JP2000082877A - Manufacture of thin film circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a through-hole that is high in connection reliability by a method wherein a conductive film is provided in a through-hole that penetrates obliquely through a board, whose main component is alumina, from its front surface to rear surface. SOLUTION: A through-hole 8 is provided in a board 1 that contains alumina of purity 99.5% or above penetrating obliquely through it from its front surface to rear surface. The oblique through-hole 8 has a structure where its rear opening is displaced in parallel from the front opening by a distance equal to the thickness of the board 1 or above. A resistive film 2 of tantalum nitride or the like, a chromium film 3a that improves a conductor film in adhesion to the board 1, a copper film 4a that ensures the board 1 of high-frequency characteristics, a nickel film 5a that protects copper against oxidation, and a gold film 6a where an electronic part is mounted are deposited on the surface of the board 1 through evaporation, sputtering, ion plating or the like. Thereafter, the rear surface of the board 1 is coated with a resistive film 2 a chrome film 3b, a copper film 4b, a nickel film 5b, and a gold film 6b the same as the front surface, and a prescribed pattern is provided in the board 1 through a photoengraving technique for the formation of a thin film circuit board 7.

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 thin film circuit board used as a board for mounting electronic components to form a high-frequency circuit.

[0002]

2. Description of the Related Art Thin-film circuit boards containing 99.5% or more of alumina can form a fine circuit pattern with high precision on a material having a small coefficient of thermal expansion. It is used for In particular, it is widely used as a thin film hybrid IC for microwave circuits because it can be used as a dielectric in a microwave band and can be directly mounted on a silicon chip.

FIG. 3 is a diagram showing a film configuration of a conventional thin film circuit, and FIG. 4 is a diagram showing a cross section of the circuit before mounting a conventional electronic circuit. In FIG. 3, a substrate containing 99.5% alumina, which has no circuit connecting the circuit pattern on the front surface and the conductive surface on the back surface, is washed with a conventional detergent, pure water, and isopropyl alcohol, and then the alumina substrate is removed. 1 and resistor 2, chromium layers 3a and 3b for improving the adhesion of copper as a conductor film, and a part of copper layers 4a and 4b for securing high-frequency characteristics are deposited, sputtered, and ion plated. And nickel layers 5a and 5b for preventing oxidation of the remaining copper and copper, and gold layers 6a and 6b for securing wire bonding and ribbon bonding in the mounting of electronic components. It has been formed by plating, vapor deposition, sputtering, ion plating, or the like.

In FIG. 4, a resist having a required pattern is further arranged, and the thin film circuit board 7 is formed by sputtering or wet etching by a conventional method.

The above-mentioned conventional thin film circuit board comprises a film structure which has undergone the above-described manufacturing process, a conductor circuit and a resistor circuit which are etched, and a connection with the back surface is made by wire bonding, ribbon bonding or the like made of a gold material. Circuit board.

[0006]

The above-mentioned thin-film circuit board 7 requires an electrical connection between the front surface and the back surface of the substrate on which high-frequency circuits and the like are formed by wire bonding or ribbon bonding. However, the reliability of the electrical connection is lacking due to the workability associated with the connection, and the space required for the connection is required.

[0007] In addition, cleaning by a conventional method for forming a resistive film or a conductive film on an alumina substrate becomes a breeding ground for bacteria unless bacteria are eliminated by ultraviolet rays, and the adhesion of the resistive film or the conductive film due to the adhesion of bacteria is improved. There was a significant risk of damage. For this reason, it becomes necessary to add a filter using ultraviolet light to the cleaning device.However, since the manufacturing of a thin-film circuit board generally uses ultraviolet light to form a protective film on an unetched portion, the cleaning device is separated from the thin-film circuit board manufacturing equipment and separated into a separate room. Had to be provided. For this reason, there is a risk that the substrate is contaminated when it is brought into a thin film circuit board manufacturing facility after the substrate is washed, and the adhesion between the substrate and a resistive film or a conductive film by vapor deposition, sputtering, ion plating or the like is impaired.

Further, a resistive film 2, chromium layers 3a and 3b to be conductor films, and portions of copper layers 4a and 4b are deposited on a substrate,
After being formed by sputtering, ion plating, etc., the remaining copper layers 4a and 4
b, the nickel layers 5a and 5b and the gold layers 6a and 6b are generally formed by wet plating.
Since it is as thin as about 00 Å, there is a danger that chromium and copper will be delaminated under the influence of the oxidation of the underlying chromium layers 3a and 3b through the copper pinball.

The present invention has been made to solve such a problem, and has as its object to obtain a thin-film circuit board having high connection reliability.

