JP3246166B2 - Thin film capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip type thin film capacitor used for various electronic devices.

[0002]

2. Description of the Related Art In recent years, with the rapid miniaturization and high performance of electronic devices, there has been an increasing demand for miniaturization of electronic components and high-density mounting. For example, to reduce the size of a capacitor,
A method of increasing the dielectric constant of the dielectric and a method of reducing the thickness of the dielectric have been used. In order to mount a capacitor at a high density, a method of forming a chip and mounting it directly on a circuit board has been adopted.

[0003] Among the conventional capacitors, a multilayer ceramic capacitor most satisfies these requirements. That is, the ceramic dielectric is thinned and further stacked to reduce the size, and an outer layer electrode suitable for solder mounting on a circuit board is formed at an end to cope with chip formation.

[0004]

However, in the conventional multilayer ceramic capacitor, the thickness of the dielectric is limited to about 5 μm in order to ensure easy handling and accuracy when stacking raw sheets in the manufacturing process. It was very difficult to make it thinner. Therefore, there has been a limit to miniaturization of the capacitor.

[0005] The multilayer ceramic capacitor is mounted by soldering an outer layer electrode at an end thereof to a land portion of a circuit board. Therefore, a space for soldering lands is required on the circuit board, and there is a limit to miniaturization of the circuit board.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thin film capacitor having a smaller size and a structure capable of reducing a mounting space on a circuit board.

[0007]

In order to achieve the above object, a thin film capacitor according to the present invention has first and second capacitance electrodes formed on both main surfaces of an insulating substrate. The electrodes are electrically connected to each other through through holes, a dielectric thin film is formed on the first capacitance electrode formed on one main surface of the insulating substrate, and the dielectric thin film is formed on the dielectric thin film. First
A third capacitance electrode is formed with a gap from the first capacitance electrode, and the second capacitance electrode and the third capacitance electrode are externally connected.
It is characterized in that it also serves as an electrode for connection .

An outer layer electrode is formed on the second capacitor electrode and the third capacitor electrode to serve as an electrode for external connection .

A glass substrate or a ceramic substrate is used as an insulating substrate, a ceramic dielectric is used as a dielectric thin film, and Ag, Pd, Cu, Ni, Al is used as a capacitor electrode.
One or more types selected from Au and Pt, and the outer layer electrode is preferably one or more types selected from Au, Pt, Pd and Au.

The ceramic dielectric is selected from barium titanate, strontium titanate, lead zirconate titanate and lead magnesium niobate.
It is preferable that the type is the main component.

[0011]

The thin-film capacitor of the present invention uses a thin-film ceramic dielectric having a thickness of 1 μm or less as the dielectric. Therefore, a small capacitor can be obtained.

Further, since the thin film capacitor of the present invention has a structure having electrodes for external connection on the upper and lower main surfaces,
One external connection electrode can be soldered, and the other external connection electrode can be wire-bonded and mounted on a circuit board.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the thin film capacitor of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a thin film capacitor 11 showing a first embodiment, and FIG. 2 is a cross-sectional view taken along line XX of FIG. In FIG. 1, 1 is an insulating substrate made of crystallized glass, 3 is a dielectric thin film, and 5 is one outer layer electrode. In FIG. 2, reference numerals 2 and 2 ′ are formed on both main surfaces of the insulating substrate 1 and are electrically connected to each other through the through holes 7. electrode,
6 is the other outer layer electrode.

Next, a method of manufacturing the thin film capacitor of the present invention will be described with reference to FIG. First, 1mm square, thickness 200
Through holes 7 having a diameter of 300 μm were formed in an insulating substrate 1 made of crystallized glass of μm by a chemical etching method. Next, a conductive paste containing 80% by weight of Ag and 20% by weight of Pd as conductive components is printed on both main surfaces of the insulating substrate 1 by a paste printing method, and then baked at 800 ° C. The first and second capacitor electrodes 2 and 2 each having a square shape of 750 μm square and electrically connected to each other by a conductive paste filled in the through holes 7 at the time of printing the conductive paste.
'Was formed.

Next, a dielectric thin film 3 of strontium titanate having a thickness of about 0.7 μm is formed on the entire surface of the first capacitor electrode 2 formed on one main surface of the insulating substrate 1 by CVD. Formed. Thereafter, C is placed on the dielectric thin film 3.
u was vacuum-deposited to form a 700 μm square third capacitor electrode 4.

Finally, an outer electrode 5 is formed on the third capacitor electrode 4 and an outer electrode 6 is formed on the second capacitor electrode 2 'by electrolytic plating of Au.
I got

FIG. 3 shows a mounting example of the thin film capacitor thus obtained. The other outer layer electrode 6 of the thin film capacitor 11 of the present invention was soldered to a circuit board 12, and one outer layer electrode 5 and an electrode (not shown) on the circuit board 12 were connected by a gold wire 13 by wire bonding.

By adopting the above mounting method, the space occupied by the soldering lands when mounting and wiring the capacitor on the circuit board becomes unnecessary, and the mounting space on the circuit board is reduced along with the miniaturization of the capacitor. Was completed.

The method of manufacturing a thin film capacitor according to the present invention is not limited to the above embodiment. That is, as the method for forming the first and second capacitor electrodes, in addition to the paste printing method, the first and second capacitor electrodes may be formed by plating with the diameter of the through hole being about 100 μm. The third capacitor electrode can be formed by a paste printing method other than the vacuum evaporation method.

