JP7595142B2 - Array Mask - Google Patents

Description

The present invention is used, for example, to create solder bumps for BGA (Ball Grid Array) systems.
This relates to a mask for arranging solder balls.

In general, solder bumps are formed through a process of applying solder paste or flux to electrodes, a process of mounting solder balls on the electrodes, and a process of heating and melting the mounted solder balls. In the above-mentioned process of mounting solder balls on electrodes, it is widely known to use an array mask having an opening pattern corresponding to the array pattern of the electrodes. For example, Patent Documents 1 and 2 disclose an array mask having a circular ball insertion hole. Patent Documents 3 and 4 disclose an array mask having a polygonal ball insertion hole such as a square opening or a triangular opening. Patent Documents 1 and 4 disclose providing a frame for supporting a mask body having ball insertion holes on the outer periphery of the mask body.

JP 2006-287215 A JP 2006-324618 A JP 2012-227466 A JP 2014-107282 A

In the arrangement masks of Patent Documents 1 and 2, in which the ball insertion holes are formed in a circular shape, the spherical outer surface of the solder ball and the arc-shaped opening edge of the insertion hole come into line contact, and the solder ball is easily damaged. In addition, since the outer surface of the solder ball and the opening edge of the insertion hole come into contact with each other in a large area, the contact resistance increases, and the solder ball cannot be smoothly dropped into the insertion hole, which is disadvantageous in that the mounting rate decreases. In contrast, in the arrangement masks of Patent Documents 3 and 4, in which the ball insertion holes are formed in a polygonal shape such as a square opening or a triangular opening, the opportunity for the opening edge and the solder ball to come into contact with each other can be reduced compared to a circular insertion hole, so that the solder ball can be effectively prevented from being damaged, and the solder ball can be smoothly dropped into the insertion hole to improve the mounting rate. However, in the arrangement masks of Patent Documents 3 and 4, when the mask body is attached to the frame body, the stress resulting from the tension is likely to concentrate on the minor-angle corners of the polygonal insertion holes, which may cause cracks in the corners and damage the arrangement mask.

The present invention has been made to solve the problems associated with conventional array masks as described above, and has an object to provide a solder ball array mask that is less likely to break even when tension is applied while ensuring an excellent solder ball mounting rate.

The present invention is directed to an array mask that has ball insertion holes 12 corresponding to a predetermined array pattern, and that mounts the solder balls 2 at predetermined positions on a workpiece 3 by dropping the solder balls 2 into the ball insertion holes 12. The opening edges of the ball insertion holes 12 are characterized in that they are formed into rounded regular polygons in plan view.

The rounded regular polygon has a partially arcuate rounded portion 17 located at the corner of the rounded regular polygon.
and straight line portions 16 that form sides of the rounded regular polygon and are tangentially connected to the rounded portions 17. The term "partial arc" used here is a concept that includes partial regular circular arcs and partial elliptical arcs.

It is preferable to define a virtual regular polygon 18 formed by extending the straight line portion 16, define a corner straight line portion 20 defined by connecting a vertex portion 19 of the virtual regular polygon 18 and an end portion of the straight line portion 16 facing the vertex portion 19, define a side dimension of the virtual regular polygon 18 as D and a length dimension of the corner straight line portion 20 as d1, and configure the virtual regular polygon 18 so as to satisfy the inequality (d1<D/2).

It is more preferable to define a virtual regular polygon 18 formed by extending the straight line portion 16, define a corner straight line portion 20 defined by connecting a vertex portion 19 of the virtual regular polygon 18 and an end portion of the straight line portion 16 facing the vertex portion 19, define a side dimension of the virtual regular polygon 18 as D and a length dimension of the corner straight line portion 20 as d1, and configure the virtual regular polygon 18 so as to satisfy the inequality (D/4≦d1≦D/3).

The opening edge of the ball insertion hole 12 is formed into a regular rectangle with rounded corners, and the regular rectangle with rounded corners is
The corner straight line portion 20 is defined by connecting a vertex 19 of the virtual square 18 and an end of the straight line portion 16 that faces the vertex 19 and defines a virtual square 18 formed by extending the straight line portion 16. The corner straight line portion 20 is defined by connecting a vertex 19 of the virtual square 18 and an end of the straight line portion 16 that faces the vertex 19.
is defined, a side dimension of the virtual regular rectangle 18 is defined as D, and a length dimension of the corner straight portion 20 is defined as d1, the movement direction of the squeegee 25 for moving on the array mask to drop the solder balls 2 into the ball insertion holes 12 coincides with the extension direction of the two straight portions 16, 16 which are a pair of opposing sides of the rounded regular rectangle of the ball insertion holes 12. The length dimension d1a (d1) of the corner straight portion 20 of the two rounded portions 17a (17) located upstream in the movement direction of the squeegee 25 and the length dimension d1b (d1) of the corner straight portion 20 of the two rounded portions 17b (17) located downstream in the movement direction of the squeegee 25 can be set to different dimensions.

