Array mask

Abstract

To provide an array mask that can more quickly and smoothly inject solder balls into through holes compared with conventional array masks.SOLUTION: An array mask according to the present invention has through holes 12 corresponding to a predetermined array pattern. The upper openings 17 of the through holes 12 are round holes with an opening diameter D1 larger than the diameter d of the solder balls 2. On the inner peripheral surface 19 of the through holes 12, one or more positioning bodies 20 are formed, projecting toward the center of the hole, to guide the solder balls 2 inserted into the through holes 12 toward a predetermined position and to hold and position the solder balls 2 at the predetermined position.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mask for arranging solder balls, which is used to create solder bumps in a BGA (Ball Grid Array) system. [Background technology]

[0002] The BGA (Ball Grid Array) method has long been known as a method for forming solder bumps. This BGA method involves a printing process in which flux is applied to electrodes on a substrate, such as a wafer, flexible substrate, or rigid substrate; an arrangement process in which solder balls are arranged on the flux; and a heating process in which the solder balls are heated and melted. A known method for arranging solder balls on a substrate is the transfer method using a mask. In this transfer method, solder balls are placed on the electrodes of the substrate using an arrangement mask (hereinafter simply referred to as the "mask") with positioning through-holes through which the solder balls can be inserted, corresponding to the arrangement pattern of the electrodes on the substrate. Specifically, the mask is placed on the substrate so that the through-holes align with the electrodes. Then, a sweeping tool such as a squeegee or brush is used to sweep the solder balls supplied onto the mask, depositing one solder ball into each through-hole, thereby adhering the solder balls to the flux and placing them in their designated positions on the substrate.

[0003] A known example of an array mask is disclosed in Patent Document 1, for example. The through holes of the mask in Patent Document 1 are configured as straight holes with a fixed penetration direction. The opening diameter of the straight holes is set slightly larger than the diameter of the solder balls. Solder balls supplied onto the mask are introduced into each through hole through the upper opening of the through hole and are positioned at a predetermined position by the inner peripheral surface of each through hole. An array mask with a similar configuration is also disclosed in Patent Document 2 by the present patent applicant. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-287215 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-324618 Summary of the Invention [Problem to be solved by the invention]

[0005] When a solder ball is supplied onto the mask and swept by a sweeping tool, it is attracted and attempts to fall into the through hole when its center of gravity is located above the upper opening of the through hole. However, with the masks of Patent Documents 1 and 2, the diameter of the upper opening of the through hole is only slightly larger than the diameter of the solder ball, so the center of gravity of the solder ball is not often located above the upper opening of the through hole, which can easily cause delays in the insertion of the solder ball into the through hole. Furthermore, there is a risk that the solder ball falling down the through hole will come into contact with the inner circumferential surface of the through hole and become stuck, which is a disadvantage in that the solder ball cannot be inserted smoothly into the through hole.

[0006] An object of the present invention is to provide an array mask that allows solder balls to be inserted into through-holes more quickly and smoothly. [Means for solving the problem]

[0007] The present invention is directed to an array mask that places solder balls 2 at predetermined positions on a substrate 3 by dropping the solder balls 2 into through holes 12 that correspond to a predetermined array pattern. The array mask is characterized in that one or more positioning bodies 20 are formed on inner peripheral surfaces 19 of the through holes 12, which are circular holes with upper openings 17 having opening diameters D1 larger than the diameters d of the solder balls 2, and that these positioning bodies 20 extend toward the center of the holes to guide the solder balls 2 that have been dropped into the through holes 12 toward the predetermined positions and to hold and position the solder balls 2 at the predetermined positions.

[0008] The positioning body 20 consists of a protrusion formed by extending in the vertical direction along the inner surface 19 of the through hole 12, and is configured to include a receiving portion 21 provided on the lower opening 18 side of the through hole 12, which receives and holds the solder ball 2 within the through hole 12, and an introduction portion 22 provided on the upper opening 17 side of the through hole 12, which guides the solder ball 2 to a predetermined position within the through hole 12.

[0009] The introduction portion 22 is formed so that the protruding dimension gradually increases toward the lower opening 18. The upper end of the introduction portion 22 is configured as part of the opening edge of the upper opening 17 of the through-hole 12, which is a round hole.

[0010] Three or more positioning bodies 20 are provided on the inner peripheral surface 19 of the through hole 12. When the inner peripheral surface 19 of the through hole 12 is divided into two semi-circumferential surfaces 19a and 19b at any position, a positioning body 20 is provided on each of the semi-circumferential surfaces 19a and 19b.

[0011] The positioning bodies 20 are provided at equal intervals in the circumferential direction on the inner peripheral surface 19 of the through-hole 12 .

[0012] The positioning body 20 is provided on the inner peripheral surface 19 of the through-hole 12 located downstream in the movement direction of a sweeping tool S that moves over the array mask to drop the solder balls 2 into the through-holes 12 .

[0013] When viewed in a plane, assuming that an imaginary line V passes through the center of the through hole 12, a positioning body 20 is provided at a position where the imaginary line V directed in the direction of movement of the sweeping tool S intersects with the inner surface 19 of the through hole 12 downstream in the direction of movement of the sweeping tool S.

[0014] The cross section of the positioning body 20 consisting of a protrusion, which is perpendicular to the vertical direction, is formed into a frustum shape, and the positioning body 20 is provided so that the arc on the longer side of the frustum faces the inner surface 19 of the through hole 12.

[0015] The cross section of the positioning body 20 made of a protrusion, which is perpendicular to the vertical direction, is formed into a trapezoid shape, and the positioning body 20 is provided so that the base of the longer side of the trapezoid faces the inner peripheral surface 19 of the through hole 12.

[0016] The cross-sectional shape of the positioning body 20 consisting of a protrusion, which is perpendicular to the vertical direction, is formed into a fan shape with the main part rounded, and the positioning body 20 is provided so that the arc of the fan shape faces the inner surface 19 of the through hole 12.

