JP7392079B2 - array mask - Google Patents

Description

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

Generally, solder bumps are formed through a process of applying solder paste or flux to an electrode, mounting a solder ball on the electrode, and heating and melting the mounted solder ball. In the process of mounting solder balls on the electrodes described above, it is widely known that an array mask having an opening pattern corresponding to the electrode array pattern is used. An array mask with holes is disclosed. Patent Documents 3 and 4 disclose array masks having polygonal ball insertion holes such as rectangular openings and triangular openings. Patent Documents 1 and 4 disclose that a frame body for supporting the mask body is provided on the outer peripheral edge of the mask body having a ball insertion hole.

JP2006-287215A Japanese Patent Application Publication No. 2006-324618 JP2012-227466A Japanese Patent Application Publication No. 2014-107282

In a configuration in which the ball insertion holes are formed in a circular shape, as in the arrangement masks of Patent Documents 1 and 2, 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 The ball is easily damaged. In addition, since there is more contact between the outer surface of the solder ball and the opening edge of the insertion hole, the contact resistance increases and the solder ball cannot fall smoothly into the insertion hole, resulting in a lower loading rate. There is also. On the other hand, when the ball insertion hole has a polygonal shape such as a rectangular opening or a triangular opening, as in the array masks of Patent Documents 3 and 4, the opening edge and the solder ball Since the chances of contact between the solder balls and the solder balls can be reduced, it is possible to effectively prevent the solder balls from being damaged, and the solder balls can fall more smoothly into the insertion holes, improving the loading rate. can. However, in the array masks of Patent Documents 3 and 4, when the mask main body is attached to the frame, stress resulting from the tension tends to concentrate at the inferior angle corner of the polygonal insertion hole. , there was a risk that cracks would occur at the corners and the array mask would be damaged.

The present invention has been made in order to solve the problems of the conventional arraying mask as described above, and it has been made to create solder balls that are difficult to break even when tension is applied, while ensuring an excellent solder ball mounting rate. The purpose is to provide a mask for arrays.

The present invention has a ball insertion hole 12 corresponding to a predetermined arrangement pattern, and by transferring the solder balls 2 into the ball insertion hole 12, an arrangement mask is created in which the solder balls 2 are mounted at a predetermined position on a workpiece 3. set to target. A feature is that the opening edge of the ball insertion hole 12 is formed into a regular polygon with rounded corners in plan view.

A regular polygon with rounded corners has a rounded part 17 in a partial arc shape located at a corner of the regular polygon with rounded corners.
and a straight line part 16 that forms the side part of the rounded regular polygon and is tangentially connected to the rounded part 17. The "partial arc" here is a concept that includes a partial regular circular arc and a partial elliptical arc.

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

A virtual regular polygon 18 formed by extending the straight line portion 16 is defined, and is defined by connecting the vertex 19 of the virtual regular polygon 18 and the end of the straight line portion 16 facing the vertex 19. When the corner straight section 20 is defined, the side dimension of the virtual regular polygon 18 is defined as D, and the length dimension of the corner straight section 20 is defined as d1, the inequality (D/4≦d1≦D/3) is expressed as More preferably, the configuration satisfies the above requirements.

The opening edge of the ball insertion hole 12 is formed into a regular square with rounded corners, and the square with rounded corners is
It is composed of a rounded part 17 located at a corner of the rounded regular quadrangle, and a straight part 16 that forms the side part of the rounded regular square and connects to the rounded part 17, and the straight part 16 is extended. A corner straight section 20 is defined by defining a virtual regular quadrilateral 18 formed by
When the side dimension of the virtual square 18 is defined as D, and the length dimension of the corner straight section 20 is defined as d1, the solder ball 2 is moved onto the array mask and inserted into the ball insertion hole 12. The moving direction of the squeegee 25 for dropping the ball is configured to coincide with the extending direction of the two straight portions 16, which are a pair of opposing sides of the square with rounded corners of the ball insertion hole 12. The length dimension d1a (d1) of the corner straight portion 20 of the two rounded portions 17a (17) located on the upstream side in the moving direction of the squeegee 25, and the two rounded portions 17b located on the downstream side in the moving direction of the squeegee 25. The length dimension d1b (d1) of the corner straight portion 20 in (17) can be set to a different dimension.

