JPH0983215A - Small sized chip attenuator for microwave and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave use small sized chip attenuator miniaturized to the same degree as the size of a chip transistor. SOLUTION: A resistance film 2, an earth electrode film 3 and input-output electrode films 4a, 4b are formed on an insulation board 1. The earth electrode film and the input output electrode film are formed symmetrically around the resistance film 2. The resistance film 2 is trimmed by thermal formation only to adjust the characteristic impedance. The length of the earth electrode film 3 from the center of the resistance film 2 to the end of the earth electrode film 3 is formed shorter than the length from the center of the resistance film 2 to the end of the input-output electrode films 4a, 4b so that the entire pattern is formed into T-shape. The length of the earth electrode film 3 is selected so that the attenuation deviation for a predetermined frequency range is within a predetermined permissible range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a small chip attenuator for microwaves, which is a small chip attenuator suitable for use in a microwave region, and a small chip attenuator for microwaves.

[0002]

2. Description of the Related Art A chip type attenuator used in a microwave region is used for correcting characteristics of a chip transistor in a communication device, a radio device or the like. The structure of a conventional chip-type attenuator is, for example, as shown in FIG. 5, a resistance film 2 and ground electrode films 3a, 3 on an insulating substrate 1 such as alumina.
It is general that b and the pair of input / output electrode films 4a and 4b are arranged in a symmetrical pattern. In this chip-type attenuator, a rectangular resistance film 2 is arranged substantially in the center of an insulating substrate 1, and rectangular ground electrode films are formed above and below the insulating substrate 1 so that both ends of the resistance film 2 in the longitudinal direction are connected. 3a, 3
b is provided. Then, one ends of the rectangular input / output electrode films 4a and 4b are connected to substantially the central portion in the longitudinal direction of the resistance film 2. The pattern shape of each of these films is designed by assuming the characteristic impedance and the attenuation value, which are important basic characteristics of the chip-type attenuator. The insulating substrate 1 of the conventional small chip attenuator for microwaves has a size of 2 mm × 3 mm even if it is small. Conventionally, when manufacturing a chip attenuator, a thin film such as a vacuum deposition method or a sputtering method is used. A film is formed using a forming technique, and after the film is formed, heat treatment and optical or mechanical trimming using a laser are performed to adjust to obtain a predetermined characteristic value, and a desired chip attenuator is manufactured. . In the heat treatment, the characteristic impedance is determined by adjusting the heating time and temperature, and the attenuation value is adjusted by correcting the width of the resistance film or each electrode film by mechanical or optical trimming using a laser. In particular, the insulating substrate 1
When the dimension of is reduced, the operator manually performs the trimming one by one.

[0003]

The size of the chip transistor used together with this chip type attenuator is generally about 1 mm × 1 mm. Therefore, to meet the demand for higher circuit density, the size of the chip type attenuator must be reduced corresponding to the size of the chip transistor. However, in miniaturizing the chip type attenuator, even if the conventional pattern is miniaturized as it is, it is difficult to obtain a predetermined characteristic because it is premised on the characteristic value adjustment by the heat treatment and the trimming process. In particular, it is complicated to perform a two-step characteristic value adjusting process of heat treatment and trimming also in the manufacturing process, and the pattern of the miniaturized pattern has a geometrically fine pattern. It has been extremely difficult to perform dynamic trimming. Furthermore,
When the size is reduced, the size of the electrodes is reduced, so that the influence of the inter-electrode capacitance is increased and the deviation of the attenuation amount in the high frequency region is increased.

It is an object of the present invention to provide a smaller chip attenuator for microwaves and a manufacturing method thereof, which is smaller than the conventional one.

Another object of the present invention is to provide a method of manufacturing a compact chip attenuator for microwaves, which is downsized to the same size as or smaller than the size of a chip transistor and has a simplified manufacturing process.

A further object of the present invention is to provide a compact chip attenuator for microwaves which is miniaturized and has a small deviation value of attenuation amount in a high frequency region.

