JPH0927676A - Solder ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately position solder balls which are used for electrically connecting an electronic component and to prevent connection failures and solder bridges caused by movement or fall of solder balls by a method wherein a flat area is provided in the peripheral surface of the solder ball to form a joining part joined to an electronic component. SOLUTION: A solder ball 10 is composed of a core 11 and a solder plating layer which covers the surface of the core 11. A flat area is provided to the solder ball 10 to serve as a flat joint 10a. The area of the flat joining part 10a is determined considering the necessary amount of solder for connecting an electronic component and the stability of the solder ball 10. By this setup, a solder ball can be easily and accurately positioned, and an electronic component can be protected against connection failure caused by movement or fall of the solder ball. The solder ball can be held with flux of low adhesion without using cream solder of high adhesion, so that solder can be supplied constant in volume, and solder bridges can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder ball used for connecting electronic components such as a semiconductor element and a printed circuit board, and more particularly to a solder ball suitable for connecting fine-pitch electronic components.

[0002]

2. Description of the Related Art Solder balls can be supplied at a constant amount by making the diameter of the solder balls constant, so that the occurrence of solder blitch can be effectively prevented. Due to these advantages, solder balls are now widely used for connection of electronic components having fine-pitch terminals (see, for example, JP-A-2-244696 and JP-A-2-2696).
No. 238693).

[0003] As shown in FIG.
In No. 0, a spherical core material 101 made of copper and high temperature solder was solder-plated 102. Such a conventional solder ball 100 has been mounted on the electrodes of an electronic component through the steps shown in FIGS. 7A to 7C.

That is, as shown in FIG. 7A, a required number of solder balls 100 are suctioned by suction nozzles 200, and the suction nozzles 200 are moved above the electronic component 300, and the solder balls 100 are moved to respective electrodes. Part 301. Note that a flux (or cream solder) 302 was applied to these electrodes 301 in advance.

Next, as shown in FIG. 7B, the suction nozzle 200 is lowered to release the suction of the suction nozzle 200, and the solder ball 100 is mounted on the electrode 301.
Thereafter, as shown in FIG. 7C, the electronic component 300 was heated in a reflow furnace 400 to melt the solder plating 102 and connect the solder ball 100 to the electrode 301.

[0006]

However, the conventional solder ball 100 described above has a spherical shape, so that it easily rolls, and a low-adhesive flux 302 is interposed between the solder ball 100 and the electrode 301. With only this, there is a problem that the solder ball 100 rolls and moves from the electrode 301 or falls off before the electronic component 200 is heated in the reflow furnace 300. In addition, when the solder ball 100 moves or falls, any one of the electrodes 30
There is also a problem that connection failure such as non-connection occurs in No. 1.

In this case, it is conceivable to position the solder ball 100 on the electrode 301 by using a flux having a high adhesive force, but there is a problem that it is difficult to remove the flux by cleaning.

When cream solder is interposed,
Due to the high adhesive strength, the solder ball 100 is connected to the electrode 301.
However, it is difficult to supply a certain amount of cream solder, and if the supply amount of cream solder becomes excessive, there is a problem that solder blitch occurs, The advantage of the solder ball, which is effective for connecting pitched electronic components, is diminished.

In order to facilitate the positioning of the spherical solder ball, for example, Japanese Utility Model Laid-Open No. 58-15862 proposes forming a concave portion in a soldered portion of a wiring pattern. However, it takes time and effort to form a concave portion in a wiring pattern, and particularly in the case of high-density mounting, it is difficult to form a concave portion in a fine wiring pattern.

Further, Japanese Patent Laid-Open No. 192499/1989 proposes a method of forming a spherical powder solder by compressing the powder solder into a lump and then crushing the lump into an amorphous powder solder. With such an amorphous powder solder, it is possible to prevent the solder from rolling and to easily perform positioning. However, in the case of the irregular-shaped powder solder, the supply amount of the solder cannot be made constant, and there is a problem that a solder blitch occurs in the connection of the electronic component having a fine pitch.

