JPS63285941A - Electronic circuit substrate, manufacture of said substrate and electronic circuit device - Google Patents

Abstract

PURPOSE:To improve heat-dissipating characteristics by respectively giving the joint surfaces of an electrical insulating layer and a high thermal conductive substrate concentration gradients in which concentration is reduced toward the member sides of the other parties. CONSTITUTION:The thin layer of an electrical insulating layer is formed directly onto a high thermal conductive substrate, and the electrical insulating layer is bonded by a mixed layer with the material of the high thermal conductive substrate. The electrical insulating layer is shaped by combining the formation of an evaporating layer through the evaporation method or sputtering method of a metal and the implantation of reactive ion species shaping the electrical insulating layer by a reaction with the evaporating layer of nitrogen ions or oxygen ions or the like. When a metallic layer is formed onto the electrical insulating layer, an inert gas such as argon gas, helium gas, nitrogen gas or the like as nonreactive ion species not reacted with a metallic-layer forming metal is used. Accordingly, each boundary of the electrical insulating layer on the high thermal conductive substrate shaped and the metallic layer on the electrical insulating layer is not made distinct, and both layers have concentration gradients and are made dense, thus acquiring an electrical circuit substrate having excellent adhesion and electrical insulating properties and small thermal resistance.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an electrically insulating layer formed on a highly thermally conductive substrate,
The present invention relates to an electronic circuit board in which a metal layer is formed on an electrically insulating layer, a manufacturing method thereof, and an electronic circuit device.

[Conventional technology]

BACKGROUND ART Conventionally, an electrically insulating layer made of a ceramic plate such as a fired alumina plate is bonded to an elevated conductive substrate and used as an electronic circuit board for an insulated element or the like. This electrically insulating layer serves to provide electrical insulation with the highly thermally conductive substrate and to transmit heat generated from elements or circuits to the highly thermally conductive substrate.

In order to fully exhibit circuit element performance in electronic circuit components, it is desirable to reduce the thermal resistance of the electrical insulating layer as much as possible to improve heat dissipation characteristics. From this point of view, the thickness of the ceramic plate serving as the electrically insulating layer must be made as thin as possible within a range that provides the required electrical insulation resistance. However, as the thickness of fired ceramic plates decreases, their mechanical strength decreases, and even slight external forces during circuit manufacturing can cause cracks, which poses problems in terms of reliability. There is a limit, and in general, those of 0.25 to 1.0I are often used. On the other hand, when using fired ceramic plates, the bonding with a highly thermally conductive substrate is usually done by soldering, so the bonding surface must have a surface finish that increases thermal resistance and reduces defects such as pores. . Furthermore, ceramics have poor leakage with solder, and it is difficult to directly bond them to a highly thermally conductive substrate with solder.1 The manufacturing process is complicated, such as metallizing treatment usually applied to the ceramic plate. Furthermore, since the ceramic plate and the highly thermally conductive substrate are joined by solder, the bonding strength is low, and there is also a concern that the ceramic plate may peel or crack due to the difference in thermal expansion between the ceramic plate and the highly thermally conductive substrate.

On the other hand, the shape or withstand voltage of the electrical insulating layer is selected depending on the intended use of the circuit, but when using a fired ceramic plate, it is not possible to manufacture it by arbitrarily changing its size, shape, thickness, etc. Because it is disadvantageous in terms of handling or price,
Currently, certain standard products are used.

On the other hand, when bonding conductors, electronic components, etc. to the electrically insulating layer, it is necessary to subject the ceramic plate to metallization treatment and to bond them with solder, which further complicates the manufacturing process and increases manufacturing costs.

Various proposals have been made in order to solve these current problems. There is a method of forming an electrically insulating layer. This method enables the formation of an electrically insulating layer directly on a highly thermally conductive substrate, which eliminates the need for soldering and reduces the number of man-hours.6 Furthermore, it is thinner than the conventional method of bonding a fired alumina plate to a highly thermally conductive substrate. An electrical insulating layer can be formed and thermal resistance can be reduced to some extent.

