Abstract:
1. A method for packaging wafers having a bottom side and a top circuit side in jars comprising the steps of  
     placing a cassette having a plurality of pockets for wafers at the back side facing upwardly, transferring the top wafer in the cassette by means of a vacuum suction mechanism which centers the top wafer in the cassette pocket upon initial engagement and then transfers and discharges the wafer in a jar located at a jar station and feeding interleafs in timed relation to the wafer feed so that an interleaf is positioned between each wafer loaded in a jar.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    These wafers are very fragile and expensive, some wafers being valued in the order of $10,000.00 and accordingly, equipment of the type to which the present invention relates must be capable of handling the wafers very carefully to minimize damage. In accordance with some prior art systems, the wafer holder cassette is placed in the loader with the circuit side of the wafer facing upwardly and then removed from the pockets in the cassette by apparatus which engages under a wafer in the cassette to withdraw it and then rotates the wafer so that the bottom faces upwardly before it is discharged into the wafer jar container. Paper liners are interleaved between the wafers stacked in the wafer jar container by mechanism including a suction cup or vacuum system which limits the type of interleaf material that can be used and eliminates some form of economic porous papers which would serve the purpose adequately from separating the wafers in the wafer jar container.  
         SUMMARY OF THE INVENTION  
         [0002]    With the foregoing in mind, it is an object of the present invention to provide a system and apparatus for automatically removing wafers from cassettes and safely loading them into shipping jars wherein characterized by novel features of construction and arrangement providing a system which transfers the wafers quickly and safely virtually eliminating counting errors and mishandling of wafers.  
           [0003]    In the system of the present invention the cassettes are mounted at a loading station with the H-bar facing up which orientation presents the bottom non-circuit side of the wafers and thus eliminating the need to rotate wafers in the transfer process. Accordingly, wafers are picked up from the back side and therefore jar loading is smoother and faster and the risk of mishandling of wafers is further reduced.  
           [0004]    More specifically, the wafer transfer mechanism of the present invention utilizes a vacuum pick and place arm mechanism with a vacuum generator built in integrally to provide a linear transfer, which is smooth and vibration free one wherein the wafers are levitated in the initial transfer cycle so that they do not engage the ribs defining the wafer pockets in the cassette and wherein the wafer is released and gently guided into the jar to ensure safe, accurate, even placement.  
           [0005]    The wafer jar container is positioned on a shelf at the wafer loading station that is easily retractable for easy access and incorporates mounting guides which ensure proper jar positioning. The configuration is such that it accommodates all popular styles of jar containers.  
           [0006]    Another feature of the system and apparatus of the present invention is the particular configuration and arrangement of the interleaf loading chamber and interleaf chute and the means for storing and discharging one interleaf at a time in timed relation with the wafer transfer mechanism so that interleaves are positioned quickly and accurately in the jar container between all of the wafers during a loading cycle. The pull out chamber holds up to 500 interleaves and the system is designed to accommodate either porous or non-porous interleaves which are carbon based. As explained in detail, hereinafter, the system is set up for maintaining automatic pressure on the stack of interleaves and includes a low paper sensor signal which signals the operator when reloading is required. The interleaf chute assembly is characterized by novel features of construction and arrangement whereby interleaves are fed into the chute until a wafer is in a jar and when the interleaf is released, advanced interleaf placement technology insures accurate, gentle insertion of the interleaves into the jar.  
           [0007]    Summarizing the features of the Wafer Jar loader System and Apparatus of the present invention, the system has a high capacity and is capable of loading 10 wafers per minute, it accommodates all styles of commonly used jar containers up to 3 ⅛ inch deep, accepts all popular styles of wafer holder cassettes and runs porous tyvek or non carbon based interleaves.  
