JP5243482B2 - Ball mounting method - Google Patents

Description

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

In the semiconductor integrated circuit, the size and interval of the bumps are miniaturized, and the diameter of the wafer is increased to 12 inches or the like. The ball mounting apparatus has a problem to cope with the increase in the density of electronic circuits and the increase in the size of the substrate (increase in the number of elements taken in a single process).
As a method for mounting solder balls on a substrate such as an electronic circuit board or a semiconductor wafer, a ball dropping method is disclosed (see Japanese Patent Laid-Open Nos. 2000-49183 and 9-148332). Also, a method using a substrate observation camera and a mask observation camera is disclosed as a method for observing the position of a substrate and a mask (see Japanese Patent Application Laid-Open No. 3-20090).

However, the conventional ball dropping device has a drawback that when the ball diameter is 200 μm or less, the solder ball is not dropped, that is, the opening of the unloaded mask increases. In particular, this tendency is further increased when the size of the substrate exceeds 8 inches (20 cm). Further, since the conditions for pressing the solder balls dropped into a predetermined position on the substrate vary, the solder balls cannot be pressed uniformly, so that there is a defect that a ball having insufficient temporary fixing force to the substrate or a solder ball that is excessively pressed is generated.

In the conventional substrate position observation method, the camera is attached to an XYZ driving device, and in a ball mounting apparatus that processes a substrate having a length of 300 mm or more, the camera is moved onto a position mark provided on the substrate. For this reason, the moving distance becomes longer. There is a drawback that a large space is required to secure a space in which the XYZ driving device operates. An increase in the installation floor area of the ball mounting device is not preferable because it is installed in a clean room.
Thus, it cannot be said that the conventional ball mounting apparatus can be adapted to the needs for the miniaturization of the solder balls and the enlargement of the substrate.
JP 2000-49183 A See JP-A-9-148332 JP-A-3-200999

The present invention solves such a problem, and an object of the present invention is to provide a ball mounting method capable of mounting fine solder balls on a large substrate at an industrial level.

The present invention relates to a ball mounting device having a substrate mounting device, a substrate flattening device, a ball dropping device, and a cleaning device, wherein the X axis rail for the substrate mounting device and the Y axis rail for the substrate mounting device are provided. Arranged at a right angle, on which an XY table is mounted, and on this XY table a Θ rotation motor is arranged, and an XYΘ table is provided between the Θ rotation motor and the Z-axis drive, and this An XYΘZ table is mounted on the shaft driving device, and the XYΘZ table is provided on a substrate mounting device on which a substrate mounting table fixing bracket for fixing the substrate mounting table is mounted and a substrate pressing jig. A substrate flattening device that presses a plurality of portions of the substrate 6 with a plurality of protrusions, and a solder ball supplied onto the mask superimposed on the substrate with a squeegee while moving the mask Solder using a ball drop device that drops a solder ball into the opening, and a ball mounting device that includes a Y-axis rail provided so that it can move below the mask and cleans the mask that has dropped the ball. In the ball mounting method of mounting the ball on the substrate,
A step of vacuum-adsorbing the substrate on the substrate mounting table after mounting the substrate on the substrate mounting table;
Lowering the substrate pressing jig with an apparatus for vertical movement and pressing operation, pressing the substrate with the substrate pressing jig, and flattening the substrate;
Moving the substrate below the mask;
Raising the substrate and bringing it into close contact with the lower surface of the mask;
Dropping a solder ball having a diameter of 30 to 200 [mu] into the opening of the mask;
Removing solder balls remaining on the mask;
Separating the substrate and the mask;
A step of cleaning the mask with a cleaning device ;
It is characterized by having.

  Further, the present invention provides a ball pressing device, a leveling adjustment device for adjusting a horizontal angle of the ball pressing head, and a substrate flattening for flattening a substrate placed on the substrate mounting platform. And a device.