[0007]

According to the present invention, a ground electrode film, a resistance film electrically connected to the ground electrode film, and a pair of input / output electrode films serially connected to each other via the resistance film are provided. A small chip attenuator for microwaves formed on an insulating substrate and a method for manufacturing the same. In the present invention, the characteristic impedance is adjusted only by thermal formation of the resistance film in the manufacturing process. Here, thermal formation means that the surface of the resistance film is oxidized by heat treatment of the formed resistance film to substantially make a part of the surface of the resistance film an insulating film, thereby reducing the thickness of the resistance film functioning as a resistor. Is a trimming method for increasing the resistance value.

Further, in the present invention, the length of the ground electrode film is determined so that the attenuation deviation of the frequency characteristic falls within the allowable range. Here, "determining the length of the earth electrode film so that the attenuation deviation of the frequency characteristic falls within an allowable range" means, for example, that the operating frequency range is from 10 GHz to DC, and the allowable attenuation deviation range is ± 1 dB. In this case, it means that the length of the earth electrode film is adjusted so that the range of the attenuation amount deviation is within ± 1 dB.

The ground electrode film and the pair of input / output electrode films are
It is formed on the insulating substrate so that it is symmetrical about the resistance film, and the length from the center of the resistance film to the end of the ground electrode film is greater than the length from the center of the resistance film to the end of the input / output electrode film. It is preferable to form the ground electrode film so as to be short.
When the dimension between electrodes becomes small, the capacitance between electrodes becomes a problem.
Changing the dimensions of the input / output electrodes has a large effect on the characteristics, but the dimensions of the ground electrode do not particularly affect the characteristics. Therefore, by shortening the length of the ground electrode film, the influence of the capacitance between the electrodes can be reduced.

With the above-described structure, the compact chip attenuator for microwaves can be miniaturized to a size corresponding to, for example, the size of a chip transistor or less. In addition, it is possible to manufacture with a predesigned pattern so that the attenuation deviation of the frequency characteristic falls within a certain allowable range, and because the characteristic impedance can be adjusted only by thermal formation of the resistive film, the manufacturing process can be simplified, so it is inexpensive. Further, it is possible to obtain a compact chip attenuator for microwaves which is small and has excellent characteristics.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a plan view showing an electrode pattern of a small chip attenuator for microwaves according to an embodiment of the present invention. In this figure, 1 is purity 9
It is an insulating substrate made of an alumina substrate having a dielectric constant of about 9.7 at 9.5% and has a square shape of 1 mm × 1 mm.
Reference numeral 2 denotes a resistance film formed in a vertically long rectangular shape in a substantially central portion of the insulating substrate 1. This resistance film is formed of a tantalum thin film. The tantalum thin film that constitutes the resistance film 3 includes a ground electrode film 3 and a pair of input / output electrode films 4a and 4b described later.
Is formed on the insulating substrate 1 so as to form the underlayer of Therefore, the T shown in FIG. 1 is formed on the surface of the insulating substrate 1.
The tantalum thin film is formed in a V-shaped pattern.

Reference numeral 3 denotes a ground electrode film, which is formed in a horizontally long rectangular shape under the insulating substrate 1. The central portion of the ground electrode film 3 in the longitudinal direction is electrically connected to one end of the resistance film 2, and the ground electrode film 3 is bilaterally symmetrical with respect to a center line XY extending in the longitudinal direction of the resistance film 2. It is formed to have a shape. Further, 4a and 4b are horizontally long rectangular input / output electrode films electrically connected to the other end of the resistance film 2. The input / output electrode films 4a and 4b are connected to the other end of the resistance film 2,
The resistance film 2 is formed so as to be symmetrical with respect to the center line XY. Then, as shown in the figure, the resistance film 2
Is formed so that the short side at the other end in the longitudinal direction and the long side above the input / output electrode films 4a and 4b are aligned with each other.

Ground electrode film 3 and input / output electrode films 4a, 4
b is 500 angstrom N on a tantalum thin film.
A thin film of iCr is formed by vapor deposition, and an Au thin film having a thickness of 3 μm is formed thereon. In practice, a NiCr thin film and an Au thin film are entirely formed on the tantalum thin film, and a portion of the resistance film 2 is exposed by using a photoetching technique, and the ground electrode film 3 and the input / output electrode films 4a and 4b are formed. To form. The tantalum thin film forming the resistance film 2 and the gold thin film forming the ground electrode film 3 and the input / output electrode films 4a and 4b are formed by a thin film forming technique such as a vacuum deposition method or a sputtering method.

