Patent Publication Number: US-2013248114-A1

Title: Chip bonding apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 2012-0029299, filed on Mar. 22, 2012 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to semiconductor devices. 
     2. Description of the Related Art 
     Wire bonding methods typically use metal wires made of fine gold or aluminum to connect and bond Integrated Circuit (IC) chips to circuit boards. These methods allow metal pads serving as input/output terminals to be formed only at edges of IC chips. Therefore, implementing these methods may be difficult when the number of input/output terminals increases and distances between the terminals decrease due to higher density of IC chips. Additionally, deterioration of electric properties may occur due to generation of noise in bonded wires as a signal frequency increases. Instead of wire bonding methods, flip-chip bonding methods have been used in which solder bumps are formed at a rear surface of an IC chip and are fused to a circuit board via reflow to bond the IC chip to the circuit board. 
     In some flip-chip bonding methods, after an IC chip having solder bumps is aligned with a metal pad on a circuit board, both the IC chip and the circuit board are heated above a melting point of the solder bumps. The heating may be performed by infrared heating, convection heating, or the like, for the purpose of bonding the solder bumps of the IC chip to the metal pad of the circuit board via reflow, i.e. melting of the solder bumps. 
     However, bonding methods using infrared or convection heating may cause damage to polymer circuit boards because they are heated with the IC chip to a temperature in a range of 200° C.-300° C. for reflow of the solder bumps. 
     A different type of flip-chip bonding method using inductive heating may be adopted because they rapidly and selectively raise a temperature of a board within a short time and, thus, may prevent deterioration of IC chips and circuit boards and reduce process time. 
     In the case of the flip-chip bonding methods using inductive heating, in consideration of the fact that a temperature of a board rapidly increases within a short time, a vacuum generation device may be used to fix a board to a stage in order to prevent deformation of the board due to rapid temperature change. 
     Such a vacuum generation device is typically installed separately from and is connected to the stage using a connection pipe through which fluid flows. If a large capacity of compressed air is supplied to the vacuum generation device, vacuum is generated between the stage and the circuit board via the connection pipe, whereby the circuit board is fixed to the stage. 
     However, in the above-described configuration, an additional facility to supply a large capacity of compressed air to the vacuum generation device may be used and an additional space for installation of the vacuum generation device may be required. Further, loss of vacuum in the connection pipe between the stage and the vacuum generation device may result in poor vacuum generation efficiency. 
     SUMMARY 
     One or more embodiments described herein correspond to a chip bonding apparatus which may efficiently fix a circuit board to a stage by generating vacuum between the circuit board and the stage. 
     In accordance with one embodiment, a chip bonding apparatus includes at least one stage unit to support a circuit board having a chip placed thereon, and a bonding unit coupled to the stage unit to define a chamber, the bonding unit including an inductive heating antenna to generate a high frequency within the chamber to bond the chip to the circuit board, wherein the stage unit includes a vacuum generator to generate vacuum between the stage unit and the circuit board to fix the circuit board onto the stage unit upon bonding of the chip to the circuit board. 
     The stage unit may include at least one stage to support the circuit board seated thereon, a base arranged below the stage to support the stage, at least one fluid supply pipe to supply a fluid into the stage, and at least one fluid discharge pipe to discharge the fluid supplied into the stage, and the vacuum generator may be inserted in the stage. 
     The stage may include a plurality of absorption holes formed in an upper surface thereof, on which the circuit board is seated, for vacuum absorption of the circuit board, a first flow-path communicating with the fluid supply pipe, and a second flow-path communicating with the fluid discharge pipe. 
     The vacuum generator may include a fluid suction portion communicating with the first flow-path, through which the fluid is suctioned so as to be supplied to the first flow-path, a fluid discharge portion communicating with the second flow-path, through which the fluid suctioned through the fluid suction portion is discharged, a connecting portion to connect the fluid suction portion and the fluid discharge portion to each other, and a guide portion communicating with the absorption holes and the connecting portion, the guide portion serving to guide the fluid introduced through the absorption holes to the connecting portion by a pressure difference generated as the fluid suctioned through the fluid suction portion flows to the fluid discharge portion. 
