Abstract:
A method for assembling a semiconductor device including the steps of providing a penetrable substrate having an adhesive surface and a plurality of dies disposed on the adhesive surface; providing a strap lead substrate having a plurality of strap leads disposed thereon; dispensing a first plurality of strap leads from the plurality of strap leads; providing a plurality of pins; bringing the penetrable substrate into close proximity with the strap lead substrate so as to bringing the first plurality of strap leads into contact with the plurality of dies; pressing the first plurality of strap leads against the plurality of dies using the plurality of pins; and, moving the penetrable substrate away from the strap lead substrate while using the plurality of pins to maintain contact between the first plurality of strap leads and the plurality of dies. An apparatus for assembling a semiconductor device is also disclosed.

Description:
BACKGROUND 
     1. Field 
     The present invention relates generally to manufacturing of semiconductor devices, and more particularly, to a method and apparatus for die transfer. 
     2. Background 
     Automatic identification of products has become commonplace. For example, the ubiquitous barcode label, placed on food, clothing, and other objects, is currently the most widespread automatic identification technology that is used to provide merchants, retailers and shippers with information associated with each object or item of merchandise. 
     Another technology used for automatic identification products is Radio Frequency Identification (RFID). RFID uses labels or “tags” that include electronic components that respond to radio frequency commands and signals to provide identification of each tag wirelessly. Generally, RFID tags and labels comprise an integrated circuit (IC, or chip) attached to an antenna that responds to a reader using radio waves to store and access the ID information in the chip. Specifically, RFID tags and labels have a combination of antennas and analog and/or digital electronics, which often includes communications electronics, data memory, and control logic. 
     One of the obstacles to more widespread adoption of RFID technology is that the cost of RFID devices such as tags or labels is still relatively high as lower cost manufacturing of RFID devices has not been achievable using current production methods. Additionally, as the demand for RFID devices has increased, the pressure has increased for manufacturers to reduce the cost of the devices, as well as to reduce the size of the electronics as much as possible so as to: (1) increase the yield of the number of dies (i.e., chips) that may be produced from a semiconductor wafer, (2) reduce the potential for damage, as the final device size is smaller, and (3) increase the amount of flexibility in deployment, as the reduced amount of space needed to provide the same functionality may be used to provide more capability. 
     However, as the chips become smaller, the process of interconnecting them with other device components, such as antennas, becomes more difficult. Thus, to interconnect the relatively small contact pads on the chips to the antennas in RFID inlays, intermediate structures variously referred to as “strap leads,” “interposers,” and “carriers” are sometimes used to facilitate inlay manufacture. Interposers include conductive leads or pads that are electrically coupled to the contact pads of the chips for coupling the chips to the antennas. These leads provide a larger effective electrical contact area between the chips and the antenna than do the contact pads of the chip alone. With the use of strap leads, the alignment between the chip and the antenna does not have to be as precise during the direct placement of the chip on the antenna as without the use of such strap leads. The larger contact area provided by the strap leads reduces the accuracy required for placement of the chips during manufacture while still providing effective electrical connection between the chip and the antenna. However, the accurate placement and mounting of the chips on strap leads and interposers still provide serious obstacles for high-speed manufacturing of RFID tags and labels. 
     Some challenges that currently face manufacturers or suppliers to component manufacturers include: 
     1) Wafer Processing: Transfer of chips from a wafer to a suitable substrate. 
     2) Chip Attachment: Accurately positioning of chips for attachment to strap leads is difficult to achieve at the speeds needed to achieve the economies of scale obtainable through high volume manufacturing. 
     3) Bonding: It is difficult to accurately bond, cure, and electrically connect the chips to strap leads at rates necessary to achieve high volume manufacturing. 
     Several possible high-speed strap assembly strategies have been proposed. The first approach, which uses the “pick-and-place” machines typically deployed in the manufacturing of circuit boards for picking up electronic components and placing them on circuit boards, is accurate, but requires expensive machines that ultimately do not deliver a sufficient throughput to justify the increased cost. That is, pick-and-place equipment may only be able to achieve 20-25,000 units per hour (UPH) whereas 100,000 UPH or more is needed for true high speed manufacturing. However, utilizing multiple pick-and-place machines in a line significantly increases the complexity of the manufacturing process and the possibility of error. 
