JP7564926B2 - Metal Mask - Google Patents

Description

The present invention relates to a metal mask for mounting conductive pillars at predetermined positions on a workpiece by dropping the conductive pillars into through holes corresponding to a predetermined arrangement pattern .

As an example of a metal mask, an array mask for mounting conductive balls made of solder at predetermined positions on a workpiece is known, for example from Patent Document 1. The array mask of Patent Document 1 has a plurality of openings formed therein for dropping the conductive balls. The openings are provided to correspond to the formation pattern of the electrode pads on the substrate (workpiece). A slope-shaped ball guide portion is formed on the upper periphery of the opening, and the ball guide portion is composed of an inclined surface that slopes gently downward toward the opening. When dropping the conductive balls, a large number of conductive balls are supplied onto the array mask and dispersed with a squeegee brush or the like, so that the ball guide portion guides the conductive balls toward the openings, allowing the conductive balls to be smoothly dropped into the openings.

JP 2011-44616 A

In recent years, in surface-mount packaged electronic elements and the like, the formation pattern of electrodes for connecting to a circuit board has become increasingly dense, and cylindrical conductive pillars that have a higher aspect ratio (height/diameter ratio) and allow for a narrower mounting pitch are being adopted in place of conventional conductive balls. In the array mask of Patent Document 1, the structure of the opening and ball guide portion is optimized to allow the conductive balls to be smoothly dropped. However, even if the structure of the array mask of Patent Document 1 is applied to an array mask for cylindrical conductive pillars, the same effect cannot be obtained. This is because, in order for the cylindrical conductive pillars to fall into the openings (arrangement through holes), one end of the conductive pillars must be oriented toward the openings. Furthermore, the conductive pillars need to slide down the ball guide portion with one end facing the opening. However, it is difficult for the conductive pillars to slide down the ball guide portion formed with a gently sloping surface. Furthermore, if the conductive pillar rolls down the ball guide section while in a lying position with the circumferential surface facing the opening, it cannot drop into the opening and the conductive pillar blocks the opening, making it impossible to drop into the opening.

An object of the present invention is to provide a metal mask that can mount conductive pillars at predetermined positions on a workpiece with high precision .

The present invention is directed to an array mask in which cylindrical conductive pillars 2 are dropped into array through holes 12 corresponding to a predetermined array pattern, and the conductive pillars 2 are mounted at predetermined positions on the workpiece 3. The array through holes 12 are provided with an introduction hole portion 15 that opens on the surface of the mask body 10 and guides the conductive pillars 2 into the interior of the array through holes 12, and a holding hole portion 16 that is provided below the introduction hole portion 15 and positions the conductive pillars 2, and the lower end of the introduction hole portion 15 and the upper end of the holding hole portion 16 are smoothly continuous. The introduction hole portion 15 is formed in a bell-mouth shape that expands toward the surface side of the mask body 10, and the holding hole portion 16 is characterized in that the opening diameter D1 of the hole portion 16 is formed as a straight hole that is set slightly larger than the diameter of the conductive pillars 2.

The array through-hole 12 can be configured to have an escape hole portion 17 below the retaining hole portion 16, the escape hole portion 17 having an opening diameter D3 larger than the opening diameter D1 of the retaining hole portion 16.

When the total height dimension of the introduction hole portion 15 and the retention hole portion 16 is H1 and the height dimension of the escape hole portion 17 is H2, the height dimension H1 of the former is set to be equal to or greater than the height dimension H2 of the latter.

When the height dimension of the introduction hole portion 15 is H3 and the height dimension of the retention hole portion 16 is H4, the latter height dimension H4 is set to be equal to or greater than the former height dimension H3.

The curvature of the cross-sectional shape of the introduction hole 15 is formed so that it varies in the circumferential direction of the introduction hole 15.

The curvature of the cross-sectional shape of the introduction hole 15 is formed so that it gradually changes from large to small from one side edge to the opposing other side edge.

The present invention is directed to a method for manufacturing an array mask in which cylindrical conductive pillars 2 are inserted into array through holes 12 corresponding to a predetermined array pattern, thereby mounting conductive pillars 2 at predetermined positions on a workpiece 3. The method for manufacturing an array mask includes a primary patterning step of providing a primary pattern resist 25 having a primary resist body 24 corresponding to the escape hole portion 17 on the surface of a mother mold 21, a secondary patterning step of providing a secondary pattern resist 29 having a secondary resist body 28 corresponding to the introduction hole portion 15 and the holding hole portion 16 on the surface of the primary pattern resist 25, and an electroforming step of forming an electroformed layer 30 by electrodepositing an electrodeposited metal on the mother mold 21. In the electroforming step, the electrodeposited metal is electrodeposited in an area that goes over the upper edge of the primary resist body 24 but does not go over the upper edge of the secondary resist body 28, thereby forming a bell-mouth-shaped introduction hole portion 15.

