JP2534793B2 - Method for manufacturing insulating substrate for electrical insulation device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an insulating substrate for an electric device such as a hybrid integrated circuit.

[Prior Art] Conventionally, as an insulating substrate for an electric device such as a substrate for a hybrid integrated circuit, a ceramic substrate having an excellent electric insulating property is mainly used. However, ceramics have weak mechanical strength, especially bending strength, and cannot be processed. Further, the flatness of the ceramic substrate becomes worse as the substrate becomes larger, and thus it is difficult to make a large-sized substrate with ceramics.

Therefore, it has been proposed to use a metal substrate instead of the ceramic substrate. Japanese Patent Application No. 62-303756 (Japanese Patent Laid-Open No. 1-145887) added 10 to 30% by weight of chromium with 0.05 to 7% by weight of aluminum, 0.05 to 5% by weight of silicon, and 0.1 to 3% by weight of titanium. A metal substrate,
Disclosed is a method for producing an insulating substrate for an electric device, which comprises heat-treating in a reducing atmosphere containing hydrogen to form a film containing no iron oxide, and then forming a glass insulating layer on a part or all of this substrate. There is.

A known method for forming a glass insulating layer on a substrate for an electric device is a screen printing method. By this printing method,
When forming a glass insulating layer on a substrate having through-holes, first, a glass material that has been pasted or slurried is printed on the iron oxide-free film on one surface of the substrate, then leveled, and then the The glassy material is evacuated to move the glassy material into the through holes, so that the glassy material is coated in the through holes, and the glassy material is dried and fired. Then, the same process is repeated for the other surface of the substrate.

This method requires a vacuuming process of the vitreous material in order to coat the glass insulating layer on the inner wall of the through hole of the substrate, and when this process is difficult due to the diameter size and position of the through hole. There is. Further, the insulating substrate obtained by this method has a problem that the glass thickness is 40 μm and the withstand voltage of the through hole is as low as about 500 V at maximum.

Therefore, the present inventor has focused on the electrophoresis method. However, the electrophoresis method has a problem that it cannot work effectively unless the substrate is electrically conductive. In this case, the metal surface is generally plated with Ni.

[Technical Problem to be Solved by the Invention] The present invention has been made based on the above circumstances, and its purpose is to focus on the fact that the BA film has conductivity, and to consider the inner wall of the through hole of the substrate. Another object of the present invention is to provide a method capable of coating a glass insulator with a simple process and having a high withstand voltage of the through hole portion of the obtained insulating substrate.

[Means and Actions for Solving the Problems] The method for producing an insulating substrate for an electrical insulating device according to the present invention is performed by an alloy base consisting of 10 to 30% by weight of chromium and the balance iron and inevitable impurities, 10 to 30% by weight of chromium and 0.05% of aluminum. Alloy base consisting of ~ 7% by weight and balance iron and unavoidable impurities, chromium 10 to 30% by weight, silicon 0.05 to 5% by weight and alloy base consisting of balance iron and unavoidable impurities or chromium 10 to 30
% By weight, 0.05 to 7% by weight of aluminum and 0.1 of titanium
An alloy substrate consisting of ˜3% by weight and the balance iron and unavoidable impurities is heat-treated in a reducing atmosphere containing hydrogen at a temperature below the dew point at which iron oxide decomposes into iron and oxygen. The method includes a step of forming a film containing no oxide and a step of forming a glass insulating layer on at least a part of the film formed on the metal substrate by an electrophoretic method.

In the present invention, first, the metal substrate 1 is prepared. A suitable metal substrate 1 should have excellent workability, corrosion resistance, and heat resistance, and its composition is based on an alloy consisting of 10 to 30% by weight of chromium, the balance iron and inevitable impurities. .
This composition contains 0.05 to 7% by weight of aluminum or 0.
It may be an alloy further added with 05 to 5% by weight. Chromium 10 to 30% by weight, aluminum 0.05 to 7% by weight, and titanium
An alloy containing 0.1 to 3% by weight and the balance iron and inevitable impurities may be used. Furthermore, chromium is 10-30% by weight and nickel 6-
An alloy composed of 20% by weight and the balance iron and inevitable impurities may be used. The reason why the addition range of chromium in these alloys is set to the above range is that the above effect is not exhibited when the content is too small, and the workability of the material is deteriorated when the content is too large. The same applies to aluminum, silicon, titanium, and nickel. The metal base has almost no influence on the effect of the present invention even if the metallurgical structure is different, and therefore the metallurgical structure is not particularly limited. For example, a rolled structure or an annealed structure is effective.

