JP2002368034A - Bump forming apparatus and bump forming method using the same - Google Patents

Abstract

An object of the present invention is to provide a bump forming apparatus and a bump forming method in which an interval between an electronic component and a substrate is ensured and a short circuit between adjacent bumps is suppressed. SOLUTION: A chamfer 3 of a capillary 1 is composed of first to third inclined portions 4 to 6, and a first chamfer diameter φD1.
Is greater than 83% of the bump diameter φD4, the first chamfer angle θ1 is 30 ° or more and 60 ° or less, the second chamfer angle θ2 is 45 ° or more and 90 ° or less, and the third chamfer angle is θ3 is 0 degrees. Also,
The clearance between the hole diameter φD3 and the wire diameter φD5 is 5
It is not less than μm and not more than 8 μm. Then, the bumps 20 are formed by one ball bonding using the capillary 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bump forming apparatus for forming a bump projecting from one side of an electronic component and joining the electronic component and the substrate when mounting the electronic component on a substrate. The present invention relates to a bump forming method using the same.

[0002]

2. Description of the Related Art Conventionally, as a method of mounting an electronic component using a bump of this type, there is, for example, flip chip mounting. This flip chip mounting is disclosed in Japanese Patent No. 263374.
As described in No. 5, first, a projection (bump) made of Au or the like is formed on an electrode pad of a semiconductor chip as an electronic component by a wire bonding method.

Then, after forming a solder layer on the tip of the bump, the semiconductor chip is mounted on the substrate surface with the side on which the bump is formed facing the substrate side (face down), and the solder layer is melted. The semiconductor chip and the terminal electrode of the substrate are joined.

In this wire bonding method, a bump is formed by using a capillary which is a manufacturing apparatus for forming a bump. A wire for forming a bump is passed through a capillary to a tip of the wire. A ball is formed, and the ball is pressed against the electrode pad at the tip of the capillary to form a bump. Hereinafter, such a bump forming method is referred to as a stud bump method.

[0005] In such flip-chip mounting, by injecting and curing an underfill resin between the semiconductor chip and the substrate, the thermal fatigue of the joint caused by the difference in the thermal expansion coefficient between the semiconductor chip and the substrate. A method for improving the service life is proposed in Japanese Patent No. 2675003.

When the underfill resin is injected as described above, it is necessary to increase the distance between the semiconductor chip and the substrate in order to improve the injectability of the underfill resin. In addition, even when the underfill resin is not injected, the thermal stress caused by the difference in the coefficient of thermal expansion between the semiconductor chip and the substrate, which acts on the joint between the substrate and the bump and the solder layer, is reduced by bending the bump. In addition, it is necessary to increase the height of the bump by increasing the distance between the semiconductor chip and the substrate, so that the bump is more easily bent.

[0007]

However, a fine pitch electrode (for example, 140 μm) corresponding to a recent narrow pitch is required.
(m pitch or less), the height of a bump that can be formed by a general-purpose bonding capillary is low (about 30 to 50 μm). For example, the electrode pitch is 140 μm and the diameter is 90 μm.
The height of the bump m is 45 μm. Therefore, to increase the distance between the semiconductor chip and the substrate, the thickness of the solder layer formed on the bump must be increased.

However, when the amount of solder is increased, the spread of the solder cannot be suppressed when the semiconductor chip and the substrate are joined, so that the adjacent solder is short-circuited in the fine pitch electrode.

On the other hand, a plurality of methods have been proposed in which the bumps are raised by forming the bumps in two layers. Among them, the technique described in Japanese Patent Application Laid-Open No. 8-264540 discloses that the second-stage bump is formed by a stud bump method, so that the ultrasonic amplitude applied to secure the bonding reliability with the first-stage bump is increased. And the load causes the first bump to be crushed.

As a result, the height of the bumps is reduced as a whole, and the height varies greatly. In addition, the risk that the crushed first-stage bump is short-circuited with an adjacent bump or electrode is increased. Furthermore, if the position of the first-stage bump and the position of the second-stage bump are slightly displaced, the second-stage bump is greatly deformed, so that there is a high possibility of short-circuiting with an adjacent bump.