  Furthermore, the present invention is characterized in that an effective dimension of a substrate mounting table on which a substrate is mounted is such that at least a 12-inch semiconductor wafer can be mounted, and a diameter of a solder ball is 200 microns or less. To do.

The present invention has the following effects by adopting the above configuration.
(1) A ball mounting method capable of mounting fine solder balls on a large substrate at an industrial level has been provided.
(2) A finer solder ball could be reliably dropped into the mask opening.
(3) The mask dirt was cleaned.

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.

  An object of the present invention is to mount fine solder balls on a large substrate. 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 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 also measures 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. In addition, the position of these protrusions is a mechanism that can move according to the dimensions of the substrate 6.

The ball pressing device 3 includes a ball pressing head 34 (see FIG. 3), a horizontality adjusting 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 33 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 is 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 corresponding to the solder ball. ing. The ball pressing mask on which the protrusions are formed 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 driven by a motor 27 is incorporated in the X rail, and the ball pressing device 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 squeegee 43 is composed of a pair of going and returning, each consisting of one air cylinder and two sliders.

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 knobs 37a and 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 display of vernier is insufficient. Therefore, the distance is measured by using 3 to 4 rangefinders 54 arranged on the substrate mounting device, and the distance is calculated with reference to the digital display. Make adjustments.

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 for the attractive force generating device 16 to manufacture the mask 44 with a ferromagnetic material and use a magnetic field as the attractive force.

  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 four distance meters 54 that can measure the four corners of the ball pressing head mounting plate 34a with the state in which 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 each of the four points. . That is, the four Z coordinates are adjusted so that the error is 5 μm or less. However, the error of the four 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 effective when the ball diameter is reduced, 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, the two position marks of 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 the XYΘ table. By this correction, the position mark on the substrate 6 and the position mark on the mask return to 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 43 is moved to drop the solder ball from the substrate 6 into a 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 43 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.

  In addition to the ball drop device, this device for substrate flattening and mask-substrate parallelism adjustment is also practical for other ball mounting methods that require high precision with respect to substrate flattening and mask-substrate parallelism. Can be

  Further, the structure having a plurality of fixed cameras can be put into practical use even in an apparatus that requires alignment of the substrate and the mask because the installation area of the apparatus is small even if the substrate becomes large.

  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)

A substrate mounting device, a substrate flattening device, a ball dropping device, and a ball mounting device having a cleaning device,
An X-axis rail for the substrate mounting apparatus and a Y-axis rail for the substrate mounting apparatus are disposed at right angles, and an XY table is mounted thereon, and a Θ rotation motor is disposed on the XY table. A table is provided between the Θ rotation motor and the Z-axis drive device, and an XYΘZ table is mounted on the shaft drive device, and the substrate placement table for fixing the substrate placement table to the XYΘZ table The substrate mounting apparatus to which the fixing bracket is attached;
The substrate flattening device for pressing a plurality of portions of the substrate 6 with a plurality of protrusions provided on the substrate pressing jig;
The above-described ball dropping device for dropping the solder ball into the opening of the mask while moving the solder ball supplied on the mask superimposed on the substrate with a squeegee; and
The solder ball is mounted on the substrate by using the ball mounting device comprising the cleaning device provided with a Y-axis rail provided so as to be moved below the mask and cleaning the dirt of the mask into which the ball has been dropped. In the ball mounting method,
  A step of vacuum-adsorbing the substrate on the substrate mounting table after mounting the substrate on the substrate mounting table;
Lowering the substrate pressing jig with a device for vertical movement and pressing operation, pressing the substrate with the substrate pressing jig, and flattening the substrate;
Moving the substrate below the mask;
Raising the substrate and closely contacting the lower surface of the mask;
Dropping the solder ball having a diameter of 30 to 200 μ into the opening of the mask;
  Separating the substrate and the mask;
  Cleaning the mask with the cleaning device;
A ball mounting method characterized by comprising: