Abstract:
A lighting component including a plurality of die transferred to the glass substrate. The transfer occurs by positioning the glass substrate to face a first surface of a die carrier carrying multiple die. A reciprocating transfer member thrusts against a second surface of the die carrier to actuate the transfer member thereby causing a localized deflection of the die carrier in a direction of the surface of the glass substrate to position an initial die proximate to the glass substrate. The initial die transfers directly to a circuit trace on the glass substrate. At least one of the die carrier or the transfer member is then shifted such that the transfer member aligns with a subsequent die on the first surface of the die carrier. The acts of actuating, transferring, and shifting are repeated to effectuate a transfer of the multiple die onto the glass substrate.

Description:
CROSS REFERENCE TO RELATED PATENT APPLICATIONS 
       [0001]    This application is a continuation of and claims priority to U.S. patent application Ser. No. 15/074,994, filed on Mar. 18, 2016, entitled “Method for Transfer of Semiconductor Devices,” which is a continuation of and claims priority to U.S. patent application Ser. No. 14/939,896, filed on Nov. 12, 2015, entitled “Method and Apparatus for Transfer of Semiconductor Devices,” which is now patented as U.S. Pat. No. 9,633,883, and which claims priority to U.S. Provisional Patent Application No. 62/146,956, filed on Apr. 13, 2015, and to U.S. Provisional Patent Application No. 62/136,434, filed on Mar. 20, 2015, which applications are hereby incorporated in their entirety by reference. 
     
    
     BACKGROUND 
       [0002]    Semiconductor devices are electrical components that utilize semiconductor material, such as silicon, germanium, gallium arsenide, and the like. Semiconductor devices are typically manufactured as single discrete devices or as integrated circuits (ICs). Examples of single discrete devices include electrically-actuatable elements such as light-emitting diodes (LEDs), diodes, transistors, resistors, capacitors, fuses, and the like. 
         [0003]    The fabrication of semiconductor devices typically involves an intricate manufacturing process with a myriad of steps. The end-product of the fabrication is a “packaged” semiconductor device. The “packaged” modifier refers to the enclosure and protective features built into the final product as well as the interface that enables the device in the package to be incorporated into an ultimate circuit. 
         [0004]    The conventional fabrication process for semiconductor devices starts with handling a semiconductor wafer. The wafer is diced into a multitude of “unpackaged” semiconductor devices. The “unpackaged” modifier refers to an unenclosed semiconductor device without protective features. Herein, unpackaged semiconductor devices may be called semiconductor device dies, or just “dies” for simplicity. A single semiconductor wafer may be diced to create dies of various sizes, so as to form upwards of more than 100,000 or even 1,000,000 dies from the semiconductor wafer (depending on the starting size of the semiconductor), and each die has a certain quality. The unpackaged dies are then “packaged” via a conventional fabrication process discussed briefly below. The actions between the wafer handling and the packaging may be referred to as “die preparation.” 
         [0005]    In some instances, the die preparation may include sorting the dies via a “pick and place process,” whereby diced dies are picked up individually and sorted into bins. The sorting may be based on the forward voltage capacity of the die, the average power of the die, and/or the wavelength of the die. 
         [0006]    Typically, the packaging involves mounting a die into a plastic or ceramic package (e.g., mold or enclosure). The packaging also includes connecting the die contacts to pins/wires for interfacing/interconnecting with ultimate circuitry. The packaging of the semiconductor device is typically completed by sealing the die to protect it from the environment (e.g., dust). 
         [0007]    A product manufacturer then places packaged semiconductor devices in product circuitry. Due to the packaging, the devices are ready to be “plugged in” to the circuit assembly of the product being manufactured. Additionally, while the packaging of the devices protects them from elements that might degrade or destroy the devices, the packaged devices are inherently larger (e.g., in some cases, around 10 times the thickness and 10 times the area, resulting in 100 times the volume) than the die found inside the package. Thus, the resulting circuit assembly cannot be any thinner than the packaging of the semiconductor devices. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The Detailed Description is set forth with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical items. Furthermore, the drawings may be considered as providing an approximate depiction of the relative sizes of the individual components within individual figures. However, the drawings are not to scale, and the relative sizes of the individual components, both within individual figures and between the different figures, may vary from what is depicted. In particular, some of the figures may depict components as a certain size or shape, while other figures may depict the same components on a larger scale or differently shaped for the sake of clarity. 
           [0009]      FIG. 1  illustrates an isometric view of an embodiment of a transfer apparatus. 
           [0010]      FIG. 2A  represents a schematic view of an embodiment of a transfer apparatus in a pre-transfer position. 
           [0011]      FIG. 2B  represents a schematic view of an embodiment of a transfer apparatus in a transfer position. 
           [0012]      FIG. 3  illustrates an embodiment of a shape profile of the end of a needle of a transfer mechanism. 
           [0013]      FIG. 4  illustrates an embodiment of a needle actuation stroke profile. 
           [0014]      FIG. 5  illustrates a plan view of an embodiment of a product substrate having a circuit trace thereon. 
           [0015]      FIG. 6  illustrates a schematic view of an embodiment of elements of a die transfer system. 
           [0016]      FIG. 7  illustrates a schematic view of an embodiment of a circuitry path between machine hardware and controllers of a die transfer system. 
           [0017]      FIG. 8  illustrates a method of a die transfer process according to an embodiment of this application. 
           [0018]      FIG. 9  illustrates a method of a die transfer operation according to an embodiment of this application. 
           [0019]      FIG. 10  illustrates an embodiment of a direct transfer apparatus and process implementing a conveyor system. 
           [0020]      FIG. 11A  illustrates a schematic view of another embodiment of a transfer apparatus in a pre-transfer position. 
           [0021]      FIG. 11B  illustrates a schematic top view of the product substrate conveyance mechanism post-transfer operation of the embodiment in  FIG. 11A . 
           [0022]      FIG. 12  illustrates a schematic view of another embodiment of a transfer apparatus in a pre-transfer position. 
           [0023]      FIG. 13  illustrates a schematic view of another embodiment of a transfer apparatus in a pre-transfer position. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    This disclosure is directed to a machine that directly transfers and affixes semiconductor device dies to a circuit and to the process for achieving the same, as well as to the circuit having dies affixed thereto (as the output product). In some instances, the machine functions to transfer unpackaged dies directly from a substrate such as a “wafer tape” to a product substrate, such as a circuit substrate. The direct transfer of unpackaged dies may significantly reduce the thickness of an end product compared to a similar product produced by conventional means, as well as the amount of time and/or cost to manufacture the product substrate. 
         [0025]    For the purpose of this description, the term “substrate” refers to any substance on which, or to which, a process or action occurs. Further, the term “product” refers to the desired output from a process or action, regardless of the state of completion. Thus, a product substrate refers to any substance on which, or to which, a process or action is caused to occur for a desired output. 
         [0026]    In an embodiment, the machine may secure a product substrate for receiving “unpackaged” dies, such as LEDs, transferred from the wafer tape, for example. In an effort to reduce the dimensions of the products using the dies, the dies are very small and thin, for example, a die may be about 50 microns thick. Due to the relatively small size of the dies, the machine includes components that function to precisely align both the wafer tape carrying the dies and the product substrate to ensure accurate placement and/or avoid product material waste. In some instances, the components that align the product substrate and the dies on the wafer tape may include a set of frames in which the wafer tape and the product substrate are secured respectively and conveyed individually to a position of alignment such that a specific die on the wafer tape is transferred to a specific spot on the product substrate. 
         [0027]    The frame that conveys the product substrate may travel in various directions, including horizontal directions and/or vertical directions, or even directions that would permit transfer to a curved surface. The frame that conveys the wafer tape may travel in various directions also. A system of gears, tracks, motors, and/or other elements may be used to secure and convey the frames carrying the product substrate and the wafer tape respectively to align the product substrate with the wafer tape in order to place a die on the correct position of the product substrate. Each frame system may also be moved to an extraction position in order to facilitate extraction of the wafer tape and the product substrate upon completion of the transfer process. 
         [0028]    In some instances, the machine may further include a transfer mechanism for transferring the dies directly from the wafer tape to the product substrate without “packaging” the dies. The transfer mechanism may be disposed vertically above the wafer tape so as to press down on the dies via the wafer tape toward the product substrate. This process of pressing down on the dies may cause the dies to peel off of the wafer tape, starting at the sides of the dies until the dies separate from the wafer tape to be attached to the product substrate. That is, by reducing the adhesion force between the die and the wafer tape, and increasing the adhesion force between the die and the product substrate, the die may be transferred. 