As another example of a method for forming bumps in two steps, there is a technique described in Japanese Patent Application Laid-Open No. 7-176534. In this technique, the short-circuit between adjacent bumps is suppressed by making the diameter of the second bump smaller than the diameter of the first bump. However, since the height of the second bump is reduced, the effect of increasing the height of the entire bump is small.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a bump forming apparatus which secures an interval between an electronic component and a substrate and suppresses a short circuit between adjacent bumps when an electronic component and a substrate are joined by bumps. And a method of forming a bump.

[0013]

In order to form a bump by using the stud bump method, the present inventor uses a bump forming apparatus (capillary) to connect a ball formed at the tip of a wire to an electrode pad or the like. We paid attention to the point that the height of the bump depends on the shape of the part pressed against the member.

According to the first aspect of the present invention, there is provided a bump forming apparatus for forming a bump (20) on a member (31) to be joined, wherein a wire (2) for forming a bump is provided. And a pressing portion (3) for pressing a ball (2a) formed at the distal end of the wire against the member to be joined, wherein the pressing portion has a pressing portion. Communicating with the inner hole (1a) of the tubular member,
In addition, the inner diameter is larger than the inner hole, and has a space opened at the tip of the tubular member. The diameter (φD1) of the cross section of the pressed portion at the opening of the tubular member is the diameter of the bump. (ΦD4) is greater than 83% of the length, a plurality of inclined portions (4 to 6) are formed on the inner wall of the pressing portion, and a portion of the plurality of inclined portions closest to the opening is formed. The first inclined portion (4) has an inclination angle (θ1) with respect to a plane normal to the axis of the cylindrical member of 30 ° or more and 60 ° or less, and the sectional area of the space portion approaches the opening. The second inclined portion (5) connected to the first inclined portion and formed on the side opposite to the opening has an inclination angle (θ2 with respect to a plane whose normal line is the axis of the cylindrical member). ) Is 45 degrees or more 9
0 ° or less, and the cross-sectional area of the space portion on the side of the first inclined portion of the second inclined portion is greater than or equal to the cross-sectional area of the space portion on the side of the second inclined portion far from the first inclined portion. The third inclined portion (6) formed at the portion of the pressing portion farthest from the opening is a surface substantially perpendicular to the axis.

According to the present invention, when the ball is pressed against the member to be bonded to form the bump, the first inclined portion (4) secures the bonding strength of the peripheral portion of the bump and the second inclined portion (4).
The height of the bump can be secured in the inclined portion (5), and the bonding strength of the central portion of the bump in the third inclined portion (6) can be secured.

In addition, since the diameter (φD1) of the cross section at the opening of the cylindrical member (1) of the pressing portion (3) is large, the direction perpendicular to the axis of the cylindrical member in the first to third inclined portions. Can be made longer.

As a result, the area for pressing the bump can be increased by increasing the length of the first and third inclined portions in the direction perpendicular to the axis of the cylindrical member, so that the bonding strength of the bump can be increased, The height of the bump can be increased by increasing the slope.

Therefore, even if the bumps are not formed one on another,
Can be used to form a tall bump, so that when joining an electronic component and a substrate with a bump, a bump that secures the space between the electronic component and the substrate and suppresses short-circuiting of adjacent bumps A forming device can be provided.

In this case, in the second embodiment, the diameter (φD3) of the portion of the inner hole of the cylindrical member adjacent to the pressing portion and having the smallest sectional area and the diameter of the wire (φD
It is characterized in that the difference from 5) is 5 μm or more and 8 μm or less.

As described above, the diameter of the inner hole can be reduced by reducing the difference between the diameter of the inner hole and the diameter of the wire at the portion having the smallest cross-sectional area adjacent to the pressing portion,
Since the diameter of the space portion of the pressing portion can be increased by that amount, the length of the pressing portion in the direction perpendicular to the axis of the tubular member can be increased.

As a result, the length of the first and third inclined portions in the direction perpendicular to the axis of the cylindrical member is further increased to increase the bonding strength of the bump, and the second inclined portion is further increased to increase the bump strength. The height can be increased.

The invention described in claim 3 is the first or second invention.
A method for forming a bump formed by using the bump forming apparatus described in 1 above, wherein a wire for forming a bump is passed through the inner hole, and a ball is formed on the tip of the wire on the opening side of the tubular member. And a step of pressing the ball against the member to be joined by the pressing portion.

Accordingly, for the same reason as in claim 1,
When joining an electronic component and a board by a bump, it is possible to provide a bump forming method that secures an interval between the electronic component and the board and suppresses a short circuit of an adjacent bump.