In the above embodiment, a glass substrate is used as an insulating substrate. However, the present invention is not limited to this, and a ceramic substrate can be used similarly.

Further, in the above embodiment, an Ag-Pd alloy and Cu are used as the capacitor electrodes, and Au is used as the outer layer electrodes. However, the present invention is not limited to this. For example,
As the capacitor electrode, in addition to the Ag-Pd alloy and Cu, known Ni, Al, Au, Pt, and the like as the capacitor electrode may be used alone or in combination, or Ag (lower layer) -Ni
(Multilayer) such as (upper layer) and Cu (lower layer) -Ni (upper layer) can be used as appropriate. Pt, Pt having good wire bonding properties other than Au as an outer layer electrode
d, Ag, etc. can be used alone or in combination.

In the above embodiment, strontium titanate is used as the dielectric thin film. However, the present invention is not limited to this. For example, barium titanate, strontium titanate, lead zirconate titanate, magnesium niobate may be used. Various high-dielectric-constant systems mainly composed of lead acid or the like or ceramic dielectrics for temperature compensation can be used. Among them, a thin film formed mainly by strontium titanate or lead magnesium niobate formed by the CVD method is most suitable as a ceramic dielectric.

Then, the first and second capacitance electrodes are formed to have a thickness that can withstand soldering by using a material having excellent solder heat resistance, and the third capacitance electrode is formed by using a material having excellent bonding property. Thus, the formation of the outer layer electrode on the capacitor electrode can be omitted.

The shape of the capacitor, including the shape of the electrodes, is not limited to this embodiment. Another embodiment will be described below. FIG. 4 shows a second embodiment, in which the insulating substrate 1
Three through-holes 7a and 7b are formed, and are divided into two on the dielectric thin film 3 formed on the first capacitance electrode 2 to form a third through-hole.
Are formed, and the outer electrode 5 is formed thereon.
By dividing a and b into two, two different capacitance components can be obtained in the same capacitor. The other parts are the same as those of the first embodiment shown in FIGS. 1 and 2, and the same reference numerals are given and the description is omitted.

Although the thin film capacitor of the present invention is directly mounted on a circuit board in the mounting example shown in FIG. 3, the thin film capacitor of the present invention is mounted on a semiconductor device such as an LSI. It can be electrically connected to a semiconductor element. In this case, no special mounting space or soldering space necessary for mounting the capacitor on the circuit board is required, and the circuit board can be further reduced in size.

[0026]

As is apparent from the above description, the thin film capacitor of the present invention has a dielectric thickness which is about one digit thinner than that of a conventional multilayer ceramic capacitor. Therefore, a small capacitor can be obtained.

Further, the thin film capacitor of the present invention has a structure having electrodes for external connection on the upper and lower main surfaces.
One external connection electrode can be soldered, and the other external connection electrode can be wire-bonded and mounted on a circuit board. Therefore, the space occupied by the soldering lands when mounting and wiring the capacitor on the circuit board becomes unnecessary, and the mounting space on the circuit board can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of a thin film capacitor of the present invention.

FIG. 2 is a cross-sectional view taken along line XX of FIG.

FIG. 3 is a sectional view showing a state where the thin film capacitor of the present invention is mounted.

FIG. 4 is a sectional view showing a second embodiment of the thin film capacitor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2, 2 ', 4 Capacitance electrode 3 Dielectric thin film 5, 6 Outer layer electrode 7 Through hole 11 Thin film capacitor

────────────────────────────────────────────────── ─── Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01G 4/00-4/12 H01G 4/14-4/42 H01G 13/00-13/06

Claims (8)

(57) [Claims] A first and a second capacitor electrode are formed on both main surfaces of an insulating substrate, and the first and second capacitor electrodes are electrically connected to each other through a through hole. A dielectric thin film is formed on the first capacitor electrode formed on one main surface, and a third capacitor electrode is formed on the dielectric thin film with a gap from the first capacitor electrode. And the second
The capacitance electrode and the third capacitance electrode also serve as external connection electrodes.
Thin film capacitor, characterized in that it is sleep. 2. The thin film capacitor according to claim 1, wherein an outer layer electrode is formed on the second capacitor electrode and the third capacitor electrode, and serves as an electrode for external connection . 3. The thin film capacitor according to claim 1, wherein the insulating substrate is made of one selected from a glass substrate and a ceramic substrate. 4. The thin film capacitor according to claim 1, wherein the dielectric thin film is made of a ceramic dielectric. 5. The ceramic dielectric according to claim 4, wherein the ceramic dielectric comprises one of barium titanate, strontium titanate, lead zirconate titanate and lead magnesium niobate as a main component. Thin film capacitors. 6. The capacitor electrode is made of Ag, Pd, Cu, Ni,
3. The thin film capacitor according to claim 1, comprising at least one selected from Al, Au, and Pt. 7. An outer electrode comprising Au, Pt, Pd and A
3. The thin film capacitor according to claim 2, comprising at least one kind selected from g. 8. The insulating substrate is made of crystallized glass, the dielectric thin film is mainly made of strontium titanate or lead magnesium niobate, and the first and second capacitor electrodes are made of an Ag—Pd alloy. 3. The thin film capacitor according to claim 2, wherein the capacitor electrode of No. 3 is made of Cu, and the outer layer electrode is made of Au.