invention each aperture member is individually placed and affixed to a semiconductor die, the pick-and-place machine may select a different type of aperture member for each of any number of sequentially-assembled optoelectronic packages.  
      An aperture member may be created from optical glass, plastic, or other materials that are transparent to the radiation spectra of interest. The material may be selected to absorb or pass specific radiation frequencies. An aperture member is usually cut from a plate of suitable material by a sawing, dicing, or scribing process, although other known processes may be used. The aperture member may be shaped, scored, or otherwise modified to refract, diffract, or diffuse light passing through. The aperture member may be sized and shaped to cover any portion of a semiconductor die, but is preferably sized to cover only the optically-sensitive portion of the die. Since the aperture member is individually manufactured, it may be of any suitable thickness and may have a horizontal cross-section of any suitable shape.  
      No open space is left between the semiconductor die  32  and the aperture member  35  after the two parts are bonded. An epoxy molding compound or other encapsulate as is known in the art is formed around the die paddle  30 , semiconductor die  32 , and aperture member  35 , leaving the upper surface of the aperture member  35  and the external metal leads  37  exposed.  
      In an alternate embodiment of the present invention, the transparent adhesive  34  may be applied to a lower surface  39  of the aperture member  35 , with the lower surface  39  of the aperture member  35  then being positioned by a pick-and-place machine against the optically active upper surface  33  of the semiconductor die  32 .  
      In still another embodiment of the present invention the order of assembly steps may be varied. A transparent adhesive  34  is applied to the optically active upper surface  33  of the semiconductor die  32 . An aperture member  35  made of borosilicate glass or another suitable material as is known in the art is placed by a pick-and-place machine on the optically active upper surface  33  of the semiconductor die  32  and affixed to the transparent adhesive  34 , forming a transparent aperture above the optically active upper surface  33 . No open space is left between the semiconductor die  32  and the aperture member  35  after the two parts are bonded.  
      An optical semiconductor die  32  is then secured upon a die paddle  30  with an adhesive epoxy material  31  or other bonding agent known in the art. Metal wires  36  are bonded from semiconductor die  32  to external metal leads  37 , which connect the circuitry of the semiconductor die  32  to external circuitry (not shown). An epoxy molding compound or other encapsulate as is known in the art is formed around the die paddle  30 , semiconductor die  32 , and aperture member  35 , leaving the upper surface of the aperture member  35  and the external metal leads  37  exposed.  
       FIGS. 4A through 4E  show the assembly of a preferred embodiment of the present invention.  FIG. 4A  shows a cross-sectional view of a metal lead frame as is known in the art, with a die paddle  40  and metal leads  41 . The lead frame is configured to accommodate a desired semiconductor and related electrical circuitry.  
       FIG. 4B  shows a semiconductor die  43  attached by an adhesive material  42  to the upper surface of the die paddle  40 . The adhesive material  42  may be dispensed, stamped, laminated, or applied by other means known in the art atop the die paddle  40 . The adhesive material  42  can be a silver-filled epoxy, a polyimide epoxy, a thermally-conductive epoxy, a thermally or electrically nonconductive epoxy, an adhesive tape, or a metal alloy. The adhesive material  42  is heated and cured, thereby securing the semiconductor die  43  to the die paddle  40 .  
      In  FIG. 4C , metal wires  44  are bonded between the semiconductor die circuitry (not shown) and the metal leads  41 , connecting the die circuitry to external circuitry (not shown). The metal wires  44  may comprise gold, aluminum, copper or other suitable materials as are known in the art. An aperture member  46  is attached upon an optically-sensitive area of the die with a transparent adhesive material  45 . The transparent adhesive material  45  may be dispensed, stamped, laminated, or applied by other means known in the art to either upper surface of the semiconductor die  43  or the lower surface of the aperture member  46 .  
       FIG. 4D  shows a cross-sectional view of the present invention after the die paddle  40 , the semiconductor die  43 , and aperture member  46  are encapsulated with an epoxy molding compound as is known in the art, forming a package  47  while leaving the upper surface of the aperture member  46  and the metal leads  41  exposed.  
