APPARATUS AND METHOD FOR MOUNTING COMPONENT

Abstract: A component mounting system includes first to third (pickup, transfer, and placement) stations. A component supplied at the component supply is picked up by a transport head at the pickup station and then transferred to a placement head at the transfer station. The placement head carries the component to the placement station where the component is placed and mounted on a substrate such as circuit board. The component held by the placement head is recognized by an imaging device at or in the vicinity of the transfer station.

Description: DESCRIPTION APPARATUS AND METHOD FOR MOUNTING COMPONENT TECHNICAL FIELD OF THE INVENTION The present invention relates to an apparatus and method for mounting components such as electric devices on a substrate or circuit board. BACKGROUND OF THE INVENTION Generally, a component mounting apparatus has been used widely for a sequential positioning or mounting of electric components on a substrate such as printed circuit board. Fig. 12 shows a conventional component mounting system. The system generally indicated by reference numeral 100 includes a component supply 110 for supplying components; a transport head 120 for picking up one of the components from the component supply 110 and then turning the component upside down to orient the component in a predetermined mounting direction; a placement head 130 for receiving the component from the transport head 120 and then placing the component onto the substrate or printed circuit board in place; an imaging camera 140 for capturing an image of the component received by the placement head 130; a holder 150 for holding and then positioning the circuit board in place in the system 100; another imaging camera 160 for capturing an indication marked on the circuit board; a controller 170 for controlling the whole operation of the system 100. The placement head 130, which is supported to move horizontally in the X-direction in Fig. 12, is equipped with a vacuum nozzle or quill capable of rotating about a vertical Z-axis. Referring to Figs. 13 and 14 operations of the system will be described hereinafter. In the drawing, the component supply 110 is provided with a number of components 111 supported and separated from another on an expanded plate 112. The components 111 are each recognized by an imaging device or camera 113. Based upon the recognition, the controller 170 moves the component supply 110 so that one component Ilia to be mounted in the subsequent mounting is positioned in a predetermined pickup position. The transport head 120 travels to a position right above the component Ilia, moves downward to contact the component Ilia, and then sucks the component 111a for unloading. After unloading, the transport head 120 moves upward and then travels in the X-direction to a transfer station. At the transfer station, the transport head 120 together with the component turns upside down as indicated by arrow 121. This brings the component 111 from an upside-down position into an upright position so that on.: surface (i.e., bottom surface with solder bumps or electrical connections) to be opposed the circuit board is faced downward. The placement head 130 approaches the component Ilia in the upright position from above to receive the component from the transport head 120. Then, the placement head 130 moves upward and then travels in the X-direction toward a placement station. The transport head 120, after being deprived of the component, moves back to the pickup station for the subsequent pickup operation During the operation described above, a circuit board 151 is transported to and then held in position by the holder 150. The imaging device or camera 160 approaches the circuit board 151 to capture the indication defined on the circuit board, indicative of a reference position for the mounting of the component. The captured image is then transmitted to the controller 170. As best Shown in Fig. 13, the imaging device 160 together with another imaging device 140 is mounted on an optical head 180. After the recognition of the indication on the circuit board 151, the optical head 180 moves back in the X-direction toward the placement head 130 that is running in the opposite direction. Once opposed, not only the optical head 180 but also the placement head 130 comes to a halt. In this state, the component Ilia held by the placement head 130 is recognized by the imaging d vic 140. The image captured by the imaging device 140 is transmitted to the controller 170. At this moment, the sucking nozzle of the placement head 130 for sucking and holding the component Ilia is maintained in an elevated position. This prevents the nozzle from making a conflict with the imaging device 140. Also, the sucked component 130 is held within a field of the imaging device 140. After the completion of the recognition, the placement head 130 with the component Ilia restarts travelling in the X-direction again toward the mounting station. During the travel, the recognition results of the component Ilia and the circuit board 151 (in particular, the reference indication) are used for calculations performed in the controller 170. The controller 170 calculates the displacement in the X-direction of the placement head 130 for the mounting of the component Ilia onto the predetermined position of the circuit board 151. Also calculated in the controller 70 are the rotational angle of the nozzle about the Z-axis and the displacement of the circuit board 151. According to the calculation made by the controller 170, the placement head 130 travels in the X-direction to a position where it opposes the circuit board 151. At this moment, the corrections for the nozzle and the circuit board 151 have already been completed. Then the placement htaM ι30 -auε ^s ^ ^zle to move downward, so that the component Ilia is mounted m position on the circuit board 151. After mounting, the placement head 130 releases the component Ilia and then pulls up the nozzle m the Z- direction to a certain level. Then, the imaging head 180 moves m between the circuit board 151 and the placement head 130 so that the imaging device 160 determines whether the component Ilia takes the predetermined position on the circuit board 151. Another imaging device 140, on the other hand, recognizes whether the placement head 130, m particular the tip end of the nozzle, carries any debris. Once the recognition has been completed, the placement head 130 moves back m the X-direction for receiving the next component. By the repetition of the series of operations described above, the components on the expanded panel 112 are mounted sequentially on the respective circuit boards with a cycle time of about, for example, 1.9 seconds. However, the conventional component mounting system has several drawbacks m the recognition operations . For example, for the recognition of the component, the placement head 130 after it has received the component Ilia is accelerated to a certain velocity. Immediately after the acceleration, the placement head 130 comes to a temporal halt for the recognition of the component Ilia by the imaging device 160. This requires further accelr cAion and deceleration of the placement head 130 before the actual mounting of the component Ilia. Also, the placement head 130 after it has come to a halt continues to vibrate for a certain period, which requires the imaging camera 160 to wait until the termination of the vibration in order to attain the precise recognition of the component Ilia. This in turn reduces the operational efficiency of the mounting. Further, as