Abstract:
The invention has an object to provide a foreign substance removing device that is capable of quickly and efficiently cleaning substrate surfaces regardless of the size thereof and preventing readhesion of once removed foreign substances as well as to provide a die bonder equipped with the same. 
     The foreign substance removing device of the invention includes: a pickup device to which a dicing film carrying dies thereon is fixed; and a collet for picking up a die separated from the dicing film and placing the die on a substrate having an adhesive applied thereon, and operates to remove foreign substances on the substrate in preparation for application of the adhesive onto the substrate. The foreign substance removing device includes a cleaning nozzle integrating an air outlet orifice and an air inlet orifice.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a foreign substance removing device and a die bonder equipped with the same. 
     2. Description of the Related Art 
     The die bonder is an apparatus which bonds a die (silicon wafer chip integrating electric circuits) to a lead frame, substrate or the like (hereinafter, referred to as “substrate”) using solder, gold plate or resin as a bonding material. An engineering plastic is used as a die bond material (paste, film) for bonding the die and the substrate together. After positioning, the die is bonded to the lead frame or the like. A method of implementing bonding by using a resin as the bonding material is now predominant. 
     In semiconductor die bonding, solder or resin paste for die bonding (Ag epoxy and Ag polyimide) is used as an adhesive for fixing a semiconductor chip (IC, LSI) to the lead frame, ceramic case, substrate or the like. 
     Dusts on a substrate surface lower the bonding force of an adhesive. It is therefore quite important in die mounting to remove the dusts (hereinafter, referred to as “foreign substances”) from the substrate before bonding the die onto the substrate. In addition, foreign particles of sizes in the range of 5 to 10 μm also cause voids in the adhesive. 
     Accordingly, a common practice in a die bonding operation is to perform cleaning with air flow. Such cleaning techniques known in the art are set forth in the following patent documents. 
     JP-A No. 2002-50655, for example, discloses an arrangement wherein plural types of cleaning devices are arranged along a transport path for horizontally transporting the substrate so that the substrate being transported is subjected to cleaning before chips are mounted thereon. 
     JP-A No. 2002-186923 discloses an arrangement wherein the foreign substances adhered to the substrate surface is vacuumed off by a dust collector. 
     JP-A No. 2000-5715 discloses an apparatus wherein a dust removing device integrating an air outlet chamber and an air inlet chamber is disposed in a moving direction of a work piece. 
     JP-A No. 2007-115979 discloses an arrangement wherein the foreign substances adhered to a surface of a wafer ring carrying a chip array thereon are removed by blasting an ionized gas followed by sucking. 
     As described in the above patent documents, the removal of the foreign substances on the substrate surface is generally accomplished by a method wherein the foreign substances are blown off by applying an air flow and the blown foreign substances are collected by air suction. Unfortunately, however, all these patent documents adopt a stationary system of foreign substance removal, which comes short of ensuring an efficient foreign-substance removal across the full width of substrate and preventing the readhesion of once removed foreign substances. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a foreign substance removing device that is adapted for quick and efficient cleaning of the substrate surface regardless of the size thereof and for prevention of readhesion of once removed foreign substances, as well as a die bonder equipped with the same. 
     According to a first aspect of the invention for achieving the above object, a foreign substance removing device comprises: a pickup device to which a dicing film carrying dies thereon is fixed; a collet for picking up a die separated from the dicing film and placing the die on a substrate having an adhesive applied thereon; and a cleaning nozzle integrating an air outlet orifice and an air inlet orifice and applying air flow for removal of foreign substances on the substrate before the die is bonded onto the substrate. 
     According to the first aspect and another aspect of the invention for achieving the above object, it is preferred that the cleaning nozzle includes a plurality of air outlet orifices formed in an elliptical form and a plurality of air inlet orifices formed in an elliptical arrangement to surround the air outlet orifices. 
     According to the first aspect and another aspect of the invention for achieving the above object, it is preferred that the cleaning nozzle is elongated in a moving direction of the substrate and moved in a direction perpendicular to the moving direction of the substrate. 
     According to the first aspect and another aspect of the invention for achieving the above object, it is preferred that the cleaning nozzle is elongated in a direction perpendicular to a moving direction of the substrate and moved in the direction perpendicular to the moving direction of the substrate and that the two cleaning nozzles are provided. 
     According to the first aspect and another aspect of the invention for achieving the above object, it is preferred that the cleaning nozzles are arranged in a staggered form. 