         [0029]    In some embodiments, the transfer mechanism may include an elongated rod, such as a pin or needle that may be cyclically actuated against the wafer tape to push the wafer tape from a top side. The needle may be sized so as to be no wider than a width of the die being transferred. Although in other instances, the width of the needle may wider, or any other dimension. When the end of the needle contacts the wafer tape, the wafer tape may experience a local deflection at the area between the die and the wafer tape. Inasmuch as the deflection is highly localized and rapidly performed, the portion of the wafer tape that does not receive pressure from the needle may begin to flex away from the surface of the die. This partial separation may thus cause the die to lose sufficient contact with the wafer tape, so as to be released from the wafer tape. Moreover, in some instances, the deflection of the wafer tape may be so minimal, as to maintain an entirety of the surface area of the die in contact with the wafer tape, while still causing the opposing surface of the die to extend beyond a plane of extension of the corresponding surface of the adjacent dies to avoid unintentional transfer of the adjacent dies. 
         [0030]    Alternatively, or additionally, the machine may further include a fixing mechanism for affixing the separated, “unpackaged” dies to the product substrate. In some instances, the product substrate may have thereon a circuit trace to which the dies are transferred and affixed. The fixing mechanism may include a device that emits energy, such as a laser, to melt/soften the material of the circuit trace on the product substrate. Moreover, in some instances, the laser may be used to activate/harden the material of the circuit trace. Thus, the fixing mechanism may be actuated before, and/or after the die is in contact with the material of the circuit trace. Accordingly, upon actuation of the transfer mechanism to release a die onto the product substrate, the energy emitting device may also be activated so as to prepare the trace material to receive the die. The activation of the energy emitting device may further enhance the release and capture of the die from the wafer tape so as to begin formation of a semiconductor product on the product substrate. 
       First Example Embodiment of a Direct Transfer Apparatus 
       [0031]      FIG. 1  illustrates an embodiment of an apparatus  100  that may be used to directly transfer unpackaged semiconductor components (or “dies”) from a wafer tape to a product substrate. The wafer tape may also be referred to herein as the semiconductor device die substrate, or simply a die substrate. The apparatus  100  may include a product substrate conveyance mechanism  102  and a wafer tape conveyance mechanism  104 . Each of the product substrate conveyance mechanism  102  and the wafer tape conveyance mechanism  104  may include a frame system or other means to secure the respective substrates to be conveyed to desired alignment positions with respect to each other. The apparatus  100  may further include a transfer mechanism  106 , which, as shown, may be disposed vertically above the wafer tape conveyance mechanism  104 . In some instances, the transfer mechanism  106  may be located so as to nearly contact the wafer substrate. Additionally, the apparatus  100  may include a fixing mechanism  108 . The fixing mechanism  108  may be disposed vertically beneath the product substrate conveyance mechanism  102  in alignment with the transfer mechanism  106  at a transfer position, where a die may be placed on the product substrate. As discussed below,  FIGS. 2A and 2B  illustrate example details of the apparatus  100 . 
         [0032]    Inasmuch as  FIGS. 2A and 2B  depict different stages of the transfer operation, while referring to the same elements and features of apparatus  200 , the following discussion of specific features may refer interchangeably to either or both of  FIGS. 2A and 2B , except where explicitly indicated. In particular,  FIGS. 2A and 2B  illustrate an embodiment of an apparatus  200 , including a product substrate conveyance mechanism  202 , a wafer tape conveyance mechanism  204 , a transfer mechanism  206 , and a fixing mechanism  208 . The product substrate conveyance mechanism  202  may be disposed adjacent to the wafer tape conveyance mechanism  204 . For example, as illustrated, the product substrate conveyance mechanism  202  may extend in a substantially horizontal direction and may be disposed vertically beneath the wafer tape conveyance mechanism  204  so as to take advantage of any effect that gravity may have in the transfer process. Alternatively, the product substrate conveyance mechanism  202  may be oriented so as to extend transversely to a horizontal plane. 
         [0033]    During a transfer operation, the conveyance mechanisms  202 ,  204  may be positioned such that a space between a surface of a product substrate carried by the product substrate conveyance mechanism  202  and a surface of a wafer tape carried by the wafer tape conveyance mechanism  204  may be more or less than 1 mm, depending on various other aspects of the apparatus  200 , including the amount of deflection that occurs by components during the transfer operation, as described herein below. In some instances, the respective opposing surfaces of the wafer tape and the product substrate may be the most prominent structures in comparison to the supporting structures of the conveyance mechanisms  202 ,  204 . That is, in order to avoid a collision between components of the machine and products thereon, which might be caused by movable parts (e.g., the conveyance mechanisms  202 ,  204 ), a distance between the respective surfaces of the wafer tape and product substrate may be less than a distance between either of the surfaces and any other opposing structural component. 
         [0034]    As depicted, and in some instances, the transfer mechanism  206  may be disposed vertically above the wafer tape conveyance mechanism  204 , and the fixing mechanism  208  may be disposed vertically beneath the product substrate conveyance mechanism  202 . It is contemplated that in some embodiments, one or both of the transfer mechanism  206  and the fixing mechanism  208  may be oriented in different positions than the positions illustrated in  FIGS. 2A and 2B . For example, the transfer mechanism  206  may be disposed so as to extend at an acute angle with respect to a horizontal plane. In another embodiment, the fixing mechanism  208  may be oriented to emit energy during the transfer process from the same direction of actuation as the transfer mechanism  206 , or alternatively, from any orientation and position from which the fixing mechanism  208  is able to participate in the transfer process. 
         [0035]    The product substrate conveyance mechanism  202  may be used to secure a product substrate  210 . Herein, the term “product substrate” may include, but is not limited to: a wafer tape (for example, to presort the dies and create sorted die sheets for future use); a paper or polymer substrate formed as a sheet or other non-planar shape, where the polymer—translucent or otherwise—may be selected from any suitable polymers, including, but not limited to, a silicone, an acrylic, a polyester, a polycarbonate, etc.; a circuit board (such as a printed circuit board (PCB)); a string or thread circuit, which may include a pair of conductive wires or “threads” extending in parallel; and a cloth material of cotton, nylon, rayon, leather, etc. The choice of material of the product substrate may include durable materials, flexible materials, rigid materials, and other materials with which the transfer process is successful and which maintain suitability for the end use of the product substrate. The product substrate  210  may be formed solely or at least partially of conductive material such that the product substrate  210  acts as a conductive circuit for forming a product. The potential types of product substrate may further include items, such as glass bottles, vehicle windows, or sheets of glass. 
         [0036]    In an embodiment as depicted in  FIGS. 2A and 2B , the product substrate  210  may include a circuit trace  212  disposed thereon. The circuit trace  212 , as depicted, may include a pair of adjacent trace lines spaced apart by a trace spacing, or gap so as to accommodate a distance between electrical contact terminals (not shown) on the dies being transferred. Thus, the trace spacing, or gap between the adjacent trace lines of the circuit trace  212  may be sized according to the size of the die being transferred to ensure proper connectivity and subsequent activation of the die. For example, the circuit trace  212  may have a trace spacing, or gap ranging from about 75 to 200 microns, about 100 to 175 microns, or about 125 to 150 microns. 
         [0037]    The circuit trace  212  may be formed from a conductive ink disposed via screen printing, inkjet printing, laser printing, manual printing, or other printing means. Further, the circuit trace  212  may be pre-cured and semi-dry or dry to provide additional stability, while still being activatable for die conductivity purposes. A wet conductive ink may also be used to form the circuit trace  212 , or a combination of wet and dry ink may be used for the circuit trace  212 . Alternatively, or additionally, the circuit trace  212  may be pre-formed as a wire trace, or photo-etched, or from molten material formed into a circuit pattern and subsequently adhered, embedded, or otherwise secured to the product substrate  210 . 
         [0038]    The material of the circuit trace  212  may include, but is not limited to, silver, copper, gold, carbon, conductive polymers, etc. In some instances, the circuit trace  212  may include a silver-coated copper particle. A thickness of the circuit trace  212  may vary depending on the type of material used, the intended function and appropriate strength or flexibility to achieve that function, the energy capacity, the size of the LED, etc. For example, a thickness of the circuit trace may range from about 5 microns to 20 microns, from about 7 microns to 15 microns, or from about 10 microns to 12 microns. 
