Abstract:
An optoelectronic component has a lens that is formed in the surface of an encapsulant surrounding a semiconductor diode element. With respect to emitters, the lens reduces internal reflection and reduces dispersion to increase overall efficiency. With respect to detectors, the lens focuses photons on the active area of the detector, increasing detector sensitivity, which allows a detector having a reduced size and reduced cost for a given application. The lens portion of the encapsulant is generally non-protruding from the surrounding portions of the encapsulant reducing contact surface pressure caused by the optoelectronic component. This non-protruding lens is particularly useful in pulse oximetry sensor applications. The lens is advantageously formed with a contoured-tip ejector pin incorporated into the encapsulant transfer mold, and the lens shape facilitates mold release.

Description:
CLAIM OF PRIORITY  
       [0001]     This application a continuation of U.S. patent application Ser. No. 10/337,058, filed Jan. 3, 2003, which is a divisional of U.S. patent application Ser. No. 09/038,494 filed Mar. 10, 1998 (now U.S. Pat. No. 6,525,386). The present application also incorporates the foregoing utility disclosures herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to the field of optoelectronics, which includes light emitting components, such as light emitting diodes (LED) and laser diodes, and which also includes light detecting components, such as photodiodes, phototransistors, photodarlingtons and photovoltaic cells. Optoelectronics also includes various devices which incorporate optoelectronic components, such as displays, photosensors, optocouplers, and fiberoptic transmitters and receivers. In particular, this invention relates to lenses to increase the efficiency of optoelectronic emitters and the sensitivity of optoelectronic detectors.  
         [0004]     2. Description of the Related Art  
         [0005]     A prior art LED  100  is shown in  FIG. 1  and consists of a semiconductor diode element  110  electrically connected to a leadframe  120  and surrounded by an encapsulating material  130 . The diode element  110  is typically mounted to one lead  122  of the leadframe  120  and connected to a second lead  124  of the leadframe  120  by a wire bond  140 . These two leads provide an electrical connection between an external current source and the anode and cathode of the diode element  110 . The external current source supplies power to the diode device  100  that is converted to emitted light by the photoelectric effect, which occurs at the semiconductor junction within the diode element  110 .  
         [0006]     Internal inefficiencies within a semiconductor diode result in very low net efficiencies, which is the ratio of emitted light power to input power. Internal inefficiencies arise from a low ratio of minority carriers injected into the diode semiconductor junction to photons generated at the junction; photon loss due to internal reflection at the semiconductor/encapsulant interface; and absorption of photons within the semiconductor material. Because of these low net efficiencies, many LED applications require high input current, resulting in heat dissipation and device degradation problems in order to obtain sufficient light.  
         [0007]     As illustrated in  FIG. 1 , the encapsulant  130  forms a flat light-transmitting surface  150 . A flat surface is convenient in many applications where the LED is mounted to another surface that is also generally flat or in applications that otherwise cannot accommodate a protruding surface. The inefficiencies described above, however, are compounded by the configuration of the LED encapsulant/air interface. An encapsulant having a flat surface, such as in  FIG. 1 , allows photons transmitted by the diode element  110  to have considerable dispersion. A flat encapsulant surface also results in internal reflection at the encapsulant/air interface, further reducing photon transmission and increasing photon absorption within the encapsulant material.  
         [0008]      FIG. 2  illustrates a prior art LED  200  having an encapsulant  230  that forms a spherical surface  250 . A spherical or other curved surface gives a larger angle of incidence for photons emitted from the semiconductor diode element  210 , reducing losses due to internal reflection. Further, this surface  250  acts as a lens to reduce the dispersion of generated photons. Unfortunately, a protrusion, such as this curved surface, is difficult to accommodate in many applications.  
       SUMMARY OF THE INVENTION  
       [0009]     An optoelectronic device according to the present invention incorporates a lens that increases component performance. For example, the output of an LED utilizing the lens is increased by, in part, reducing internal reflection. Internal reflection results from the differing indices of refraction at the interface between the LED encapsulant and the surrounding air.  
         [0010]     As shown in  FIG. 3 , when a light ray  310  passes from a media having a higher index of refraction  320  to a media having a lower index of refraction  330 , the ray  310  is refracted away from the normal  340  to the surface  350 . The angle, θ 1 , is customarily referred to as the angle of incidence  370  and the angle θ 2  is customarily referred to as the angle of refraction  380 . As the angle of incidence  370  is increased, the angle of refraction  380  increases at a greater rate, in accordance with Snell&#39;s Law: 
 