However, in recent years, as the output of electronic circuit components has increased, there has been an increasing demand for electrical insulating layers with low thermal resistance and thinner integrated circuits. This is difficult, and there are some cases where even this technology cannot be used due to thermal resistance caused by pores, etc.

[Problems to be Solved by the Invention] The above-mentioned conventional techniques are unable to meet the demands for higher output and thinner devices. That is, as the output increases, the amount of heat generated by elements or circuits increases, and it is necessary to improve heat dissipation characteristics, but the heat dissipation characteristics have been low.

As a countermeasure, it is best to reduce the thickness of the electrical insulating layer to the extent that electrical insulation is maintained, and to form one layer densely to reduce thermal resistance. should be in an atomic bonded state rather than a mechanical bonded state. In other words, it is preferable that the boundaries are not clear and that there are no boundaries that impede heat transfer. Further, it is preferable that a dense layer without defects such as pores that increase thermal resistance be formed between the highly thermally conductive substrate and the electrical insulating layer and within the electrical insulating layer.

On the other hand, when manufacturing an electronic circuit board, it is desirable to keep the temperature as low as possible. For example, it is necessary to raise the temperature when bonding or forming electrical insulating layers, metallizing processing of electrical insulating layers, and bonding electronic circuit components and conductors.
It is necessary to keep this temperature as low as possible. This is because when processed at high temperatures, the electrical insulating layer (ceramic) and the highly thermally conductive substrate have different coefficients of thermal expansion, which may cause peeling or cracking during heating or cooling.

In addition, deformation is likely to occur, and the surface must be flattened through post-processing to bond electronic components and conductors. When forming a thin metal layer on an electrically insulating layer by the plasma spraying method described above, it is necessary to raise the temperature to improve adhesion, and some degree of deformation is unavoidable. Furthermore, since ceramic powder is used, a large amount of man-hours and technology are required to make the shape and size of the zero particles constant, since the thickness of the electrically insulating layer is also influenced by the particle diameter.

Therefore, since ceramic powder with a somewhat non-uniform particle size is used, the layer thickness will also be non-uniform, and if the particle size is not made larger than a certain level, the particle size flow during thermal spraying may deteriorate. Some particles have a diameter of several tens of micrometers, and because these particles are piled up to form a layer, it is difficult to reduce the thickness of the electrical insulation layer, and thermal spraying eliminates all pores. It is extremely difficult to do so.1゜An object of the present invention is to be able to form a dense electrical insulating layer with no clear boundary between the highly thermally conductive substrate and the desired portion of the highly thermally conductive substrate. An object of the present invention is to provide an electronic circuit board and a method for manufacturing the same which have excellent characteristics and can meet the demands for higher output of electronic components.

Another object of the present invention is to form a metal layer in a desired portion of the electrical insulating layer that has no clear boundary with the electrical insulating material, has excellent adhesion, allows direct bonding of electronic components or conductors, and has excellent heat dissipation properties. An object of the present invention is to provide an electronic circuit board and a method for manufacturing the same.

Yet another object of the invention is a metal layer and an electrically insulating layer.

Another object of the present invention is to provide an electronic circuit device that has excellent heat dissipation characteristics for heat generated from electronic components disposed on a metal layer by making the boundaries between an electrically insulating layer and a highly thermally conductive substrate unclear.

[Means/effects for solving the problem] The first invention (Claim 1) provides an electronic circuit board in which an electrically insulating layer is formed on a highly thermally conductive substrate. This is an electronic circuit board in which the substrate has a concentration gradient in which the concentration decreases toward the other member at its bonding surface.

As a result, there is no clear boundary between the electrically insulating layer and the highly thermally conductive substrate, and the material changes continuously from one side to the other, reducing thermal resistance.