shown in Fig. 14, in the operation for the recognition of the circuit board 151, the nozzle 131 of the placement head 130 is moved upward to the elevated position as indicated by arrow 135. Then, as indicated by arrow 145, the optical head 180 moves in between the elevated nozzle 131 and the circuit board 151 for imaging by the imaging devices 140 and 160. A distance between the elevated nozzle and the circuit board, indicated by alphabet H, is designed to be about 40mm, for example, in order' to prevent the interference of the optical head 180 with the nozzle 131 and also to ensure a proper imaging operation of the optical head 180. The elevation of the nozzle 131 requires 0.1 second even by the use of a high-speed voice coil motor. Furthermore, the conventional mounting system is equipped with an interlock to avoid the interference of the optical head 180 with the placement head 130 during the recognition operations by the optical head 180 befθ-2 and after the mounting. This complicates the structure of the mounting system 100 and makes the system less economical. Moreover, the conventional recognition procedure requires the placement head 130 and the optical head 180 to travel along complicated passes, respectively. This in turn requires the mounting system to have a more number of drive shafts and acceleration/deceleration operations, which further reduces the positional precision of the moving part and thereby the imaging quality. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an improved component mounting apparatus and method. To this end, the component mounting apparatus of the present invention has a component supply provided at a first station for supplying a component; a transport head for picking up the component at the first station from the component supply and then transporting the component :o a second station; a placement head for receiving the component from the transport head at the second station and then transporting the component to a third station; a substrate provided at the third station, the substrate being provided with the component from the placement head at the third station; and an imaging unit for recognizing the component held by the placement head; wherein the first imaging unit is positioned m or m the vicinity of the second station. Another component mounting apparatus of the present invention has a component supply provided at a first station for supplying a component; a transport head for picking up the component at the first station from the component supply and then transporting the component to a second station; a placement head for receiving the component from the transport head at the second station and then transporting the component to a third station; a substrate holder for holding a substrate, the substrate holder being movable between the third station and a fourth station spaced a certain distance away from the third station; a first imaging unit for recognizing the component held by the placement head; and a second imaging unit positioned at the fourth station for recognizing the substrate . Another component mounting apparatus of the present invention has a component supply provided at a first station for supplying a component; a transport head for picking up the component at the first station from the component supply and then transporting the component to a second station; a placement head for receiving the component from the transport head at the second statio ^ nd then transporting the component to a third station; a substrate holder provided at the third station for holding a substrate, the substrate being provided with the component from the placement head at the third station; a first imaging unit for recognizing the component held by the placement head; and a second imaging unit for recognizing the substrate; wherein the first and second imaging units are arranged not to interfere with a passage of the placement head. Also, a component mounting method has picking up a component by a transport head from a component supply at a first station; transporting the component from the first station to a second station by the transport head; transferring the component from the transport head to a placement head at the second station; recognizing the component received by the placement head at or in the vicinity of the second station; transporting the component from the second station to a third station by the placement head; placing the component onto a substrate at the third station by the placement head; and controlling the step of placing the component onto the substrate based upon information obtained by the recognition of the component. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a compcne . : mounting apparatus according to a preferred embodiment of the present invention; Fig. 2 is an exploded perspective view of various elements of the component mounting apparatus in Fig. 1; Fig. 3 is a side elevational view showing the movement of elements in the component mounting apparatus shown in Fig. 1; Figs. 4A through 41 are side elevational views each showing the movement of elements in the component mounting apparatus shown in Fig. 1; Figs. 5A and 5B are graphs showing time versus moving velocity relations of the placement head in the conventional system and the system according to the present invention; Fig. 6 are graphs showing time versus moving velocity relations of the transport and placement heads and the substrate holder together with the transport pass of the component; Fig. 7 is a block diagram of the component mounting apparatus according to the preferred embodiment of the present invention; Fig. 8 is a perspective view of a component mounting apparatus according to another preferred embodiment of the present invention; Figs. 9A through 9K are side elevational views each showing the movement of elements in the component mounting apparatus shown in Fig. 8; Figs. 10A and 10B are side elevational views of the imaging device and the component in the conventional system and the system according to the present invention; Figs. 11A through 11F are side elevational views of the component recognizing device according to another preferred embodiments of the present invention; Fig. 12 is a schematic perspective view of the conventional component mounting apparatus; Fig. 13 is an exploded perspective view of various elements of the conventional component mounting apparatus in Fig. 12; and Fig. 14 is a side elevational view cf the movable elements in the conventional component mounting apparatus in Fig. 12. PREFERRED EMBODIMENTS OF THE INVENTION With reference to the drawings, a variety of embodiments of a component mounting system and its method according to the present invention will be described in detail hereinafter. It should be noted that although a vacuum nozzle is used for holding a component and a circuit board is employed for a substrate to which the component is mounted, the present invention is not limited thereto. For example, the vacuum nozzle may be replaced by another mechanical holder or chuck for holding the component by a mechanical engagement with the component. Also, the substrate may be another device or housing to which the component is mounted. Referring to Fig. 1, there is shown an embodiment of the component mounting system, generally indicated by reference numeral 1, according to the present invention. Generally, the system 1 has a component supply 10 for supplying components to the system 1; a transport head 20 for picking up each component from the component supply 10 and then turning upside down to orient the