           [0008]    The apparatus is rather simple and compact in design and presents a clear operator view to the wafer transfer process by reason of a see-through plexidome housing which protects the wafers without obscuring visibility. The main controls of the system are easy to access and the short cassette to jar distance maximizes through put and minimizes the chances of mishandling and damage to wafers.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    These and other objects of the present invention and the various features and details of the operation and construction thereof are hereinafter more fully set forth with reference to the accompanying drawings, wherein;  
         [0010]    [0010]FIG. 1 is a plan top view of the Wafer Jar Loading system showing the functional stations and operating elements;  
         [0011]    [0011]FIG. 2 is a sectional view taken along line A-A of FIG. 1 showing details of the Wafer Jar Loading system;  
         [0012]    [0012]FIG. 3 is a side and top plan view of an inverted cassette showing the H-Bar upward and used as a datum for registering the cassette and wafers;  
         [0013]    [0013]FIG. 4 is a schematic which illustrates of the sequence and order of a typical wafer jar container loading process. Major elements of the loading process are shown removed from the system for clarity of operation. The sequence is automatically continued until all wafers are loaded into a shipping container jar. The operator then reloads wafers, container jar, and interleaf material to start another loading process;  
         [0014]    [0014]FIG. 5A is a side view of a cassette;  
         [0015]    [0015]FIG. 5B is a side view of a cassette holder;  
         [0016]    [0016]FIG. 6A is a side elevation view of a cassette installed in a cassette holder with lever and cam mechanism in an unseated position;  
         [0017]    [0017]FIG. 6B is a side elevation view of a cassette installed in a cassette holder with lever and cam mechanism in a seated position;  
         [0018]    [0018]FIG. 7A is a detail of holder switch indicating that cassette in an unseated position;  
         [0019]    [0019]FIG. 7B is a detail of holder switch indicating that cassette is in the seated position;  
         [0020]    [0020]FIG. 8 is a side elevation view partly in section showing the spring biasing means for normally biasing the wafer locating plate in operative limit position;  
         [0021]    [0021]FIG. 9 is a top plan view with parts broken away of the cassette and the wafer seating assembly into limit positions;  
         [0022]    [0022]FIG. 10 is a top plan view of the transfer pickup station showing extreme limit positions for the suction pickup;  
         [0023]    [0023]FIG. 11 is a transverse sectional view taken of lines  11 - 11  of FIG. 10;  
         [0024]    [0024]FIG. 12 is a side elevational view of the suction pickup and wafer cassette prior to activation of the suction cup to engage the uppermost wafer in the cassette;  
         [0025]    [0025]FIG. 13 is a view similar to FIG. 12 showing the details of the vacuum transfer mechanism;  
         [0026]    [0026]FIG. 14 is an enlarged transverse sectional view through the shipping container or jar;  
         [0027]    [0027]FIG. 15 is a fragmentary view showing the suction pickup engaging the uppermost wafer;  
         [0028]    [0028]FIG. 16 is a fragmentary view showing the gap sensor and flag which determines the engaging stroke of the suction pickup;  
         [0029]    [0029]FIG. 17 is a fragmentary view showing automatic centering of the uppermost wafer when vacuum is applied to the cup;  
         [0030]    [0030]FIGS. 18, 19,  20  are transverse sectional views of another embodiment of suction vacuum pickup device in accordance with the present invention;  
         [0031]    [0031]FIG. 21 is a view showing the cup mounted on the section pickup arm;  
         [0032]    [0032]FIG. 22 is a fragmentary sectional view showing the suction pickup showing the second embodiment of a suction pickup engaging the uppermost wafer in the cassette;  
         [0033]    [0033]FIG. 23 is a fragmentary view showing the centering function;  
         [0034]    [0034]FIG. 24 is a view of the control panel;  
         [0035]    [0035]FIG. 25 is a perspective view of a wafer non-inverted cassette;(inverted cassette)  
         [0036]    [0036]FIG. 26 is a fragmentary perspective view showing some of the details of the interleaf station;  
         [0037]    [0037]FIG. 27 is a perspective interleaf station showing the interleaf storage container;  
         [0038]    [0038]FIG. 28 a plan view of the interleaf station;  
         [0039]    [0039]FIG. 29 is a fragmentary section taken on lines  29 - 29  of FIG. 28 showing a slide drawer;  
         [0040]    [0040]FIG. 30 is a sectional view taken on lines  30 B- 30 B of FIG. 30A;  
         [0041]    [0041]FIG. 30A is a transverse sectional view showing the interleaf loading mechanism;  
         [0042]    [0042]FIG. 31 show the switches for the cam nut design featured in FIG. 30;  
         [0043]    [0043]FIG. 32 is a bottom plan view of the pulley for activating the leafs through on the interleaf lift mechanism;  
         [0044]    [0044]FIG. 33 is an enlarged sectional view showing the interleaf stack and wheel runner;  
         [0045]    [0045]FIG. 34 is a fragmentary sectional view similar to FIG. 33 showing the wheel runner in its initial retract position to condition the uppermost interleaf for discharge from the stack;  
         [0046]    [0046]FIG. 35 is a perspective view of the portion of the interleaf mechanism for taken on lines G-G of FIG. 34;  
         [0047]    [0047]FIG. 36 is a fragmentary view showing the wheel runner advancing the uppermost interleaf to positioned where it can be discharged down the chute to the jar;  
         [0048]    [0048]FIG. 37 is a perspective view showing the interleaf in position to be discharged to the jar; and  
         [0049]    [0049]FIG. 38 is a view showing the interleaf discharging into the jar.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0050]    Referring now to FIGS. 1 and 2, there is shown a top plan view and a side section view respectively of a system and apparatus  10  for packaging wafers W in shipping containers J. The system  10  is shown removed form its housing and comprises a cassette loading station  14 , a transfer pickup station  16 , for removing wafers W from cassettes C, a shipping container station  18  with pull out shelf  21  to position containers for loading, a slide drawer interleaf station  22 , and an operator control station that initiates the automatic sequencing of alternately placing wafers W and interleafs I into shipping containers J as well as controlling and monitoring all other functions.  
