JPS6314845B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ceramic capacitor having an electrode structure useful for example in chip capacitors.

In recent years, various electronic components have been made into chips in order to remove inductance components caused by lead terminals and make electronic components suitable for use at high frequencies. Electronic components made into chips in this manner are advantageous in that they are compact.

Conventional chip capacitors use multilayer electrodes made of Ti-Pd-Au as ceramic dielectric electrodes. However, during the die bonding process, the chip capacitor including the electrodes is exposed to heat, and gas components present in the capacitor dielectric are released, thereby creating a space between the ceramic dielectric and the electrodes. It was observed that there was a tendency for tanδ to deteriorate.

In view of this background, the present invention provides a ceramic capacitor having an electrode configuration suitable for chipped electronic components, particularly chip capacitors.

More specifically, the present invention provides a ceramic capacitor whose electrode strength does not deteriorate even when a thermal load is applied.

Other objects and features of the present invention will become more apparent from the detailed description given below with reference to the drawings.

The drawing is a sectional view of a ceramic capacitor according to an embodiment of the present invention.

In the figure, numeral 1 is a ceramic dielectric substrate, which is obtained by a normal ceramic manufacturing process.

Typical materials constituting the dielectric substrate 1 include high dielectric constant dielectric ceramic, temperature compensating dielectric ceramic, and grain boundary insulated semiconductor ceramic. Among these, examples of grain boundary insulated semiconductor ceramics include SrTiO ₃ -based and BaTiO ₃ -based.

Metal oxide layers 2 and 3 are formed on both main surfaces of the ceramic dielectric substrate 1, respectively. Examples of metal oxides 2 and 3 include zirconia (ZrO ₂ ),
Examples include alumina (Al ₂ O ₃ ), zinc oxide (ZnO), and tin oxide (SnO ₂ ). The metal oxide layers 2 and 3 can be formed on both main surfaces of the ceramic dielectric substrate 1 by, for example, so-called reactive sputtering, which is carried out in an atmosphere consisting of argon and oxygen. Preferable from the standpoint of mass production. Therefore, various metal targets such as Zr, Al, Zn, and Sn are used as targets. Of course, formation by high frequency sputtering using a metal oxide target is also permitted.

On the metal oxide layers 2 and 3, nickel,
Metal layers 4 and 5 made of either copper are formed. The metal layers 4 and 5 are formed by dry plating, such as vacuum evaporation, sputtering, and ion plating.

Furthermore, on these metal layers 4 and 5, gold, platinum,
Metal layers 6 and 7 made of silver, tin, or a tin alloy are formed. The metal layers 6 and 7 are formed by dry plating or electrolytic plating such as vacuum evaporation, sputtering, and ion plating. Here, examples of tin alloys include tin-lead alloys and tin-indium alloys.

The ceramic capacitor constructed as described above includes a ceramic dielectric substrate 1, metal layers 4, 5,
and metal oxide layers 2, 3 between metal layers 6, 7.
Due to the interposition of the metal oxide layers 2 and 3, the ceramic dielectric substrate 1 and the metal layers 4 and 5 and the metal layers 6 and 7, especially the ceramic dielectric substrate 1 and the metal layer 4, are interposed. , 5 can be increased in adhesive strength. Therefore, even if heat is applied when die-bonding such a ceramic capacitor, it is possible to eliminate the phenomenon of peeling of the electrodes due to heat treatment. One of the reasons for this is that the metal layers 4 and 5 formed on the metal oxide layers 2 and 3 are made of either nickel or copper. That is, nickel and copper are easy to process when forming the metal layers 4 and 5, and have strong adhesive strength. Further, as the metal layers 6 and 7, gold,
Platinum, silver, tin, and tin alloys are used, and these are metals suitable for bonding, and gold, platinum, and silver are particularly suitable for die bonding.

Note that it is preferable to use a ceramic dielectric substrate 1 that has already been heat-treated. The basis for performing heat treatment in this way is
Due to the heat applied during bonding,
This is to release gas components generated from the ceramic dielectric substrate in advance. of course,
Even without heat treatment, since the metal oxide layers 2 and 3 are formed on the front and back main surfaces of the ceramic dielectric substrate 1, the gas components generated by the heat during bonding are absorbed by the metal oxide layer 2. , 3, and the problems encountered in the prior art do not occur.