         [0039]    Accordingly, in one non-limiting example, the product substrate  210  may be a flexible, translucent polyester sheet having a desired circuit pattern screen printed thereon using a silver-based conductive ink material to form the circuit trace  212 . 
         [0040]    The product substrate conveyance mechanism  202  may include a product substrate conveyor frame  214  for securing a product substrate holder frame  216 . The structure of the product substrate holder frame  216  may vary significantly depending on the type and properties (e.g., shape, size, elasticity, etc.) of the product substrate being used. Inasmuch as the product substrate  210  may be a flexible material, product substrate  210  may be held under tension in the product substrate holder frame  216 , so as to create a more rigid surface upon which a transfer operation, discussed herein below, is performed. In the above example, the rigidity created by the tension in the product substrate  210  may increase the placement accuracy when transferring components. 
         [0041]    In some instances, using a durable or more rigid material for the product substrate  210 , naturally provides a firm surface for component placement accuracy. In contrast, when the product substrate  210  is allowed to sag, wrinkles and/or other discontinuities may form in the product substrate  210  and interfere with the pre-set pattern of the circuit trace  212 , to the extent that the transfer operation may be unsuccessful. 
         [0042]    While the means of holding the product substrate  210  may vary greatly,  FIG. 2A  illustrates an embodiment of a product substrate holder frame  216  including a first portion  216   a  having a concave shape and a second portion  216   b  having a convex counter shape that corresponds in shape to the concave shape. In the depicted example, tension is created for the product substrate  210  by inserting an outer perimeter of the product substrate  210  between the first portion  216   a  and the second portion  216   b  to thereby clamp the product substrate  210  tightly. 
         [0043]    The product substrate conveyor frame  214  may be conveyed in at least three directions—two directions in the horizontal plane and vertically as well. The conveyance may be accomplished via a system of motors, rails, and gears (none of which are shown). As such, the product substrate tensioner frame  216  may be conveyed to and held in a specific position as directed and/or programmed and controlled by a user of the apparatus  200 . 
         [0044]    The wafer tape conveyance mechanism  204  may be implemented to secure a wafer tape  218  having dies  220  (i.e., semiconductor device dies) thereon. The wafer tape  218  may be conveyed in multiple directions to the specific transfer positions for the transfer operation via a wafer tape conveyor frame  222 . Similar to the product substrate conveyor frame  214 , the wafer tape conveyor frame  222  may include a system of motors, rails, and gears (none of which are shown). 
         [0045]    The unpackaged semiconductor dies  220  for transfer may be extremely small. Indeed, the height of the dies  220  may range from 12.5 to 200 microns, or from 25 to 100 microns, or from 50 to 80 microns. 
         [0046]    Due to the micro size of the dies, when the wafer tape  218  has been conveyed to the appropriate transfer position, a gap spacing between the wafer tape  218  and the product substrate  210  may range from about 0.25 mm to 1.50 mm, or about 0.50 mm to 1.25 mm, or about 0.75 mm to 1.00 mm, for example. A minimum gap spacing may depend on factors including: a thickness of the die being transferred, a stiffness of the wafer tape involved, an amount of deflection of the wafer tape needed to provide adequate capture and release of the die, a proximity of the adjacent dies, etc. As the distance between the wafer tape  218  and the product substrate  210  decreases, a speed of the transfer operation may also decrease due to the reduced cycle time (discussed further herein) of the transfer operation. Such a decrease in the duration of a transfer operation may therefore increase a rate of die transfers. For example, the die transfer rate may range from about 6-20 dies placed per second. 
         [0047]    Furthermore, the wafer tape conveyor frame  222  may secure a wafer tape holder frame  224 , which may stretch and hold the wafer tape  218  under tension. As illustrated in  FIG. 2A , the wafer tape  218  may be secured in the wafer tape holder frame  224  via clamping a perimeter of the wafer tape  218  between adjacent components of the wafer holder frame  224 . Such clamping assists in maintaining the tension and stretched characteristic of the wafer tape  218 , thereby increasing the success rate of the transfer operation. In view of the varying properties of different types/brands/qualities of wafer tapes available, a particular wafer tape may be selected for use based on an ability to consistently remain at a desired tension during a transfer process. In some instances, the needle actuation performance profile (discussed further herein below) may change depending on the tension of the wafer tape  218 . 
         [0048]    The material used for the wafer tape  218  may include a material having elastic properties, such as a rubber or silicone, for example. Furthermore, inasmuch as temperature of the environment and the wafer tape  218  itself may contribute to potential damage to the wafer tape  218  during the transfer process, a material having properties that are resistant to temperature fluctuation may be advantageous. Additionally, in some instances, the wafer tape  218  may be stretched slightly so as to create a separation or gap between individual dies  220  to assist in the transfer operation. A surface of the wafer tape  218  may include a sticky substance via which the dies  220  may be removably adhered to the wafer tape  218 . 
         [0049]    The dies  220  on the wafer tape  218  may include dies that were individually cut from a solid semiconductor wafer and then placed onto the wafer tape  218  to secure the dies. In such a situation, the dies may have been pre-sorted and explicitly organized on the wafer tape  218 , in order, for example, to assist in the transfer operation. In particular, the dies  220  may be arranged sequentially as to the expected order of transfer to the product substrate  210 . Such pre-arrangement of the dies  220  on the wafer tape  218  may reduce the amount of travel that would otherwise occur between the product substrate conveyance mechanism  202  and the wafer tape conveyance mechanism  204 . Additionally, or alternatively, the dies on the wafer tape  218  may have been pre-sorted to include only dies having substantially equivalent performance properties. In this case, efficiency of the supply chain may be increased and thus, travel time of the wafer tape conveyance mechanism  204  may be reduced to a minimum. 
         [0050]    In some instances, materials used for the dies may include, but is not limited to, silicon carbide, gallium nitride, a coated silicon oxide, etc. Furthermore, sapphire or silicon may be used as a die as well. Additionally, as indicated above, a “die” may be representative herein of an electrically actuatable element generally. 
         [0051]    In some embodiments, the wafer tape  218  may include dies that are not pre-sorted, but rather are formed by simply cutting a semiconductor directly on wafer tape, and then leaving the dies on the wafer tape without “picking and placing” to sort the dies depending on the respective performance quality of the dies. In such a situation, the dies on the wafer tape may be mapped to describe the exact relative locations of the different quality dies. Therefore, in some instances, it may be unnecessary to use wafer tape having pre-sorted dies. In such a case, the amount of time and travel for the wafer tape conveyance mechanism  204  to move between particular dies for each sequential transfer operation may increase. This may be caused in part by the varying quality of the dies dispersed within the area of the semiconductor, which means that a die of a specific quality for the next transfer operation may not be immediately adjacent to the previously transferred die. Thus, the wafer tape conveyance mechanism  204  may move the wafer tape  218  further to align an appropriate die of a specific quality for transfer than would be necessary for a wafer tape  218  containing dies of substantially equivalent quality. 
         [0052]    In further regard to the dies  220  on the wafer tape  218 , in some instances, a data map of the dies  220  may be provided with the wafer tape  218 . The data map may include a digital file providing information that describes the specific quality and location of each die on the wafer tape  218 . The data map file may be input into a processing system in communication with the apparatus  200 , whereby the apparatus  200  may be controlled/programmed to seek the correct die  220  on the wafer tape  218  for transfer to the product substrate  210 . 
         [0053]    A transfer operation is performed, in part, via the transfer mechanism  206 , which is a die separation device for assisting in separation of dies from the wafer tape  218 . The actuation of the transfer mechanism  206  may cause one or more dies  220  to be released from the wafer tape  218  and to be captured by the product substrate  210 . In some instances, the transfer mechanism  206  may operate by pressing an elongated rod, such as a pin or a needle  226  into a top surface of the wafer tape  218  against a die  220 . The needle  226  may be connected to a needle actuator  228 . The needle actuator  228  may include a motor connected to the needle  226  to drive the needle  226  toward the wafer tape  218  at predetermined/programmed times. 
         [0054]    In view of the function of the needle  226 , the needle  226  may include a material that is sufficiently durable to withstand repetitive, rapid, minor impacts while minimizing potential harm to the dies  220  upon impact. For example, the needle  226  may include a metal, a ceramic, a plastic, etc. Additionally, a tip of the needle  226  may have a particular shape profile, which may affect the ability of the needle to function repetitively without frequently breaking either the tip or damaging the wafer tape  218  or the dies  220 . The profile shape of the tip of the needle is discussed in greater detail below with respect to  FIG. 3 . 