The second invention (Claim 3) includes forming a vapor deposition layer on a highly thermally conductive substrate by vapor deposition or sputtering;
This is a method of manufacturing an electronic circuit board in which an electrically insulating layer is formed on a highly thermally conductive substrate by simultaneously or alternately implanting reactive ion species that generate an electrically insulating layer by reaction with the vaporized layer.

Since the vapor deposited layer is formed by reducing the particle size by vapor deposition or sputtering, an extremely thin layer can be formed without voids.

In addition, the injection of reactive ion species generates heat and transforms the vapor deposited layer into an electrically insulating layer such as ceramics, and the material components are sputtered on the surface of the highly thermally conductive substrate due to the kinetic energy possessed by the implanted ion species, so that the vapor deposition layer side The boundary between the electrically insulating layer and the highly thermally conductive substrate becomes unclear as a whole. In other words, it becomes a mixed layer state.

A third invention (Claim 5) provides an electronic circuit board in which an electrically insulating layer is formed on a highly thermally conductive substrate, and a metal layer is formed on the electrically insulating layer. The electronic circuit board has a concentration gradient in which the concentration decreases toward the other member at the bonding surface.

As a result, there is no clear boundary between the metal layer and the electrically insulating layer, and the material changes continuously from one to the other, reducing thermal resistance.

The fourth invention (Claim 8) is to form a metal layer by vapor deposition or sputtering on an electrical insulating layer formed on a highly thermally conductive substrate, and to add a non-reactive material to the metal layer that does not react with the metal. This is a method of manufacturing an electronic circuit board in which implantation of reactive ion species is performed simultaneously or alternately.

Since the metal layer is formed by reducing the particle size by vapor deposition or sputtering, it is possible to form an extremely thin metal layer without voids. In addition, due to the implantation of non-reactive ion species, the material components are sputtered on the surface of the electrically insulating layer due to the kinetic energy of the non-reactive ion species and ejected to the metal layer side, making the boundary between the metal layer and the electrically insulating layer unclear as a whole. . In other words, it becomes a mixed layer state.

A fifth invention (Claim 10) provides that an electrical insulating layer is formed on a highly thermally conductive substrate, a metal layer is formed on the electrically insulating layer, and the electrically insulating layer and the highly thermally conductive substrate are bonded together. The metal layer and the electrical insulating layer each have a concentration gradient in which the concentration decreases toward the other member at the bonding surface thereof, and the metal layer and the electrical insulating layer each have a concentration gradient in which the concentration decreases toward the other member at the bonding surface thereof. However, it is an electronic circuit device in which electronic components and necessary conductors are arranged on this metal layer.

As a result, when increasing the output of electronic components, heat can be released from the metal layer to the highly thermally conductive substrate via the electrically insulating substrate because each boundary is a continuous mixed layer.

〔Example〕

The electronic circuit board of the present invention has a thin electrically insulating layer formed directly on a highly thermally conductive substrate, and this electrically insulating layer is bonded by a mixed layer with the material of the highly thermally conductive substrate. The method for forming the electrically insulating layer is a combination of forming a vaporized layer by metal vapor deposition or sputtering and implanting reactive ion species such as nitrogen ions or oxygen ions that form the electrically insulating layer by reacting with the vaporized layer. It is formed. In other words, in the electronic circuit board of the present invention, the electrical insulating layer has a concentration gradient increasing from the high thermal conductive substrate side to the electrical insulating layer side, and has no clear boundary with the high thermal conductive substrate. ing. Further, since the electrical insulating layer is formed by a combination of a vapor deposition method or a sputtering method and a one-reaction ion implantation method, the grain size can be reduced and a dense and thin layer can be formed. Therefore, it has excellent adhesion with high thermal conductivity substrates,
It has extremely low thermal resistance and can handle high output electronic components.