In the secondary patterning process, the secondary pattern resist 29 is provided with the central axis Q2 of the secondary resist body 28 aligned coaxially with the central axis Q1 of the primary resist body 24.

In the secondary patterning process, the secondary pattern resist 29 is provided with the central axis Q2 of the secondary resist body 28 offset from the central axis Q1 of the primary resist body 24.

In the mask for arranging conductive pillars of the present invention, the introduction hole portion 15 and the holding hole portion 16 constituting the array through hole 12 are smoothly connected, and the introduction hole portion 15 for guiding the conductive pillar 2 is formed in a bell-mouth shape that expands toward the surface side of the mask body 10. In this way, with the introduction hole portion 15 formed in a bell-mouth shape, when the conductive pillar 2 is dropped into the array through hole 12, the conductive pillar 2 in the recumbent position can be dropped along the curved surface of the introduction hole portion 15 while changing its position to an upright position, and the conductive pillar 2 can be introduced and guided into the array through hole 12. In detail, when the center of gravity position of the conductive pillar 2 in the recumbent position exceeds the upper edge of the introduction hole portion 15 and is positioned on the array through hole 12, one end of the conductive pillar 2 positioned on the array through hole 12 can be tilted downward with the upper edge of the introduction hole portion 15 as a fulcrum. As a result, the conductive pillar 2 in the recumbent position can be gradually changed from the recumbent position to the upright position. Furthermore, at the same time as changing the posture to the upright posture, the conductive pillar 2 can be slid into the array through hole 12 along the introduction hole portion 15. Therefore, with the array mask of the present invention, the conductive pillar 2 can be smoothly dropped into the array through hole 12, so that the mounting work of the conductive pillar 2 on the workpiece 3 can be completed in a short time.

In addition, the straight-shaped retaining hole 16, which has an opening diameter D1 set slightly larger than the diameter of the conductive pillar 2, allows the conductive pillar 2 introduced and guided by the introduction hole 15 and dropped into the array through hole 12 to be received and positioned by the inner surface of the retaining hole 16. Therefore, with the array mask of the present invention, the conductive pillar 2 can be accurately positioned by the retaining hole 16, and further, tilting or shifting of the conductive pillar 2 within the array through hole 12 can be prevented, so that the conductive pillar 2 can be mounted accurately at a predetermined position on the workpiece 3.

According to the arrangement through hole 12 having the escape hole portion 17 having an opening diameter D3 larger than the opening diameter D1 of the retaining hole portion 16 on the lower side of the retaining hole portion 16, the length of the engagement portion of the conductive pillar 2 and the retaining hole portion 16 in the axial direction can be made smaller than that of the arrangement through hole 12 without the escape hole portion 17. Therefore, after the conductive pillar 2 is mounted on the work 3, the array mask can be separated from the work 3 with a smaller movement amount, so that the conductive pillar 2 can be prevented from tilting or shifting when the array mask is separated, and the conductive pillar 2 can be mounted at a predetermined position on the work 3 with higher accuracy. In addition, when the array mask is placed on the work 3, the contact area between the work 3 and the array mask can be made as small as possible. This makes it possible to prevent the array mask and the work 3 from being damaged by placing the array mask on the work 3, and improve the durability of the array mask. Furthermore, flux may be applied to the mounting positions of the conductive pillars 2 on the workpiece 3. Even in such cases, the escape holes 17 prevent the flux from adhering to the array mask, eliminating the need to clean the array mask.

When the total height dimension H1 of the introduction hole portion 15 and the retention hole portion 16 is set to be equal to or greater than the height dimension H2 of the escape hole portion 17, the introduction hole portion 15 and the retention hole portion 16 can be formed to a sufficient height even when the escape hole portion 17 is provided below the retention hole portion 16. Therefore, the introduction hole portion 15 can accurately guide the introduction of the conductive pillar 2, and the retention hole portion 16 can accurately position the conductive pillar 2.

By setting the height dimension H4 of the retaining hole 16 to be equal to or greater than the height dimension H3 of the introduction hole 15, the positioning effect of the conductive pillar 2 in the retaining hole 16 can be maximized, and the conductive pillar 2 can be mounted precisely at a predetermined position on the workpiece 3.