Furthermore, the present invention provides an arrangement for mounting the solder balls 2 at predetermined positions on the workpiece 3 by providing ball insertion holes 12 corresponding to a predetermined arrangement pattern and by transferring the solder balls 2 into the ball insertion holes 12. Targeting masks. The opening edge of the ball insertion hole 12 has a straight portion 41 forming a side of a regular polygon, and a partial arc portion 43 bulging outward at each vertex portion 42 forming the regular polygon. It is characterized by being formed into an irregular regular polygon.

In general, the stress applied during the process of manufacturing the array mask and acting on the opening edge of the ball insertion hole 12 is concentrated at locations where the opening edge shape of the ball insertion hole 12 changes rapidly (for example, at the corners). For this reason, when the ball insertion hole 12 is formed into a rounded regular polygon with rounded corners as in the present invention, compared to the opening edge of a regular polygonal ball insertion hole with the same number of angles, , it is possible to suppress a sudden change in the shape of the opening edge at the corner portion, and to disperse and apply stress to the rounded corner portion. Therefore, according to the present invention, it is possible to obtain an array mask that is less likely to be damaged even when tension is applied, compared to a mask having polygonal ball insertion holes. Since distortion of the arraying mask caused by deformation of the ball insertion holes 12 due to stress concentration can be suppressed, there is also an advantage that the flatness of the arraying mask can be maintained. Furthermore, compared to a mask having a circular ball insertion hole, the chances of contact between the opening edge and the solder ball can be reduced, so it is possible to drop the solder ball 2 into the insertion hole 12 more smoothly. , it is possible to improve the mounting rate of solder balls 2.

A regular polygon with rounded corners has a rounded part 17 in a partial arc shape located at a corner of the regular polygon with rounded corners.
and a straight line part 16 that forms the side part of the rounded regular polygon and is tangentially connected to the rounded part 17. According to such a ball insertion hole 12, the opening edge is formed into a rounded portion 1.
7 and the straight portion 16 can be configured to connect smoothly, so that the ball insertion hole 12
It is possible to eliminate the formation of inferior angle bent portions where stress tends to concentrate at the edges of the openings. Therefore, damage and deformation of the solder ball 2 array mask due to stress concentration can be more effectively prevented.

A virtual regular polygon 18 formed by extending the straight line portion 16 is defined, and is defined by connecting the vertex 19 of the virtual regular polygon 18 and the end of the straight line portion 16 facing the vertex 19. When the corner straight section 20 is defined, the side dimension of the virtual regular polygon 18 is defined as D, and the length dimension of the corner straight section 20 is defined as d1, it is configured to satisfy the inequality (d1<D/2). be able to. In this way, if the relationship between the side dimension D of the virtual regular polygon 18 and the length dimension d1 of the corner straight section 20 is configured to satisfy the inequality (d1<D/2), the ball insertion hole 12 Since the curvature of the rounded portion 17 can be made as small as possible within a range where the opening edge does not become circular, stress can be sufficiently dispersed at 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. Furthermore, if the length dimension d1 is D/3 or less, a sufficient length dimension of the straight portion 16 can be ensured to prevent scratches on the solder balls 2 and deterioration of the mounting rate of the solder balls 2. It can be prevented. On the other hand, if the length dimension d1 is less than D/4, the curvature of the rounded part 17 is large, so stress cannot be sufficiently dispersed at the corner part, and the length dimension d1 is less than D/3. If it exceeds this, the straight portion 16 will not be sufficiently secured, the solder balls 2 will be easily damaged, and the mounting ratio of the solder balls 2 will deteriorate.