     According to the first aspect and another aspect of the invention for achieving the above object, it is preferred that the cleaning nozzle rotates about a longitudinal end thereof in a direction perpendicular to a moving direction of the substrate. 
     According to the first aspect and another aspect of the invention for achieving the above object, it is preferred that the plural cleaning nozzles are arranged in a direction perpendicular to a moving direction of the substrate. 
     According to the first aspect and another aspect of the invention for achieving the above object, it is preferred that the cleaning nozzle periodically performs air blasting and air sucking. 
     The invention can provide a die bonder and a foreign substance removing device that are adapted for quick and efficient cleaning of the substrate surface regardless of the size thereof and for prevention of readhesion of once removed foreign substances. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a conceptual diagram of a die bonder as seen from above; 
         FIG. 2  is an external perspective view showing a pickup device mounted in the die bonder of  FIG. 1 ; 
         FIG. 3  is a schematic diagram showing a structure of a cleaning nozzle according to a first embodiment of the invention; 
         FIG. 4  is a diagram showing movement and configuration of an air nozzle of the cleaning nozzle according to the first embodiment; 
         FIG. 5  is a schematic diagram showing a structure of a cleaning nozzle according to a second embodiment of the invention; 
         FIG. 6  is a schematic diagram showing a structure of a cleaning nozzle according to a third embodiment of the invention; 
         FIG. 7  is a schematic diagram showing a structure of a cleaning nozzle according to a fourth embodiment of the invention; and 
         FIG. 8  is a schematic diagram showing a structure of a cleaning nozzle according to a fifth embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A nozzle which ejects air for removal of foreign substances on the substrate may have a configuration wherein a circular air outlet orifice is formed at the center and is surrounded by an air inlet orifice in the form of a ring. 
     Such a nozzle can suck in dust particles at once before the dust particles are stirred up by the air flow. It is therefore ensured that the once removed dust particles are prevented from adhering again onto the substrate. 
     On the other hand, the substrate to receive the die does not always have a constant width. Since the die bonder bonds dies to substrates of different widths, the cleaning operation need to deal with the substrates having various widths. 
     Therefore in a case where the cleaning nozzle has the circular air outlet orifice and the ring-like air inlet orifice, as described above, the nozzle must move over a longer distance to clean the substrate having a maximum width. This results in increased cleaning time. 
     After various studies on the configuration and operation mode of the cleaning nozzle that can deal with the various substrate widths, the present inventors have accomplished the following embodiments. 
     Referring to  FIG. 1  and  FIG. 2 , an embodiment of a die bonder is described as below. 
       FIG. 1  is a conceptual diagram of the die bonder as seen from above. 
     Referring to  FIG. 1 , the die bonder principally includes a wafer feeder  1 , a work-piece feeding/transporting portion  2  and a die bonding portion  3 . The wafer feeder  1  includes a wafer cassette lifter  11  and a pickup device  12 . The wafer cassette lifter  11  includes a wafer cassette loaded with wafer rings (not shown) for sequentially feeding the wafer rings to the pickup device  12 . The pickup device  12  is adapted to move the wafer ring for picking up a desired die from the wafer ring. 
     The work-piece feeding/transporting portion  2  includes a stack loader  21 , a frame feeder (not shown) and an unloader  23 . The stack loader  21  transports a substrate (not shown) to receive a die in a direction of an arrow A in the figure by means of substrate guides  22   a ,  22   b . The substrate guides  22   a ,  22   b  transports the substrate to the unloader  23  via two processing positions on the frame feeder  22 . The unloader  23  defines a portion to store the delivered substrates. A cleaning nozzle (foreign substance removing device)  5  is installed at place above the substrate guides  22   a ,  22   b  and the substrate transported. The die bonding portion  3  includes a preform portion (die paste applicator)  31  and a bonding head portion  32 . 
       FIG. 2  is an external perspective view showing the pickup device mounted in the die bonder. 
     Referring to  FIG. 2 , the pickup device  12  includes: an expand ring  15  for retaining a wafer ring  14 , and a support ring (not shown) for horizontally positioning a dicing tape  16  retained by the wafer ring  14  and having a plurality of dies (chips)  4  adherent thereto. A plurality of formed dies  4  are extracted one by one by means of the preform portion  31  and bonded to a surface of the substrate with an adhesive applied thereto, the substrate transported by means of the substrate guides  22   a ,  22   b  shown in  FIG. 1 . 
     A detailed description is made as below on the cleaning nozzle  5  of the invention. 
     First Embodiment 
       FIG. 3  is a schematic diagram showing a structure of a cleaning nozzle according to a first embodiment of the invention. 
