Mask for arrangement

Abstract

To prevent defective mounting of solder balls caused by the upper end of a protruding wall abutting against the lower surface of a mask body for example, in a mask for arrangement applied to a substrate having a protruding wall such as a dam for underfill.SOLUTION: A mask for arrangement includes a mask body 10 in which a large number of through holes 12 are formed, and a protrusion 18 that protrudes downward from a lower surface 15 of the mask body 10 and supports the mask body 10 in a position spaced apart from an upper surface 17 of a substrate 3. In the mask for arrangement, a recess 19 is formed in the lower surface 15 of the mask body 10 to receive an upper portion of a protruding wall 7 that protrudes upward from the upper surface 17 of the substrate 3.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventionally, as a method for forming solder bumps, a BGA (Ball Grid Array) method is known. In this BGA method, a printing process of applying flux to electrodes on a substrate such as a wafer, a flexible substrate, or a rigid substrate, an array process of arranging solder balls on the flux, and a heating process of heating and melting the solder balls are performed to form bumps. And, in the above-described array process, as a method for arranging solder balls on a substrate, there is a pouring method using a mask. In this pouring method, an array mask (hereinafter, simply referred to as a "mask" as appropriate) having positioning through-holes through which solder balls can be inserted corresponding to the arrangement pattern of the electrodes on the substrate is used to mount the solder balls on the electrodes of the substrate. Specifically, after aligning the mask with the substrate so that the through-holes and the electrodes coincide, the solder balls supplied onto the mask are swept with a squeegee, a brush, or the like, and one solder ball is inserted into each through-hole. Then, by fixing the solder balls to the flux, the solder balls are temporarily mounted at predetermined positions on the substrate.

[0003] As a known example of this type of array mask, for example, there is one disclosed in Patent Document 1. In the mask described in Patent Document 1, a large number of supporting protrusions are formed on the lower surface of a mask body having through-holes. During the operation of arranging the solder balls, the lower surface of the protrusion is brought into contact with the upper surface of the substrate, so that the opposing interval between the mask body and the substrate is ensured, and thereby it is possible to prevent the flux applied on the electrodes from adhering to the lower surface of the mask body. An array mask having a similar configuration is also disclosed in Patent Document 2 by the applicant of the present patent.

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. 2008-263053 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] When mounting an electronic component on a substrate using solder bumps, for the purpose of mechanically reinforcing the electronic component with respect to the substrate, a liquid resin may be applied between the two (the substrate and the electronic component) and cured to form a so-called "underfill". On the surface of the substrate on which such an underfill is formed, a dam composed of a protruding wall for preventing the outflow of the liquid resin outside the application area is provided in advance. When the height dimension of such a dam is smaller than the height dimension of the protruding portion, the lower end of the protruding portion can be brought into contact with the upper surface of the substrate, and the alignment mask can be stably placed on the substrate. On the other hand, when the height dimension of the dam is larger than the height dimension of the protruding portion, before the protruding portion comes into contact with the substrate, the upper end of the dam will hit the lower surface of the mask body first, and a gap will be generated between the protruding portion and the substrate. In this case, since the facing interval between the mask body and the substrate becomes larger than the preset facing interval, the alignment mask cannot hold the solder ball on the inner surface of the through hole, and there is a risk of mounting defects such as the solder ball being mounted at a position deviated from the electrode.

[0006] An object of the present invention is to prevent the occurrence of mounting defects of solder balls due to the upper end of a protruding wall, such as a dam for underfill, coming into contact with the lower surface of the mask body in an alignment mask applied to a substrate provided with the protruding wall. [Means for Solving the Problems]

[0007] The present invention is directed to an array mask for mounting solder balls 2 at predetermined positions on a substrate 3 by pouring the solder balls 2 into through holes 12 corresponding to a predetermined array pattern. This array mask includes a mask body 10 in which a large number of through holes 12 are formed, and protrusions 18 projecting downward from the lower surface 15 of the mask body 10 to support the mask body 10 in a posture separated from the upper surface 17 of the substrate 3. And, a recessed portion 19 for receiving the upper portion of a protruding wall 7 projecting upward from the upper surface 17 of the substrate 3 is recessed and formed on the lower surface 15 of the mask body 10, which is characterized in that.