[0017] The cross section of the positioning body 20 made of a rib is formed into a fan shape perpendicular to the vertical direction, and the positioning body 20 is provided so that the arc of the fan shape faces the inner peripheral surface 19 of the through hole 12. [Effects of the Invention]

[0018] In the array mask of the present invention, one or more positioning bodies 20 are formed on the inner peripheral surface 19 of the through holes 12, which are round holes with an opening diameter D1 of the upper opening 17 larger than the diameter d of the solder balls 2, and extend toward the center of the hole to guide the solder balls 2 inserted into the through holes 12 toward a predetermined position and to hold and position the solder balls 2 in the predetermined position. In this way, when the one or more positioning bodies 20 extending from the inner peripheral surface 19 of the through holes 12 guide and hold the solder balls 2 at the predetermined position in the through holes 12, the opening diameter D1 of the upper openings 17 of the through holes 12 can be made larger than the diameter d of the solder balls 2 by the extension dimension of the positioning bodies 20, compared to conventional masks that hold the solder balls on the inner peripheral surface of the through holes. This increases the chance that the center of gravity of the solder balls 2 swept by the sweeping tool S will be located above the upper openings 17 of the through holes 12, making it easier for the solder balls 2 to be guided into the through holes 12. Furthermore, by making the opening diameter D1 of the upper opening 17 of the through hole 12 larger than the diameter d of the solder ball 2, a gap can be formed between the peripheral surface of the solder ball 2 falling into the through hole 12 and the inner peripheral surface 19 of the through hole 12, thereby preventing the solder ball 2 falling through the through hole 12 from coming into contact with and getting caught on the inner peripheral surface 19. As described above, the array mask 1 according to the present invention makes it possible to insert the solder balls 2 into the through holes 12 more quickly and smoothly than conventional array masks. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 2 is a plan view showing through holes of the array mask according to the first embodiment of the present invention. [Figure 2] 1A and 1B are a perspective view showing an entire array mask and a workpiece, and an enlarged plan view of a portion of the array mask. [Figure 3] FIG. 2 is a vertical sectional front view of a main part of the array mask. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] FIG. 10 is a plan view showing through holes of an array mask according to a second embodiment of the present invention. [Figure 7] FIG. 10 is a plan view showing through holes of an array mask according to a third embodiment of the present invention. [Figure 8] FIG. 10 is a plan view showing through holes of an array mask according to a fourth embodiment of the present invention. [Figure 9] FIG. 10 is a plan view showing through holes of an array mask according to a fifth embodiment of the present invention. [Figure 10] FIG. 10 is a plan view showing a positioning body for an array mask according to a sixth embodiment of the present invention. [Figure 11] FIG. 13 is a plan view showing a positioning body for an array mask according to a seventh embodiment of the present invention. [Figure 12] FIG. 13 is a plan view showing a positioning body for an array mask according to an eighth embodiment of the present invention. [Figure 13] FIG. 13 is a vertical cross-sectional view showing a positioning body for an array mask according to a ninth embodiment of the present invention. [Figure 14] FIG. 20 is a longitudinal sectional view showing a positioning body for an array mask according to a tenth embodiment of the present invention. [Figure 15] FIG. 22 is a vertical cross-sectional view showing a positioning body for an array mask according to an eleventh embodiment of the present invention. [Figure 16] FIG. 23 is a longitudinal sectional view showing a positioning body for an array mask according to a twelfth embodiment of the present invention. [Figure 17] FIG. 23 is a vertical cross-sectional view showing a positioning body for an array mask according to a thirteenth embodiment of the present invention. [Figure 18] FIG. 23 is a longitudinal sectional view showing a positioning body for an array mask according to a fourteenth embodiment of the present invention. [Figure 19] FIG. 22 is a vertical cross-sectional view showing a positioning body for an array mask according to a fifteenth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] (First embodiment) Figures 1 to 4 show a first embodiment of a solder ball array mask according to the present invention. In this embodiment, front, back, left, right, and top and bottom refer to the crossed arrows shown in Figures 1 and 3 and the notations for front, back, left, right, and top and bottom near the crossed arrows. The top and bottom directions correspond to the thickness direction of the array mask, and the dimensions such as thickness in each figure are shown schematically rather than showing the actual state. This array mask (hereinafter simply referred to as the mask) 1 is used in the operation of arranging solder balls 2 in the creation of solder bumps for the BGA method. The solder balls 2 are spheres with a diameter d of 100 μm or less.

[0021] In FIG. 2, reference numeral 3 denotes a substrate (workpiece) on which solder balls 2 are mounted using a mask 1. This substrate 3 is formed by mounting multiple semiconductor chips 5 on a base 4, such as a glass epoxy substrate, and then wiring the chips by wire bonding and sealing them with a transfer mold. On the top surface of the substrate 3, electrodes 6 serving as input / output terminals are formed in a predetermined arrangement pattern, surrounding the semiconductor chips 5. After solder bumps are formed, the substrate 3 is cut into individual pieces to form individual LSI chips. Each electrode 6 is formed in a circular shape, and its diameter is set to approximately the same as the diameter d of the solder ball 2. During a printing process prior to arranging the solder balls 2, flux 7 is applied to the electrodes 6 to temporarily adhesively hold the solder balls 2 in place. Note that each electrode 6 may be formed in a rectangular shape. In this case, the diameter d of the solder balls 2 is set to approximately the same as the length of the long side of the rectangle.