     The stage may further include a third flow-path communicating with the absorption holes and the guide portion. 
     The chip bonding apparatus may further include a fluid circulation pipe communicating with the fluid discharge pipe and the interior of the chamber to supply the fluid discharged through the fluid discharge portion into the chamber. The fluid may be nitrogen (N2) gas. 
     In accordance with another embodiment, a chip bonding apparatus includes a chamber, the interior of which is hermetically sealed, at least one stage arranged within the chamber and configured to support a circuit board having a chip placed thereon, an inductive heating antenna arranged above the stage and serving to generate a high frequency within the chamber to bond the chip to the circuit board, and a vacuum generator coupled to the stage and serving to generate a vacuum between the stage and circuit board to fix the circuit board on the stage. 
     The stage may include an absorber panel to support the circuit board seated thereon and having a plurality of absorption holes for vacuum absorption of the circuit board, and a flow-path defining panel coupled to a lower surface of the absorber panel to define a flow-path communicating with the absorption holes. 
     The vacuum generator may be provided in the flow-path defining panel and communicates with the absorption holes and the flow-path. 
     The chip bonding apparatus may further include a fluid circulation pipe to supply the gas used for generation of vacuum in the vacuum generator into the chamber. 
     In accordance with another embodiment, a chip bonding apparatus includes at least one stage unit configured to support a circuit board having a chip thereon and a bonding unit coupled to the stage unit to define a chamber, the bonding unit including at least one inductive heater configured to heat to bond the chip to the circuit board, and the stage unit including a vacuum generator configured to generate a vacuum between the stage unit and the circuit board to hold the circuit board onto the stage unit during bonding of the chip to the circuit board. 
     The stage unit may include at least one stage to support the circuit board thereon, a base arranged below the stage to support the stage, at least one fluid supply pipe to supply a fluid into the stage, and at least one fluid discharge pipe to discharge the fluid supplied into the stage, wherein the vacuum generator is in the stage. 
     The stage may include an upper surface including a plurality of absorption holes, the circuit board overlaps the plurality of absorption holes, a first flow-path communicates with the at least one fluid supply pipe, and a second flow-path communicates with the at least one fluid discharge pipe. 
     The vacuum generator may include a fluid suction portion communicating with the first flow-path, through which the fluid is suctioned so as to be supplied to the first flow-path; a fluid discharge portion communicating with the second flow-path, through which the fluid suctioned through the fluid suction portion is discharged; a connecting portion to connect the fluid suction portion and the fluid discharge portion to each other; and a guide portion communicating with the absorption holes and the connecting portion, the guide portion serving to guide the fluid introduced through the absorption holes to the connecting portion by a pressure difference generated as the fluid suctioned through the fluid suction portion flows to the fluid discharge portion. The stage may also include a third flow-path communicating with the absorption holes and the guide portion. 
     The apparatus may include a fluid circulation pipe communicating with the fluid discharge pipe and the interior of the chamber to supply the fluid discharged through the fluid discharge portion into the chamber. The fluid includes nitrogen (N 2 ) gas. 
     In accordance with another embodiment, a processing apparatus comprises a stage to support an object and a vacuum generator in the stage, the stage including a plurality of first holes coupled to the vacuum generator and a plurality of second holes adjacent the first holes and configured to receive a gas, a first pressure applied through the first holes to hold the object and a second pressure applied through the second holes to receive the gas during a time when the first pressure is not applied through the first holes. 
     The apparatus may include an inductive heater configured to heat the object when held by the first pressure on the stage, and a spacer to separate the inductive heater and stage by a distance. The spacer may be made of a material which does not exhibit eddy current when a field is applied. 
     Additionally, the first holes are at a first location which overlaps the object and the second holes are at a second location which does not overlap the object. The first holes may be between at least two of the second holes. Also, a section of the stage that includes the first holes may be made from a material that dissipates heat at a faster rate than a material from which the object is made. 
