JPH11298132A - Method for forming and mounting solder bump, and solder junction structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a solder bump together with a method for mounting a solder bump of high junction reliability. SOLUTION: A solder ball 15 is solder-jointed to a circuit electrode 12 through a through hole 13 provided at an insulating substrate 11, so that a solder bump is formed on the surface opposite to the circuit electrode 12 of the insulating substrate 11, related to a method for forming a solder bump. Here, the solder ball 15 is mounted on the through hole 13 provided as a diameter smaller than the solder ball 15, and the solder ball 15 is pressurized against the substrate 11 so that the upper end surface of the through hole 13 is crushed for beveling. Then the insulating substrate 11 is heated to melt the solder ball 15, for solder joint to the circuit electrode 12. Thus, a notch in the solder joint part is eliminated for preventing concentration of stress, thus reliability at the solder junction after mounting is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

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

[0003] 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 are not the same surface of the substrate. That is, circuit electrodes are formed on one surface of a tape-shaped substrate constituting a package, and solder balls are mounted on the opposite side of the surface on which the circuit electrodes are formed. Then, the solder ball is melted, and the molten solder is conducted to the circuit electrode through a through hole of the substrate provided at the position of the circuit electrode to form a solder bump.

A conventional solder bump forming method in such a case will be described below with reference to the drawings. FIG.
(A), (b), (c) is a partial sectional view of a conventional tape-shaped substrate. In FIG. 3A, a circuit electrode 2 is formed on a lower surface of a tape-shaped insulating substrate 1. Insulating substrate 1
A through hole 3 is provided at the position of the circuit electrode 2. The through-hole 3 is provided by punching from the lower side to the upper side in the figure, and burrs B are generated at the edge of the upper end face by the punching.

[0005] A flux 4 is applied in the through hole 3, and then, as shown in FIG. 3 (b), a solder bump is formed in the through hole 3 to form a solder bump on the circuit electrode 2.
Is mounted. Thereafter, the insulating substrate 1 is sent to reflow and heated, so that the solder balls 5 are melted and the molten solder 5 ′ is melted.
Fills the through hole 3 and is soldered to the circuit electrode 2.

[0006]

At this time, the molten solder 5 '
Protrudes to the upper surface of the insulating substrate 1 and covers the upper end surface of the through-hole 3. Here, since the burrs B are present at the edge of the upper end surface of the through-hole 3, the molten solder 5 'is solidified after the solidification. A sharp notch N is formed in the portion of the burr B. The presence of the notch N causes concentration of stress in this portion, and reduces the repetitive strength of the solder bump. Then, it becomes a cause of breakage of the solder joint due to a heat cycle after mounting, and significantly reduces the reliability of the solder joint.

However, in the above-described conventional method for forming a solder bump, it is difficult to effectively prevent the occurrence of the notch portion N, so that the above serious defect cannot be prevented, and a solder bump having high bonding reliability can be formed. There was a problem that it was difficult to do. In addition, the above problem occurs when a spherical solder bump is mounted on a circuit electrode of a substrate, that is, when a through hole is provided in a resist covering the circuit electrode, and the solder bump is mounted on the circuit electrode through the through hole. Was also common.

Accordingly, an object of the present invention is to provide a method for forming a solder bump having high bonding reliability, a method for mounting a solder bump, and a solder bonding structure having high bonding reliability.

[0009]

According to a first aspect of the present invention, there is provided a method of forming a solder bump, comprising: soldering a solder ball to a circuit electrode via a through hole provided in an insulating substrate; A method of forming a solder bump on a surface, wherein a step of crushing an upper end edge of the through hole by pressing the solder ball into the through hole provided with a smaller diameter than the solder ball; Heating the substrate to melt the solder balls and solder-join the circuit electrodes.