[0022] As shown in FIG. 2, the mask 1 comprises a mask body 10 formed by electroforming using copper, nickel, nickel alloys such as nickel-cobalt, or other electrodeposited metals, and a frame 11 bonded to surround the mask body 10. The frame 11 is rectangular, and its outer periphery matches the outer periphery of the mask body 10. The metal constituting the frame 11 is preferably a metal with a lower coefficient of linear thermal expansion (low thermal expansion material) than the metal constituting the mask body 10, such as 42 alloy, Invar, or SUS430. Other low thermal expansion materials include stainless steel, aluminum, and aluminum alloys. The surface of the mask body 10, surrounded by the frame 11, is formed with numerous pattern regions 13 each having a number of independent through-holes 12 for inserting solder balls 2, corresponding to each semiconductor chip 5. The frame 11 serves both as a holding member for holding the mask body 10 and as a reinforcing member for reinforcing the mask body 10.

[0023] When arranging the solder balls 2, the mask 1 is placed on the substrate 3. At this time, the mask body 10 has protrusions 14 on its underside to support the mask body 10 in a position spaced apart from the upper surface of the substrate 3. Specifically, as shown in FIG. 3 , a number of protrusions 14 are integrally formed on the underside of the mask body 10, i.e., the surface facing the substrate 3, so as to protrude downward. These protrusions 14 ensure a sufficient distance from the substrate 3. Each protrusion 14 is cylindrical, with a height approximately equal to or slightly smaller than half the diameter d (radius) of the solder ball 2. Providing these protrusions 14 prevents the flux 7 from adhering to the mask body 10 or the inner circumferential surfaces 19 of the through holes 12 when the mask 1 is placed on the substrate 3. The protrusions 14 are not limited to being independently formed, but may be arranged in a lattice frame shape surrounding the pattern region 13. The protrusions 14 are formed integrally with the mask body 10, but may also be formed separately and then integrally joined to the mask body 10. The shape of the protrusions 14 is not limited to a columnar shape, but may also be a rib shape.

[0024] As shown in FIGS. 1 and 3 , a large number of independent through-holes 12 are formed at positions corresponding to the arrangement pattern of the electrodes 6 of each semiconductor chip 5 on the substrate 3. Each through-hole 12 is a straight circular hole that penetrates the mask body 10 in the vertical direction (thickness direction) and has circular openings on the top and bottom surfaces of the mask body 10. The opening diameter D1 of the upper opening 17 of each through-hole 12 that opens on the top surface of the mask body 10 and the opening diameter D2 of the lower opening 18 that opens on the bottom surface of the mask body 10 are the same diameter, and both openings 17 and 18 are formed with diameters larger than the diameter d of the solder balls 2. Specifically, the opening diameters D1 and D2 of both openings 17 and 18 are preferably set to about 1.5 times the diameter d of the solder balls 2, and more preferably about 1.25 times the diameter d of the solder balls 2.

[0025] 1, one or more positioning bodies 20 are formed on the inner peripheral surface 19 of the through hole 12, protruding toward the center of the hole, to guide the solder balls 2 inserted into the through hole 12 toward a predetermined position and to hold and position the solder balls 2 at the predetermined position. In this embodiment, three positioning bodies 20 are provided at equal intervals in the circumferential direction of the inner peripheral surface 19 of the through hole 12, and one of the three positioning bodies 20 is provided on the inner peripheral surface 19 of the through hole 12 downstream of the movement direction of a squeegee brush (sweeping tool) S, which moves over the mask 1 to drop the solder balls 2 into the through hole 12 during the operation of arranging the solder balls 2.

[0026] Specifically, the squeegee brush S moves from the front to the rear of the mask 1. When an imaginary line V is drawn through the center of each through hole 12 in a plan view, one of the three positioning bodies 20 is provided at a position where the imaginary line V, which is oriented in the direction of movement of the squeegee brush S (front-to-back direction), intersects with the inner circumferential surface 19 of each through hole 12 downstream of the direction of movement of the squeegee brush S. The remaining two positioning bodies 20 are provided at positions rotated 120 degrees and 240 degrees clockwise from the previous positioning body 20, with respect to the center of each through hole 12. For example, when the diameter d of the solder ball 2 is 1 and the opening diameter D1 (opening diameter D2) of the upper opening 17 (lower opening 18) is 1.25 (1.25 times the diameter d of the solder ball 2), it is desirable that the protruding dimension of each positioning body 20 be 0.125 or less.

[0027] When three (three or more) positioning bodies 20 are provided on the inner peripheral surface 19 of the through hole 12, they do not necessarily have to be provided at equal intervals in the circumferential direction of the inner peripheral surface 19 of the through hole 12, but when the inner peripheral surface 19 of the through hole 12 is divided into two semi-circumferential surfaces 19a and 19b at an arbitrary position, it is desirable to provide a positioning body 20 on each of the semi-circumferential surfaces 19a and 19b. In this embodiment, when the inner peripheral surface 19 of the through hole 12 is divided into front and rear semi-circumferential surfaces 19a and 19b, two positioning bodies 20 are provided on the front semi-circumferential surface 19a and one positioning body 20 is provided on the rear semi-circumferential surface 19b.

[0028] As shown in FIGS. 3 and 4 , each positioning body 20 is made of a protrusion extending vertically from the inner peripheral surface 19 of the through hole 12. The protrusions include a receiving rib (receiving portion) 21 that is provided on the lower opening 18 side of the through hole 12 and receives and holds the solder ball 2 within the through hole 12, and an introduction rib (introduction portion) 22 that is provided on the upper opening 17 side of the through hole 12 and guides the solder ball 2 to a predetermined position within the through hole 12. The receiving rib 21 is made of a protrusion with a constant protrusion dimension and extends from the edge of the lower opening 18 of the through hole 12 to the vertical center. The receiving rib 21 has a rectangular cross section. The introduction rib 22 is made of a protrusion that gradually increases in protrusion dimension toward the lower opening 18 and extends from the edge of the upper opening 17 of the through hole 12 to the vertical center. The introduction rib 22 has a substantially right-angled triangular cross section whose hypotenuse is an arc recessed toward the inner peripheral surface 19. The lower end of the introduction rib 22 and the upper end of the receiving rib 21 are continuous with each other at the center of the through-hole 12 in the vertical direction.

