JPH0629143A - Method for forming bump of layered electronic parts - Google Patents

Abstract

PURPOSE:To obtain a method for forming a bump on layered electronic parts easily and positively without changing a conventional bump-manufacturing process greatly. CONSTITUTION:A ceramic sheet 5 where an external electrode 6 of a metal without any wetting property for solder is printed at both edges is stacked on a ceramic sheet 3 and the outermost layer of an internal electrode 4 and the entire part is calcined. Thin, a lower electrode 12 is connected to the external electrode 6 for interlocking to the internal electrode 4 and at the same time a bump electrode 11 with wetting property for solder is printed at the external electrode 6 while being matched to the bump-mounting position and then bump is piled up on the bump electrode 11, thus forming a bump 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bump forming method for mounting a bump on a laminated electronic component such as a laminated capacitor.

[0002]

2. Description of the Related Art In recent years, there has been a demand for downsizing of electronic devices. In order to achieve downsizing of the electronic devices, electronic parts used inside are downsized, and at the same time, a large number of electronic parts are formed on a substrate having a certain area. It has been desired to implement high-density packaging that incorporates as much as possible. As one method for realizing such high density mounting of electronic components, a mounting method of electronic components using bumps is known.

For example, when bumps are formed on a multilayer capacitor in which electrodes and dielectrics are laminated, metal is attached to both end surfaces where internal electrodes are exposed to connect individual internal electrodes, and this metal is used for this multilayer capacitor. It was extended to the lower surface of and the bump was provided there.

More specifically, first, Ag / Pb or the like is baked on both sides of the multilayer capacitor to form a lower electrode, Ni or the like is attached on the lower electrode by plating to form an intermediate electrode, and then solder is further plated. Then, the external electrodes are formed and the bumps are provided there.

[0005]

As described above, since the metal has to be attached to the end face, the lower face and the upper face of the capacitor, the capacitor is usually placed in the molten metal with the end face facing downward. , It was done until the metal adhered to the bottom surface of the capacitor. Therefore, when the capacitor is pulled up, the metal attached to the periphery of the capacitor accumulates downward due to its own weight or is rounded by the surface tension, and the surface of the formed electrode inclines with respect to the lower surface of the capacitor. When attaching a bump to an electrode, it could be very difficult to attach. Moreover, in order to form the bumps, it is troublesome because the insulating resist must be applied to the parts other than the bump mounting positions. In addition, the size of the capacitor itself is very small, which makes it difficult to handle and the manufacturing cost is low. Was rising.

Further, it is known that instead of providing a metal on the side surface, a through hole is formed to connect the individual internal electrodes. In order to form this through hole, each electrode is formed by drilling after laminating. There is a problem in that it is necessary to form a through hole and to apply a metal to the inner surface of this hole, which requires time and labor for manufacturing.

It is an object of the present invention to provide a method of utilizing a conventional bump forming process of a laminated electronic component without making a great change, and easily and surely forming a bump on the laminated electronic component. To do.

[0008]

In order to solve the above problems, therefore, in the present invention, a metal having no wettability with respect to solder is printed on both ends of the ceramic sheet before laminating, so that the internal electrodes and the ceramics are not printed. After sequentially laminating the sheets, the ceramic sheet is laminated on the outer surface of the electronic component. Thereafter, this ceramic sheet is fired together with the internal electrodes to form external electrodes by firing the printed metal on the outer surface of the laminated electronic component. Next, a metal having solder wettability is printed on the external electrodes thus formed at the bump mounting locations to provide bump electrodes, and solder is placed on the bump electrodes to form bumps.
The internal electrode and the external electrode are electrically connected separately.

[0009]

Since the external electrodes are formed by directly printing on the surface of the ceramic sheet and firing, the surface is formed flat after firing and the electrodes for bumps can be easily printed on the surface. Since the external electrodes do not have wettability with respect to the bumps, bump solder can be placed only on the bump electrodes to form the bumps easily and reliably.

[0010]

Embodiments of the bump forming method according to the present invention will be described below with reference to the drawings.