When the opening edge of the ball insertion hole 12 is formed into a square with rounded corners, the length dimension d1a of the corner straight part 20 of the two rounded parts 17a (17) located on the upstream side in the moving direction of the squeegee 25
(d1) and two rounded portions 17b (17) located on the downstream side in the moving direction of the squeegee 25.
The length dimension d1b (d1) of the corner straight portion 20 can be set to a different dimension. For example, the length d1a of the radiused portion 17a is the length d1b of the latter radiused portion 17b.
When set smaller than , the straight portion 16 of the side located on the upstream side in the moving direction of the squeegee 25
Since the length of the solder ball 2 can be increased, when the center of gravity of the solder ball 2 is located above the ball insertion hole 12 in a plan view, the solder ball 2 tends to fall into the ball insertion hole 12. By increasing the length of the straight portion 16 on the upstream side in the moving direction, the solder balls 2 can be easily guided into the ball insertion holes 12, and the mounting rate of the solder balls 2 can be improved. In addition, since the length dimension d1b of the rounded portion 17b is large, the squeegee 25
This allows the squeegee 25 to smoothly pass over the ball insertion hole 12 by suppressing the ball from getting caught on the side located on the downstream side in the direction of movement.

In another arrangement mask according to the present invention, the opening edge of the ball insertion hole 12 into which the solder balls 2 are inserted has a straight line portion 41 forming the side of a regular polygon as shown in FIG. It is formed into an irregular regular polygon having partial arcuate portions 43 bulging outward at each of its apex portions 42 . According to this, it is possible to eliminate the formation of inferior angle-shaped opening edges where stress tends to concentrate at the corner portions of the ball insertion hole 12. Therefore, according to the present invention, the polygonal ball insertion hole 12 prevents the solder balls 2 from being damaged and improves the mounting rate of the solder balls 2, while also preventing damage when tension is applied to the array mask. It is possible to obtain a mask for arranging solder balls 2 that is difficult to arrange.

FIG. 2 is a plan view of main parts of the array mask according to Example 1 of the present invention. It is a perspective view showing the whole mask for arrangement. FIG. 3 is a longitudinal sectional front view of the main parts of the array mask. (a) to (d) are explanatory diagrams showing a method of manufacturing an array mask. (a) to (d) are explanatory diagrams showing a method of manufacturing an array mask. FIG. 7 is a plan view of a main part of an array mask according to Example 2 of the present invention. FIG. 7 is a plan view of a main part of an array mask according to Example 3 of the present invention. (a) to (c) are plan views showing modified examples of ball insertion holes in the array mask according to the present invention. FIG. 7 is a plan view of a main part of an array mask according to Example 4 of the present invention.

(Example 1) FIGS. 1 to 5 show Example 1 of a mask for arranging solder balls according to the present invention. In this example, front and rear, left and right, and top and bottom refer to the crossed arrows shown in FIGS. 1, 2, and 3,
Follow the front/back, left/right, and up/down notations near the crossing arrow. Note that the dimensions such as thickness and width in the figures of this embodiment do not represent the actual situation, but are shown schematically. The same applies to the figures of the following embodiments.

This array mask (hereinafter referred to as "mask") 1 is used in the step of mounting solder balls 2 in the production of BGA solder bumps. In FIGS. 2 and 3, reference numeral 3 indicates a workpiece to which solder balls 2 are mounted using the mask 1. In FIGS. This work 3
For example, a plurality of semiconductor chips 5 are mounted on a base 4 of a glass epoxy substrate, wired with wire bonds, and then sealed by transfer molding. Electrodes 6, which are input/output terminals, are formed in a predetermined pattern. Note that the workpiece 3 is cut into individual pieces after the solder bumps are created to form individual LSI chips.

As shown in FIG. 2, the mask 1 is made of a nickel alloy such as nickel or nickel cobalt, copper,
It consists of a mask body 10 formed by electroforming using another electrodeposited metal as a material, and a frame 11 joined to surround this mask body 10. At the center of the mask body 10 is a pattern area 13 having a large number of independent ball insertion holes (hereinafter referred to as "insertion holes") 12 for inserting solder balls 2, corresponding to each semiconductor chip 5. Many are formed.

The insertion holes 12 correspond to an arrangement pattern corresponding to the arrangement position of the electrodes 6 of each semiconductor chip 5 in the workpiece 3 . The solder ball 2 has a diameter of 100 μm or less, and accordingly, the front-back and left-right dimensions of each insertion hole 12 are slightly larger than the diameter of the ball 2.

