JP4118285B2 - Solder ball mounting apparatus and solder ball mounting method - Google Patents

Description

The present invention relates to a solder ball mounting apparatus and a solder ball mounting method for mounting solder balls to be solder bumps on a printed wiring board.

Solder bumps are used for electrical connection between the package substrate and the IC chip. The solder bump is formed by the following process.
(1) A step of printing flux on connection pads formed on the package substrate.
(2) A step of mounting solder balls on connection pads on which flux is printed.
(3) A step of reflowing to form solder bumps from the solder balls.

In the process of mounting the solder balls on the connection pads described above, for example, the printing technique disclosed in Patent Document 1 is used. In this printing technique, as shown in FIG. 13A, a ball alignment mask 116 provided with an opening 116a is placed on the printed wiring board 30 at a position facing the connection pad 75, and a squeegee 124 is used for solder ball 78s. Was dropped on the connection pad 75.
JP 2001-267331 A

As ICs are highly integrated, the solder bumps on the package substrate are required to be further reduced in diameter and pitch. For this reason, the solder balls have a smaller diameter than sand grains having a diameter of less than 200 μmΦ, and the method of using the above-described ball alignment mask and squeegee together causes variations in the height of the solder bumps, resulting in a reduction in quality.

That is, when the diameter of the solder ball is reduced, the weight ratio with respect to the surface area is reduced, and the phenomenon of adsorption of the solder ball due to intermolecular force occurs. In the prior art, solder balls that tend to agglomerate are sent in contact with the squeegee, so that the solder balls are damaged and some of them are chipped. If a part of the solder ball is missing, the volume of the solder bump differs on each connection pad, so that the height of the solder bump varies as described above. If there is a solder bump having a small volume, thermal stress concentrates on the solder bump, resulting in a decrease in connection reliability.

Further, the surface of the printed wiring board is not flat. In particular, the build-up multilayer wiring board has large surface irregularities. When the ball alignment mask is placed on the printed wiring board, a recessed portion is formed in the ball alignment mask along the unevenness of the printed wiring board. When a solder ball having a diameter of less than 200 μmΦ is handled, the squeegee 124 cannot follow the depression on the ball alignment mask 116 having a depression as shown in FIG. It will be crushed as it is pushed, making it impossible to transport. Even if the squeegee is made of a soft material for this measure, as shown in FIG. 13C, the tip portion of the squeegee 124 is bent, and the solder ball 78s enters and is crushed. Thus, with the method using a squeegee, it has become difficult to mount a solder ball having a diameter of less than 200 μmΦ on the connection pad with a normal solder volume.

An object of the present invention is to provide a solder ball mounting apparatus and a solder ball mounting method capable of reliably mounting a solder ball having a diameter of less than 200 μm on a connection pad.

In order to achieve the above object, the invention of claim 1 is a solder ball mounting device for mounting a solder ball to be a solder bump on each connection pad in a connection pad region of a printed wiring board,
A ball alignment mask having a plurality of openings corresponding to connection pads of the printed wiring board;
A cylindrical member that is located above the ball alignment mask and collects solder balls directly under the opening by sucking air from the opening;
A moving mechanism for moving the cylindrical member in a horizontal direction, and moving the solder ball assembled on the ball alignment mask by moving the cylindrical member, through the opening of the ball alignment mask, A movement mechanism for dropping the solder ball onto the connection pad of the printed wiring board, and the opening of the cylindrical member is substantially rectangular,
The length of the side parallel to the cylindrical member moving direction of the opening is 1.1 to 4 times the length of the side parallel to the cylindrical member moving direction of the connection pad region,
A technical feature is that the length of the side of the opening perpendicular to the direction of movement of the cylindrical member is 1.1 to 4 times the length of the side of the connection pad region perpendicular to the direction of movement of the cylindrical member. To do.

According to a fourth aspect of the present invention, there is provided a ball alignment mask having a plurality of openings corresponding to connection pads in a connection pad region of a printed wiring board, and mounting solder balls serving as solder bumps on the connection pads of the printed wiring board. A solder ball mounting method,
The opening has a substantially rectangular shape, and the length of the side parallel to the cylindrical member moving direction of the opening is 1.1 to 4 with respect to the length of the side parallel to the cylindrical member moving direction of the connection pad region. A cylindrical member in which the length of the side perpendicular to the cylindrical member moving direction of the opening is 1.1 to 4 times the length of the side perpendicular to the cylindrical member moving direction of the connection pad region The solder balls are gathered on the ball alignment mask directly below the cylindrical member by being positioned above the ball alignment mask and sucking air with the cylindrical member.
By moving the cylindrical member in the horizontal direction, the solder balls assembled on the ball alignment mask are moved, and the solder balls are dropped onto the connection pads of the printed wiring board through the openings of the ball alignment mask. Is a technical feature.

According to the solder ball mounting apparatus of claim 1 and the solder ball mounting method of claim 4, the cylindrical member is positioned above the ball alignment mask, and the solder ball is sucked by sucking air from the opening of the cylindrical member. By assembling and moving the cylindrical member in the horizontal direction, the assembled solder balls are moved over the ball alignment mask, and the solder balls are moved to the connection pads of the printed wiring board through the openings of the ball alignment mask. Drop it. For this reason, a fine solder ball can be reliably mounted on all the connection pads of the printed wiring board. Further, since the solder ball is moved in a non-contact manner, unlike the case of using a squeegee, it can be mounted on the connection pad without damaging the solder ball, and the height of the solder bump can be made uniform. Furthermore, a solder ball can be appropriately placed on a connection pad even on a printed wiring board having a large undulation on the surface, such as a build-up multilayer wiring board. In addition, since the solder balls do not aggregate due to non-contact, one solder ball can be reliably mounted on the connection pad.