     Another approach, referred to as a “self-assembly process,” is a method in which multiple chips are first dispersed in a liquid slurry, shaken and assembled into a substrate containing chip receiving recesses. Some current processes are described in U.S. Pat. No. 6,848,162, entitled “Method and Apparatus for High Volume Assembly of Radio Frequency Identification Tags,” issued to Arneson, et al. on Feb. 1, 2005; U.S. Pat. No. 6,566,744, entitled “Integrated Circuit Packages Assembled Utilizing Fluidic Self-Assembly,” issued to Gengel on May 20, 2003; and, U.S. Pat. No. 6,527,964, entitled “Methods and Apparatuses for Improved Flow in Performing Fluidic Self Assembly,” issued to Smith et al. on Mar. 4, 2003. Publications, patents and patent applications are referred to throughout this disclosure. All references cited herein are hereby incorporated by reference. 
     Accordingly, there is a long-felt, but as yet unsatisfied need in the RFID device manufacturing field to be able to produce RFID devices in high volume, and to assemble them at much higher speed per unit cost than is possible using current manufacturing processes. 
     SUMMARY OF THE PREFERRED EMBODIMENTS 
     A method for assembling a semiconductor device is provided herein. In one preferred embodiment, the method includes the steps of providing a penetrable substrate having an adhesive surface and a plurality of dies disposed on the adhesive surface; providing a strap lead substrate having a plurality of strap leads disposed thereon; dispensing a first plurality of strap leads from the plurality of strap leads; providing a plurality of pins; bringing the penetrable substrate into close proximity with the strap lead substrate so as to bringing the first plurality of strap leads into contact with the plurality of dies; pressing the first plurality of strap leads against the plurality of dies using the plurality of pins; and, moving the penetrable substrate away from the strap lead substrate while using the plurality of pins to maintain contact between the first plurality of strap leads and the plurality of dies. 
     A second method for creating a semiconductor device configured in accordance with one preferred embodiment of the present invention is also described herein. The method includes the steps of providing a plurality of strap leads on a strap lead substrate, each strap lead in the plurality of strap leads having a strap lead contact side; providing a plurality of dies on a penetrable die support substrate, each die in the plurality of dies having a die contact side facing the strap lead contact side of a respective strap lead in the plurality of strap leads; moving together the strap lead substrate and the penetrable die support substrate such that the die contact side of each die in the plurality of dies is in contact with the strap lead contact side of the respective strap lead; providing a plurality of pins; pressing the plurality of pins against the plurality of dies; and, separating the strap lead substrate and the penetrable die support substrate while using the plurality of pins to maintain contact between the plurality of dies and the plurality of strap leads. 
     An apparatus for assembling a semiconductor device is also disclosed. In one preferred embodiment of the present invention, the apparatus includes a pin platform having a plurality of pins with the pin platform having a first surface upon which the plurality of pins are displaced, each pin in the plurality of pins having a tapered end pointing away from the first surface. The apparatus also includes a penetrable die support substrate comprising a first surface and a second surface and a plurality of dies displaced on the first surface; and a strap lead support platform comprising a strap lead substrate with a plurality of strap leads displaced thereon. The strap lead support platform is alignable with the penetrable die support substrate such that the plurality of strap leads on the strap lead substrate are alignable with the plurality of dies on the penetrable die support substrate, with the first surface of the penetrable die support substrate facing the plurality of strap leads, and the first surface of the pin platform facing the second surface of the penetrable die support substrate. 
     Other features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description. It is to be understood, however, that the detailed description of the various embodiments and specific examples, while indicating preferred and other embodiments of the present invention, are given by way of illustration and not limitation. Many changes and modifications within the scope of the present invention may be made without departing from the spirit thereof, and the invention includes all such modifications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be more readily understood by referring to the accompanying drawings in which: 
         FIG. 1  is a top plan view of a die dispensing apparatus configured in accordance with one preferred embodiment of the present invention; 
         FIG. 2  is a flow diagram of a method for transferring a plurality of dies from a wafer in accordance to a preferred embodiment of the present invention; 
         FIG. 3  is a top plan view of a die dispensing apparatus configured in accordance with another preferred embodiment of the present invention; 
         FIG. 4  is a side view of the die dispensing apparatus of  FIG. 3 ; 
         FIG. 5  is a process for dispensing die using the die dispensing apparatus of  FIG. 3  pursuant to one preferred embodiment of the present invention; and 
         FIG. 6  is a top plan view of a die dispensing apparatus configured in accordance with yet another preferred embodiment of the present invention. 