         [0051]    In FIG. 2 three cassette loading positions are shown; an initial load position  26 , a wafer number  1 , load position  28 , and a wafer number  25 , load position  30 . As wafers W are transferred to the shipping container J, the cassette C is incrementally raised by cassette lift mechanism. Wafers W are transferred from cassette C to shipping container J as the pickup arm  34  with pickup cup  36  traverses distance  38  along a horizontal track  40  depositing wafers W in a shipping container J. FIG. 1 shows a shipping container J on pull out shelf  21  in two positions; with the pull out shelf extended as at  21   a  and seated as at  21   b . The shipping container J generally contains a foam ring  42  around the internal periphery and a foam bottom pad  44  to cushion and protect wafers W. Pull out shelf  21  sits on positioning mechanism  46  that rides along two horizontal tracks  48 . Interleaf slide drawer is shown with cover  52  raised and is comprised of a slide drawer  54  for a supply of interleafs  1 , an interleaf feed wheel  56  and peel blade  58 , an interleaf lift mechanism  60 , and an interleaf chute  62 . Slide drawer  54  is shown in an open position  54   a  and seated position  54   b .  
         [0052]    Considering the system and apparatus in terms of function and referring to FIGS. 1 and 2, wafers W housed in a conventional cassette C are transferred one at a time from the cassette C to the shipping container J. In accordance with the present invention, the cassette C is positioned so that the wafer&#39;s circuit sides are down facilitating easy and rapid transfer of wafers W from the cassette C to the shipping container J without the need for expensive and complicated robotics to rotate wafers. To facilitate understanding of the following embodiment, a schematic representation of the container loading sequence is shown in FIGS. 4, 10 and  11 . FIG. 4 shows a wafer cassette C having a transport handle, a so-called H-Bar  64  which also provides the loading surface datum  66 . A typical shipping container J with foam pad ring  42  and foam pad disc  44  is inserted to protect wafers W during loading and shipping. As illustrated, container loading is achieved in a predetermined sequence. A disc-like interleaf I is first inserted (interleaf No.  1 ) followed by a wafer W (wafer No. 1 ). This sequence and order repeats until the desired number (N) of wafers W have been placed in container J. When wafer w (No. N) is placed into container J one more interleaf I (No. N+1) is placed into container J. The container J is removed and foam filler pads  68  are placed inside container J to fill remaining space above wafer W (No. N) before installing container lid.  
         [0053]    Wafers W have two flat surfaces with one being the back and the other being the circuit side. The nominal wafer orientation in cassettes C is with the backside facing toward the bottom and the circuit side facing up. However, packaging in containers J require the circuit side facing down towards the container bottom. With the backside facing upwardly unpacking wafers W is easier and more rapid since only the back surface can be handled leaving the circuit side untouched. Unique to the present invention is the upside down and inverted positioning of the cassette C, eliminating the need to flip the wafer upside down for placement into the container J. This simplifies the automation process, speeds the loading and more importantly reduces handling.  