       FIG. 4  is a diagram showing movement and configuration of a cleaning nozzle of the cleaning nozzle according to the first embodiment. 
     Referring to  FIG. 3  and  FIG. 4 , a substrate  10  supported in grooves of the substrate guides  22   a ,  22   b  is transported in a backward direction as seen on the drawing surface (shown in  FIG. 3 ). The cleaning nozzle  5  is provided with an air feed pipe  5   a  and an air discharge pipe  5   b . As shown in  FIG. 3 , the air discharge pipe  5   b  has a larger diameter than the air feed pipe  5   a . This is because the air discharge pipe  5   b  also serves to transport the foreign substances. As shown in  FIG. 4 , a nozzle face  5   c  is closest to a surface of the substrate  10 . 
     As shown in  FIG. 4 , the nozzle face  5   a  is centrally formed with a plurality of air outlet orifices  5   d . The nozzle face is also formed with a plurality of air inlet orifices  5   e  around the air outlet orifices  5   d.    
     Thus, the foreign substances blown away by the air ejected from the air outlet orifices  5   d  are immediately sucked into the air inlet orifices  5   e , as indicated by arrows in  FIG. 3 , and are finally discarded. 
     The cleaning nozzle  5  moves up and down as indicated by an arrow B in  FIG. 3 . Indicated at  51  is the cleaning nozzle that stops at an upper position. The cleaning nozzle  5  is normally lowered to a proper position (e.g., 2 mm above the substrate) above the substrate  10 . When the substrate  10  is moved or replaced, the cleaning nozzle is moved up. As indicated by an arrow C in  FIG. 3 , the cleaning nozzle  5  performs an operation of removing the foreign substances as moved in a width direction of the substrate  10 . Indicated at  52  is the cleaning nozzle moved in the width direction. 
     In this embodiment, the rectangular cleaning nozzle  5  is moved in a direction perpendicular to a moving direction of the substrate  10 , while the rectangular cleaning nozzle  5  orients the long side thereof in the same direction as the moving direction of the substrate. 
     In this embodiment, the width of the nozzle face  5   c  of the cleaning nozzle  5  is set to a required value according to a cleaning process time (required throughput). This provides for the setting of a desired amount of movement of the cleaning nozzle  5  according to the width of the substrate  10 . Therefore, the cleaning according to the embodiment can deal with the substrates having various widths. In addition, the cleaning according to the embodiment can be carried out under an optimum cleaning condition that an optimum distance is maintained between the substrate  10  and the cleaning nozzle  5  while preventing failure caused by contact between the substrate being transported and the nozzle. 
     According to the embodiment, the nozzle face  5   c  of the cleaning nozzle  5  has the rectangular shape thereby providing an increased width for foreign substance cleaning and hence, cleaning efficiency can be notably increased through cleaning time reduction. 
     Second Embodiment 
       FIG. 5  is a diagram showing an exemplary cleaning nozzle layout according to a second embodiment of the invention. 
     Referring to  FIG. 5 , two cleaning nozzles  53 ,  54  are arranged in parallel in the direction perpendicular to the moving direction of the substrate  10 . In this embodiment, the cleaning nozzles  53 ,  54  are supported by the substrate guides  22   a ,  22   b . The two cleaning nozzles  53 ,  54  have the long sides directed in the direction perpendicular to the moving direction of the substrate. Furthermore, the two cleaning nozzles  53 ,  54  are adapted to operate in the direction of the long side. 
     According to the embodiment, cleaning in X-direction and cleaning in Y-direction shown in  FIG. 1  are simultaneously accomplished by moving the substrate  10 . 
     Third Embodiment 
       FIG. 6  is a diagram showing an exemplary cleaning nozzle layout according to a third embodiment of the invention. 
     Referring to  FIG. 6 , three cleaning nozzles  55 ,  56 ,  57  according to the embodiment are arranged in parallel in the direction perpendicular to the moving direction of the substrate  10  and in staggered relation. Similarly to the second embodiment, the three cleaning nozzles  55 ,  56 ,  57  have the long sides oriented in the direction perpendicular to the moving direction of the substrate. The central cleaning nozzle  57  is fixed to place while the cleaning nozzles  55 ,  56  on either side are adapted to operate in the direction of the long sides thereof just as in the second embodiment. 