Further, since the opening of the cylindrical member is substantially rectangular, the solder balls can be assembled into a substantially rectangular shape, and the solder balls can be efficiently mounted on the connection pads in the connection pad region having a substantially rectangular shape. Here, the length of the side parallel to the cylindrical member moving direction of the opening of the cylindrical member is 1.1 to 4 times the length of the side parallel to the cylindrical member moving direction of the connection pad region. The length of the side perpendicular to the cylinder member movement direction is 1.1 to 4 times the length of the side perpendicular to the cylinder movement direction of the connection pad area. Solder balls can be collected. Here, when it is less than 1.1 times, it becomes impossible to mount solder balls on the connection pads in the outer peripheral portion of the connection pad region. If it exceeds four times, the solder balls are not collected at the center of the cylindrical member, and the solder balls cannot be mounted on the connection pads at the center of the connection pad region.

According to the solder ball mounting device of claim 2, (the length of the side parallel to the cylindrical member moving direction of the opening) / (the length of the side parallel to the cylindrical member moving direction of the connection pad region) The length of the side perpendicular to the cylindrical member moving direction) / (the length of the side perpendicular to the cylindrical moving direction of the connection pad region). For this reason, the solder balls can be collected so as to be long in the moving direction of the cylindrical member with respect to the substantially rectangular connection pad region, and the solder balls can be efficiently attached to the connection pads in the substantially rectangular connection pad region. Can be installed.

In the solder ball mounting apparatus according to claim 3, since the wind speed between the cylindrical member and the ball alignment mask is 5 to 35 m / sec, the solder balls are appropriately collected on the connection pad region, and the solder balls are collected on the connection pads. Can be mounted efficiently. Here, when the wind speed is less than 5 m / sec, the solder balls are concentrated on the outer peripheral portion of the cylindrical member, so that it is difficult to mount the solder balls on the connection pad region located at the center of the connection pad region. On the other hand, when the wind speed exceeds 35 m / sec, the solder balls are concentrated at the center of the cylindrical member, so that it is difficult to mount the solder balls on the connection pad area located at the outer periphery of the connection pad area. Here, the connection pad region is a region of 75A in FIG. 8 and includes a connection pad located in the outermost layer, and is a rectangular region having the smallest area. When the connection pad 75 is not arranged in a rectangular shape as shown in FIG. 9C, the connection pad region is set so that the rectangular area of the connection pad region 75A including the outermost connection pad is minimized. .

First, the structure of the multilayer printed wiring board 10 manufactured using the solder ball mounting method and mounting apparatus according to the embodiment of the present invention will be described with reference to FIGS. 6 shows a cross-sectional view of the multilayer printed wiring board 10 and FIG. 7 shows a state in which the IC chip 90 is attached to the multilayer printed wiring board 10 shown in FIG. As shown in FIG. 6, in the multilayer printed wiring board 10, conductor circuits 34 are formed on both surfaces of the core substrate 30. The top surface and the back surface of the core substrate 30 are connected via a through hole 36.

Furthermore, a conductor circuit 58 for forming a conductor circuit layer is formed on the conductor circuit 34 of the core substrate 30 via an interlayer resin insulating layer 50. The conductor circuit 58 is connected to the conductor circuit 34 via the via hole 60. A conductor circuit 158 is formed on the conductor circuit 58 via an interlayer resin insulation layer 150. Conductor circuit 158 is connected to conductor circuit 58 via via hole 160 formed in interlayer resin insulation layer 150.

A solder resist layer 70 is formed above the via hole 160 and the conductor circuit 158. By providing the nickel plating layer 72 and the gold plating layer 74 in the opening 71 of the solder resist layer 70, the connection pad 75 is formed. ing. A solder bump 78U is formed on the upper connection pad 75, and a BGA (ball grid array) 78D is formed on the lower connection pad 75.

 As shown in FIG. 7, the solder bumps 78 </ b> U on the upper surface side of the multilayer printed wiring board 10 are connected to the lands 92 of the IC chip 90. On the other hand, the lower BGA 78D is connected to the land 96 of the daughter board 94.

FIG. 8 is a plan view of a multilayer printed wiring board 10A for multi-piece production. The multilayer printed wiring board 10A is separated by cutting the individual multilayer printed wiring board 10 including the connection pad regions 75A in which the connection pads 75 are arranged in a matrix shape, by cutting along a dashed line in the drawing. FIG. 5 is an explanatory diagram of a process of forming solder bumps on the multi-layer printed wiring board 10A for multi-piece taking, and corresponds to a cross-sectional view taken along line Y1-Y1 in FIG. As shown in FIG. 5A, the flux 80 is printed on the surface of the multilayer printed wiring board 10A in which the connection pads 75 are formed in the openings 71 of the solder resist layer 70 on the surface. As shown in FIG. 5B, a small solder ball 78s (for example, manufactured by Hitachi Metals, Tamura, diameter 40 μm or more is used on the upper connection pad 75 of the multilayer printed wiring board 10A by using a solder ball mounting device described later. , Less than 200 μm). Solder balls with a diameter of less than 200 μm are desirable for finer processing. If the diameter is less than 40 μmΦ, the solder ball is too light and does not fall on the connection pad. On the other hand, if the diameter is 200 μmΦ or more, the solder balls cannot be assembled in the cylindrical member because they are too heavy, and there are connection pads on which the solder balls are not placed. In the present invention, it is highly significant to use solder balls having a diameter of 40 μmΦ or more and less than 200 μmΦ. In this range, it is advantageous for refinement. Further, in the method in which the solder ball is sucked by the suction head and the solder ball is mounted on the connection pad, since the solder ball is small and difficult to be sucked, the superiority of the method of the embodiment becomes clear.