[0008] In a placement posture where the protrusion 18 is in contact with the upper surface 17 of the substrate 3, a clearance gap G is formed between the outer surface of the protruding wall 7 that has entered the recessed portion 19 and the bottom surface 20 and the peripheral surface 21 of the recessed portion 19.

[0009] When the depth dimension of the recessed portion 19 is defined as D and the thickness dimension of the mask body 10 is defined as T, it is preferable that the depth dimension D of the recessed portion 19 is set to 80% or less of the thickness dimension T of the mask body 10.

[0010] When the height dimension of the protrusion 18 is defined as H1, the thickness dimension of the mask body 10 is defined as T, and the sum of the height dimension H1 and the thickness dimension T is defined as the total mask dimension H3, it is preferable that the height dimension H1 of the protrusion 18 is set to 50% or more and 70% or less of the total mask dimension H3.

[0011] On the upper surface 14 of the mask body 10, a bulging portion 45 for increasing the thickness of the mask body 10 is formed in a protruding shape corresponding to the recessed portion 19.

Effects of the Invention

[0012] As in the mask for arrays of the present invention, when a recessed portion 19 for receiving the upper portion of the protruding wall 7 protruding upward from the upper surface 17 of the substrate 3 is formed in a concave shape on the lower surface of the mask body 10, even for a substrate 3 in which the height dimension H2 of the protruding wall 7 exceeds the height dimension H1 of the protruding portion 18, by receiving the protruding wall 7 in the recessed portion 19, the lower surface 15 of the mask body 10 comes into contact with the upper end of the protruding wall 7, that is, it is possible to prevent the mask body 10 from hitting the protruding wall 7 first and being received. As described above, according to the mask 1 of the present invention, since the tip of the protruding portion 18 can be surely brought into contact with the upper surface 17 of the substrate 3, the array operation of the solder balls 2 can be advanced while maintaining the facing interval between the lower surface 15 of the mask body 10 and the upper surface 17 of the substrate 3 at a preset distance. Further, according to the present invention, it is possible to prevent the occurrence of mounting defects of the solder balls 2 due to the upper end of the protruding wall 7 coming into contact with the lower surface of the mask body 10.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0014] (First Embodiment) FIGS. 1 to 5 show a first embodiment of the mask for array according to the present invention. The vertical direction corresponds to the thickness direction of the mask for array, and the dimensions such as thickness in each figure are shown schematically rather than showing the actual state. This mask for array (hereinafter simply referred to as a mask) 1 is used in the array operation of solder balls 2 in the creation of BGA-type solder bumps.

[0015] In FIG. 2, reference numeral 3 indicates a substrate (workpiece) on which the solder balls 2 are to be mounted by the mask 1. This substrate 3 is formed by mounting a plurality of semiconductor chips 5 on a base 4 of a glass epoxy substrate, wiring by wire bonding, and then performing transfer molding encapsulation. On the upper surface of the substrate 3, electrodes 6, which are input / output terminals, are formed in a predetermined pattern so as to surround the semiconductor chips 5. Further, on the upper surface of the substrate 3, a dam (protruding wall) 7 is formed to protrude upward so as to surround the semiconductor chips 5 and the electrodes 6. The dam 7 is composed of a rectangular frame-shaped protrusion formed simultaneously with the creation of the substrate 3, and is for preventing the liquid resin (liquid resin for underfill formation) applied between the substrate 3 and the electronic components from flowing more than necessary when forming the underfill. The underfill is provided for the purpose of increasing the bonding strength between the substrate 3 and the electronic components mounted on the substrate 3 using solder bumps. On the electrodes 6, a flux 8 for adhesively holding the solder balls 2 temporarily is applied in the printing process prior to the array operation of the solder balls 2. The dam 7 can also prevent the movement of this flux and solder (paste, balls, peeled bumps, etc.). The shape of the dam 7 may be a lattice shape, an L shape, or a pair of vertical bars (horizontal bars).