[0029] As shown in Figure 5, the positioning body 20 made of a protruding strip has a cross section perpendicular to the vertical direction that is formed into a truncated fan shape, and is provided in the through hole 12 so that the arc on the longer side of the truncated fan shape faces the inner peripheral surface 19. The cross section of the receiving rib 21 is constant in the vertical direction, whereas the cross section of the introduction rib 22 changes in the vertical direction. Specifically, the cross section of the introduction rib 22 has an upper end that is formed by part of the opening edge of the upper opening 17 of the through hole 12, which is a round hole, and the protruding dimension gradually increases downward, with the lower end being formed by the upper end of the receiving rib 21.

[0030] The protruding tip of the receiving rib 21 is formed with a receiving surface 23 consisting of a curved surface that extends vertically and curves in the circumferential direction, and the protruding tip of the lead-in rib 22 is formed with an introduction surface 24 consisting of a curved surface that extends obliquely from the upper end of the receiving rib 21 toward the edge of the upper opening 17 and curves in the circumferential direction. The curvature of the cross section of the curved receiving surface 23 and the curvature of the cross section of the curved introduction surface 24 are arc curvatures with the center of the through hole 12 as the arc center. The curvature of the cross section of the receiving rib 21 (receiving surface 23) is constant in the vertical direction. On the other hand, the curvature of the cross section of the introduction rib 22 (receiving surface 24) gradually increases from the upper end to the lower end, with the upper end portion having the same curvature as the through hole 12 and the lower end portion having the same curvature as the cross section of the receiving rib 21.

[0031] The operation of arranging the solder balls 2 begins by aligning the mask 1 with the substrate 3, and then placing the mask 1 on the substrate 3. At this time, the lower ends of the protrusions 14 come into contact with the upper surface of the substrate 3, allowing the mask 1 to be stably placed on the substrate 3 with an appropriate opposing distance formed between the lower surface of the mask body 10 and the upper surface of the substrate 3.

[0032] Next, a large number of solder balls 2 are supplied onto the mask 1, and the squeegee brush S is used to sweep and distribute the solder balls 2 over the mask 1, and the solder balls 2 are dropped one by one into the through holes 12. The solder balls 2 attempt to fall into the through holes 12 when their center of gravity is located above the upper openings 17 of the through holes 12. The solder balls 2 that begin to fall into the through holes 12 are guided by the introduction surfaces 24 of the introduction ribs 22 toward the center of the through holes 12, i.e., toward the predetermined position where the solder balls 2 are held, and then are guided downward by the receiving surfaces 23 of the introduction ribs 22 and dropped into the predetermined position within the through holes 12. The solder balls 2 dropped into the through holes 12 are firmly held in place from three directions in a three-point support manner by the receiving ribs 21 of the three positioning bodies 20, and are further temporarily adhesively held in place by the flux 7. In this state, the center position of the solder ball 2 and the center position of the through-hole 12 are aligned in a plan view, and a gap space is formed between the solder ball 2 and the inner circumferential surface 19 of the through-hole 12 excluding the portion where the positioning body 20 is formed. Finally, the mask 1 is lifted vertically from above the substrate 3 and removed. This completes the arrangement process, allowing the solder balls 2 to be mounted on the electrodes 6.

[0033] Although the through hole 12 described above is configured as a straight hole with a constant opening diameter in the vertical direction (through-hole direction), the through hole 12 can also be configured as a tapered hole that narrows downward or tapered upward. Essentially, the through hole 12 is merely required to be a through hole whose upper opening 17 has an opening diameter D1 larger than the diameter d of the solder ball 2. The guide rib 22 has a vertical cross-sectional shape that is a substantially right-angled triangle with its hypotenuse formed by an arc that is recessed toward the inner circumferential surface 19. However, the guide rib 22 may also have a vertical cross-sectional shape that is a substantially right-angled triangle with its hypotenuse formed by an arc that bulges toward the center of the hole. The boundary between the guide rib 22 and the receiving rib 21 does not need to be at the vertical center of the through hole 12. The protruding dimensions of each positioning body 20 do not need to be the same; they can also be formed to have different protruding dimensions.

[0034] Second Embodiment FIG. 6 shows a second embodiment of a solder ball array mask according to the present invention. This second embodiment differs from the first embodiment in the number of positioning bodies 20. Four positioning bodies 20 are provided at equal circumferential intervals on the inner circumferential surface 19 of each through hole 12. Two of the four positioning bodies 20 are provided at a position where an imaginary line V passing through the center of each through hole 12 intersects with the inner circumferential surface 19 of the through hole 12 on the upstream side in the direction of movement of the squeegee brush S, and at a position where the imaginary line V intersects with the inner circumferential surface 19 of the through hole 12 on the downstream side in the direction of movement of the squeegee brush S. The remaining two positioning bodies 20 are provided at positions rotated 90 degrees clockwise from the previous positioning body 20 with respect to the center of each through hole 12. Since the other configurations are the same as those of the first embodiment, the same components are designated by the same reference numerals and their description will be omitted. This also applies to the third and subsequent embodiments.

[0035] Third Embodiment FIG. 7 shows a third embodiment of a solder ball array mask according to the present invention. This third embodiment differs from the first embodiment in the number of positioning bodies 20 and the circumferential length of the positioning bodies 20. Two positioning bodies 20 are provided at equal intervals in the circumferential direction on the inner circumferential surface 19 of each through hole 12. The two positioning bodies 20 are provided at a position where an imaginary line V passing through the center of each through hole 12 intersects with the inner circumferential surface 19 of the through hole 12 on the upstream side in the direction of movement of the squeegee brush S, and at a position where the imaginary line V intersects with the inner circumferential surface 19 of the through hole 12 on the downstream side in the direction of movement of the squeegee brush S. Furthermore, in this embodiment, the number of positioning bodies 20 formed is reduced, so the circumferential formation area of ​​the positioning bodies 20 on the inner circumferential surface 19 of the through hole 12 is larger than that of the positioning bodies 20 of the first embodiment. It is preferable that the central angle of the formation area of ​​the positioning bodies 20 be set to be less than 90 degrees. This is because if the central angle of the formation area of ​​the positioning body 20 is 90 degrees or more, friction due to contact between the solder ball 2 and the receiving surface 23 increases, and there is a risk that the solder ball 2 will get caught when it falls into the through hole 12.