By forming the curvature of the cross-sectional shape of the introduction hole portion 15 to change in the circumferential direction of the introduction hole portion 15, the introduction guide function of the conductive pillar 2 can be greatly exerted in the part with small curvature, and the height dimension H4 of the holding hole portion 16 can be increased in the part with large curvature, and the positioning function of the conductive pillar 2 in the holding hole portion 16 can be greatly exerted. Therefore, it is possible to make it easier to partially drop the conductive pillar 2 in the circumferential direction of the introduction hole portion 15, and it is possible to form an array through hole 12 that can accurately position the dropped conductive pillar 2.

If the curvature of the cross-sectional shape of the introduction hole portion 15 is formed so that it gradually changes from large to small from one side edge to the opposite side edge, for example, by forming the array through holes 12 so that the side with the smaller curvature faces the same direction, the conductive pillars 2 can be dropped into the array through holes 12 more quickly by moving the squeegee from the side with the smaller curvature to the side with the larger curvature when dropping the conductive pillars 2, and the installation work can be completed in a shorter time.

According to the manufacturing method of the conductive pillar array mask of the present invention, an array mask having an array through hole 12 with a bell-mouth-shaped introduction hole portion 15 can be manufactured without the need for a separate process for forming the introduction hole portion 15 into a bell-mouth shape. In detail, the edge portion of the growth tip of the electroformed metal that grows beyond the upper edge of the primary resist body 24 grows in a quarter-circular arc shape. Therefore, in the electroforming process, the bell-mouth-shaped introduction hole portion 15 can be formed simply by electroforming the electrodeposited metal to an extent that overcomes the upper edge of the primary resist body 24 but does not overcome the upper edge of the secondary resist body 28. Therefore, the work steps in the manufacturing process of the array mask can be shortened, and the manufacturing cost of the array mask can be reduced.

In the secondary patterning process, if the central axis Q2 of the secondary resist body 28 is positioned coaxially with the central axis Q1 of the primary resist body 24, the distance that it grows beyond the upper edge of the primary resist body 24 can be made uniform in the circumferential direction, so that the cross-sectional shape of the introduction hole portion 15 can be made uniform in the circumferential direction. Therefore, the introduction guide action of the conductive pillar 2 in the introduction hole portion 15 can be exerted uniformly in the circumferential direction, and an array through-hole 12 can be formed into which the conductive pillar 2 can be smoothly dropped from any direction.

In the secondary patterning process, if the central axis Q2 of the secondary resist body 28 is offset from the central axis Q1 of the primary resist body 24, the distance that the secondary resist body 28 grows beyond the upper edge of the primary resist body 24 can be varied in the circumferential direction, so that the cross-sectional shape of the introduction hole portion 15 can be formed so that the curvature gradually changes from large to small in the circumferential direction. At this time, the longer the distance that the secondary resist body 2 grows beyond, the smaller the curvature of the cross-sectional shape becomes. As a result, the side with the smaller curvature can exhibit a large introduction guide effect for the conductive pillar 2, and the height dimension H4 of the holding hole portion 16 can be increased on the side with the larger curvature, so that the positioning effect of the conductive pillar 2 in the holding hole portion 16 can be exhibited greatly. Therefore, the arrangement through-hole 12 that can accurately position the conductive pillar 2 while making it easy to drop the conductive pillar 2 can be easily formed by simply performing the electroforming process.

1 is a vertical sectional front view showing a main part of a mask for arranging conductive pillars according to a first embodiment of the present invention; 1 is a perspective view for explaining an overall structure of a mask for arranging conductive pillars according to a first embodiment of the present invention; 1 is a vertical sectional front view of a mask for arranging conductive pillars according to a first embodiment of the present invention; 3A to 3C are diagrams illustrating a method for manufacturing a mask for arranging conductive pillars according to the first embodiment of the present invention. 3A to 3C are diagrams illustrating a method for manufacturing a mask for arranging conductive pillars according to the first embodiment of the present invention. 11 is a vertical sectional front view showing a main part of a mask for arranging conductive pillars according to a second embodiment of the present invention. FIG. FIG. 11 is a plan view showing a main part of a mask for arranging conductive pillars according to a second embodiment of the present invention. 6A to 6C are diagrams illustrating a method for manufacturing a mask for arranging conductive pillars according to a second embodiment of the present invention. FIG. 11 is a vertical sectional front view of a mask for arranging conductive pillars according to a third embodiment of the present invention.

