JP3493999B2 - Solder bump forming method and solder bump mounting method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder bump forming method for forming a solder bump on a circuit electrode of an electronic component or a substrate and a solder bump mounting method for mounting the solder bump on an electronic component or a substrate. .

[0002]

2. Description of the Related Art A method using solder bumps is known as a method for mounting electronic components. In this method, solder bumps, which are protruding electrodes of solder, are previously formed on the circuit electrodes of the electronic component, and the solder bumps are solder-bonded to the circuit electrodes such as a substrate. As a method of forming a solder bump, a method of mounting a solder ball on a circuit electrode of an electronic component or the like has been conventionally known.

By the way, CSP (Chip Size P)
In some cases, the surface on which the circuit electrodes are formed and the surface on which the solder bumps are formed may not be the same surface of the substrate. That is, a circuit electrode is formed on one surface of a tape-shaped substrate that constitutes a package, and a solder ball is mounted on the opposite side of the surface on which the circuit electrode is formed. Then, the solder balls are melted, and the molten solder is conducted to the circuit electrodes through the through holes of the substrate provided at the circuit electrode positions to form solder bumps. Here, due to the fine pitch of the circuit electrodes accompanying the miniaturization of electronic components, the through holes of the front holes are also reduced in diameter, and the number of cases of using the through holes smaller than the diameter of the solder balls to be mounted is increasing.

A conventional solder bump forming method in such a case will be described below with reference to the drawings. Figure 3
(A), (b), (c) is a partial cross-sectional view of a conventional tape-shaped substrate. In FIG. 3A, the circuit electrode 2 is formed on the lower surface of the tape-shaped substrate 1. A through hole 3 is provided at the position of the circuit electrode 2 on the substrate 1, and cream solder 4, which is a mixture of solder particles having a powder diameter of 30 μm or less and flux, is supplied into the through hole 3. After this,
Solder balls 5 are mounted on the through holes 3 as shown in FIG. Here, the diameter of the through hole 3 is smaller than the diameter of the solder ball 5. Therefore, the solder ball 5 does not completely enter the inside of the through hole 3, and the solder ball 5 and the surface of the circuit electrode 2 do not come into contact with each other to form a gap. It has become a shape.

After that, by feeding the substrate 1 to a reflow process and heating it, the cream solder 4 and the solder balls 5 are heated and melted, and the solder balls 5 and the solder particles in the cream solder 4 are melted by melting. The solder is integrated and solder-bonded to the surface of the circuit electrode 2 to form a solder bump.

[0006]

At this time, since the solder particles in the cream solder 4 have a small particle diameter, they are attracted to either side of the solder ball 5 or the circuit electrode 2 in the process of melting, as shown in FIG. In some cases, the portion absorbed by the solder ball 5 and the portion 4'welded to the surface of the circuit electrode 2 are separated as shown in FIG. In this way, once the molten solder has been completely separated, it is difficult to integrate the molten solder after that, and the solder ball 5 is not soldered to the electrode 2 and a solder bump is missing. The electronic component with the missing solder bump is discarded as a defective product, which causes a reduction in product yield.

As described above, the conventional solder bump forming method has a problem that the solder bumps cannot be reliably formed due to the behavior of the cream solder during melting. Also, this problem is that when mounting an electronic component having a spherical solder bump on a circuit electrode, that is, a through hole smaller than the diameter of the solder bump is provided in the resist covering the circuit electrode, and cream solder is supplied into this through hole. This is also common when mounting spherical solder bumps through the through holes.

Therefore, an object of the present invention is to provide a solder bump forming method and a solder bump mounting method capable of surely forming solder bumps and mounting the solder bumps.

[0009]

According to a first aspect of the present invention, there is provided a method of forming a solder bump, wherein a solder ball is solder-bonded to a circuit electrode through a through hole provided in the insulating substrate, and the solder ball is opposite to the circuit electrode of the insulating substrate. A method of forming a solder bump in which a solder bump is formed on a surface, wherein the solder ball is mounted on the through hole in the through hole having a diameter smaller than that of the solder ball. Supplying a solder bonding material containing solder particles of a size that can simultaneously contact both of the circuit electrode surfaces; mounting a solder ball on the through hole to which the solder bonding material is supplied; Heating the solder balls and melting the solder particles in the solder bonding material to structurally integrate the solder balls and the solder particles and solder bond them to the surface of the circuit electrode. Including.