     In accordance with another embodiment, chip bonding apparatus comprises a chamber; a stage configured to support a circuit board having a chip thereon, the stage located in the chamber; an inductive heater configured to generate heat to bond the chip to the circuit board; and a vacuum generator coupled to the stage and configured to generate a vacuum between the stage and the circuit board to hold the circuit board on the stage. The vacuum generator may be located in or coupled to the stage. When coupled to the stage, a vacuum source for the vacuum generator may located inside or outside the chamber. 
     The stage may include an absorber to support the circuit board, the absorber including a plurality of holes transfer the vacuum absorption to the circuit board; and a flow-path between the vacuum generator and the holes in the absorber. Also, a fluid circulation pipe may be included to supply a gas used for generation of the vacuum in the chamber. The gas may include a nitrogen (N 2 ) gas or another processing gas. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of example embodiments will become more apparent by describing in detail example embodiments with reference to the attached drawings. The accompanying drawings are intended to depict example embodiments and should not be interpreted to limit the intended scope of the claims. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. 
         FIG. 1  shows one embodiment of a chip and circuit board. 
         FIG. 2  shows one embodiment of a chip bonding apparatus. 
         FIG. 3  shows a front view of the chip bonding apparatus. 
         FIGS. 4 and 5  show examples of a stage unit in this apparatus. 
         FIG. 6  shows an example of a bonding unit. 
         FIG. 7  shows an inductive heating antenna in the bonding unit. 
         FIG. 8  shows an interior arrangement of a chamber. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Detailed example embodiments are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. Example embodiments may, however, be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein. 
     Accordingly, while example embodiments are capable of various modifications and alternative forms, embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments to the particular forms disclosed, but to the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of example embodiments. Like numbers refer to like elements throughout the description of the figures. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it may be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (eg., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.). 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved. 
       FIG. 1  shows one embodiment of a flip chip  20  and a circuit board  10 . The flip chip  20  includes a die  21  which, for example, may be in the form of a flat plate and a plurality of solder bumps  22  protruding from one surface of the die  21  to mount the die  21  to a circuit board  10 . 
       FIG. 2  shows one embodiment of a chip bonding apparatus, and  FIG. 3  shows a top view of the chip bonding apparatus. As illustrated in  FIGS. 2 and 3 , the chip bonding apparatus, designated by reference numeral  1 , includes a transfer unit  30 , a stage unit  70 , a loading unit  40 , a bonding unit  50 , an unloading unit  60 , a cooling unit  90 , and a rotating unit  81 . 
     The transfer unit  30  transfers the circuit board  10  having the flip chip  20  placed thereon to a bonding unit  50  and also discharges the completely bonded circuit board  10  to an external location. 
     The stage unit  70  has a stage onto which the circuit board  10  having the flip chip  20  placed thereon is loaded. 
     The loading unit  40  holds the circuit board  10  transferred via the transfer unit  30  and thereafter loads the circuit board  10  on the stage unit  70 . 
     The bonding unit  50  bonds the flip chip  20  to the circuit board  10 . 
     The unloading unit  60  separates the completely bonded circuit board  10  from stage unit  70  and delivers the circuit board  10  to the transfer unit  30  that discharges the circuit board  10  to an external location. 
     The cooling unit  90  reduces a temperature of heated stage unit  70 . 
     The rotating unit  81  rotates stage unit  70  by a predetermined angle. 
     Operation of the transfer unit  30  will now be explained in greater detail. In accordance with one embodiment, the transfer unit  30  includes a conveyor  31  to transfer the circuit board  10  having the flip chip  20  placed thereon, and a motor (not shown) to move the conveyor  31  leftward or rightward. The loading unit  40  may include a plurality of holders  41  arranged in parallel to hold the circuit board  10  delivered from the transfer unit  30 . 
     Once the circuit board  10  having the flip chip  20  placed thereon has been placed on the conveyor  31 , the conveyor  31  is driven to deliver the circuit board  10  to one of the plurality of holders  41  of the loading unit  40 . After the circuit board  10  is delivered to one of the plurality of holders  41  arranged in parallel, the transfer unit  30  moves the conveyor  31  to deliver another circuit board  10  to the next holder  41 . 