Then, the metal substrate thus prepared is heat-treated in a reducing atmosphere containing hydrogen to form a coating 2 containing no iron oxide on the surface of the metal substrate, which does not deteriorate the conductivity. The reducing atmosphere containing hydrogen is, for example, a mixed atmosphere of hydrogen and nitrogen formed by decomposition of ammonia,
In addition, the heat treatment is performed below the dew point at which iron oxide decomposes into iron and nitrogen. The iron oxide-free coating obtained by this heat treatment is a so-called BA coating: bright annealing (Bright A
nnealing: commonly known as BA), which is a semiconducting film that does not contain iron oxides, and in some cases does not contain chromium oxides, even though the metal substrate is an iron-chromium alloy. In addition, it is made of an oxide having a low dissociation degree of oxygen partial pressure, such as aluminum oxide. The adhesion between this film and the glassy insulating layer is better than the adhesion between the metal substrate and the glassy insulating layer, and as a result, the adhesion between the metal substrate and the glassy insulating layer, especially heating at high temperature. It is possible to improve the adhesiveness when repeated. The present inventors presume that such excellent adhesion properties are due to the fact that the coating (oxide) has a high degree of denseness and that the iron content does not diffuse from the metal substrate into the glass layer. In order to decompose iron oxide into iron and oxygen, that is, to prevent the film from containing iron oxide,
The dew point of the reducing atmosphere is preferably −20 ° C. or lower, particularly preferably −40 ° C. or lower. By heat treatment at such a low dew point, the film formed is preferable because it can have a structure with a large amount of amorphous and less crystalline. The film is made amorphous by controlling the components of the metal substrate, the atmosphere during film formation, the cooling rate after film formation, and the heat treatment temperature. The heating temperature is preferably 500 to 1200 ° C, particularly preferably 800 to 900 ° C. The treatment time may be short, and it is important that the temperature reaches a predetermined temperature. However, the high temperature of the metal substrate,
For example, if the material is exposed to a temperature of 900 ° C or higher for a long time, the workability of the material deteriorates. The film thus formed in the reducing atmosphere has a thickness of 100 to 200Å, does not have an insulating property, and has a semiconductor-like electrical conductivity.

Then, a glass insulating layer 3 is formed on a part or the whole of this film by an electrophoretic method. Here, since the above film has a semiconductor-like electrical conductivity, the electrophoretic method can be effectively applied. In particular, the inner wall of the through hole of the metal substrate can be well covered with the glass insulating layer.

When the substrate is small, it is possible to form the glass insulating layer only by the electrophoretic method, but when the substrate is large, the glass insulating layer is formed on the inner wall of the through hole by the electrophoretic method, and the other portions are formed. For, it is efficient to use a screen printing method for coating.

[Example] A metal base (25.4 m) having a thickness of 0.4 mm, which is composed of 15% by weight of chromium, 4% by weight of aluminum, the balance iron and inevitable impurities.
m × 25.4 mm) was prepared and heated in a mixed atmosphere of 75% by volume of hydrogen and 25% by volume of nitrogen at a dew point of −40 ° C. and a temperature of 870 ° C. for 30 seconds to form a BA film on the surface of the metal substrate. . The thickness of this film was about 200Å, and it had a dense amorphous structure mainly composed of aluminum oxide without iron and iron oxide.

Also, a glass suspension was prepared. First, a crystallized glass (GA-30: trade name) manufactured by Nippon Electric Glass Co., Ltd. was prepared. 200 g of this crystallized glass was wet-ground with a 2-ball mill for 24 hours together with 500 cc of isopropyl alcohol, and finely ground to an average particle size of 2 to 3 μm to obtain a slurry. The slurry thus obtained was mixed with a dispersant to prepare a glass suspension.

Next, a stirrer is arranged at the bottom of the electrodeposition tank, counter electrodes are arranged on both sides of the tank, the glass suspension is placed therein, and a metal substrate having the BA film formed thereon is placed between the counter electrodes. (The distance between the metal substrate and the counter electrode: 15 to 20 mm). DC voltage of 100 to 300 V is applied for 1 minute with the metal base being negative and the counter electrode being positive, and then the metal base is raised at a pulling rate of 1 to 2 mm / sec with the voltage between the metal base and the counter electrode being 0. And pulled from the glass suspension. After drying this metal substrate, it was fired in the atmosphere at 850 ° C. for 10 minutes to manufacture an insulating substrate of the present invention (thickness of crystalline glass insulating layer: 40 μm).