As shown in FIG. 1, the opening edge of the insertion hole 12 is formed into a regular square shape with rounded corners (a regular polygonal shape with rounded corners) when viewed from above. More specifically, the opening edge of the insertion hole 12 has a total of four straight portions 16 running in the front-back and left-right directions, and quarter-arc shaped (partial arc-shaped) rounded portions 17 formed at the four corners. It is formed into a square shape with rounded corners when viewed from above. Mask 1 according to the present example
Here, the radial dimensions of the four rounded portions 17 are set to be the same. In addition, each round portion 17
On the other hand, two adjacent straight portions 16 are tangentially connected. That is, with respect to the rounded part 17 formed in a quarter-arc shape, the adjacent straight parts 16 are configured to be tangentially connected, and the rounded part 17 and the straight part 16 are smoothly connected. . The insertion hole 12 is formed in the mask body 10 so that the extending direction of the two straight parts 16, which are the front and rear sides of the square with rounded corners, coincides with the moving direction (left and right direction) of the squeegee brush (squeegee) 25, which will be described later. It is desirable that the

The proportion of the rounded portion 17 in the side dimensions of the regular square shape, that is, the proportion of the non-linear portions on each side of the regular square shape, is preferably less than 1/2, and 1/4 to 1/3 (1/3).
4 or more and 1/3 or less). More specifically, reference numeral 18 in FIG.
indicates a virtual regular quadrilateral (virtual regular polygon) formed by extending the straight line portion 16, and the side dimension of the virtual regular quadrilateral 18 is assumed to be D. A corner straight part 20 is defined by connecting the vertex 19 of this virtual square 18 and the end of the straight part 16 facing the vertex 19, and the length dimension of the corner straight part 20 is set as d1. It is stipulated that At this time, the length d1 of the corner straight portion 20 preferably satisfies the inequality (d1<D/2), and more preferably satisfies the inequality (D/4≦d1≦D/3). It is optimal that it satisfies the following. The length dimension d1 of this corner straight portion 20 becomes the radius dimension of the rounded portion 17. In this embodiment, the length d1 of the corner straight portion 20 is set to D/4. Note that the side dimension D of the virtual square 18 is preferably set to 1.05 to 1.15 times the diameter dimension of the solder ball 2.

As shown in FIG. 2, a frame 11 that supports 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, there is a configuration in which the frame body 11 and the mask body 10 are joined via a gauze such as Tetron (registered trademark). The frame 11 also serves as a reinforcing member for the mask body 10. This frame 1
1 is a horizontally elongated flat plate made of a material with a low coefficient of linear thermal expansion such as 42 alloy, Invar material, Super Invar material, SUS430, etc., in addition to aluminum and stainless steel. A rectangular opening that is horizontally elongated is formed. The frame 11 is a molded product that is thicker than the mask body 10, and is inseparably joined to the outer peripheral edge 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 balls 2 used, and in particular, the thickness of the mask body 10 (including the thickness of the support protrusions 23 when provided) is designed to match the diameter of the solder balls 2 used. It is preferable that the diameter be approximately the same as that of No. 2.

On the lower surface side of the mask main body 10, that is, on the side facing the workpiece 3, a support protrusion 23 is provided to protrude downward and ensure a facing distance from the workpiece 3. The support protrusion 23 has an inverted truncated conical shape, and its lower end surface always comes into contact with the surface of the workpiece 3 during the process of arranging the solder balls 2, thereby ensuring a spacing between the mask 1 and the workpiece 3. The support protrusions 23 can be provided in a lattice frame shape so as to surround the pattern area 13. Although the support projections 23 are integrally formed with the mask body 10, they may be formed separately and integrally joined to the mask body 10.