component m a direction along which the component is mounted onto the substrate; a placement head 30 for receiving the component from the transport head 20 and then mounting the component onto the substrate; an imaging device or camera 40 for imaging a position of the component held by the placement head 30 immediately after the component has been transferred to the placement head 30; a substrate holder 50 for holding and then positioning the substrate m place m the system 1; another imaging device or camera 60 for imaging a position of the substrate; and a controller 70 for controlling the whole operation of the system 1. Referring to Figs. 1 and 2, the transport head 20 is supported by a horizontal guide (not shown) ext e nding in the X-direction and is connected with a motor 22 so that by the driving of the motor 22 the head 20 moves back and forth in the X-direction. The placement head 30 is also supported by a horizontal guide (not shown) extending m the X-direction and is connected with a motor 32 so that by the driving of the motor 32 the head 30 moves back and forth in the X-direction. As can be seen clearly by the comparison of Figs. 2 and 14, m the component mounting system 1 of the present invention, the imaging cameras 40 and 60 are located m different positions. For example, the imaging camera 40 is mounted adjacent a transfer station where the transport head 20 transfers the component to the placement head 30. The imaging camera 60, on the other hand, is mounted on the rear side of and outside a region where the placement head 30 travels m the X-direction so that the imaging camera 60 does not interfere with the placement head 30. Referring again to Figs. 1 and 2, the component supply 10 has an upper table, i.e., X-table (not shown), for supporting the components and a lower table, i.e., Y- table (also not shown), for supporting the X-table. The tables are mounted so that the lower table moves back and forth m Y-direction relative to the system and the upper table moves back and forth in X-direction relative to the lower table. For this purpose, the tables are dπvingly connected with respective motors 13 and 14, so that by the driving of the motors 13 and 14 the tables move back and forth in X- and Y-directions independently, allowing a designated component to take a predetermined pickup position. The transport head 20 is supported by a horizontal guide (not shown) extending in the X-direction and is connected with a motor 22 so that by the driving of the motor the head 20 moves back and forth in the X- direction. A motor 21 is mounted on the transport head 20 for turning the picked component upside down, allowing the component to be transported for the placement head 30 m a condition where the connecting portion of the component is faced down. The placement head 30 is slidably supported by a horizontal guide (not shown) extending m the X-direction and is connected with a motor 32 so that by the driving of the motor 32 the head 30 moves back and forth in the X- direction. A motor 33 is mounted on the placement head 30 for rotating the component about the vertical Z-axis and thereby orienting the component m a predetermined direction. Another motor 34 is provided m the placement head 30 for the vertical movement of a component holding part of the placement head 30. The substrate holder 50, which is slidably supported by a guide rail (not shown) extending in the Y- direction, includes a motor 52 for its movement in the Y- directions along the guide rail. The imaging device 60, which is also slidably supported by a guide rail 60a extending in the X-direction, has a motor 62 for its movement in the X-direction along the guide rail (not shown) . As described above, the component imaging device 40 is fixed in the system 1 at a position where it can oppose the placement head 30. Fig. 3 shows a positional relationship of various parts and stations (i.e., pickup station A, transfer station B, and mount station C) in the system. As can be seen from the drawing, each component supported on the component supply 10 is picked up by the transport head 20 at the pickup station A. The transport head 20 moves in the X-direction (from left to right in the drawing) to the transfer station 3 where it turns upside down to overturn the component into a state in which the component can be mounted on the substrate from its above. The overturned component 11 is then transferred to the placement head 30. The placement head 30 with the component 11 moves to the placement station C to mount the component 11 onto the predetermined position of the substrate 51. In order to control the sequential operations without any trouble, an imaging device or camera 12 is arranged at the pickup station A. The imaging devices 40 and 60 are arranged at the transfer and placement stations B and C, respectively. Also, the imaging devices 12, 40, and 60 are connected to the controller 70 (see Fig. 1) so that the images captured by the imaging devices are transmitted to the controller 70, respectively. As already described above, the imaging device 60 is positioned on the rear side of the placement head 30 to avoid the interference between the imaging device 60 and the placement head 30. Referring next to Figs. 4A to 4H, operations performed at respective stations will be described m detail hereinafter. The drawings illustrate the operations performed at the stations A to C, when viewed m the Y- direction. As can be seen from the drawings, the operations performed at the pickup station A are depicted m Figs. 4A and 4B, operations at the transfer station B are m Figs. 4C to 4E, and operations at the placement station C are m Figs. 4F to 4H. At the pickup station A, as best shown m Fig. 4A, each of the components 11 supported by the component supply 10 is recognized by the imaging device 12 from above. By the use of the information transmitted from the imaging device 12, the controller 70 moves the component supply 10 so that the component 11 to be picked up and then mounted on the substrate 51 takes the pickup position. Then, as shown m Fig. 4B, the transport head 20 reaches above the pickup position and then moves downward to pick up the component at the pickup position. Thereafter, the transport head 20 moves upward and then travels toward the transfer station B, i.e., from left to right m the drawing. At this moment, the imaging device 12 is located above the pass of the transport head 20 so that no interference would be made between them. Referring to Fig. 4C, at the transfer station B, the transport head 20 turns upside down so that the component is oriented into a placement condition. This allows that the electric connections such as solder bumps provided at a bottom surface of the component to be directed downward for the mounting onto the substrate. Although the solder bumps are widely used for the electrical connections between the component and wires on the circuit board for the mounting of, for example, an oscillator, the electrical connections can be performed by the use of a conductive adhesive. Also m this placement condition, a top surface of the component, typically without any bump, is easy to be received or sucked by the vacuum nozzle of the placement head 30. Although the turning operation of the transport head 20 is performed at the transfer station B n this embodiment, it can be done as the transport head 20 moves from the pickup station A to the transfer station B. Also, although the transfer of the component is performed vertically from the transport head 20 to the placement head 30, it can be done in any direction such as