JPH0897073A - Formation of thin film terminal electrode - Google Patents

Abstract

PURPOSE: To form a thin film terminal electrode with high productivity while shortening the time required for the thin film formation process and enhancing the bonding strength of the thin film with respect to a bare chip. CONSTITUTION: When thin film terminal electrodes 15 are formed at the opposite end parts of an element of chip capacitor 10, chip thermistor, chip resistor, chip inductor or chip LC filter, i.e., a bare chip 11 of sintered ceramic, thin films 16, 17, 18 are formed at the opposite end parts of the bare chip 11 by vapor phase method in an inert gas under vacuum pressure at room temperature and then the bare chip 11 is heat treated in a reductive atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming terminal electrodes of chip type electronic parts such as chip capacitors, chip thermistors, chip resistors, chip inductors and chip LC filters. More specifically, the present invention relates to a method for forming terminal electrodes made of a thin film on both ends of a bare chip of a ceramic sintered body which is an element body of a chip-type electronic component.

[0002]

2. Description of the Related Art Conventionally, as a method of forming a terminal electrode of this type, a Cr first electrode layer is formed on the end of a bare chip by a sputtering method, and a Cr-Ni alloy or Cu-Ni alloy is formed on the first electrode layer by a sputtering method. Alternatively, a method of forming a second electrode layer of Cu and then forming a third electrode layer of Sn or Sn-Pb alloy thereon by electrolytic plating or electroless plating is disclosed (JP-A-60-195916). ).
As another forming method, a method of forming a third electrode layer in addition to the first electrode layer and the second electrode layer by a sputtering method, a vacuum vapor deposition method or a plasma spraying method has been proposed (JP-A-3-225810). .

The former method heats the bare chip to 150 ° C. to 200 ° C. during sputtering, and the latter method heats the bare chip during sputtering, vacuum deposition or plasma spraying, or forms an electrode layer at room temperature. ing.

[0004]

However, when forming a thin film while heating by a conventional sputtering method, etc.,
Although relatively high thin film adhesion strength can be obtained, it takes a long time to reach a desired vacuum pressure because the degree of vacuum decreases during the temperature rising process. Moreover, after forming a film by a sputtering method etc., it is necessary to cool it to room temperature in vacuum. Takes a long time, and as a result, there is a problem that productivity is poor. Further, when the thin film was formed by the sputtering method at room temperature, the above-mentioned problems did not occur, but the adhesive strength of the thin film to the bare chip was not sufficiently high.

An object of the present invention is to provide a method for forming a thin film terminal electrode, which requires a short time for forming a thin film, has high productivity, and has high adhesion strength of a thin film to a bare chip.

[0006]

In order to achieve the above object, as shown in FIGS. 1 and 2, the present invention is a bare chip of a ceramic sintered body which is an element body of a chip type electronic component such as a chip capacitor 10. Thin film terminal electrodes 15 on both ends of 11
It is an improvement of the method of forming the. The characteristic structure is that after forming thin films 16, 17 and 18 on both ends of bare chip 11 at room temperature by a vapor phase method in an inert gas of vacuum pressure, bare chip 11 on which this thin film is formed is placed in a reducing atmosphere. It is in heat treatment.

The present invention will be described in detail below. The terminal electrode of the present invention is a terminal electrode of a chip-type electronic component such as a chip capacitor, a chip thermistor, a chip resistor, a chip inductor, and a chip LC filter. The vapor phase method of the present invention includes a sputtering method, a vacuum vapor deposition method, a plasma spraying method,
There are an ion plating method, a CVD (chemical vapor deposition) method, and the like. The sputtering method may be any of a high frequency method and a magnetron method, but a magnetron sputtering method in which the temperature of the bare chip during the sputtering is small is preferable. Examples of the inert gas include rare gases such as Ar, He and Ne.