FIG. 1 shows an exploded view of the capacitor 2. (In the figure, the upper and lower sides are turned upside down for convenience of description.) The ceramic sheet 3 is made of a dielectric ceramic such as barium titanate, and the internal electrodes 4 are formed on the surface of the ceramic sheet 3. The internal electrodes 4 are formed by printing a silver-based or copper-based metal, are printed on the ceramic sheet 3 alternately for each electrode, and are extended to different ends for each electrode, and the ceramic sheets 3 are laminated. Then, the end of the internal electrode 4 is exposed on the end face of the capacitor 2. The ceramic sheet 3 and the internal electrode 4 are sequentially laminated, and the ceramic sheet 5 having both ends coated with tungsten 7 by printing is superposed on the lowermost layer.

When the ceramic sheet 3, the internal electrodes 4 and the ceramic sheet 5 are laminated in this way and then the whole is fired, the capacitor 2 is formed and wettability to the solder made of tungsten 7 at both ends of the ceramic sheet 5 is obtained. The external electrode 6 which is not formed is formed.

Next, as shown in FIG. 2, bump electrodes 11 are printed on the surface of each external electrode 6 at two locations on each of the external electrodes 6 at both ends. The bump electrode 11 is printed using silver, which has wettability with respect to solder. And further capacitor 2
The lower electrodes 12 are connected to the external electrodes 6 on the respective sides and attached to both sides of the external electrodes 6. The lower electrode 12 has only to have conductivity, and the kind of metal is not particularly limited. Next, solder is applied to the bump electrodes 11 to form the bump 1
0 is formed at four places as shown in FIG. FIG. 4 shows a state in which the capacitor 2 is mounted on the substrate 20 via the bump 10.

Therefore, according to the forming method of this embodiment, since the external electrodes 6 for mounting the bumps 10 are formed by printing and subsequent firing, the surface can be made flat,
Moreover, since it has no wettability with respect to solder, it is not necessary to newly apply a resist, and the bumps can be easily and reliably formed on the capacitor 2 without significantly changing the conventional bump attaching apparatus.

Although the external electrode 6 is formed of tungsten 7 in this embodiment, the external electrode 6 is not required to be wettable by solder in the present invention, and other metal such as chromium may be used. Further, the bump electrode 11 is formed by printing using silver, but similarly, the bump electrode 11 only needs to have wettability with respect to solder, and in addition to silver, gold, copper, an alloy of silver and lead, or the like may be used. Alternatively, the forming means may be performed by another method such as vapor deposition.

Furthermore, the present invention is not limited to capacitors, but can be applied as a forming method for mounting bumps on the surface of electronic components manufactured by laminating multilayer substrates such as multilayer substrates.

[0017]

As described above, according to the bump forming method of the present invention, a metal having no solder wettability is printed on the ceramic sheet which is the outer surface of the laminated component before firing, and the metal is fired. Since the bump mounting surface is formed on the external electrode with high flatness, the bump mounting electrode is printed on the external electrode with a metal having good solder wettability, and the bump mounting surface is flat. It is possible to provide an effective bump forming method that can be made highly expensive, that the bumps can be easily and surely attached, and that the apparatus used for forming the conventional bumps can be used without making a great change, and that the bump forming method is very mass producible.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a capacitor for explaining a bump forming method according to the present invention.

FIG. 2 is an exploded perspective view of a capacitor for explaining a bump forming method according to the present invention.

FIG. 3 is a perspective view of a capacitor according to the present invention.

FIG. 4 is a front view showing a state in which a capacitor according to the present invention is mounted on a substrate.

[Explanation of symbols]

 2 Capacitor 3 Ceramic Sheet 4 Internal Electrode 5 Ceramic Sheet 6 External Electrode 10 Bump 11 Bump Electrode

Claims (2)

[Claims] 1. A metal having a low solder wettability is applied to both ends of an upper surface or a lower surface of a laminated electronic component, which is baked to form an external electrode, and a metal having a good solder wettability is bumped on the external electrode. A bump forming method for a laminated electronic component, comprising applying a molten solder to an attachment position to the external electrode to attach the solder to the bump attachment position to form a bump on the laminated electronic component. 2. The multilayer electronic component according to claim 1, which is a multilayer capacitor, wherein the internal electrode of the multilayer capacitor is integrally connected by providing a lower electrode on a side surface of the multilayer capacitor and the lower electrode and the external electrode. Forming a bump of a multilayer capacitor.