The present invention has been made in view of the above-mentioned problems, allows easy and accurate positioning, and reliably prevents connection failure due to movement and drop of solder balls and occurrence of solder blitches. The purpose is to provide a solder ball that can be manufactured.

[0012]

In order to achieve the above object, the solder ball according to claim 1 is a solder ball used for electrical connection of electronic parts, and at least a part of the sphere is made flat. It is formed by molding to form a joint with the electronic component. According to such a configuration, the solder balls can be placed on the electronic component by bringing the planar joints into contact with each other, so that the solder balls can be prevented from rolling and the solder balls can be easily and accurately arranged. Can be positioned.

A solder ball according to a second aspect of the present invention has a structure in which the entire joint portion of the solder ball is flat. According to such a configuration, the solder ball can be placed in surface contact with the electronic component and mounted, so that the solder ball can be positioned in a more stable state.

A solder ball according to a third aspect of the present invention has a structure in which a joint portion of the solder ball has an uneven shape. According to such a configuration, the surface area of the bonding portion is increased, and the solder ball can be firmly held by the low-adhesion flux. Further, since the joint portion has a planar shape like the solder ball according to the first aspect, it is possible to prevent the solder ball 80 from rolling.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the solder ball of the present invention will be described with reference to the drawings. First, a solder ball according to a first embodiment of the present invention will be described.
FIG. 1 is a sectional view showing a solder ball according to the first embodiment of the present invention.

In FIG. 1, reference numeral 10 denotes a solder ball;
The surface of the core material 11 is formed by applying a solder plating 12. A part of the solder ball 10 is formed in a flat shape, and the whole is a flat joint portion 10a. Here, the area of the joint 10a is determined by comparing the amount of solder required for connecting the electronic components and the stability of the solder ball. Further, the core material 11 having a special shape is mass-produced by a molding die.

Next, a process of mounting the solder ball having the above-mentioned structure on an electronic component will be described with reference to FIGS. 2 (a) to 2 (d). 2A to 2D are explanatory views showing a series of mounting steps of the solder ball.

First, as shown in FIG. 2A, a required number of solder balls 10 are arranged on an alignment stage 20, and this alignment stage 20 is vibrated. As a result, all the solder balls 10 on the alignment stage 20 are aligned with the joint 10a facing downward.

Next, as shown in FIG. 2B, the solder ball 10 on the alignment stage 20 is sucked by the suction nozzle 30, and the suction nozzle 30 is moved above the electronic component 40, and the solder ball 10 is It faces the electrode section 41. Further, on the electrode 41 of the electronic component 40, a flux 42 having a low adhesive strength is applied in advance. The electronic component 40 is not limited to a surface mount component such as a semiconductor element, but includes a printed circuit board.

Next, as shown in FIG. 2C, the suction nozzle 30 is lowered to release the suction of the suction nozzle 30,
The solder ball 10 is placed on the electrode 41. After that, Figure 2
As shown in (d), the electronic component 40 is heated in the reflow furnace 50 to melt the solder plating 12 and connect the solder ball 10 to the electrode 41.

According to the solder ball of the present embodiment as described above, a flat joint portion 10 a
Is formed, so that the solder ball 10 is
Flux 4 with low adhesive strength
2, the solder ball 10 can be held in a stable state, the rolling of the solder ball 10 can be prevented, and the solder ball 10 can be positioned easily and accurately.

Next, a solder ball according to a second embodiment of the present invention will be described. FIG. 3 is a sectional view showing a solder ball according to a second embodiment of the present invention.

As shown in FIG. 1, the solder ball 60 of the present embodiment has a configuration in which a joint 60a has an uneven shape. According to such a configuration, the surface area of the joint portion 60a is enlarged, and the solder ball 60 can be more firmly held by the low-adhesion flux. Further, since the joint portion 60a is entirely flat, it is possible to prevent the solder ball 60 from rolling.