The present invention also relates to an array mask that has ball insertion holes 12 corresponding to a predetermined array pattern, and that mounts the solder balls 2 at predetermined positions on the workpiece 3 by dropping the solder balls 2 into the ball insertion holes 12. The opening edge of the ball insertion holes 12 is characterized in that it is formed into an irregular regular polygon having straight line portions 41 that form the sides of the regular polygon, and partial arc portions 43 that are formed by bulging outward at each of vertices 42 that form the regular polygon.

Generally, the stress applied during the manufacturing process of the array mask and acting on the opening edge of the ball insertion hole 12 is concentrated at the portion where the opening edge shape of the ball insertion hole 12 changes abruptly (for example, at the corner). For this reason, when the ball insertion hole 12 is formed as a regular polygon with rounded corners, as in the present invention, the sudden change in the opening edge shape at the corners can be suppressed compared to the opening edge of a regular polygon ball insertion hole with the same number of corners, and the stress can be distributed and applied to the rounded corners. Therefore, according to the present invention, an array mask that is less likely to break even when tension is applied can be obtained compared to a mask with a polygonal ball insertion hole. Since the distortion of the array mask caused by the deformation of the ball insertion hole 12 due to stress concentration can be suppressed, there is also the advantage that the flatness of the array mask can be maintained. In addition, since the opportunity for the opening edge and the solder ball to come into contact can be reduced compared to a mask with a circular ball insertion hole, the solder ball 2 can be dropped more smoothly into the insertion hole 12, and the mounting rate of the solder ball 2 can be improved.

The rounded regular polygon has a partially arcuate rounded portion 17 located at the corner of the rounded regular polygon.
and a straight portion 16 that forms a side portion of the rounded regular polygon and is tangentially connected to the round portion 17.
7 and the straight portion 16 can be smoothly connected, so that the ball insertion hole 12
Therefore, damage and deformation of the mask for arranging the solder balls 2 due to the concentration of stress can be more effectively prevented.

When a virtual regular polygon 18 formed by extending the straight line portion 16 is defined, a corner straight line portion 20 defined by connecting a vertex 19 of the virtual regular polygon 18 and an end portion of the straight line portion 16 facing the vertex 19 is defined, and a side dimension of the virtual regular polygon 18 is defined as D and a length dimension of the corner straight line portion 20 is defined as d1, the inequality (d1<D/2) can be satisfied. In this manner, when the relationship between the side dimension D of the virtual regular polygon 18 and the length dimension d1 of the corner straight line portion 20 is configured to satisfy the inequality (d1<D/2), the curvature of the rounded portion 17 can be made as small as possible within a range in which the opening edge of the ball insertion hole 12 does not become circular, and therefore stress can be sufficiently dispersed in the corner portion.

Alternatively, the relationship between the side dimension D of the virtual regular polygon 18 and the length dimension d1 of the corner straight portion 20 can be configured to satisfy the inequality (D/4≦d1≦D/3). In this way, when the length dimension d1 is D/4 or more, the curvature of the rounded portion 17 can be reduced, and stress can be sufficiently dispersed at the corner portion. When the length dimension d1 is D/3 or less, the length dimension of the straight portion 16 can be sufficiently secured, and it is possible to prevent the solder balls 2 from being scratched and the mounting rate of the solder balls 2 from being deteriorated. On the other hand, when the length dimension d1 is less than D/4, the curvature of the rounded portion 17 is large, and therefore stress cannot be sufficiently dispersed at the corner portion. When the length dimension d1 exceeds D/3, the straight portion 16 is not sufficiently secured, and the solder balls 2 are easily scratched and the mounting rate of the solder balls 2 is deteriorated.