The method for forming an electrically insulating layer is to form a vapor deposited layer using a vapor deposition method or a sputtering method while applying nitrogen ions or oxygen ions to a desired portion of a highly thermally conductive substrate. inject. That is, accelerated nitrogen ions or oxygen ions are injected into a highly thermally conductive substrate and a vapor deposited layer to generate heat, and the vapor deposited layer reacts with the implanted ions to form a nitride or oxide that becomes an electrically insulating layer. . At this time, since the highly thermally conductive substrate is injected with reactive ion species, it is sputtered and sputtered, and is mixed with the deposited metal particles to form a mixed layer. However, this phenomenon occurs only at the initial stage of film formation, and as the film thickness increases, reactive ion species are no longer implanted into the highly thermally conductive substrate.
Sputtering of highly thermally conductive substrates no longer occurs. Depending on the accelerating voltage of the reactive ion species, the formed nitride or oxide may be sputtered, so it is preferable to set the accelerating voltage to a high level of 5 < 5 when forming the mixed layer, and then accelerate once the mixed layer is formed. It is better to lower the voltage to avoid sputtering. Further, although it depends on the accelerating voltage of the reactive ion species and the thickness of the deposited layer, similar results can be obtained even if the formation of the deposited layer and the implantation of the reactive ion species are performed alternately.

However, if the thickness of the deposited layer is thick and the accelerating voltage is low, no mixed layer is formed and the adhesion is extremely weak. therefore,
It is necessary to appropriately select the accelerating voltage and the thickness of the deposited layer.

Regarding the film quality of the electrical insulating layer, the vapor deposited particles or sputtered particles are very fine, and since these particles are piled up to form a layer, the five layers are extremely dense. Therefore, an electrical insulating layer with low thermal resistance without intervening holes or the like can be obtained.

In addition, since the single particle size is small, the thickness of the electrical insulating layer can be freely adjusted according to human orders, and the film thickness can be formed as desired.

On the other hand, when forming a metal layer on an electrically insulating layer, an inert gas such as argon gas, helium gas, or nitrogen gas, which is a non-reactive ion species that does not react with the metal forming the metal layer, is used. Metal layer formation If a gas that reacts with the metal is used, a compound layer will be formed, which is undesirable.Also, the metal layer may be formed by vapor deposition or sputtering of a pure metal or an alloy, or by using a mixture of two or more types of metal. Similar results can be obtained by simultaneously forming metal by vapor deposition or sputtering. At this time, due to the implantation of non-reactive ion species, sputtering occurs on the electrical insulating layer due to the kinetic energy of the non-reactive ion species, which themselves fly out as particles, resulting in a mixed layer in which the material of the electrical insulating layer is mixed into the metal layer. The boundary between the two becomes unclear. The concentration gradient is such that the concentration of the metal layer and the electrically insulating layer decreases toward the other member at the bonding surface thereof.

Although the electrical insulating layer and the metal layer are formed by the method described above, the kinetic energy of accelerated ions is converted into thermal energy and the heat generated is only in the extreme surface layer, so that the highly thermally conductive substrate may be deteriorated. There is no deformation, and there is very little deformation. If the temperature should rise, this can be solved by cooling the highly thermally conductive substrate or by intermittent ion implantation. Cooling or intermittent implantation has no effect on insulator formation.

This is a metal layer formed on an electrical insulating layer, and high melting point brazing filler metal requires high temperatures when bonding electronic components and conductors, which is undesirable as it may cause functional damage or deformation of the electronic components. therefore.

A low melting point brazing filler metal, that is, a soft brazing filler metal is preferable, and a low melting point brazing filler metal having good leakage properties with conductors such as Pb-5n alloy (solder) and electronic parts is particularly desirable.

On the other hand, nitrides or oxides, which are electrically insulating layers formed on highly thermally conductive substrates, are thermally conductive.