     Once the circuit boards  10  have been delivered to all the holders  41  of the loading unit  40  and the stage unit  70  onto which the circuit boards  10  will be loaded has been moved to a position corresponding to the loading unit  40 , the holders  41  of the loading unit  40  place the circuit boards  10  on the stage unit  70 . 
     Additionally, the transfer unit  30  may be divided into a supply unit to deliver the circuit board  10  having the flip chip  20  placed thereon to the loading unit  40  via the conveyor  31  as described above and a discharge unit to discharge the completely bonded circuit board  10 . The discharge unit may discharge the circuit board  10  to an external location from the bonding apparatus via operation of the conveyor  31 , once the completely bonded circuit board  10  has been placed on the conveyor  31  by the unloading unit  60 . 
     Instead of conveyor  31 , the transfer unit may use another transfer device to supply the circuit board  10  to the bonding apparatus and to discharge the completely bonded circuit board  10  from the bonding apparatus for progress of a next process. 
       FIGS. 4 and 5  show an embodiment of stage unit  70  of the chip bonding apparatus, on which stage unit is loaded circuit board  10  by the loading unit  40 . In this embodiment, the stage unit  70  includes a plurality of stages  71  on which circuit boards  10  are placed respectively, a base  78  configured to support the plurality of stages  71 , and fluid supply pipes  80   a  and fluid discharge pipes  80   b  to respectively supply or discharge a fluid. 
     Each stage  71  includes an absorber panel  72  configured to support the circuit board  10  placed thereon, a flow-path defining panel  73  configured to support the absorber panel  72  and having a variety of flow-paths, and a thermally insulating panel  74  to prevent heat transfer. 
     A plurality of absorption holes  76  and exhaust holes  76   a  are formed in a surface of the absorber panel  72 . The absorption holes  76  are connected to a vacuum generator  100  provided within the stage  71  to perform vacuum chucking. 
     If bonding is performed in a state in which the circuit board  10  is not fixed on the stage  71 , serious deformation of the circuit board  10  may occur due to rapid temperature increase during bonding and even the deformed board may come into contact with an inductive heating antenna  52  of the bonding apparatus, causing generation of arcing. Moreover, local burning of the circuit board  10  may occur and/or flight of the flip chips  20  placed on the circuit board  10  may occur. 
     In accordance with one embodiment, absorption holes  76  are formed in the absorber panel  72  to fix the circuit board  10  to the absorber panel  72  via vacuum absorption, which may prevent, for example, bending of the heated circuit board  10 . The exhaust holes  76   a  suction and exhaust a gas (e.g., nitrogen gas) supplied into a chamber  150  to remove the gas (e.g., nitrogen) from within the chamber atmosphere. 
     The absorption holes  76  may be formed in a central region of the absorber panel  72  on which the circuit board  10  is placed, and the exhaust holes  76   a  may be formed in a rim region of the absorber panel  72 . 
     Meanwhile, the absorber panel  72  may be formed, for example, of Invar as an alloy of nickel (Ni) and iron (Fe), graphite, silicon carbide (SiC), or the like. Heat generated from solder bumps  22  during bonding is rapidly transferred to the relatively cold board that comes into contact with the solder bumps  22 , which may disable electrical connection of contacts. For this reason, the absorber panel  72  may be formed of Invar, graphite, SiC or the like that exhibits excellent heat dissipation and high deformation resistance. 
     The flow-path defining panel  73  is installed to a lower surface of the absorber panel  72  to support the absorber panel  72  and includes flow-paths  77   a ,  77   b  and  77   c  communicating with the plurality of absorption holes  76  of the absorber panel  72  and vacuum generator  100 , as shown, for example, in  FIG. 8 . 
     The thermally insulating panel  74  is installed below a lower surface of the flow-path defining panel  73  to prevent heat generated during bonding from dissipating outward via the stage  71 , thereby preventing deterioration in melting efficiency of the solder bumps  22 . 
     An elastic structure  75  is installed below a lower surface of the stage  71 . The elastic structure  75  is deformed upon receiving external force and is returned to an original shape thereof when the force is removed. The elastic structure  75  may, for example, be a spring. 