When the opening edge of the ball insertion hole 12 is formed into a regular rectangle with rounded corners, the length dimension d1a of the corner straight portion 20 of the two rounded portions 17a (17) located upstream in the moving direction of the squeegee 25 is
(d1) and two curved portions 17b (17) located downstream in the moving direction of the squeegee 25.
For example, the length dimension d1a of the rounded portion 17a can be set to a dimension different from the length dimension d1b (d1) of the corner straight portion 20 of the rounded portion 17b.
If the distance is set smaller than the distance 16, the straight line portion 16 of the side portion located on the upstream side in the moving direction of the squeegee 25 will be
Since the length dimension of the straight portion 16 on the upstream side of the moving direction of the squeegee 25 can be increased, the solder ball 2 tends to fall into the ball insertion hole 12 when its center of gravity is located above the ball insertion hole 12 in a plan view, so by increasing the length dimension of the straight portion 16 on the upstream side of the moving direction of the squeegee 25 as described above, the solder ball 2 can be easily guided into the ball insertion hole 12, and the mounting rate of the solder ball 2 can be improved.
This can prevent the squeegee 25 from getting caught on the edge portion located downstream in the moving direction, thereby enabling the squeegee 25 to pass smoothly over the ball insertion hole 12.

In another array mask according to the present invention, the opening edge of the ball insertion hole 12 into which the solder balls 2 are inserted is formed as an irregular regular polygon having straight line portions 41 constituting the sides of the regular polygon and partial arc portions 43 formed by bulging outward at each vertex portion 42 constituting the regular polygon, as shown in Fig. 9. This makes it possible to prevent the corner portion of the ball insertion hole 12 from forming an opening edge with a minor angle, which is prone to stress concentration. Therefore, according to the present invention, it is possible to obtain an array mask for solder balls 2 that is difficult to break even when tension is applied to the array mask, while preventing the solder balls 2 from being scratched by the polygonal ball insertion hole 12 and improving the mounting rate of the solder balls 2.

1 is a plan view of a main part of an array mask according to a first embodiment of the present invention; FIG. 2 is a perspective view showing an entire array mask. FIG. 2 is a vertical sectional front view of a main part of the array mask. 5A to 5D are explanatory diagrams showing a method for manufacturing an array mask. 5A to 5D are explanatory diagrams showing a method for manufacturing an array mask. FIG. 11 is a plan view of a main part of an array mask according to a second embodiment of the present invention. FIG. 11 is a plan view of a main part of an array mask according to a third embodiment of the present invention. 11A to 11C are plan views showing modified examples of ball insertion holes in an array mask according to the present invention. FIG. 11 is a plan view of a main part of an array mask according to a fourth embodiment of the present invention.

1 to 5 show a first embodiment of a solder ball array mask according to the present invention. In this embodiment, front, back, left, right, top and bottom refer to the crossed arrows shown in FIGS. 1, 2 and 3, and
Please follow the notations for front, back, left, right, and up and down near the crossed arrows. Note that the dimensions such as thickness and width in each figure of this embodiment are not shown in actuality, but are shown diagrammatically. The same applies to the figures of the following embodiments.

This array mask (hereinafter referred to as "mask") 1 is used in the process of mounting solder balls 2 in the production of solder bumps for the BGA system. In Figures 2 and 3, reference numeral 3 denotes a workpiece on which the solder balls 2 are to be mounted using the mask 1. This workpiece 3
is formed by mounting a plurality of semiconductor chips 5 on a base 4 of a glass epoxy substrate, wiring them with wire bonds, and then sealing them with a transfer mold, and electrodes 6 serving as input/output terminals are formed in a predetermined pattern on the upper surface of the work 3 so as to surround the semiconductor chips 5. After the solder bumps are formed, the work 3 is cut into individual pieces to be made into individual LSI chips.

As shown in FIG. 2, the mask 1 is made of nickel, a nickel alloy such as nickel-cobalt, copper,
It is composed of a mask body 10 formed by electroforming using other electrodeposited metals as a material, and a frame body 11 joined so as to surround this mask body 10. In the center of the surface of the mask body 10, a number of pattern areas 13 are formed, each having a number of independent ball insertion holes (hereinafter referred to as "insertion holes") 12 for inserting solder balls 2, corresponding to each semiconductor chip 5.

The insertion holes 12 correspond to an arrangement pattern that corresponds to the arrangement positions of the electrodes 6 of each semiconductor chip 5 in the work 3. The solder balls 2 have a diameter dimension of 100 μm or less, and accordingly, the front-to-back and left-to-right dimensions of each insertion hole 12 are slightly larger than the diameter dimension of the balls 2.