[0016] As shown in FIG. 2, the mask 1 is composed of a mask body 10 formed by electroforming using a nickel alloy such as copper, nickel, or nickel cobalt, or other electrodeposited metal as a material, and a frame body 11 joined so as to surround the mask body 10. The frame body 11 is a square frame body, and its outer peripheral shape coincides with the outer peripheral shape of the mask body 10. The metal constituting the frame body 11 is preferably made of a metal (low thermal expansion material) having a smaller coefficient of thermal expansion than the metal constituting the mask body 10, such as 42 alloy, invar material, or SUS430. On the board surface of the mask body 10 surrounded by the frame body 11, a large number of pattern regions 13 having a large number of independent through holes 12 for injecting solder balls 2 are formed corresponding to the respective semiconductor chips 5. The frame body 11 serves both as a holding member for holding the mask body 10 and as a reinforcing member for reinforcing the mask body 10.

[0017] As shown in FIG. 1, each through hole 12 is a straight round hole that penetrates the mask body 10 in the vertical direction (thickness direction) and has openings on the upper and lower surfaces 14 and 15, and is formed at a position corresponding to the arrangement pattern of the electrodes 6 of each semiconductor chip 5 on the substrate 3. The solder ball 2 is a sphere having a diameter d of 100 μm or less, and the opening diameter of each through hole 12 has a dimension slightly larger than the diameter d of the ball 2 in order to receive and hold the solder ball 2 on the inner surface 16 of the hole.

[0018] When the mask 1 is placed on the substrate 3 during the array operation of the solder balls 2, at this time, in order to support the mask body 10 in a posture floating away from the upper surface 17 of the substrate 3, a protrusion 18 is provided on the lower surface 15 of the mask body 10. Specifically, as shown in FIG. 1, on the lower surface 15 side of the mask body 10, that is, on the opposing surface side facing the substrate 3, a large number of protrusions 18 for securing an opposing interval with the substrate 3 are integrally formed on the mask body 10 so as to protrude downward. Each protrusion 18 is formed in a columnar shape whose height dimension H1 is approximately equal to or slightly smaller than half (radius) of the diameter d of the solder ball 2. The protrusions 18 are not limited to being independently formed, and can be provided in a lattice frame shape so as to surround the pattern region 13. Note that although the protrusions 18 are integrally formed with the mask body 10, those formed separately can also be integrally joined to the mask body 10. The shape of the protrusions 18 is not limited to a columnar shape and may be a rib shape.

[0019] When the height dimension H2 (see FIG. 1) of the dam 7 is formed larger than the height dimension H1 of the protrusion 18, the mask 1 placed on the substrate 3 is such that, at the portion corresponding to the dam 7, the lower surface 15 of the mask body 10 comes into contact with the upper end of the dam 7 before the lower end of the protrusion 18 comes into contact with the upper surface of the substrate 3. Thus, the mask body 10 is received by the dam 7. When the mask body 10 is partially received by the dam 7 in this way, the lower end of the protrusion 18 does not come into contact with the upper surface 17 of the substrate 3, so the opposing interval between the lower surface 15 of the mask body 10 and the upper surface 17 of the substrate 3 becomes larger than the preset distance. In this way, when the distance of the opposing interval becomes large, the solder ball 2 cannot be held by the inner surface 16 of the through hole 12 during the array operation of the solder balls 2, and there is a possibility that the solder ball 2 is mounted at a position deviated from the arrangement position of the electrode 6. Therefore, in the mask 1 of the present embodiment, a structure for avoiding contact between the mask body 10 and the dam 7 is provided during the array operation of the solder balls 2.

[0020] Specifically, as shown in FIG. 1, in order to avoid contact between the mask body 10 and the dam 7 when the mask 1 is placed on the substrate 3, a recessed portion 19 for receiving the upper part of the dam 7 is formed in a concave shape on the lower surface 15 of the mask body 10 corresponding to the dam 7. The recessed portion 19 is composed of a square frame-shaped concave groove that opens to the lower surface 15 side of the mask body 10 and has an opening shape that is one size larger than the dam 7. The shape of the groove cross-section of the recessed portion 19 is rectangular. The depth dimension D of the recessed portion 19 is preferably set to a dimension such that when the dam 7 enters the recessed portion 19, the bottom surface (upper surface) 20 of the recessed portion 19 and the upper end surface of the dam 7 do not come into contact. In the present embodiment, the depth dimension D of the recessed portion 19 is set to a dimension where the dam 7 does not come into contact. From the above, a clearance gap G is formed between the outer surface of the dam 7 that has entered the recessed portion 19 and the bottom surface 20 and the peripheral surface 21 (the inner surface of the recessed portion 19) of the recessed portion 19.