       FIG. 4E  shows the exposed metal leads  41  formed at approximately a 90-degree angle with respect to the plane of the die paddle  41 , creating a device especially suited for application as a Through Hole Device (THD) such as a Plastic Dual-Inline Package (PDIP). Finally, the individual package is punched out or cut from any attached metal frame to become a finished package.  
       FIGS. 5A through 5E  show the assembly of an embodiment similar to that shown in  FIGS. 4A through 4E , except that in  FIG. 5E  the exposed parts of the metal leads  51  may be formed as a gull wing, a J-form, or a C-form as required by external circuitry, creating a device especially suited for use as a Surface Mount Device (SMD) package such as a Plastic Leaded Chip Carrier (PLCC), a Small Outline Plastic (SOP), a Small Outline Integrated Circuit (SOIC), or a Plastic Quad Flat Pack (PQFP).  
       FIGS. 6A through 6E  show the assembly of an embodiment especially suited to non-leaded surface mount applications such as a Plastic non-Leaded Package (PLLP).  FIG. 6A  shows a cross-sectional view of a metal frame as is known in the art, with a die paddle  60  and metal contacts  61 . The frame is configured to accommodate a desired semiconductor and related electrical circuitry.  
       FIG. 6B  shows a semiconductor die  63  attached by an adhesive material  62  to the upper surface of the die paddle  60 . The adhesive material  62  may be dispensed, stamped, laminated, or applied by other means known in the art atop the die paddle  60 . The adhesive material  62  can be a silver-filled epoxy, a polyimide epoxy, a thermally-conductive epoxy, a thermally or electrically nonconductive epoxy, an adhesive tape, or a metal alloy. The adhesive material  62  is heated and cured, thereby securing the semiconductor die  63  to the die paddle  60 .  
      In  FIG. 6C , metal wires  64  are bonded between the semiconductor die circuitry (not shown) and the metal contacts  61 , connecting the die circuitry to external circuitry (not shown). The metal wires  64  may comprise gold, aluminum, copper or other suitable materials as are known in the art. An aperture member  66  is attached upon an optically-sensitive area of the die with a transparent adhesive material  65 . The transparent adhesive material  65  may be dispensed, stamped, laminated, or applied by other means known in the art to either upper surface of the semiconductor die  63  or the lower surface of the aperture member  66 .  
       FIG. 6D  shows a cross-sectional view of the present invention after the semiconductor die  63 , the aperture member  66 , and the upper portions of the die paddle  60  are encapsulated with an epoxy molding compound as is known in the art, forming a package  67  while leaving the upper surface of the aperture member  66  and lower surfaces of the metal contacts  61  exposed. Finally, as shown in  FIG. 6E , the individual package is punched out or cut from any attached frame to become a finished package.  
       FIGS. 7A through 7E  show the assembly of an embodiment especially suited for Ball Grid Array (BGA) or Land Grid Array (LGA) packages. As shown in  FIG. 7A , a Printed Circuit Board (PCB) substrate  71  comprising rubber, bismallimide triazene (BT), a ceramic, or other suitable material as is known in the art is configured to accommodate a desired semiconductor and related electrical circuitry.  
       FIG. 7B  shows a semiconductor die  73  attached by an adhesive material  72  to the upper surface of the substrate  71 . The adhesive material  72  may be dispensed, stamped, laminated, or applied by other means known in the art atop the substrate  71 . The adhesive material  72  can be a silver-filled epoxy, a polyimide epoxy, a thermally-conductive epoxy, a thermally or electrically nonconductive epoxy, an adhesive tape, or a metal alloy. The adhesive material  72  is heated and cured, thereby securing the semiconductor die  73  to the substrate  71 .  