From the viewpoint of electrical insulation, aluminum nitride, aluminum oxide, silicon nitride, boron nitride, etc. are particularly preferred. However, the material is not limited to the above-mentioned nitrides and oxides, and any material having excellent thermal conductivity and electrical insulation may be used.

The electrical insulating layer on the highly thermally conductive substrate formed by the method described above and the metal layer on the electrical insulating layer have indistinct boundaries and concentration gradients, and the layers are dense, so the adhesion and It has excellent electrical insulation and low thermal resistance, fully satisfying the requirements for electronic circuit boards. That is, in the electronic circuit board of the present invention, the boundaries between the highly thermally conductive substrate and the electrical insulating layer, which increase thermal resistance, and the electrical insulating layer and the metal layer are not clear. If there is no clear boundary, heat can be transferred smoothly to the highly thermally conductive substrate, but if there is a clear boundary, the boundary becomes an obstacle to heat transfer and heat cannot be dissipated smoothly to the highly thermally conductive substrate. can accumulate and cause damage to electronic components, etc.

Furthermore, the electrical insulating layer of the present invention has no intervening pores that would impede thermal resistance, and since it is a dense layer, heat can be smoothly transferred to the highly thermally conductive substrate and there is no accumulation of heat. Furthermore, the film thickness can be adjusted as required for electrical insulation, thermal resistance can be reduced, and it can also contribute to thinning of electronic circuit boards. Furthermore, since it has excellent adhesion, there is no fear of peeling when forming a single layer or when bonding electronic components or conductors.

As described above, the electronic circuit board of the present invention satisfies the requirements for an electronic circuit board, has extremely low thermal resistance, and can sufficiently handle high output.

Miyu Example 1 Oxygen-free copper plate (thickness 0, 8 rm
.

30 x 30 mm) was attached to a water-cooled target in a vacuum container, and after evacuating the inside of the container to 10-B Torr or less, aluminum and boron were placed on a highly thermally conductive substrate.

Implant nitrogen ions while depositing silicon, aluminum nitride, and boron nitride onto the substrate, respectively.

A silicon nitride film was formed to a thickness of 50 μm. The film forming conditions were a deposition rate of 11 people/s, and an acceleration voltage of 20 kV.

Current: 0. LA, nitrogen ion implantation amount: 2×10′δ ions/d. Next, on each of the thin layers of nitride electrical insulators formed in this way, areas other than the shapes corresponding to the electronic components and conductors are masked, and the same process as when forming the electrical insulating layer is applied. Argon ions were implanted while depositing the Pb-Sn alloy using the method. As a result, a Pb-Sn alloy metal layer was formed in the portions that were not masked.

The film thickness is 25 μm. Electronic components and conductors were placed on the Pb-Sn alloy thin film of the substrate created in this way.
The electronic circuit device shown in FIG. 1 was fabricated by heating to 00° C. for bonding, and then connecting lead wires by a known method. For comparison, FIG. 2 shows a conventional electronic circuit device in which an electrical insulating layer of AQzOs is formed by thermal spraying. The thickness of this electrically insulating layer is 0.1 mm. In the electronic circuit device of the present invention, an electrical insulating layer 2 is formed on a highly thermally conductive substrate 1 by a combination of forming a vapor deposited layer of metal or the like and implanting nitrogen ions. Sn alloy metal layer 3
is formed. 4 is a metallizing layer, 5 is a semiconductor element (Si element), and 6 is a Cu lead wire. In the comparative example, a metallizing layer 4 is formed on the electrical insulating layer 2 because the solder 3 cannot be directly bonded thereto. Since the highly thermally conductive substrate 1 and the electrical insulating layer 2 cannot be directly bonded, a metallizing layer 4 is formed. The adhesion between the highly thermally conductive substrate 1 and the electrical insulating layer 2 of the electronic circuit device shown in FIG. 1 and the conventional electronic circuit device shown in FIG. 2 was investigated. Table 1 shows the results, and in the comparative example, 1, 5 to 3, 0 kg/
Although the adhesion force was about 2 m2, the adhesion force of the electronic circuit devices of the present invention was all 7 kg/nu'' or more, showing extremely high adhesion force, and a highly reliable insulating layer 2 was obtained.