The reference numerals in parentheses of the above means indicate the correspondence with specific means described in the embodiments described later.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) The embodiment shown in the drawings will be described below. FIG. 1 is a cross section of a stud bump capillary (a cylindrical member according to the present invention, hereinafter simply referred to as a capillary) 1 as a bump forming apparatus according to the present embodiment, and a bump 20 being formed using the capillary 1. FIG. For comparison, FIG.
In the figure, the outline of the cross section of the conventional general-purpose capillary 100 is indicated by a dashed-dotted line, and the outline of the cross section of the bump 200 being formed using the conventional capillary is indicated by a broken line.

In this embodiment, the bump pitch is 140 μm, the wire diameter (diameter) is 30 μm, and the diameter is 90 μm.
The case where m bumps are formed will be described. As shown in FIG. 1, a wire 2 for forming a bump is passed through an inner hole 1a of a capillary 1. The capillary 1 communicates with an inner hole 1 a of the capillary 1, and has a space that is larger in diameter than the inner hole 1 a and that opens at the tip of the capillary 1. The area surrounding this space is
The chamfer (pressing portion in the present invention) 3 presses the ball formed at the tip of the wire 2 against the member to be joined.

A plurality of inclined portions (three in the illustrated example) 4 to 6 are formed on the inner wall of the chamfer 3. Among these inclined parts 4 to 6, the inclined part that constitutes the part closest to the opening of the capillary 1 is referred to as a first inclined part 4. And
A region of the chamfer 3 surrounded by the first inclined portion 4 is referred to as a first chamfer portion.

The first chamfer diameter φD1, which is the diameter of the cross section at the opening of the capillary 1 in the first chamfer portion (pressing portion), is larger than the same portion in the conventional general-purpose capillary 100 indicated by a dashed line.
Specifically, the first chamfer diameter φD1 is larger than 83% of the bump diameter (diameter) φD4.

In the first inclined portion 4, an inclination angle θ1 (hereinafter referred to as a first chamfer angle) with respect to a plane whose normal line is the axis of the capillary 1 is not less than 30 degrees and not more than 60 degrees. The cross-sectional area of the space portion in the first chamfer portion increases as approaching the opening of the capillary 1. In addition, the capillary 1 in the first inclined portion 4
(Hereinafter, referred to as a first chamfer length) L1 is 4 μm or more and
μm or less.

A second inclined portion 5 is formed on the opposite side of the opening from the first inclined portion 4. The inclination angle θ2 (hereinafter, referred to as a second chamfer angle) of the second inclined portion 5 with respect to a plane having the axis of the capillary 1 as a normal line is not less than 45 degrees and not more than 90 degrees. The cross-sectional area of the space on the first inclined portion 4 side of the second inclined portion 5 is the first inclined portion 4.
It is larger than the cross-sectional area of the space on the side farther from.
Note that a region of the chamfer 3 surrounded by the second inclined portion 5 is referred to as a second chamfer portion.

Further, a third inclined portion 6 is formed in a portion of the chamfer 3 farthest from the opening of the capillary 1. In the present embodiment, the third inclined portion 6 is connected to the second inclined portion 5. Further, the third inclined portion 6 is a surface substantially perpendicular to the axis of the capillary 1. That is, in the present embodiment, the inclination angle (hereinafter, referred to as a third chamfer angle) θ3 of the third inclined portion 6 with respect to a plane whose normal line is the axis of the capillary 1 is 0 degree.

The hole diameter φD3, which is the diameter of the portion of the inner hole 1a of the capillary 1 adjacent to the chamfer 3 and having the smallest cross-sectional area, is determined by the conventional general-purpose capillary 1
00 is smaller than the same site. Specifically, the clearance, which is the difference between the hole diameter φD3 and the wire diameter φD5, is 5 μm or more and 8 μm or less.

In the present embodiment, since the capillary 1 has such a structure, when the ball is pressed against the member to be joined to form the bump 20, the first member is disposed near the member to be joined. By the first inclined portion 4 having the relatively small chamfer angle θ1, the bonding strength of the peripheral portion of the bump 20 can be ensured.

