JP4334985B2 - Substrate mounting device - Google Patents

Description

  The present invention relates to a ball mounting apparatus for mounting solder balls or the like on a substrate such as an electronic circuit board or a semiconductor wafer.

  As a ball mounting device, a ball dropping method is disclosed (Japanese Patent Laid-Open No. 2000-049183). Further, a substrate mounting device in which an XYZθ driving device is incorporated is disclosed (see Japanese Patent Application Laid-Open No. 2001-068840).

However, since the ball drop-type ball mounting device adopts a method in which the ball is dropped into the opening of the mask corresponding to the electrode on the substrate by the weight of the ball, the weight of the ball is reduced when the ball diameter is reduced to 200 μm or less. As a result, the number of openings into which the balls are not dropped increases. Further, the probability that the ball is not dropped into the opening of the mask and the probability of jumping out of the opening after the ball is dropped into the opening are remarkably increased when the warpage of the substrate or the warpage of the mask is increased.
On the other hand, the conventional substrate mounting apparatus discloses a mechanism for vacuum-adsorbing the substrate, but does not disclose a mechanism for closely attaching the mask to the substrate or a mechanism for pressing and flattening the substrate.
JP 2000-049183 A JP 2001-068840 A

  The present invention solves such problems, puts the mask in a detachable manner on the substrate, puts the substrate mounting device with a small mask warpage into practical use, and puts the ball mounting device on which fine balls can be mounted into practical use. The purpose is to provide.

  The present invention solves the above-described problems, and includes a substrate mounting device for mounting a substrate, a mask having an opening for dropping a solder ball, a ball dropping device for dropping a solder ball into the opening, and a substrate. In a ball mounting device comprising a ball pressing device that presses a mounted solder ball, the substrate mounting device includes an XYΘZ table, a substrate mounting table fixed to the XYΘZ table via a fixing jig, and the XYΘZ It is characterized by comprising a Z-axis driving device provided on a table and an attracting force generating device which is connected to the Z-axis driving device and is movably mounted up and down between an XYΘZ table and a substrate mounting table.

Further, the present invention is provided with a substrate flattening device for flattening a substrate, and the substrate flattening device comprises a horizontal movement device, a vertical movement device, and a substrate pressing jig. Moves on the substrate placed on the substrate placement table and presses at least four locations of the substrate.

By configuring the substrate mounting device like this,
(1) Since the mask and the substrate are in close contact, the ball can be dropped stably in the step of dropping the ball.
(2) In the step of separating the mask from the substrate, it is possible to separate the mask from the substrate after the adsorption force generating device is lowered. In the step of separating the mask from the substrate, damage to the mask is reduced.

  An object of the present invention is to mount a fine solder ball on a large-sized substrate by improving the substrate mounting apparatus. Hereinafter, embodiments of a ball mounting apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 is a plan view of an embodiment of a ball mounting apparatus. FIG. 2 is a front view of this apparatus. 1 and 2 will be described together.

The ball mounting device includes a substrate mounting device 1, a substrate flattening device 2, a ball pressing device 3, a ball dropping device 4, and a cleaning device 5. The substrate mounting device 1, the ball pressing device 3, and the ball dropping device 4 are arranged in series (X direction).

In the substrate platform 1, the substrate platform X-axis rail 7 and the substrate platform Y-axis rail 8 are arranged at right angles, and an XY table 9 is mounted thereon. A Θ rotation motor is disposed on the XY table 9. The XYΘ table 11 is provided between the Θ rotation motor 10 and the Z-axis drive device 12. An XYΘZ table 13 is mounted on the Z-axis drive device 12. On the XYΘZ table 13, a Z-axis air cylinder 15, a substrate mounting table fixing bracket 17, and a camera fixing bracket are attached.

The suction force generating device 16 is disposed in a space between the XYΘZ table 13 and the substrate mounting table 13 and is attached to be movable up and down by four Z-axis air cylinders 15. The attracting force generating device 16 is an electromagnetic field generating device and attracts the mask 44 to the substrate 6.

The substrate mounting table 18 is fixed by two substrate mounting table fixing brackets 17. On the upper surface of the substrate mounting table 18, an opening or a vacuum suction pad for vacuum suction of the mounted substrate 6 is provided. The mask position measuring camera 19a is fixed via a camera fixing bracket.

The mask position measurement camera 19a uses a CCD having a total number of pixels of 410,000 in an interline method. The mask position measuring camera 19a can also measure the position of the ball pressing head 34.