Next, a solder ball according to a third embodiment of the present invention will be described. FIG. 4 is a sectional view showing a solder ball according to the third embodiment of the present invention.

As shown in the figure, the solder ball 70 of the present embodiment has a configuration in which the unevenness of the joint 70a is triangular.

According to such a configuration, similarly to the second embodiment, the surface area of the joint portion 70a is increased, and the solder ball 70 can be held more firmly by the low-adhesion flux. In addition, since the joint portion 70a is entirely flat, it is possible to prevent the solder ball 70 from rolling.

Next, a solder ball according to a fourth embodiment of the present invention will be described. FIG. 5 is a sectional view showing a solder ball according to the fourth embodiment of the present invention.

As shown in the figure, the solder ball 80 of the present embodiment has a configuration in which the entire joint 80a is depressed in a hemispherical shape.

According to such a configuration, the total amount of solder forming the solder ball 80 can be adjusted by changing the depth of the depression of the joint portion 80a, so that an appropriate amount of solder can be easily supplied. it can. This makes it possible to more reliably prevent the occurrence of a solder bridge. Also,
Since the joint portion 80a is entirely flat, the solder balls 80 can be prevented from rolling.

The solder ball of the present invention is not limited to the first to fourth embodiments. For example, in these embodiments, the solder balls 10, 60, 7
Joints 10a, 60a, 70a, 80 on a part of 0, 80
However, the present invention is not limited to this, and the joining portions 10a, 60a, 7 are provided at two places on the upper side and the lower side.
0a and 80a may be formed.

With such a structure, the solder ball 1
When the electronic component 40 is connected to another electronic component via the solder balls 10, 60, 70 after connecting 0, 60, 70 to the electronic component 40, the solder balls 10, 60, 70 are also connected to other electronic components. Since they are in surface contact or line contact, the electronic component 40
And other electronic parts can be connected easily and surely.

Further, the solder ball joint portion of the present invention is not limited to the shape shown in FIGS. 1 and 3 to 5, but may have any shape in which the contact surface with the electronic component is entirely flat. Things are included.

Further, the concavo-convex shape of the joint portion in the present invention is not limited to those shown in FIGS. 3 and 4, but includes those having protrusions and depressions and all shapes having undulations.

[0034]

As described above, according to the solder ball of the present invention, the solder ball can be positioned easily and accurately, and the defective connection of the electronic component due to the movement and the drop of the solder ball can be prevented. . In addition, since the solder balls can be sufficiently held by the low-adhesion flux without using the high-adhesion cream solder, the supply amount of the solder can be always kept constant, and the occurrence of solder blitch can be prevented. it can. Therefore, the solder ball of the present invention, in particular,
It has a tremendous effect in connecting fine pitch electronic components.

[Brief description of drawings]

FIG. 1 is a sectional view showing a solder ball according to a first embodiment of the present invention.

FIGS. 2A to 2E are explanatory views showing a series of mounting steps of the solder ball.

FIG. 3 is a sectional view showing a solder ball according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a solder ball according to a third embodiment of the present invention.

FIG. 5 is a sectional view showing a solder ball according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view showing a conventional solder ball.

FIGS. 7A to 7C are explanatory views showing a series of mounting steps of a conventional solder ball.

[Explanation of symbols]

 10, 60, 70, 80 Solder ball 10a, 60a, 70a, 80a Joint part 11, 61, 71, 81 Core material 12, 62, 72, 82 Solder plating

Claims (3)

[Claims] 1. A solder ball used for electrical connection of an electronic component, characterized in that at least a part of a sphere is formed into a flat surface to form a joint with the electronic component. 2. The solder ball according to claim 1, wherein the entire joint portion of the solder ball is flat. 3. The solder ball according to claim 1, wherein a joint portion of the solder ball has an uneven shape.