         [0054]    The cassette loading station  14  is comprised of a wafer cassette C illustrated in FIG. 1 and  2 , a cassette holder  82  shown in FIG. 5A, 5B,  6 A, and  6 B, and a cassette lift mechanism. The wafer cassette C is of conventional design and typically made of a plastic material and has a pair of sidewalls  72  and  74  and a series of ribs  26  which define pockets  78  for the wafers W. A clearance between wafers W (see FIG. 3) and the pockets  78  allow wafers W to be removed from the pockets  78  without damage. The cassette C is positioned so that the H-Bar  64  is facing up thereby locating surface datum  66  in an upward position with the transport handle  80  in a downward position.  
         [0055]    Cassette holder comprises a housing  82  having sides  84  and  86 , and a base  88 . Base  88  has a pair of runners  90  and  92  (FIGS. 7A and 7B) which complement the bottom shape of cassette C so that cassette C can slide in place in a longitudinal direction into cassette holder. Cassette C has a so called H-Bar  64  which aligns with the top plate  94  of cassette holder. When cassette C is locked in place, H-Bar  64  engages switch  96  (FIGS. 6A, 6B) to condition the apparatus and system  10  for transferring wafers W into shipping container J in a manner described hereafter.  
         [0056]    A wafer-seating plate  100  having a curved front face  102  complementing the curvature of wafers W is engaged by wafers W when the cassette C is positioned in place in the cassette holder. The function of the wafer-seating plate  100  is to ensure that all of wafers W are fully seated in cassette pockets  78  so that the pickup arm  34  engages the back side surface of each wafer  12  in the same relative position thereby properly aligning the wafers W when they are transferred to the shipping container J.  
         [0057]    When the cassette C is in place in the manner described above, the handle  83  is rotated from its horizontal rest position as shown in FIG. 6A to the position shown in FIG. 6B. Through a linkage  104  and cam  106  arrangement, the wafer-seating plate  100  moves forwardly so that there is a predetermined clearance between the front face of seating plate  100  and wafer W to permit transfer of wafers W in a manner to be described. As shown in FIG. 6A, the wafer-seating plate  100  is normally biased to a forward limit position (cam position A, FIG. 8) by a pair of compression springs  108 . A slide bearing  110  supports the wafer-seating plate  100  so that it moves in a truly horizontal plane and does not cock during activation between cam position A and cam position B thereby seating all of wafers W in a uniform fashion. The actuation of the handle  83  raises cassette C so that the H-Bar  64  engages and locks in place with the top plate  94  of cassette holder  82 . When cassette C is fully locked in place, switch  96  conditions the system for operation and feed and transfer of wafers W from the cassette C to the transfer station  16 . The clearance between the wafers W and the wafer-seating plate  100  ensures incremental vertical displacement of the cassette C during the transfer cycle in a manner to be described in more detail hereafter.  
         [0058]    [0058]FIG. 8 illustrate the wafer-seating plate  100  when the cassette C is loaded and when the lift handle  88  is rotated. FIG. 9 is a cut-away to show a top view of the cam linkage  104 . The wafer-seating plate  100  is split along the center showing the portion with respect to the wafer W and cassette C with cam  106  in position A and B. When at position B, the cassette C is raised and the H-Bar  64  is deflected as shown in FIG. 9. FIG. 8 illustrates the linear motion achieved upon moving cam  106  from position A to B and details the opposing linear compression spring  108  stroke limit screw  112  and linear slide bearing  110  arrangement.  