Thereafter, as shown in FIG. 5C, a solder ball 78L having a normal diameter (diameter: 250 μmΦ) is formed on the connection pad 75 on the lower side of the multilayer printed wiring board 10A by a suction head according to a conventional technique (for example, Japanese Patent No. 1975429). Is adsorbed and placed. Thereafter, it is heated in a reflow furnace, and as shown in FIG. 6, for example, 500 to 30,000 solder bumps 78U (corresponding to the number of connection pads) are formed on the upper side of the multilayer printed wiring board 10A at a pitch of 60 μm or more and less than 200 μm on the lower side. For example, 250 BGAs 78D are formed at a pitch of 2 mm. In particular, when the number of connection pads is 2000 to 30000 or more, the connection pad area becomes large, and therefore, the significance of applying the method of the present invention is high. This is because the bump height is stable due to non-contact, and solder bumps with low height are unlikely to be generated, so that a printed wiring board with high connection reliability can be obtained. When the pitch is less than 60 μm, it becomes difficult to manufacture solder balls suitable for the pitch. When the pitch is 200 μm or more, the present method can be produced without any problem, but it can also be produced by a conventional method. Further, as shown in FIG. 7, after the multi-layer multilayer printed wiring board 10A is cut into individual multilayer printed wiring boards 10, the IC chip 90 is mounted via the solder bumps 78U by reflow. The multilayer printed wiring board 10 on which the IC chip 90 is mounted is attached to the daughter board 94 via the BGA 78D.

With reference to FIG. 5, a solder ball mounting apparatus for mounting a small (less than 200 μm diameter) solder ball 78s on the connection pad of the multilayer printed wiring board described above with reference to FIG.
FIG. 1A is a configuration diagram showing a configuration of a solder ball mounting device according to an embodiment of the present invention, and FIG. 1B is a diagram illustrating the solder ball mounting device of FIG. FIG.

The solder ball mounting device 20 includes an XYθ suction table 14 that positions and holds the multilayer printed wiring board 10A, a vertical movement shaft 12 that raises and lowers the XYθ suction table 14, and an opening that corresponds to the connection pad 75 of the multilayer printed wiring board. A ball alignment mask 16, a mounting cylinder (cylinder member) 24 for guiding a solder ball moving on the ball alignment mask 16, a suction box 26 for applying a negative pressure to the mounting cylinder 24, and excess solder balls are collected. A suction ball removing cylinder 61, a suction box 66 for applying a negative pressure to the suction ball removing cylinder 61, a suction ball removing suction device 68 for holding the collected solder balls, and a mask clamp for clamping the ball alignment mask 16 44, an X direction moving shaft 40 for sending the mounting cylinder 24 and the suction ball removing cylinder 61 in the X direction, and an X direction moving shaft 40 are supported. A moving shaft support guide 42, an alignment camera 46 for imaging the multilayer printed wiring board 10, a remaining amount detection sensor 18 for detecting the remaining amount of solder balls under the mounting cylinder 24, and a remaining amount detection sensor 18. A solder ball supply device 22 for supplying the solder balls to the mounting cylinder 24 based on the detected remaining amount. In the solder ball mounting apparatus 20 shown in FIG. 1, only the X-direction moving shaft 40 for sending the mounting cylinder 24 and the suction ball removing cylinder 61 in the X direction is shown, but a moving mechanism for sending in the Y direction can also be provided.

FIG. 9A is an explanatory view showing, in an enlarged manner, the connection pad region 75A and the mounting cylinder 24 of the multilayer printed wiring board 10A in FIG.
The mounting cylinder 24 has a lower end opening 24A (see FIG. 2B) formed in a rectangular shape. Therefore, the solder balls can be assembled into a substantially rectangular shape, and the solder balls can be efficiently mounted on the connection pads 75 in the connection pad region 75A having a substantially rectangular shape. Here, the length ax of the side (inner wall length) 24X parallel to the mounting cylinder movement direction (X direction) of the opening is defined as the length x of the side 75X parallel to the mounting cylinder movement direction of the connection pad region 75A. Is set to a (1.1 to 4) times. On the other hand, the length by of the side (inner wall length) 24Y perpendicular to the mounting tube movement direction of the opening (Y direction) is set to the length y of the side 75Y of the connection pad region 75A perpendicular to the mounting tube movement direction. It is set to b (1.1-4) times. For this reason, it is possible to collect the solder balls on the connection pad area 75A of the printed wiring board (on the ball alignment mask positioned on the connection pad area). Here, when the ratio is less than 1.1 times, as shown in FIG. 10A, the solder ball group (aggregate of solder balls) 78G gathers too much on the inner side, and the solder is applied to the connection pads 75 in the outer peripheral portion of the connection pad region 75A. The ball cannot be mounted. If it exceeds four times, as shown in FIG. 10 (B), the solder balls are not collected at the center of the mounting cylinder 24, and the solder balls cannot be mounted on the connection pads 75 at the center of the connection pad region 75A. Here, as shown in FIG. 9C, when the connection pads 75 are not arranged in a rectangular shape, x and y include the outermost connection pads so that the rectangular area of the connection pad region 75A is minimized. Set.