sin θ 2 =(N 1 /N 2 )sin θ 1 , 
 
 where (N 1 &gt;N 2 ). When the angle of incidence  370  reaches a value such that sin θ 1 =N 2 /N 1 , then sin θ2=1.0 and θ 2 =90°. At this point none of the light is transmitted through the surface  350 , the ray  310  is totally reflected back into the denser medium  320 , as is any ray which makes a greater angle to the normal  340 . The angle at which total reflection occurs: 
 
θ c =arcsin N 2 /N 1  
 
 is referred to as the critical angle. For an ordinary air-glass surface, where the index of refraction is 1.5, the critical angle is about 42°. For an index of 1.7, the critical angle is near 36°. For an index of 2.0, the critical angle is about 30°. For an index of 4.0, the critical angle is about 14.5°. 
 
         [0011]     An optoelectronic device according to the present invention has an encapsulant that functions as a lens. For emitter applications, the lens reduces internal reflection and dispersion without having a protruding curved surface. Thus, LEDs utilizing the present invention have an improved efficiency compared with prior art flat-surfaced LEDs and similar devices, without the physical interface difficulties of the prior art curved-surface LEDs and similar devices. For detector applications, the lens focuses photons on the active area of the detector, increasing detector sensitivity. This increased detector sensitivity allows a detector having a reduced size, hence a reduced cost, to be used for a given application.  
         [0012]     A particularly advantageous application of an optoelectronic device with a non-protruding lens is in pulse oximetry, and in particular, as an emitter in pulse oximetry probes. Pulse oximetry is the noninvasive measurement of the oxygen saturation level of arterial blood. Early detection of low blood oxygen saturation is critical because an insufficient supply of oxygen can result in brain damage and death in a matter of minutes. The use of pulse oximetry in operating rooms and critical care settings is widely accepted.  
         [0013]     A pulse oximetry probe is a sensor having a photodiode which detects light projected through a capillary bed by, typically, red and infrared LED emitters. The probe is attached to a finger, for example, and connected to an instrument that measures oxygen saturation by computing the differential absorption of these two light wavelengths after transmission through the finger. The pulse oximetry instrument alternately activates the LED emitters then reads voltages indicating the resulting intensities detected at the photodiode. A ratio of detected intensities is calculated, and an arterial oxygen saturation value is empirically determined based on the ratio obtained: 
 