Although not shown, a conductive electrode film made of an Au (gold) thin film is entirely formed on a reverse surface of the insulating substrate 1 on which these patterns are formed, although not shown. This eliminates the influence of the capacitance generated due to the thickness of the insulating substrate 1 between the surface on the pattern side and the back surface on the conductive electrode side. When actually used, the conductive electrodes on the back surface are connected to a printed circuit board or the like by a conductive adhesive or soldering.

Generally, when the size is reduced, the dimension between electrodes becomes small and the capacitance between the electrodes affects the characteristics. Therefore, if the length of the ground electrode film 3 is increased, the ground electrode film 3 and the input / output electrode film 4a, The capacitance between 4 and 4b affects the attenuation amount characteristic in the high frequency region. Therefore, in this embodiment, the length of the ground electrode film 3 is shortened to adjust the interelectrode capacitance. That is,
The length from the center line XY of the resistive film 2 to the end of the ground electrode film 3 in the longitudinal direction is measured from the center line XY of the resistive film 2 to the end of the input / output electrode films 4a and 4b in the longitudinal direction. The capacitance between the electrodes is adjusted to be shorter than the length. How to shorten the length of the ground electrode film 3 is appropriately determined.

From the above requirements, the resistance film 2, the ground electrode film 3 and the input / output electrode film 4a formed on the insulating substrate 1
The arrangement pattern of 4b is basically T-shaped. When arranging the T-shaped pattern on the insulating substrate 1, as shown in FIG. 1, a gap is formed so as to form a predetermined peripheral space between the peripheral portion of the insulating substrate 1 and the peripheral portion of the T-shaped pattern. D1, D2 and D3 are opened. This is to prevent cracks that may occur in the cutting and separating steps, which will be described later, from entering the pattern and prevent characteristic changes.

The amount of attenuation is determined by adjusting the width A of the resistance film 2, the width B of the ground electrode film 3 and the width C of the input / output electrode films 4a and 4b shown in FIG. In the present embodiment, the length of the ground electrode film 3 is 0.4 mm, D1 = 0.2 mm, D
2 = 0.05 mm. Input / output electrode films 4a, 4
If the width C of b is made too small, the characteristics in the high frequency region deteriorate, so the width C cannot be changed significantly. In order to improve the frequency characteristic of the attenuation amount deviation, the inter-electrode capacitance is set to L and C which the input / output electrode films 4a and 4b have.
It is necessary to determine the balance with the [capacitance formed on the upper side of the electrode (upward in the thickness direction of the substrate 1)], but this can be determined by calculation by an electronic computer using simulation software. A preferable concrete numerical value in the embodiment is as follows. When the attenuation amount is 3 dB, A = 0.089.
mm, B = 0.25 mm, C = 0.26 mm, and when the amount of attenuation is 5 dB, A = 0.157 mm, B = 0.2
It is preferable that 5 mm and C = 0.26 mm. Furthermore,
When the amount of attenuation is 10 dB, A = 0.333 mm, B =
It is 0.25 mm and C = 0.26 mm. The above numerical values show one example, and are not limited to these numerical values. That is, the allowable range of these numerical values is determined by the allowable range of the attenuation deviation, and the individual numerical values can be changed by changing the fixed numerical values such as the interval for forming the ground electrode film and the surrounding space. Is changed.

Next, a method of adjusting the characteristic impedance will be described. In the past, heat treatment and mechanical or optical trimming were used together to adjust the characteristic impedance, but it is extremely difficult to use the conventional trimming method by making it compact as described above. In the present invention, the characteristic impedance is adjusted using only thermal conversion.
In thermal formation, the formed resistance film 2 is subjected to heat treatment (left in heated air of several hundreds of degrees) to oxidize the surface of the resistance film 2, and a part of the surface of the resistance film is made into an insulating film (tantalum pentoxide). The characteristic impedance is adjusted by increasing the resistance value of the resistance film 2.

When this is specifically shown, the characteristic impedance value can be determined from the relationship between the characteristic impedance and the heat treatment time as shown in FIG. For example, if the characteristic impedance value to be set is 50Ω, 320
It becomes 50.38Ω by heating at ℃ for 90 minutes, so it is about 8 from Fig. 2.
When the heat treatment is performed for 0 minutes, a characteristic impedance value of 50Ω can be obtained. In this way, the characteristic impedance can be determined by adjusting the heating temperature and the heat treatment time.