[0036] (Fourth Embodiment) FIG. 8 shows a fourth embodiment of a solder ball array mask according to the present invention. This fourth embodiment differs from the first embodiment in the number of positioning bodies 20 formed. Similar to the third embodiment, two positioning bodies 20 are provided on the inner peripheral surface 19 of the through hole 12. When the inner peripheral surface 19 of the through hole 12 is divided into front and rear semi-peripherals 19a and 19b, the two positioning bodies 20 are provided on the rear semi-peripheral surface 19b in a line-symmetrical manner with respect to an imaginary line V passing through the center of the through hole 12 as the axis of symmetry. In this embodiment, the solder balls 2 are held in a predetermined position by the two positioning bodies 20 and the inner peripheral surface 19 of the through hole 12. In a plan view, the centers of the solder balls 2 held in a predetermined position are at different positions from the center of the through hole 12. In this embodiment, it is desirable to set the protruding dimensions of the positioning body 20 so that the largest inscribed circle defined by the protruding tips of both positioning bodies 20 and the inner surface 19 of the through hole 12 is the same as or slightly larger than the diameter d of the solder ball 2.

[0037] Fifth Embodiment FIG. 9 shows a fifth embodiment of a solder ball array mask according to the present invention. This fifth embodiment differs from the first embodiment in the number of positioning bodies 20 and the circumferential length of the positioning bodies 20. Specifically, one positioning body 20 is formed on the inner peripheral surface 19 of the through hole 12. Furthermore, when the inner peripheral surface 19 of the through hole 12 is divided into front and rear semi-peripherals 19a and 19b, this positioning body 20 is provided on the rear semi-peripheral surface 19b. The circumferential length of the positioning body 20 is longer than that of the positioning body 20 of the first embodiment. Furthermore, the positioning body 20 is provided symmetrically with respect to the imaginary line V passing through the center of the through hole 12 as the axis of symmetry. As in the fourth embodiment, the solder balls 2 are held in position within the through hole 12 by one positioning body 20 and the inner peripheral surface 19 of the through hole 12. In a plan view, the center of the solder ball 2 held in a predetermined position is at a different position from the center of the through-hole 12. In the positioning body 20 of this embodiment, for example, when the diameter d of the solder ball 2 is set to 1 and the opening diameter D1 (opening diameter D2) of the upper opening 17 (lower opening 18) is set to 1.25 (1.25 times the diameter d of the solder ball 2), it is desirable to set the protrusion dimension of the positioning body 20 to 0.25 or less.

[0038] 10 shows a sixth embodiment of a solder ball array mask according to the present invention. In this sixth embodiment, the cross-sectional shape of the positioning body 20 differs from that of the first embodiment. Specifically, the positioning body 20, which is made up of protrusions, has a trapezoidal cross-sectional shape perpendicular to the vertical direction, and is provided within the through-hole 12 so that the base of the longer side of the trapezoid faces the inner peripheral surface 19. The protruding tip of the receiving rib 21 is formed with a receiving surface 23 consisting of a flat surface extending vertically, and the protruding tip of the leading rib 22 is formed with a leading surface 24 consisting of a flat surface extending at an angle from the upper end of the receiving rib 21 toward the edge of the upper opening 17.

[0039] 11 shows a seventh embodiment of a solder ball array mask according to the present invention. In this seventh embodiment, the cross-sectional shape of the positioning body 20 differs from that of the first embodiment. Specifically, the positioning body 20, which is made up of ribs, has a cross-sectional shape perpendicular to the vertical direction, which is formed into a fan shape with the main part rounded, and is provided in the through hole 12 so that the arc of the fan faces the inner peripheral surface 19. The protruding tip of the receiving rib 21 is formed with a receiving surface 23 consisting of an arc surface extending vertically, and the protruding tip of the leading rib 22 is formed with a leading surface 24 consisting of an arc surface extending at an angle from the upper end of the receiving rib 21 toward the edge of the upper opening 17.

[0040] Eighth Embodiment FIG. 12 shows an eighth embodiment of a solder ball array mask according to the present invention. In this eighth embodiment, the cross-sectional shape of the positioning body 20 differs from that of the first embodiment. Specifically, the positioning body 20, which is made of ribs, has a fan-shaped cross-section perpendicular to the vertical direction, and is provided in the through-hole 12 so that the arc of the fan faces the inner circumferential surface 19. The protruding tip of the receiving rib 21 is formed with a receiving edge 30 consisting of a ridge extending along the vertical direction, and the protruding tip of the leading rib 22 is formed with a leading edge 31 consisting of a ridge extending at an angle relative to the vertical direction. The solder balls 2 falling through the through-hole 12 are guided to a predetermined position by the leading edge 31, and are held and positioned at the predetermined position by the receiving edge 30. As a modification of this embodiment, two leading edges 31, 31 may be formed at the protruding tips of the receiving rib 21 and the leading rib 22. In this case, the cross-sectional shape perpendicular to the vertical direction of the positioning body 20, which is made of ribs, is simply changed.