The operation of arranging the solder balls 2 using the mask 1 is performed in the following procedure. First, the flux 24 is applied by printing onto the electrode 6 of the workpiece 3 (see FIG. 3). Next, ball insertion hole 1
After positioning the mask 1 on the workpiece 3 so that the electrode 6 and the mask 2 coincide with each other, the mask 1 is fixed. This positioning work is actually performed by aligning the outer peripheral edges of the frame 11 and the workpiece 3. Note that a magnet can be placed below the workpiece 3, and after the alignment work is completed, the mask 1 can be inseparably and integrally fixed to the workpiece 3 by the magnetic attraction force of the magnet. In this fixed state, the lower end surface of the support protrusion 23 comes into contact with the surface of the workpiece 3, so that the mask 1 is maintained in a spaced-apart attitude with a facing distance from the workpiece 3 as shown in FIG.

Next, a large number of solder balls 2 are supplied to the opening of the frame 11, that is, 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-like tip. The solder balls 2 are inserted into the insertion holes 12 one by one. 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 ball 2 into the insertion hole 12, and the solder ball 2 is placed on the electrode 6. Have it installed. The solder ball 2 inserted into the insertion hole 12 is adhesively held temporarily with flux 24. Finally, after removing the remaining solder balls 2 from the upper surface of the mask 1, the mask 1 is removed and the solder balls 2 are heated and melted to form solder bumps on the electrodes 6 of the workpiece 3.

4 and 5 show a method of manufacturing the array mask 1 according to this embodiment. First, Figure 4(a)
As shown in FIG. 2, a photoresist layer 28 is formed on the surface of a conductive matrix 27 made of stainless steel or brass, for example. This photoresist layer 28 can be formed by laminating one or several negative-type photosensitive dry photoresists to a predetermined height and bonding them under heat. Next, on the photoresist layer 28, an inverted truncated conical support projection 23 is formed.
After closely adhering a pattern film 29 (glass mask) having transparent holes 29a corresponding to the patterns, exposure is performed by irradiating ultraviolet light with an ultraviolet lamp 30, and processing of development and drying is performed.
By dissolving and removing the unexposed portions, a primary pattern resist 31 having resist bodies 31a corresponding to the support protrusions 23 was formed on the matrix 27, as shown in FIG. 4(b).

Next, the mother mold 27 is placed in an electroforming bath prepared under predetermined conditions, and is covered with the resist body 31a of the mother mold 27 within the height range of the resist body 31a, as shown in FIG. 4(c). A primary electroformed layer 32 was formed by electroforming an electrodeposited metal such as nickel on the uncoated surface. Here, the primary electroformed layer 32 was formed over substantially the entire surface of the matrix 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 process, it is desirable that the surface of the primary electroformed layer 32 be subjected to a polishing process or a peeling process after the primary pattern resist 31 is removed.

Subsequently, as shown in FIG. 5(a), a photoresist layer 35 is formed on the entire surface of the primary electroformed layer 32 and the matrix 27, and then insertion holes 12 are formed on the surface of the photoresist layer 35.
After closely adhering a pattern film 36 (glass mask) having transparent holes 36a corresponding to the patterns, exposure is performed by irradiating ultraviolet light with an ultraviolet light lamp 30, and processing of development and drying is performed.
By dissolving and removing the unexposed portions, a secondary pattern resist 37 having resist bodies 37a corresponding to the insertion holes 12 as shown in FIG. 5(b) was formed on the surface of the primary electroformed layer 32.

Subsequently, the mother mold 27 is placed in an electroforming bath prepared under predetermined conditions, and the primary electroforming is carried out within the height range of the resist body 37a that is not covered by the mother mold 27 and the resist body 37a. A secondary electroformed layer 38 was formed by electroforming an electrodeposited metal such as nickel on the surface of the layer 32 . Next, the secondary pattern resist 37 is dissolved and removed, and the matrix 27 and the primary electroformed layer 32 are peeled off (removed) from the secondary electroformed layer 38, as shown in FIGS. 5(d) and 3. A mask body 10 was obtained. Finally, by joining the frame 11 to the mask main body 10, a mask 1 as shown in FIG. 2 can be obtained.