Next, the manufacturing process of the small chip attenuator for microwaves according to the present invention will be described. First, on a large-sized insulating substrate capable of forming a large number of small chip attenuators for microwaves, a resistance film made of tantalum nitride is formed over the entire insulating substrate by using a thin film forming technique such as a vacuum deposition method or a sputtering method according to a predesigned pattern. Many are formed. Next, an underlayer made of NiCr and an Au layer formed on the underlayer were formed by using a similar thin film forming technique in accordance with a previously designed pattern.
And a thin film of. Then, after that, the resistance film 2 is exposed by photoetching to simultaneously form an earth electrode film and an input / output electrode film, and a large number of small chip attenuators for microwaves are formed at once on a large insulating substrate. Since the conductive electrode film on the back surface of the insulating substrate is formed of the NiCr film and the gold thin film, it may be formed at the same time when the ground electrode film and the input / output electrode film are formed, or may be collectively formed last. May be. Further, this conductive electrode may be formed by a print coating technique of a conductive paint.

After measuring the characteristics of each of the small chip attenuators for microwaves formed in this way, the substrate is cut and separated by a laser or a diamond cutting machine, and the characteristics are divided into groups. A plurality of attenuators divided into these groups are subjected to thermal chemical conversion treatment according to their characteristics, and each attenuator is adjusted to a predetermined characteristic impedance to obtain a product.

Although a ceramic substrate is used as the insulating substrate in the above description, an insulating resin substrate or the like may be used as long as it can withstand high temperature processing. The size of the insulating substrate is also 1 mm ×
It is not limited to 1 mm. Although the resistance film is made of tantalum in this embodiment, the resistance film may be formed of tungsten, titanium, nickel chrome, or the like. Also,
Although NiCr and Au were used as the materials for the ground electrode film, the input / output electrode film, and the conductive electrode film, it is clear that a highly conductive material such as silver or copper may be used. Therefore, depending on the material, whether the resistance film is formed first, the ground electrode film and the input / output electrode film are formed first, or the thin film forming process changes, but the order of these processes is not limited. Of course, the order of forming the conductive electrode film is not limited. Generally, it is common sense to perform the step of performing the higher temperature treatment first. In the above manufacturing process, the measurement was performed before the cutting / separating process, but it is clear that the cutting / separating process may be performed first. Further, the thermal formation step may be performed for each large insulating substrate before the cutting and separating steps as long as the characteristics of individual small chip attenuators for microwaves on the large insulating substrate are uniform. Further, in the cutting and separating steps, first, dividing grooves may be formed in a large insulating substrate according to the size of each small chip attenuator for microwaves, and the dividing grooves may be divided later.

FIG. 3A shows another embodiment of the present invention. This embodiment is substantially different from the embodiment of FIG. 1 in the shape of the input / output electrode films 4a and 4b. In the present embodiment, the input / output electrode films 4a and 4b are overlapped portions, that is, the protruding electrode portions 4a1 and 4b1 protruding inward in the width dimension of the resistance film 2.
It has. When the protruding electrode portions 4a1 and 4b1 are not formed, current concentration occurs at the corner formed between the input / output electrode film and the resistance film, and the resistance value changes at that portion, which is an extreme case. Cracks occur due to aging. In addition, the electric high frequency characteristic is also deteriorated. FIG. 3 (B)
It is the ZZ sectional view taken on the line of FIG. When thermal formation is performed,
In the figure, the surface portion 2a is oxidized to tantalum pentoxide, and the inside 2b remains as tantalum. The resistance value of the resistance film 2 is adjusted by changing the degree of oxidation of the surface portion 2a. The high frequency current flows through the inside 2b.

The trimming method of the present invention can be applied to a small chip attenuator for microwaves having both ground patterns as shown in FIG. In addition, in the embodiment of FIG.
In the same manner as in the above embodiment, the pair of input / output electrodes 4'a and 4'b project inward in the width direction of the resistance film 2 ', and the protruding electrode portion 4'a1.
And 4'b1. The insulating substrate 1'of this embodiment also has a size substantially equal to the size of the chip transistor, and the resistance value of the resistance film 2'is adjusted only by thermal formation. When this attenuator is mounted on a circuit board, a back electrode made of a thin film of NiCr and a thin film of Au provided on the back surface of the insulating substrate 1'is soldered to the electrode on the circuit board by AuSn solder. The ground electrodes 3'a and 3'b and the input / output electrodes 4'a and 4'b are bonded to the electrodes on the circuit board by bonding wires. The ground electrodes 3'a and 3'b may be electrically connected by soldering.