         [0059]    Consider now the pick up transfer station  16  of FIGS. 1 and 2 and with reference to FIGS. 10, 11 and  12 . When switch  96  in cassette holder  82  is activated by H-Bar  64  verifying that cassette C has been loaded in correct orientation, pick up arm  34  is enabled for automatically transferring wafers W from cassette C to shipping container station  18 . FIG. 11 is a side cutaway view wherein the pickup arm  34  transfers wafer W to wafer release position  134 . FIGS. 11 and 12, are side and front elevation views of transfer pickup arm assembly  34  and cassette C. The portion of cassette holder  70  that secures and registers the H-Bar  64  has been hidden from this figure for explanation of the wafer pickup sequence. The pickup/transfer arm assembly  34  consists of a vacuum cup  136 , slide arm  138 , slide base  140 , gap sensor  142 , interrupt flag  144 , counterbalance extension springs  146 , and two-screw stops  148 . The slide arm  138  is shown in a starting position where the slide arm  138  is downward and arrested on two-screw heads  148  and stop surfaces  148 . The two counter balance springs  146  add resistance in the opposite direction to reduce the effective weight of the slide arm assembly  140  that will contact the wafer W. FIG. 12 best illustrates the gap sensor  142  and interrupt flag  144  relationship with the slide arm  140  in the starting position. The distance between the sensor  142  and the flag  144  allow for detection of contact with the wafer W. The amount of slide arm  138  movement can be varied by adjusting the distance away from the sensing point. For compliant type vacuum cups  136 , this distance allows the cup to collapse without pulling the wafer W upward against the cassette C top side support grooves. As illustrated in FIG. 15, the vacuum cup  136  illustration identifies “cup support ribs”  150 . These ribs  150  are stops within the vacuum cup  136  which limit the amount of compliance on vacuum cup  136  when vacuum is drawn. FIG. 15 shows the vacuum cup  136  making initial contact with the wafer W. The wafer  12  continues being raised until the flag  144  interrupts the sensor  142  within the gap distance shown in FIG. 15. Once the sensor  142  is blocked, cassette C motion is stopped and vacuum is turned on to the vacuum cup  136 . As vacuum builds up, the cup  136  begins to collapse. This collapsing motion allows the slide arm  58  to move downward until the stop surfaces  148  are engaged by the screw head  152 . Then the balance springs  146  lift the wafer W off the bottom side guides as shown in FIG. 16. The last motion is when the cassette C is lowered a programmed amount to center the wafer within the cassette support slots and the wafer is pulled out.  
         [0060]    Consider now a typical cycle of operation with the parts in the position shown in FIGS. 10 and 11. The pickup transfer arm  34  is moved from a position overlying the container J to the wafer W and then the cassette C is raised so that the top wafer W engages the vacuum cup  136  and displaces the slide arm  58  a predetermined distance as determined by gap sensor  142 . This initiates the vacuum which causes the vacuum cup  136  to flatten and tend to displace a wafer W upwardly a predetermined small distance. However, the slide arm  58  can return to its home position and in this position, the wafer W is centered in its pocket  32  to avoid any biasing in the grooves of the cassette C which may damage the wafer W. When all of the wafers W in a given cassette C have been transferred from the cassette C to jar or container J, the control panel then signals the operator to replace the empty cassette C with another full one. The system  10  can be set to transfer selected numbers of wafers W for an automatic cycle of operation.  
         [0061]    Consider now briefly part of an operational cycle and assume that the pickup arm overlies the wafer W and the system is ready to initiate a transfer cycle. In position  132  of pickup arm  34 , a cassette drive motor elevates the cassette holder  82  and when the top wafer W engages the suction cup  136 , the sensor flag  144  activates the gap sensor  142  which signals the cassette motor to stop. Simultaneously, the vacuum cycle is activated. The vacuum causes the suction cup  136  to comply. The arrangement just described including the flag  144  sensor  142  and limited range of travel of a slide arm  138  in slide base  140  ensures that wafers W are not damaged or are biased in the cassette pockets  78  during a transfer cycle. The pickup assembly further includes counter-balancing springs  180  extending from a projection on slide base  140  to the slide arm  138  as shown in FIG. 12. This arrangement minimizes load on the wafers W and on the suction cup  136  when the cassette C is raised in the manner described above wherein the top wafer is engaged initially by the suction cup  136  again in the manner described above.  
         [0062]    Considering now the Interleaf station  22 , and referring to FIGS. 26 and 27, perspective views of the Interleaf feed mechanism are shown. Disc-like interleafs I made of a tissue paper product are stacked in Interleaf holder  240  (shown in an op load position), automatically released and interspersed one at a time between wafers(W). In FIG. 26, the Interleaf cover  241  is shown in an open position exposing the paper buckle and release mechanism  242 , Interleaf queue and release station  243 , air cushion chute  244 , and Interleaf lift mechanism  245 . Interleaf holder  240  is an elongated generally rectangular slide drawer  246  having an open bottom depending-cylindrical container  247 . interleafs I are stacked on top of a vertically movable lifter pad  248  which is attached to the upper end of lifter adjustment screw  249  and projects into the open bottom of cylindrical container  247 . lnterleafs I are held in place in the cylindrical container  247  of Interleaf holder  240  by a semi-circular back edge retainer  250  of FIG. 28 which projects slightly beyond the opening of cylindrical container  247  to engage an annular portion of the top Interleaf I. A peel blade  251  having an entrance and exit ramps  252  and  253  respectively extends over the Interleaf opening at approximately from the rim  254  to hold the interleafs I in place in the manner shown in FIG. 28.  