(First embodiment) FIGS. 1 to 3 show a first embodiment of the metal mask according to the present invention. In this embodiment, the thickness direction of the metal mask is defined as the up-down direction. The dimensions of the thickness, width, and the like in FIGS. 1 to 3 of this embodiment are not shown in actual conditions, but are shown in schematic form. The same applies to the other figures. A metal mask (hereinafter simply referred to as a mask) 1 applied as a mask for arranging conductive pillars is used in the mounting work of conductive pillars 2 in forming electrode posts of an LSI chip. As shown in FIG. 3, the conductive pillar 2 is a cylindrical block made of copper, and has a diameter dimension of 80 μm and a height dimension of 85 μm. In FIG. 2, reference numeral 3 denotes a workpiece on which the conductive pillar 2 is to be mounted by the mask 1, and this workpiece 3 is formed by mounting a plurality of semiconductor chips 5 on a base 4 of a glass epoxy substrate and then molding and sealing it. On the upper surface of the workpiece 3, electrodes 6 as input/output terminals are formed in a predetermined pattern so as to surround the semiconductor chips 5. After the electrode posts are formed, the work 3 is diced along dicing lines shown by dashed lines in FIG. 2 and divided into individual LSI chips.

The mask 1 is composed of a mask body 10 formed by electroforming using nickel-based electrodeposited metal as a material, and a frame-shaped frame 11 attached to surround the mask body 10. A large number of independent array through-holes (through-holes) 12 corresponding to an array pattern that matches the formation pattern of the electrodes 6 are formed on the surface of the mask body 10. The conductive pillars 2 can be mounted at predetermined positions on the workpiece 3 by dropping the conductive pillars 2 into the array through-holes 12. The frame 11 reinforces the mask body 10 and is made of a material with a low thermal expansion coefficient, such as 42 alloy, Invar material, Super Invar material, or SUS430, which is thicker than the mask body 10. The frame 11 is bonded to the outer periphery of the mask body 10 with an adhesive or the like, so that the two are inseparably joined together. The mask body 10 can be formed using nickel alloys such as nickel-cobalt, copper, or other electrodeposited metals as materials.

1, the array through-holes 12 include an introduction hole portion 15 that opens on the surface (upper surface) of the mask body 10 and a retention hole portion 16 provided below the introduction hole portion 15, and the lower end of the introduction hole portion 15 smoothly connects to the upper end of the retention hole portion 16. In addition, the array through-holes 12 include an escape hole portion 17 below the retention hole portion 16.

The introduction hole portion 15 is formed in a bell-mouth shape that widens toward the surface side of the mask body 10, and has the function of guiding the conductive pillar 2 into the arrangement through-hole 12 when the conductive pillar 2 is dropped into the arrangement through-hole 12. The cross-sectional shape of the introduction hole portion 15 is the same in the circumferential direction, and the introduction and guiding function of the conductive pillar 2 in the introduction hole portion 15 can be uniformly exerted in the circumferential direction. In this embodiment, the cross-sectional shape of the introduction hole portion 15 is formed in a quarter arc of a perfect circle.

The retaining hole portion 16 is formed as a straight hole with an opening diameter D1 set slightly larger than the diameter of the conductive pillar 2, and serves to position the conductive pillar 2 dropped into the array through-hole 12. The outer peripheral surface of the conductive pillar 2 comes into contact with the inner peripheral surface of the retaining hole portion 16, thereby preventing tilting or shifting, and positioning the conductive pillar 2.

The escape hole portion 17 is formed as a straight hole having an opening diameter D3 larger than the opening diameter D1 of the retaining hole portion 16, and the central axis P2 of the escape hole portion 17 is located on the same axis as the central axis P1 of the retaining hole portion 16. In this embodiment, the opening diameter D1 of the retaining hole portion 16 is set to 85 μm, the opening diameter D2 of the upper end of the introduction hole portion 15 is set to 125 μm, and the opening diameter D3 of the escape hole portion 17 is set to 145 μm.

The total height dimension H1 of the introduction hole portion 15 and the retention hole portion 16 is set to be larger than the height dimension H2 of the escape hole portion 17, with the former height dimension H1 being 50 μm and the latter height dimension H2 being 40 μm. In this way, by setting the height dimension H1 of the array through holes 12 to be larger than the height dimension H2 of the escape hole portion 17, it is possible to form introduction hole portion 15 and retention hole portion 16 of sufficient height even when the escape hole portion 17 is provided below the retention hole portion 16. Therefore, the introduction hole portion 15 can accurately guide the introduction of the conductive pillar 2, and the retention hole portion 16 can accurately position the conductive pillar 2.