       Like numerals refer to like parts throughout the several views of the drawings. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a single column die transfer mechanism  100  configured in accordance to one preferred embodiment of the present invention where the single column die transfer mechanism  100  has three platforms: 1) a pin platform  104 , 2) a wafer platform  168 , and 3) a strap lead (or antenna lead) platform  118 . In one preferred embodiment, the three platforms stack one above another, with the pin platform  104  being the top layer having a plurality of pins  102  pointing in a downwards direction. The wafer platform  168 , which is the middle layer, is also referred to as a penetrable carrier and is further described below. It should be noted that the description of the orientation of the various elements in this embodiment as “upwards” or “downwards” is not to be taken as a limitation because other orientations are suitable as well. Similarly, it should be noted that terms such as “top,” “topmost,” “bottom,” and “bottommost” are dependent on the orientation of the particular element being described, and similarly should not be taken as limitations on other possible embodiments. 
     A wafer  170  is adhered to the bottom of the wafer platform  168  with an adhesive. The wafer  170  is comprised of a plurality of dies  172  (illustrated in the figure as  172   a ,  172   b , and  172   c ). The strap lead platform  118 , which is the bottom-most layer, includes a strap lead substrate  120  having a plurality of strap leads  154  (illustrated in the figure as  154   a ,  154   b , and  154   c ) disposed thereon. In one preferred embodiment, the strap lead substrate  120  is a web that is unwound from a dispensing roll (not shown) and onto an uptake roll (not shown). The plurality of strap leads  154  on the strap lead platform  118  are facing upwards and ready to receive the plurality of dies  172  from the wafer  170 . In one preferred embodiment, the pitch between the strap leads of the plurality of strap leads  154  is a whole number multiple of the pitch between each of the dies in the plurality of dies  172 . Thus, for example, the pitch between each of the strap leads of the plurality of strap leads  154  can correspond directly on a one-to-one basis to the pitch between each of the dies in the plurality of dies  172 . In another example, the pitch between each of the strap leads of the plurality of strap leads  154  corresponds on a two-to-one basis to the pitch between each of the dies in the plurality of dies  172 . In yet another example, the pitch between each of the strap leads of the plurality of strap leads  154  corresponds on an N-to-one basis to the pitch between each of the dies in the plurality of dies  172 , where N is a whole integer. 
       FIG. 2  is a high-level overview of one preferred embodiment of a die punch process  200 , during which the plurality of dies  172  is transferred from the wafer platform  168  to the strap lead substrate  120  (i.e., the dies on the penetrable carrier are each transferred to a respective strap lead on the strap lead substrate  120 ) and attached thereto by an adhesive; and a bonding and curing stage  216 , during which the dies are simultaneously bonded to the strap lead substrate  120  and the adhesive cured. In one preferred embodiment, the die punch process  200  includes the following stages: a wafer platform and strap lead substrate alignment stage  206 , during which the dies on the wafer platform  168  are aligned to the strap lead substrate  120 . During the wafer platform and strap lead substrate alignment stage  206 , the wafer  170  is positioned so that a subset of the plurality of dies  172  is aligned with a corresponding subset of strap leads on the strap lead substrate  120 . 
     In one preferred embodiment, the plurality of pins  102  on the pin platform  104  are also aligned to the subset of plurality of dies to be transferred from the plurality of dies  172  and the corresponding subset of strap leads on the strap lead substrate  120 . The alignment sequence could also include the scenario of aligning the plurality of pins  102  to the subset of plurality of dies to be transferred before the corresponding subset of strap leads on the strap lead substrate  120  are aligned to both the plurality of pins  102  and the subset of plurality of dies to be transferred. Similarly, the plurality of pins  102  may be aligned to the corresponding subset of strap leads on the strap lead substrate  120  before the subset of plurality of dies to be transferred are aligned to both the plurality of pins  102  and the corresponding subset of strap leads on the strap lead substrate  120 . 