1, the opening edge of the insertion hole 12 is formed in a rounded regular square shape (rounded regular polygon shape) in a plan view. More specifically, the opening edge of the insertion hole 12 is formed in a rounded regular square shape in a plan view, having a total of four straight line parts 16 running in the front-rear and left-right directions, and quadrant arc-shaped (partial arc-shaped) round parts 17 formed at the four corner parts.
In the example shown in FIG. 1, the radius dimensions of the four rounded portions 17 are set to the same dimension.
The two adjacent straight line portions 16 are tangentially connected to the arc portion 17 formed in a quadrant arc shape. In other words, the adjacent straight line portions 16 are tangentially connected to the arc portion 17 formed in a quadrant arc shape, and the arc portion 17 and the straight line portion 16 are smoothly connected. The insertion hole 12 is desirably arranged in the mask body 10 so that the extension direction of the two straight line portions 16, which are the front and rear sides of the rounded regular rectangle, coincides with the movement direction (left-right direction) of the squeegee brush (squeegee) 25 described later.

The ratio of the radiused portion 17 to the side dimensions of the square shape, i.e., the ratio of the non-linear portion to each side of the square shape, is preferably less than 1/2, and more preferably 1/4 to 1/3 (1/
More preferably, the ratio is 1/4 or more and 1/3 or less.
indicates a virtual regular quadrangle (virtual regular polygon) formed by extending the straight line portion 16, and the side dimension of the virtual regular quadrangle 18 is D. A corner straight line portion 20 is defined by connecting a vertex portion 19 of the virtual regular quadrangle 18 with an end portion of the straight line portion 16 facing the vertex portion 19, and the length dimension of the corner straight line portion 20 is defined as d1. In this case, the length dimension d1 of the corner straight line portion 20 preferably satisfies the inequality (d1<D/2), and more preferably satisfies the inequality (D/4≦d1≦D/3). The length dimension d1 of the corner straight line portion 20 is the radius dimension of the rounded portion 17. In this embodiment, the length dimension d1 of the corner straight line portion 20 is set to D/4. It is preferable that the side dimension D of the virtual regular quadrangle 18 is set to 1.05 to 1.15 times the diameter dimension of the solder ball 2.

As shown in FIG. 2, a frame 11 for supporting the mask body 10 is joined to the mask body 10. Specifically, the frame 11 is directly attached to the mask body 10 with an adhesive or the like.
Alternatively, the frame 11 and the mask body 10 may be joined via a gauze such as Tetoron (registered trademark). The frame 11 also serves as a reinforcing member for the mask body 10.
The mask 1 is a horizontally long flat plate made of a material with a low coefficient of linear thermal expansion such as aluminum, stainless steel, 42 alloy, Invar material, Super Invar material, or SUS430, and a horizontally long rectangular opening corresponding to the mask body 10 is formed in the center of the plate surface. The frame 11 is a molded product that is thicker than the mask body 10 and is inseparably joined to the outer periphery of the mask body 10. The thickness of the frame 11 is, for example, about 0.05 to 3 mm. The overall thickness of the mask 1 can be designed according to the diameter of the solder ball 2 to be used, and it is particularly preferable that the thickness of the mask body 10 (including the thickness of the support protrusions 23 if they are provided) is approximately the same as the diameter of the solder ball 2.

On the lower surface side of the mask body 10, i.e., the surface side facing the workpiece 3, a support protrusion 23 is provided in a downward protruding manner to ensure a facing distance with the workpiece 3. The support protrusion 23 has an inverted truncated cone shape, and its lower end face always abuts against the surface of the workpiece 3 during the arrangement work of the solder balls 2, thereby ensuring a facing distance between the mask 1 and the workpiece 3. The support protrusion 23 can be provided in a lattice frame shape so as to surround the pattern region 13. The support protrusion 23 is formed integrally with the mask body 10, but it is also possible to integrally join a separately formed member to the mask body 10.

The process of arranging the solder balls 2 using the mask 1 is carried out as follows. First, the flux 24 is printed and applied onto the electrodes 6 of the workpiece 3 (see FIG. 3). Next, the ball insertion holes 1 are
The mask 1 is aligned on the workpiece 3 so that the electrode 6 and the frame 11 are aligned, and then the mask 1 is fixed. This alignment is actually performed by aligning the outer periphery of the frame 11 and the workpiece 3. A magnet can be placed below the workpiece 3, and after the alignment is completed, the mask 1 can be fixed to the workpiece 3 in an inseparable manner by the magnetic attraction force of the magnet. In this fixed state, the lower end faces of the support protrusions 23 abut against the surface of the workpiece 3, so that the mask 1 is held in a separated position with a facing distance from the workpiece 3 secured as shown in FIG. 3.