[0021] The above clearance gap G is not essential, and the recessed portion 19 may be in a form that fits the dam 7. In this case, it can contribute to improving the positioning accuracy of the mask 1 with respect to the substrate 3 and the mounting stability. The shape of the groove cross-section of the recessed portion 19 is not limited to a rectangular shape, and may be a trapezoidal shape, a polygonal shape, or a semi-circular shape. The concave groove constituting the recessed portion 19 may be in a form where at least a part of the bottom surface 20 communicates with the upper surface 14 of the mask body 10. In this case, the opening diameter of the communication portion should be smaller than the diameter d of the solder ball 2. The recessed portion 19 can also be used as a relief for the mounted objects (for example, semiconductor chips 5 and bumps, etc.) mounted on the substrate 3.

[0022] It is preferable that the depth dimension D of the recessed portion 19 is formed such that it is 80% or less of the thickness dimension T of the mask body 10. This is because if the depth dimension D of the recessed portion 19 exceeds 80% of the thickness dimension T of the mask body 10, the strength of the portion corresponding to the recessed portion 19 may be insufficient, and the durability of the mask body 10 may decrease. More preferably, the depth dimension D of the recessed portion 19 is set to be 5% or more and 80% or less of the thickness dimension T of the mask body 10. In the present embodiment, the depth dimension D of the recessed portion 19 is set to 60% of the thickness dimension T of the mask body 10.

[0023] Further, it is preferable that the height dimension H1 of the protrusion 18 is set to be 50% or more and 70% or less of the total mask dimension H3 (see FIG. 1), which is the sum of the thickness dimension T of the mask body 10 and the height dimension H1 of the protrusion 18. If the height dimension H1 of the protrusion 18 is less than 50% of the total mask dimension H3, the flux 8 applied to the electrode 6 is more likely to adhere to the lower surface 15 of the mask body 10. If the height dimension H1 of the protrusion 18 exceeds 70% of the total mask dimension H3, the load acting on the protrusion 18 when the mask 1 is placed on the substrate 3 increases, and the durability of the mask 1 decreases. In this embodiment, the height dimension H1 of the protrusion 18 is set to 55% of the total mask dimension H3. The total mask dimension H3 in the array mask is set to be about 30 to 120 μm.

[0024] For the array operation of the solder balls 2, first, the mask 1 is aligned with the substrate 3, and then the mask 1 is placed on the substrate 3. At this time, by receiving the dam 7 in the recess 19, contact with the lower surface 15 of the mask body 10 is avoided, and the lower end of the protrusion 18 contacts the upper surface 17 of the substrate 3. As described above, the mask 1 can be stably placed on the substrate 3 with an appropriate opposing interval formed between the lower surface 15 of the mask body 10 and the upper surface 17 of the substrate 3.

[0025] Subsequently, a large number of solder balls 2 are supplied onto the mask 1, and the solder balls 2 are dispersed on the mask 1 using a squeegee brush, and the solder balls 2 are inserted into the through holes 12 one by one. Since the height dimension H1 of the protrusion 18 is set to be slightly smaller than half (radius) of the diameter d of the solder ball 2, the solder ball 2 inserted into the through hole 12 is positioned with respect to the electrode 6 by the central portion in the vertical direction of the spherical peripheral surface having the maximum diameter in the horizontal direction being received by the inner surface 16 of the hole of the through hole 12. The solder balls 2 inserted into the through holes 12 are adhesively held to the flux 8 in a temporarily fixed manner. Finally, the mask 1 is lifted vertically and removed from the substrate 3, so that the solder balls 2 are mounted on the electrodes 6 and the array operation is completed.