         [0063]    When the slide drawer  246  is seated, as shown in FIG. 28, Slide drawer front edge  255  depresses switch  256  and ball plunger  257  extends in slide drawer detent grooves  258  seating slide drawer  2 , and preparing the system  10  for sequential operation.  
         [0064]    With slide drawer  246  in place, the feed sequence begins with the Interleaf lift mechanism  245  raising the interleafs I up to peel blade  251  and back edge retainer  250  applying a constant but controlled force as shown in FIG. 33. The distance between pre-load springs  259  and upper support angle  260  and lower support angle  261  achieve this constant force as shown in FIG. 33. Both support angles  260  and  261  are attached to two linear rail bearing slide blocks  262  and  263 .Both upper support angle  260  and lower support angle  261  and bearing blocks  262  and  263  have the pre-load gap/distance maintained by threaded rod and pre-load adjustment nut  265 . The threaded rod&#39;  264  is attached to a threaded spring post  266  and locked with nut  267 . The opposite end passes through a clearance hole in spring post  268  and through lower support angle  261 . The pre-load adjustment  265  works against pre-load springs  259  to maintain a predetermined distance between upper support angle  260  and lower support angle  261 . The pre-load adjustment nut  265  has a tapered surface which makes contact with a pre-load sense switch that indicates nut  265  is seated against lower support angle  261 .  
         [0065]    During the Interleaf lift cycle, the force of the pre-load spring  265  will be exceeded causing upper support angle  260  and bearing block  263  to move toward opposing bearing block  262 . This movement causes pre-load nut  265  to move away from lower angle  261 . This small movement causes switch  269  to change state deactivating pre-load drive motor  270  which stops drive belt  271  and pulleys  272  This small is illustrated on FIG. 31 wherein detail “IC” shows switch  269  in a normally open condition on tapered surface of adjustment nut  265  which indicates no pre-load sensed and detail “D” shows switch  269  off taper of adjustment nut  265  in a normally closed condition which indicates a pre-load is sensed. Detail “D” also shows the gap  273  within which the pre-load switch  269  operates. Section E-E of FIG. 32 is a bottom view of the pulleys  272  and drive belt  271  that drive lead screw  271 A with attached lead screw nut  2713 . Lifting of lifter pad  248  by lead screw  271 A is achieved through the drive belt  271  and pulleys  272 . Lead screw  271 A is supported by two angular contact bearings  273  and retained through a mounting block  274  via a bearing take up nut  275 . On activation of pre-load drive motor  270 , lead screw  271 A through drive belt  271  and pulleys  272  and motor  270  cause the nut  275  to move up/down depending on state of switch  269 . Lower stroke limit sensor  276  and upper stroke limit sensor  277  control and limit the extent of Interleaf lift travel  278 . Stroke limit sensors are triggered when the sensor flag  279  interrupts a light beam. This i illustrated in FIG. 30A with the flag  279  shown at the lower stroke limit position. Section E-E of FIG. 32 shows a view of flag  279  passing through the sensor. During the upward cycle of raising and pre-loading interleafs, the pre-load switch  269  is activated and motor  270  stops until enough Interleaf sheets have been stripped from the stack to reactivate switch  269  and turn on motor  270 . This sequence repeats until the upper stroke limit sensor  277  is blocked by flag  279 . When this upper limit has been reached and switch  269  activates indicating no more pre-load is present, the motor is reversed until the sensor flag  279  returns to the starting lower limit stroke  276  position.  