     When the stage unit  70  on which the circuit board  10  has been loaded is moved upward to a position spaced apart from the inductive heating antenna  52  of the bonding unit  50  by a certain distance, the stage unit  70  is additionally moved upward to hermetically seal the bonding unit  50 . 
     Through the additional upward movement of the stage unit  70 , the base  78  of the stage unit  70  is closely fitted into a bottom opening of the bonding unit  50  to hermetically seal the bonding unit  50 . Additional upward movement force applied to the stage unit  70  to hermetically seal the bonding unit  50  is transmitted to the elastic structure  75 , causing the elastic structure  75  to be compressed. The stage unit  70  is moved upward in proportion to a compressed degree of the elastic structure  75 . 
     The additional upward movement of the stage unit  70  to hermetically seal the bonding unit  50  is accomplished via compression of the elastic structure  75 , and may have no influence on a constant distance between the inductive heating antenna  52  and the stage  71  that is maintained by a spacer  55  for uniform bonding. 
     The base  78  to support the stage  71  is installed below a lower surface of the stage  71 . The base  78  may be designed to have the same shape and area as the bottom opening of the bonding unit  50 . Thereby, when the stage unit  70  is moved upward, the base  78  of the stage unit  70  may be closely fitted into the bottom opening of the bonding unit  50 . In other embodiments, the base may have a shape and/or area different from the shape and area of the bottom opening of the bonding unit. 
     After the base  78  of the stage unit  70  has closely been fitted into the bottom opening of the bonding unit  50 , the bonding unit  50  is hermetically sealed. An elastic structure  79  may be installed to a lower surface of the base  78  and may perform the same function as the elastic structure  75  installed to the lower surface of the stage  71 . Additionally, the elastic structure  79  may enable upward or downward tilting of the base  78 , which provides some movement margin of the base  78 . 
     The fluid supply pipes  80   a  and the fluid exhaust pipes  80   b  to supply or exhaust a fluid are coupled to the lower surface of the base  78 . The fluid supplied into the stage  71  through the fluid supply pipes  80   a  passes through the vacuum generator  100  and is discharged outward from the chamber ( 150 , see  FIG. 8 ) through the fluid exhaust pipes  80   b.    
     In one embodiment, a plurality of stage units  70  is installed on the rotating unit  81  and is spaced apart from one another. Thereby, the stage units  70  are subjected to predetermined respective processes via rotation of rotating unit  81 . 
     The stage unit  70  may be vertically moved by a vertical drive unit  82  which, for example, may include a transfer screw installed to a lower surface of the rotating unit  81  and a motor. As such, a distance between the circuit board  10  loaded on the stage  71  and the inductive heating antenna  52  of the bonding unit  50  may be adjusted. 
       FIG. 6  shows another view of the bonding unit, and  FIG. 7  shows one arrangement of the inductive heating antenna of the bonding unit. As shown, the bonding unit  50  includes a housing  51  and a plurality of inductive heating antennas  52  arranged within the housing  51 . The bonding unit  50  includes the housing  51  to shield electromagnetic waves, and the housing  51  has an open bottom. 
     When the stage unit  70  is moved upwardly through the open bottom of the housing  51  until the base  78  of the stage unit  70  is closely fitted into the open bottom of the housing  51 , the housing  51  is hermetically sealed to define the chamber  150 . Once the chamber  150  has been defined, the solder bumps  22  of the flip chip  20  are heated to a molten state to bond the flip chip  20  to circuit board  10  by inductive heating using one or more of the inductive heating antennas  52  provided for the chamber  150 . 
     The inductive heating antennas  52  are arranged within the housing  51  to perform inductive heating on the flip chip  20  so as to bond the flip chip  20  to the circuit board  10 . In one embodiment, the inductive heating antennas  52  are mounted to an inner ceiling surface of the housing  51  via support pieces  53 . A plurality of support pieces  53  may be provided to ensure sufficiently stable fixing of the inductive heating antennas  52 . 
     The spacer  55  may be mounted to a lower surface of the inductive heating antenna  52 . The spacer  55  may maintain a constant distance between the stage  71  and the inductive heating antenna  52  when the stage  71  on which the circuit board  10  has been loaded approaches the inductive heating antenna  52  for bonding. 