The height dimension H4 of the retaining hole 16 is set to be larger than the height dimension H3 of the introduction hole 15, the latter being 20 μm and the former being 30 μm. In this way, by setting the height dimension H4 of the retaining hole 16 to be larger than the height dimension H3 of the introduction hole 15, the positioning effect of the conductive pillar 2 in the retaining hole 16 can be more reliably exerted.

The mounting operation of the conductive pillars 2 on the workpiece 3 using the mask 1 is performed in the following procedure. This mounting operation is performed using a dedicated arrangement device equipped with a pillar supply device, an excess pillar recovery device, a squeegee brush, etc. First, flux is printed and applied to the surface of the electrode 6 of the workpiece 3 using a screen printing method. The flux is applied to activate the surface of the electrode 6, improving the bonding strength between the electrode 6 and the conductive pillar 2 after reflow, and to temporarily fix the conductive pillar 2 using the adhesiveness of the flux when the conductive pillar 2 is mounted.

Then, the mask 1 is aligned on the workpiece 3 so that the array through holes 12 coincide with the electrodes 6, and then the mask 1 is placed and fixed. At this time, the escape hole portion 17 allows the contact area between the workpiece 3 and the mask 1 to be as small as possible, so that damage to the mask 1 and the workpiece 3 caused by placing the mask 1 on the workpiece 3 can be suppressed, and the durability of the mask 1 can be improved. In addition, the escape hole portion 17 prevents flux from adhering to the mask 1, eliminating the need to clean the mask 1.

Next, a large number of conductive pillars 2 are supplied onto the mask 1, and the conductive pillars 2 are distributed on the mask 1 using a squeegee brush, and the conductive pillars 2 are dropped into each of the array through holes 12 one by one. The conductive pillars 2 are dropped into the array through holes 12 as follows. When the center of gravity of the conductive pillars 2 in a recumbent position dispersed by the squeegee brush exceeds the upper edge of the introduction hole portion 15 and is positioned on the array through hole 12, one end of the conductive pillar 2 positioned on the array through hole 12 tilts downward with the upper edge of the introduction hole portion 15 as a fulcrum. As a result, the conductive pillars 2 in a recumbent position are gradually changed in position from the recumbent position to an upright position. Furthermore, at the same time as the position is changed to the upright position, the conductive pillars 2 slide into the array through holes 12 along the introduction hole portion 15. As a result, the conductive pillars 2 are introduced and guided by the introduction hole portion 15 and smoothly dropped into the array through holes 12. The conductive pillar 2 dropped into the array through-hole 12 is temporarily fixed in place with flux, and is precisely positioned by the inner surface of the retaining hole 16.

After the conductive pillars 2 have been dropped in, any excess conductive pillars 2 remaining on the mask 1 are collected. Finally, the workpiece 3 and mask 1 are released from their fixed positions, and the mask 1 is lifted up and separated, completing the work of mounting the conductive pillars 2 on the workpiece 3. At this time, the escape hole 17 reduces the length of the axial engagement portion of the engagement portion between the conductive pillars 2 and the retaining hole 16, so that the mask 1 can be separated from the workpiece 3 with a small amount of movement, and the conductive pillars 2 can be prevented from tilting or becoming misaligned when the mask 1 is separated.

4 and 5 show a method for manufacturing an array mask according to the first embodiment.
(Primary patterning process)
As shown in Fig. 4(a), a photoresist layer 22 is formed on the entire surface of a conductive matrix 21 made of, for example, stainless steel or brass, and then a pattern film 23 made of a glass mask having circular light-transmitting holes corresponding to the relief hole portions 17 is adhered to the matrix. In this state, ultraviolet light is irradiated to perform exposure, and then development and drying processes are performed. The photoresist layer 22 here is formed by laminating one or several sheets of negative type sheet-shaped photosensitive dry film resist and thermocompression bonding to a predetermined thickness. Next, the photoresist layer 22 in the unexposed portion is dissolved and removed to obtain a primary pattern resist 25 having a disk-shaped primary resist body 24 corresponding to the relief hole portion 17, as shown in Fig. 4(b).