      In  FIG. 7C , metal wires  74  are bonded between the PCB circuitry  79  and the semiconductor die circuitry (not shown). The metal wires  74  may comprise gold, aluminum, copper or other suitable materials as are known in the art. An aperture member  76  is attached upon an optically-sensitive area of the die with a transparent adhesive material  75 . The transparent adhesive material  75  may be dispensed, stamped, laminated, or applied by other means known in the art to either upper surface of the semiconductor die  73  or the lower surface of the aperture member  76 .  
       FIG. 7D  shows a cross-sectional view of the present invention after the semiconductor die  73 , the aperture member  76 , and the upper portions of the substrate  71  are encapsulated with an epoxy molding compound as is known in the art, forming a package  77  while leaving the upper surface of the aperture member  76  and lower surfaces of the substrate  71  exposed.  
       FIG. 7E  shows attachment of solder balls  78  to terminals on the lower side of the substrate  71  for a BGA package. The solder balls  78  are not required on an LGA package. Finally, the individual package is punched out or cut from any attached substrate to become a finished package.  
      As previously described, the optical member, semiconductor die, and die paddle of each embodiment of the present invention are bonded together directly with thin layers of adhesives, so that during sensor assembly each component is properly aligned with adjacent components without need for rings, ridges, bumps, or other component alignment features known in the art. The simplicity of this method allows a manufacturer considerable latitude in the dimensions and size variances of components. This latitude may be enhanced in many embodiments of the present invention by the use of flexible die paddle support strips.  
       FIG. 8A  shows an alternate embodiment of the die paddle  40  of the embodiment of  FIGS. 4A through 4E  with die paddle support strips  80  attached.  FIG. 8A  shows the die paddle  40  with two support strips  80 , each attached near the center of an opposing side of the die paddle  40 . Support strips are formed or attached prior to sensor assembly in any quantity or position deemed suitable for a particular sensor manufacturing operation. Support strips may be formed directly from a die paddle while or after the die paddle is stamped or wet-etched from a copper sheet. Alternatively, support strips may be attached using adhesives or other methods known in the art.  
       FIGS. 8B through 8E  show a sensor assembly that is essentially the same as that already described in  FIGS. 4A through 4E  and  FIGS. 5A through 5E , with the addition of support strips  80 . The same assembly process is used, with the addition of a trimming operation. During sensor assembly the support strips  80  are supported by a mold tool (not shown) as is known in the art. As shown in  FIG. 8E , the support strips protrude from the package  47  after the package  47  is molded. The protruding ends  81  are trimmed to be approximately flush with the surface of the package  47 , resulting in the finished sensor shown in  FIG. 8F .  
      The support strips  80  are usually made from thin copper sheet metal, although other metals or plastics or ceramics might be utilized for specific material characteristics. Since the support strips  80  are flexible, the presence of the support strips  80  during the assembly steps shown in  FIGS. 8B, 8C , and  8 D allows the die paddle  40  to move during component assembly in response to variations in the thickness of the die paddle  40 , semiconductor die  43 , optical member  46 , adhesive material  42 , transparent adhesive material  45 , and mold tools (not shown). Die paddle  40  motion during component assembly allows components to settle into optimum positions without the use of alignment structures. A manufacturer may then use components with greater dimensional variances while still producing sensor packages with required optical characteristics. A manufacturer may also use increased assembly pressure without damaging components. In a preferred embodiment, the die paddle  40  may be deflected up to 0.002 inch toward the lead frame.  
       FIGS. 9A through 9K  show the assembly of an alternate embodiment of the PLLP non-leaded surface mount application shown in  FIGS. 6A through 6F . The process may be applied to BGA, PCB, LGA, and other QFN assemblies.  FIG. 9A  shows a plan view of a portion of a lead frame  900 . In this embodiment the lead frame  900  is a flat plate made of materials known in the art. Die paddle assembly location pins  902  on the lead frame  900  form a perimeter that locates die paddle assemblies  910  upon the lead frame  900 .  FIG. 9A  shows four adjacent die paddle assemblies  910  disposed upon the lead frame  900 , but in a typical application the entire area within the die paddle assembly location pins  902  would be populated by similar die paddle assemblies  910 .  