Next, a large number of solder balls 2 are supplied to the opening of the frame 11, i.e., onto the mask body 10, and the solder balls 2 are dispersed on the mask body 10 using a squeegee brush 25 with a brush-shaped tip, and the solder balls 2 are inserted one by one into the insertion holes 12. In this embodiment, the left direction is the upstream side and the right direction is the downstream side, and the squeegee brush 25 is moved from left to right to insert the solder balls 2 into the insertion holes 12, and the solder balls 2 are mounted on the electrodes 6. The solder balls 2 inserted into the insertion holes 12 are adhesively held in a temporary state by the flux 24. Finally, the remaining solder balls 2 are removed from the upper surface of the mask 1, and then the mask 1 is removed, and the solder balls 2 are heated and melted, thereby forming solder bumps on the electrodes 6 of the workpiece 3.

4 and 5 show a method for manufacturing the array mask 1 according to this embodiment. First, FIG.
As shown in FIG. 1, a photoresist layer 28 is formed on the surface of a conductive matrix 27 made of, for example, stainless steel or brass. This photoresist layer 28 can be formed by laminating one or several sheets of negative type photosensitive dry photoresist to a predetermined height and then subjecting them to thermocompression bonding. Next, inverted truncated cone-shaped support protrusions 23 are formed on the photoresist layer 28.
After that, a pattern film 29 (glass mask) having light transmitting holes 29a corresponding to the patterns is attached to the substrate 20, and then the substrate 20 is exposed to ultraviolet light from an ultraviolet lamp 30, and then the substrate 20 is developed and dried.
By dissolving and removing the unexposed portions, a primary pattern resist 31 having resist bodies 31a corresponding to the supporting projections 23 was formed on the matrix 27, as shown in FIG. 4(b).

Next, the mother mold 27 is placed in an electroforming tank prepared under predetermined conditions, and as shown in Fig. 4(c), within the range of the height of the resist body 31a, an electrodeposited metal such as nickel is electroformed on the surface of the mother mold 27 that is not covered by the resist body 31a, thereby forming a primary electroforming layer 32. Here, the primary electroforming layer 32 is formed over substantially the entire surface of the mother mold 27. Next, as shown in Fig. 4(d), the primary pattern resist 31 is removed. In order to improve the workability of the subsequent peeling step, it is desirable to subject the surface of the primary electroforming layer 32 to a polishing treatment or a peeling treatment after removing the primary pattern resist 31.

5A, a photoresist layer 35 is formed on the entire surface of the primary electroforming layer 32 and the matrix 27, and then the insertion holes 12 are formed on the surface of the photoresist layer 35.
After that, the pattern film 36 (glass mask) having the light transmitting holes 36a corresponding to the patterns is attached to the substrate 30, the substrate 30 is exposed to ultraviolet light by the ultraviolet lamp 30, and then the substrate 30 is developed and dried.
The unexposed portions were dissolved and removed to form a secondary pattern resist 37 having resist bodies 37a corresponding to the insertion holes 12 as shown in FIG. 5(b) on the surface of the primary electroforming layer 32.

Next, the mother mold 27 was placed in an electroforming tank prepared under specified conditions, and within the range of the height of the resist body 37a, an electrodeposited metal such as nickel was electroformed on the mother mold 27 and the surface of the primary electroforming layer 32 not covered by the resist body 37a to form a secondary electroforming layer 38. Next, the secondary pattern resist 37 was dissolved and removed, and the mother mold 27 and the primary electroforming layer 32 were peeled (removed) from the secondary electroforming layer 38 to obtain a mask body 10 as shown in Figures 5(d) and 3. Finally, a frame 11 was joined to the mask body 10 to obtain a mask 1 as shown in Figure 2.

The secondary electroformed layer 38, i.e., the mask body 10, can be supported by the frame 11 in a state where tension is applied thereto so that a stress acts on the mask body 10 in a direction in which the mask body 10 contracts inward.
In other words, the mask body 10 is supported by the frame 11 while tension is applied to the mask body 10. In this embodiment, the secondary electroformed layer 38 is supported by the frame 11 before being peeled off from the matrix 27.
This can be achieved by bonding the mask body 10 (mask body 10) and the frame body 11. This allows the expansion of the mask body 10 due to changes in the ambient temperature to be absorbed by tension in the contraction direction, preventing the mask body 10 from shifting in position relative to the workpiece 3. In addition, since uniform tension can be applied to the entire mask body 10, the solder balls 2 can be mounted on the workpiece 3 with good positional accuracy.