I rd /I ir =Ratio         % O 2  Saturation 
 
         [0014]     Typically, a look up table or the like correlates the Ratio to saturation. The use of conventional LEDs within pulse oximetry probes has a number of drawbacks. Pulse oximetry performance is limited by signal-to-noise ratio which, in turn, is improved by high light output emitters. LEDs without lenses, such as illustrated in  FIG. 1 , are not optimized to transmit the maximum amount of light into the skin. LEDs with protruding lenses, such as illustrated in  FIG. 2 , create increased pressure on the skin, resulting in perfusion necrosis, i.e. a reduction of arterial blood flow, which is the medium to be measured. A solution to this problem in accordance with the present invention is an LED incorporating a non-protruding lens.  
         [0015]     One aspect of the present invention is an optoelectronic device that comprises an encapsulant having a surface, a lens portion of the surface, and a filler portion having a generally planar surface. The filler portion is disposed around the lens, and the lens does not extend substantially beyond the plane of the generally planar surface. The optoelectronic device also comprises an optoelectronic element embedded in the encapsulant and operable at at least one wavelength of light. The lens being configured to transmit or receive the at least one wavelength.  
         [0016]     Another aspect of the present invention is a mold tool for an optoelectronic device that comprises a first mold piece having a surface that defines a first cavity and an aperture within the first cavity. The mold tool also comprises a second mold piece having a surface which defines a second cavity. The first cavity and second cavity cooperate to form a molding compound into a predetermined shape. The mold tool further comprises an ejector pin having a contoured tip. The pin is movably located within the aperture between a first position retracted within the cavity and a second position extended from the aperture. In the first position, the tip constitutes an integral portion of the first cavity. In the second position, the ejector pin facilitates removal of the compound from the first cavity. The ejector pin tip at least partially defines the predetermined shape.  
         [0017]     Another aspect of the present invention is an optoelectronic method comprising the steps of providing a generally planar surface at a predefined distance from an optoelectronic element, defining a light transmissive region of that surface within the critical angle of the optoelectronic element, and contouring the surface within the transmissive region without exceeding the predefined distance. These steps create a non-protruding lens for the optoelectronic element. In one embodiment, the transmissive region has a circular cross-section. The optoelectronic method can comprise the further step of shaping a surrounding region adjacent said transmissive region.  
         [0018]     Yet another aspect of the present invention is an optoelectronic device comprising an encapsulant means for embedding an optoelectronic element and a lens means for conveying light between the optoelectronic element and a media surrounding the encapsulant means. In one embodiment, the optoelectronic device further comprises a flat surface means for providing a low-pressure contact surface for the lens means. In that embodiment, the optoelectronic device can further comprise an arcuate surface means for avoiding total internal reflection of light from the flat surface means. In another embodiment, the optoelectronic device further comprises a surrounding surface means for providing a contact surface for the encapsulant from which the lens means does not protrude. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The present invention is described in detail below in connection with the following drawing figures in which:  
         [0020]      FIG. 1  is a cross-section view of a prior art LED having an encapsulant with a flat light-transmitting surface;  
         [0021]      FIG. 2  is a cross-section view of a prior art LED incorporating a protruding, spherical light-transmitting surface;  
         [0022]      FIG. 3  generally illustrates light refraction at a surface between two media having different indices of refraction;  
         [0023]      FIG. 4  is a cross-section view of an LED incorporating a single emitter and a flat-surfaced, vertical-side lens according to the present invention;  
         [0024]      FIG. 5A  is a plan view of an LED incorporating dual-emitters and a flat-element, non-protruding lens;  
         [0025]      FIG. 5B  is an enlarged view of a portion of  FIG. 5A  illustrating the critical angle;  
         [0026]      FIG. 6  is a plan view of another LED incorporating dual-emitters and a spherical-element, non-protruding LED lens;  
         [0027]      FIG. 7A  is a plan view of the lower cavity of a production mold tool for encapsulating an optoelectronic element;  
         [0028]      FIG. 7B  is a plan view of the upper cavity of a production mold tool for encapsulating an optoelectronic element;  
         [0029]      FIG. 7C  is a cross section view of the upper cavity and the lower cavity of a production mold tool in a closed position;  
         [0030]      FIG. 8A  is an illustration of a prior art ejector pin for a production mold tool;  
         [0031]      FIG. 8B  is a cross-section view of a prior art ejector pin tip;  
         [0032]      FIG. 9  is a cross-section view of a non-protruding optoelectronic lens being formed in a mold tool with a contoured ejector pin tip according to the present invention;  
         [0033]      FIG. 10A  is a cross-section view of an ejector pin tip for creating a non-protruding optoelectronic lens featuring a flat surface element;  
         [0034]      FIG. 10B  is a cross-section view of an ejector pin tip for creating a non-protruding optoelectronic lens featuring a spherical surface element; and  