In the embodiment, (the length of the side 24X parallel to the cylinder member moving direction (X direction) of the opening of the mounting cylinder 24) / (the length of the side 75X parallel to the mounting cylinder moving direction of the connection pad region 75A). ) = A is larger than (length of side 24Y perpendicular to mounting cylinder movement direction of opening) / (length of side 75Y perpendicular to mounting cylinder movement direction of connection pad region 75A) = b (A> b). Therefore, as shown in FIG. 9B, the solder ball group 78G can be formed so as to be long in the moving direction (X direction) of the mounting cylinder 24 with respect to the connection pad region 75A having a substantially rectangular shape. When the mounting cylinder 24 is moved in the X direction, solder balls can be efficiently mounted on the connection pads 75 in the rectangular connection pad region 75A.

As shown in the plan view of FIG. 8, the mounting cylinder 24 and the suction ball removing cylinder 61 of the solder ball mounting apparatus 20 are arranged on the multi-layer printed wiring board 10A for multi-cavity so as to correspond to each connection pad area 75A. A plurality are arranged in the Y direction. Here, one mounting cylinder 24 corresponds to one connection pad area 75A, but the mounting cylinder 24 may be sized to correspond to a plurality of connection pad areas 75A. Here, the Y direction is convenient and may be arranged in the X direction. The XYθ suction table 14 positions, sucks, holds, and corrects the multilayer printed wiring board 10 on which the solder balls are mounted. The alignment camera 46 detects the alignment mark of the multilayer printed wiring board 10 on the XYθ suction table 14, and the positions of the multilayer printed wiring board 10 and the ball alignment mask 16 are adjusted based on the detected position. The remaining amount detection sensor 18 detects the remaining amount of solder balls by an optical method.

Next, a solder ball mounting process by the solder ball mounting apparatus 20 will be described with reference to FIGS.
(1) Position Recognition and Correction of Multilayer Printed Wiring Board As shown in FIG. 2 (A), the alignment mark 34M of the multi-layer printed wiring board 10A for picking multiple pieces is recognized by the alignment camera 46, and the ball alignment mask 16 is detected. Then, the position of the multilayer printed wiring board 10A is corrected by the XYθ suction table 14. That is, the positions of the openings 16a of the ball alignment mask 16 are adjusted so as to correspond to the connection pads 75 of the multilayer printed wiring board 10A.

(2) Solder Ball Supply As shown in FIG. 2B, the solder ball 78s is quantitatively supplied from the solder ball supply device 22 to the mounting cylinder 24 side. In addition, you may supply in a mounting cylinder previously.

(3) Solder ball mounting As shown in FIG. 3A, a predetermined clearance (for example, 0.5 to 4 times the ball diameter) with the ball alignment mask is maintained above the ball alignment mask 16. By positioning the mounting cylinder 24 and sucking air from the suction part 24b, the flow velocity of the gap between the mounting cylinder and the printed wiring board is set to 5 m / sec to 35 m / sec, and the mounting cylinder 24 is directly below the opening 24A. Solder balls 78 s were assembled on the ball alignment mask 16.

Thereafter, as shown in FIGS. 3B, 4A, and 8, the mounting cylinders 24 arranged along the Y axis of the multilayer printed wiring board 10A shown in FIGS. 1B and 1A. Is sent in the horizontal direction along the X-axis via the X-direction moving shaft 40. As a result, the solder balls 78s assembled on the ball alignment mask 16 are moved along with the transfer of the mounting cylinder 24, and the solder balls 78s are moved through the openings 16a of the ball alignment mask 16 to the multilayer printed wiring board 10A. Drop and mount on the connection pad 75. Thereby, the solder balls 78s are sequentially aligned on all the connection pads on the multilayer printed wiring board 10A side.

(4) Removal of Adhering Solder Balls As shown in FIG. 4B, after the surplus solder balls 78s are guided to the position without the openings 16a on the ball alignment mask 16 by the mounting cylinder 24, the suction ball removing cylinder 61 is used. Remove by suction.

(5) Removing the multilayer printed wiring board 10A from the XYθ suction table 14 for removing the board.

According to the solder ball mounting method and the solder ball mounting apparatus 20 of the present embodiment, the mounting cylinder 24 is positioned above the ball alignment mask 16, and the suction portion 24B (see FIG. 2B) of the mounting cylinder 24 is used. The solder balls 78s are gathered by sucking air, and the mounting cylinder 24 is moved in the horizontal direction, so that the gathered solder balls 78s are moved on the ball alignment mask 16, and the opening of the ball alignment mask 16 is opened. The solder balls 78s are dropped onto the connection pads 75 of the multilayer printed wiring board 10A through 16a. For this reason, the fine solder balls 78s can be surely mounted on all the connection pads 75 of the multilayer printed wiring board 10A. Further, since the solder ball 78s is moved in a non-contact manner, unlike the case of using a squeegee, the solder ball can be mounted on the connection pad 75 without scratching, and the height of the solder bump 78U can be made uniform. For this reason, it is excellent in environmental resistance tests such as mountability of electronic components such as IC, heat cycle test after mounting, and high temperature / high humidity test. Furthermore, since it does not depend on the flatness of the product, it is possible to appropriately place the solder balls on the connection pads even on a printed wiring board having many undulations on the surface. In addition, since a small solder ball can be surely placed on a connection pad, even in a printed wiring board having a connection pad pitch of 60 to 150 μm and a solder resist opening diameter of 40 to 100 μm, all bumps are bumps. A solder bump having a stable height can be obtained.

Further, since the solder balls are guided by the suction force, the solder balls can be prevented from aggregating and adhering. Furthermore, by adjusting the number of mounting cylinders 24, it is possible to cope with workpieces of various sizes (worksheet-sized multilayer printed wiring boards), so that it can be flexibly applied to various types and small-scale production. Is possible.