The substrate flattening device 2 includes a horizontal movement device (air cylinder 22) and a device (Z-axis air cylinder) for vertical movement and pressing so that the substrate pressing jig 20 can press a predetermined portion of the substrate 6. 21). The substrate pressing jig 20 includes four arms and eight protrusions attached to the arms. The number of protrusions may be 4 or 9, and is not limited. Further, the position of these protrusions is a mechanism that can be adjusted in accordance with the dimensions of the substrate 6.

The ball pressing device 3 includes a ball pressing head 34, a leveling adjustment device 53, a Θ rotation driving device 36, and a Z-axis driving motor 33. The ball pressing head 34 is fixed to the levelness adjusting device 53 via a ball pressing head mounting plate 34a. The ball pressing head 34 adjusted in level with the substrate 6 is lowered by the Z-axis drive motor and presses the ball dropped into the opening of the mask 44 against the substrate 6. Since the mask 44 is fixed to the fixing base 23, the ball pressing head 34 moves onto the mask 44 in the step of pressing the ball. In a process such as a ball dropping process, the ball pressing head 34 can be moved to a position that does not get in the way. Further, the ball pressing head 34 can be moved in the Y direction by the motor 29 and the ball screw 30 and further moved in the Z direction by the Z-axis moving motor 33 and the slider 35. When the diameter of the solder ball is larger than the thickness of the mask 44, the lower surface of the ball pressing head 34 is a flat plate. On the other hand, when the diameter of the solder ball is smaller than the thickness of the mask 44, a protrusion is formed at a position corresponding to the solder ball. Has been. The ball pressing head 34 provided with the protrusions needs to be aligned with the mask 44, and in the case of a flat plate, alignment with the mask 44 is not necessary.

The ball pressing device 3 is disposed on an X rail 26 provided on a fixed base 23 supported by four support columns 24 via a moving substrate 28. A ball screw that is rotated by a motor 27 is incorporated in the X rail, and the ball pressing device 3 moves on the X rail 26 by the rotation of the motor 27.

The ball dropping device 4 drops the solder ball into the opening of the mask 44 while moving the solder ball supplied on the mask 44 superimposed on the substrate 6 with the squeegee 43. The squeegee 43 is fixed to the air cylinder 41 and the slider 42 via a squeegee mounting jig 43a, and can be moved up and down by the air cylinder 41 and in the X direction by the motor 27. The squeegee 43 is composed of a brush, an air blower, or the like. The ball dropping device 4 is composed of a pair of going and returning, each consisting of one air cylinder, two sliders and one squeegee.

The cleaning device 5 is a device that cleans the dirt of the mask 44, and includes a cleaning paper 52, a supply roller 51a and a take-up roller 51b of the cleaning paper 52 attached to the cleaning device frame, and can be moved below the mask 44. Are provided with a Y-axis rail 48, a motor for pressing the cleaning paper against the mask 44, a motor for driving the supply roller and the take-up roller (not shown). Since the height of the cleaning device itself is low, it is arranged on the cleaning device base 46 higher than the installation surface of the ball mounting device.

FIG. 3 is a front view of the ball pressing device 3. The level adjustment device 53 includes an X-axis rotation device 38 and a Y-axis rotation device 37. The two rotating devices are the same, and the mounting angles differ by 90 degrees. Each is provided with a knob (37a, 38a) for adjusting the angle, and the adjustment angle can be read by the vernier 37b. In order to adjust the parallelism within 5 μm, for example, when the length of the substrate 6 is 35 cm, the angle accuracy must be 0.3 seconds or less. Angular accuracy can be achieved by rotating the knob, but the vernier display is insufficient, so the distance displayed digitally using three to four distance meters 54 (see FIG. 4) arranged on the substrate mounting device. Adjust the parallelism referring to.

FIG. 4 is a front view of the substrate mounting apparatus 1, and FIG. 5 is a side view thereof. The suction force generation device 16 is installed to be movable up and down between the XYΘZ table 13 and the substrate mounting table. When the solder ball is dropped into the opening of the mask 44, the mask 44 needs to be flat. The attraction force generation device 16 is a device that attracts the mask 44 to the substrate 6 using an electromagnetic field such as an electric field or a magnetic field. When the substrate 6 is thin such as COF (Chip On Film), the suction force generating device 16 causes the mask 44 to be adsorbed flat on the substrate 6 by an electric field when the mask is an insulator or the mask surface is an insulator. Can do. Further, when the substrate 6 is thick, it is effective that the attraction force generating device 16 uses the magnetic field as the attraction force by manufacturing the whole or a part of the mask 44 with a ferromagnetic material. When the mask 44 is in close contact with the substrate 6 in most of the areas except for the openings, the adhesion with the substrate 6 can be increased. However, when the adhesive or flux is applied to the substrate 6, the mask 44 is easily contaminated. When the substrate 6 is a semiconductor wafer, if the central portion where the bumps are not formed in the semiconductor integrated circuit is made of a ferromagnetic material and the space between the bumps is made of a non-magnetic material, the contamination of the mask 44 can be reduced. . A method of partially forming a ferromagnetic material on the mask 44 can be easily made by using a conventional photolithography technique. Further, if the ferromagnetic body itself is used as a spacer or a spacer is provided in the region, the mask 44 can be particularly prevented from being contaminated.