         [0035]      FIG. 10C  is a cross-section view of an ejector pin tip for creating a detector cavity. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0036]      FIG. 4  illustrates an embodiment of an LED having a non-protruding or minimally protruding lens according to the present invention. The LED  400  consists of at least one semiconductor diode element  410 , which is mounted to one lead of a leadframe  420  and connected to another lead of a leadframe  420  with a bond wire  440 . The diode element  410 , bond wire  440  and portions of the leadframe  420  are surrounded by an encapsulant  430 . A lens  460  is molded into a portion of the encapsulant  430 . The lens  460  has a generally flat, surface portion  462  that is at or below the plane of the surrounding surface portions  434  of the encapsulant  430 . The lens extends radially from the diode element  410  out to the critical angle  464 , at which point total internal reflection of photons emitted from the diode element would occur. Past the critical angle  464 , the lens  460  has a steep side surface portion  466 , which extends below the surface of the surrounding filler portion  434  of the encapsulant  430  to prevent internal reflection. A trough  468  is located between the flat surface portion  462  of the lens  460  and the surface of the surrounding filler portion  434  of the encapsulant  430 . Due to refraction, light rays exiting the side surface portion  466  are bent towards the lens  460 , reducing dispersion as compared to the prior art LED of  FIG. 1 .  
         [0037]     Manufacturability considerations may limit the lens embodiment described above. If the lens side surface portion  466  is too steep, the LED may be difficult to release from the encapsulant mold. Further, the depth of the trough  468  may restrict the flow of encapsulant during the molding process and may also interfere with the bond wire  440 . Optical considerations also may constrain this embodiment. The sharp transition  465  between the flat surface portion  462  and side surface portion  466  of the lens  460  results in an abrupt directional change of light rays exiting the lens  460  on either side of this transition  465 , which may be problematic in some applications.  
         [0038]      FIG. 5A  illustrates an embodiment of a non-protruding lens LED for pulse oximetry applications. Pulse oximetry requires transmission of two wavelengths. Thus, this LED  500  utilizes dual semiconductor diode elements, a “red emitter”  512  producing wavelengths in the red portion of the spectrum and an “IR emitter”  514  producing infrared wavelengths. One type of red emitter is an AlGaAs chip available from, among others, Opto Tech Corporation, Hsinchu Science-Based Industrial Park, Taiwan, R.O.C., part number ED-014-UR/3. This part has a peak emission at 660±3 nm and a radiant power of 1.3 mW minimum. One type of IR emitter is a GaAs chip available from, among others, Infratech Corporation, 10440 Miller Road, Dallas, Tex., part number INF905N13H. This part has a peak emission at 905±10 nm and a radiant power of 1.8 mW typical.  
         [0039]     The cathode side of the red emitter  512  is mounted to a first lead  522  and the cathode side of the IR emitter is mounted to a second lead  524 . A third lead  528  is unused. A first bond wire  542  connects the anode side of the red emitter  512  to the second lead  524 . A second bond wire  544  connects the anode side of the IR emitter  514  to the first lead  522 . With this configuration, the red emitter  512  and IR emitter  514  are electrically connected in parallel and “back-to-back,” i.e. cathode to anode. In this manner, the red emitter  512  and IR emitter  514  are activated one at a time by alternating the polarity of a voltage applied between the first lead  522  and second lead  524 .  
         [0040]     The semiconductor diode elements  512 ,  514 , the leads  522 ,  524 ,  528  and associated bond wires  542 ,  544  are all encapsulated after the mounting and bonding process. Encapsulation is accomplished with a transfer mold process as described in detail below. The encapsulant  530  is molded into a standard-sized planar package having a length, L, of 220 mils, a width, W, of 170 mils and a thickness, T, of 70 mils. This forms a light transmitting side  502  and a backside  504  for the LED  500 . One available encapsulant is HYSOL® MG18, which is from The Dexter Corporation, Electronic Materials Division, Industry, Calif. The index of refraction, I R , for MG18 is 1.52. Thus, the critical angle, θ c , is arcsin(1/1.52)=41.1°. Another available encapsulant is NT-300H, which is from Nitto Denko America, Inc., 55 Nicholson Lane, San Jose, Calif. The index of refraction and critical angle for NT-300H is I R =1.564 and θ c =39.7° 
         [0041]     A lens is advantageously formed in the encapsulant during the molding process, as further described below. The light transmitting side  502  of the encapsulant  530  contains a contoured region  550  and a flat, filler region  570 . The contoured region  550  is a shaped-surface within a circular cross-section 125 mils in diameter. The flat region  570  is a planar surface that surrounds the contoured region  550 . Within the contoured region  550  are a lens  560  and a trough  552  having a sidewall  554 . The lens  560  has a circular cross-section  563 , a flat surface element  564 , and an arcuate surface element  568 . The flat surface element  564  is a substantially flat, circular portion of the lens  560  having a 30-mil diameter in one embodiment. The arcuate surface element  568  is a curved portion of the lens  560  having a 25-mil radius extending from the edge of the flat surface element  564  to the beginning of the trough  552  in one embodiment. The trough  552  has a depth of 22 mils and a bottom width of 4.2 mils in one embodiment. The sidewall  554  is constructed at an angle of 50° with respect to the flat region  570 . With the lens configuration described above, the flat surface element  564  of the lens  560  is in the same plane as the flat region  570  surrounding the lens. This creates a non-protruding lens surface, which avoids pressure necrosis when the emitter with a lens in accordance with the present invention is used is a sensor.  
         [0042]     As depicted in  FIG. 5B , if the center of an emitter  512  is assumed to be a point source, the maximum distance, B, along the flat surface element before total internal reflection of light occurs is calculated as follows: 
 