horizontally or obliquely. At the transfer station B, the vacuum nozzle of the placement head 30 moves down toward the transport head 20 positioned below the placement head 30 to contact with and then suck the component 11. Simultaneously with this, the transport head 20 releases the component 11, causing the component 11 to be transferred to the placement head 30. After the transfer of the component 11, the transport head 20 moves away from the transfer station B toward the pickup station A (i.e., from right to left in the drawing) for the subsequent pickup operation of the component 11. As shown in Fig. 4E, the movement of the transport head 20 away from the transfer station B allows the component 11 held by the placement head 30 to fall within the field of the imaging device 40 located under the transfer station B. The imaging device 40 recognizes the component 11 held by the placement head 30. The image of the component is then transmitted to the controller 70 by which the position of the component 11, including X- and Y- lateral positions of its center, angular orientation, is determined. During the above operations performed at the pickup and transfer stations A and B, the substrate 51 is transported from a substrate supply not shown into the placement station C and then held by the substrate holder 50. As shown in Fig. 4F, the substrate 51 is opposed to the imaging device 60 for capturing the image of the substrate to identify respective locations of indications marked on the substrate. For this purpose, as best shown in Fig. 4F, the substrate 51 as well as the substrate holder 50 is moved from the placement station C to an offset position, spaced rearward away from the station C. Mounted above the offset position is the imaging device 60 for picking up image of the indications. After the image pickup, the substrate holder 50 together with the substrate 51 is carried back to the placement station C, as shown by the dotted lines in' Fig. 41. It should be noted that the imaging device in the conventional system is designed to move in two directions, i.e., X- and Y-directions, which requires two feed mechanisms. However, the imaging device 60 of the present invention moves back and forth only in the X-direction. This means that one of the two feed mechanisms can be eliminated from the system, which is more economical and improves the quality of the recognition. Also, according to the conventional system the imaging device is designed to move into the operational position m wnich it opposes the substrate. At this moment, in order to avoid the possible interference between the imaging device and the placement head, the placement head as well as tne vacuum nozzle should be moved up and away from the imaging device. This requires another waiting time for the placement head, which results m the extension of the overall mounting time. According to the present invention, the placement head 30 occupies a certain region spaced away from that of the imaging device 60, which ensures that no interference would occur between them. This also allows the imaging device 60 to pick up images at any time, irrelevant to the position of the placement head 30, reducing the mounting The controller 70 determines a positional deviation between a predetermined sucking point and an actual sucking point by the nozzle and an angular orientation of the component, by the use of the image or signals transmitted from the imaging device 40. Also, the controller 70 determines a positional deviation between the predetermined and the actual positions of the indications on the substrate 51, by the use of the image or signals transmitted from the imaging device 60. Taking account of these deviations, the controller 70 calculates a travelling distance to the placement station, a rotating angle of the nozzle 31 about the vertical Z-axis, and a displacement of the substrate 51 with respect to the Y-direction. Based upon the calculation, operations of the motors for moving the placement head 30 and the substrate 51 are controlled by the controller 70. After the transfer and the recognition of the component at the transfer station B, the placement head 30 begins to move toward the placement station C (i.e., from left to right m the drawing) . Also, after the correction of the positional deviation and the angular orientation by the controller 70, the placement head 30 moves to the placement station C, as shown m Fig. 4G. Thereafter, as shown m Fig. 4H the placement head 30 places the component 11 in place on the substrate 51. In this operation, the nozzle 31 sucking ana holding the component moves down with the placement head 30 toward the substrate 51. Once the solder bumps provided on the bottom surface contact with the substrates 51, the placement head 30 forces the component 11 against the substrate 51. Simultaneously, the placement head 30 applies a high frequency vibration to the component 11, causing the solder bumps to be connected with the substrate. The vibration may be an ultrasonic wave generated by a piezoelectric device. For example, the ultrasonic wave has an amplitude of about 1 micron and a frequency of about 63,000 per minute. After the completion of the component mounting, the placement head 30 moves back to the transfer station B for the subsequent mounting of the component. The imaging device 40 picks up the image of the placement head 30 as the head is waiting for the next transfer operation to determine the existence of debris. If the debris is detected, the system suspends the subsequent operations for the removal of the debris, which would otherwise cause any damage to the component 11 or the nozzle 31. This operation can equally be applied to the transport head 20. In this instance, the imaging device 40 picks up the image of the nozzle of the transport head 20 to detect any debris on the nozzle. Preferably, this is performed as the placement head 30 is moving toward the placement station C. Further, at the placement station C, after the placement operation by the placement head 30, the substrate 51 may move rearward to a shifted position where it opposes the imaging device 60 for picking up an image of the substrate 51 and thereby determining whether the component 11 has been mounted m place on the substrate 51. The imaging device 40 positioned at the transfer station B allows the component 11 to be recognized before the placement head 30 begins to move toward the placement station C, which ensures the placement head 30 to move continuously without any halt. The position of the imaging device 40 is not limited thereto. For example, the imaging device 40 may be positioned in the vicinity of the transfer station B or in another position spaced slightly away from the position where the component is transferred from the transport head 20 to the placement head 30. The reason why the imaging device 40 is placed at or immediately adjacent the transfer station is to avoid any loss of time which is caused in the conventional operation that requires the placement head needs to halt after it has reached the maximum speed in the course of moving from the transfer station to the placement station for the recognition of the component and also the imaging device to wait until the vibration caused by the halt will come to an end. In this regard, the time loss can be reduced to some extent even when the placement ' head makes a halt before it reaches the maximum speed. Therefore, the terms "vicinity" and "spaced slightly" means a certain range in which the placement head is accelerated up to the maximum speed. Referring to Figs. 5A and 