[0041] (Ninth Embodiment) Figure 13 shows a ninth embodiment of a solder ball array mask according to the present invention. In this ninth embodiment, the cross-sectional shape of the positioning body 20 differs from that of the first embodiment. The receiving rib 21 is a protrusion with a constant protrusion dimension, and is formed from the edge of the lower opening 18 of the through hole 12 to the vertical center. The cross-sectional shape of the receiving rib 21 is rectangular. The introduction rib 22 is a protrusion formed so that the protrusion dimension gradually increases toward the lower opening 18, and is formed from the edge of the upper opening 17 of the through hole 12 to the vertical center. The cross-sectional shape of the introduction rib 22 is a right-angled triangle. The lower end of the introduction rib 22 and the upper end of the receiving rib 21 are continuous at the vertical center of the through hole 12.

[0042] (Tenth Embodiment) Figure 14 shows a tenth embodiment of the solder ball array mask according to the present invention. In this tenth embodiment, the longitudinal cross-sectional shape of the positioning body 20 differs from that of the first embodiment. The positioning body 20, which is made of a protruding strip, is provided on the opening edge of the lower opening 18 of the through-hole 12 and comprises a receiving portion 21 that receives and holds the solder ball 2 within the through-hole 12, and a lead-in rib (lead-in portion) 22 that is provided from the upper opening 17 to the lower opening 18 of the through-hole 12 and guides the solder ball 2 to a predetermined position within the through-hole 12. The receiving portion 21 is formed by the lower end of the lead-in rib 22. The lead-in rib 22 is composed of a first rib 34 provided on the upper opening 17 side and a second rib 35 provided on the lower opening 18 side.

[0043] The first rib 34 is provided from the edge of the upper opening 17 of the through hole 12 to the vertical center, and its vertical cross section is formed into a substantially right-angled triangle whose hypotenuse is an arc concave toward the inner circumferential surface 19. The second rib 35 is provided from the vertical center of the through hole 12 to the edge of the lower opening 18, and its vertical cross section is formed into a trapezoid whose one leg is formed into a vertical side. The lower end of the first rib 34 and the upper end of the second rib 35 are continuous at the vertical center of the through hole 12. In this embodiment, the receiving surface 23 is omitted, and the solder ball 2 is received by the protruding tip of the receiving portion 21 and held in a predetermined position.

[0044] 11th Embodiment Fig. 15 shows an eleventh embodiment of a solder ball array mask according to the present invention. In this embodiment, the vertical cross-sectional shape of the first rib 34 differs from that of the tenth embodiment. The first rib 34 is provided from the edge of the upper opening 17 of the through hole 12 to the center in the vertical direction, and its vertical cross-sectional shape is formed into a right-angled triangle. The inclination angle of the introduction surface 24 (introduction edge 31) with respect to the vertical line (inner peripheral surface 19 of the through hole 12) is relatively small for the first rib 34 and relatively large for the second rib 35, and the lower end of the first rib 34 and the upper end of the second rib 35 are continuous at the center in the vertical direction of the through hole 12.

[0045] 12th Embodiment FIG. 16 shows a twelfth embodiment of a solder ball array mask according to the present invention. In this twelfth embodiment, the longitudinal cross-sectional shape of the positioning body 20 differs from that of the first embodiment. The positioning body 20, which is made of a protruding strip, is provided on the edge of the lower opening 18 of the through-hole 12 and is configured to receive and hold the solder ball 2 within the through-hole 12, and is configured to include a receiving portion 21 and a lead-in rib (lead-in portion) 22 that is provided from the upper opening 17 to the lower opening 18 of the through-hole 12 and guides the solder ball 2 to a predetermined position within the through-hole 12. The longitudinal cross-sectional shape of the lead-in rib 22 is formed into a substantially right-angled triangle whose hypotenuse is an arc recessed toward the inner circumferential surface 19. The receiving portion 21 is configured at the lower end of the lead-in rib 22, and the receiving surface 23 is omitted, so that the solder ball 2 is received by the protruding tip of the receiving portion 21 and held in a predetermined position.

[0046] 17 shows a solder ball array mask according to a thirteenth embodiment of the present invention. In this thirteenth embodiment, the cross-sectional shape of the introduction rib 22 differs from that of the twelfth embodiment. The introduction rib 22 has a right-angled triangular cross-sectional shape. The receiving portion 21 is formed at the lower end of the introduction rib 22, and the receiving surface 23 is omitted, so that the solder balls 2 are received by the protruding tip of the receiving portion 21 and held in place.

[0047] 18 shows a solder ball array mask according to a fourteenth embodiment of the present invention. In this fourteenth embodiment, the longitudinal cross-sectional shape of the positioning body 20 differs from that of the first embodiment. The positioning body 20, which is made of a protruding strip, is composed of a receiving rib 21 that is provided on the lower opening 18 side of the through-hole 12 and receives and holds the solder balls 2 within the through-hole 12, an introduction rib 22 that is provided on the upper opening 17 side of the through-hole 12 and guides the solder balls 2 to a predetermined position within the through-hole 12, and a step 38 that is provided between the lower end of the introduction rib 22 and the upper end of the receiving rib 21.

[0048] The receiving rib 21 is a ridge with a constant protrusion dimension, extending from the edge of the lower opening 18 of the through hole 12 to the vertical center. The vertical cross section of the receiving rib 21 is rectangular. The lead-in rib 22 is a ridge formed so that its protrusion dimension gradually increases toward the lower opening 18, extending from the edge of the upper opening 17 of the through hole 12 to the vertical center. The vertical cross section of the lead-in rib 22 is a right-angled triangle. The receiving rib 21 has a relatively small protrusion dimension, while the lead-in rib 22 has a relatively large protrusion dimension, forming a step 38 between the ribs 21 and 22. The lower end of the lead-in rib 22 and the upper end of the receiving rib 21 are continuous with each other at the vertical center of the through hole 12 via the step 38.

[0049] 19 shows a solder ball array mask according to a 15th embodiment of the present invention. In this 15th embodiment, the cross-sectional shape of the introduction rib 22 differs from that of the 14th embodiment. The introduction rib 22 has a rectangular cross-sectional shape. The upper end of the introduction rib 22 protrudes from the edge of the upper opening 17 toward the center of the through-hole 12.