Table 1 also shows the results of analyzing the electrical insulating layer 2 of the conventional electronic circuit device and the electronic circuit device of the present invention down to the highly thermally conductive substrate 1 while digging in the thickness direction by Auger electron spectroscopy.
The results shown in the figure were obtained. That is, in the electronic circuit board of the present invention, the concentration of AQN, which is the electrical insulating layer 2, gradually decreases toward the highly thermally conductive substrate 1, and conversely, the concentration of copper, which is the base material of the substrate 1, gradually increases. There is. In comparison, the conventional one shows a rapid change. That is, it can be seen that in the electronic circuit board of the present invention, a mixed layer is formed on the bonding surface between the highly thermally conductive substrate and the electrical insulating layer. Therefore, since there is no clear boundary, the adhesion force also shows a high value. Furthermore, since the boundaries are not clear, it can be easily inferred that the heat dissipation properties are naturally excellent.

Experimental Example 2 Carbon steel (C content 0.06%) plate (4
Using the same method as in Experimental Example 1, oxygen ions were implanted while depositing aluminum to form an aluminum oxide layer of about 50 μm on the base material.

Next, as in Experimental Example 1, unnecessary portions were masked, and helium ions were implanted while copper was being deposited to form a metal layer of copper with a thickness of about 50 μm on the aluminum oxide layer.

Next, electronic components and lead wires were soldered using a known method to create an electronic circuit device. As a comparative example, an insulating layer of AQzOs was formed by the thermal spraying method in the same manner as in Experimental Example 1. Further, copper was thermally sprayed onto the A Q z Os insulating layer, and then electronic components and lead wires were soldered to create an electronic circuit device. As a result of measuring the adhesion strength between the insulating layer and the copper layer of the electronic circuit devices of the present invention and the conventional electronic circuit devices, the adhesion strength of the conventional device was 2 to 3 kg/IIfi2, while that of the present invention was 8.5 to 10 kg/1ff112. It showed extremely good adhesion.

In addition, as a result of measuring the thermal resistance of these electronic circuit boards,
While the conventional one had a temperature of 1.8°C/W, the one of the present invention had a temperature of 1.2°C/W, which was an improvement of about 33% compared to the conventional one. This is also considered to be because in the present invention, the boundary is a mixed layer.

Experimental Example 3 Fe-42%Ni alloy (30mm
x 30mm x 1.6mm) Similar to Experimental Example 1, aluminum was sputtered to form a film on the same substrate, while nitrogen ions were implanted to form an aluminum nitride layer of about 60 μm, and on top of that, Experimental Example 1 Similarly, a metal layer made of copper was formed by masking non-essential parts and implanting argon ions while sputtering copper. Next, electronic components and lead wires were soldered onto the copper layer by a known method to create an electronic circuit device. The withstand voltage of this electronic circuit device was determined to be 2000V or more. The withstand voltage required for general insulated elements or modules is 1500 V or more, and even a film thickness of about 60 μm can sufficiently withstand it.

Incidentally, the withstand voltage of A Q 20 s produced by the thermal spraying method is about 1500 V at 90 μm, indicating that the electronic circuit board of the present invention has a high withstand voltage even though it is thin. Therefore, when the same withstand voltage is required, the film thickness can be made thinner, and the demand for thinner thickness can be met.

As described above, the electronic circuit board of the present invention can be applied to semiconductor elements, resistors, capacitors, etc.

〔Effect of the invention〕

According to the first invention (Claim 1) and the third invention (Claim 5), the boundary is not clear and the material changes continuously from one side to the other, so the thermal resistance is small. Become. Therefore, heat dissipation characteristics can be improved.