In the solder ball mounting apparatus of the present embodiment, as shown in FIG. 1B, a plurality of mounting cylinders 24 are arranged in the Y direction corresponding to the width of the work (multilayer printed wiring board having a work sheet size). By only sending the mounting cylinder 24 in the direction perpendicular to the row direction (X direction), the solder balls can be reliably mounted on all the connection pads 75 of the multilayer printed wiring board 10A.

Further, since the solder ball 78s remaining on the ball alignment mask 16 can be collected by the suction ball removing cylinder 61, an excessive solder ball remains and does not cause a failure such as a failure.

[Example]
(1) Preparation of printed wiring board A double-sided copper-clad laminate (for example, MCL-E-67 manufactured by Hitachi Chemical Co., Ltd.) was used as a starting material, and through-hole conductors and conductor circuits were formed on this substrate by a well-known method. . Thereafter, interlayer insulation layers and conductor circuit layers are alternately laminated by a well-known method (for example, “Build-Up Multilayer Printed Wiring Board” published by Nikkan Kogyo Shimbun on June 20, 2000). In the conductor circuit layer, a connection pad group for electrical connection to the IC was formed, and the connection pad group was formed with 2000 connection pads of 120 μmΦ in the connection pad region (70 mm ² : 10 mm × 7 mm), Most of them are arranged in a grid pattern with a pitch of 150 μm, and the via pads (the solder bumps are formed immediately above the via holes) are preferably filled vias, and the dents and protrusions (see FIG. 14). ) Is preferably in the range of −5 to 5 μm with respect to the conductor thickness of the conductor circuit 158. When the recessed amount of the filled via exceeds 5 μm (−5 μm), Since there are fewer contacts on the connection pad, the wettability becomes worse when solder bumps are formed, and voids tend to get caught in solder or not mounted (missing bumps), while the thickness of the conductor circuit 158 exceeds 5 μm. Since it becomes thicker, it is not suitable for making finer.
A commercially available solder resist was formed thereon (film thickness 20 μm), and an opening of 90 μmφ was formed in the solder resist on the connection pad by photographic method in order to expose the connection pad.

(2) Solder ball mounting (1) A commercially available rosin flux was applied to the surface (IC mounting surface) of the printed wiring board. Thereafter, the printed circuit board was mounted on the suction table of the solder ball mounting apparatus of the present invention described above, the alignment marks of the printed wiring board and the ball alignment mask were recognized using a CCD camera, and the printed wiring board and the ball alignment mask were aligned. Here, as the ball alignment mask, a Ni metal mask having an opening of 110 μmφ at a position corresponding to the connection pad of the printed wiring board was used. The thickness of the metal mask is preferably 1/4 to 3/4 of the solder ball. Although a Ni metal mask is used here, a ball alignment mask made of SUS or polyimide can also be used. The opening diameter formed in the ball alignment mask is preferably 1.1 to 1.5 times the diameter of the ball used. Next, a mounting tube made of SUS having a size corresponding to the connection pad area (1.1 to 4 times the area where the connection pad is formed) and a height of 200 mm is 0.5 to 0.5 times the solder ball diameter. A Sn63Pb37 solder ball (manufactured by Hitachi Metals Co., Ltd.) having a ball diameter of 80 μm was placed on the ball alignment mask in the vicinity of the periphery of the metal mask (ball alignment mask) while maintaining a 4-fold clearance. In the embodiment, Sn / Pb solder is used for the solder balls, but Pb-free solder selected from the group consisting of Sn and Ag, Cu, In, Bi, Zn, or the like may be used.

Then, air is sucked from the suction portion (5 to 20 mmΦ) 24B (see FIG. 2B) at the top of the mounting cylinder, and the solder balls are gathered on the ball alignment mask in the mounting cylinder by satisfying the following relational expression. I let you.
“Flow velocity in the gap between the mounting cylinder and ball alignment mask> Wind speed in the mounting cylinder and the natural falling speed of the solder ball> Wind speed in the mounting cylinder (excluding the wind speed of the suction part)”
In order to satisfy the above relational expression, the following main parameters were adjusted.
Parameter (1): Suction amount from the suction part at the top of the mounting cylinder (2L / min to 500L / min)
Parameter (2): Gap between the mounting cylinder and the ball alignment mask (0.5 to 2.5 times the solder ball diameter)
Parameter (3): Area of the lower end opening 24 (A) of the mounting cylinder (see FIGS. 2B and 9)

Here, the wind speed between the mounting cylinder and the ball alignment mask can be 5 to 35 m / sec, and the wind speed in the mounting cylinder can be 0.1 m / sec to 2 m / sec. Further, the size of the mounting cylinder (see FIG. 9) does not have to be a size obtained by enlarging the connection pad region (electronic component mounting region) at the same magnification. The enlargement magnification of the mounting cylinder relative to the connection pad area is preferably larger on the moving direction side. As described above, when the mounting cylinder becomes larger in the moving direction, the solder balls exist wider in the moving direction as described above with reference to FIG. Since a chance of dropping to the opening of the ball alignment mask occurs, the solder ball mounting rate is improved.

Thereafter, the mounting ball was sent at a moving speed of 20 mm / sec to move the solder ball, and the solder ball was dropped from the opening of the ball alignment mask to mount the solder ball on the connection pad. Next, after removing excess solder balls from the ball alignment mask, the solder ball alignment mask and the printed wiring board were separately removed from the solder ball mounting apparatus. Finally, the printed wiring board produced above was put into a reflow set at 230 degrees to obtain a printed wiring board with solder balls.