Further, the height of the bump 20 can be increased by the second inclined portion 5 having a relatively large second chamfer angle θ2. Further, the bonding strength at the center of the bump 20 can be ensured by the third inclined portion 6 which is substantially perpendicular to the axis. In addition,
Here, the term "substantially right angle" means that the ball is formed at a right angle so that the ball can be given such a force that the bonding strength at the central portion of the bump 20 can be suitably secured when the ball is formed on the member to be joined. Is shown.

Further, the first chamfer length L1 is
Since the bonding strength is set as small as possible so that the bonding strength of 0 can be ensured, the second chamfer diameter φD2, which is the diameter at the interface between the first and second chamfers, can be increased. Since the second chamfer angle θ2 is relatively large, the second chamfer height H2, which is the axial length of the capillary 1 in the second chamfer portion, can be increased. Therefore, a bump 20 having a large height can be formed.

The general-purpose capillary 100 is also used for wire bonding for electrically connecting distant parts via wires. In this case, when forming the second bond portion, the wire is pressed against the member to be joined by pressing the wire by the face portion, which is a portion substantially perpendicular to the axis of the capillary at the tip of the capillary.

Therefore, when the face length, which is the radial length of the face portion, is reduced, there is a problem that the bonding length of the second bond portion is reduced and the bonding strength is reduced. Therefore, when the first chamfer diameter φD1 is increased, the face length is reduced, and the bonding strength of the second bond portion is reduced. Therefore, the first chamfer diameter φD1 is changed to the bump diameter φD4.
83% or less.

Further, in the general-purpose capillary 100, when wire bonding is performed between distant portions, the clearance between the hole diameter and the wire diameter is increased in order to reduce the sliding resistance between the capillary and the wire during loop formation. Need
The clearance is larger than 8 μm and 16 μm or less. In particular, in order to form a long loop of 4 mm or more, a clearance of 13 μm or more is required.

On the other hand, the capillary 1 of the present embodiment
Is a capillary for stud bumps, and the face length may be small because it is not necessary to form the second bond portion. Further, since it is not necessary to form a loop, the clearance may be small. Therefore, the first chamfer diameter φD1
And the clearance between the hole diameter φD3 and the wire diameter φD5 is reduced.

As a result, the first chamfer diameter φD1 is increased and the clearance between the hole diameter φD3 and the wire diameter φD5 is reduced by the chamfer 3 (first to third inclined portions 4 to 5).
The length in the radial direction in 6) can be increased.
Therefore, by increasing the first chamfer length L1 and the third chamfer length L3, which is the radial length of the chamfer 3 in the third inclined portion 6, the area for pressing the bump 20 can be increased, and the ball can be covered. The force applied to the ball when pressed against the joining member can be increased, and the joining strength (joining reliability) of the bump 20 can be increased.

The chamfer 3 in the second inclined portion 5
The second chamfer length L2, which is the length in the radial direction, can be increased, and the second inclined portion 5 can be increased. Therefore, the second inclined portion 5 can be greatly extended in the oblique direction, and the second chamfer height H2 can be increased as compared with the case where the second chamfer angle θ2 is the same. Therefore, the height of the bump 20 can be increased.

When the capillary 1 having such a structure is used,
Since the chamfer height H10, which is the distance from the tip of the capillary 1 to the interface between the chamfer 3 and the inner hole 1a, is large, the bump 20 having a high height can be formed.

It has been experimentally confirmed that a bump having a large height can be formed if the dimensions of the chamfer 3 such as the chamfer angles θ1 to θ3 in the inclined portions 4 to 6 are as described above. .

Next, a method of forming bumps using the capillary 1 will be described by applying a method of flip-chip mounting a semiconductor chip as an electronic component on a circuit board. FIG. 2 is a schematic sectional view showing a method of mounting the semiconductor chip 31 on which the bumps 20 are formed on the circuit board 32.
FIG. 3 is a process chart showing a method for forming the bumps 20 on the semiconductor chip 31.

As shown in FIG. 2A, the semiconductor chip 3
An electrode pad 33 is formed on the front surface side of 1, and a portion of the surface other than the electrode pad 33 is covered with an insulating film 34. Then, the bumps 20 made of Au or the like are formed on the electrode pads 33. Next, a method of forming the bump 20 will be described.

First, as shown in FIG. 3A, the capillary 1 having the above-described structure is prepared, and the inner hole 1a of the capillary 1 is prepared.
Is passed through the wire 2 for forming the bump 20. As the wire 2, for example, a wire made of Au can be used. Then, a ball (initial ball) 2a is formed at the tip of the wire 2 on the opening side of the capillary 1 (step of forming a ball). The ball 2a is made larger than when a general-purpose capillary is used, and has a volume slightly larger than the volume of the chamfer 3.