  The XYΘZ table 13 is provided with three to four distance meters 54, which measure the distance between the ball pressing head 34 and the substrate mounting table and display it on a digital display meter (not shown). Yes.

Next, the alignment between the ball pressing head 34 and the mask 44, the alignment between the mask 44 and the substrate 6, the alignment between the ball pressing head 34 and the substrate, and the parallelism between the ball pressing head 34 and the substrate 6. The adjustment of the will be described.

The ball pressing head 34 and the mask 44 are aligned by measuring the position mark of the mask 44 and the position mark of the ball pressing head 34 with the mask position measuring camera 19a, and rotating the motor 29 and Θ so that only the coordinates in the X direction are different. The ball pressing head is moved by the driving device 36.

The position mark of the mask 44 is measured by moving the mask position measuring camera 19a because the mask 44 is fixed to the fixed base 23. On the other hand, the measurement of the position mark of the ball pressing head 34 is performed by sending the ball pressing head 34 to a position away from the fixed base 23, lowering it to the same height as the mask 44, and moving the mask position measuring camera 19a to the ball pressing head 34. Move down and do it.

In the case of the ball pressing head 34 having a protrusion for pressing the solder ball, the protrusion for pressing the solder ball is aligned with the opening position of the mask 34 in advance. The opening of the mask is provided in the mask corresponding to the electrode of the substrate on which the solder ball is mounted. Further, the mask is fixed by applying tension to a mask frame (not shown). Attaching the mask to the mask pressing jig means that the mask fixed with the mask frame being tensioned is attached to the mask pressing jig together with the mask frame.

The alignment between the mask 44 and the substrate 6 is performed in the following steps. After the substrate 6 is placed on the substrate placement table 18, the substrate placement device 1 is moved below the substrate position measurement camera (19 b, 19 c), and the planar positions of the two position marks provided on the substrate 6. Is used as the reference coordinates of the substrate 6. Next, the substrate mounting apparatus 1 is moved below the mask 44, the plane positions of the two position marks provided on the mask 44 are read, and used as the reference coordinates of the mask 44. The difference between the reference position of the substrate 6 and the reference coordinates of the mask 44 is in a relationship determined by specifications. The substrate 6 is moved using the XYΘ table 13 so as to satisfy this relationship. This alignment is performed every time the substrate 6 is placed.

  The alignment between the ball pressing head 34 and the substrate 6 is determined by calculation using the coordinate data obtained by the alignment between the ball pressing head 34 and the mask 44 and the alignment between the mask 44 and the substrate 6 previously performed. It is done.

Since the parallelism between the ball pressing head 34 and the substrate 6 cannot be adjusted directly, the ball pressing head mounting plate 34a and the substrate mounting table 18 are used as substitutes to adjust the parallelism indirectly. Is called. The ball pressing head mounting plate 34a is measured by using three distance meters 54 that can measure three points of the ball pressing head mounting plate 34a with the state where the ball pressing head mounting plate 34a is in close contact with the substrate mounting table 18 as Z-axis reference coordinates. And the knobs (37a, 38a) are rotated so that the difference between the Z-axis reference coordinate and the Z-coordinate of the ball pressing head mounting plate 34a is the same or less than a predetermined reference value at three points. . That is, adjustment is made so that the error of the Z coordinate of the three points is 5 μm or less. However, the error of the three Z coordinates is more preferably 2 μm or less.
Although a mechanism for adjusting the degree of parallelism between the mask 44 and the substrate 6 is not shown, a leveling adjustment device may be connected to the mask holding jig 45. This is particularly effective when the ball diameter is reduced, and particularly when the ball diameter is 100 μm or less.

FIG. 6 shows a flowchart of an operation of dropping the solder ball into the opening of the mask 44 and then pressing the solder ball against the substrate 6 to temporarily fix it.
Step 1 (S1) is a process of placing the substrate 6 on the substrate placing apparatus 1. The substrate 6 stored in the magazine is pushed out by a pusher, slid on the rail, moved onto the substrate mounting table 18, and the substrate mounting table 18 is lifted by the Z-axis driving device to bring the substrate 6 into the substrate mounting table. Place on top. Thereafter, the substrate 6 is vacuum-sucked to the substrate mounting table 18.