[Example 1]
Example 1 was prepared according to the example, and solder balls having a diameter of 80 μmΦ were used. The number of pads was changed from 2000 to 4000. As a result, the connection pad area was 130 (75X = 13 mm, 75Y = 10 mm, see FIG. 9A) mm ² . Moreover, in the ball mounting, the main parameters described above were adjusted as follows.
(1) Suction amount = 25 L / min (suction part diameter: 6.5 mmΦ)
(2) Gap = 0.2-0.3mm
(3) Opening area = 1170 mm ² (24X = 39: a = 3, 24Y = 30: b = 3)
As a result, the wind speed between the mounting cylinder and the ball alignment mask was 11 to 17 m / sec, and the wind speed in the mounting cylinder was 0.65 m / sec or less. In addition, since no solder ball was sucked from the suction part, the wind speed in the mounting cylinder must be less than the natural falling speed of the solder ball (less than the natural falling speed of the solder ball> the wind speed in the mounting cylinder). Was also confirmed.

[Example 2]
In Example 2, a and b were set to a = b = 1.1 in Example 1. Parameter (1) was adjusted within the range of the example, and the wind speed between the mounting cylinder and the ball alignment mask was set to 11 to 17 m / sec, and the wind speed in the mounting cylinder was set to 0.65 m / sec or less. Further, since no solder balls were sucked from the suction portion, it was confirmed that the natural falling speed of the solder balls> the wind speed in the mounting cylinder.

[Example 3]
In Example 3, a and b were set to a = b = 4 in Example 1. Parameter (1) was adjusted within the range of the example, and the wind speed between the mounting cylinder and the ball alignment mask was set to 11 to 17 m / sec, and the wind speed in the mounting cylinder was set to 0.65 m / sec or less. Further, since no solder balls were sucked from the suction portion, it was confirmed that the natural falling speed of the solder balls> the wind speed in the mounting cylinder.

[Example 4]
In Example 4, a and b were set to a = 3 and b = 1.1 in Example 1. In addition, parameter (1) was adjusted within the range of the example so that the wind speed between the mounting cylinder and the ball alignment mask was 5 to 10 m / sec, and the wind speed in the mounting cylinder was 0.65 m / sec or less. Further, since no solder balls were sucked from the suction portion, it was confirmed that the natural falling speed of the solder balls> the wind speed in the mounting cylinder.

[Example 5]
In Example 5, a and b in Example 1 were set to a = 4 and b = 1.1. In addition, parameter (1) was adjusted within the range of the example so that the wind speed between the mounting cylinder and the ball alignment mask was 20 to 25 m / sec, and the wind speed in the mounting cylinder was 0.65 m / sec or less. Further, since no solder balls were sucked from the suction portion, it was confirmed that the natural falling speed of the solder balls> the wind speed in the mounting cylinder.

[Example 6]
In Example 6, a and b in Example 1 were set to a = 4 and b = 3. In addition, parameter (1) was adjusted within the range of the example so that the wind speed between the mounting cylinder and the ball alignment mask was 30 to 35 m / sec, and the wind speed in the mounting cylinder was 0.65 m / sec or less. Further, since no solder balls were sucked from the suction portion, it was confirmed that the natural falling speed of the solder balls> the wind speed in the mounting cylinder.

[Example 7]
In Example 7, a = 2 and b = 1.1 in Example 1, and parameter (1) is adjusted within the range of the example, and the wind speed between the mounting cylinder and the ball alignment mask is 11 to 17 m. / sec, the wind speed in the mounting cylinder was 0.65 m / sec or less. Further, since no solder balls were sucked from the suction portion, it was confirmed that the natural falling speed of the solder balls> the wind speed in the mounting cylinder.

[Example 8]
In Example 8, a = 3 and b = 1.1 in Example 1, parameter (1) is adjusted within the range of the example, and the wind speed between the mounting cylinder and the ball alignment mask is 11 to 17 m. / sec, the wind speed in the mounting cylinder was 0.65 m / sec or less. Further, since no solder balls were sucked from the suction portion, it was confirmed that the self-falling speed of the solder balls> the wind speed in the mounting cylinder.

[Example 9]
In Example 9, a = 4 and b = 1.1 in Example 1, parameter (1) is adjusted within the range of the example, and the wind speed between the mounting cylinder and the ball alignment mask is 11 to 17 m. / sec, the wind speed in the mounting cylinder was 0.65 m / sec or less. Further, since no solder balls were sucked from the suction portion, it was confirmed that the natural falling speed of the solder balls> the wind speed in the mounting cylinder.

[Example 10]
In Example 10, a = 4 and b = 3 in Example 1, parameter (1) is adjusted within the range of the example, and the wind speed between the mounting cylinder and the ball alignment mask is 11 to 17 m / sec. The wind speed in the mounting cylinder was 0.65 m / sec or less. Further, since no solder balls were sucked from the suction portion, it was confirmed that the natural falling speed of the solder balls> the wind speed in the mounting cylinder.

[Reference Example 1]
In Reference Example 1, a and b were set to a = b = 1 in Example 1. The parameter (1) was adjusted within the range of the example, so that the wind speed between the mounting cylinder and the ball alignment mask was 11 to 17 m / sec, and the wind speed in the mounting cylinder was 0.65 m / sec or less. Further, since no solder balls were sucked from the suction portion, it was confirmed that the natural falling speed of the solder balls> the wind speed in the mounting cylinder.

[Reference Example 2]
In Reference Example 2, a and b were set to a = b = 5 in Example 1. Parameter (1) was adjusted within the range of the example, and the wind speed between the mounting cylinder and the ball alignment mask was set to 11 to 17 m / sec, and the wind speed in the mounting cylinder was set to 0.65 m / sec or less. Further, since no solder balls were sucked from the suction portion, it was confirmed that the natural falling speed of the solder balls> the wind speed in the mounting cylinder.