     The spacer  55  may be formed of a material that does not transmit an eddy current created by a magnetic field around the inductive heating antenna  52  and is not deformed at high temperatures. For example, the spacer  55  may be formed of ceramic or engineering plastic that may endure high temperatures. The spacer  55  may be designed such that a cross-sectional width thereof is equal to a distance between the inductive heating antenna  52  and the circuit board  10  that is required for efficient and uniform bonding of the circuit board  10 . 
     An anti-pollution plate  56  may be mounted to the lower surface of the inductive heating antenna  52 . The anti-pollution plate  56  prevents flux evaporated during bonding from being attached to the inductive heating antenna  52 , thereby preventing pollution of the inductive heating antenna  52 . 
     The inductive heating antenna  52  may further include a plurality of connection terminals  131   a  and  131   b  for connection of a high-frequency power-supply unit  133  and a ground  134 . The connection terminals  131   a  and  131   b  may be cylindrical terminals located at one side of the inductive heating antenna  52 . 
     The high-frequency power-supply unit  133  includes a high-frequency generator to generate high-frequency AC power of 27.12 MHz or 13.56 MHz, and a matcher to match impedances between the high-frequency generator and the inductive heating antenna  52 . 
     The inductive heating antenna  52  may further include cooling water ports  132   a  and  132   b  to cool the inductive heating antenna  52  heated via supply of high-frequency AC power. The cooling water ports  132   a  and  132   b  include inlet and outlet ports connected to cooling lines  57  for supply of cooling water. 
     When high-frequency AC power is applied to the inductive heating antenna  52 , a magnetic field is created around the inductive heating antenna  52 . In this case, if a metal is present near the inductive heating antenna  52 , an eddy current flows through the metal by the created magnetic field and inductive heating of the metal occurs based on the eddy current. 
     Accordingly, when circuit board  10  on which the flip chip  20  is placed is arranged below the inductive heating antenna  52  and high-frequency AC power is applied to the inductive heating antenna  52 , an AC magnetic field is created around the inductive heating antenna  52 . As an eddy current is applied to the solder bumps  22  by the AC magnetic field, the solder bumps  22  are heated by the eddy current and, as a result, the flip chip  20  is attached to the circuit board  10 . 
       FIG. 8  shows one possible arrangement for an interior of the chamber. As shown, the chamber  150  is defined via coupling of the bonding unit  50  and the stage unit  70  and bonding to fix the flip chip  20  to the circuit board  10  is performed. 
     In the chamber, it may be necessary to fix the circuit board  10  to the stage  71  in order to prevent deformation of the circuit board  10 , generation of arcing, and/or flight of the flip chips  20  during the bonding. To this end, the stage unit  70  may be equipped to include the vacuum generator  100  to realize vacuum absorption of the circuit board  10  to the stage  71 , and the flow-paths  77   a ,  77   b  and  77   c  communicating with the vacuum generator  100  and the plurality of absorption holes  76 . 
     The vacuum generator  100  is located within the stage  71  and, more particularly, within the flow-path defining panel  73  constituting the stage  71 . The vacuum generator  10  includes a fluid suction portion  110  for suction of a fluid into the stage  71 , a fluid discharge portion  120  for discharge of the fluid suctioned through the fluid suction portion  110 , a connecting portion  130  between the fluid suction portion  110  and the fluid discharge portion  120 , and a guide portion  140  for communication between the plurality of absorption holes  76  and the connecting portion  130 . 
     The fluid suction portion  110  communicates with the first flow-path  77   a  that will be described hereinafter. As a fluid is suctioned into the fluid suction portion  110  through the fluid supply pipe  80   a  and the first flow-path  77   a , the fluid flows to the connecting portion  130  and the fluid discharge portion  120 . The fluid suction portion  110  may be provided, for example, with a solenoid valve to adjust the flow rate of fluid supplied to the fluid suction portion  110 . 
     The fluid discharge portion  120  discharges not only a fluid suctioned from the fluid suction portion  110  and having passed through the connecting portion  130 , but also air or gas introduced into a gap between circuit board  10  and absorber panel  72  through the guide portion  140 . This air or gas may be introduced through guide portion  140  as a result of negative pressure generated during flow of the fluid through the connecting portion  130 , outwardly from the stage  70 . 