The secondary electroformed layer 38, ie, the mask body 10, can be supported on the frame 11 under tension such that stress in the direction of inward contraction is applied to itself.
In other words, the mask body 10 is supported by the frame 11 in a state where tension is applied to the mask body 10, and in this form, before the secondary electroformed layer 38 is peeled off from the matrix 27, the secondary electroformed layer 38 is Electroformed layer 38
This can be realized by joining the mask body 10 and the frame 11. According to this, the expansion of the mask body 10 due to a change in the ambient temperature can be absorbed by the tension in the contraction direction, so that misalignment of the mask body 10 with respect to the workpiece 3 can be prevented. Moreover, since uniform tension can be applied to the entire mask body 10, the solder balls 2 can be mounted on the workpiece 3 with high positional accuracy.

As described above, in the arraying 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 plan view. Even when tension is applied to the mask body 10 during joining to the mask body 11, the mask body 1
0 can be effectively prevented from being damaged. That is, in general, the stress that acts on the opening edge of the insertion hole 12 due to the tension of the mask body 10 tends to concentrate at a location where the opening edge shape of the insertion hole 12 changes rapidly. In the case of a rectangular shape, stress is concentrated at right-angled corners, and damage is likely to occur from the right-angled corners. On the other hand, if the insertion hole 12 is formed in a rounded square shape with rounded corners as in this embodiment, the corners It is possible to prevent sudden changes in the shape of the opening edge at the rounded corners and to distribute stress 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 square ball insertion holes. There is also the advantage that the flatness of the arraying mask 1 can be maintained by suppressing distortion of the mask body 10 (mask 1) caused by deformation of the ball insertion holes 12 due to stress concentration. Furthermore, compared to a mask having a circular ball insertion hole, the chances of contact between the opening edge and the solder ball can be reduced, so it is possible to drop the solder ball 2 into the insertion hole 12 more smoothly. It is also possible to improve the mounting rate of the solder balls 2 using the array mask 1.

In addition, in this embodiment, a quarter-arc-shaped (partial arc-shaped) rounded portion 17 located at a corner of a rounded regular quadrilateral and a side portion of the rounded regular quadrilateral are configured and connected tangentially to the rounded portion 17. Since the opening edge of the ball insertion hole 12 is formed by the straight line portion 16, the opening edge of the ball insertion hole 12 can be configured so that the rounded portion 17 and the straight portion 16 are smoothly connected. As a result, it is possible to eliminate the formation of an inferior angle bend at the opening edge of the ball insertion hole 12 where stress tends to concentrate, thereby making it possible to more effectively prevent damage and deformation of the mask for arranging the solder balls 2 due to stress concentration. can be prevented.

When the relationship between the side dimension D of the virtual regular quadrilateral (virtual regular polygon) 18 and the length dimension d1 of the corner straight section 20 is configured to satisfy the inequality (d1<D/2), the opening of the ball insertion hole 12 By making the curvature of the rounded portion 17 as small as possible within a range that does not make the edge circular, stress can be sufficiently dispersed at the corner portion. In each of the embodiments described above, the relationship between the side dimension D of the virtual square 18 and the length dimension d1 of the corner straight section 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 disperse stress at the corner portion. Moreover, if the length dimension d1 exceeds D/3, the straight portion 16 will not be sufficiently secured,
Solder ball 2 becomes easily damaged. This also causes a deterioration in the mounting rate of solder balls 2.

(Example 2) FIG. 6 shows Example 2 of a mask for arranging solder balls according to 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) in the moving direction of the squeegee brush 25 is , two rounded portions 1 located on the downstream side (right side side) in the moving direction of the squeegee brush 25.
Length dimension d1b (d1) of corner straight part 20 of 7b (17) (radius of rounded part 17b)
This differs from the first embodiment in that it is set smaller than . The length dimension d1a of the rounded portion 17a is D
/4, and the length dimension d1b of the rounded portion 17b was set to D/3. Since the rest is the same as in Example 1, the same members are given the same reference numerals and their explanations will be omitted. The same applies to the following examples.

According to the insertion hole 12 as described above, the length of the straight portion 16 on 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 above the ball insertion hole 12 in a plan view, the solder ball 2 tends to fall into the ball insertion hole 12, so the upstream side (left side) in the direction of movement of the squeegee brush 25 By increasing the length of the linear portion 16 (side), the solder balls 2 can be easily guided into the ball insertion holes 12, and the mounting rate of the solder balls 2 can be improved. Furthermore, 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, it is possible to suppress the squeegee brush 25 from getting caught on the right side portion located on the downstream side in the moving direction. , the squeegee brush 25 can smoothly pass over the ball insertion hole 12.