(Secondary Patterning Process)
As shown in FIG. 4(c), a photoresist layer 26 is formed on the entire surface of the mother mold 21 including the portion where the primary pattern resist 25 is formed, and a pattern film 27 made of a glass mask having a circular light-transmitting hole corresponding to the holding hole portion 16 is adhered to the upper surface of the photoresist layer 26. At this time, the pattern film 27 is adhered so that the center of the light-transmitting hole coincides with the central axis Q1 of the primary resist body 24. In this state, ultraviolet light is irradiated to perform exposure, and the processes of development and drying are performed. The photoresist layer 26 here is formed in the same manner as the photoresist layer 22 described above. Next, the photoresist layer 26 in the unexposed portion is dissolved and removed to obtain a secondary pattern resist 29 having a cylindrical secondary resist body 28 corresponding to the introduction hole portion 15 and the holding hole portion 16, as shown in FIG. 4(d). Since the center of the light-transmitting hole of the pattern film 27 coincides with the central axis Q1 of the primary resist body 24, the central axis Q2 of the cylindrical secondary resist body 28 is positioned coaxially with the central axis Q1 of the disk-shaped primary resist body 24.

(Electroforming process)
The above-mentioned mother mold 21 is placed in a prepared electroforming tank, and as shown in FIG. 5(a), the electroformed metal is electrodeposited in an area that goes over the upper edge of the primary resist body 24 but does not go over the upper edge of the secondary resist body 28, to form an electroformed layer 30, i.e., a layer that becomes the mask body 10. At this time, the edge of the growth tip of the electroformed metal that grows over the upper edge of the primary resist body 24 grows in a quarter-circular arc shape, so that the bell-mouth-shaped introduction hole portion 15 can be formed simply by electrodepositing the electrodeposited metal on the mother mold 21. As described above, it is possible to manufacture an array mask having an array through hole 12 with a bell-mouth-shaped introduction hole portion 15 without the need to perform a separate process for forming the introduction hole portion 15 into a bell-mouth shape, so that the number of work steps in the manufacturing process of the array mask can be shortened, and the manufacturing cost of the array mask can be reduced. In addition, since the central axis Q2 of the secondary resist body 28 is positioned coaxially with the central axis Q1 of the primary resist body 24, the introduction hole portion 15 can be formed with the same cross-sectional shape in the circumferential direction.

(Peeling process)
As shown in Fig. 5(b), the electroforming layer 30 and the primary and secondary pattern resists 25, 29 are peeled off from the matrix 21, and then the primary and secondary pattern resists 25, 29 are dissolved and removed to obtain the mask body 10 shown in Fig. 3. The frame 11 is adhered to the outer periphery of the obtained mask body 10 with an adhesive, and the two 10, 11 are inseparably joined to obtain the array mask 1.

(Second embodiment) Figures 6 and 7 show a second embodiment of the mask for arranging conductive pillars according to the present invention. In this embodiment, as shown in Figure 6, the central axis P1 of the holding hole portion 16 is offset relative to the central axis P2 of the escape hole portion 17, and the curvature of the cross-sectional shape of the introduction hole portion 15 is formed so as to gradually change from large to small from one side edge to the opposite other side edge. More specifically, the cross-sectional shape of the introduction hole portion 15 is formed similarly in the circumferential direction, and the curvature of the cross-sectional shape of the introduction hole portion 15 is the largest on the right side in Figure 6 and the smallest on the left side, and the curvature gradually changes from large to small in the middle part from the right side to the left side of the introduction hole portion 15. The cross-sectional shape of the introduction hole portion 15 is formed in a quarter-circular arc shape of a perfect circle. The height dimension H3 of the introduction hole portion 15 in this embodiment is the dimension at the position where the curvature is smallest. Since the rest is the same as in the first embodiment, the same members are given the same symbols and their description is omitted. The same applies to the following embodiments.

Figure 8 shows a method for manufacturing an array mask according to the second embodiment. The primary patterning process in the manufacturing method of this embodiment is similar to the method shown in Figures 4(a) and (b) described in the first embodiment.

(Secondary Patterning Process)
As shown in FIG. 8(a), a photoresist layer 26 is formed on the entire surface of the mother mold 21 including the portion where the primary pattern resist 25 is formed, and a pattern film 27 made of a glass mask having a circular light-transmitting hole corresponding to the holding hole portion 16 is attached to the upper surface of the photoresist layer 26. At this time, the entire pattern film 27 is attached in a state shifted to the right side in FIG. 8(a) so that the center of the light-transmitting hole and the central axis Q1 of the primary resist body 24 are in different positions. In this state, exposure is performed by irradiating ultraviolet light, and each process of development and drying is performed. The photoresist layer 26 here is formed in the same manner as the photoresist layer 22 described above. Next, the photoresist layer 26 in the unexposed portion is dissolved and removed to obtain a secondary pattern resist 29 having a cylindrical secondary resist body 28 corresponding to the introduction hole portion 15 and the holding hole portion 16 as shown in FIG. 8(b). Note that since the center of the light-transmitting hole of the pattern film 27 and the central axis Q1 of the primary resist body 24 are in different positions, the central axis Q2 of the secondary resist body 28 is biased with respect to the central axis Q1 of the primary resist body 24.

