TW202218512A - Ball loading method and ball loading apparatus including a flux printing process (steps S1 to S4) for printing a flux on an electrode by using a gravure offset printing method - Google Patents

Abstract

This invention relates to a ball loading method for loading a conductive ball on a predetermined electrode of a wafer (substrate). The ball loading method includes a flux printing process (steps S1 to S4) for printing a flux on an electrode by using a gravure offset printing method and a ball loading process (steps S5 to S8) for loading a ball on the flux. This invention may provide a ball loading method capable of achieving a higher fineness ball loading.

Description

Ball mounting method and ball mounting device

Field of Invention

The present invention relates to a ball mounting method and a ball mounting apparatus for mounting conductive balls on a substrate.

Background technique

The bumps of electrodes provided on substrates such as silicon wafers and printed wiring boards are formed by mounting conductive balls such as solder balls on the electrodes, and melting the balls. When mounting conductive balls, as described in Patent Document 1 and Patent Document 2, flux is applied to electrodes by a screen printing method, and balls are placed on the flux. Patent Document 1 and Patent Document 2 disclose a ball mounting device including a screen printing portion for printing flux on electrodes of a substrate using a mask, and a ball mounting device for mounting a ball on a ball mounting portion of the flux.

On the other hand, as described in Patent Document 3 and Patent Document 4, as a technique of forming a wiring pattern on a substrate, a technique of printing a wiring material on a substrate by a gravure offset printing method is known. Patent Document 3 discloses a gravure offset printing method in which an ink constituting a wiring material is transferred from a gravure offset printing plate to a substrate through a rubber cylinder. In Patent Document 4, a method of printing a fine wiring pattern by the gravure offset printing method using the technique of Patent Document 3 is disclosed. Among the wiring printing methods, a letterpress printing method, an ink jet printing method, a gravure printing method, a screen printing method, and the like are used in accordance with the wiring pattern, production speed, and the like. In the case where fine wiring can be printed and the printing accuracy is emphasized, the gravure offset printing method is used. prior art literature Patent Literature

[Patent Document 1] Japanese Patent Laid-Open No. 2019-67991 [Patent Document 2] Japanese Patent Laid-Open No. 2008-288515 [Patent Document 3] Japanese Patent Laid-Open No. 2014-73653 [Patent Document 4] International Publication WO2014/112557

Summary of Invention The problem to be solved by the invention

In recent years, with the progress of miniaturization and high density of electronic components, the electrodes are formed smaller and the interval (pitch) between the electrodes is shortened. However, in the screen printing method, it is impossible to place fine ball printing flux in such a narrow pitch range. The reason for this is because there is a limit to improving the accuracy of printing in the screen printing method. Therefore, in the ball mounting apparatus for printing the flux by the screen printing method, there is a problem of hindering the manufacture of electronic components intended for miniaturization and high density.

An object of the present invention is to provide a ball loading method and a ball loading device that can achieve high precision ball loading. means of solving problems

In order to achieve this object, the ball mounting method of the present invention is a ball mounting method for mounting conductive balls on predetermined electrodes of a substrate, and includes a flux printing step of printing flux on the electrodes by a gravure offset printing method. ; and a ball mounting process, wherein the ball is mounted on the flux.

The ball mounting device of the present invention is a ball mounting device for mounting conductive balls on predetermined electrodes of a substrate, and includes a gravure offset printing section, a rotary transfer body that transfers flux from a gravure offset gravure plate, and transfers the help Solder is printed on the electrodes; and a ball mounting portion mounts the balls on the flux. Invention effect

In the present invention, the flux is printed on the electrodes of the substrate with high precision by the gravure offset printing method. Therefore, according to the present invention, it is possible to provide a ball mounting method and a ball mounting apparatus capable of achieving high-precision ball mounting.

Form for carrying out the invention

Hereinafter, an embodiment of the ball mounting method and the ball mounting apparatus according to the present invention will be described in detail with reference to FIGS. 1 to 7 . (Explanation of the ball mounting device) The ball mounting apparatus 1 shown in FIG. 1 is an apparatus for implementing the ball mounting method of the present invention, and mainly has three functional parts. These functional parts are: the loading & unloading part 2 located in the center part in FIG. 1 , the gravure offset printing part 3 located on the left side in FIG. 1 , and the ball mounting part 4 located on the right side in FIG. 1 . In addition, this ball mounting apparatus 1 is installed in a clean room or an environment equivalent to a clean room.