A=the distance to the lens surface 
 
=thickness of encapsulant top-half−lead thickness−½ emitter thickness=(50−10−4)=36 mil 
 
 B/A =tan (π·θ c /180°)=0.83, for θ c =39.7°, therefore 
 
B=0.83·36≈30 mil 
 
 Thus, the entirety of the flat surface element  564 , which has a diameter of 30 mil, is within the critical angle of light rays from either the red emitter  512  or the IR emitter  514 , as illustrated in  FIG. 5B  and by the calculations above. 
 
         [0043]     The red emitter  512  is advantageously mounted only slightly offset with respect to the center of the lens  560 . Although there is no total internal reflection of light from either emitter  512 ,  514  at any portion of the flat surface element  564 , internal reflection increases as the incident angle approaches the critical angle. The red emitter  512  has a lower efficiency as compared to the IR emitter  514 , as apparent from the 1.3 mW versus 1.8 mW radiant power, respectively, for the parts described above. The placement of the red emitter  512  near the lens center minimizes losses from internal reflection in the red spectrum to somewhat compensate for the red emitter&#39;s lower efficiency. This placement, however, is somewhat at the expense of the IR emitter  514 , which has a higher efficiency and is, accordingly, mounted near the periphery of the lens  560  due to the space constraints imposed by the red emitter  512  placement and the configuration of the leads  522 ,  524  and bond wires  542 ,  544 . At its location, the IR emitter  514  may incur significant internal reflection at portions of the lens  560  and uncalculated optical effects due to the proximity of the trough  552  and the trough sidewall  554 .  
         [0044]     The embodiment illustrated in FIGS.  5 A-B overcomes the limitations of the non-protruding LED lens described with respect to  FIG. 4 . The trough  552  is shallow enough to allow encapsulant flow and to avoid bond wires. The sidewall  554  is angled to allow easy release of the part from the molding tool. The arcuate portion  568  provides a smooth transition between the flat surface portion  564  and the trough  552  to reduce corner effects.  
         [0045]      FIG. 6  illustrates another preferred embodiment of the LED that incorporates a non-protruding spherical lens. As in the embodiment described with respect to FIGS.  5 A-B, the light transmitting side  502  of the encapsulant  530  contains a contoured region  550  and a flat, filler region  570 . The contoured region  550  and flat region  570  are as described above. Within the contoured region  550  are a lens  660  and a trough  652  having a sidewall  654 . The lens  660  has a spherical surface element  664  having a curved surface with a radius of 50 mils. In this configuration, the trough  652  has a depth of 25 mils and a bottom width of 2.7 mils. The sidewall  654  is constructed at an angle of 56° 35′ with respect to the flat region  570 . With the lens configuration described above, the apex portion of the spherical surface element  664  is in the same plane as the flat region  570  surrounding the lens. As with the lens described with respect to FIGS.  5 A-B, this creates a non-protruding lens surface, which avoids pressure necrosis. One of ordinary skill in the art will recognize that other lens shapes are also feasible within the scope of the current invention, such as a lens with a parabolic surface element.  
         [0046]      FIG. 7A  depicts top, front and side views of the lower cavity portion  710  of a production transfer mold for encapsulating an LED according to the present invention. An available mold has 200 cavities and is manufactured by Neu Dynamics Corp., 110 Steamwhistle Drive, Ivyland, Pa., part number 97-3239. As shown in  FIG. 7A , the lower cavity portion  710  has a cavity  720  for each LED to be molded. Placed into this mold are leadframe strips each containing the components for multiple LEDs. Each cavity has portions  722  to accommodate the three leadframe leads allocated to each LED. Each cavity  720  also has a gate  724  through which encapsulant is injected during the molding process, which is described in detail below. A vent  728  allows excess encapsulant and air to be ejected from the cavity. The depth of each cavity  720  is 50 mils, which, with reference to  FIG. 5B , corresponds to the thickness, T u , of the encapsulant upper half.  
         [0047]     Each cavity  720  in the lower cavity portion  710  of the mold tool contains an ejector pin  800 . When the mold press is opened, these ejector pins  800  protrude into the cavities  720 , separating the encapsulated leadframes from the mold tool and allowing removal of the encapsulated leadframes. Within each cavity  720  is an aperture  732  that accommodates the ejector pin tip  1000  as described below. The ejector pin  800  for each cavity is installed in a shaft  734  in the body of the lower cavity portion  710 .  