According to a second aspect of the present invention, there is provided a method for mounting a solder bump.
A solder bump mounting method of soldering a solder bump formed on an electronic component to the circuit electrode via a through hole provided in an insulating film covering a circuit electrode of the board, and mounting the solder bump on the board. Pressing the solder bumps into the through holes provided with a smaller diameter than the solder bumps to crush the upper edges of the through holes with the solder bumps, and heating the substrate to melt the solder bumps. And soldering to the circuit electrode.

According to a third aspect of the present invention, there is provided a solder joint structure formed by joining a spherical solder portion to the circuit electrode through a through hole provided in an insulating film covering the circuit electrode. Therefore, the step of forming the solder joint structure,
Pressing the solder portion into the through hole provided with a smaller diameter than the solder portion to crush the upper end edge of the through hole with the solder portion; and melting the solder portion and soldering to the circuit electrode. And included.

According to the present invention, the upper end of the through-hole is pressed by pressing the solder ball or the solder bump into the through-hole provided in the insulating substrate or the insulating film for solder-joining the solder ball or the solder bump. By crushing the edge, the notch in the solder joint is eliminated, preventing the occurrence of stress concentration,
The reliability of the solder joint after mounting can be improved.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG.
(B), (c), (d), and (e) are process explanatory views of the method of forming a solder bump according to the first embodiment of the present invention, and show the method of forming a solder bump in the order of processes. FIG. 1 (a)
In the above, the insulating substrate 11 as an insulating film has
Are formed. The through holes 13 are provided corresponding to the positions of the circuit electrodes 12 formed on the lower surface of the insulating substrate 11, and are for forming solder bumps as solder portions on the surface of the insulating substrate 11 opposite to the circuit electrodes 12. . Here the through hole 1
The diameter of 3 is set smaller than the diameter of a solder ball mounted for bump formation. Since the through-hole 13 has been punched, burrs B are formed on the upper end surface.

Next, as shown in FIG.
The cream solder 14 is supplied therein. Cream solder 14
Is obtained by mixing solder particles in a flux containing a solvent component. Next, as shown in FIG. 1C, the solder balls 15 are mounted on the through holes 14 to which the cream solder 14 is supplied by the ball mounting means. FIG. 1 (b), (c)
Shows a suction tool 16 as an example of the ball mounting means. As described above, the diameter of the solder ball 15 is
Is larger than the diameter, the solder ball 15 enters the through hole 13 and does not contact the electrode 12, but is placed in a state of contacting the upper end surface of the through hole 13. After the mounting operation, the solder balls 15 are pressed against the insulating substrate 11 with a predetermined load by the ball mounting means for a predetermined time. Thereby, as shown in FIG. 1D, the upper end surface of the through hole 13 is crushed by the pressing force of the solder ball 15, and the burr B on the upper end surface generated at the time of punching the through hole 13 disappears.

Thereafter, the insulating substrate 11 is sent to a reflow step and heated. As a result, as shown in FIG. 1E, the solder balls 15 and the cream solder 14 are melted, and the molten solders 14 ′ and 15 ′ fill the inside of the through-hole 13, and a part of them protrudes onto the insulating substrate 11. At this time, since the upper end surface of the through hole 13 is crushed by the above-described pressing, a sharp notch is not formed in the upper end surface of the through hole 13 after the molten solder 15 ′ is solidified. It is possible to form a highly reliable solder bump without inviting. Although the pressing step is performed after the mounting step in the present embodiment, the solder ball 15 may be pressed against the insulating substrate 11 by the suction tool 16 at the same time as the mounting.

(Embodiment 2) FIGS. 2 (a), (b),
(C), (d), and (e) are process explanatory diagrams of the solder bump mounting method according to the second embodiment of the present invention, and show the solder bump mounting method in the order of processes. In FIG. 2A, a circuit electrode 22 is formed on the surface of a substrate 21. A solder resist 23 as an insulating film made of a resin material such as epoxy or acrylic is formed so as to cover the substrate 21 and the circuit electrodes 22. Solder resist 2
A through hole 24 is provided at a position corresponding to the third circuit electrode 22. Here, the diameter of the through hole 24 is smaller than the diameter of the solder bump to be mounted.
The upper end face of 4 has a sharp edge portion.