It is another object of the present invention to provide a thin film circuit board capable of removing bacteria which may adhere to a substrate during a cleaning process and forming a resistive film and a conductive film having good adhesion. It is.

According to the present invention, vapor deposition, sputtering and ion plating are performed on a resistive film and a part of chromium and copper on an alumina substrate, and vapor deposition and sputtering are performed when a part of the remaining copper and nickel and chromium are coated by wet plating. It is another object of the present invention to provide a thin film circuit board capable of adhering a film made by ion plating or the like to a film made by wet plating without impairing the adhesion.

[0012]

According to a first aspect of the present invention, there is provided a method of manufacturing a thin film circuit board, wherein a through hole penetrating from one surface to the other surface of a substrate containing alumina as a main component is formed obliquely to the substrate surface. And a second step of forming a resistive film and a conductive film of the substrate on both surfaces of the substrate by vapor deposition, sputtering, or ion plating after the first process.

A method of manufacturing a thin film circuit board according to a second aspect of the present invention includes a first step of forming a through hole extending from one surface of the substrate containing alumina as a main component to the other surface in an oblique direction to the substrate surface. After the first step, a second step of immersing the substrate in sulfuric acid in a concentration range of 1.00 to 1.50 mol and washing with water;
A third step of immersion in hydrofluoric acid within a concentration range of 1 mol to 3.03 mol, and after the third step, a resistive film and a conductive film of the substrate on both surfaces of the substrate by vapor deposition, sputtering or ion plating. Forming a fourth step.

According to a third aspect of the present invention, there is provided a method of manufacturing a thin-film circuit board, comprising: a first step of forming a through-hole penetrating from one surface to the other surface of an alumina-based substrate in an oblique direction with respect to the substrate surface; After the first step, a second step of immersing the substrate in sulfuric acid in a concentration range of 1.00 to 1.50 mol and washing with water;
A third step of dipping in a concentration of 1 mol to 3.03 mol of hydrofluoric acid, and after the third step, a resistive film of the substrate, chromium and chromium are deposited on both sides of the substrate by vapor deposition, sputtering or ion plating. The substrate on which the copper conductor film is formed is subjected to cathodic electrolysis base adjustment in a solution obtained by adding 0.2 mol of potassium nickel cyanide to a potassium cyanide solution within a concentration range of 0.62 mol. And a fifth step of coating the remaining conductive film by wet plating after the fourth step.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a thin film circuit board, wherein, in the first step, a through hole is formed on one surface of the substrate and the thickness of the substrate or the thickness of the substrate or more on the other surface of the substrate. It is formed in an oblique direction that has been translated.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 1 and 2 are cross-sectional views of an alumina substrate and a thin-film circuit board using the alumina substrate according to the first embodiment of the present invention. In the figure, 1 is 9
A substrate containing 9.5% or more of alumina, and an oblique through hole (through hole) 8 penetrating from the front surface to the back surface of the substrate.
Is provided. At this time, the through hole 8 is provided as an oblique through hole 8 in which the surface of the substrate 1 and the thickness of the substrate or the thickness of the substrate or more are moved in parallel to the back of the substrate.

Next, as shown in FIG. 2, from the surface of the substrate 1, a resistive film 2 such as tantalum nitride, chromium 3a for improving the adhesion between the substrate and the conductive film, copper 4a for ensuring high frequency characteristics, and oxidation of copper are removed. After coating nickel 5a for prevention and gold 6a for mounting electronic components by vapor deposition, sputtering, ion plating or the like, the back surface of the substrate 1 is made of the resistive film 2, chrome 3b, copper 4b, nickel 5b,
The thin film circuit board 7 can be formed by coating gold 6b and etching it into a required pattern by photomechanical technology.

Embodiment 2 FIG. In the second embodiment of the present invention, the substrate having the oblique through-hole provided in FIG.
After being immersed in sulfuric acid in the concentration range of 00 to 1.5 mol and washed with water, it is immersed in hydrofluoric acid in the concentration range of 1.01 to 3.03 mol for washing. Washed substrate 1
Alumina substrate 1 containing 99.5% or more in which the adhesion between the substrate and the resistive film and the conductive film is improved by using
Can be used as the thin film circuit 7. Here, the upper limits of the concentrations of sulfuric acid and hydrofluoric acid are set because the resist 9 having the required pattern shown in FIG. 2 used for forming the resistive film and the conductive film and etching by photolithography is coated and etched. This is to prevent the resist remaining. The lower limit is set in the concentration range of sulfuric acid and hydrofluoric acid in order to exert the effect of cleaning the substrate.