The solder bump mounting method according to claim 2 is
A solder bump mounting method for solder-bonding a solder bump formed on an electronic component to the circuit electrode through a through hole provided in an insulating film covering a circuit electrode of the substrate to mount the solder bump on the substrate. A solder particle having a size smaller than the solder bump and having a diameter smaller than that of the solder bump and simultaneously contacting both the solder bump and the circuit electrode surface in a state where the solder bump is mounted on the through hole. A step of supplying a solder bonding material containing the solder bonding material, a step of mounting a solder bump on the through hole to which the solder bonding material is supplied, and a step of heating the substrate to solder in the solder bump and the solder bonding material. Melting the particles to structurally integrate the solder bumps and the solder particles and solder-bond them to the surface of the circuit electrode.

According to the invention described in each of the claims, the solder joint containing the solder particles having a size capable of simultaneously contacting both the solder ball or the solder bump and the surface of the circuit electrode is provided in the through hole formed on the circuit electrode. By supplying the material, the solder particles serve as a bridge connecting the solder ball or the solder bump and the circuit electrode surface in the heating process, and the molten solder can be prevented from separating.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION (Embodiment 1) FIG.
(B), (c), (d), (e) is a process explanatory view of the solder bump forming method of the first embodiment of the present invention, showing the solder bump forming method in the order of processes. Figure 1 (a)
In, the insulating substrate 11 is made of an insulating material such as polyimide tape or glass epoxy resin, and the circuit electrode 12 is formed on the insulating substrate 11. Circuit electrode 12 of insulating substrate 11
Through holes 13 are provided at positions corresponding to. The through holes 13 are for forming solder bumps on the surface of the insulating substrate 11 opposite to the circuit electrodes 12.

As shown in FIG. 1B, cream solder 14 is supplied into the through hole 13. The cream solder 14 is a mixture of solder particles 14a and flux. The particle size of the solder particles 14a is such that the solder balls 14 are provided on both the solder balls and the surface of the circuit electrode 12 when the solder balls are mounted on the through holes 13 to which the cream solder 14 is supplied.
The size is set so that at least one of a is in contact with at the same time. That is, the example of the present embodiment (75 μ
through hole 13 with a diameter of 200 μm in insulating substrate 11 with a thickness of m
In an example in which a solder ball having a diameter of 300 μm is mounted thereon, the solder paste having a particle diameter of 40 μm to 70 μm in a volume ratio of 5 to 30% (preferably 20%) is contained in the cream solder 14 To use.

Next, as shown in FIG. 1C, solder balls 15 are mounted on the through holes 13 to which the cream solder 14 is supplied. At this time, since the solder particles 14a having the particle size as described above are included, at least one of the solder particles 14a in the cream solder 14 is the solder ball 15
And both surfaces of the circuit electrode 12 are simultaneously in contact with each other.

After that, the insulating substrate 11 is sent to a reflow process and heated. This causes the solder particles 14a and the solder balls 15 to start melting. At this time, the solder particles 14a
Of the solder balls 15 and the surfaces of the circuit electrodes 12, the solder particles 14a that are in contact with each other are melted together with the solder balls 15 to melt the solder balls 15 as shown in FIG. , The molten solder 14'a in which the solder particles 14a are melted quickly to the circuit electrode 1
2 It is fixed on the surface. Since the wettability between the solders and between the solder and the surface of the circuit electrode 12 is good, the molten solder 1
This is because 4'is immediately integrated with the molten solder 15 'and also fused to the surface of the circuit electrode 12.

Therefore, in the heating process, the solder particles 14a in the cream solder 14 are not melted and separated vertically into the solder ball 15 side and the circuit electrode 12 side, and the molten solder 15 'of the solder ball 15 is the cream solder 14'. It surely integrates with the molten solder 14a 'of the solder particles inside. After the molten solder is solidified, the solder bumps 16 are formed on the circuit electrodes 12 by soldering, as shown in FIG.

(Embodiment 2) FIGS. 2 (a), 2 (b),
(C), (d), (e) is process explanatory drawing of the mounting method of the solder bump of Embodiment 2 of this invention, and has shown the mounting method of a solder bump in process order.