5B, descriptions will be made to this in details. As shown in Fig. 5A, according to the conventional system in which the placement head halts in the course of moving from the transfer station to the placement station for the recognition of the component by the imaging device, a certain time of about 0.1 second is required for damping the vibration of the placement head caused by the mertial force of the placement head with a weight of about 10 kilograms, for example. After recognition, the placement head moves to the placement station, during which it is accelerated and then decelerated again. Contrary to this, according to the mounting system of the present invention, as shown m Fig. 5B, after the transfer of the component, the transport head 20 moves away from the field of the imaging device. Immediately after that, the component held by the placement head 30 is recognized. Then, the placement head 30 accelerates to the maximum speed, moves with the speed, and then decelerates to reach the placement station. This eliminates the additional acceleration and deceleration required in the conventional system, which decreases the cycle time by about 0.2 seconds. Fig. 6 shows a relationship of movements and operations for the placement head 30, transport head 20, and substrate holder 50. As can be seen from the drawing, after the placement of the component, the placement head 30 moves back from the placement station C to the transfer station B. In synchronism with this, the transport head 20 which has already picked up the subsequent component moves from the pickup station A toward the transfer station B. The heads 20 and 30 halt to oppose each other at the transfer station B and then approach each other for the transfer of the component from the transport head to the placement head, which is illustrated by a hollow arrow directed upward. Immediately after the transfer of the component, the transport head moves back toward the pickup station, allowing the recognition of the component held on the placement head 30 by the use of the imaging device. The recognition operation of the component is illustrated as a hatched box. When the recognition is completed, the placement head 30 moves toward the placement station C. During the movement of the placement head 30, the recognition operation for the substrate 51 is performed, which is illustrated as another hatched box. Then, the substrate holder 50 moves to the placement station C where the placement head 30 places the component on the substrate 51, which is illustrated by a hollow arrow directed downward. During this, the transport head 20 picks up the subsequent component from the component supply. The above- described operations are repeated for each component. Provided below is a comparative table showing movement axes and mechanisms (i.e., feed mechanisms for X-, Y-, and/or Z-direction) for the transfer and placement heads, the imaging devices, and the substrate holder, required for the conventional system and the system of the present invention. It should be noted that the increase of the number of the feed mechanisms complicates the structure of the system and also decreases the positional precision of the component and the devices such as head and substrate. TABLE Element Feed Mech. Required Improvement System 1 System 100 Z-Displacement Head 20 X, Z X, Z Reduced Z-Displacement Head 30 X, Z X, Z Reduced X, Y No X, Y-Feed Mech Device 40 ' Y or Z ' [No X-Feed Mech, Holder 50 Y Y No Y-Feed Mech. Device 60 X, Y X X-Displacement Reduced As can be seen from the table, the system according to the present invention, the fixed imaging device 40 does not need X- and Y-feed mechanisms needed for the conventional system. This not only simplifies the structure of the system but also increases the positioning and imaging precision. Meanwhile, the imaging device 40 may be designed to move Y- or Z-direction, which will be described below. Even m this embodiment, one of the two mechanisms is eliminated. This is illustrated m the table by bracketing. For the imaging device 60, only one (i.e., X- feed) mechanism is needed. This means that one mechanism can be eliminated from the conventional system which needs two (X- and Y- ) feed mechanisms. This is because the substrate 51 is shifted away from the placement station to another position for its recognition by the imaging device 60. The reduction of the feed mechanism also increases the recognition precision of the substrate. Although the system is designed so that the substrate holder moves back and forth m Y-direction, it may be moved m another direction provided that the substrate can be recognized by the imaging device m a certain position away from the placement station and the imaging device 60 does not make any conflict with the placement head 30. Further the system of the present invention can shorten the moving passes of respective moving elements. For example, according to the conventional system the vacuum nozzle 31 of the placement head 30 is required to move about 40mm m the vertical direction m order to avoid the interference with the imaging devices. Contrary to this, according to the system of the present invention, the imaging devices 40 and 60 are located at difference positions and outside the passage of the placement head 30 m the movements m the X-direction. This minimizes the vertical movements of the nozzle 31 m the placement head 30 at the transfer and placement stations down to about 1mm, for example, which is required for the prevention of the interference with the component. Further, according to the conventional system, the imaging device for the substrate recognition is assembled with another imaging device for the component recognition. This requires both imaging devices to move a long distance of about 250mm, for example, between the component and substrate recognition stations. However, according to the system of the present invention, the substrate recognition device is separated from the other component recognition device so that it is served only for the recognition of the substrate. Therefore, the substrate recognition device is required to move only a limited distance of about 10mm, for example, which might differ depending upon the size or the purpose of the component. The reduction of the moving distance results m the reduction of the mertial force of the movement mechanism as well as the necessary rigidity of the supporting structure and also m the increase of the precision of the positioning . As described above, the system 1 of the present invention has a number of moving parts. Among other things, the placement head 30 moves about 500mm m the X-direction between the transfer and placement stations B and C. The movement of each element should be controlled precisely m order to attain the precise alignment of the components on the substrate. For this purpose, the system employs servomotors, pulse-motors, and/or voice-coil motors for controlling the moving distance of the elements. In addition to those motors and m combination therewith, a linear scale may be used for each moving mechanism m order to attain a more precise control of the moving distance. The linear scale, which is a pulse encoder for measuring a liner displacement, has a reference scale with indices marked optically or magnetically and a detector mounted for movement on and relative to the reference scale, which ensures a precise movement control. Taking such feature into account, the linear scale is preferably used for the compensation of the change of moving distance that might be caused by heat. Fig. 7 is a circuit diagram showing