JPH1032222A - Manufacture of electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to form solder balls of a good appearance without making the manufacturing cost of the solder balls remarkedly high. SOLUTION: Flux 3 is applied to a land part 2 formed on the major surface 1a on the opposite side to the surface, which is mounted with a chip component, of a substrate 1 to place solder balls 4 on the flux 3, atomized flux 8 is sprayed on the balls 4 from the side of the upper surfaces of the balls 4 to coat the flux 8 also on the side of the upper surfaces of the balls 4 and after this, the balls 4 are molten and are made to solidify to make the balls 4 secure on the land part 2. Moreover, a screen 6 having open parts at positions, where correspond to the solder ball placement positions on the flux 3, is arranged on the side of the upper surfaces of the balls 4 and the atomized flux 8 may be sprayed in such a way that it is sprayed via this screen 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electronic component, such as a ball grid array, in which solder balls serving as connection terminals with the outside are formed on one principal surface of a substrate. More specifically, it relates to a method of manufacturing an electronic component in which a solder ball is formed with a good appearance by applying a flux to the upper surface side of the solder ball to prevent oxidation of the solder ball surface when the solder ball is melted and solidified. is there.

[0002]

2. Description of the Related Art In various printed wiring boards on which various chip components such as IC packages are mounted, high-density mounting of chip components has been promoted due to rapid development of surface mounting technology. Thus, although the miniaturization of IC packages and the like are being promoted, it is difficult to achieve higher-density mounting than at present. On the other hand, in recent years, so-called bare chip mounting, in which an IC chip is taken out of an IC package and directly mounted on a printed wiring board, is being studied.

As a method for performing the above-described bare chip mounting, for example, a ball grid array system (hereinafter, referred to as a BGA system) can be cited. BGA above
In the method, a substrate on which printed wiring is formed is disposed on the side of the printed circuit board opposite to the printed circuit board, which is referred to as a mother board, in the IC chip which is a bare chip, and connected to the terminal portion of the IC chip on the side of the printed circuit board opposite to the substrate. As well as
A ball grid array type electronic component (hereinafter, referred to as BGA) having a second land portion to be a connection terminal with the outside and a solder ball mounted on the second land portion is prepared. The solder balls are melted and solidified to connect the land portions of the BGA to the land portions of a printed wiring board called a motherboard, and the BGA is mounted on the printed wiring board. That is, the above BGA
In, the solder ball functions as a substantial external connection terminal.

In the BGA substrate, a first land corresponding to the terminal of the IC chip and connected thereto is formed on one main surface, and the first land is formed on the opposing main surface. And a second land portion connected to the land portion by a wiring circuit pattern is formed.
By connecting the terminals of the chip, the terminals of the IC chip and the second lands are connected.
That is, in the BGA method, the terminal portion of the IC chip is drawn out to the outside via the substrate, and the formation position of the second land portion serving as a connection terminal with the outside can be determined relatively freely. is there.

[0005]

The above-mentioned BGA
Is manufactured through the following steps. That is, first, a substrate which is a printed wiring board having the first and second lands formed on the opposing main surfaces as described above is prepared. Subsequently, a chip component such as an IC chip, which is a bare chip, is mounted on the main surface on the side where the first land portion is formed.

Next, a flux is applied on the second land portion of the substrate by printing or potting. Next, a solder ball is placed on the second land portion to which the flux has been applied. Then, the substrate is subjected to a heat treatment called reflow, and the heat causes the solder balls on the second lands to melt appropriately. further,
The substrate is cooled to solidify the solder balls and fix the solder balls on the second lands, thereby completing the BGA.

However, when an electronic component having a solder ball formed thereon as a connection terminal with the outside, such as a BGA, is manufactured, there is a disadvantage that the appearance of the solder ball is not good. This is because no flux is contained in the solder ball, and the surface of the solder ball is significantly oxidized by air in the atmosphere during reflow.

To solve this inconvenience, it has been proposed to use silver-containing solder balls as solder balls and to perform reflow in a nitrogen atmosphere.
Silver-containing solder balls are more expensive than commonly used eutectic solder balls, and reflow devices that can reflow in a nitrogen atmosphere have higher running costs. It is expensive and not preferred.