     The connecting portion  130  connects the fluid suction portion  110  and the fluid discharge portion  120  to each other to allow the fluid suctioned through the fluid suction portion  110  to be discharged through the fluid discharge portion  120 . During flow of the suctioned fluid, negative pressure is created in the connecting portion  130  and the air between the circuit board  10  and the absorber panel  72  is introduced into the connecting portion  130  through the plurality of absorption holes  76  and the guide portion  140 . As vacuum is created between the circuit board  10  and the absorber panel  72 , force to absorb and fix the circuit board  10  to the absorber panel  72  is generated. 
     The guide portion  140  guides the air, introduced through the plurality of absorption holes  76  by negative pressure created in the connecting portion  130 , to the connecting portion  130 . 
     The flow-paths  77   a ,  77   b  and  77   c  communicate with the vacuum generator  100  and the plurality of absorption holes  76 . In accordance with one embodiment, flow-path  77   a  is connected between the fluid supply pipe  80   a  and the fluid suction portion  110  to allow a fluid supplied into the stage  71  through the fluid supply pipe  80   a  to be suctioned by the vacuum generator  100 . Flow-path  77   b  is connected between fluid discharge portion  120  and fluid exhaust pipe  80   b  to allow the fluid discharged from the vacuum generator  100  to be discharged outward from the stage  71 . Flow-path  77   c  is connected between the plurality of absorption holes  76  and guide portion  140  to allow air between the circuit board  10  and the absorber panel  72  to be introduced into the vacuum generator  100 . 
     To ensure absorption and fixing of the circuit board  10  to the stage  71 , the fluid supplied to the vacuum generator  100  may be nitrogen (N2) gas to process the solder bumps  22  for connection between the circuit board  10  and the flip chip  20 . In another embodiment, a different gas or fluid may be used. 
     The solder bumps  22  of the flip chip  20  that come into contact with the circuit board  10  may be subjected to chemical treatment using flux. This flux may correspond to a solvent for surface treatment of a metal to prevent a molten metal surface from being oxidized via reaction with the atmosphere. Because adhesion may be difficult if an oxide layer is formed via oxidation of a molten metal surface during bonding of a metal, this flux treatment may be performed to prevent oxidation of the molten metal surface. 
     During this treatment, evaporation of flux may occur during bonding at a high temperature and bonding may fail due to oxidation of the solder bumps  22  that come into contact with the board. To prevent oxidation of the solder bumps  22 , a nitrogen (or other gas) atmosphere may be formed within the chamber  150  to enable flux treatment. 
     The nitrogen gas is suctioned into the vacuum generator  100  through the fluid supply pipe  80   a  and first flow-path  77   a  and then is discharged outwardly from stage  71  through flow-path  77   b  and fluid exhaust pipe  80   b . Thereafter, the fluid is supplied into the chamber  150  through the fluid exhaust pipe  80   a  and a fluid circulation pipe  80   c  which communicate with the chamber  150 . 
     That is, as the nitrogen gas is introduced into the stage  71  and flows through the vacuum generator  100  by suction force of the vacuum generator  100 , the circuit board  10  is fixed to the stage  71 . Thereafter, the fluid is supplied into the chamber  150  through the fluid exhaust pipe  80   b  and fluid circulation pipe  80   c  for flux treatment. Finally, the nitrogen gas used for flux treatment is discharged outward from the chamber  150  through the exhaust holes  76   a.    
     By directly coupling the vacuum generator  100  to the stage  71 , enhanced absorption efficiency is achieved. Further, using nitrogen gas for use in bonding as a fluid to generate suction force in the vacuum generator  100  may eliminate a facility to supply a large capacity of compressed air, which may result in cost reduction and enhanced productivity. 
     The cooling unit  90  cools the stage unit  70  from which all the completely bonded circuit boards  10  have been unloaded. After completion of bonding and cooling, stage  71  of the stage unit  70  from which the circuit board  10  has been removed has a high temperature of approximately 100° C. 