various parts incorporated m respective devices described above. As can be seen from the drawing, the system has a hardware section and a software section. The hardware section includes the component supply 10, transport head 20, placement head 30, component recognition device 40, substrate holder 50, and substrate recognition device 60. The software section includes various processing units for controlling necessary operations for supplying component, sucking component, calculating an amount for position correction, calculating an amount for angular correction, recognizing component, recognizing reference-indication, and correcting position. The hardware and software elements are integrated with the controller that controls the overall operations of the elements . Each of the hardware elements whose operations are already described above has various drivers connected through respective lines extending out from the elements. The controller receives signals from respective units of the software section and, based on which, controls respective drivers. Among other things, the component supply processing unit controls the movement of the component supply 10 so that the component to be picked up is placed at the pickup position. The component sucking processing unit controls timing and vacuum for tne component sucking by nozzles mounted on the transfer and placement heads. The units for calculating positional and angular corrections calculates, from signals transmitted from the recognition device 40, a moving distance of the placement head 30 m the X-direction for the mounting and the amount of angular correction for the nozzle 31 about the vertical Z-axis. The component recognition unit controls the recognition timing by the recognition device 40 and the field of the device. The reference-indication recognition unit controls the recognition timing and the field of the substrate recognition device 60 and, based upon the recognition by the device 60, the position correction unit controls the moving distance of substrate holder 50 m the Y-direction. With the arrangement, the recognition devices 40 and 60 are separated from each other, which allows respective devices 40 and 60 to be controlled independently, without any restriction imposed by the other device. Referring to Fig. 8, another mounting system and method according to the second embodiment of the present invention will be described hereinafter. The component mounting system of this embodiment, generally indicated by reference numeral 2, is similar to that of the first embodiment except that the system 2 has a second placement head 80. Therefore, like parts bears like reference numerals throughout the drawings. Meanwhile, according to the system of the first embodiment, the placement head 30 receives the component at the transfer station B and then moves to the placement station C for the mounting of the component. The mounting of the component at the placement station C is completed by the ultrasonic connection, which needs a relatively extended period of time of about 0.5 seconds. This increases a waiting time of associated element or elements, which results in an unwanted extension of the overall time for mounting. Contrary to this, in tne system 2 of this embodiment, the first and second placement heads bear respective functions and thereby enhance the productivity of the mounting. For example, the system 2 is designed so that the placement head 30 serves for a first step of mounting m which the component 11 is mounted on the substrate 51 and then connected temporally by the ultrasonic vibration. The temporal connection requires only a limited time of about 0.1 second. After the temporal connection, the placement head 30 moves back from the placement station C to the transfer station B where it receives the next component from the transport head. The second placement head 80 serves for a second step of mounting in which it applies the ultrasonic vibration again to the temporally connected component 11 for the permanent connection of the component to the substrate. The permanent connection requires another time of about 0.4 seconds . With the two-step connection embodiment, the first (temporal) and second (permanent) connections by the placement heads 30 and 80 require about 0.1 and 0.4 seconds, respectively. Therefore, the total connection time appears to be identical to that required by the system 1 of the first embodiment. However, according to the system 2, after the temporal connection, i.e., during the permanent connection, the placement head 30 can proceed to receive the next component, which means that the overall time for mounting per component is substantially reduced by, for example, 0.4 seconds. Therefore, the functional separation using two placement heads causes the overall time for mounting of the component to be reduced considerably and also the productivity of the system to be increased significantly. Besides, the two-step connection provides a drastic increase of the connecting force of the component than the one-step connection. In order to provide the ultrasonic vibration to the component effectively, another holder in the form of bracket or box cover may be used for holding the component and then forcing it to the substrate. Also, in the two-step connection, the position and/or orientation of component mounted temporally on the substrate may be recognized by the recognition device and, if necessary, corrected at the permanent connection base upon the recognition result. In this instance, immediately after the temporal connection of the component by the placement head 30, the substrate 51 is transported rearward to oppose the fixed recognition device 60 for the recognition of the component mounted temporally on the substrate. Then, baseα on the positional information transmitted from the recognition device 60, the controller 70 calculates the amount for X-, Y-, and/or angular correction and then controls the movement of the other placement head 80. Preferably, the recognition device 40 recognizes the component holding portion of the placement head 30 immediately after the temporal mounting of the component and the component holding portion of another placement head 80 before the permanent mounting of the component. This allows the controller 70 to prevent any possible accidents, which may be caused by the existence of debris at the component holding portions of the placement heads. Also, this allows the placement head 80 to hold the temporally mounted component positively. Figs. 9A to 9J schematically shows a series of operations performed at the pickup, transfer, and placement stations by the system 2. As can be seen from the drawings, the operations illustrated m Figs. 9A to 9G are the same as those illustrated m and described with reference to Figs. 4A to 4G. According to the system 2 of this embodiment, m particular, the component 11 is temporally mounted on and connected with the substrate 51 as shown in Fig. 9H. After the completion of the temporal connection of the component, the placement head 30 moves back in the X-direction to the transfer station B for the transfer operation of the next component. After the disengagement with the placement head 30, the substrate 51 moves rearward in the Y-direction to oppose the recognition device 60. As shown in Fig. 91, the recognition device 60 recognizes the component temporally connected on the substrate 51 and then transmits the recognized image signal to the controller 70. The positional relationship between the substrate 51 and the recognition device 60 is similar to that shown in