[0026] FIG. 3 to FIG. 5 show an example of a method for manufacturing the mask 1 according to the present embodiment. First, as shown in FIG. 3(a), a first photoresist layer 27 is formed on the surface of a master mold 26 made of, for example, stainless steel or brass having conductivity, and a first pattern film 28 having a light-transmitting hole 28a corresponding to the protrusion 18 is adhered onto the first photoresist layer 27. The first photoresist layer 27 is formed by laminating one or several negative-type photosensitive dry film resists to a predetermined height and performing thermocompression bonding. Next, the first photoresist layer 27 is exposed by irradiating ultraviolet light with an ultraviolet lamp 29, and after performing each process of development and drying, the unexposed portion is dissolved and removed, thereby forming a first pattern resist 30 composed of a straight first resist body 30a corresponding to the protrusion 18 on the master mold 26 as shown in FIG. 3(b).

[0027] Subsequently, the master mold 26 is placed in an electroforming bath (plating bath) set under predetermined conditions, and as shown in FIG. 3(c), within the height range of the first resist body 30a, electroforming (plating) of an electrodeposited metal such as a nickel alloy is performed on the surface of the master mold 26 not covered by the first resist body 30a of the master mold 26. After that, by dissolving and removing the first pattern resist 30, a first electroformed layer 31 as shown in FIG. 3(d) is formed on the master mold 26. The formation height of the first electroformed layer 31 coincides with the height dimension H1 of the protrusion 18. Note that the first pattern resist 30 can also proceed to the next step without being removed. In this case, the first pattern resist 30 may be dissolved and removed together with the second pattern resist 34 (described later).

[0028] Subsequently, as shown in Fig. 4(a), a second photoresist layer 32 is formed on the surface not covered by the first electroformed layer 31 of the master mold 26 and on the surface of the first electroformed layer 31, and a second pattern film 33 having a light-transmitting hole 33a corresponding to the recessed portion 19 is adhered onto this second photoresist layer 32. The second photoresist layer 32 is formed in the same manner as the previous first photoresist layer 27. Next, ultraviolet light is irradiated onto the second photoresist layer 32 with an ultraviolet lamp 29 to expose it. After performing the processes of development and drying, the unexposed portions are dissolved and removed, thereby forming a second pattern resist 34 composed of a second resist body 34a having a straight hole corresponding to the recessed portion 19 on the master mold 26 and the first electroformed layer 31, as shown in Fig. 4(b).

[0029] Subsequently, the master mold 26 is placed in an electroforming bath (plating bath) adjusted to predetermined conditions, and as shown in Fig. 4(c), within the height range of the second resist body 34a, electroplating metal such as nickel alloy is electroformed (plated) on the surface of the first electroformed layer 31 not covered by the second resist body 34a. After that, the second pattern resist 34 is dissolved and removed, thereby forming a second electroformed layer 35 on the first electroformed layer 31 as shown in Fig. 4(d). The formation height of the second electroformed layer 35 is in agreement with the depth dimension D of the recessed portion 19. In the above description, the second electroformed layer 35 (metal) is formed corresponding to the recessed portion 19, but the metal can also be replaced with resin (resist body).

[0030] Subsequently, as shown in Fig. 5(a), a third photoresist layer 36 is formed on the surface not covered by the first electroformed layer 31 of the master mold 26 and on the surfaces of both electroformed layers 31 and 35. On this third photoresist layer 36, a third pattern film 37 having light-transmitting holes 37a corresponding to the outer shape of the through holes 12 and the mask body 10 is adhered. The third photoresist layer 36 is formed in the same manner as the previous first photoresist layer 27. Next, the third photoresist layer 36 is exposed by irradiating ultraviolet light with an ultraviolet lamp 29. After performing the processes of development and drying, the unexposed portion is dissolved and removed, thereby forming a third pattern resist 38 composed of straight third resist bodies 38a corresponding to the through holes 12 and the mask body 10 on the first electroformed layer 31 as shown in Fig. 5(b). Note that the third resist body 38a forming a hole corresponding to the outer shape of the mask body 10 is not shown.