[Reference Example 3]
In Reference Example 3, a and b were set to a = b = 3 in Example 1. In addition, parameter (1) was adjusted within the range of the example so that the wind speed between the mounting cylinder and the ball alignment mask was less than 5 m / sec, and the wind speed in the mounting cylinder was 0.65 m / sec or less. Further, since no solder balls were sucked from the suction portion, it was confirmed that the natural falling speed of the solder balls> the wind speed in the mounting cylinder.

[Reference Example 4]
In Reference Example 4, a and b were set to a = b = 3 in Example 1. Further, the parameter (1) is adjusted within the range of the embodiment so that the wind speed between the mounting cylinder and the ball alignment mask is 40 to 45 m / sec, and the wind speed in the mounting cylinder is 0.65 m / sec or less. did. Further, since no solder balls were sucked from the suction portion, it was confirmed that the natural falling speed of the solder balls> the wind speed in the mounting cylinder.

[Reference Example 5]
In Reference Example 5, a = 1 and b = 1.1 in Example 1, parameter (1) is adjusted within the range of the example, and the wind speed between the mounting cylinder and the ball alignment mask is 11 to 17 m. / sec, the wind speed in the mounting cylinder was 0.65 m / sec or less. Further, since no solder balls were sucked from the suction portion, it was confirmed that the natural falling speed of the solder balls> the wind speed in the mounting cylinder.

[Reference Example 6]
In Reference Example 6, a = 5 and b = 1.1 in Example 1, parameter (1) is adjusted within the range of the example, and the wind speed between the mounting cylinder and the ball alignment mask is 11 to 17 m. / sec, the wind speed in the mounting cylinder was 0.65 m / sec or less. Further, since no solder balls were sucked from the suction portion, it was confirmed that the natural falling speed of the solder balls> the wind speed in the mounting cylinder.

[Examples 11 to 20, Reference Examples 7 to 12]
In Examples 1 to 10 and Reference Examples 1 to 6, the solder balls used were 40 μmΦ. With this change, the film thickness of the solder resist was 10 μm, the opening of the solder resist was 45 μmΦ, and the opening of the ball alignment mask was 50 μmΦ. The wind speed in the mounting cylinder was adjusted to 0.1 m / sec. Other than that, it produced according to each Example and each reference example.

[Examples 21-30, Reference Examples 13-18]
In Examples 1 to 10 and Reference Examples 1 to 6, the solder balls used were 150 μmΦ. Along with this change, the connection pad was 200 μmΦ, the solder resist opening was 170 μmΦ, and the ball alignment mask opening was 200 μmΦ. The connection pads were mostly formed at a pitch of 250 μm, the number of connection pads was reduced, and the connection pad area was formed within 130 mm ² . Other than that, it created according to each Example and each reference example.

[Examples 31 to 40, Reference Examples 19 to 24]
In Examples 1 to 10 and Reference Examples 1 to 6, the solder balls used were 180 μmΦ. Along with this change, the connection pad was 250 μmΦ, the solder resist opening was 220 μmΦ, and the ball alignment mask opening was 250 μmΦ. The connection pads were mostly formed at a pitch of 300 μm and the number of connection pads was reduced to form a connection pad area within 130 mm ² . Other than that, it created according to each Example.

[Comparative Example 1]
In Example 1, the solder ball mounting method was changed, and 80 μmφ solder balls were mounted on a printed wiring board using a ball alignment squeegee as in the prior art.

[Comparative Example 2]
In Example 11, the solder ball mounting method was changed, and 40 μmφ solder balls were mounted on a printed wiring board using a ball alignment squeegee as in the prior art.

[Comparative Example 3]
In Example 21, the solder ball mounting method was changed, and 150 μmφ solder balls were mounted on a printed wiring board using a ball alignment squeegee as in the prior art.

[Comparative Example 4]
In Example 31, the solder ball mounting method was changed, and 180 μmφ solder balls were mounted on a printed wiring board using a ball alignment squeegee as in the prior art.

[Comparative Example 5]
In Comparative Example 5, solder bumps were formed using solder paste instead of solder balls in Example 1.

(Evaluation test)
100 printed wiring boards with solder balls of each example, reference example and comparative example were prepared, and the presence or absence of solder bumps on all connection pads of each printed wiring board was confirmed (× 10 magnification microscope). A printed wiring board having solder bumps formed on all connection pads was regarded as a good product, and a printed wiring board having connection pads not formed with solder bumps was regarded as defective. The number of non-defective printed wiring boards was counted and used as the yield (number of non-defective printed wiring boards / 100 × 100%). The results are shown in the charts in FIGS.

It turned out that a yield can be raised by making a and b 1.1 to 4 times. It was also found that the yield can be further increased by making a larger than b. On the other hand, it was found that the solder balls can be efficiently mounted on the connection pads by adjusting the wind speed between the mounting cylinder and the ball alignment mask to 5 to 35 m / sec.

Comparing the yield of the comparative example and the yield of the present invention, it can be seen that the present invention is highly significant when the solder balls are 40 to 150 μmΦ.