The structure of one invention selected from the plurality of inventions described in this specification will be described below.

(1) A ground electrode film, a resistance film having one end connected to the ground electrode film, and a resistance film on each of the insulation substrates of the division substrate in which a division groove for indexing the insulation substrate is formed. After forming a circuit pattern having a pair of input / output electrode films connected to each other in series via, a method for manufacturing the microwave small chip attenuator by dividing the dividing substrate along the dividing groove, A method of manufacturing a small chip attenuator for microwaves, characterized in that the circuit pattern is formed so as to leave a space around the circuit pattern where a scratch that may occur when the dividing substrate is divided is left.

[0027]

As described above, according to the present invention, the compact chip attenuator for microwaves can be made smaller than the conventional one. Further, it is possible to easily manufacture a small chip attenuator for microwaves in which the deviation of the attenuation amount falls within a certain allowable range.

[Brief description of drawings]

FIG. 1 is a plan view showing a pattern of a small chip attenuator for microwaves according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a characteristic impedance and a heat treatment time for explaining thermal conversion used in the present invention.

3 (A) and 3 (B) are a plan view showing a pattern of a small chip attenuator for microwaves of another embodiment of the present invention and a cross-sectional view taken along line ZZ of FIG. 3 (A).

FIG. 4 is a plan view showing a pattern of a small chip attenuator for microwaves according to still another embodiment of the present invention.

FIG. 5 is a plan view of a pattern showing an example of a conventional chip type attenuator.

[Explanation of symbols]

 1 Insulating substrate 2 Resistive film 3 Earth electrode film 4a, 4b Input / output electrode film

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yozo Ohara 3158 Shimookubo, Osawano-cho, Kamishinkawa-gun, Toyama Prefecture Hokuriku Electric Industry Co., Ltd.

Claims (5)

[Claims] 1. A ground electrode film, a resistance film electrically connected to the ground electrode film, and a pair of input / output electrode films serially connected to each other via the resistance film are formed on an insulating substrate. In the method for manufacturing a small chip attenuator for microwaves, the method for manufacturing a small chip attenuator for microwaves characterized in that the characteristic impedance is adjusted only by thermal formation of the resistance film. 2. A ground electrode film, a resistance film electrically connected to the ground electrode film, and a pair of input / output electrode films serially connected to each other via the resistance film are formed on an insulating substrate. In the method for manufacturing a small chip attenuator for microwaves, the characteristic impedance is adjusted only by thermal formation of the resistance film, and the length of the earth electrode film is adjusted so that the attenuation deviation of the frequency characteristic falls within the allowable range. A method for manufacturing a compact chip attenuator for microwaves, which is characterized. 3. A ground electrode film, a resistance film electrically connected to the ground electrode film, and a pair of input / output electrode films serially connected to each other via the resistance film are formed on an insulating substrate. In the small chip attenuator for microwaves, the resistance film is trimmed by thermal formation, and the length of the ground electrode film is determined so that the attenuation deviation of the frequency characteristic falls within an allowable range. A characteristic compact chip attenuator for microwaves. 4. A ground electrode film, a resistance film whose one end is connected to the ground electrode film, and a pair of input / output electrode films connected in series with each other via the resistance film, with the resistance film as the center. In the small chip attenuator for microwaves formed on the insulating substrate so as to have a symmetrical shape, the resistance film is trimmed by thermal formation, and the length from the center of the resistance film to the end of the ground electrode film is increased. The ground electrode film is formed so that the length is shorter than the length from the center of the resistance film to the end of the input / output electrode film, and the length of the ground electrode film is in a predetermined frequency range. A small chip attenuator for microwaves, wherein the attenuation deviation is determined to fall within a predetermined allowable range. 5. The pair of input / output electrode films have protruding electrode portions protruding toward the resistance film side.
Alternatively, the small chip attenuator for microwave according to the item 4.