The loading and unloading unit 2 has a function of taking out a substrate without balls as a workpiece from the workpiece storage container 6, or storing a substrate with mounted balls in the workpiece storage container 6; The part 4 performs the function of receiving and delivering the substrate. The substrate is, for example, a silicon wafer, a printed wiring board, or the like. The ball mounting device 1 of this embodiment uses a silicon wafer (hereinafter simply referred to as a wafer) as a substrate. As the workpiece storage container 6 for accommodating wafers, a so-called closed-type cassette called FOUP (Front Opening Unify Pod) can be used. The workpiece storage container 6 has wafers in the vicinity of the loading and unloading section 2 The entrance and exit (not shown). The wafer entrance and exit are arranged so as to point to the loading & unloading unit 2. In this embodiment, as shown in FIG. The storage container 6A, and the second workpiece storage container 6B that accommodates a plurality of wafers 9 on which the balls are mounted.

Although the details of the ball mounting apparatus 1 of this embodiment will be described later, the flux 11 is printed on the electrode formation region 8a of the wafer 8 on which the ball is not mounted by the gravure offset printing method (see FIGS. 5A to 5C ). A ball 12 (see FIG. 4 ) is mounted on the 11 . As shown in FIG. 2 , the loading and unloading unit 2 includes a transfer robot 13 composed of an articulated robot, and a pre-aligner 14 .

The transfer robot 13 includes a first transfer arm 15 that attracts the lower surface of the wafer 8 and holds the wafer 8 , and moves the first transfer arm 15 in the horizontal and vertical directions to transfer the wafer 8 . The pre-aligner 14 is for aligning the position of a flat notch (not shown) formed in the outer peripheral portion of the wafer 8 with a predetermined position, and includes a turntable 14a on which the wafer 8 is placed and rotated, and A sensor 14b that detects flat cuts.

(Description of gravure offset printing section) As shown in FIG. 2 , the gravure offset printing unit 3 includes: a first wafer stage 16 provided in the vicinity of the boundary with the loading & unloading section 2; The carrier 17; the workpiece table slide member 18 which is provided near the first wafer transfer device 17 and holds the wafer 8 at the printing position; the blanket cylinder 19; the doctor blade 20; the plate slider 21; The first wafer stage 16 has three suction pins 16a. These suction pins 16a have a function of suctioning the lower surface of the wafer 8 to hold the wafer 8, and a function of lifting and lowering.

The first wafer transfer device 17 includes a second transfer arm 17a for sucking the lower surface of the wafer 8 and holding the wafer 8, an X slider 17b for moving the second transfer arm 17a in two horizontal directions, and Y slider 17c. Here, the two directions in the horizontal direction refer to the X direction (the horizontal direction in FIG. 1 ) in which the gravure offset printing portion 3 and the ball mounting portion 4 are aligned, and the Y direction orthogonal to the X direction in the horizontal direction. direction. The X slider 17b moves the Y slider 17c and the second conveyance arm 17a in the X direction. The Y slider 17c moves the second conveyance arm 17a in the Y direction.

The workpiece table slide member 18 has a flat support surface 18a that attracts and holds the wafer 8, and three lift-type suction pins 18b, and is configured to be movable in the X direction and the Y direction. Above the workpiece table sliding member 18, a plurality of alignment cameras 23 that can photograph the wafer 8 on the workpiece table sliding member 18 from above are provided. The stage slide member 18 moves in the X direction and the Y direction according to the image of the wafer 8 captured by the alignment camera 23 so that the wafer 8 is arranged at a predetermined printing position.