As described above, in the array mask 1 according to the present embodiment, the opening edge of the insertion hole 12 into which the solder balls 2 are inserted is formed into a rounded regular quadrangle (rounded regular polygon) in a plan view. Therefore, even when tension is applied to the mask body 10 during bonding to the frame 11, the mask body 1
0 can be effectively prevented from being damaged. That is, generally, the stress acting on the opening edge of the insertion hole 12 due to the tension of the mask body 10 tends to concentrate at the portion where the opening edge shape of the insertion hole 12 changes abruptly. For example, when the insertion hole is a regular square, the stress concentrates at the right-angled corners, and the insertion hole is easily damaged from the corners. On the other hand, when the insertion hole 12 is formed in a rounded regular square with rounded corners as in this embodiment, the sudden change in the opening edge shape at the corners can be suppressed compared to the opening edge of a conventional square-shaped insertion hole, and the stress can be distributed and applied to the rounded corners. Therefore, according to this embodiment, it is possible to obtain an array mask 1 that is less likely to be damaged even when tension is applied, compared to a mask having a square-shaped ball insertion hole. There is also an advantage that the distortion of the mask body 10 (mask 1) caused by the deformation of the ball insertion hole 12 due to stress concentration can be suppressed, and the flatness of the array mask 1 can be maintained. Furthermore, since the chance of the opening edge coming into contact with the solder balls can be reduced compared to a mask having circular ball insertion holes, the solder balls 2 can be dropped more smoothly into the insertion holes 12, and the mounting rate of the solder balls 2 using the array mask 1 can be improved.

Furthermore, in this embodiment, the opening edge of the ball insertion hole 12 is formed by the quadrant arc-shaped (partial arc-shaped) rounded portions 17 located at the corners of the rounded regular rectangle, and the straight portions 16 that form the sides of the rounded regular rectangle and are tangentially connected to the rounded portions 17, so that the opening edge of the ball insertion hole 12 can be configured so that the rounded portions 17 and the straight portions 16 are smoothly connected. This makes it possible to eliminate the formation of minor angled bends that are prone to stress concentration at the opening edge of the ball insertion hole 12, and therefore makes it possible to more effectively prevent damage and deformation of the mask for arranging the solder balls 2 due to stress concentration.

If the relationship between the side dimension D of the virtual regular quadrangle (virtual regular polygon) 18 and the length dimension d1 of the corner straight portion 20 is configured to satisfy the inequality (d1<D/2), the curvature of the rounded portion 17 can be made as small as possible without causing the opening edge of the ball insertion hole 12 to become circular, thereby allowing sufficient stress dispersion at the corner portion. In each of the above embodiments, the relationship between the side dimension D of the virtual regular quadrangle 18 and the length dimension d1 of the corner straight portion 20 is configured to satisfy the inequality (D/4≦d1≦D/3). This is because if the length dimension d1 is less than D/4, the curvature of the rounded portion 17 is large, making it difficult to sufficiently distribute stress at the corner portion. Also, if the length dimension d1 exceeds D/3, the straight portion 16 is not sufficiently secured,
This makes the solder balls 2 more susceptible to damage, and also leads to a decrease in the mounting rate of the solder balls 2.

6 shows a solder ball array mask according to a second embodiment of the present invention. In this embodiment, the length dimension d1a (d1) (radius of the rounded portion 17a) of the corner straight portion 20 of the two rounded portions 17a (17) located on the upstream side (left side) of the moving direction of the squeegee brush 25 is set to 1/2 the length dimension d1a (d1) (radius of the rounded portion 17a) of the two rounded portions 17a (17) located on the downstream side (right side) of the moving direction of the squeegee brush 25.
Length dimension d1b (d1) of the straight corner portion 20 of 7b (17) (radius of the rounded portion 17b)
The difference from the first embodiment is that the length d1a of the rounded portion 17a is set smaller than D
The length dimension d1b of the rounded portion 17b is set to D/4, and the length dimension d1b of the rounded portion 17b is set to D/3. Since the rest is the same as in the first embodiment, the same members are given the same reference numerals and the description thereof is omitted. The same applies to the following embodiments.