Step 2 is a step of flattening the warped substrate 6. When the thickness of the substrate 6 is thick and when the substrate is warped upward, the vacuum suction is insufficient. The substrate pressing jig 20 in the retracted position is moved onto the substrate 6 by the air cylinder 22, and then the substrate pressing jig 20 is lowered by the Z-axis air cylinder 21, and the substrate 6 is pressed by eight protrusions. When the substrate is warped upward, vacuum suction works relatively well, but the substrate pressing jig 20 presses the substrate 6 to further flatten the substrate. After the planarization operation of the substrate 6 is completed, the substrate pressing jig 20 is retracted to the initial position.

Step 3 is a step of moving the substrate 6 below the mask 44. During the movement, the position mark of the substrate 6 is read by the substrate position measuring camera (19b, 19c), and the reference coordinates of the substrate 6 are calculated. Next, two position marks on the mask 44 are read by the mask position measuring camera 19a, the position coordinates of the mask 44 are calculated, and the difference from the set value is corrected by moving the XYΘ table. By this correction, the position mark on the substrate 6 and the position mark on the mask have a predetermined positional relationship. That is, the electrode of the substrate 6 on which the ball is mounted and the opening of the mask 44 are arranged at the correct positions.
Since there are two substrate position measuring cameras, the position mark on the substrate 6 can be read with little movement in the Y direction, the time for searching for the position mark can be greatly reduced, and the tact time can be greatly reduced.

Step 4 is a process of bringing the mask 44 into close contact with the substrate 6. The substrate 6 is raised and brought into close contact with the lower surface of the mask 44. With the suction force generation device 16 in close contact with the substrate mounting table 18, the suction force generation device 16 is operated so that the mask 44 is adsorbed to the substrate 6. The suction force generation device 16 continues to operate until the step of separating the mask 44 from the substrate 6.

  Step 5 is a step of dropping the solder ball into the opening of the mask 44. First, the squeegee 43 is moved above the mask 44 and the squeegee 43 is lowered by the air cylinder 41. The solder ball is dropped into the opening of the mask 44 by moving on the mask 44 while pushing the solder ball supplied from a solder ball supply device (not shown) with the squeegee 43. Further, the squeegee is moved to drop the solder ball from the substrate 6 into the ball storage recess (not shown).

  Step 6 is a process of removing the solder balls remaining on the mask 44. The squeegee 43 used for dropping the ball is raised, the other residual ball removing squeegee 43 is lowered, and the remaining ball is swept down and dropped into the other ball storage recess (not shown). Thereafter, the two squeegees are retracted to a predetermined position.

  Step 7 is a solder ball pressing step. The ball pressing head 34 is moved onto the mask 44 and lowered to press the solder ball dropped into the opening of the mask 44 against the substrate 6. The surface of the solder ball in contact with the substrate 6 is flattened and temporarily fixed. When the solder balls are pressed against the electrodes (including bumps) of the substrate 6 and flux is applied to the electrodes, the adhesive force also becomes a temporary fixing force. Further, when the flux is solid at room temperature, the adhesive force can be increased by raising the flux to a critical temperature or higher.

  Step 8 is a process of separating the substrate 6 and the mask 44. After the suction force of the suction force generating device 16 with respect to the mask 44 is weakened, the substrate 6 and the mask 44 are separated. Specifically, the suction force generating device 16 is turned off after being turned off. When the attracting force generating device 16 is an electret, a permanent magnet or the like, the attracting force generating device 16 is sufficiently lowered with the mask 44 in close contact with the substrate 6 to reduce the attracting force exerted on the mask 44, and then the substrate 6. Is separated from the mask 44. When the substrate 6 is separated from the mask 44 in a state where the suction force acting on the mask 44 is strong, the mask 44 is deformed.

  Step 9 is a process for inspecting whether or not the solder ball is completely dropped. When it is incomplete, it enters a repair process, and when it is complete, it enters a reflow process.

  In the present invention, the embodiment in which the number of substrate position measurement cameras a is two has been described, but it is obvious that three or more may be used. If the number of substrate position measuring cameras 19a is increased, the cost of the apparatus increases, but the tact time of the ball mounting process can be shortened and the installation size of the ball mounting apparatus can be reduced. However, since the substrate 6 on which the solder balls are mounted cannot be considered to be very large like the display device substrate, it is preferable to attach two to four substrate position measuring cameras a to the fixed base 23.