         [0048]      FIG. 7B  depicts the upper cavity portion  760  of the production transfer mold corresponding to  FIG. 7A . As shown in  FIG. 7B , the upper cavity portion  760  has a cavity  770  for each LED to be molded. The depth of each cavity  770  is 20 mils, which, with reference to  FIG. 5B , corresponds to the thickness, T 1 , of the encapsulant lower half. The production mold, including the lower  710  and upper  760  cavity mold portions are mounted on lower and upper platens, respectively, of a standard production press. An available press is an 83-ton press manufactured by Fujiwa Seiki, model number TEP75-30, available from ESC International, Four Ivybrook Blvd., Ivyland, Pa.  
         [0049]     A transfer molding process is utilized to encase the semiconductor diode elements, interconnecting gold bond wire and leadframe within a thermosetting epoxy resin, which is optically transmissive. Further conventional processing results in a completed LED device. Initially, the mold tool is brought to an operating temperature between 140-175° C. The mold tool is brought to an open position. One or more leadframes having multiple leads  522 ,  524 ,  528 , mounted emitters  512 ,  514  and bond wires  542 ,  544  are loaded into a carriage so that the emitters  512 ,  514  will be face down in the lower mold cavities  720 , which form the light emitting side  502  of the encapsulant  530 . The leadframe carriage is then preheated to 325° F. and loaded into the mold tool. The mold press is closed, exerting maximum pressure on the mold tool. Mold compound pellets, which have been preheated for approximately 25 seconds to the consistency of a marshmallow are then loaded into a mold compound pot. A transfer ram injects the molten encapsulant into each cavity gate  724  at a pressure of between 500-1000 psi, and air and excess encapsulant are ejected through each cavity vent  728 . The mold cycle time is between 2-5 minutes and nominally 3:00 minutes. After transfer molding, the clear molding resin is cured in an oven at 150° C.±10° C. for 2-4 hours.  
         [0050]      FIG. 7C  shows a side, cross-section view of the upper cavity portion  760  and the lower cavity portion  710  of the mold tool in the closed position. The upper cavity portion  760  is shown attached to the upper mold tool base  780  with bolts  782 . The lower cavity portion  710  is shown attached to the lower mold tool base  740  with bolts  742 . In this closed position, each upper cavity  770  and lower cavity  720  together form a whole cavity  790  that accepts and shapes mold compound to form the LED encapsulant. Also shown is a cavity ejector pin  800  that functions as described above for separating an encapsulated leadframe from the mold tool. In addition, there is a runner ejector pin  744  that functions similarly to the cavity ejector pin  800  to separate an encapsulated leadframe from the mold tool. A runner holddown pin  784  serves to position a leadframe within the mold tool.  
         [0051]      FIG. 8A  illustrates a conventional ejector pin  800 . The pin  800  has a base  810 , a rod  820  and a tip  830 .  FIG. 8B  illustrates the flat surface at the tip  830  of a prior art ejector pin  800 . A pin  801  with a contoured tip  1000  according to the present invention, as described below with respect to FIGS.  10 A-B, is installed in the shaft  734  of the lower cavity portion  710  described with reference to  FIG. 7A . The rod  820  can freely slide within the shaft  734  such that the tip  1000  is flush with or protrudes into the cavity  720  through the aperture  732 . A separate portion of the mold tool presses against the base  810  to actuate the ejector pin  800  when the press is opened or closed. With the prior art ejector pin  800 , discontinuities between the pin tip  830  and the surrounding tool and the fact that the pin tip  830  is not exactly flush with the surrounding tool result in imperfections on the surface of the mold compound. This undesirable ejector pin mark typically has to be polished off or placed on a portion of the molded part where the mark has no effect. With respect to molding LED devices, the ejector pin mark can distort the optical properties of the LED encapsulant surface. As a result, in a typical LED molding process, ejector pins are placed on the backside or non-emitting surface of the LED.  