     Thus, the embodiment permits the cleaning nozzle  57 , which is not provided with an operating mechanism, to follow the operations of the cleaning nozzles  55 ,  56  with respect to the width of the substrate, also offering cost advantage. Further, the substrate  10  is subjected to the cleaning while passed under the cleaning nozzles  55 ,  56 ,  57 . Therefore, the cleaning process time cannot be a causal factor of lowering the throughput. 
     Fourth Embodiment 
       FIG. 7  is a diagram showing an exemplary cleaning nozzle layout according to a fourth embodiment of the invention. 
     Referring to  FIG. 7 , a cleaning nozzle  58  of this embodiment is adapted to rotate about a fulcrum  58   a  just like an automotive wiper to be positioned as a cleaning nozzle  58 ′ as indicated by a dotted line in the figure. 
     According to the embodiment, the cleaning nozzle  58  having a longitudinal length to cover the width of the substrate  10  can be rotated in a θ direction from a parallel (horizontal) position to a perpendicular position relative to the substrate  10 . Therefore, the cleaning nozzle can deal with substrates having various widths. Further, the cleaning nozzle  58  of the embodiment is adapted for the change of the substrate width simply by mounting a rotation mechanism thereto. Hence, the cleaning device per se can achieve size reduction. This also leads to cost reduction. 
     Fifth Embodiment 
       FIG. 8  is a diagram showing an exemplary cleaning nozzle layout according to a fifth embodiment of the invention. 
     Referring to  FIG. 8 , the embodiment has an arrangement wherein cleaning nozzles  59 ,  60  rotatable about respective fulcrums  59   a ,  60   a  just as in the fourth embodiment are provided in two stages. Indicated at  59 ′ and  60 ′ are cleaning nozzles rotated to respective positions. The substrate guides are movable to places, as indicated by  22   a ′ and  22   b ′, according to the width of the substrate. 
     The embodiment is adapted not only to operate the both cleaning nozzles to deal with the substrate having a large width but also to operate only either the cleaning nozzle  59  or the cleaning nozzle  60  depending upon the width of the delivered substrate. 
     Namely, the cleaning nozzles of this embodiment are flexible to operate with freedom from restriction by the width of the substrate, so as to accomplish any cleaning jobs regardless of the substrate width. 
     Sixth Embodiment 
     According to the embodiment, illustration of which is omitted, the cleaning nozzle is adapted to apply pulsed air in order to further enhance the foreign substance removing effect of the cleaning nozzles of the first to sixth embodiments described above. 
     According to the embodiment, the foreign substances firmly adhered to the substrate surface can be forcibly removed by dynamically and periodically repeating air blasting and air sucking. The embodiment can achieve improvement in foreign substance removal ability. 
     The following modifications may be made to the first to sixth embodiments. 
     A distance sensor may be mounted to a tip of the cleaning nozzle  5  for the purpose of protecting the substrate and the dies  4  previously bonded thereto for lamination. A distance to the substrate or the surface of the laminated dies can be measured by means of the distance sensor and hence, determination can be made as to whether the cleaning nozzle is deviated from a proper distance or not. Measure for creating an alarm in response to the deviation from the proper distance may also be provided. Alternatively, an interlock function may be provided such as to deactivate the die bonder in response to the deviation from the proper distance. There may also be provided a control function that responds to the distance sensor to control the cleaning nozzle  5  to maintain the proper distance from the substrate or the surface of the laminated dies. 
     This system can prevent the substrate or substrate product carrying the dies from suffering failure caused by contact with the nozzle and can also ensure the proper foreign substance removal ability even if the substrate is deformed or the substrate or the nozzle is displaced due to physical effect. 
     In order to stabilize the foreign substance removal ability and to obviate failure resulting from decrease in the foreign substance removal ability, a flow sensor or pressure sensor may also be employed for detecting a flow rate of air from the cleaning nozzle  5  and a suction flow rate of air into the inlet orifices. An alarm is created in response to deviation from a proper flow rate. Alternatively, an interlock function may be provided such as to deactivate the die bonder in response to the deviation from the proper flow rate. There may also be provided a function to maintain a constant flow rate by detecting the flow rate by means of the flow sensor or pressure sensor. 
     This system can prevent the decrease in the foreign substance removal ability which results from abnormal air flow rate or suction flow rate, or can prevent the substrate or substrate product carrying the dies from being damaged due to excessive flow rate. Furthermore, the system can also maintain the proper foreign substance removal ability. 
     While the invention has been described with reference to the specific embodiments thereof, it is to be understood from the above description that equivalents, changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such equivalents, changes and modifications depart from the scope of the present invention, they should be construed as being included therein.