         [0055]    In a transfer operation, the needle  226  may be aligned with a die  220 , as depicted in  FIG. 2A , and the needle actuator may move the needle  226  to push against an adjacent side of the wafer tape  218  at a position in which the die  220  is aligned on the opposing side of the wafer tape  218 , as depicted in  FIG. 2B . The pressure from the needle  226  may cause the wafer tape  218  to deflect so as to extend the die  220  to a position closer to the product substrate  226  than adjacent dies  220 , which are not being transferred. As indicated above, the amount of deflection may vary depending several factors, such as the thickness of the die and circuit trace. For example, where a die  220  is about 50 microns thick and circuit trace  212  is about 10 microns thick, an amount of deflection of the wafer tape  218  may be about 75 microns. Thus, the die  220  may be pressed via the needle  226  toward the product substrate  210  to the extent that the electrical contact terminals (not shown) of the die are able to bond with the circuit trace  212 , at which point, the transfer operation proceeds to completion and the die  220  is released from the wafer tape  218 . 
         [0056]    To the extent that the transfer process may include a rapidly repeated set of steps including a cyclical actuation of the needle  226  pressing upon a die  220 , a method of the process is described in detail herein below with respect to  FIG. 8 . Further, the stroke profile of the actuation of the needle  226  (within the context of the transfer process) is discussed in more detail hereafter with respect to  FIG. 4 . 
         [0057]    Turning back to  FIGS. 2A and 2B , in some instances, the transfer mechanism  206  may further include a needle retraction support  230 , (also known as a pepper pot). In an embodiment, the support  230  may include a structure having a hollowed space wherein the needle  226  may be accommodated by passing into the space via an opening  232  in a first end of the support  230 . The support  230  may further include at least one opening  234  on a second opposing end of the support  230 . Moreover, the support may include multiple perforations near opening  234 . The at least one opening  234  may be sized with respect to a diameter of the needle  226  to accommodate passage of the needle  226  therethrough so as to press on the wafer tape  218  during the transfer process. 
         [0058]    Additionally, in some instances, the support  230  may be disposed adjacent to the upper surface of the wafer tape  218 . As such, when the needle  226  is retracted from pressing on the wafer tape  218  during a transfer operation, a base surface of the support  230  (having the at least one opening  234  therein) may come into contact with the upper surface of the wafer tape  218 , thereby preventing upward deflection of the wafer tape  218 . This upward deflection may be caused in the event where the needle  226  pierces at least partially into the wafer tape  218 , and while retracting, the wafer tape is stuck to the tip of the needle  226 . Thus, the support  230  may reduce the time it takes to move to the next die  220 . A wall perimeter shape of the support  230  may be cylindrical or any other shape that may be accommodated in the apparatus  200 . Accordingly, the support  230  may be disposed between the needle  226  and an upper surface of the wafer tape  218 . 
         [0059]    With respect to the effect of temperature on the integrity of the wafer tape  218 , it is contemplated that a temperature of support  230  may be adjusted so as to regulate the temperature of the needle  226  and the wafer tape  218 , at least near the point of the transfer operation. Accordingly, the temperature of the support  230  may be heated or cooled, and a material of the support  230  may be selected to maximize thermal conductivity. For example, the support  230  may be formed of aluminum, or another relatively high thermal conductivity metal or comparable material, whereby the temperature may be regulated to maintain consistent results of the transfer operations. In some instances, air may be circulated within the support  230  to assist in regulating the temperature of a local portion of the wafer tape  218 . Additionally, or alternatively, a fiber optic cable  230   a  may be inserted into the needle retraction support  230 , and may further be against the needle  226  to assist in temperature regulation of the wafer tape  218  and/or the needle  226 . 
         [0060]    As indicated above, fixing mechanism  208  may assist in affixing the die  220  to the circuit trace  212  on a surface of the product substrate  210 .  FIG. 2B  illustrates the apparatus  200  in a transfer stage, where the die  220  is pushed against the circuit trace  212 . In an embodiment, fixing mechanism  208  may include an energy-emitting device  236  including, but not limited to, a laser, electromagnetic radiation, pressure vibration, ultrasonic welding, etc. In some instances, the use of pressure vibration for the energy-emitting device  236  may function by emitting a vibratory energy force so as to cause disruption of the molecules within the circuit trace against those of the electrical contact terminals so as to form a bond via the vibratory pressure. 
         [0061]    In a non-limiting example, as depicted in  FIG. 2B , a laser may be implemented as the energy-emitting device  236 . During a transfer operation, laser  236  may be activated to emit a specific wavelength and intensity of light energy directed at the die  220  being transferred. The wavelength of the light of the laser  236  may be selected specifically based on the absorption of that wavelength of light with respect to the material of the circuit trace  212  without significantly affecting the material of the product substrate  210 . For example, a laser having an operational wavelength of 808 nm, and operating at 5 W may be readily absorbed by silver, but not by polyester. As such, the laser beam may pass through the substrate of polyester and affect the silver of a circuit trace. Alternatively, the wavelength of laser may match the absorption of the circuit trace and the material of the substrate. The focus area of the laser  236  (indicated by the dashed lines emanating vertically from the laser  236  in  FIG. 2B  toward the product substrate  210 ) may be sized according to the size of the LED, such as for example, a 300 micron wide area. 
         [0062]    Upon actuation of a predetermined controlled pulse duration of the laser  236 , the circuit trace  212  may begin to cure (and/or melt or soften) to an extent that a fusing bond may form between the material of the circuit trace  212  and the electrical contact terminals (not shown) on the die  220 . This bond further assists in separating the unpackaged die  220  from the wafer tape  218 , as well as simultaneously affixing the die  220  to the product substrate  210 . Additionally, the laser  236  may cause some heat transfer on the wafer tape  218 , thereby reducing adhesion of the die  220  to the wafer tape  218  and thus assisting in the transfer operation. 
         [0063]    In other instances, dies may be released and fixed to the product substrates in many ways, including using a laser having a predetermined wavelength or a focused light (e.g., IR, UV, broadband/multispectral) for heating/activating circuit traces to thereby cure an epoxy or phase change bond materials, or for deactivating/releasing a die from wafer tape, or for initiating some combination of reactions. Additionally, or alternatively, a specific wavelength laser or light may be used to pass through one layer of the system and interact with another layer. Furthermore, a vacuum may be implemented to pull a die from the wafer tape, and air pressure may be implemented to push the die onto a product substrate, potentially including a rotary head between the die wafer substrate and the product substrate. In yet another instance, ultrasonic vibration may be combined with pressure to cause the die to bond to the circuit traces. 
         [0064]    Similar to the needle retraction support  230 , the fixing mechanism may also include a product substrate support  238 , which may be disposed between the laser  236  and the bottom surface of the product substrate  210 . The support  238  may include an opening  240  at a base end thereof and an opening  242  at an upper end thereof. For example, the support  238  may be formed as a ring or hollow cylinder. The support may further include structure to secure a lens (not shown) to assist in directing the laser. The laser  236  emits the light through the openings  240 ,  242  to reach the product substrate  210 . Furthermore, the upper end of the sidewalls of the support  238  may be disposed in direct contact with or closely adjacent to the bottom surface of the product substrate  210 . Positioned as such, the support  238  may help to prevent damage from occurring to the product substrate  210  during the stroke of the needle  226  at the time of a transfer operation. In some instances, during the transfer operation, the portion of the bottom surface of the product substrate  210  that is aligned with the support  238  may contact the support  238 , which thereby provides resistance against the incoming motion of the die  220  being pressed by the needle  226 . Moreover, the support  238  may be movable in a direction of the vertical axis to be able to adjust a height thereof so as to raise and lower support  238  as necessary, including to a height of the product substrate  210 . 
         [0065]    In addition to the above features, apparatus  200  may further include a first sensor  244 , from which apparatus  200  receives information regarding the dies  220  on the wafer tape  218 . In order to determine which die is to be used in the transfer operation, the wafer tape  218  may have a bar code (not shown) or other identifier, which is read or otherwise detected. The identifier may provide die map data to the apparatus  200  via the first sensor  244 . 