         [0052]      FIG. 9  illustrates a mold tool that advantageously utilizes the presence of the ejector pin in each mold cavity to shape the mold compound. This is in stark contrast to the prior art, which attempts to minimize the ejector pin effect. With respect to molding an LED, such as that shown in  FIG. 6 , the ejector pin  800  is located such that it contacts the light transmitting surface  502  of the LED  600 , rather than the backside surface  504 . The ejector pin  800  is located within a cavity  720  of the lower cavity portion  710  of the mold tool so that it becomes an integral part of the molding process. As illustrated in  FIG. 9 , the pin tip  1000  is contoured to form the lens  660 , trough  652  and trough sidewall  654  of the LED  600 .  
         [0053]     The ejector pin  801  according to the present invention functions both to remove the molded parts from the tool and impart a contour to the surface of the LED. As shown in  FIG. 9 , in the mold tool closed position, the ejector pin  801  provides a shaped surface for molding a lens  660  into the encapsulant  530 . In the mold tool open position, the ejector pin  801  serves the function of separating the encapsulated LED  600  from the mold tool  710  to facilitate removal.  
         [0054]      FIG. 10A  illustrates an embodiment of a contoured-tip ejector pin according to the present invention. The ejector pin tip  1000  is advantageously shaped to create an LED  500  having a non-protruding lens  560  with a flat surface element  564  corresponding to the illustration of  FIG. 5A . The ejector pin tip  1000  of  FIG. 10A  has an optically ground and polished flat circular surface  1010  of 30 mil diameter which corresponds to the flat surface element  564  of the LED lens  560 . The ejector pin tip  1000  also features a curved portion  1020  of 25 mil radius, R 1 , blending into the flat surface  1010  which is similarly ground into the pin tip  1000  and which corresponds to the arcuate surface element  568  of the LED lens  560 . The pin tip  1000  has a combination of a 50° angle, θ 1 , and a 0.023 inch height, D 1 , taper  1030  ground and optically polished on the outer diameter of the pin tip  1000  which corresponds to the LED encapsulant sidewall  554 . The tip area  1040  between the curved portion  1020  and taper  1030  corresponds to the LED encapsulant trough  552 .  
         [0055]      FIG. 10B  illustrates another embodiment of a contoured-tip ejector pin according to the present invention. The ejector pin tip  1000 A is advantageously shaped to create an LED  600  having a non-protruding lens  660  with a spherical surface element  664  corresponding to the illustration of  FIG. 6 . The ejector pin tip  1000 A of  FIG. 10B  has an optically ground and polished spherical dome  1060  of 50-mil radius, R 2 , which corresponds to the spherical surface element  664 . The tip  1000 A also has a 56°, 35′ angle, θ 2 , and 0.025 inch height, D 2 , taper  1070  ground and optically polished on the outer diameter of the pin tip  1000 A which corresponds to the encapsulant sidewall  654 . The tip area  1080  between the spherical dome  1060  and taper  1070  corresponds to the encapsulant trough  652 . Neu Dynamics, Ivyland, Pa., is capable of manufacturing ejector pins with contoured tips such as shown in FIGS.  10 A-B.  
         [0056]      FIG. 10C  illustrates yet another embodiment of a contoured-tip ejector pin according to the present invention. The ejector pin tip  1000 B is advantageously shaped to create a generally cone-shaped chamber in the encapsulant to concentrate or “funnel” energy onto the surface of a detector element embedded in the encapsulant. This creates a one-piece detector device that functions similarly to a photodetector mounted within a separate chamber, as described in U.S. Pat. No. 5,638,818 and assigned to the assignee of the present invention. The tip  1000 B features a taper  1090  that is ground and optically polished on the outer diameter of the pin tip  1000 B and that corresponds to the chamber walls.  
         [0057]     The non-protruding optoelectronic lens and associated contoured-tip ejector pins have been disclosed in detail in connection with the various embodiments of the present invention. These embodiments are disclosed by way of examples only and are not to limit the scope of the present invention, which is defined by the claims that follow. One of ordinary skill in the art will appreciate many variations and modifications within the scope of this invention. For example, although the current invention was described above mostly with respect to LED embodiments, the current invention also applies to non-protruding lenses for encapsulated photodiode detectors and to detector cavities.