Next, as shown in FIG.
4, cream solder 25 is supplied.
As shown in (c), an electronic component 27 on which a spherical solder bump 26 as a solder portion is formed is mounted on a substrate 21 by mounting means. FIG. 2B shows a nozzle 28 as an example of the mounting means. As described above, the solder bump 26
Is larger than the diameter of the through-hole 24, and therefore the solder bump 26 does not enter the inside of the through-hole 24 and is placed in a state of contacting the upper end surface of the through-hole 24. After the mounting operation, the mounting means presses the electronic component 27 against the substrate 21 with a predetermined load for a predetermined time. As a result, FIG.
As shown in (d), the upper end surface of the through hole 24 is crushed by the pressing force of the solder bump 26, and the sharp edge of the upper end surface of the through hole 24 disappears.

Thereafter, the substrate 21 is sent to a reflow process,
Heated. As a result, the cream solder 25 and the solder bump 26 melt as shown in FIG. At this time, since the upper end surface of the through hole 24 is chamfered by the above-described pressing, a sharp notch is not formed in the upper end surface of the through hole 24 after the molten solder is solidified. A highly reliable solder joint that does not cause stress concentration can be formed. In the present embodiment, the pressing step is performed after the mounting step. However, the electronic component 27 may be pressed against the through hole 24 simultaneously with the mounting.

[0019]

According to the present invention, a through hole provided in an insulating film for solder-joining a solder ball or a solder bump is formed.
Solder balls and solder bumps are pressed to crush the top edge of the through-hole and then solder-bonded, so burrs on the top surface and notches in the solder-bonded portion due to edges can be eliminated, and therefore the solder-bonded portion This prevents the occurrence of stress concentration in the solder joint, thereby improving the reliability of the solder joint after mounting.

[Brief description of the drawings]

FIG. 1A is a process explanatory view of a solder bump forming method according to a first embodiment of the present invention. FIG. 1B is a process explanatory view of a solder bump forming method according to a first embodiment of the present invention. Process description diagram of the solder bump forming method of the first embodiment (d) Process description diagram of the solder bump forming method of the first embodiment of the present invention (e) Method of forming the solder bump of the first embodiment of the present invention Process description diagram

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 description diagram of solder bump mounting method according to Embodiment 2 (d) Process description diagram of solder bump mounting method according to Embodiment 2 of the present invention (e) Method of mounting solder bump according to Embodiment 2 of the present invention Process description diagram

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11 Insulating board 2, 12, 22 Circuit electrode 3, 13, 24 Through-hole 4, 14, 25 Cream solder 5, 15 Solder ball 21 Substrate 23 Solder resist 26 Solder bump 27 Electronic component

Claims (3)

[Claims] 1. A method of forming a solder bump, comprising: soldering a solder ball to a circuit electrode via a through hole provided in an insulating substrate to form a solder bump on a surface of the insulating substrate opposite to the circuit electrode; Pressing the solder ball into the through-hole provided with a smaller diameter than the solder ball to crush the upper edge of the through-hole; and heating the insulating substrate to melt the solder ball and to form the circuit electrode. And a solder bonding step. 2. A solder bump, wherein a solder bump formed on an electronic component is solder-bonded to the circuit electrode via a through-hole provided in an insulating film covering the circuit electrode on the board, and the solder bump is mounted on the board. The mounting method, wherein pressing the solder bumps into the through holes provided with a smaller diameter than the solder bumps to crush the upper edge of the through holes with the solder bumps, and heating the substrate to heat the substrate. Melting the solder bumps and joining them to the circuit electrodes by soldering. 3. A solder joint structure formed by soldering a spherical solder portion to the circuit electrode via a through hole provided in an insulating film covering the circuit electrode, wherein the solder joint structure is formed. Pressing the solder portion into the through hole provided with a smaller diameter than the solder portion to crush the upper end edge of the through hole with the solder portion; and melting the solder portion and soldering the circuit electrode. And a joining step.