         [0066]    As shown in  FIGS. 2A and 2B , the first sensor  244  may be positioned near the transfer mechanism  206  (or the needle  226  specifically), spaced apart from the transfer mechanism  206  by a distance d, which may range from about 1-5 inches, so as to enhance the accuracy of location detection. In an alternative embodiment, first sensor  244  may be disposed adjacent the tip of the needle  226  in order to sense the exact position of the dies  220  in real time. During the transfer process, the wafer tape  218  may be punctured and or further stretched over time, which may alter the previously mapped, and thus expected, locations of the dies  220  on the wafer tape  218 . As such, small changes in the stretching of the wafer tape  218  could add up to significant errors in alignment of the dies  220  being transferred. Thus, real time sensing may be implemented to assist in accurate die location. 
         [0067]    In some instances, the first sensor  244  may be able to identify the precise location and type of die  220  that is being sensed. This information may be used to provide instructions to the wafer tape conveyor frame  222  indicating the exact location to which the wafer tape  218  should be conveyed in order to perform the transfer operation. Sensor  244  may be one of many types of sensors, or a combination of sensor types to better perform multiple functions. Sensor  244  may include, but is not limited to: a laser range finder, or an optical sensor, such as a non-limiting example of a high-definition optical camera having micro photography capabilities. 
         [0068]    Moreover, in some instances, a second sensor  246  may also be included in apparatus  200 . The second sensor  246  may be disposed with respect to the product substrate  210  so as to detect the precise position of the circuit trace  212  on the product substrate  210 . This information may then be used to determine any positional adjustment needed to align the product substrate  210  between the transfer mechanism  206  and the fixing mechanism  208  so that the next transfer operation occurs in the correct location on the circuit trace  212 . This information may further be relayed to the apparatus  200  to coordinate conveying the product substrate  210  to a correct position, while simultaneously conveying instructions to the wafer tape conveyor frame  222 . A variety of sensors are also contemplated for sensor  246  including optical sensors, such as one non-limiting example of a high-definition optical camera having micro photography capabilities. 
         [0069]      FIGS. 2A and 2B  further illustrate that the first sensor  244 , the second sensor  246 , and the laser  236  may be grounded. In some instances, the first sensor  244 , the second sensor  246 , and the laser  236  may all be grounded to the same ground (G), or alternatively, to a different ground (G). 
         [0070]    Depending on the type of sensor used for the first and second sensors  244 ,  246 , the first or second sensors may further be able to test the functionality of transferred dies. Alternatively, an additional tester sensor (not shown) may be incorporated into the structure of apparatus  200  to test individual dies before removing the product substrate  210  from the apparatus  200 . 
         [0071]    Furthermore, in some examples, multiple independently-actuatable needles and/or lasers may be implemented in a machine in order to transfer and fix multiple dies at a given time. The multiple needles and/or lasers may be independently movable within a three-dimensional space. Multiple die transfers may be done synchronously (multiple needles going down at the same time), or concurrently but not necessarily synchronously (e.g., one needle going down while the other is going up, which arrangement may balance better the components and minimize vibration). Control of the multiple needles and/or lasers may be coordinated to avoid collisions between the plurality of components. Moreover, in other examples, the multiple needles and/or lasers may be arranged in fixed positions relative to each other. 
       Example Needle Tip Profile 
       [0072]    As mentioned above, a profile shape of the tip  300  of a needle is discussed with respect to  FIG. 3 , which shows a schematic example profile shape of the tip  300 . In an embodiment, the tip  300  may be defined as the end of the needle, including sidewalls  302  adjoining tapered portion  304 , corner  306 , and base end  308 , which may extend transversely to the opposing side of the needle. The specific size and shape of the tip  300  may vary according to factors of the transfer process such as, for example, the size of the die  220  being transferred and the speed and the impact force, of a transfer operation. For example, the angle θ seen in  FIG. 3 , as measured between a longitudinal direction of the central axis of the needle and the tapered portion  304  may range from about 10 to 15°; the radius r of the corner  306  may range from about 15 to 50+ microns; the width w of the base end  308  may range from about 0 to 100+ microns (μm), where w may be less than or equal to the width of the die  220  being transferred; the height h of the tapered portion  304  may range from about 1 to 2 mm, where h may be greater than a distance traveled by needle during a stroke of a transfer operation; and the diameter d of the needle  226  may be approximately 1 mm. 
         [0073]    Other needle tip profiles are contemplated and may have different advantages depending on various factors associated with the transfer operation. For example, the needle tip  300  may be more blunt to mirror the width of the die or more pointed so as to press in a smaller area of the wafer tape. 
       Example Needle Actuation Performance Profile 
       [0074]    Illustrated in  FIG. 4  is an embodiment of a needle actuation performance profile. That is,  FIG. 4  depicts an example of the stroke pattern performed during a transfer operation by displaying the height of the needle tip with respect to the plane of the wafer tape  218  as it varies with time. As such, the “0” position in  FIG. 4  may be the upper surface of the wafer tape  218 . Further, inasmuch as the idle time of the needle and the ready time of the needle may vary depending on the programmed process or the varying duration of time between transferring a first die and the time it takes to reach a second die for transfer, the dashed lines shown at the idle and ready phases of the stroke pattern indicate that the time is approximate, but may be longer or shorter in duration. Moreover, it is to be understood that the solid lines shown for use of the laser are example times for an embodiment illustrated herewith, however, the actual duration of laser on and off time may vary depending on the materials used in forming the circuit (such as the material choice of the circuit trace), the type of product substrate, the desired effect (pre-melting circuit trace, partial bond, complete bond, etc.), the distance of the laser from the bond point (i.e., the upper surface of the product substrate), the size of the die being transferred, and the power/intensity/wavelength of the laser, etc. Accordingly, the following description of the profile shown in  FIG. 4  may be an example embodiment of a needle profile. 
         [0075]    In some instances, prior to a transfer operation, a fully retracted needle tip may be idle at approximately 2000 μm above the surface of the wafer tape. After a varying amount of time, the needle tip may descend rapidly to rest in the ready state at approximately 750 μm above the surface of the wafer tape. After another undetermined amount of time at the ready state, the needle tip may descend again to contact the die and press the wafer tape with the die down to a height of approximately −1000 μm, where at the die may be transferred to the product substrate. The dotted vertical line at the start of the laser on section indicates that the laser may come on at some point between the beginning of the descent from the ready phase and the bottom of the stroke of the needle tip. For example, the laser may turn on at approximately 50% of the way through the descent. In some instances, by turning the laser on early, for example before the needle begins to descend, the circuit trace may begin to soften prior to contact with the die so as to form a stronger bond, or additionally, the die wafer may be affected or prepared during this time. The phase in which the laser turns on may last approximately 20 ms (“milliseconds”). At the bottom of the stroke, where the laser is on, that phase may be a bonding phase between the die and the product substrate. This bonding phase may allow the circuit trace to attach to the die contacts, which stiffens quickly after the laser is turned off. As such, the die may be bonded to the product substrate. The bonding phase may last approximately 30 ms. Thereafter, the laser may be turned off and the needle may ascend to the ready phase rapidly. Conversely, the laser may be turned off before the needle begins to ascend, or at some point during the ascent of the needle tip back to the ready phase, the laser may be turned off. After the ascent of the needle tip to the ready phase, the height of the needle tip may overshoot and bounce back under the height of the ready phase somewhat buoyantly. While some of the buoyancy may be attributed to the speed at which the needle tip ascends to the ready phase, the speed and the buoyancy may be intentional in order to assist in retracting a tip of the needle from a surface of the wafer tape in the case where the needle has pierced the wafer tape and may be stuck therein. 
         [0076]    As depicted in  FIG. 4 , the timing in which the laser is turned off may be longer than the timing in which the laser is turned on, where a slower speed of the descent may assist in preventing damage to the die, and as mentioned above, the rapid rate of ascent may assist in extracting the needle tip from the wafer tape more effectively. Nevertheless, as previously stated, the timing shown on  FIG. 4  is approximate, particularly with respect to the idle and ready periods. Therefore, the numerical values assigned along the bottom edge of the  FIG. 4  are for reference and should not be taken literally, except when otherwise stated. 
       Example Product Substrate 
       [0077]      FIG. 5  illustrates an example embodiment of a processed product substrate  500 . A product substrate  502  may include a first portion of a circuit trace  504 A, which may perform as a negative or positive power terminal when power is applied thereto. A second portion of the circuit trace  504 B may extend adjacent to the first portion of the circuit trace  504 A, and may act as a corresponding positive or negative power terminal when power is applied thereto. 