[0050] In addition to the above, the positioning bodies 20 can be configured into various shapes by combining the number and positions shown in the first to fifth embodiments, the cross-sectional shapes shown in the sixth to eighth embodiments, and the longitudinal cross-sectional shapes shown in the ninth to fifteenth embodiments. When multiple positioning bodies 20 are provided, it is not necessary to provide positioning bodies 20 of the same shape, and positioning bodies 20 of different shapes can also be provided on the inner peripheral surface 19 of the through hole 12. The positioning bodies 20 do not need to be provided symmetrically with respect to the imaginary line V.

[0051] As described above, in the mask 1 according to each of the above embodiments, one or more positioning bodies 20 formed to protrude from the inner peripheral surface 19 of the through hole 12 guide and hold the solder ball 2 at a predetermined position in the through hole 12. Therefore, compared to conventional masks that hold the solder ball on the inner peripheral surface of the through hole, it is possible to make the opening diameter D1 of the upper opening 17 of the through hole 12 larger than the diameter d of the solder ball 2 by the protrusion dimension of the positioning body 20. This increases the chance that the center of gravity of the solder ball 2 swept by the squeegee brush S will be located above the upper opening 17 of the through hole 12, making it easier to guide the solder ball 2 into the through hole 12. Furthermore, because the opening diameter D1 of the upper opening 17 of the through hole 12 is made larger than the diameter d of the solder ball 2, it is possible to form a gap between the peripheral surface of the solder ball 2 falling into the through hole 12 and the inner peripheral surface 19 of the through hole 12, which prevents the solder ball 2 falling through the through hole 12 from coming into contact with and getting caught on the inner peripheral surface 19. As described above, the mask 1 according to each of the above embodiments allows the solder balls 2 to be inserted into the through-holes 12 more quickly and smoothly than conventional masks.

[0052] Positioning body 20, which is a protrusion formed by extending in the vertical direction from inner peripheral surface 19 of through hole 12, is provided on the lower opening 18 side of through hole 12 and includes a receiving portion (receiving rib) 21 that receives and holds solder ball 2 within through hole 12, and an introducing portion (introduction rib) 22 that is provided on the upper opening 17 side of through hole 12 and guides solder ball 2 to a predetermined position within through hole 12. Therefore, solder ball 2 that falls into through hole 12 from upper opening 17 can be accurately guided toward the predetermined position by introducing portion 22, and guided solder ball 2 can be securely held and positioned by receiving portion 21. Therefore, solder ball 2 can be mounted with high precision in the correct position on substrate 3 (the center of electrode 6 in plan view).

[0053] Lead-in portion 22 is formed so that its protruding dimension gradually increases toward lower opening 18, thereby guiding solder ball 2 so that it gradually approaches a predetermined position and can be smoothly introduced into receiving portion 21. In addition, the upper end of lead-in portion 22 is formed by part of the opening edge of upper opening 17 of through-hole 12, which is a round hole, so lead-in portion 22 guides solder ball 2 from the initial stage of its falling into through-hole 12, allowing it to be introduced into receiving portion 21 more smoothly.

[0054] Three or more positioning bodies 20 are provided on the inner peripheral surface 19 of the through hole 12, and when the inner peripheral surface 19 of the through hole 12 is divided into two semi-peripheral surfaces 19a and 19b at any position, a positioning body 20 is provided on each of the semi-peripheral surfaces 19a and 19b. In this way, the solder ball 2 can be supported at three points by the positioning bodies 20, and the solder ball 2 can be positioned at a predetermined position in the through hole 12, so that the solder ball 2 can be mounted accurately in the appropriate position on the substrate 3.

[0055] The positioning bodies 20 are provided at equal intervals around the inner peripheral surface 19 of the through hole 12, so that the positioning bodies 20 uniformly support and position the periphery of the solder ball 2 at three points, and the solder ball 2 can be mounted with high precision in the appropriate position on the substrate 3.

[0056] The positioning body 20 is provided on the inner peripheral surface 19 of the through hole 12 located downstream in the movement direction of the squeegee brush S, which moves on the array mask to drop the solder balls 2 into the through hole 12. This makes it possible for the positioning body 20 to receive the solder balls 2 that are swept downstream in the movement direction of the squeegee brush S and are guided into the upstream half of the upper opening 17 of the through hole 12 and fall into the through hole 12, and the positioning body 20 can accurately guide the solder balls 2 to the specified position.

[0057] When viewed in a plane, when an imaginary line V passing through the center of the through hole 12 is imagined, a positioning body 20 is provided at a position where the imaginary line V directed in the direction of movement of the squeegee brush S intersects with the inner surface 19 of the through hole 12 downstream in the direction of movement of the squeegee brush S, so that the solder ball 2 that is guided into the upstream half of the upper opening 17 of the through hole 12 and falls into the through hole 12 can be reliably received.

[0058] The cross section of the positioning body 20 consisting of a protrusion, which is perpendicular to the vertical direction, is formed into a truncated fan shape, and the positioning body 20 is provided so that the arc on the longer side of the truncated fan shape faces the inner peripheral surface 19 of the through hole 12, so that the solder ball 2 can be guided and held by the concave arc surface, and damage to the solder ball 2 due to contact with the positioning body 20 can be prevented.

[0059] The cross section of the positioning body 20 made of a protrusion, which is perpendicular to the up-down direction, is formed into a trapezoid shape, and the positioning body 20 is arranged so that the base of the longer side of the trapezoid faces the inner peripheral surface 19 of the through-hole 12. This makes it possible to guide and hold the solder ball 2 on a flat surface, preventing the solder ball 2 from being damaged due to contact with the positioning body 20. Furthermore, by bringing the solder ball 2 into point contact with the positioning body 20, the solder ball 2 falling through the through-hole 12 can be prevented from getting caught on the positioning body 20.