      Lead frame runner slots  908  mate with mold tool runner slots  938  shown in  FIG. 9F . Mold tool location pins  904  mate with mold tool location holes  934  in the mold tool  930  shown in  FIG. 9F .  
       FIG. 9B  shows an enlarged view of four adjacent die paddle assemblies  910 . Die paddles  912  are supported by support strips  914  projecting diagonally from each corner of a die paddle  912 . Support strips  914  may be formed as a die paddle assembly  910  is stamped or wet-etched from a copper sheet, with the die paddle  912  simultaneously or subsequently formed upward or downward with respect to the plane of the metal contacts  916 . Although  FIG. 9A  shows a lead frame  900  having space for thirty-six component assemblies, a lead frame  900  may have space for any number of die paddle assemblies  910  allowed by the manufacturing system used.  
       FIG. 9C  shows a cross-sectional elevation view of the die paddle assemblies  910  of  FIG. 9B . Each die paddle  912  is supported at each corner by support strips  914  that raise the die paddle  912  above the lead frame  900 . As described above for the embodiments of  FIG. 8 , the support strips  914  are usually made from thin copper sheet metal, although other metals or plastics or ceramics might be utilized for specific material characteristics. Since the support strips  914  are flexible, the presence of the support strips  914  during the component assembly allows a die paddle  912  to move in response to variations in the thickness of the die paddle  912 , semiconductor die, optical member, adhesive material, transparent adhesive material, and mold tool. In a preferred embodiment, the die paddle  912  may be deflected up to 0.002 inch toward the lead frame  900 . Die paddle  912  motion during component assembly allows components to settle into optimum positions without the use of alignment structures. A manufacturer may then use components with greater dimensional variances while still producing sensor packages with required characteristics. A manufacturer may also use increased assembly pressure without damaging components. Attachment of support strips  914  to each corner of a die paddle  912  reduces undesirable die paddle positional deviations that may occur when only two support strips are used.  
       FIG. 9D  shows another cross-sectional elevation view of the die paddle assemblies  910  of  FIG. 9B , with the vertical dimensions of the die paddles  912  and metal contacts  916  somewhat exaggerated for clarity.  
       FIG. 9E  shows a cross-sectional elevation view of components assembled on the die paddle assemblies of  FIG. 9D . A semiconductor die  922  is attached by an adhesive material  920  to the upper surface of the die paddle  912 . A pick-and-place machine as is known in the art may according to its programming instructions select a semiconductor die  922  with any desired characteristics. Since in accordance with the method of the present invention each semiconductor die  922  is individually placed and affixed to a die paddle  912 , the pick-and-place machine may select a different type of semiconductor die  922  for each of any number of sequentially-assembled optoelectronic packages.  
      The adhesive material  920  may be dispensed, stamped, laminated, or applied by other means known in the art atop the die paddle  912 . The adhesive material  920  can be a silver-filled epoxy, a polyimide epoxy, a thermally-conductive epoxy, a thermally or electrically nonconductive epoxy, an adhesive tape, or a metal alloy. The adhesive material  920  is heated and cured, thereby securing the semiconductor die  922  to the die paddle  912 . Metal wires  928  are bonded between the semiconductor die circuitry (not shown) and the metal contacts  916 , connecting the die circuitry to external circuitry (not shown). The metal wires  928  may comprise gold, aluminum, copper or other suitable materials as are known in the art. In preferred embodiments, silver may be selectively plated on portions of the die paddle  912  and metal contacts  916  requiring gold bonds. Since mold compound does not adhere to silver, silver plating is avoided in other areas.  
       FIG. 9E  additionally shows an aperture member  926  as previously described, attached in a manner previously described upon an optically-sensitive area of the semiconductor die  922  with a transparent adhesive material  924  as is known in the art. The transparent adhesive material  924  may be dispensed, stamped, laminated, or applied by other means known in the art to either upper surface of the semiconductor die  922  or the lower surface of the aperture member  926 . The metal contacts  916 , metal wires  928 , die paddle  912 , adhesive material  920 , semiconductor die  922 , transparent adhesive material  924 , and aperture member  926  together comprise a component assembly  929 .  