         [0078]    As similarly described above with respect to the wafer tape, in order to determine where to convey the product substrate  502  to perform the transfer operation, the product substrate  502  may have a bar code (not shown) or other identifier, which is read or otherwise detected. The identifier may provide circuit trace data to the apparatus. The product substrate  502  may further include datum points  506 . Datum points  506  may be visual indicators for sensing by the product substrate sensor (for example, second sensor  246  in  FIG. 2 ) to locate the first and second portions of the circuit trace  504 A,  504 B. Once the datum points  506  are sensed, a shape and relative position of the first and second portions of the circuit trace  504 A,  504 B with respect to the datum points  506  may be determined based on preprogrammed information. Using the sensed information in connection with the preprogrammed information, the product substrate conveyance mechanism may convey the product substrate  502  to the proper alignment position for the transfer operation. 
         [0079]    Additionally, dies  508  are depicted in  FIG. 5  as straddling between the first and second portions of the circuit trace  504 A,  504 B. In this manner, the electrical contact terminals (not shown) of the dies  508  may be bonded to the product substrate  502  during a transfer operation. Accordingly, power may be applied to run between the first and second portions of the circuit trace  504 A,  504 B, and thereby powering dies  508 . For example, the dies may be unpackaged LEDs that were directly transferred from a wafer tape to the circuit trace on the product substrate  502 . Thereafter, the product substrate  502  may be processed for completion of the product substrate  502  and used in a circuit or other final product. Further, other components of a circuit may be added by the same or other means of transfer to create a complete circuit, and may include control logic to control LEDs as one or more groups in some static or programmable or adaptable fashion. 
       Simplified Example Direct Transfer System 
       [0080]    A simplified example of an embodiment of a direct transfer system  600  is illustrated in  FIG. 6 . The transfer system  600  may include a personal computer (PC)  602  (or server, data input device, user interface, etc.), a data store  604 , a wafer tape mechanism  606 , a product substrate mechanism  608 , a transfer mechanism  610 , and a fixing mechanism  612 . Inasmuch as a more detailed description of the wafer tape mechanism  606 , the product substrate mechanism  608 , the transfer mechanism  610 , and the fixing mechanism  612  has been given heretofore, specific details about these mechanisms is not repeated here. However, a brief description of how the wafer tape mechanism  606 , the product substrate mechanism  608 , the transfer mechanism  610 , and the fixing mechanism  612  relate to interactions between the PC  602  and the data store  604  is described hereafter. 
         [0081]    In some instances, the PC  602  communicates with data store  604  to receive information and data useful in the transfer process of directly transferring dies from a wafer tape in wafer tape mechanism  606  using the transfer mechanism  610  on to a product substrate in the product substrate mechanism  608  whereat the dies may be fixed upon the product substrate via actuation of a laser or other energy-emitting device located in the fixing mechanism  612 . PC  602  may also serve as a receiver, compiler, organizer, and controller of data being relayed to and from each of the wafer tape mechanism  606 , the product substrate mechanism  608 , the transfer mechanism  610 , and the fixing mechanism  612 . PC  602  may further receive directed information from a user of the transfer system  600 . 
         [0082]    Note that, while  FIG. 6  depicts directional movement capability arrows adjacent to the wafer tape mechanism  606  and the product substrate mechanism  608 , those arrows merely indicate general directions for mobility, however, it is contemplated that both the wafer tape mechanism  606  and the product substrate mechanism  608  may also be able to move in other directions including rotation in plane, pitch, roll, and yaw, for example. 
         [0083]    Additional details of the interaction of the components of the transfer system  600  are described with respect to  FIG. 7  below. 
       Detailed Example Direct Transfer System 
       [0084]    A schematic of the communication pathways between the respective elements of a transfer system  700  may be described as follows. 
         [0085]    The direct transfer system may include a personal computer (PC)  702  (or server, data input device, user interface, etc.), which may receive communication from, and provide communication to a data store  704 . The PC  702  may further communicate with a first cell manager  706  (illustrated as “Cell Manager  1 ”) and a second cell manager  708  (illustrated as “Cell Manager  2 ”). Therefore, the PC  702  may control and synchronize the instructions between the first cell manager  706  and the second cell manager  708 . 
         [0086]    PC  702  may include processors and memory components with which instructions may be executed to perform various functions with respect to the first and second cell managers  706 ,  708 , as well as data store  704 . In some instances, PC  702  may include a project manager  710  and a needle profile definer  712 . 
         [0087]    Project manager  710  may receive input from the first and second cell managers  706 ,  708  and data store  704  to organize the direct transfer process and maintain smooth functioning with respect to orientation and alignment of the product substrate with respect to the wafer tape and the dies thereon. 
         [0088]    Needle profile definer  712  may contain data regarding the needle stroke performance profile, which may be used to instruct the transfer mechanism regarding the desired needle stroke performance according to the specific dies on the loaded wafer tape and the pattern of the circuit trace on the product substrate. Additional details of the needle profile definer  712  are discussed further herein below. 
         [0089]    Turning back to data store  704 , data store  704  may include memory containing data such as a die map  714 , which may be specific to the wafer tape loaded in the wafer tape mechanism. As explained previously, a die map may describe the relative locations of each die on the wafer tape and the quality thereof for the purpose of providing a pre-organized description of the location of specific dies. Further, data store  704  may also include memory containing circuit CAD files  716 . Circuit CAD files  716  may contain data regarding a specific circuit trace pattern on the loaded product substrate. 
         [0090]    Project manager  710  may receive the die map  714  and circuit CAD files  716  from the data store  704 , and may relay the respective information to the first and second cell managers  706 ,  708 , respectively. 
         [0091]    In an embodiment, the first cell manager  706  may use the die map  714  from data store  704  via a die manager  718 . More specifically, die manager  718  may compare die map  714  with the information received by a sensor manager  720 , and based thereon, may provide instructions to a motion manager  722  regarding the location of a particular die. Sensor manager  720  may receive data regarding the actual location of dies on the wafer tape from a die detector  724 . Sensor manager  720  may also instruct the die detector  724  to look for a particular die in a particular location according to die map  714 . The die detector  724  may include a sensor such as the second sensor  244  in  FIGS. 2A and 2B . Based on the received data of the actual location (either a confirmation or an update regarding a shift in position) of the dies on the wafer tape, the motion manager  722  may instruct a first robot  726  (illustrated as “Robot  1 ”) to convey the wafer tape to an alignment position with the needle of the transfer mechanism. 
         [0092]    Upon reaching the instructed location, the first robot  726  may communicate the completion of its movement to a needle controlboard manager  728 . Additionally, the needle control board manager  728  may directly communicate with the PC  702  to coordinate the execution of the transfer operation. At the time of the execution of the transfer operation, the PC  702  may instruct the needle control board manager  728  to activate the needle actuator/needle  730 , thereby causing the needle to perform a stroke in accordance with the loaded needle profile in the needle profile definer  712 . The needle controlboard manager  728  may also activate the laser control/laser  732 , thereby causing the laser to emit a beam toward the product substrate as the needle presses down a die via the wafer tape to execute the transfer operation. As indicated above, the activation of the laser control/laser  732  may occur prior to, simultaneously, during, or after activation, or even a complete actuation, of the needle stroke. 
         [0093]    Accordingly, the first cell manager  706  may pass through a plurality of states including: determining where to tell the first robot  726  to go; telling the first robot  726  to go to the determined location; turning on the needle; activating the fixing device; and resetting. 
         [0094]    Prior to execution of the transfer operation, the project manager  710  may relay the data of the circuit CAD files  716  to the second cell manager  708 . The second cell manager  708  may include a sensor manager  734  and a motion manager  736 . Using the circuit CAD files  716 , the sensor manager  734  may instruct the substrate alignment sensor  738  to find the datum points on the product substrate and thereby detect and orient the product substrate according to the location of the circuit trace thereon. The sensor manager  734  may receive confirmation or updated location information of the circuit trace pattern on the product substrate. The sensor manager  734  may coordinate with the motion manager  736  to provide instructions to a second robot  740  (illustrated as “Robot  2 ”) to convey the product substrate to an alignment position (i.e., a transfer fixing position) for execution of the transfer operation. Thus, the circuit CAD files  716  may assist the project manager  710  in aligning the product substrate with respect to the wafer tape such that the dies may be accurately transferred to the circuit trace thereon. 