According to the insertion hole 12 as described above, the length dimension of the straight line portion 16 of the left side located on the upstream side in the moving direction of the squeegee brush 25 can be increased. According to this, when the center of gravity of the solder ball 2 is located on the ball insertion hole 12 in a plan view, the solder ball 2 tries to fall into the ball insertion hole 12, so by increasing the length dimension of the straight line portion 16 on the upstream side (left side) in the moving direction of the squeegee brush 25, the solder ball 2 can be easily guided into the ball insertion hole 12, and the mounting rate of the solder ball 2 can be improved. In addition, since the length dimension d1b of the two rounded portions 17b located on the downstream side in the moving direction of the squeegee brush 25 is large, the squeegee brush 25 is prevented from getting caught on the right side located on the downstream side in the moving direction, and the squeegee brush 25 can be allowed to pass smoothly over the ball insertion hole 12.

7 shows a third embodiment of a mask for arranging solder balls according to the present invention. In this embodiment, contrary to the second embodiment, the length dimension d1a (d2a) of the corner straight portion 20 of the two rounded portions 17a (17) located on the upstream side (left side) in the moving direction of the squeegee brush 25 is 1.0 mm.
1) (the radius of the rounded portion 17a) is set to the length dimension d1b (d1) (
The length dimension d1a of the rounded portion 17a is set to be larger than the radius of the rounded portion 17b.
The length dimension d1b of the rounded portion 17b is set to D/4.
2, the solder ball 2 can be dropped quickly into the insertion hole 12. More specifically, the outer surface of the solder ball 2 as it falls into the insertion hole 12 comes into contact with the inner surface of the insertion hole 12 downstream in the movement direction of the squeegee brush 25. Therefore, by increasing the length dimension of the straight portion 16 downstream in the movement direction of the squeegee brush 25, the contact area between the outer surface of the solder ball 2 as it falls and the inner surface of the insertion hole 12 can be reduced, and the falling action of the solder ball 2 can be prevented from being braked by friction between the two as it falls, allowing the solder ball 2 to be dropped quickly into the ball insertion hole 12. As a result, the solder ball 2 as it falls can be prevented from coming into contact with the inner surface of the insertion hole 12 downstream in the movement direction of the squeegee brush 25.
This can prevent the ball from being scraped out of the ball insertion hole 12 by the squeegee brush 25.

In the above embodiments, the connection between the straight portion 16 and the rounded portion 17 is configured to be tangential, but a slightly less-angled corner may be formed at the connection between the two. In this case, it is desirable to make the angle of the corner close to 180 degrees in order to avoid stress concentration.
Although each of the rounded portions 17 is configured as a quadrant arc, the rounded portions 17 may be configured as a quarter elliptical arc. Even in this case, it is preferable that adjacent straight portions 16 are configured to be tangent to the rounded portion 17, so that the rounded portion 17 and the straight portion 16 are smoothly connected. Even in this case, the length d1 of the corner straight portion 20 is within the range of (D/4≦d1≦D
/3) inequality.
One side (front side) and the other side (rear side) in the direction perpendicular to the moving direction of the squeegee brush 25
In the above, the length dimension d1 of the corner straight portion 20 can be changed. Also, the length dimension d1 of each corner portion of the insertion hole 12 may be made different.

8 shows modified examples of the insertion hole 12. In Fig. 8(a), the opening edge of the insertion hole 12 is a rounded regular triangle (rounded regular polygon) in plan view, in Fig. 8(b), the opening edge of the insertion hole 12 is a rounded regular pentagon (rounded regular polygon) in plan view, and in Fig. 8(c), the opening edge of the insertion hole 12 is a rounded regular hexagon (rounded regular polygon) in plan view. In these modified examples, the straight line portion 16 adjacent to the rounded portion 17 formed in a partial arc shape is also
The rounded corners of the rounded corners of the rounded corners of the straight portion 16 are not limited to the rounded corners of the rounded corners of the rounded corners of the straight portion 16.

9 shows a solder ball array mask according to a fourth embodiment of the present invention. In this embodiment, the opening edge of the insertion hole 12 is a straight line portion 4 constituting the sides of a regular quadrangle (regular polygon).
The insertion hole 12 is formed into an irregular regular quadrangle (irregular regular polygon) having a square 41 and a partial arc portion 43 formed by bulging outward at each vertex 42 constituting the regular quadrangle. The radius R of the partial arc portion 43 is set to 1/8 of the length L of the side of the regular quadrangle forming the opening edge of the insertion hole 12, and the connection portion between the straight portion 41 and the partial arc portion 43 is rounded with a radius smaller than the radius R of the partial arc portion 43. The insertion hole 12 is arranged in a staggered manner with two straight portions 41, 41, which are the front and rear sides of the regular quadrangle, extending in the same direction as the moving direction (left-right direction) of the squeegee brush 25, and two straight portions 41, 41 facing each other, extending in the direction inclined at 45 degrees to the moving direction (left-right direction) of the squeegee brush 25. The regular polygon forming the opening edge of the insertion hole 12 is not limited to a regular quadrangle, and may be, for example, an equilateral triangle, a regular pentagon, or the like. The radius R of the partial arc portion 43 is (L/8<R≦L/2).
It is preferable that the inequality is satisfied.