The blanket cylinder 19 is a cylinder in which a rubber blanket 19a is wound around the outer periphery, and has a function of rotating around an axis C1 extending in the X direction, a function of moving in the Y direction, and a predetermined descending position. and the function of raising and lowering between the raised positions. In this embodiment, the blanket cylinder 19 corresponds to what is called a "rotary transfer body" in the present invention. The descending position of the blanket cylinder 19 is a position where the blanket cylinder 19 contacts the wafer 8 on the table slide member 18 and the gravure plate 24 for gravure offset printing on the plate slider 21 to be described later. The ascending position is a position where the blanket cylinder 19 is spaced upward from the wafer 8 and the gravure 24 for offset gravure printing. The blanket cylinder 19 of the present embodiment is arranged between the workpiece table sliding member 18 and the plate slider 21 to be described later.

The scraper 20 is provided with the blade 20a which consists of a strip|belt-shaped board material extended in the X direction. The blade 20a can swing freely about the axis 2C extending in the X direction. The scraper 20 has a function of swinging the blade 20a, and is configured to move in the Y direction integrally with the blanket cylinder 19 . The squeegee 20 of this embodiment moves in the Y direction (upper side in FIG. 2 ) in a state where the lower end of the blade 20a is in contact with the upper surface of the gravure plate 24 for gravure offset printing, which will be described later, and the lower end of the blade 20a contacts the gravure offset printing plate. The gravure 24 for printing moves to the other side (lower side in FIG. 2 ) in the Y direction in a state of being separated.

The plate slider 21 is for positioning and holding the intaglio plate 24 for gravure offset printing (hereinafter simply referred to as the intaglio plate 24 ) at a predetermined position. As shown in FIG. 5A , the intaglio plate 24 is formed as a flat plate-like plate, and concave portions 25 are respectively provided on the upper surface of the intaglio plate 24 at positions corresponding to the plurality of electrodes 8 b of the wafer 8 . The recessed part 25 is formed in the printing area 24a of the gravure 24 (refer FIG. 2). The material forming the gravure 24 is glass, synthetic resin, metal, or the like. A dispenser 22 for supplying the flux 11 to the gravure 24 is arranged above the plate slider 21 .

(explanation of the ball mounting part) As shown in FIGS. 2 and 3 , the ball mounting portion 4 includes a second wafer stage 31 provided in the vicinity of the boundary with the loading & unloading portion 2 , and a second wafer stage 31 for positioning the second wafer stage 31 in the operating range. A circular transfer device 32, a wafer stage 33 that is provided in the vicinity of the second wafer transfer device 32 and holds the wafer 8 at the ball mounting position, a ball arrangement mask 34, a ball insertion portion 35, and a wiper plate 36 etc. The second wafer stage 31 has the same configuration as the first wafer stage 16, and has three liftable suction pins 31a.

The second wafer transfer device 32 has the same configuration as the first wafer transfer device 17, and includes a third transfer arm 32a, an X slider 32b, and a Y slider 32c. The third transfer arm 32 a attracts the lower surface of the wafer 8 and holds the wafer 8 . The X slider 32b moves the Y slide 32c and the third conveyance arm 32a in the X direction. The Y slider 32c moves the third conveyance arm 32a in the Y direction.

As shown in FIG. 3, the wafer stage 33 has a flat upper surface 33a, and has a plurality of air holes 41 opening on the upper surface 33a. The air hole 41 communicates with the suction chamber 42 provided at the lower part of the wafer stage 33 and the space above the wafer stage 33 . An air suction device (not shown) is connected to the suction chamber 42 . In addition, the wafer stage 33 is provided with a plurality of lift-type suction pins (not shown in the figure) in order to receive the wafer 8 without the balls mounted on the third transfer arm 32a or transfer the wafer 9 with the balls mounted to the third transfer arm 32a. Show).

As shown in FIG. 3 , the ball arrangement mask 34 is formed to cover the wafer stage 33 from above, is arranged above the wafer stage 33 , and is configured to be movable in the vertical direction. As shown in FIG. 4 , the ball arrangement cover 34 has a plurality of through holes 43 into which the balls 12 are inserted. The through holes 43 are respectively provided at positions corresponding to the plurality of electrodes 8 b of the wafer 8 . The hole diameter of the through hole 43 is such that only one ball 12 can be inserted. The thickness of the ball arrangement cover 34 is such that the upper ends of the balls 12 inserted into the through holes 43 are located in the vicinity of the upper surface of the ball arrangement cover 34 . In addition, although not shown in the figure, a ball suction device that attracts the remaining balls 12 on the ball arrangement cover 34 and then removes them may be provided in the vicinity of the ball arrangement cover 34 .