         [0095]    Accordingly, the second cell manager  708  may pass through a plurality of states including: determining where to tell the second robot  740  to go; telling the second robot  740  to go to the determined location; and resetting. 
         [0096]    It is understood that additional and alternative communication pathways between all or fewer than all of the various components of the direct transfer system  700  described above are possible. 
       Example Direct Transfer Method 
       [0097]    A method  800  of executing a direct transfer process, in which one or more dies is directly transferred from a wafer tape to a product substrate, is illustrated in  FIG. 8 . The steps of the method  800  described herein may not be in any particular order and as such may be executed in any satisfactory order to achieve a desired product state. The method  800  may include a step of loading transfer process data into a PC and/or a data store  802 . The transfer process data may include data such as die map data, circuit CAD files data, and needle profile data. 
         [0098]    A step of loading a wafer tape into a wafer tape conveyor mechanism  804  may also be included in method  800 . Loading the wafer tape into the wafer tape conveyor mechanism may include controlling the wafer tape conveyor mechanism to move to a load position, which is also known as an extract position. The wafer tape may be secured in the wafer tape conveyor mechanism in the load position. The wafer tape may be loaded so that the dies of the semiconductor are facing downward toward the product substrate conveyor mechanism. 
         [0099]    The method  800  may further include a step of preparing the product substrate to load into the product substrate conveyor mechanism  806 . Preparing the product substrate may include a step of screen printing a circuit trace on the product substrate according to the pattern of the CAD files being loaded into the PC or data store. Additionally, datum points may be printed onto the circuit substrate in order to assist in the transfer process. The product substrate conveyor mechanism may be controlled to move to a load position, which is also known as an extraction position, whereat the product substrate may be loaded into the product substrate conveyor mechanism. The product substrate may be loaded so that the circuit trace faces toward the dies on the wafer. In some instances, for example, the product substrate may be delivered and placed in the load position by a conveyor (not shown) or other automated mechanism, such as in the style of an assembly line. Alternatively, the product substrate may be manually loaded by an operator. 
         [0100]    Once the product substrate is properly loaded into the product substrate conveyor mechanism in the wafer tape is properly loaded into the wafer tape conveyor mechanism, a program to control the direct transfer of the dies from the wafer tape to the circuit trace of the product substrate may be executed via the PC to commence the direct transfer operation  808 . The details of the direct transfer operation are described below. 
       Example Direct Transfer Operation Method 
       [0101]    A method  900  of the direct transfer operation of causing dies to be transferred directly from the wafer tape (or other substrate holding dies, also called a “die substrate” for simplified description of  FIG. 9 ) to the product substrate is illustrated in  FIG. 9 . The steps of the method  900  described herein may not be in any particular order and as such may be executed in any satisfactory order to achieve a desired product state. 
         [0102]    In order to determine which dies to place on the product substrate and where to place the dies on the product substrate, the PC may receive input regarding the identification of the product substrate and the identification of the die substrate containing the dies to be transferred  902 . This input may be entered manually by a user, or the PC may send a request to the cell managers in control, respectively, of the product substrate alignment sensor and the die detector. The request may instruct the sensor to scan the loaded substrate for an identification marker, such as a barcode or QR code; and/or the request may instruct the detector to scan the loaded die substrate for an identification marker, such as a barcode or QR code. 
         [0103]    Using the product substrate identification input, the PC may query the data store or other memory to match the respective identification markers of the product substrate and the die substrate and retrieve the associated data files  904 . In particular, the PC may retrieve a circuit CAD file associated with the product substrate that describes the pattern of the circuit trace on the product substrate. The circuit CAD file may further contain data such as the number of, relative positions of, and respective quality requirement of, the dies to be transferred to the circuit trace. Likewise, the PC may retrieve a die map data file associated with the die substrate that provides a map of the relative locations of the specific dies on the die substrate. 
         [0104]    In the process of executing a transfer of a die to the product substrate, the PC may determine the initial orientation of the product substrate and the die substrate relative to the transfer mechanism and the fixing mechanism  906 . Within step  906 , the PC may instruct the substrate alignment sensor to locate datum points on the product substrate. As discussed above, the datum points may be used as reference markers for determining the relative location and orientation of the circuit trace on the product substrate. Further, the PC may instruct the die detector to locate one or more reference points on the die substrate to determine the outlay of the dies. 
         [0105]    Once the initial orientation of the product substrate and die substrate are determined, the PC may instruct the respective product substrate and die substrate conveyance mechanisms to orient the product substrate and die substrate, respectively, into a position of alignment with the transfer mechanism and the fixing mechanism  908 . 
         [0106]    The alignment step  908  may include determining the location of the portion of the circuit trace to which a die is to be transferred  910 , and where the portion is located relative to the transfer fixing position  912 . The transfer fixing position may be considered to be the point of alignment between the transfer mechanism and the fixing mechanism. Based on the data determined in steps  910  and  912 , the PC may instruct the product substrate conveyance mechanism to convey the product substrate so as to align the portion of the circuit trace to which a die is to be transferred with the transfer fixing position  914 . 
         [0107]    The alignment step  908  may further include determining which die on the die substrate will be transferred  916 , and where the die is located relative to the transfer fixing position  918 . Based on the data determined in steps  916  and  918 , the PC may instruct the wafer tape conveyance mechanism to convey the die substrate so as to align the die to be transferred with the transfer fixing position  920 . 
         [0108]    Once the die to be transferred from the die substrate and the portion of the circuit trace to which a die is to be transferred are aligned with the transfer mechanism and the fixing mechanism, the needle and the fixing device (e.g., laser) may be actuated  922  to effectuate the transfer of the die from the die substrate to the product substrate. 
         [0109]    After a die is transferred, the PC may determine whether additional dies are to be transferred  924 . In the case where another die is to be transferred, the PC may revert to step  908  and realign the product and die substrates accordingly for a subsequent transfer operation. In the case where there will not be another die transferred, the transfer process is ended  926 . 
       Example Direct Transfer Conveyor/Assembly Line System 
       [0110]    In an embodiment described with respect to  FIG. 10 , several of the components of the direct transfer apparatus described above may be implemented in a conveyor/assembly line system  1000  (hereinafter “conveyor system”). In particular,  FIGS. 2A and 2B  depict the product substrate  210  being held by the product substrate conveyor frame  214  and tensioned by the product substrate tensioner frame  216 . As an alternative to securing a product substrate conveyor frame  214  in a confined area via a system of motors, rails, and gear as indicated with respect to apparatus  200 ,  FIG. 10  illustrates the product substrate conveyor frame  214  being conveyed through the conveyor system  1000  in which the product substrate goes through an assembly line style process. As the actual means of conveyance between operations being performed on the product substrate being conveyed, the conveyor system  1000  may include a series of tracks, rollers, and belts  1002  and/or other handling devices to sequentially convey a plurality of product substrate conveyor frames  214 , each holding a product substrate. 
         [0111]    In some instances, operation stations of the conveyor system  1000  may include one or more printing stations  1004 . As blank product substrates are conveyed to the printing station(s)  1004 , a circuit trace may be printed thereon. In the case that there are multiple printing stations  1004 , the multiple printing stations  1004  may be arranged serially, and may be configured to perform one or more printing operations each so as to form a complete circuit trace. 
         [0112]    Additionally, in the conveyor system  1000 , the product substrate conveyor frame  214  may be conveyed to one or more die transfer stations  1006 . In the event that there are multiple die transfer stations  1006 , the multiple die transfer stations  1006  may be arranged serially, and may be configured to perform one or more die transfers each. At the transfer station(s), the product substrates may have one or more dies transferred and affixed thereto via a transfer operation using one or more of the direct transfer apparatus embodiments described herein. For example, each transfer station  1006  may include a wafer tape conveyance mechanism, a transfer mechanism, and a fixing mechanism. In some instances, a circuit trace may have been previously prepared on the product substrate, and as such, the product substrate may be conveyed directly to the one or more transfer stations  1006 . 
         [0113]    In the transfer stations  1006 , the wafer tape conveyance mechanism, the transfer mechanism, and the fixing mechanism may be aligned with respect to the conveyed product substrate conveyor frame  214  upon entering the station. In this situation, the transfer station  1006  components may repeatedly perform the same transfer operation in the same relative position on each product substrate as the plurality of product substrates are conveyed through the conveyor system  1000 . 