Embodiment 3 In the third embodiment of the present invention, a resistive film 2 made of tantalum nitride or the like and the chromium layers 3a and 3b coated on the substrate 1 shown in FIG. In order to further improve the productivity of the substrate 1 coated with 1/5 of the copper layers 4a and 4b and the copper layers 4a and 4b, the nickel layers 5a and 5b, and the gold layers 6a and 6b, In order to obtain a conductor film having good adhesion. A resistance film 2 such as tantalum nitride is formed on a substrate 1 shown in FIG.
After １ ／ of the chromium layers 3a and 3b and １ ／ of the copper layers 4a and 4b are applied to the substrate, the copper layers 4a and 4b are activated with a solution of sodium or potassium cyanide or the like by a conventional method. Cathodic electrolysis is performed in a solution obtained by adding 0.2 mol of potassium nickel cyanide to a potassium cyanide solution having a molar concentration of 0.2 mol to remove a part of the oxide film of the chromium layers 3 a and 3 b through pinholes of the copper layers 4 a and 4 b. By activating 3a and 3b, it is possible to obtain a thin-film circuit board in which the adhesion to the post-process plating by wet processing is improved.

[0020]

According to the first and fourth aspects of the present invention, a through hole is formed by vapor deposition, sputtering, ion plating or the like by providing an oblique through hole connecting a front surface and a back surface to a substrate mainly composed of alumina. Enabled. By providing the through-hole conductor film, a thin-film circuit board having a through-hole with high connection reliability can be realized.

Further, according to the second and fourth aspects of the present invention, bacteria which may adhere to the substrate containing alumina as a main component in the cleaning process are eliminated to form a resistance film and a conductor film having good adhesion. I can do things. Further, it is possible to realize a thin film circuit board in which the resist used for forming a required pattern due to excessive etching of the substrate due to the cleaning does not remain and high-frequency characteristics are not impaired.

According to the third and fourth aspects of the present invention, a substrate mainly composed of alumina is subjected to vapor deposition, sputtering and ion plating up to a resistive film and a portion of chromium and copper to form a portion of copper and nickel and chromium. When coating by wet plating, a film formed by vapor deposition, sputtering, ion plating, or the like, and a film formed by wet plating are adhered to each other without impairing the adhesion, and a thin film circuit board can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of an alumina substrate according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a thin-film circuit board using an alumina substrate according to Embodiments 2 and 3 of the present invention.

FIG. 3 is a cross-sectional view showing a film configuration and the like of a conventional thin film circuit board using alumina.

FIG. 4 is a cross-sectional view of a conventional thin film circuit board using alumina.

[Explanation of symbols]

1 substrate, 2 resistive film, 3 chrome, 4 copper, 5 nickel, 6 gold, 7 thin film circuit board, 8 through hole, 9
Resist.

Claims (4)

[Claims] A first step of forming a through hole penetrating from one surface to the other surface of a substrate containing alumina as a main component in an oblique direction with respect to the substrate surface; and after the first step, both surfaces of the substrate. Forming a resistive film and a conductive film of the substrate by vapor deposition, sputtering or ion plating. 2. A first step in which a through hole penetrating from one surface to the other surface of a substrate containing alumina as a main component is formed in an oblique direction with respect to the substrate surface. A second step in which the substrate is immersed in sulfuric acid in a concentration range of 0.000 to 1.50 mol and washed with water, and after the second step, the substrate is cleaned in a concentration range of 1.01 to 3.03 mol. A third step of immersing in an acid; and a fourth step of forming a resistive film and a conductive film of the substrate on both sides of the substrate by vapor deposition, sputtering or ion plating after the third step. Of manufacturing a thin film circuit board. 3. A first step of forming a through hole penetrating from one surface of the substrate containing alumina as a main component to the other surface in an oblique direction with respect to the substrate surface, and after the first step, removing the substrate by one step. A second step in which the substrate is immersed in sulfuric acid in a concentration range of 0.000 to 1.50 mol and washed with water, and after the second step, the substrate is cleaned in a concentration range of 1.01 to 3.03 mol. A third step of immersing in acid, and after the third step, a substrate on which a resistive film of the substrate is formed on both surfaces of the substrate by sputtering or ion plating, and a conductive film of some of chromium and copper, A fourth step of adjusting the base of the cathodic electrolysis in a solution obtained by adding 0.2 mol of potassium potassium cyanide to a potassium cyanide solution within a concentration range of 0.62 mol, and a conductor remaining after the fourth step. Fifth process to coat the film by wet plating And a method of manufacturing a thin film circuit board. 4. The first step is characterized in that the through-hole is formed in an oblique direction in which one side of the substrate and a thickness of the substrate or a thickness greater than the thickness of the substrate are moved in parallel to the other surface of the substrate. The method for manufacturing a thin-film circuit board according to claim 1.