The ball insertion portion 35 is formed in a cylindrical shape, and is connected to a not-shown ball supply device. The balls 12 are fed into the ball insertion portion 35 from above by the ball feeding device. The balls 12 are conductive balls having conductivity such as solder balls. In addition, the ball insertion portion 35 has a function of rotating around an axis C3 extending in the vertical direction, and a function of moving in the X direction, the Y direction, and the vertical direction. A brush scraper 36 is provided at the lower end of the ball insertion portion 35 . The brush scraper 36 is a cylindrical brush member whose outer diameter gradually increases toward the lower side.

(Explanation of ball mounting method) Next, the ball mounting method according to the present invention will be described with reference to the flowchart shown in FIG. In order to implement the ball mounting method according to the present invention, first, the wafer 8 is transferred to the gravure offset printing section 3 (step S1 ). In this process, first, the wafer 8 is taken out from the first workpiece storage container 6A by the transfer robot 13 and then transferred to the pre-aligner 14 . After the circumferential position of the wafer 8 is corrected by the pre-aligner 14 , the wafer 8 is transferred from the pre-aligner 14 to the first wafer stage 16 by the transfer robot 13 . This transfer is performed by retreating the first transfer arm 15 of the transfer robot 13 with respect to the wafer 8 in a state where the wafer 8 is held by the three suction pins 16 a.

Next, the wafer 8 is transferred from the first wafer stage 16 to the second transfer arm 17a of the first wafer transfer device 17, and the second transfer arm 17a is moved to the upper side of the workpiece table slide member 18, and then The wafer 8 is transferred to the work table slide member 18 . When the wafer 8 is transferred from the first wafer stage 16 to the second transfer arm 17a, the second transfer arm 17a is inserted under the wafer 8, and in this state, the suction of the three suction pins 16a is released. its decline. When the wafer 8 is transferred from the second transfer arm 17a to the workpiece table sliding member 18, the three suction pins 18b of the workpiece table sliding member 18 are raised to push the wafer 8 upward from the second transfer arm 17a. In this state, the second transfer arm 17 a is retracted from the wafer 8 . Next, the suction pins 18 b are lowered so that the wafer 8 is placed on the upper surface of the work table slide member 18 in a state where the wafer 8 is suctioned to the suction pins 18 b.

In this way, after the wafer 8 is carried into the gravure offset printing section 3, the flux 11 is supplied to the gravure 24 (step S2). In this process, first, the flux 11 is dropped onto the gravure 24 by a predetermined amount by the dispenser 22 . Next, as shown in FIG. 5A, the blade 20a of the scraper 20 is inclined so that the lower end of the blade 20a contacts the gravure 24, and the scraper 20 and the blanket cylinder 19 located at the raised position are directed in one direction of the Y direction (the same as the workpiece in the Y direction). the direction in which the table slide members 18 are separated). At this time, the blade 20a is inclined so that the downstream side in the moving direction is positioned downward. The concave portion 25 is filled with the flux 11 by the blade 20a traversing the intaglio plate 24 in the Y direction.

After the scraper 20 is moved to one end in the Y direction, the blade 20a is shaken to separate the lower end from the gravure plate 24, and the blanket cylinder 19 is positioned at the lowered position, and is pressed against the gravure plate 24 to move the other side in the Y direction. (direction toward the workpiece table slide member 18 ). At this time, the blanket cylinder 19 rotates by moving in the Y direction while being in contact with the gravure 24 . Next, as shown in FIG. 5B , the flux 11 in the recessed portion 25 is transferred to the blanket cylinder 19 along with the rotation of the blanket cylinder 19 (step S3 ).

By rotating the blanket cylinder 19 on the gravure 24 to the other end in the Y direction, the flux 11 is transferred from all the recesses 25 to the blanket 19a of the blanket cylinder 19 . Next, the blanket cylinder 19 continues to move in the Y direction, and turns on the wafer 8 as shown in FIG. 5C . The flux 11 on the blanket cylinder 19 is transferred from the blanket 19a to the wafer 8 by moving the blanket cylinder 19 toward the other side of the Y direction while rotating on the wafer 8 while pressing the blanket cylinder 19 toward the wafer 8. electrode 8b (step S4). In this embodiment, the processes shown in step S1 to step S4 correspond to the "flux printing process" of the ball mounting method of the present invention.