The height of the solder bump of Example 1 and Comparative Example 5 (height protruding from the solder resist) was measured with a WYKO “NT2000” manufactured by Beco Co., Ltd., and the variation (σ) was calculated. The results were as follows.
σ
Example 1 1.26
Comparative Example 5 2.84

Further, an IC was mounted on the printed wiring boards of Example 1 and Comparative Example 5, and an underfill was filled between the IC and the printed wiring board to obtain an IC-mounted printed wiring board. Thereafter, the connection resistance of a specific circuit connected to the back surface of the IC-mounted printed wiring board from the back surface (the side opposite to the IC mounting surface) of the IC-mounted printed wiring board was measured again as an initial value. After the initial value measurement, the sample was left in an atmosphere of 85 ° C. × 80% for 15 hours, and then a heat cycle test with one cycle of −55 ° C. × 5 minutes to 125 ° C. × 5 minutes was repeated 1000 times, and the connection resistance was measured again. We measured the connection reliability. The amount of change in connection resistance is represented by ((connection resistance value after heat cycle−initial connection resistance value) / initial connection resistance value) × 100, and if the value is within ± 10%, it is acceptable. Beyond that, it is bad. As a result, Example 1 was “pass” and Comparative Example 5 was “bad”.

FIG. 1A is a configuration diagram showing a configuration of a solder ball mounting device according to an embodiment of the present invention, and FIG. 1B is a diagram illustrating the solder ball mounting device of FIG. FIG. FIG. 2A is an explanatory diagram of positioning of the multilayer printed wiring board, and FIG. 2B is an explanatory diagram of supply of solder balls to the mounting cylinder. FIG. 3A is an explanatory diagram of a set of solder balls by a mounting cylinder, and FIG. 3B is an explanatory diagram of a set of solder balls by a mounting cylinder and guidance. FIG. 4A is an explanatory view of the dropping of the solder ball onto the connection pad, and FIG. BB is an explanatory view of the removal of the solder ball by the suction ball removing cylinder. 5 (A), 5 (B), and 5 (C) are explanatory diagrams of the manufacturing process of the multilayer printed wiring board. It is sectional drawing of a multilayer printed wiring board. It is sectional drawing which shows the state which attached the IC chip to the multilayer printed wiring board shown in FIG. 6, and mounted in the daughter board. It is a top view of the multilayer printed wiring board for multi-piece taking. FIG. 9A is an explanatory view showing the correspondence between the connection pad region and the mounting cylinder, and FIG. 9B is an explanatory view of a solder ball group assembled by the mounting cylinder, and FIG. FIG. 10 is a plan view of another example of the connection pad region. FIG. 10A is an explanatory view showing the correspondence between a mounting cylinder in which a and b are less than 1.1 and a solder ball group, and FIG. 10B is a mounting cylinder and solder in which a and b are more than 4. It is explanatory drawing which shows a response | compatibility with a ball group. It is a graph which shows the evaluation result of an Example, a reference example, and a comparative example. It is a graph which shows the evaluation result of an Example, a reference example, and a comparative example. FIGS. 13A, 13B, and 13C are schematic views showing mounting of solder balls using a conventional ball alignment mask. It is explanatory drawing of the uneven | corrugated amount of a filled via.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printed wiring board 16 Ball alignment mask 16a Opening 20 Solder ball mounting apparatus 22 Solder ball supply apparatus 24 Mounting cylinder (cylinder member)
24A Opening 24X, 24Y Side 42 Moving shaft support guide 61 Suction ball removal cylinder 68 Suction ball removal suction device 75 Connection pad 75A Connection pad area 75X, 75Y Side 78s Solder ball 78G Solder ball group

Claims (4)

A solder ball mounting device for mounting a solder ball to be a solder bump on each connection pad in a connection pad area of a printed wiring board,
A ball alignment mask having a plurality of openings corresponding to connection pads of the printed wiring board;
A cylindrical member that is located above the ball alignment mask and collects solder balls directly under the opening by sucking air from the opening;
A moving mechanism for moving the cylindrical member in a horizontal direction, and moving the solder ball assembled on the ball alignment mask by moving the cylindrical member, through the opening of the ball alignment mask, A movement mechanism for dropping the solder ball onto the connection pad of the printed wiring board, and the opening of the cylindrical member is substantially rectangular,
The length of the side parallel to the cylindrical member moving direction of the opening is 1.1 to 4 times the length of the side parallel to the cylindrical member moving direction of the connection pad region,
Solder characterized in that the length of the side of the opening perpendicular to the direction of movement of the cylindrical member is 1.1 to 4 times the length of the side of the connection pad region perpendicular to the direction of movement of the cylindrical member. Ball mounting device. The length of the side of the opening parallel to the cylinder member movement direction / the length of the side of the connection pad area parallel to the cylinder member movement direction is the length of the side of the opening perpendicular to the cylinder member movement direction / 2. The solder ball mounting device according to claim 1, wherein the length of the side perpendicular to the moving direction of the cylindrical member of the connection pad region is larger. 3. The solder ball mounting device according to claim 1, wherein a wind speed between the cylindrical member and the ball alignment mask is 5 to 35 m / sec. A solder ball mounting method for mounting a solder ball to be a solder bump on a connection pad of a printed wiring board using a ball alignment mask having a plurality of openings corresponding to the connection pads in the connection pad area of the printed wiring board ,
The opening has a substantially rectangular shape, and the length of the side parallel to the cylindrical member moving direction of the opening is 1.1 to 4 with respect to the length of the side parallel to the cylindrical member moving direction of the connection pad region. A cylindrical member in which the length of the side perpendicular to the cylindrical member moving direction of the opening is 1.1 to 4 times the length of the side perpendicular to the cylindrical member moving direction of the connection pad region The solder balls are gathered on the ball alignment mask directly below the cylindrical member by being positioned above the ball alignment mask and sucking air with the cylindrical member.
By moving the cylindrical member in the horizontal direction, the solder balls assembled on the ball alignment mask are moved, and the solder balls are dropped onto the connection pads of the printed wiring board through the openings of the ball alignment mask. A solder ball mounting method characterized by comprising:

Images