Fig. 9K. After the recognition, the substrate 51 moves back in the Y-direction to the placement station where it opposes the second placement head 80. As shown in Fig. 9J, the placement head 80 moves downward to hold the temporally connected component 11. Also, the placement head 80 forces the component 11 to the substrate and then provides the component with the ultrasonic vibration for the permanent connection of the component to the substrate. As best shown in Fig. 9J, the component holding portion of the placement head 80 is defined in the form of bracket. Alternatively, the placement head takes another configuration suitable for the positioning of the component and the application of the ultrasonic vibrations to the component . It should be noted that when any misalignment such as improper mounting or connection of the component is detected by the recognition device 60 (see Fig. 91), the controller 70 suspends the mounting operation to make a warning. In this case, if necessary, the substrate 51 may be discarded automatically or manually. Referring to Figs. 10A and 10B, another embodiment of the system according to the present invention will be described hereinafter. The drawings illustrate positional relationships between the component sucked and held by the nozzle 31 of the placement head 30 and the recognition devices m the conventional system (Fig. 10A) and the system of the present invention (Fig. 10B) , respectively. As described above with reference to Figs. 13 and 14, according to the conventional system the space between the component Ilia held by the nozzle 131 of the placement head 130 and the substance 151 is so limited. This fails to ensure a distance, between the recognition device 140 and the component, necessary for the proper recognition of the component, which reduces the resolution of the image of, in particular, the large size component. Contrary to this, the recognition device 40 is mounted only for the recognition of the component and therefore fixed m the system, which does not need additional space to avoid the interference with the neighboring members. This m turn defines a larger space between the recognition device 40 and the component than the conventional system, which increases the field and/or resolution of the recognition device 40. The increase of the field and resolution are illustrated by dotted lines a and long and short dotted lines β m Fig. 10B Improvement on the field anα/or resolution of the recognition device can be attained by another embodiments illustrated m Figs. 11A to 11F. For example, according to the embodiment m Fig. 11A, the recognition device 40 is designed to shift m the direction indicated by arrow 45, i.e., the X- or Y-direction, to a certain extent. With the arrangement, first the recognition device 40 occupies a first position where it recognizes a part of the component. Then, the recognition device 40 moves to a second position where it recognizes the remaining part of the component. Partial images of the component are then combined and processed at the controller for the subsequent processes such as position and/or angular correction of the component. This process allows the recognition device to capture the entire image of the component with a necessary resolution even within a limited space. This m turn means that the moving range of the recognition device for the component recognition can be minimized. In addition, the horizontal movement of the recognition device 40 ma reduce the likelihood that it suffers from any damage by the possible drop of the component or other members. Although the whole image of the component is captured through two pickup processes, more number of pickup processes can be employed for the larger component. In another embodiment in Fig. 11B, the recognition device 40 is designed to move vertically, i.e., in the Z-direction between a lowered position indicated by solid lines and an elevated position indicated by dotted lines. This embodiment allows the recognition device 40 to shift its focus vertically so that the components with different heights or at different levels can be recognized without any defocus. For example, as shown in the drawing the larger component 11 is moved down from the elevated to the lowered position to extend its field, so that the entire image of the larger component can be captured by one shot. The recognition device 40, due to its movability in the vertical direction, is also available for the detection of debris carried by the component holding portion of the transfer and placement heads 20 and 30. In another embodiment in Fig. 11C, the recognition device 40 is supported by a horizontal axis not shown so that it rotates as indicated by arrow 47. This arrangement allows the recognition device 40 to take between a first position (indicated by solid lines) where it recognizes a part of the component and a second position (indicated by dotted lines) where it recognizes the remaining part of the component. For this purpose, the recognition device is connected with a driving source such as pulse motor that is controlled by the controller. The system may be designed so that the recognition device takes three positions where the recognition device captures respective parts of the component. In another embodiment in Fig. 11D, the recognition unit has two fixed recognition devices 40a and 40b in order to enlarge the field of the recognition unit. This arrangement allows the larger component to be recognized by two recognition devices with a high resolution. Also, this arrangement may be used so that either one of the ' recognition devices works for a small component, and both for a large component. Of course, the number of the recognition is not limited to two. In another embodiment in Fig. HE, the recognition device 40 is oriented horizontally. Also, the recognition unit has a mirror 41. The mirror 41 is located in front of the recognition device 40 and supported for rotation so that the field of the recognition device is reflected and then moved across the component. With this arrangement, the mirror rotates between a first position where the reflected field of the recognition device covers a part of the component and a second position where the reflected field covers the remaining part of the component. For this purpose, the mirror is dπvmgly connected to a motor, such as pulse motor, so that the controller controls the motor to rotate the mirror. The mirror may be any member capable of changing a light pass, such as prism. In another embodiment m Fig. 11F, the recognition unit has an optical member 42 such as lens positioned between the recognition device 40 and the component 11, allowing the recognition device 40 to pick up the image of larger component. The optical member 42 may be supported to move out of the space between the recognition device 40 and the component 11. Two or more optical members may be prepared so that a suitable one of which is selected depending upon the s ze of the component and/or the required resolution. Also, the optical member 42 may be used m combination with other optical elements such as mirror and prism. Further, the recognition device 40 may be supported for movement not only m this embodiment but also m the previous embodiment m Fig. HE, which enlarges the field of the recognition device while keeping the required resolution. While this invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled m the art. Accordingly, it is intended to embrace all such alternatives, modifications, and variations that fall within the spirit and broad scope of the appended claims.