     As further described below, die punch process  200  also includes a die pinning stage  210 , where the dies are pinned to the strap lead substrate  120  using the plurality of pins  102 . In one preferred embodiment, the dies are adhered to the strap leads on the strap lead substrate  120 , as further disclosed herein. Then, in a penetrable carrier detachment stage  212 , the wafer platform  168  (penetrable carrier) is moved away from the pinned dies, leaving the pinned dies attached to the strap leads. It is noted that the plurality of pins  102  may puncture the penetrable carrier either during the pining down process (i.e., die pinning stage  210 ) or during the removal of the penetrable carrier (i.e., penetrable carrier detachment stage). A pin array removal stage  214 , where the plurality of pins  102  is moved away from the dies that are now attached to the strap lead substrate  120 . In one preferred embodiment, once the subset of plurality of dies to be transferred from the plurality of dies  172  is transferred to the corresponding strap leads on strap lead substrate  120 , an optional strap lead substrate dispensing stage  218  will be engaged to dispense additional strap leads so process steps  206  to  214  may be repeated, until all the dies of the plurality of dies  172  in wafer  170  are dispensed. Then, a plurality of dies from another wafer may be dispensed using the die punch process  200 . 
     In one preferred embodiment, all three platforms are independently movable in three axes, with a control system controlling the three platforms to precisely dispense the plurality of dies  172  in high speed, as further described herein. In another preferred embodiment, the pin platform  104  will only move up and down, while the wafer platform  168  will not only move up and down but also step horizontally to place a particular subset of dies  172   b  of the plurality of dies  172  to be under and aligned with the plurality of pins  102  to be punched and transferred to a respective subset of strap leads  154   b . The strap lead substrate  120  will be wound up in one direction, and after each winding of the web, fine alignment of the strap lead substrate  120  to the plurality of pins  102  and the wafer  170  may be needed. 
     In one preferred embodiment, the plurality of pins  102  as well as the plurality of strap leads  154  on the strap lead substrate  120  are configured in a single linear column. The approach can transfer the plurality of dies  172  from the wafer  170 , which is in a circular configuration, to a liner continuous web. As noted herein, in one preferred embodiment of the present invention, the pitch between each strap lead in the plurality of strap leads  154  is a whole number multiple of the pitch between each of the dies in plurality of dies  172 . Thus, the pitch between each strap lead in the plurality of strap leads  154  can be equal to the pitch between each die in the plurality of dies  172 , providing a one-to-one correspondence between the strap leads and the dies. 
     To ensure that all the dies in the longest die column of the wafer  170  are transferable to the strap lead platform  118 , the length of the pin array (i.e., the plurality of pins  172 ) has to be at least equal or larger than the diameter of the wafer  170  to be processed by the single column die transfer mechanism  100 . In other words, the number of pins in the plurality of pins  172  has to be at least as numerous as the number of dies contained in the longest diameter of the wafer  170 . In other preferred embodiments, any number of pins in the plurality of pins  172  may be used, except that multiple die transfer operations may be necessary for a single column of the wafer  170  if the length of the pin array is shorter than the diameter of the wafer  170  to be processed. Similarly, the strap lead platform  118  has to be at least as long as the diameter of the wafer  170 . However, in the configuration as shown, some of the pins in the plurality of pins  102  as well as a few strap leads  156  of the plurality of strap leads  154  on the strap lead platform  118  are redundant for the purposes of transferring dies from a shorter column of the wafer  170 . Although having redundant pins and strap leads will ensure that all the dies of the plurality of dies  172  of the wafer  170  can be transferred, the redundant strap leads  156  will be unused and presumably wasted. Considering that the die is typically the component in an RFID inlay construction having the highest cost, it is preferred that all dies in the plurality of dies  172  are transferred (i.e., it is preferred that no dies are left on the wafer  170  and presumably wasted). However, the presence of the redundant strap leads  156  may cause contamination because the adhesive on the redundant strap leads  156  may smear onto the wafer  170  or the wafer platform  168 . 