The terminal electrode 15 may be composed of a single-layer thin film, but may be composed of a plurality of thin films. As the first thin film 16 that is directly adhered to the bare chip, a thin film made of V (vanadium) or Cr (chrome) and an alloy thereof having high adhesive strength is preferable. As the second thin film 17 formed on the first thin film, Ni (nickel) or Cu having high heat resistance is used so that the thin film is not eroded when the chip type electronic component is soldered to the printed circuit board.
Thin films of (copper) and alloys of these are preferred.
Further, as the third thin film 18 formed on the second thin film, the first
Alternatively, a thin film made of Au (gold) is preferable in order to prevent oxidation of the second thin film and enhance solder wettability.

The heat treatment temperature after forming the thin film is 100
℃ ~ 400 ℃ is required, 150 ℃ ~ 20
0 ° C is preferred. The heat treatment time is 0.5 hours
It is necessary to be 4 hours, and preferably 1 hour to 2 hours. If it is less than 100 ° C. or less than 0.5 hours, the adhesive strength of the thin film is not practically sufficient, and even if it exceeds 400 ° C. or 4 hours, the adhesive strength of the thin film does not become higher than that at 400 ° C. or 4 hours. The reducing atmosphere during this heat treatment contains CO ₂
Gas or N ₂ gas is used.

[0010]

When the chamber is evacuated to high vacuum at room temperature, the desired vacuum pressure is reached relatively quickly. If an inert gas is introduced in this state to form a thin film, the film formation rate increases due to the influence of the inert gas. 100 ℃ ~ 400 after forming a thin film
When heat-treated at a temperature range of ℃ for 0.5 to 4 hours, the metal layers diffuse and adhere to each other at the interface with the bare chip or at the interface between thin films when a plurality of thin films are stacked. . As a result, it adheres strongly to the bare chip. By reducing the atmosphere during the heat treatment, oxidation of the thin film is prevented.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. A chip capacitor 10, which is the chip type monolithic ceramic capacitor shown in FIG. 1, was manufactured by the following method. In FIG. 1, 11 is a bare chip, 11a is an internal electrode, 16 is a first thin film, 17 is a second thin film, 18 is a third thin film, and 15 is a terminal electrode composed of first to third thin films. First, as shown in FIG. 3, a large number of through holes 12 for accommodating bare chips 11 made of a large number of ceramic sintered bodies are formed.
The chip holding plate 13 having the above space was prepared, and the chip holding plate 13 was placed on the base plate 14a having a larger area than the holding plate. As a result, the lower portion of the through hole 12 was closed by the base plate 14a. As shown in FIG. 2, the thickness of the chip holding plate 13, that is, the depth of the through hole 12 has such a dimension that the upper end portion of the bare chip 11 slightly projects when the bare chip 11 is inserted. In this state, each of the through holes 12 has a ceramic dielectric of 4.40 mm in length and 3.15 mm in width.
After inserting the bare chip 11 having a height of 1.13 mm, the chip holding plate 13 together with the base plate 14a was placed in a chamber of a magnetron-type sputtering device (not shown) and set.

The inside of the chamber is evacuated to a high vacuum, and Ar gas is supplied.
It is introduced until it reaches 0 × 10 ⁻¹ Pa and then at 20 ° C., as shown in FIG.
As shown in (a), one end of all bare chips 11 was sputtered. First, the first thin film made of V is formed, then the current-carrying electrode of the sputtering apparatus is changed, the second thin film made of Ni is formed on the first thin film, and finally the current-carrying electrode is changed to change the thickness of the second thin film. A third thin film of Au was formed on top. After the formation of the terminal electrode at one end is completed, the chip holding plate 13 together with the base plate 14a is taken out from the sputtering apparatus, and another base plate 14b is placed on the chip holding plate 13 as shown in FIG. 2 (b). The chip holding plate 13 was placed on the base plate 14a and turned upside down with the chip holding plate 13 sandwiched between the base plates 14a and 14b, and then the base plate 14a was removed.
The other end of the bare chip 11 protrudes from the chip holding plate 13, whereby the work of inserting the bare chip 11 into the through hole can be omitted. Subsequently, as shown in FIG. 2C, the chip holding plate 13 together with the base plate 14b was placed in the chamber of the sputtering apparatus and set, and the first to third thin films were similarly formed on the other end of the bare chip 11.
In FIG. 2, symbol B is a metal atom sputtered from the target.