In the present invention, the cleaning device 5 has been described as cleaning the mask 44 with cleaning paper, but cloth may be used in addition to paper. Further, the present invention includes impregnating a cleaning sheet with a cleaning agent and cleaning the mask 44 in a cleaning liquid.

  In the present invention, the horizontal pressure adjusting device for adjusting the horizontal angle of the ball pressing head in the ball pressing device is a device capable of adjusting the angle of 0.3 second, preferably 0.1 second. The angle can be adjusted. In the present invention, the position measuring camera is described as a CCD, but a MOS type image sensor may be used.

  In the present invention, the effective dimension of the substrate mounting table on which the substrate is mounted is a dimension that allows the substrate 6 to be mounted and vacuum-sucked and fixed, and is a size that can mount at least a 12 inch (30 cm) semiconductor wafer. The upper limit is not specifically limited, but is practically 20 inches (50 cm).

  Also, if the solder ball has a large diameter, it can be mounted by a conventional ball mounting apparatus. Therefore, in the present invention, the solder ball has a diameter of 200 μm or less. However, when the ball diameter is reduced to 30 μm or less, it becomes difficult to drop the ball into the opening of the mask. For this reason, in the present invention, the diameter of the solder ball is suitably 30 to 200 μm. More preferably, it is 50 to 200 μm.

  The present invention is a newly developed substrate mounting device in which a suction force generating device is arranged so as to be movable up and down. This substrate mounting device is a mounting device that mounts a mask in close contact with the substrate. Can be widely put into practical use.

It is a top view of a ball mounting apparatus. It is an elevation view of a ball mounting device. It is an elevational view of a ball pressing head. It is an elevation view of a substrate mounting device. It is a side view of a substrate mounting apparatus. It is a flowchart of ball mounting.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Substrate mounting device, 2 ... Substrate flattening device, 3 ... Ball pressing device, 4 ... Ball dropping device, 5 ... Cleaning device, 6 ... Substrate, 7 ...・ X-axis rail for substrate placement device, 8... Y-axis rail for substrate placement device, 9... XY table, 10... Θ rotation motor, 11. Axis driving device, 13 ... XYΘZ table, 14 ... Suction device receiving plate, 15 ... Z-axis air cylinder, 16 ... Suction force generating device, 17 ... Substrate mounting table fixing bracket, 18 ... Substrate mounting table, 19a ... Mask position measuring camera, 19b, 19c ... Substrate position measuring camera, 20 ... Substrate pressing jig, 21 ... Z-axis air cylinder, 22 ... Air cylinder, 23 ... Fixing base, 24 ... Stand, 2 5 ... support base, 26 ... X rail, 27 ... motor, 28 ... moving substrate, 29 ... motor, 30 ... ball screw, 31 ... mounting jig with rail, 32 ... Θ rotation drive device mounting jig, 33... Z-axis drive motor, 34... Ball pressing head, 34 a... Ball pressing head mounting plate, 35. 37 ... Y-axis rotating device, 37a ... adjustment knob, 37b ... vernier, 38 ... X-axis rotating device, 39 ... horizontal beam, 40 ... vertical beam, 41. ..Air cylinder, 42 ... Slider, 43 ... Squeegee, 43a ... Squeegee mounting jig, 44 ... Mask, 45 ... Mask holding jig, 46 ... Cleaning device base, 48 ... Y rail, 49 ... support, 50 ... cleaning Device frame, 51a... Supply 1 roller, 51b .. take-up roller, 52... Cleaning paper, 53... Leveling adjustment device, 54.

Claims (1)

The substrate mounting apparatus X-axis rail and the substrate mounting apparatus Y-axis rail are disposed at right angles, and an XY table is mounted on them, and a Θ rotation motor is disposed on the XY table. An XYΘ table is provided on the motor, a Z-axis drive device is provided on the XYΘ table, and an XYΘZ table is mounted on the Z-axis drive device, and the substrate mounting table fixing bracket is provided on the XYΘZ table. The substrate mounting table on which the substrate is mounted is fixed to the XYΘZ table by the substrate mounting table fixing bracket, the mask is fixed to the fixing base, and the opening of the mask superimposed on the substrate A suction force generating device that sucks the mask into which the solder balls are dropped and sucks the mask and the substrate is provided between the XYΘZ table and the substrate mounting table. In the substrate mounting device provided between,
The substrate mounting apparatus, wherein the suction force generating device is installed so as to be vertically movable between the substrate mounting table and the XYΘZ table by a Z-axis air cylinder fixed to the XYΘZ table.