       FIG. 3  illustrates a top plan view and  FIG. 4  illustrates a side view of a die transfer mechanism  300  configured in accordance with another preferred embodiment of the present invention. In this embodiment, die transfer mechanism  300  is configured to minimize adhesive smearing during the transfer of dies in a short die column while still using a strap lead platform  318  that is as long as the diameter of the wafer  170 . The strap lead platform  318  also includes an angled portion  318   a  that is angled to reduce the possible contamination of adhesives for dies that are not being placed. The wafer platform  168  includes a penetrable carrier substrate  404  and an adhesive layer  406 . The wafer  170  is attached to the adhesive layer  406 , with the wafer  170  adhered to the bottom of the penetrable carrier substrate  404 . In  FIG. 4 , it is illustrated that a frame  402  holds the penetrable carrier substrate  404 . 
     Referring also to  FIG. 5 , which will be used to describe the operation of the die transfer mechanism  300 , the die transfer mechanism  300  can be used in a process  500  that begins with step  502 , where the strap lead substrate  320  is wound so that there are just enough empty strap leads sitting on the strap lead platform  318 . In one preferred embodiment of the present invention, having enough empty strap leads means that a number of empty strap leads  354   b  (i.e., strap leads with no die) is approximately equal to a number of dies to be punched out  372   b  from the die column in the next punch operation, with the last empty strap lead placed at the end of the strap lead platform  318  from which the strap lead substrate  320  is entering. The strap lead substrate  320  will have straps  372   a  (i.e., strap leads with dies already dispensed thereon) sitting at the other end of the strap lead platform  318  (i.e., the end of the strap lead platform  318  from which the strap lead substrate  320  exits the strap lead platform  318 ). In step  504 , the strap lead platform  318  is moved so that all the empty strap leads  354   b  are aligned with both the dies to be punched  372   b  and the plurality of pins  102  to be used to punch the dies  372   b . Then, in step  506 , the punch operation is performed to transfer the dies to be punched  372   b  to the empty straps  354   b . As illustrated, die  372   b , strap lead  354   b  and adhesive  362  comprise a device to be assembled  380 . 
     The embodiments referred to above has been described using a single column of pins and strap leads. However, using only a single column of pins and strap leads significantly limit the throughput of the die transfer process. To further improve the throughput of the process, in one preferred embodiment it is desirable to have multiple single-column strap lead substrates and multiple column of pins working concurrently. In one preferred embodiment, as illustrated in  FIG. 6 , the wafer  170  can be divided into several segments of equal width (e.g., 8 segments for an 8 inch wafer, with each segment being approximately 1 inch wide). Each segment of the wafer  170  will have its own single-column pin array (not shown) with the pin array length approximately equal to the longest column of the total number of dies in each segment. Each segment of the wafer  170  will also have its own single-column strap leads  604  and strap lead platform  602  with the strap lead platform  602  approximately equal to the longest column of the total number of die in each segment. The manner in which each single-column pin array is placed, how each single-column strap lead substrate is wound, how each column of dies are aligned to and attached to each strap lead on each single column strap lead platform  602  follows the procedure described above. 
     In one preferred embodiment of the present invention, all pins move up and down together, therefore one punch will transfer a set of dies out of each wafer section to their corresponding strap lead platform  602 . In this embodiment, it is necessary to synchronize each strap lead platform  602  so that each one follows the three step procedure described in  FIG. 5  to receive dies. Thus, it is necessary to: 1) determine how may dies will be transferred out in the next punch while winding up the strap lead substrate with the predicted number of empty strap leads and aligning the last empty strap lead to the edge of the strap lead platform  602 ; 2) move each strap lead platform  602  so that each of the empty straps are aligned to both the dies to be punched and the pins to be used to punch the dies; and 3) when all the strap lead platforms  602  have finished steps 1 and 2, proceed to punch and transfer the dies. 
     Portions of the die punch/transfer and attachment process described herein may be optional and the described process may include portions that are not needed for a particular application. Therefore, the description contained herein should be read as illustrating exemplary embodiments of a novel die transfer process as practiced in one preferred embodiment of the present invention and should not be read in a limiting sense. Specifically, the die transfer process described herein is applied to the linear transfer of all dies from a wafer, where dies are being attached to strap leads. 
     The embodiments described above are exemplary embodiments of the present invention. Those skilled in the art may now make numerous uses of, and departures from, the above-described embodiments without departing from the inventive concepts disclosed herein. Accordingly, the present invention is to be defined solely by the scope of the following claims.