[0031] Subsequently, after performing a peeling treatment or cover plating on the surface not covered by the first electroformed layer 31 of the master mold 26 and on the surfaces of both electroformed layers 31 and 35, the master mold 26 is placed in an electroforming bath (plating bath) prepared under predetermined conditions, and within the height range of the third resist body 38a, electroplating (plating) a plating metal such as nickel alloy is performed on the surface not covered by the first electroformed layer 31 of the master mold 26 and on the surfaces of both electroformed layers 31 and 35 to form a third electroformed layer 39 on the upper surfaces of the master mold 26, the first electroformed layer 31, and the second electroformed layer 35. Further, after the formation of the third electroformed layer 39, a polishing treatment is performed on the upper surfaces of the third electroformed layer 39 and the third resist body 38a to finish the upper surface of the third electroformed layer 39 flat as shown in Fig. 5(c). Next, by peeling the third electroformed layer 39 from the master mold 26 and both electroformed layers 31 and 35, a mask body 10 having a protruding portion 18 formed protruding on the lower surface 15 and a recessed portion 19 formed in a concave shape, and having a through hole 12 penetrating the disk surface is obtained as shown in Fig. 5(d). The formation thickness of the third electroformed layer 39 formed on the upper surface of the first electroformed layer 31 matches the thickness dimension T of the mask body 10. Finally, by integrally fixing the frame body 11 to the upper surface 14 of the mask body 10, a mask 1 as shown in Fig. 2 can be obtained. Note that after the formation of the third electroformed layer 39, a polishing treatment may be performed on its upper surface as necessary to improve the flatness of the upper surface 14 of the mask body 10.

[0032] (Second Embodiment) FIG. 6 shows a second embodiment of the mask for an array according to the present invention. In this embodiment, the difference from the previous first embodiment is that a bulging portion 45 for partially thickening the mask body 10 is provided on the upper surface 14 of the mask body 10. The bulging portion 45 is formed to protrude on the upper surface 14 side of the mask body 10 corresponding to the recessed portion 19. By providing the bulging portion 45 on the upper surface 14 of the mask body 10, the thickness from the bottom surface 20 of the recessed portion 19 to the upper surface 14 of the mask body 10 is increased, and a decrease in the structural strength of the mask body 10 due to the formation of the recessed portion 19 can be suppressed. Further, even in the mask body 10 in which the recessed portion 19 is formed, the thickness of the entire mask body 10 can be made uniform by providing the bulging portion 45.

[0033] The mask 1 of this embodiment is created through substantially the same steps as the manufacturing method of the previous first embodiment (see FIGS. 3 to 5), except that the polishing process is not performed after the formation of the third electroformed layer 39. Since electroforming (plating) has a uniform growth amount in the thickness direction, a step is generated between the portion corresponding to the first electroformed layer 31 and the portion corresponding to the second electroformed layer 35, and a bulge that becomes the bulging portion 45 is formed on the upper surface of the third electroformed layer 39. Incidentally, if necessary, by performing electroforming (plating) while controlling to increase the current density of the portion corresponding to the second electroformed layer 35 during electroforming (plating) of the third electroformed layer 39, the portion corresponding to the second electroformed layer 35 can be formed to be thicker than other portions. Since the rest is the same as the first embodiment, the same members are denoted by the same reference numerals and the description thereof is omitted.

[0034] In the mask 1 according to each of the above embodiments, since the recessed portion 19 for receiving the upper portion of the dam 7 is formed in a concave shape on the lower surface 15 of the mask body 10, even for a substrate 3 in which the height dimension H2 of the dam 7 exceeds the height dimension H1 of the protrusion 18, by receiving the dam 7 in the recessed portion 19, the lower surface 15 of the mask body 10 can be prevented from coming into contact with the upper end of the dam 7, that is, the mask body 10 can be prevented from hitting the dam 7 first and being received. From the above, according to this mask 1, since the tip of the protrusion 18 can be surely brought into contact with the upper surface 17 of the substrate 3, the soldering ball 2 can be arranged while maintaining the facing interval between the lower surface 15 of the mask body 10 and the upper surface 17 of the substrate 3 at a preset distance. Further, according to this mask 1, it is possible to prevent the occurrence of mounting defects of the soldering balls 2 due to the upper end of the dam 7 coming into contact with the lower surface 15 of the mask body 10.