Claims: CLAIMS 1. A component mounting apparatus, comprising: a component supply provided at a first station for supplying a component; a transport head for picking up the component at the first station from the component supply and then transporting the component to a second station; a placement head for receiving the component from the transport head at the second station and then transporting the component to a third station; a substrate holder provided at the third station for holding a substrate, the substrate being provided with the component from the placement head at the third station; and an imaging unit for recognizing the component held by the placement head; wherein the imaging unit is positioned m or in the vicinity of the second station. 2. The component mounting apparatus in accordance with claim 1, wherein the imaging unit is fixed in or in the vicinity of the second station. 3. The component mounting apparatus in accordance with claim 1, wherein the imaging unit is movable in a direction perpendicular to another direction along which the imaging unit opposes the placement head for the recognition of the component . 4. The component mounting apparatus in accordance with claim 1, wherein the imaging unit is movable in a direction along which the imaging unit opposes the placement head for the recognition of the component. 5. The component mounting apparatus in accordance with claim 1, wherein the vicinity is defined by a range in which the placement head is accelerated up to the maximum speed in the course of the movement thereof from the second station toward the third station. 6. The component mounting apparatus in accordance with claim 1, wherein the transport head turns the component upside down after receiving the component at the first station and before transferring the component at the second station. 7. The component mounting apparatus in accordance with claim 1, wherein the imaging unit is supported so that it recognizes different portions of the component. 8. The component mounting apparatus m accordance with claim 1, wherein the imaging unit has a plurality of imaging devices . 9. The component mounting apparatus m accordance with claim 1, wherein the imaging unit has an optical member for changing an optical feature of the first imaging unit. 10. The component mounting apparatus in accordance with claim 9, wherein the optical member is a mirror, prism, or lens, or a combination thereof. 11. The component mounting apparatus in accordance with claim 1, wherein the imaging unit recognizes a portion of the transport head and/or a portion of the placement head, for holding the component. 12. A component mounting apparatus, comprising: a component supply provided at a first station for supplying a component; a transport head for picking up the component at the first station from the component supply and then transporting the component to a second station; a placement head for receiving the component from the transport head at the second station and then transporting the component to a third station; a substrate holder for holding a substrate, the substrate holder being movable between the third station and a fourth station spaced a certain distance away from the third station; a first imaging unit for recognizing the component held by the placement head; and a second imaging unit positioned at the fourth station for recognizing the substrate. 13. The component mounting apparatus in accordance with claim 12, wherein the second imaging unit is movable in a first direction along which the placement head moves between the second and third stations, and the substrate holder is movable in a second direction perpendicular to the first direction. 14. The component mounting apparatus in accordance with claim 13, further comprising a fixing head, so that the placement head makes a temporal connection of the component to the substrate and then the fixing head makes a permanent connection of the component to the substrate. 15. The component mounting apparatus in accordance with claim 14, wherein the second imaging unit recognizes the component on the substrate after the temporal connection and before the permanent connection of the component. 16. The component mounting apparatus in accordance with claim 14, wherein the second imaging unit recognizes portions of the placement head and the fixing head for holding the component. 17. The component mounting apparatus in accordance with claim 16, further comprising a linear scale mounted on a shaft for guiding the placement head between the second and third stations. 18. A component mounting apparatus, comprising: a component supply provided at a first station for supplying a component; a transport head for picking up the component at the first station from the component supply and then transporting the component to a second station; a placement head for receiving the component from the transport head at the second station and then transporting the component to a third station; a substrate holder provided at the third station for holding a substrate, the substrate being provided with the component from the placement head at the third station; a first imaging unit for recognizing the component held by the placement head; and a second imaging unit for recognizing the substrate; wherein the first and second imaging units are arranged not to interfere with a passage of the placement head. 19. A component mounting method, comprising the steps of: picking up a component by a transport head from a component supply at a first station; transporting the component from the first station to a second station by the transport head; transferring the component from the transport head to a placement head at the second station; recognizing the component received by the placement head at or in the vicinity of the second station; transporting the component from the second station to a third station by the placement head; placing the component onto a substrate at the third station by the placement head; and controlling the step of placing the component onto the substrate based upon information obtained by the recognition of the component. 20. A component mounting method in accordance with claim 19, wherein the vicinity is defined by a range in which the placement head is accelerated up to the maximum speed in the course of the movement thereof from the second station toward the third station. 21. A component mounting method in accordance with claim 19, further comprising a step of making a permanent connection of the component to the substrate at the third station by a fixing head, after the step of placing the component onto the substrate by the placement head.

Inventors: KANAYAMA SHINJI, MINAMITANI SHOZO, ONOBORI SHUNJI, SHIMIZU TAKASHI, SIDA SATOSHI, UENO YASUHARU, KANAYAMA, SHINJI, MINAMITANI, SHOZO, ONOBORI, SHUNJI, SHIMIZU, TAKASHI, SIDA, SATOSHI, UENO, YASUHARU
Applicants: KANAYAMA SHINJI, MATSUSHITA ELECTRIC IND CO LTD, MINAMITANI SHOZO, ONOBORI SHUNJI, SHIMIZU TAKASHI, SIDA SATOSHI, UENO YASUHARU, KANAYAMA, SHINJI, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD., MINAMITANI, SHOZO, ONOBORI, SHUNJI, SHIMIZU, TAKASHI, SIDA, SATOSHI, UENO, YASUHARU
Application year: 2001
Main classification: H05K3
IPC codes: H01L21, H05K13