         [0114]    Moreover, the conveyor system  1000  may further include one or more finishing stations  1008  to which the product substrate may be conveyed to have final processing performed. The type, amount, and duration of the final processing may depend on the features of the product and the properties of the materials used to make the product. For example, the product substrate may receive additional curing time, a protective coating, additional components, etc., at the finishing station(s)  1008 . 
       Second Example Embodiment of a Direct Transfer Apparatus 
       [0115]    In another embodiment of a direct transfer apparatus, as seen in  FIGS. 11A and 11B , a “light string” may be formed. While many of the features of apparatus  1100  may remain substantially similar to those of apparatus  200  of  FIGS. 2A and 2B , product substrate conveyance mechanism  1102 , as depicted in  FIGS. 11A and 11B , may be configured to convey a product substrate  1104  that is different than the product substrate  212 . Specifically, in  FIGS. 2A and 2B , the product substrate conveyance mechanism  202  includes the conveyor frame  214  and the tensioner frame  216 , which secure the sheet-like product substrate  212  under tension. In the embodiment of  FIGS. 11A and 11B , however, the product substrate conveyance mechanism  1102  may include a product substrate reel system. 
         [0116]    The product substrate reel system may include one or two circuit trace reels  1106  that are wound with a “string circuit,” which may include a pair of adjacently wound conductive strings or wires as the product substrate  1104 . In an instance with only one reel, the reel  1106  may be located on a first side of the transfer position, and the pair of conductive strings ( 1104 ) may be wound around the single reel  1106 . Alternatively, there may be two circuit trace reels  1106  located on the first side of the transfer position, where each reel  1106  contains a single strand of the string circuit and the strands are then brought together to pass through the transfer position. 
         [0117]    Regardless of whether one reel  1106  or two reels  1106  are implemented, the die transfer process of forming the string circuit may be substantially similar in each case. In particular, the conductive strings of the product substrate  1104  may be threaded from the reel(s)  1106  across the transfer position and may be fed into a finishing device  1108 . In some instances, the finishing device  1108  may be: a coating device to receive a protective coating, for example, of a translucent or transparent plastic; or a curing apparatus, which may finish curing the string circuit as a part of final processing of the product. Additionally, or alternatively, the circuit string may be fed onto another reel, which may wind up the string circuit thereon before final processing of the string circuit. As the conductive strings of the product substrate  1104  are pulled through the transfer position, the transfer mechanism  206  may be actuated to perform a needle stroke (as described above) to transfer dies  220  to the conductive strings of the product substrate  1104  so that electrical contact terminals of the dies  220  are placed, respectively, on the adjacent strings, and the fixing mechanism  208  may be actuated to affix the dies  220  in position. 
         [0118]    Furthermore, apparatus  1100  may include tensioning rollers  1110  on which the conductive strings of the product substrate  1104  may be supported and further tensioned against. Thus, the tensioning rollers  1110  may assist in maintaining tension in the formed string circuit so as to enhance the die transfer accuracy. 
         [0119]    In  FIG. 11B , dies  220  are depicted as having been transferred to the conductive strings of the product substrate  1104 , thereby uniting (to some extent) the conductive strings of the product substrate  1104  and forming a string circuit. 
       Third Example Embodiment of a Direct Transfer Apparatus 
       [0120]    In an additional embodiment of a direct transfer apparatus, as seen in  FIG. 12 , apparatus  1200  may include a wafer tape conveyance mechanism  1202 . In particular, in lieu of the wafer tape conveyor frame  222  and the tensioner frame  224  shown in FIGS.  2 A and  2 B, the wafer tape conveyance mechanism  1202  may include a system of one or more reels  1204  to convey dies  220  through the transfer position of the apparatus  1200  to transfer dies to a single substrate. In particular, each reel  1204  may include a substrate  1206  formed as a narrow, continuous, elongated strip having dies  220  attached consecutively along the length of the strip. 
         [0121]    In the case where a single reel  1204  is used, a transfer operation may include conveying the product substrate  210  via the product substrate conveyance mechanism  202  substantially as described above, using motors, tracks, and gears. However, the wafer tape conveyance mechanism  1202  may include a substantially static mechanism, in that, while the dies  220  may be fed continuously through the transfer position by unrolling the substrate  1206  from reel  1204 , the reel  1204  itself main remain in a fixed position. In some instances, the tension of the substrate  1206  may be maintained for stability purposes by tensioning rollers  1208 , and/or a tensioning reel  1210 , which may be disposed on a side of the apparatus  1200  opposite the reel  1204 . The tensioning reel  1210  may roll up the substrate  1206  after the dies have been transferred. Alternatively, the tension may be maintained by any other suitable means to secure the substrate  1206  so as to assist in pulling it through the transfer position after each transfer operation to cycle through the dies  220 . 
         [0122]    In an embodiment where multiple reels  1204  are used, each reel  1204  may be disposed laterally adjacent to other reels  1204 . Each reel  1204  may be paired with a specific transfer mechanism  206  and a specific fixing mechanism  208 . In this case, each respective set of transfer mechanisms and fixing mechanisms may be arranged with respect to the product substrate  210  such that multiple dies may be placed in multiple locations on the same product substrate  210  simultaneously. For example, in some instances, the respective transfer positions (i.e., the alignment between a transfer mechanism and a corresponding fixing mechanism) may be in a line, offset, or staggered so as to accommodate various circuit trace patterns. 
         [0123]    Regardless of whether one reel  1204  or a plurality of reels  1204  are implemented, the die transfer operation may be relatively similar to the transfer operation as described above with respect to the first example embodiment of the direct transfer apparatus  200 . For instance, the product substrate  210  may be conveyed to a transfer position (die fixing position) in the same manner as described above via the product substrate conveyance mechanism  202 , the transfer mechanism(s)  206  may perform a needle stroke to transfer the die  220  from the die substrate  1206  to the product substrate  210 , and the fixing mechanism  208  may be actuated to assist in affixing the die  220  to the product substrate  210 . 
         [0124]    Note that in an embodiment with a plurality of reels  1204 , a circuit trace pattern may be such that not every transfer mechanism may need to be actuated simultaneously. Accordingly, multiple transfer mechanisms may be actuated intermittently as the product substrate is conveyed to various positions for transfer. 
       Fourth Example Embodiment of a Direct Transfer Apparatus 
       [0125]      FIG. 13  depicts an embodiment of a direct transfer apparatus  1300 . As in  FIGS. 2A and 2B , the product substrate conveyance mechanism  202  may be disposed adjacent to the wafer tape conveyance mechanism  204 . However, there is a space between the conveyance mechanisms  202 ,  204  in which a transfer mechanism  1302  may be disposed to effectuate the transfer of the dies  220  from the wafer tape  218  to the product substrate  210 . 
         [0126]    The transfer mechanism  1302  may include a collet  1304  that picks the dies  220 , one or more at a time, from the wafer tape  218  and rotates about an axis A that extends through arm  1306 . For example,  FIG. 13  depicts the wafer tape  218  facing the product substrate  210  such that the collet  1304  may pivot 180 degrees about pivot point  1308  (see directional pivot arrows) between the die-carrying surface of the wafer tape  218  and the transfer surface of the product substrate  210 . That is, the direction of extension of the collet  1304  pivots in a plane that is orthogonal to the surface or plane of transfer of both the wafer tape  218  and the product substrate  210 . Alternatively, in some embodiments, the arm structure of the collet may be arranged to pivot between two parallel surfaces, and the arm of the collet may pivot along parallel plane. Thus, when facing the wafer tape  218 , the collet  1304  may pick the die  220  and then immediately pivot to the surface of the product substrate  210  to be in line with the fixing mechanism  208 . The collet  1304  then releases the die  220  so as to transfer the die  220  to be affixed to the circuit trace  212  on the product substrate  210 . 
         [0127]    In some instances, the transfer mechanism  1302  may include two or more collets (not shown) extending from the arm in different directions. In such an embodiment, the collets may be indexed rotatingly 360 degrees through the collet stop locations and picking and transferring a die every time a collet passes the wafer tape  218 . 
         [0128]    Additionally, the one or more collets  1304  may pick and release the dies  220  from the wafer tape using positive and negative vacuum pressure through the collet  1304 . 
       CONCLUSION 
       [0129]    Although several embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the claims are not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as illustrative forms of implementing the claimed subject matter. Furthermore, the use of the term “may” herein is used to indicate the possibility of certain features being used in one or more various embodiments, but not necessarily in all embodiments.