In this way, after the flux 11 is printed on the wafer 8 by the gravure offset printing unit 3, the wafer 8 is transferred to the ball mounting unit 4 (step S5). In this process, first, the wafer 8 on the work table sliding member 18 is transferred to the first wafer stage 16 by the first wafer transfer device 17 , and the wafer 8 is transferred from the first wafer stage 16 by the transfer robot 13 . The circular stage 16 is transferred to the pre-aligner 14 . In the pre-aligner 14, the wafer 8 after the printing of the flux is rotated, and the circumferential position of the wafer 8 is corrected. After that, the wafer 8 is transferred from the pre-aligner 14 to the ball mounting unit 4 by the transfer robot 13 (step S5 ).

In this transfer, the wafer 8 is transferred from the pre-aligner 14 to the second wafer stage 31 by the transfer robot 13 , and the wafer 8 is moved into the ball arrangement mask by the second wafer transfer device 32 . The lower part of 34 is then transferred to wafer stage 33 and performed. At this time, by forming the suction chamber 42 of the wafer stage 33 to a negative pressure in advance, the air is sucked from the air hole 41 , and the wafer 8 is sucked on the upper surface 33 a of the wafer stage 33 . In this way, after the wafer 8 is placed on the wafer stage 33, the ball arrangement mask 34 is lowered and attached to the upper surface of the wafer 8 (step S6).

Next, the ball insertion portion 35 is moved over the ball arrangement cover 34 , and the balls 12 are supplied into the ball insertion portion 35 . Next, the ball insertion portion 35 is rotated, and the ball insertion portion 35 is moved in the X direction and the Y direction along the ball arrangement cover 34 with the brush blade 36 sweeping the balls 12 . By operating the ball insertion portion 35 in this manner, as shown in FIG. 4 , the balls 12 are inserted into the through holes 43 of the ball arrangement cover 34 (step S7 ). The balls 12 are pressed from above by the other balls 12 after being put into the through holes 43, and adhere to the flux 11 in a state of being slightly pressed against the flux 11 printed on the electrode 8b. After the balls 12 are placed in all the through holes 43, the ball insertion portion 35 is moved out of the ball arrangement cover 34, and the remaining ball arrangement cover 34 is removed by, for example, a suction device. Ball 12. Next, the ball arrangement mask 34 is lifted upward from the wafer 8 (step S8 ).

After that, the wafer 9 with the ball mounted on the wafer stage 33 is replaced and mounted on the third transfer arm 32 a of the second wafer transfer device 32 , and then transferred to the second wafer transfer device 32 by the second wafer transfer device 32 . Wafer stage 31 . Next, the wafer 8 is unloaded from the ball mounting section 4 by the transfer robot 13 (step S9 ) and stored in the second workpiece storage container 6B, thereby completing the mounting of the balls 12 for one wafer 8 . The wafer 9 in the second workpiece storage container 6B is wired in the region where the balls 12 are mounted. In this embodiment, steps S5 to S8 correspond to the "ball mounting step" of the ball mounting method of the present invention.

According to the ball mounting method and the ball mounting apparatus 1 of the present embodiment, when the flux 11 is printed on the electrode 8b of the wafer 8, as shown in FIG. The pitch L between them is 100 μm or less.

According to the ball mounting method and the ball mounting apparatus 1 of the present embodiment, the flux 11 can be printed on the electrodes 8b of the wafer 8 with high accuracy by the gravure offset printing method. Therefore, it is possible to provide a ball mounting method and a ball mounting device that can achieve high-precision ball mounting.

The gravure plate 24 for gravure offset printing of the present embodiment is a lithographic plate. Therefore, the flux 11 can be transferred from the gravure 24 to the blanket cylinder 19 with high accuracy without skewing. Therefore, according to the present embodiment, it is possible to print the flux 11 on the wafer 8 so as to further improve the printing accuracy. According to this embodiment, for a workpiece whose electrode outer diameter ψ of wafer 8 is 30 μm, pitch is 50 μm, and total pitch is 295 mm (in the effective area of a ψ 12-inch wafer), dot diameter ψ 20 μm can be printed with a printing position accuracy of ±5 μm of flux 11. In other words, according to the present embodiment, the maximum accuracy of conventional screen printing can be achieved with a dot diameter of 60 μm or less and a pitch of 100 μm or less.