(Electroforming process)
The above-mentioned mother mold 21 is placed in a prepared electroforming tank, and as shown in Fig. 8(c), the electroformed metal is electrodeposited in an area that goes over the upper edge of the primary resist body 24 but does not go over the upper edge of the secondary resist body 28, to form an electroformed layer 30, i.e., a layer that becomes the mask body 10. At this time, the edge of the growth tip of the electroformed metal that grows over the upper edge of the primary resist body 24 grows in a quarter-circular arc shape, so that the bell-mouth-shaped introduction hole 15 can be formed simply by electrodepositing the electrodeposited metal on the mother mold 21. Furthermore, the longer the distance from the surface of the mother mold 21 to the secondary resist body 28, the smaller the curvature of the quarter-circular arc becomes, so that the curvature of the edge of the growth tip of the electroformed metal growing on the right side in Fig. 8(c) is small, and the curvature of the edge of the growth tip of the electroformed metal growing on the left side is large. As a result, the arrayed through holes 12 in which the curvature of the cross-sectional shape of the introduction hole 15 gradually changes from large to small in the circumferential direction can be easily formed simply by performing the electroforming process. Furthermore, since the central axis Q2 of the secondary resist body 28 is offset from the central axis Q1 of the primary resist body 24, the central axis P1 of the retaining hole portion 16 can be formed in an offset position relative to the central axis P2 of the escape hole portion 17.

(Peeling process)
As shown in Fig. 8(d), the electroforming layer 30 and the primary and secondary pattern resists 25, 29 are peeled off from the matrix 21, and then the primary and secondary pattern resists 25, 29 are dissolved and removed to obtain the mask body 10 shown in Fig. 6. The frame 11 is adhered to the outer periphery of the obtained mask body 10 with an adhesive, and the two 10, 11 are inseparably joined to obtain the array mask 1.

As described above, when the cross-sectional shape of the introduction hole portion 15 is formed so that it gradually changes from large to small from one side edge to the opposite other side edge in the circumferential direction, the introduction guide function of the conductive pillar 2 can be greatly exerted on the side with the small curvature, and the height dimension H4 of the holding hole portion 16 can be increased on the side with the large curvature, so that the positioning function of the conductive pillar 2 in the holding hole portion 16 can be greatly exerted. Therefore, it is possible to make it easier to partially drop the conductive pillar 2 in the circumferential direction of the introduction hole portion 15, and it is possible to make the arrangement through hole 12 capable of accurately positioning the dropped conductive pillar 2. In addition, by forming the arrangement through hole 12 so that the side with the small curvature is oriented in the same direction, when dropping the conductive pillar 2, the squeegee can be moved from the side with the small curvature to the side with the large curvature, so that the conductive pillar 2 can be dropped into the arrangement through hole 12 more quickly, and the installation work can be completed in a shorter time.

In this embodiment, the curvature is formed so as to gradually change from large to small from one side edge to the opposite other side edge, but the introduction hole portion 15 may have a large curvature portion and a small curvature portion formed smoothly and alternately in the circumferential direction. It is preferable to form the curvature between the large curvature portion and the small curvature portion so that the curvature gradually changes from large to small or from small to large. In this case, in the primary patterning process, a pattern film 23 made of a glass mask in which light-transmitting holes corresponding to the escape hole portion 17 are formed in a petal shape is used to form a primary pattern resist 25 having a primary resist body 24 corresponding to the escape hole portion 17. The subsequent process is the same as in the first embodiment. In this way, by forming the petal-shaped primary resist body 24, the timing at which the electrodeposited metal overcomes the upper edge of the primary resist body 24 and contacts the secondary resist body 28 during the electroforming process can be partially different. This makes it possible to increase the curvature of the edge of the growth tip of the electroformed metal that first contacted the secondary resist body 28, and to reduce the curvature of the edge of the growth tip of the other parts.

The array mask (metal mask) of this embodiment can also be used as a metal mask, such as an array mask for conductive balls, or a screen printing mask for forming a printed layer of conductive paste. Note that the same is true for the other embodiments.