(Example 3) FIG. 7 shows Example 3 of a mask for arranging solder balls according to the present invention. In this embodiment, contrary to the previous embodiment 2, the length dimension d1a ( d
1) (the radius of the rounded portion 17a) is the length dimension d1b(d1)(
The radius of the rounded portion 17b is set larger than the radius of the rounded portion 17b. The length dimension d1a of the rounded portion 17a is D/
3, and the length dimension d1b of the rounded portion 17b was set to D/4. Such insertion hole 1
According to No. 2, the solder ball 2 can be quickly dropped into the insertion hole 12. Specifically, the outer surface of the solder ball 2 on its way down into the insertion hole 12 comes into contact with the inner surface of the insertion hole 12 on the downstream side in the direction of movement of the squeegee brush 25 . Therefore, if the length of the straight portion 16 on the downstream side in the moving direction of the squeegee brush 25 is increased, the contact area between the outer surface of the solder ball 2 and the inner surface of the insertion hole 12 in the middle of falling is reduced, and the solder ball 2 is It is possible to suppress the braking of the falling motion due to the friction between the two when falling, and the solder ball 2 can be quickly dropped into the ball insertion hole 12. As a result, solder ball 2 on the way down
can be prevented from being scraped out of the ball insertion hole 12 by the squeegee brush 25.

In each of the embodiments described above, the connecting portion between the straight portion 16 and the rounded portion 17 is configured to be tangentially connected, but a slightly inferior corner portion may be formed at the connecting portion between the two. In this case, in order to avoid stress concentration, it is desirable that the angle of the corner be close to 180 degrees.
Although each of the rounded portions 17 is constituted by a quarter circular arc, the rounded portion 17 may be constituted by a quarter elliptical arc. Even in this case, it is preferable that the adjacent straight portions 16 are connected tangentially to the rounded portion 17, so that the rounded portion 17 and the straight portion 16 are smoothly connected. Also in this case, the length dimension d1 of the corner straight portion 20 is (D/4≦d1≦D
It is preferable that the following inequality is satisfied: /3).
One side (front side) and the other side (rear side) in the direction orthogonal to the moving direction of the squeegee brush 25
In this case, it is possible to change the length d1 of the corner straight portion 20. Further, the length dimension d1 may be made different at each corner portion of the insertion hole 12.

FIG. 8 shows a modification of the insertion hole 12. FIG. 8(a) shows the opening edge of the insertion hole 12 as a rounded equilateral triangle (rounded regular polygon) in plan view, and FIG. 8(b) shows the opening edge of the insertion hole 12 in plan view. In FIG. 8(c), the opening edge of the insertion hole 12 is a regular hexagon with rounded corners (regular rounded polygon) in plan view. Also in these modified examples, the adjacent linear portion 16 is
- 16 is configured to have a tangential connection, and the rounded portion 17 and the straight portion 16 are smoothly connected. The regular polygon with rounded corners forming the insertion hole 12 in this way is not limited to the regular square with rounded corners shown in each of the above embodiments.

(Example 4) FIG. 9 shows Example 4 of a mask for arranging solder balls according to the present invention. In this embodiment, the opening edge of the insertion hole 12 is a straight line portion 4 forming the sides of a regular quadrangle (regular polygon).
1 and a partial arc portion 43 bulging outward at each vertex 42 constituting the regular quadrilateral. The radius dimension R of the partial circular arc portion 43 is set to 1/8 of the length dimension L of the side of the square formed by the opening edge of the insertion hole 12, and the connecting portion between the straight portion 41 and the partial circular arc portion 43 is rounded with a smaller radius than the radius R of the partial arc portion 43. The insertion hole 12 has two linear portions 41, which are the front and rear sides of a regular quadrangular shape, whose extension directions match the moving direction (left-right direction) of the squeegee brush 25, and two straight quadrangular opposing straight portions 41. - The extension direction of 41 is inclined at 45 degrees with respect to the moving direction (left-right direction) of the squeegee brush 25, and these are arranged alternately in a staggered manner. Note that the regular polygon forming the opening edge of the insertion hole 12 is not limited to a regular square, and may be, for example, a regular triangle, a regular pentagon, or the like. Moreover, the radius dimension R of the partial circular arc portion 43 is (L/8<R≦L/2)
It is preferable that the configuration is such that the following inequality is satisfied.