The gravure offset printing section 3 of the above-described embodiment is one that performs gravure offset printing using the gravure 24 for gravure offset printing consisting of a lithographic plate. However, the present invention is not limited to this. In other words, the gravure offset printing part 3 may also use other gravure offset printing methods using non-lithographic gravure. Even in such a case, the ball mounting method of the present invention can be carried out by a process in which the ink material is caused to contact and rotate the transfer body (blanket cylinder 19 ) and the printing pattern portion of the non-planographic gravure plate (Flux 11) the process of transferring the transfer body to the surface of the transfer body; the process of pressing the transfer body to the object to be printed (for example, the wafer 8) to transfer the printing pattern to the object to be printed; and the process of mounting the ball 12 on the object to be printed process.

1: Ball carrying device 2: Loading & Unloading Department 3: Gravure offset printing department 4: Ball mounting part 6 (6A, 6B): Workpiece storage container 8(9): Wafer (substrate) 8a: Electrode formation area 8b: Electrodes 11: Flux 12: Ball 13: Transfer robot 14: Pre-aligner 14a: Rotary table 14b sensor 15: 1st transfer arm 16: The first wafer stage 16a: adsorption pin 17: The first wafer transfer device 17a: 2nd transfer arm 17b: X Slider 17c: Y Slider 18: Workpiece table sliding member 18a: Support surface 18b: adsorption pin 19: Rubber roller (rotary transfer body) 19a: Blanket 20: scraper 20a: Blades 21: Edition Slider 22: Dispenser 23: Align the camera 24: Gravure for gravure offset printing 24a: Printing area 25: Recess 31: 2nd wafer stage 31a: adsorption pin 32: Second wafer transfer device 32a: 3rd transfer arm 32b:X Slider 32c: Y Slider 33: Wafer stage 33a: upper surface 34: Mask for ball arrangement 35: Ball insertion section 36: Brush scraper 41: Air holes 42: Attraction Room 43: Through hole C1, C2, C3: axis D: point diameter L: point spacing S1 to S4: Steps (Flux Printing Process) S5 to S8: Step (Ball Mounting Process) S9: Steps

FIG. 1 is a block diagram showing the configuration of a ball mounting apparatus for implementing the ball mounting method according to the present invention. FIG. 2 is a plan view showing the configuration of the ball mounting device. FIG. 3 is a cross-sectional view showing the structure of the ball mounting portion. FIG. 4 is an enlarged cross-sectional view showing a part of the ball mounting portion. 5A is a cross-sectional view for explaining the operation of the gravure offset printing section. 5B is a cross-sectional view for explaining the operation of the gravure offset printing section. 5C is a cross-sectional view for explaining the operation of the gravure offset printing section. FIG. 6 is a flow chart for explaining the ball loading method of the present invention. FIG. 7 is an enlarged plan view showing the flux after printing.

S1 to S4: Steps (Flux Printing Process)

S5 to S8: Step (Ball Mounting Process)

S9: Steps

Claims (4)

A ball mounting method, which is a ball mounting method for mounting conductive balls on predetermined electrodes of a substrate, characterized by comprising: a flux printing process, using a gravure offset printing method to print flux on the aforementioned electrodes; and In the ball mounting step, the ball is mounted on the flux. A ball mounting device, which is a ball mounting device for mounting conductive balls on predetermined electrodes of a substrate, characterized in that it has: a gravure offset printing section for printing flux onto the aforementioned electrodes using a rotary transfer body that transfers flux from a gravure for offset gravure; and The ball mounting portion mounts the ball on the flux. The ball mounting device according to claim 2, wherein the gravure plate for gravure offset printing is a lithographic plate. The ball mounting device according to claim 2 or 3, wherein the dot diameter of the flux printed on the electrodes is 60 μm or less, and the pitch is 100 μm or less.

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