         [0066]    Considering now the interleaf station  22 , and referring to FIGS. 26 and 27, perspective views of the interleaf feed mechanism are shown. Disc-like interleafs I made of a tissue paper product are stacked in interleaf holder  240  (shown in an open load position), automatically released and interspersed one at a time between wafers(W). In FIG. 26, the interleaf cover  241  is shown in an open position exposing the paper buckle and release mechanism  242 , interleaf queue and release station  243 , air cushion chute  244 , and interleaf lift mechanism  245 . Interleaf holder  240  is an elongated generally rectangular slide drawer  246  having an open bottom depending cylindrical container  247 . Interleafs I are stacked on top of a vertically movable lifter pad  248  which is attached to the upper end of lifter adjustment screw  249  and projects into the open bottom of cylindrical container  247 . Interleafs I are held in place in the cylindrical container  247  of interleaf holder  240  by a semi-circular back edge retainer  250  of FIG. 28 which projects slightly beyond the opening of cylindrical container  247  to engage an annular portion of the top interleaf I. A peel blade  251  having an entrance and exit ramps  252  and  253  respectively extends over the interleaf opening at approximately from the rim  254  to hold the interleafs I in place in the manner shown in FIG. 28.When the slide drawer  246  is seated, as shown in FIG. 28, Slide drawer front edge  255  depresses switch  256  and ball plunger  257  extends in slide drawer detent grooves  258  seating slide drawer  246  and preparing the system  10  for sequential operation. With slide drawer  246  in place, the feed sequence begins with the interleaf lift mechanism  245  raising the interleafs I up to peel blade  251  and back edge retainer  250  applying a constant but controlled force as shown in FIG. 33. The distance between pre-load springs  259  and upper support angle  260  and lower support angle  261  achieve this constant force as shown in FIG. 33. Both support angles  260  and  261  are attached to two linear rail bearing slide blocks  262  and  263 . Both upper support angle  260  and lower support angle  261  and bearing blocks  262  and  263  have the pre-load gap/distance maintained by threaded rod and pre-load adjustment nut  265 . The threaded rod  264  is attached to a threaded spring post  266  and locked with nut  267 . The opposite end passes through a clearance hole in spring post  268  and through lower support angle  261 .  
         [0067]    The pre-load adjustment nut  265  works against pre-load springs  259  to maintain a predetermined distance between upper support angle  260  and lower support angle  261 . The pre-load adjustment nut  265  has a tapered surface which makes contact with a pre-load sense switch that indicates nut  265  is seated against lower support angle  261 . During the interleaf lift cycle, the force of the pre-load spring  265  will be exceeded causing upper support angle  260  and bearing block  263  to move toward opposing bearing block  262 . This movement causes pre-load nut  265  to move away from lower angle  261 . This small movement causes switch  269  to change state deactivating pre-load drive motor  270  which stops drive belt  271  and pulleys  272 . This small is illustrated on FIG. 31 wherein detail “C” shows switch  269  in a normally open condition on tapered surface of adjustment nut  265  which indicates no pre-load sensed and detail “D” shows switch  269  off taper of adjustment nut  265  in a normally closed condition which indicates a pre-load is sensed. Detail “D” also shows the gap  273  within which the pre-load switch  269  operates. Section E-E of FIG. 32 is a bottom view of the pulleys  272  and drive belt  271  that drive lead screw  271 A with attached lead screw nut  271 B. Lifting of lifter pad  248  by lead screw  271 A is achieved through the drive belt  271  and pulleys  272 . Lead screw  271 A is supported by two angular contact bearings  273  and retained through a mounting block  274  via a bearing take up nut  275 . On activation of pre-load drive motor  270 , lead screw  271 A through drive belt  271  and pulleys  272  and motor  270  cause the nut  275  to move up/down depending on state of switch  269 . Lower stroke limit sensor  276  and upper stroke limit sensor  277  control and limit the extent of interleaf lift travel  278 .  
         [0068]    Stroke limit sensors are triggered when the sensor flag  279  interrupts a light beam. This is illustrated in FIG. 30A with the flag  279  shown at the lower stroke limit position. Section E-E of FIG. 32 shows a view of flag  279  passing through the sensor. During the upward cycle of raising and pre-loading interleafs, the pre-load switch  269  is activated and motor  270  stops until enough interleaf sheets have been stripped from the stack to reactivate switch  269  and turn on motor  270 . This sequence repeats until the upper stroke limit sensor  277  is blocked by flag  279 . When this upper limit has been reached and switch  269  activates indicating no more pre-load is present, the motor is reversed until the sensor flag  279  returns to the starting lower limit stroke  276  position.  