According to the insertion hole 12 as described above, it is possible to eliminate the formation of inferior angle-shaped opening edges where stress tends to concentrate at the corner portions of the ball insertion hole 12. Therefore, according to the present invention, compared to the opening edges of polygonal ball insertion holes having the same number of angles, it is possible to suppress a sudden change in the shape of the opening edge at the corner, thereby reducing stress on the rounded corner. This can be applied in a dispersed manner, and therefore, it is possible to obtain an array mask that is less likely to be damaged even when tension is applied, compared to a mask having polygonal ball insertion holes. Compared to a mask with a circular ball insertion hole, the chances of contact between the opening edge and the solder ball can be reduced, so the solder ball 2 can fall more smoothly into the insertion hole 12, and the solder It is also possible to improve the loading rate of the balls 2. Furthermore, the partial arc portion 43 serves as a guiding portion for the solder ball 2, and the solder ball 2 that has reached the partial arc portion 43 can be guided into the insertion hole 12. At this time, if an inclined surface is provided that slopes downward from the partial arc portion 43 to the straight portion 41, the guiding function of the partial arc portion 43 to the insertion hole 12 can be more effectively exhibited. Note that at least the region surrounded by the partial arc portion 43 may be formed in a bottomed shape (non-penetrating).

(Reference Example) Although the insertion hole 12 in each of the above embodiments has a regular polygon as the standard shape of the opening edge, the standard shape of the opening edge may be a rectangle. Moreover, it can also be constructed of convex polygons, concave polygons, star-shaped polygons, 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 fall into it.

1 Arraying mask 2 Solder balls 3 Workpiece 12 Ball insertion hole 16 Straight section 17 Rounded section 17a Rounded section 17b located on the upstream side in the direction of movement of the squeegee Rounded section 18 located on the downstream side in the direction of movement of the squeegee Virtual regular polygon (virtual square)
19 Vertex portion 20 Corner straight portion 25 Squeegee (squeegee brush)
41 Straight line part 42 Vertex part 43 Partial arc part D Side dimension of virtual regular polygon d1 Length dimension of corner straight part d1a Length dimension of corner straight part of rounded part 17a Length dimension of corner straight part of rounded part 17b

Claims (2)

A ball insertion hole (12) corresponding to a predetermined arrangement pattern is provided, and by transferring the solder ball (2) into the ball insertion hole (12), the solder ball (2) is placed at a predetermined position on the workpiece (3). An array mask to be mounted,
The opening edge of the ball insertion hole (12) has a partially arcuate rounded part (17) and a straight part (16) tangentially connected to the rounded part (17),
In the moving direction of the squeegee (25) for transferring the solder ball (2) into the ball insertion hole (12) , the radius (r) of the rounded portion (17) located on the upstream side in the moving direction of the squeegee (25) is: An arraying mask characterized in that the radius (r) of the rounded portion (17) located on the downstream side in the moving direction of the squeegee (25) is smaller than the radius (r) . A ball insertion hole (12) corresponding to a predetermined arrangement pattern is provided, and by transferring the solder ball (2) into the ball insertion hole (12), the solder ball (2) is placed at a predetermined position on the workpiece (3). An array mask to be mounted,
The opening edge of the ball insertion hole (12) has a partially arcuate rounded part (17) and a straight part (16) tangentially connected to the rounded part (17),
In the moving direction of the squeegee (25) for transferring the solder ball (2) into the ball insertion hole (12), the radius (r) of the rounded portion (17) located on the upstream side in the moving direction of the squeegee (25) is: An arraying mask characterized by having a radius (r) larger than the radius (r) of the rounded portion (17) located downstream in the direction of movement of the squeegee (25) .