The heat treatment temperature at this time is not particularly limited, but is preferably in the range of 200 to 350°C. This is because the gas components contained in the ceramic dielectric substrate 1 cannot be removed sufficiently at temperatures below 200°C, and on the other hand, heat treatment at temperatures below 350°C does not require treatment at high temperatures exceeding 350°C. This is because gas components can be removed. Therefore,
There is no need to particularly strictly consider the upper limit temperature.

Next, specific embodiments of the present invention will be described.

A TiO ₂ based ceramic dielectric substrate was prepared. This dielectric substrate was heat-treated in a temperature range of 200 to 350°C in a natural atmosphere. Next, this dielectric substrate was placed on the anode side of the sputtering apparatus, while a metallic zirconium target was placed on the cathode side. The inside of the vacuum chamber of the sputtering apparatus was once brought to a high vacuum of about 10 ^-6 Torr, and then a mixed gas of argon and oxygen was introduced to set the gas pressure at about 10 ^-1 to ^{10 -3} Torr. Thereafter, a high DC voltage was applied between the cathode and the anode, and a metal oxide layer made of zirconia was formed on the surface of the dielectric substrate by reactive sputtering.

Furthermore, using a nickel metal target, a high DC voltage is applied between the cathode and anode in a neutral or reducing atmosphere such as argon or nitrogen, and a nickel metal layer is applied on the metal oxide layer of the dielectric substrate. was formed.

Thereafter, sputtering was performed in the same manner using gold as the metal target to form a metal layer made of gold on the nickel metal layer.

When we measured the electrical characteristics of the ceramic capacitor obtained in this way with a size of 1 mm x 1 mm x 0.2 mm, we found that the measurement frequency was 1 MHz.
The values shown were dielectric constant 2700, tan δ 0.3 to 0.4%, and insulation resistance (IR) = 10 ¹² Ω·cm.

When we similarly measured the electrical characteristics of a conventional ceramic capacitor with electrodes made of Ti-Pd-Au, we found that it had a dielectric constant of 2700 and a tanδ of 0.6~
The values were 0.8% and insulation resistance (IR) = 10 ¹² Ωcm.

Furthermore, when each of these samples was heat treated at a temperature of 400°C, there was no problem with the adhesive strength of the samples according to the present invention.
It was confirmed that in the conventional example, the electrode was lifted from the ceramic dielectric substrate, the tan δ was decreased, and the adhesive strength was also significantly decreased.

Although the above-mentioned specific example of manufacturing one ceramic capacitor has been described, a large ceramic dielectric substrate is used and metal oxide layers 2, 3, metal layers 4, 5,
By sequentially forming the metal layers 6 and 7 and then cutting, it is also possible to manufacture microscopic ceramic capacitors. In this case, depending on the size of each ceramic capacitor to be obtained through the mask, metal oxide layers 2, 3, metal layer 4,
5 and metal layers 6 and 7 are also included.

As described above, the ceramic capacitor according to the present invention includes a metal oxide layer formed on the surface of a ceramic dielectric substrate, a metal layer of either nickel or copper formed on this layer, and a metal layer further formed on the metal oxide layer. ,
A metal layer of platinum, silver, tin, or a tin alloy is formed, and since the first layer is a metal oxide layer, it absorbs gas components from the ceramic dielectric substrate generated during heat treatment. , has the effect of not causing peeling from the metal layer formed thereon and made of either nickel or copper. In addition, the metal layer made of either nickel or copper has excellent adhesive strength with the metal oxide layer, and is suitable for bonding with the metals formed on it, such as gold, platinum, silver, tin, and tin alloys. Sufficient adhesion strength with the layer can be ensured, and the peeling phenomenon of electrodes can be eliminated with respect to the bonding required as capacitors are made into smaller chips.

[Brief explanation of the drawing]

The drawing is a sectional view showing an example of the ceramic capacitor of the present invention. In the figure, 1 is a ceramic dielectric substrate, 2,
3 is a metal oxide layer, and 4, 5, 6, and 7 are metal layers.

Claims (1)

[Claims] 1. A metal oxide layer is formed on the surface of a ceramic dielectric substrate, a metal layer of nickel or copper is formed on this, and further a metal layer of gold, platinum, or
A ceramic capacitor formed with a metal layer of silver, tin, or a tin alloy. 2. The ceramic dielectric substrate is placed in a natural atmosphere.
The ceramic capacitor according to claim 1, which is heat-treated at a temperature of 200 to 350°C. 3. The ceramic capacitor according to claim 1, wherein the metal oxide layer is made of any one of zirconia, alumina, zinc oxide, and tin oxide.