[0060] The cross section of the positioning body 20 made of a rib is formed into a fan shape with a rounded main portion, perpendicular to the up-down direction, and the positioning body 20 is arranged so that the arc surface of the fan shape faces the inner peripheral surface 19 of the through hole 12. This makes it possible to guide and hold the solder ball 2 by the arc surface (rounded shape) of the rib, preventing the solder ball 2 from being damaged due to contact with the positioning body 20. In addition, the solder ball 2 and the positioning body 20 are in point contact, preventing the solder ball 2 falling through the through hole 12 from getting caught on the positioning body 20.

[0061] The cross section of the positioning body 20 consisting of a ridge is formed into a fan shape perpendicular to the vertical direction, and the positioning body 20 is provided so that the arc surface of the fan shape faces the inner peripheral surface 19 of the through hole 12, so that the solder ball 2 and the positioning body 20 are in point contact with each other, preventing the solder ball 2 falling through the through hole 12 from getting caught on the positioning body 20.

[0062] The array mask of the present invention can contribute to Goal 9 (Build resilient infrastructure, promote inclusive and sustainable industrialization, foster innovation and promote resilience) and Goal 12 (Promote responsible consumption and production) of the Sustainable Development Goals (SDGs) advocated by the United Nations.

[0063] In the above embodiments, the array mask 1 has been described in which conductors made of solder balls 2 are inserted into the through holes 12 that are round holes, but other examples of the array mask include an array mask in which the through holes are formed as polygonal holes or rounded polygonal holes, and an array mask in which conductors made of columnar (cylindrical) conductive pillars are inserted into the through holes. In these array masks, one or more positioning bodies can be formed on the inner circumferential surface of the through holes, extending toward the center of the hole, to hold and position the conductors (solder balls, conductive pillars) in a predetermined position. [Explanation of symbols]

[0064] 1 Array mask 2 solder balls 3. Circuit Board 12 through hole 17 Top opening 18 Lower opening 19 Inner surface 19a Half of the circumference of the through hole 19b Half circumferential surface of through hole 20 Positioning body 21 Receiving portion (receiving rib) 22 Lead-in section (leading-in rib) d solder ball diameter D1 Upper opening diameter S Sweeping tool (squeegee brush) V: An imaginary line passing through the center of the through hole

Claims

1. An array mask for mounting solder balls (2) at predetermined positions on a substrate (3) by dropping the solder balls (2) into through holes (12) corresponding to a predetermined array pattern, The array mask is characterized in that one or more positioning bodies (20) are formed on the inner surface (19) of the through hole (12), which is a round hole with an upper opening (17) having an opening diameter (D1) larger than the diameter (d) of the solder ball (2), and which extend toward the center of the hole to guide the solder ball (2) inserted into the through hole (12) toward a predetermined position and hold and position the solder ball (2) in the predetermined position.

2. 2. The array mask according to claim 1, wherein the positioning body (20) is a protrusion formed by extending in the vertical direction along the inner peripheral surface (19) of the through hole (12), and includes a receiving portion (21) provided on the lower opening (18) side of the through hole (12) for receiving and holding the solder ball (2) within the through hole (12), and an introduction portion (22) provided on the upper opening (17) side of the through hole (12) for guiding the solder ball (2) to a predetermined position within the through hole (12).

3. The introduction portion (22) is formed so that the protruding dimension gradually increases toward the lower opening (18), 3. An array mask according to claim 2, wherein the upper end of the introduction portion (22) is formed by a part of the opening edge of the upper opening (17) of the through hole (12) which is a round hole.

4. Three or more positioning bodies (20) are provided on the inner peripheral surface (19) of the through hole (12), 2. An array mask according to claim 1, wherein when the inner peripheral surface (19) of the through hole (12) is divided into two semi-peripheral surfaces (19a, 19b) at any position, a positioning body (20) is provided on each of the semi-peripheral surfaces (19a, 19b).

5. 5. An array mask according to claim 4, wherein the positioning bodies (20) are provided at equal intervals in the circumferential direction on the inner peripheral surface (19) of the through-hole (12).

6. 2. An array mask according to claim 1, wherein a positioning body (20) is provided on an inner peripheral surface (19) of a through hole (12) located downstream in the direction of movement of a sweeping tool (S) that moves over the array mask to drop the solder balls (2) into the through hole (12).

7. In a plan view, when a virtual line (V) passing through the center of the through hole (12) is assumed, 7. The array mask according to claim 6, wherein a positioning body (20) is provided at a position where a virtual line (V) directed in the direction of movement of the sweeping tool (S) intersects with an inner peripheral surface (19) of the through hole (12) downstream in the direction of movement of the sweeping tool (S).

8. 3. An array mask according to claim 2, wherein the cross-sectional shape of the positioning body (20) consisting of a protrusion, which is perpendicular to the vertical direction, is formed into a frustum shape, and the positioning body (20) is arranged so that the arc on the longer side of the frustum faces the inner surface (19) of the through hole (12).

9. 3. The array mask according to claim 2, wherein the cross-sectional shape of the positioning body (20) consisting of a protrusion, which is perpendicular to the vertical direction, is formed into a trapezoidal shape, and the positioning body (20) is arranged so that the base of the longer side of the trapezoid faces the inner surface (19) of the through hole (12).

10. 3. The array mask according to claim 2, wherein the cross-sectional shape of the positioning body (20) consisting of a protrusion, which is perpendicular to the vertical direction, is formed into a fan shape with the essential part rounded, and the positioning body (20) is provided so that the arc of the fan shape faces the inner surface (19) of the through hole (12).

11. 3. The array mask according to claim 2, wherein the cross-sectional shape of the positioning body (20) consisting of a protrusion, which is perpendicular to the vertical direction, is formed in a fan shape, and the positioning body (20) is arranged so that the arc of the fan shape faces the inner surface (19) of the through hole (12).

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