       FIG. 9F  shows a portion of a plan view of a mold tool  930  with a mold cavity  932  and mold tool location holes  934 .  FIG. 9G  shows a cross-sectional elevation view of the mold tool of  FIG. 9F . Once components are assembled as shown in  FIG. 9E , the mold tool  930  is placed on the lead frame  900  with the mold cavity  932  facing the lead frame  900 . The mold tool  930  and lead frame  900  are aligned by mating mold tool location pins  904  with mold tool location holes  934 . Mold tools  930  with mold cavities  932  of different depths may be used to accommodate different component assemblies  929 .  
      Epoxy molding compound as is known in the art is injected through the lead frame runner slots  908  into the mold tool runner slots  938 , with pressure and molding compound distribution equalized between mold tool runner slots  938  by an equalizing channel  935  in the mold tool  930 . Molding compound then passes through gates  939  into the mold cavity  932  and envelopes the die paddles and assembled components. Air is forced out of the mold cavity  932  through vents  933  ( FIG. 9A ). Vents  933  exit the perimeter of the mold cavity  932  so that residual molding compound protruding into a vent may later be trimmed off during a routine trimming process. Vents  933  are preferentially of a significantly smaller diameter than gates  939  to limit the escape of molding compound.  
       FIG. 9H  shows a portion of a cross-sectional elevation view of the present invention after the component assemblies  929  are enclosed by the mold tool  930 . The edges  936  of the mold cavity  932  contact the lead frame  900  outside of the die paddle assembly location pins  902 , mating closely enough to the lead frame  900  to minimize leakage of molding compound. Injected molding compound encapsulates all components except the lower surfaces of the metal contacts  916  and the upper surfaces of the aperture members  926 . The mold tool  930  is then removed, the encapsulated component assemblies  929  are removed from the lead frame  900 , and individual component assemblies are singulated and trimmed with a saw or water-assisted laser to form individual optoelectronic packages as shown in  FIG. 9J .  FIG. 9K  shows a cross-sectional perspective view of a singulated optoelectronic package.  
      The embodiments described above utilize pre-cut aperture members rather than wafer-sized sheets, eliminating extra cutting steps and allowing increased flexibility in selecting the size, position, and optical characteristics of each embedded window. An aperture member  926  made of borosilicate glass or other suitable material known in the art is placed by a pick-and-place machine on the upper surface of transparent adhesive  924 , affixing the aperture member  926  to the transparent adhesive  924  and the optically active upper surface of the semiconductor die  922 , forming a transparent aperture above the optically active upper surface. The pick-and-place machine may according to its programming instructions select an aperture member with any desired characteristics. Since in accordance with the method of the present invention each aperture member is individually placed and affixed to a semiconductor die, the pick-and-place machine may select a different type of aperture member for each of any number of sequentially-assembled optoelectronic packages.  
      The principles, embodiments, and modes of operation of the present invention have been set forth in the foregoing specification. The embodiments disclosed herein should be interpreted as illustrating the present invention and not as restricting it. For example, it should be recognized that a lead frame might be replaced with a printed circuit board (PCB) or a wired circuit board (WCB), and that an optoelectronic sensor might be replaced by a light-emitting semiconductor. Additionally, the assembly steps may be varied from the orders described, and in each case prior to assembly the transparent adhesive may be applied first to the aperture member or to both the die and the aperture member. In any embodiment of the present invention a pick-and-place machine may select a different type of semiconductor die and/or aperture member for each of any number of sequentially-assembled optoelectronic packages.  
      The foregoing disclosure is not intended to limit the range of equivalent structure available to a person of ordinary skill in the art in any way, but rather to expand the range of equivalent structures in ways not previously contemplated. Numerous variations and changes can be made to the foregoing illustrative embodiments without departing from the scope and spirit of the present invention.