A large number of chip capacitors 10 having terminal electrodes 15 formed on both ends thereof are taken out from the sputtering apparatus, and these chip capacitors 10 are divided into four equal parts.
Group (Example 1) in the N ₂ (nitrogen) gas atmosphere was 1
It heat-processed at 50 degreeC for 1 hour. The second group (Example 2) was heat-treated at 180 ° C. for 1 hour in an N ₂ gas atmosphere, and the third group (Example 3) was heated in an N ₂ gas atmosphere to 200 ° C.
Heat treatment was performed at 1 ° C. for 1 hour. The fourth group (Comparative Example 1) was not heat treated.

After soldering a pair of lead wires to the terminal electrodes at both ends of each of the ten chip capacitors of Examples 1 to 3 and Comparative Example 1, the chip capacitors were set in a tensile tester to make a pair. The lead wire was gripped, the tensile strength when the thin films 16 to 18 were peeled from the bare chips of these chip capacitors was measured, and the average value was obtained. Ten chip capacitors of each of Examples 1 to 3 and Comparative Example 1 were soldered to the front surface of a glass epoxy board having a thickness of 1.6 mm, and a force was applied to the back surface center of the board to bend the board. The amount of deflection of the alumina substrate when the edge of the bare chip was chipped or the thin film was peeled from the edge of the bare chip was measured, and the average value was obtained. Table 1 shows the results.

[0015]

[Table 1]

As is clear from Table 1, the chip capacitors of Examples 1 to 3 have a higher bonding strength of the terminal electrodes than the chip capacitors of Comparative Example 1 without heat treatment, and in particular, the chip capacitors of Example 3 having the highest heat treatment temperature. It was found that the adhesive strength of the terminal electrode was the highest.

[0017]

As described above, according to the present invention, since the inside of the chamber is vacuumed at room temperature to form a film, it does not take a long time to reach a desired vacuum pressure as in the conventional case, and Since it does not require cooling, the thin film formation process can be completed in a short time,
High productivity. Due to the heat treatment after the film formation, the metal layer at the interface of the thin film with the bare chip is diffused and adheres to the bare chip with high strength.

[Brief description of drawings]

FIG. 1 is a central longitudinal sectional view of a chip type monolithic ceramic capacitor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA of FIG. 3 in the process of forming the terminal electrode of the embodiment of the present invention.

FIG. 3 is a perspective view of a chip holding plate and a base plate according to the embodiment of the present invention.

[Explanation of symbols]

 10 Chip Capacitor 11 Bare Chip 12 Through Hole 13 Chip Holding Plate 14a, 14b Base Plate 15 Terminal Electrode 16 First Thin Film 17 Second Thin Film 18 Third Thin Film

Claims (3)

[Claims] 1. A thin film terminal electrode (15) is formed at both ends of a bare chip (11) made of a ceramic sintered body which is a body of a chip capacitor (10), a chip thermistor, a chip resistor, a chip inductor or a chip LC filter. In the method, after forming a thin film (16, 17, 18) on both ends of the bare chip (11) at room temperature by a vapor phase method in an inert gas of vacuum pressure, the bare chip (11) on which the thin film is formed A method for forming a thin film terminal electrode, characterized in that the film is heat-treated in a reducing atmosphere. 2. A first thin film made of V or Cr and an alloy thereof at both ends of a bare chip (11) at room temperature by a sputtering method in a vacuum pressure chamber into which an inert gas is introduced.
(16), a second thin film (17) made of Ni or Cu and their alloys, and a third thin film (18) made of Au are formed in this order, and then the thin films (16, 17, 18) are formed. The method for forming a thin film terminal electrode according to claim 1, wherein the bare chip (11) is heat-treated in a reducing atmosphere. 3. The heat treatment is performed at a temperature of 150 ° C. to 200 ° C. for 1 hour.
The method for forming a thin film terminal electrode according to claim 1 or 2, which is carried out for a time of 2 hours.