Accordingly, the present invention has been proposed in view of the conventional circumstances, and provides a method of manufacturing an electronic component which enables formation of a solder ball having a good appearance without significantly increasing the manufacturing cost. The purpose is to do.

[0010]

In order to achieve the above-mentioned object, a method of manufacturing an electronic component according to the present invention is directed to a method of manufacturing an electronic component on a land portion formed on a main surface of a substrate opposite to a surface on which chip components are mounted. Apply flux to the solder ball, place the solder ball on it, spray the mist flux from the top side of the solder ball, apply the flux to the top side of the solder ball, and then melt and solidify the solder ball on the land. It is characterized by being fixed.

In the method of manufacturing an electronic component according to the present invention, a screen having an opening at a position corresponding to the solder ball mounting position is arranged on the upper surface side of the solder ball, and a mist-like flux is passed through the screen. May be sprayed.

In the method for manufacturing an electronic component according to the present invention,
Since the flux is also applied to the upper surface side of the solder ball, the surface of the solder ball is protected by the flux, and the surface of the solder ball is not remarkably oxidized at the time of reflow, so that the solder ball has a good appearance.

Further, since the application is performed by spraying a mist-like flux on the upper surface side of the solder ball, no careless force is applied to the solder ball, and the solder ball may be displaced. Absent.

Further, if the mist-like flux is sprayed through a screen having an opening at a position corresponding to the solder ball mounting position, the flux can be applied only to the upper surface of the solder ball. It is possible.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

In the method of manufacturing an electronic component according to the present embodiment, first, a wiring circuit pattern including a first land portion serving as a connection portion with a chip component which is a bare chip such as an IC chip is formed on one main surface, A substrate which is a printed wiring board on which a wiring circuit pattern including a second land portion which is electrically connected to the first land portion and serves as a terminal on the other main surface is formed is prepared. Then, the first land portion of the substrate is electrically connected to the terminal of the chip component, and
The chip component is mounted on the side of the land portion forming surface.

Next, as shown in FIG. 1, a flux 3 is applied by a method such as printing or potting on the second land portion 2 on one main surface 1a opposite to the chip component mounting surface of the substrate 1. Apply. Subsequently, the solder balls 4 are placed on the flux 3. At this time, solder balls 4
Is a state temporarily fixed by the flux 3.

Next, a screen 6 having an opening 5 at a position corresponding to the mounting position of the solder ball 4 on the substrate 1 as shown in FIG. 2 is prepared. Then, as shown in FIG. 3, the screen 6 shown in FIG.
Are arranged in a state where the openings 5 and the solder balls 4 are aligned. At this time, the screen 6 is moved so that the position of the solder ball 4 does not shift due to the contact with the screen 6.
Is preferably arranged slightly away from the solder ball 4.

Subsequently, as shown in FIG.
The atomizing flux 8 is sprayed by the spray nozzle 7 from the one main surface 6a side opposite to the solder ball facing surface.
That is, the mist-like flux 8 is sprayed through the screen 6, and the mist-like flux 8 can pass through the screen 6 only at the opening 5 of the screen 6. Needless to say, the spray nozzle 7 is connected to a flux supply device or the like (not shown). Since the opening 5 is formed at a position corresponding to the solder ball 4 placement position, the flux 8 is applied only to the upper surface side of the solder ball 4 as shown in FIG.

Next, reflow is performed on the substrate 1 on which the solder balls 4 are mounted, and after the solder balls 4 are appropriately melted, cooled and solidified.
Is fixed on the second land portion 2 to complete the electronic component.

In the method of manufacturing an electronic component according to the present embodiment, since the flux 8 is also applied to the upper surface side of the solder ball 4, the surface of the solder ball 4 is protected by the flux 8, and the surface of the solder ball 4 is remarkably reflowed. The solder ball 4 is not oxidized and the second land 2
Thus, it is possible to obtain an electronic component in which the solder balls are fixed in a good appearance and the solder balls are formed in a good appearance.