(Third embodiment) FIG. 9 shows a third embodiment of the mask for arranging conductive pillars according to the present invention. In this embodiment, as shown in FIG. 9, a plurality of support protrusions 35 formed in a columnar shape on the underside of the mask body 10 are integrally provided so as to avoid the escape hole portion 17, which is different from the first embodiment. The support protrusions 35 may be formed of the same metal material as the mask body 10, or may be formed of a material made of another metal. They may also be formed of a non-magnetic material such as copper or resin. In this way, since the support protrusions 35 are provided on the underside of the mask body 10, contact between the workpiece 3 and the mask 1 can be avoided as much as possible, and damage to the mask 1 and the workpiece 3 caused by placing the mask 1 on the workpiece 3 can be further suppressed. In addition, the durability of the mask 1 can be further improved.

In the above embodiment, the support protrusions 35 are provided to avoid the escape hole portion 17, but they may be provided at equal intervals at positions corresponding to the dicing lines of the workpiece 3 shown by the dashed lines in FIG. 2, or may be provided only at positions corresponding to the intersections of the dicing lines. The support protrusions 35 are not limited to being columnar, but may be formed in a rib shape. When formed in a rib shape, a group of support protrusions 35 arranged in parallel may be formed, or the support protrusions 35 may be formed in a lattice shape.

As described above, according to the conductive pillar array mask of each of the above embodiments, the conductive pillar 2 can be introduced and guided by the introduction hole portion 15 formed in a bell-mouth shape, and the conductive pillar 2 can be smoothly dropped into the array through hole 12, so that the mounting work of the conductive pillar 2 on the workpiece 3 can be completed in a short time. In addition, the conductive pillar 2 dropped into the array through hole 12 can be positioned by the straight hole-shaped holding hole portion 16, and the conductive pillar 2 can be prevented from tilting or shifting within the array through hole 12, so that the conductive pillar 2 can be mounted accurately at a predetermined position on the workpiece 3.

In each of the above embodiments, the cross-sectional shape of the introduction hole portion 15 is formed in a quarter-circular arc shape, but it may be an elliptical quarter-circular arc shape or a partially protruding circular arc shape. The escape hole portion 17 is not limited to a straight hole shape, and can be formed in a truncated cone hole shape or a stepped hole shape. When forming a stepped hole shape, the primary resist body 24 can be formed in two stages in a stepped shape.

2 Conductive pillar (target object)
3 Workpiece 10 Mask body 12 Through hole (arranged through hole)
15 Introduction hole 16 Holding hole 17 Relief hole 21 Mother mold 24 Primary resist body 25 Primary pattern resist 28 Secondary resist body 29 Secondary pattern resist 30 Electroformed layer D1 Opening diameter D3 Opening diameter H1 Total height dimension H2 of introduction hole and holding hole Height dimension H3 of relief hole Height dimension H4 of introduction hole Height dimension Q1 of holding hole Central axis Q2 of primary resist body Central axis of secondary resist body

Claims (3)

A metal mask having a mask body (10) provided with through holes (12) corresponding to a predetermined pattern, and having columnar conductive pillars (2) mounted at predetermined positions on a workpiece (3),
the through hole (12) includes an introduction hole portion (15) that opens on the upper surface of the mask body (10) and guides the conductive pillar (2) into the through hole (12), and a holding hole portion (16) that is provided below the introduction hole portion (15) and positions the conductive pillar (2);
When the height dimension of the introduction hole portion (15) is H3 and the height dimension of the holding hole portion (16) is H4 , the height dimension (H4) of the holding hole portion (16) is set to be equal to or larger than the height dimension (H3) of the introduction hole portion (15),
A support protrusion (35) formed in a columnar or rib shape is provided on the lower surface of the mask body (10),
A metal mask characterized in that a total height dimension (H1) of the introduction hole portion (15) and the holding hole portion (16) is set to be larger than a height dimension of the support protrusion (35) . The metal mask according to claim 1, wherein the dimensional ratio of the height dimension (H3) of the introduction hole portion (15) to the height dimension (H4) of the retention hole portion (16) is set within the range of (H3):(H4) = 1:1 to 1:1.5. The retaining hole portion (16) is formed as a straight hole,
2. The metal mask of claim 1, wherein when the opening diameter of the retaining hole portion (16) is D1 and the opening diameter of the introduction hole portion (15) on the upper surface of the mask body (10) is D2 , the opening diameter (D1) of the retaining hole portion (16) is set to be larger than the diameter of the conductive pillar (2), and the opening diameter (D2) of the upper end of the introduction hole portion (15) is set to be larger than the opening diameter (D1) of the retaining hole portion (16) .

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