[0035] In the placement posture in which the protrusion 18 is in contact with the upper surface 17 of the substrate 3, a clearance gap G is formed between the outer surface of the dam 7 that has entered the recessed portion 19 and the bottom surface 20 and the peripheral surface 21 of the recessed portion 19. Therefore, contact between the bottom surface 20 and the peripheral surface 21 of the recessed portion 19 and the outer surface of the dam 7 can be suppressed, and the tip of the protrusion 18 can be surely brought into contact with the upper surface 17 of the substrate 3.

[0036] The depth dimension D of the recessed portion 19 is preferably set to 80% or less of the thickness dimension T of the mask body 10. Thereby, it is possible to suppress a decrease in the durability of the mask body 10 due to insufficient strength of the portion of the mask body 10 corresponding to the recessed portion 19.

[0037] The height dimension H1 of the protrusion 18 is preferably set to 50% or more of the total mask dimension H3. Thereby, it is possible to prevent the flux 8 from adhering to the lower surface 15 of the mask body 10 and the inner surface of the through hole 12. Further, the height dimension H1 of the protrusion 18 is preferably set to 70% or less of the total mask dimension H3. Thereby, it is possible to suppress a decrease in the durability of the mask 1 due to an increase in the load acting on the protrusion 18.

[0038] According to the mask 1 in which the bulging portion 45 is formed on the upper surface 14 of the mask body 10 corresponding to the recessed portion 19, it is possible to prevent the thickness dimension T of the mask body 10 from being partially formed to be thin, so that it is possible to suppress a decrease in the structural strength of the mask body 10 due to the formation of the recessed portion 19.

[0039] The array mask according to the present invention can contribute to Goal 9 (Build the infrastructure for industry and technological innovation) and Goal 12 (Responsibility to produce, responsibility to use) of the Sustainable Development Goals (SDGs) proposed by the United Nations. In addition, the structure of the array mask according to the present invention can also be applied to various metal masks such as for solder ball adsorption, screen printing masks, or evaporation.

Explanation of reference numerals

[0040] 1 Mask for array 2 Solder ball 3 Substrate 7 Protruding wall (dam) 10 Mask body 12 Through hole 15 Lower surface of the mask body 17 Upper surface of the substrate 18 Protruding portion 19 Recessed portion 45 Bulging portion D Depth dimension of the recessed portion G Margin gap H1 Height dimension of the protruding portion H3 Total mask dimension T Thickness dimension of the mask body

Claims

1. An array mask for mounting solder balls (2) at predetermined positions on a substrate (3) by pouring the solder balls (2) into through holes (12) corresponding to a predetermined array pattern, comprising: a mask body (10) in which a large number of through holes (12) are formed; and protrusions (18) protruding downward from the lower surface (15) of the mask body (10) for supporting the mask body (10) in a posture separated from the upper surface (17) of the substrate (3). An array mask, characterized in that a recessed portion (19) for receiving an upper portion of a protruding wall (7) protruding upward from the upper surface (17) of the substrate (3) is recessed in the lower surface (15) of the mask body (10).

2. In a mounted posture where the protrusion (18) is in contact with the upper surface (17) of the substrate (3), The array mask according to claim 1, wherein a clearance gap (G) is formed between the outer surface of the protruding wall (7) that has entered the recessed portion (19) and the bottom surface (20) and the peripheral surface (21) of the recessed portion (19).

3. When the depth dimension of the recessed portion (19) is defined as (D) and the thickness dimension of the mask body (10) is defined as (T), the depth dimension (D) of the recessed portion (19) is set to 80% or less of the thickness dimension (T) of the mask body (10). The array mask according to claim 1.

4. When the height dimension of the protrusion (18) is defined as (H1), the thickness dimension of the mask body (10) is defined as (T), and the sum of the height dimension (H1) and the thickness dimension (T) is defined as the total mask dimension (H3), the height dimension (H1) of the protrusion (18) is set to 50% or more and 70% or less of the total mask dimension (H3). The array mask according to claim 1.

5. On the upper surface (14) of the mask body (10), a bulging portion (45) for increasing the wall thickness of the mask body (10) is formed in a protruding shape corresponding to the recessed portion (19). The array mask according to claim 1.

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