According to the manufacturing methods of the second invention (Claim 3) and the fourth invention (Claim 8), it is possible to form a deposited layer with a small particle size, so it is easy to form an extremely thin layer without voids. This allows the overall thickness to be reduced. Furthermore, since sputtering occurs on the substrate side due to the kinetic energy of the implanted ion species, a continuous mixed layer with unclear boundaries can be easily formed. The mixed layer formed in this manner provides high adhesion between the two, and can also improve heat resistance properties. Furthermore, even if materials cannot be directly bonded to each other, they can be directly bonded using the method of the present invention, which eliminates the need for a conventional metallizing layer, thereby reducing the number of manufacturing steps and reducing costs.

According to the fifth invention (Claim 10), it is possible to sufficiently cope with the increase in the output of electronic components, and it is also possible to improve the reliability of the electronic circuit device.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of an electronic circuit device showing an embodiment of the present invention, Fig. 2 is a cross-sectional view of a conventional electronic circuit device, and Fig. 3 is a graph showing the results of Auger electron spectroscopy of the present invention and a comparative example. It is. 1... High thermal conductive substrate, 2... Electrical insulating layer, 3...
-Metal layer, 4...Metallizing layer, 5...Si element, 6...Cu lead wire.

Claims (1)

[Claims] 1. In an electronic circuit board in which an electrically insulating layer is formed on a highly thermally conductive substrate, the electrically insulating layer and the highly thermally conductive substrate each have a concentration that decreases toward the other member at their joint surfaces. An electronic circuit board characterized in that it has a decreasing concentration gradient. 2. The electronic circuit board according to claim 1, wherein the electrical insulating layer is made of aluminum nitride, aluminum oxide, silicon nitride, or boron nitride. 3. Forming a vapor deposited layer on a highly thermally conductive substrate by vapor deposition or sputtering, and implanting reactive ion species that generate an electrically insulating layer by reaction with the vapor deposited layer into the vapor deposited layer, either simultaneously or alternately. 1. A method of manufacturing an electronic circuit board, comprising forming an electrical insulating layer on a highly thermally conductive substrate. 4. The method of manufacturing an electronic circuit board according to claim 3, wherein the vapor deposited layer is made of aluminum, silicon, or boron, and the reactive ion species is nitrogen ions or oxygen ions. 5. In an electronic circuit board in which an electrically insulating layer is formed on a highly thermally conductive substrate and a metal layer is formed on this electrically insulating layer, the metal layer and the electrically insulating layer are each on the side of the other member at the bonding surface thereof. An electronic circuit board characterized by having a concentration gradient in which the concentration decreases in the direction of the substrate. 6. An electronic circuit board according to claim 5, in which the electrical insulating layer and the highly thermally conductive substrate each have a concentration gradient at their bonding surface where the concentration decreases toward the other member. 7. The electronic circuit board according to claim 5 or 6, wherein the metal layer is a soft brazing material. 8. Forming a metal layer by vapor deposition or sputtering on an electrical insulating layer formed on a highly thermally conductive substrate and implanting non-reactive ionic species that do not react with the metal layer into this metal layer, either simultaneously or alternately. 1. A method of manufacturing an electronic circuit board, characterized in that the method comprises: 9. The method of manufacturing an electronic circuit board according to claim 8, wherein the metal layer is a soft brazing material and the non-reactive ion species are argon ions, neon ions, xenon ions, or helium ions. 10. An electrically insulating layer is formed on a highly thermally conductive substrate, a metal layer is formed on this electrically insulating layer, and the electrically insulating layer and the highly thermally conductive substrate each face the other member at their joint surfaces. The metal layer and the electrical insulating layer each have a concentration gradient in which the concentration decreases toward the other member at the bonding surface thereof, and electronic components and necessary components are formed on the metal layer. An electronic circuit device equipped with conductors.