     If the circuit board  10  having the flip chip  20  placed thereon is again loaded above the stage  71  without lowering the temperature of the stage  71  to approximately 60° C. or less, the high temperature of the stage  71  may cause deformation of the circuit board  10 . Therefore, cooling unit  90  to lower the temperature of the stage  71  may be used to lower the temperature of the stage before another circuit board is loaded. 
     In one embodiment, the cooling unit  90  may include a plurality of chambers containing cooling water. The chambers may be designed to have approximately the same shape as that of the stages  71 , and the number of the chambers may be equal to the number of stages  71 . However, the configuration of the cooling unit  90  is not limited to the above description, and the cooling unit  90  may be replaced by any other shapes and configurations so long as they function to cool the stages  71 . A temperature of the cooling water may be, for example, approximately 20° C. 
     The stage unit  70 , from which the circuit board  10  has been unloaded, is moved to a position where the cooling unit  90  is installed via rotation of the rotating unit  81 . The stage unit  70  moved to the installation position of the cooling unit  90  is moved upward to the cooling unit  90  until it comes into contact with the cooling unit  90 . The upward movement of the stage unit  70  stops upon coming into contact with the cooling unit  90 . 
     The stage unit  70  in contact with the cooling unit  90  as described above performs heat exchange with the cooling water of the cooling unit  90 , thereby being cooled. This state is continued until the temperature of the stage unit  70  is lowered to a predetermined temperature or less. 
     The rotating unit  81  includes a rotatable plate on which the stage unit  70  is installed, and a motor to drive the rotatable plate. The rotatable plate may have any one of a number of geometrical shapes including but not limited to a circular or polygonal shape. 
     The plurality of stage units  70  may be installed on the rotating plate. Although the number of the stage units  70  installed on the rotating plate is not limited, it will be appreciated that six stage units  70  may be installed on the rotating plate in one embodiment. The rotating plate may have a plurality of sections, for example, equal in number to the number of the stage units  70  such that the stage units  70  are installed to the respective sections in a one to one ratio. 
     The transfer unit  30 , loading unit  40 , bonding unit  50 , unloading unit  60 , and cooling unit  90  may be installed respectively at predetermined positions on the rotating plate. 
     The rotating unit  81  is rotated by a split angle equivalent to the number of the stage units  70  after a predetermined time for each process has passed. For example, if six stage units  70  are installed, the rotating unit  81  is rotated by 60 degrees at a time. 
     The unloading unit  60  unloads the circuit board  10 , which has been completely bonded in the bonding unit  50  and has been subjected to the cooling process, from the stage unit  70 . The unloading unit  60  may include a pickup member  61  to pickup the circuit board  10  and movable arms that are movable respectively in X-axis, Y-axis and Z-axis to position the pickup member  61  above the circuit board  10  that will be unloaded. 
     The pickup member  61  is rotatably installed to a distal end of the arm that is movable in the Z-axis. That is, the pickup member  61  is positioned above the circuit board  10  to be unloaded via movement of the arms movable on the respective axes. Then, the pickup member  61  is rotated to have a shape coincident with the circuit board  10  to pickup the circuit board  10 . The unloaded circuit board  10  is placed on the conveyor  31  of the discharge unit constituting the transfer unit  30  and is discharged outward from the bonding apparatus via the conveyor  31 . 
     According to one or more embodiments, a vacuum generator is therefore provided which generates vacuum between a stage and a circuit board for using in fixing or otherwise holding and supporting the circuit board to the stage. The circuit board may, therefore, be directly coupled to the stage, which eliminates the use of a connection pipe between the stage and the vacuum generator and prevents possible loss in the connection pipe, resulting in enhanced vacuum generation efficiency. 
     Further, enhanced installation convenience is accomplished because a space for installation of the vacuum generator may be unnecessary. 
     Further, by using a gas during bonding as a fluid to generate vacuum in the vacuum generator, it may be unnecessary for a facility to supply a large capacity of compressed air and cost reduction and enhanced productivity may be accomplished. 
     Example embodiments having thus been described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the intended spirit and scope of example embodiments, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.