According to the insertion hole 12 as described above, it is possible to prevent the corners of the ball insertion hole 12 from forming a minor angled opening edge where stress is likely to concentrate. Therefore, according to the present invention, compared to the opening edge of a polygonal ball insertion hole with the same number of corners, it is possible to suppress abrupt changes in the opening edge shape at the corners, so that stress can be distributed and applied to the rounded corners, and therefore, compared to a mask having a polygonal ball insertion hole, it is possible to obtain an array mask that is less likely to break even when tension is applied. Compared to a mask having a circular ball insertion hole, it is possible to reduce the opportunity for the opening edge and the solder balls to come into contact with each other, so it is possible to make the solder balls 2 fall more smoothly into the insertion hole 12, and it is also possible to improve the mounting rate of the solder balls 2. In addition, the partial arc portion 43 serves as a guide portion for the solder balls 2, and the solder balls 2 that have reached the partial arc portion 43 can be guided to the insertion hole 12. At this time, if an inclined surface that slopes downward from the partial arc portion 43 to the straight portion 41 is provided, the guide function of the partial arc portion 43 to the insertion hole 12 can be more effectively exerted. At least the region surrounded by the partial arc portion 43 may be formed to have a bottom (not penetrating).

(Reference Example) In each of the above embodiments, the insertion hole 12 has a regular polygon as the reference shape of the opening edge, but the reference shape of the opening edge can be a rectangle. It can also be a convex polygon, a concave polygon, a star-shaped polygon, etc. In these cases, the opening edge of the insertion hole 12 is set to a size that allows at least one solder ball 2 to be dropped into it.

1 Array mask 2 Solder ball 3 Work 12 Ball insertion hole 16 Straight portion 17 Rounded portion 17a Rounded portion 17b located upstream in the moving direction of the squeegee Rounded portion 18 located downstream in the moving direction of the squeegee Virtual regular polygon (virtual regular quadrilateral)
19: apex portion 20: corner straight portion 25: squeegee (squeegee brush)
41 Straight portion 42 Vertex portion 43 Partial arc portion D Side dimension of virtual regular polygon d1 Length dimension of corner straight portion d1a Length dimension of corner straight portion of round portion 17a d1b Length dimension of corner straight portion of round portion 17b

Claims (5)

An array mask having ball insertion holes (12) corresponding to a predetermined array pattern, and for mounting solder balls (2) at predetermined positions on a workpiece (3) by inserting solder balls (2) into the ball insertion holes (12),
The opening edge of the ball insertion hole (12) is formed into an irregular regular polygon having straight line portions (41) constituting the sides of the regular polygon and partial arc portions (43) formed by bulging outward at each vertex portion (42) constituting the regular polygon,
When the length dimension of a side of a regular polygon forming an opening edge of the ball insertion hole (12) is defined as (L), a radius dimension (R) of the partial circular arc portion (43) is configured to satisfy the inequality (L/8<R) ;
An array mask characterized in that a sloped surface is provided which slopes downward from a partial arc portion (43) to a straight portion (41) . The array mask according to claim 1, characterized in that the radial dimension (R) of the partial arc portion (43) is configured to satisfy the inequality (L/8<R≦L/2). 3. The array mask according to claim 1, wherein a connecting portion between the straight portion (41) and the partial arc portion (43) is rounded with a radius smaller than a radius (R) of the partial arc portion (43). 4. The array mask according to claim 1 , wherein the extending direction of the straight line portion (41) in the ball insertion hole (12) is different from the extending direction of the straight line portion (41) in the adjacent ball insertion hole (12). The opening edge of the ball insertion hole (12) is formed into an irregular regular quadrangle in a plan view,
4. An array mask as described in any one of claims 1 to 3, characterized in that the ball insertion hole (12) has two opposing straight line portions (41, 41) of an irregular regular quadrangle, the extension direction of which coincides with the movement direction of the squeegee brush (25) and the extension direction of which is inclined at 45 degrees to the movement direction of the squeegee brush ( 25) .