JP3277389B2 - Bump forming method for laminated electronic components - Google Patents

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 multilayer electronic component such as a multilayer capacitor.

[0002]

2. Description of the Related Art In recent years, there has been a demand for miniaturization of electronic devices. In order to achieve the miniaturization of the electronic devices, electronic components used therein have been miniaturized, and a large number of electronic components have been mounted on a substrate having a certain area. It is desirable to implement high-density packaging as much as possible. As one method of 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 laminated capacitor or the like formed by laminating electrodes and a dielectric, a metal is attached to both end surfaces where the internal electrodes are exposed to connect the individual internal electrodes, and the metal is connected to the laminated capacitor. And a bump was provided there.

More specifically, Ag / Pb or the like is first baked on both sides of a multilayer capacitor to form a lower electrode, Ni or the like is mounted on the lower electrode by plating to provide an intermediate electrode, and further solder is plated. Thus, an external electrode is formed and a bump is provided there.

[0005]

As described above, since the metal must 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 down. , Until the metal adheres to the lower surface of the capacitor. Therefore, when the capacitor is pulled up, the metal adhering to the periphery of the capacitor collects below due to its own weight, and is rounded due to surface tension, so that the surface of the formed electrode is inclined with respect to the lower surface of the capacitor. In some cases, it was very difficult to attach a bump to an electrode. In addition, it is necessary to apply an insulating resist to portions other than the bump mounting position in order to form bumps, which is troublesome. In addition, since the size of the capacitor itself is very small, it is difficult to handle, and the manufacturing cost is high. Was rising.

Further, there is also known a method in which a through hole is formed instead of providing a metal on a side surface to connect individual internal electrodes. However, in order to form the through hole, each electrode is drilled or the like after lamination. There is a problem that it is necessary to provide a through hole and apply a metal to the inner surface of the hole, which takes a lot of trouble in manufacturing.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a bump on a laminated electronic component that can be utilized without making a significant change in the bump forming process of a conventional laminated electronic component, and that can easily and reliably form a bump on the laminated electronic component. I do.

[0008]

Therefore, in order to solve the above-mentioned problems, in the present invention, a metal having no wettability with respect to solder is printed on both ends of a ceramic sheet before lamination, so that the internal electrode and the ceramic are laminated. After sequentially laminating the sheets, the ceramic sheet is laminated on the outer surface of the electronic component. Thereafter, the ceramic sheet is fired together with the internal electrodes to form external electrodes on the outer surface of the multilayer electronic component by firing the printed metal. Next, a metal having solder wettability is printed on the external electrode formed in this way at the place where the bump is to be attached to provide a bump electrode, and solder is provided on the bump electrode to form a bump.
The internal electrode and the external electrode are electrically connected separately.

[0009]

Since the external electrodes are formed by applying directly to the surface of the ceramic sheet by printing or the like and firing it, the surface is formed flat after firing and the bump electrodes can be easily printed on the surface. Since the external electrode has no wettability with respect to the bump, the solder for the bump is provided only on the bump electrode, so that the bump can be easily and reliably formed.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a bump forming method according to an embodiment of the present invention.

FIG. 1 shows an exploded view of the capacitor 2. The ceramic sheet 3 is made of a dielectric ceramic such as barium titanate, and an internal electrode 4 is formed on the surface of the ceramic sheet 3. The internal electrodes 4 are printed with silver or copper metal, and are alternately printed on the ceramic sheet 3 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 a ceramic sheet 5 having tungsten 7 applied to both ends by printing is laminated on the lowermost layer.

After laminating the ceramic sheet 3, the internal electrode 4 and the ceramic sheet 5 in this way, when 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. No external electrode 6 is formed.

Next, as shown in FIG. 2, two bump electrodes 11 are printed on the external electrodes 6 at both ends on the surface of the external electrodes 6 respectively. The printing of the bump electrode 11 uses silver having wettability to solder. And furthermore, capacitor 2
The lower electrodes 12 are connected to the external electrodes 6 on the respective sides and attached to both sides. The lower electrode 12 only needs to have conductivity, and the kind of metal is not particularly limited. Next, solder is provided on the bump electrode 11 and the bump 1
0 are 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 bumps 10.

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

In this embodiment, the external electrode 6 is formed of tungsten 7. However, in the present invention, the external electrode 6 is not required to have wettability to solder, and may be another metal such as chromium. In addition, the bump electrode 11 was formed by printing using silver. Similarly, the bump electrode 11 may have any wettability to solder, and may be gold, copper, an alloy of silver and lead, or the like, in addition to silver. Alternatively, the forming means may be performed by another method such as vapor deposition.

Further, the present invention is not limited to capacitors, but can be applied as a forming method when bumps are attached to the surface of electronic components manufactured by lamination such as a multilayer substrate.

[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 corresponding to the outer surface of the laminated component before firing, and this metal is fired. An external electrode with high flatness is formed, and an electrode for bump attachment is printed on this external electrode with a metal having good solder wettability, and a bump is attached to this bump electrode. It is possible to provide an effective bump forming method which is very high in mass productivity because it can be made high, the bumps can be easily and reliably attached, and the apparatus used for forming the conventional bumps can be used without significant changes.

[Brief description of the drawings]

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

FIG. 2 is an exploded perspective view of a capacitor illustrating 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 where the 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)

(57) [Claims] 1. A metal having low solder wettability is applied to both ends of an upper surface or a lower surface of a multilayer electronic component, and is baked to form an external electrode, and a metal having good solder wettability is bumped on the external electrode. A method for forming a bump on a laminated electronic component, the method comprising: applying solder to a mounting position, applying molten solder to the external electrode, and adhering solder to the bump mounting position to form a bump on the laminated electronic component. 2. The multilayer electronic component according to claim 1, wherein the multilayer electronic component is a multilayer capacitor, wherein a lower electrode is provided on a side surface of the multilayer capacitor to integrally connect an internal electrode of the multilayer capacitor, and the lower electrode and an external electrode. And a bump forming method for a multilayer capacitor.