Next, as shown in FIG. 3B, the balls 2a are connected to the electrode pads of the semiconductor chip 31 by the first to third inclined portions 4 to 6 of the chamfer 3 (in FIG. 3, the electrode pads and the insulating film are formed). (Omitted)) to perform ball bonding (pressing step). Thereby, the ball 2
a is formed into the shape of the chamfer 3 and joined to the electrode pad.

Subsequently, as shown in FIG. 3 (c), the wire 2 is bent at the upper part of the joined ball 2a, and cut as shown in FIG. 3 (d).

Then, as shown in FIG. 3 (e), the height of the bonded ball 2a is adjusted by hitting the wire 2 on the ball 2a bonded by the height adjusting plate 35.

In this way, the bump 2 shown in FIG.
0 is formed on the electrode pad of the semiconductor chip 31.

Next, as shown in FIG. 2B, a solder 36 is formed on the bump 20. This can be performed, for example, by a plating method or the like. And the semiconductor chip 3
The semiconductor chip 31 and the circuit board 32 are joined by mounting the semiconductor chip 1 face down on the circuit board 32 and melting the solder 36 by reflow or the like. If necessary, the semiconductor chip 31 may be used to improve the thermal fatigue life.
By injecting and curing an underfill resin between the semiconductor chip 31 and the circuit board 32, the mounting of the semiconductor chip 31 on the circuit board 32 is completed.

When the bumps 20 are formed by using the capillary 1 having the above-described structure, the bumps 20 having a large height can be formed by a single bonding operation. Can be formed. Further, even if the amount of the solder 36 formed on the tip of the bump 20 is small, the distance between the semiconductor chip 31 and the circuit board 32 can be increased.

As described above, it is possible to form the bump 20 having a small variation in the shape such as the above-mentioned crushed width, and at the same time, it is possible to reduce the amount of solder.
The bumps 2 adjacent to the bumps 2
It is possible to prevent a short circuit with 0 or an electrode of the circuit board 32. In the case of a fine pitch electrode, such a short circuit is particularly problematic. However, if the bumps 20 are formed using the capillary 1 of the present embodiment, such a short circuit can be suitably prevented.

Also, since the height of the bumps 20 is large, the bumps 20 are caused by the coefficient of thermal expansion between the semiconductor chip 31 and the circuit board 32 acting at the base of the solder 36 (the joint with the bump 20 and the joint with the circuit board 32). Since the thermal stress can be reduced by bending the bump 20, the thermal fatigue life of the joint with the solder 36 can be sufficiently ensured.

Further, since the distance between the semiconductor chip 31 and the circuit board 32 can be suitably increased, the injectability of the underfill resin can be improved.

Further, since the bumps 20 can be formed by one-time bonding, the bumps 20 having a large height can be formed without impairing the efficiency.

Next, a specific example in which the inventors have confirmed that a tall bump can be formed will be described.

The bump pitch is 140 μm and the diameter is 90 μm.
m bumps were formed using a 30 μm diameter wire. The first chamfer diameter φD1 of the capillary 1 was 84 μm, and the length was 93.3% of the bump diameter φD4. Also,
The first chamfer angle θ1 was 45 degrees, and the first chamfer length L1 was 6 μm. Further, the second chamfer angle θ2 was set to 85 degrees, and the second chamfer length L2 was set to 5 μm.
Further, the third chamfer angle θ3 was set to 0 degree, and the third chamfer length L3 was set to 13 μm. The hole diameter φD3 was 36 μm, and the clearance between the wire diameter φD5 and the hole diameter φD3 was 6 μm.

Then, the tip of the capillary is 86 μm in diameter.
Was formed to form the bump 20. For reference, when a general-purpose capillary was used, a ball having a diameter of 67 μm was formed.

FIG. 4 is a sectional view of the bump formed in this manner. In the drawing, the bumps formed using a general-purpose capillary are indicated by broken lines for reference. As shown in FIG. 4, the bump 20 of the present embodiment has a main bump height H21 corresponding to the chamfer height H10 of the capillary of 63 μm.
m, and the total bump height H22 from the interface with the semiconductor chip to the tip of the bump 20 was 91 μm. Incidentally, the height H30 from the interface with the semiconductor chip to the portion where the tip of the capillary 1 was in contact was 18 μm.
m.