In FIG. 2A, the circuit electrode 22 is formed on the surface of the substrate 21. A solder resist 23 as an insulating film made of epoxy or acrylic resin is formed so as to cover the substrate 21 and the circuit electrodes 22. At the position corresponding to the circuit electrode 22 of the solder resist 23,
A through hole 24 is provided. Here, the diameter of the through hole 24 is smaller than the diameter of the solder bump mounted on the through hole 24. Next, as shown in FIG.
Cream solder 25 is supplied into the through holes 24. Cream solder 25 is similar to cream solder 14 in the first embodiment.

Next, as shown in FIG. 2C, an electronic component 27 having spherical solder bumps 26 formed thereon is mounted on the substrate 21. After this, the substrate 21 is sent to the reflow process and heated. As a result, the solder particles in the cream solder 25 and the solder bumps 26 start melting, but at this time, the first embodiment
Similarly, among the solder particles in the cream solder 25, the solder particles in contact with both the solder bumps 26 and the surface of the circuit electrode 22 are melted, so that the solder bumps 26 are formed as shown in FIG. 2D. The molten molten solder 26 'is the circuit electrode 2
2 It is fixed on the surface. Therefore, in the heating process, the solder particles in the cream solder 25 are not separated into upper and lower parts, and after the molten solder is solidified, the solder bumps 26 are surely mounted on the circuit electrodes 22 by soldering as shown in FIG. To be done.

[0020]

According to the present invention, there is provided a solder bonding material containing solder particles having a size such that the through holes formed on the circuit electrodes simultaneously contact both the solder balls or the solder bumps and the surface of the circuit electrodes. In the heating process, the solder particles play a role of a bridge that connects the solder balls or solder bumps to the circuit electrode surface, and prevent the molten solder from being separated into upper and lower parts to reliably form the solder bumps. Alternatively, solder bumps can be mounted.

[Brief description of drawings]

1A is a process explanatory diagram of a solder bump forming method according to a first embodiment of the present invention. FIG. 1B is a process explanatory diagram of a solder bump forming method according to a first embodiment of the present invention. Process explanatory drawing of the solder bump formation method of Embodiment 1 (d) Process explanatory drawing of the solder bump formation method of Embodiment 1 of this invention (e) Solder bump formation method of Embodiment 1 of this invention Process explanatory drawing of

FIG. 2A is a process explanatory view of a solder bump mounting method according to a second embodiment of the present invention. FIG. 2B is a process explanatory view of a solder bump mounting method according to a second embodiment of the present invention. Process explanatory drawing of the solder bump mounting method of Embodiment 2 (d) Process explanatory drawing of the solder bump mounting method of Embodiment 2 of this invention (e) Solder bump mounting method of Embodiment 2 of this invention Process explanatory drawing of

FIG. 3A is a partial cross-sectional view of a conventional tape-shaped substrate. (B) Partial cross-sectional view of a conventional tape-shaped substrate (C) Partial cross-sectional view of a conventional tape-shaped substrate

[Explanation of symbols]

1, 11 Insulation board 2, 12, 22 circuit electrodes 3, 13, 24 through holes 4,14,25 Cream solder 14a Solder particles 5,15 solder balls 15 ', 26' molten solder 16, 26 Solder bump 21 board

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Claims (2)

(57) [Claims] 1. A method of forming a solder bump, comprising solder-bonding a solder ball to a circuit electrode through a through hole provided in an insulating substrate to form a solder bump on the surface of the insulating substrate opposite to the circuit electrode. In the through hole provided with a diameter smaller than that of the solder ball, solder particles having a size that simultaneously contacts both the solder ball and the surface of the circuit electrode when the solder ball is mounted on the through hole. A step of supplying the solder bonding material containing the solder ball, a step of mounting a solder ball on the through hole to which the solder bonding material is supplied, a step of heating the insulating substrate, and solder particles in the solder ball and the solder bonding material. A step of melting the solder balls and the solder particles structurally so as to be joined to the surface of the circuit electrode by soldering. 2. A solder bump in which a solder bump formed on an electronic component is solder-bonded to the circuit electrode through a through hole provided in an insulating film covering the circuit electrode of the substrate to mount the solder bump on the substrate. A mounting method, in which the solder bump and the surface of the circuit electrode are simultaneously contacted in the through hole provided with a diameter smaller than that of the solder bump, with the solder bump mounted on the through hole. Supplying a solder bonding material containing solder particles of a size; mounting a solder bump on the through hole to which the solder bonding material is supplied; heating the substrate; By melting the solder particles in the bonding material,
A method of mounting a solder bump, comprising the step of structurally integrating the solder bump and solder particles and solder-bonding to the surface of the circuit electrode.