In the method of manufacturing an electronic component according to the present embodiment, since solder balls 4 are prevented from being oxidized during reflow, silver-containing solder balls are used as solder balls 4 or reflow is performed in a nitrogen atmosphere. Eutectic solder balls that are commonly used as solder balls 4 can be used for reflow in the air, and devices such as screen 6 and spray nozzle 7 are relatively inexpensive. In addition, the manufacturing cost is not significantly increased.

Further, in the method of manufacturing an electronic component according to the present embodiment, since the mist-like flux 8 is sprayed through the screen 6 having the opening 5 at a position corresponding to the mounting position of the solder ball 4, It is possible to apply the flux 8 only to the upper surface of the ball 4, and it is possible to cope with the manufacture of an electronic component having a small interval between solder balls.

Furthermore, in the method of manufacturing an electronic component according to the present embodiment, the application is performed by spraying the mist-like flux 8 and the screen 6 is disposed at a position slightly away from the solder ball 4. In addition, it is possible to obtain an electronic component on which the solder balls 4 are formed with good positional accuracy without applying an inadvertent force to the solder balls 4 and without causing a displacement or the like of the solder balls 4.

In the above-described example of the method of manufacturing an electronic component, the example in which the mist-like flux is sprayed through the screen has been described. However, a plurality of solder balls are arranged as the electronic component at a sufficient interval. When there is no possibility that an electrical connection (bridge) between the solder balls occurs during reflow, a mist-like flux may be sprayed without passing through a screen.

[0026]

As is clear from the above description, in the method for manufacturing an electronic component of the present invention, since the flux is applied also to the upper surface side of the solder ball, the surface of the solder ball is protected by this flux, The surface of the solder ball is not significantly oxidized during reflow, and the solder ball is formed with a good appearance.

In the method of manufacturing an electronic component according to the present invention, since the solder balls are prevented from being oxidized during reflow, silver-containing solder balls are used as the solder balls or the reflow is performed in a nitrogen atmosphere. There is no need to use a eutectic solder ball that is usually used as a solder ball, and it is possible to reflow in air, so that the manufacturing cost is not significantly increased.

Furthermore, since the application is performed by spraying the mist-like flux on the upper surface side of the solder ball, no careless force is applied to the solder ball, and the solder ball may be displaced. In addition, it is possible to obtain an electronic component on which solder balls are formed with good positional accuracy.

Furthermore, if the mist-like flux is sprayed through a screen having an opening at a position corresponding to the solder ball mounting position, the flux can be applied only to the upper surface of the solder ball. It is possible to cope with the manufacture of an electronic component having a small interval between solder balls.

[Brief description of the drawings]

FIG. 1 is a fragmentary enlarged cross-sectional view showing a method of manufacturing an electronic component to which the present invention is applied in the order of steps, showing a step of applying a flux on a second land portion and mounting a solder ball. .

FIG. 2 is a perspective view illustrating a method of manufacturing an electronic component to which the present invention is applied in the order of steps, and illustrating a step of preparing a screen.

FIG. 3 is a fragmentary enlarged cross-sectional view showing a method of manufacturing an electronic component to which the present invention is applied, in the order of steps, showing a step of arranging a screen on a solder ball upper surface side;

FIG. 4 is a fragmentary enlarged cross-sectional view showing a method of manufacturing an electronic component to which the present invention is applied in the order of steps, showing a step of spraying a mist-like flux through a screen.

FIG. 5 is a fragmentary enlarged cross-sectional view showing a method of manufacturing an electronic component to which the present invention is applied, in the order of steps, showing a state where a flux is applied only to the upper surface side of a solder ball.

[Explanation of symbols]

1 substrate, 1a, 6a one main surface, 2nd land part,
3,8 flux, 4 solder ball, 5 opening,
6 screen

Claims (2)

[Claims] 1. A flux is applied to a land portion formed on a main surface of a substrate opposite to a surface on which chip components are mounted, and a solder ball is placed thereon. A flux is also applied to the upper surface side of the solder ball by spraying, and thereafter, the solder ball is melted and solidified to be fixed on the land portion. 2. A screen having an opening at a position corresponding to a solder ball mounting position on an upper surface side of a solder ball, and spraying mist-like flux through the screen. A method for producing the electronic component described in the above.