When the inner wall of the through hole of the substrate obtained by this method was observed, it was found that all the inner wall was covered with the glass insulating layer.

Also, when the withstand voltage of the through hole was measured, it was 1K.
It was V or higher. Furthermore, as a result of measuring the surface roughness, 0.3
~ 0.4Raμm, conductor paste on this insulating substrate,
It was possible to screen print circuits, resistors, etc. satisfactorily.

Comparative Example 1 An insulating substrate was manufactured under the same conditions as those of the above-mentioned Examples except that the glass insulating layer was formed by the screen printing method. As a result of measuring the withstand voltage of the through hole, it was only 500 V at maximum.

Comparative Example 2 An iron oxide-free film was formed on the surface of a metal substrate, and then a tempering treatment was performed to form an insulating film. On the other hand, a glass insulating layer was formed under the same conditions as those of the above-described Examples to insulate the film. The substrate was manufactured.

Even if a conductor paste, a circuit, a resistor, etc. were screen-printed on this insulating substrate, they could not be formed.

Experimental Example Next, a circuit was formed on the substrate of the example and the substrate of the comparative example 2, and the circuit characteristics of the conductor and the resistance were examined. Table 1 shows the results.

[Effects of the Invention] As described above, since the film obtained in the present invention is a film that does not become an insulator, a glass insulating layer can be formed on the film by an electrophoresis method. As a result, no plating process is required even if the electrophoretic method is used, and the glass insulating layer is well formed on the inner wall portion of the through hole of the metal substrate which could not be covered by the conventional screen method. Can be coated. Moreover, the surface of the glass insulating layer has the surface smoothness necessary for forming a thick film circuit. Further, even if there is a metal exposed portion, it has strong corrosion resistance and heat resistance and can withstand re-baking.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an insulating substrate according to the present invention. 1 ... Metal substrate, 2 ... Film, 3 ... Glass insulating layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C25D 13/20 C25D 13/20 C H05K 3/44 H05K 3/44 C

Claims (4)

(57) [Claims] 1. An alloy substrate consisting of 10 to 30% by weight of chromium and the balance of iron and unavoidable impurities is heat-treated in a reducing atmosphere containing hydrogen at a temperature below the dew point at which iron oxide decomposes into iron and oxygen. Electrical insulation comprising a step of forming a film containing no iron oxide on the surface of the metal substrate and a step of forming a glass insulating layer on at least a part of the film formed on the alloy substrate by an electrophoretic method. Manufacturing method of insulating substrate for device. 2. Chromium 10 to 30% by weight and aluminum 0.05 to
An alloy substrate consisting of 7% by weight and the balance iron and unavoidable impurities was heat-treated in a reducing atmosphere containing hydrogen at a temperature not higher than the dew point at which iron oxide decomposes into iron and oxygen.
Manufacture of an insulating substrate for an electrical insulating device, which comprises a step of forming a film containing no iron oxide and a step of forming a glass insulating layer on at least a part of the film formed on the alloy substrate by an electrophoretic method. Method. 3. An alloy substrate comprising 10 to 30% by weight of chromium, 0.05 to 5% by weight of silicon, the balance iron and inevitable impurities,
Heat treatment in a reducing atmosphere containing hydrogen at a temperature below the dew point at which iron oxide decomposes into iron and oxygen to form a film containing no iron oxide on the surface of the metal substrate, and forming on this alloy substrate And a step of forming a glass insulating layer on at least a part of the formed film by an electrophoretic method, the method for producing an insulating substrate for an electric insulating device. 4. Chromium 10 to 30% by weight and aluminum 0.05 to
An alloy substrate consisting of 7% by weight and 0.1 to 3% by weight of titanium, and the balance of iron and unavoidable impurities is heat-treated in a reducing atmosphere containing hydrogen at a temperature below the dew point at which iron oxide decomposes into iron and oxygen, An electrical insulating device comprising a step of forming a coating film containing no iron oxide on the surface of a metal substrate and a step of forming a glass insulating layer on at least a part of the coating film formed on the alloy substrate by an electrophoretic method. Method for manufacturing insulating substrate.