For reference, when a general-purpose capillary was used, the main bump height H201 was 9 μm, and the total bump height H202 was 37 μm. Therefore, the bump 20 of the present embodiment has a main bump height of 7 times and a total bump height of about 2.5 times as compared with the case using a general-purpose capillary.
Could be doubled.

(Other Embodiments) In order to further increase the height of the bumps 20 in the above embodiment, a thin wire having a diameter as small as possible is used. When the dimensions of each part of the capillary 1 are within the range shown in the above embodiment, the hole diameter φD3 can be reduced. As a result, the second chamfer height L2 can be increased by increasing the second chamfer length L2, thereby increasing the second chamfer height H2. Therefore, the height of the bump 20 can be increased.

The bump 2 for the semiconductor chip 31
By reducing the third chamfer length L3 as long as the bonding quality of 0 can be ensured, the second chamfer length L2 is increased accordingly, the second chamfer height H2 is increased, and the height of the bump 20 is increased. The size may be increased.

When the electrode pad pitch (bump pitch) is different, the tip diameter φD6, which is the diameter of the portion where the outer wall of the capillary 1 is extended and the portion where the face of the capillary is extended intersects, It is preferable that the dimensions of each part of the capillary be within the range of the above embodiment by using a capillary that matches the pitch.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a capillary according to a first embodiment and bumps being formed using the capillary.

FIG. 2 is a schematic sectional view illustrating a method for mounting a semiconductor chip using bumps according to the first embodiment.

FIG. 3 is a process chart showing a bump forming method according to the first embodiment.

FIG. 4 is a cross-sectional view of the bump according to the first embodiment.

[Explanation of symbols]

1 ... Capillary (tubular member), 1a ... Inner hole of tubular member,
2 ... wire, 2a ... ball, 3 ... chamfer (pressing portion), 4 ... first inclined portion, 5 ... second inclined portion, 6 ... third inclined portion, 20 ... bump, 31 ... semiconductor chip (member to be joined) , Θ1: first chamfer angle, θ2: second chamfer angle, φD1: first chamfer length, φD3: hole diameter,
φD4: bump diameter, φD5: wire diameter.

Claims (3)

[Claims] A bump (2) is attached to a member (31) to be joined.
A bump forming apparatus for forming a bump (0), comprising: a tubular member (1) through which a wire (2) for forming the bump is passed; A pressing portion (3) for pressing the formed ball (2a) against the member to be joined is formed, and the pressing portion communicates with the inner hole (1a) of the tubular member and is more than the inner hole. It has a large diameter and a space opened at the tip of the cylindrical member, and the diameter (φD1) of the cross section of the pressing portion at the opening of the cylindrical member is the diameter of the bump (φD4). )
A plurality of inclined portions (4 to 6) are formed on the inner wall of the pressing portion, and a portion of the plurality of inclined portions that is closest to the opening is formed. The first inclined portion (4) has an inclination angle (θ1) with respect to a plane whose normal line is the axis of the cylindrical member being 30 degrees or more and 60 degrees or more.
Degrees or less, the cross-sectional area of the space increases as approaching the opening, and a second slope connected to the first slope and formed on the opposite side to the opening. The part (5) has an inclination angle (θ2) of 45 degrees or more and 90 degrees or less with respect to a plane having the axis of the cylindrical member as a normal line, and the second inclined part on the side of the first inclined part. A cross-sectional area of the space portion is equal to or larger than a cross-sectional area of the space portion on the side of the second inclined portion remote from the first inclined portion, and formed at a portion of the pressing portion farthest from the opening; The third inclined portion (6) is a surface substantially perpendicular to the axis. 2. A difference between a diameter (φD3) of a portion of the inner hole of the cylindrical member adjacent to the pressing portion and having a smallest cross-sectional area and a diameter (φD5) of the wire is 5 mm.
The bump forming apparatus according to claim 1, wherein the thickness is not less than 8 μm and not more than 8 μm. 3. A bump forming method formed by using the bump forming apparatus according to claim 1 or 2, wherein the wire for forming the bump is passed through the inner hole, and A method for forming a bump, comprising: a step of forming the ball at a tip portion of the wire on an opening side; and a step of pressing the ball against the member to be joined by the pressing section.