         [0069]    Having positioned the interleaf stack for releasing single interleaf discs into the shipping container J, pre-load switch  269  activates pre-load drive motor  270  thereby causing lifter pad  248  to move upward through opening in the interleaf holder  240  to engage metal disc  280 . The interleaf stack is forced against and stopped by the peel blade  251  and back edge retainer  250 . Pre-load switch  269  now removes power from pre-load drive motor  270  readying interleafs for stripping one at a time while incremental pressure is maintained on the stack. Interleaf disc separation begins by activating separator motor  281  that drives the buckle/feed tire in a counter clockwise rotation pulling the front portion of the top interleaf to be pulled backwards from under peel blade  251  and causing the front portion of the top interleaf disc to bow or buckle upward  283  making contact with a light weight buckle paddle  284  pivoting it upward around its pivot point thereby activating sensor  285  mounted in housing  287  confirming interleaf has been released from under peel blade  251 . Adjustment of sensor  285  can allow more or less buckling to occur. View G-G of FIG. 35 is an isometric more clearly showing sensor  285  and buckle paddle  284 . Having released the top interleaf from under peel blade  251 , power to separator motor  281  is reversed causing buckle/feed tire to rotate clockwise pushing the interleaf forward and up over knife edge of peel blade  251  and under interleaf deflector  290  that guides the interleaf towards the queue and release station  292  and idler wheel  292 A as shown in FIGS. 36 and 37. When the front edge of the interleaf is detected by queue sensor  293  causing power to separator motor  281  to be turned off releasing the back portion of the interleaf so that the interleaf may continue its forward progress. FIG. 37 illustrates the relationship.  
         [0070]    The last part of the sequence is the release of the interleaf to the shipping container. First, a fan in fan enclosure  298  underneath the air chute  244  is turned on to provide an air cushion underneath the interleaf. The interleaf release/stage wheel  295  is reactivated releasing the interleaf and causing the interleaf to float down the inclined air cushion chute  244  surface toward a shipping container. The funnel ring  296  is tapered upward to form a funnel-like entrance to the shipping container to provide more clearance for the interleaf to enter. Three emitter/detector pairs  297  on the funnel ring form a light curtain sensing the passage of an interleaf. When any of the sensor pairs  297  detects an interleaf, the interleaf release/stage wheel  295  is turned off. These sensors  297  continue to be monitored until all sensors are unblocked indicating the interleaf has passed through into the shipping container. FIG. 38 is a cutaway view taken along line G-G of FIG. 37 showing the progress of an interleaf as it passes from the queue and release station  292  down air cushion chute  244  and into a shipping container. This sequence continues all interleafs are interspersed between wafers.  
         [0071]    In a second embodiment, the vacuum pickup cup incorporates novel features of construction and arrangement to obviate potential non-alignment issues. The potential for both the wafer pickup surface and cup pickup surface being out of parallel is a normal condition. Though this parallel alignment error may not be large, it can be enough to prevent vacuum to be pulled. Referring now to FIG. 18, the pickup cup generally designated  310  consists of a threaded support post  311  which extends downwardly to the rigid pickup cup  312  where if flanges out as at  311 A to form one side of an electrical contact  313 . The flanged out section  311 A has a hollow bore to allow a press fit of rigid cup  312 . A port  314  through the center of support post  311  allows a vacuum to be pulled through rigid cup  312  and the small holes  315  that feed a pattern of circular grooves  316  which provide sufficient area to securely hold the wafer W during transport from the cassette C to the shipping containers J.  
         [0072]    A floating cup ring  321  surrounds and slips over rigid cup  312  and has a recess in the upper surface of the flange to secure the upper contact  317 . Lead wire  317 A is soldered to contact  317  and terminates in and is attached with connector mount  317 C a two-pin connector  317 A and locked to threaded post  311  with lock nut  319 . Upper contact  317 , therefore, forms a normally closed switch. To prevent floating cup  321  from rotating and severing contact wire  317 D, an anti-rotate pin  318  is provided eliminating rotation between parts. To assure anti-rotate pin  318  cannot dislodge, a plastic stroke limiter sleeve  320  is positioned above and returned via a press fit onto support post  311 . The floating cup ring  321  has a periphery extending outer depending flange  316 A which projects a predetermined distance D below a plane P-P through the bottom face  312 A of cup ring when the cup ring  316  is fully seated as shown in FIG. 18. Accordingly, when the vacuum assembly  310  is positioned to pick up a wafer W, the flange  316 A first engages the wafer surface and is displaced relative to the cup  321 . The contacts are opened to initiate activation of the vacuum.