JP4595893B2 - Insulating film formation method - Google Patents

Description

  The present invention relates to an insulating film forming method in which an aerosol in which fine particles of an insulating material are dispersed in a gas is sprayed from a nozzle onto an object, and an insulating film made of the insulating material is formed on the surface of the object.

  Conventionally, when forming an insulating film made of an insulating material on the surface of a conductor (object) containing a metal as a main component, a film is formed by spraying an aerosol in which fine particles of an insulating material are dispersed in a gas from the nozzle onto the object. In some cases, a so-called aerosol deposition method is employed (see, for example, Patent Documents 1 to 5).

The aerosol deposition method is a film formation method in which a particulate raw material prepared in advance is mixed with a gas to form an aerosol, which is then sprayed onto an object through a nozzle in a reduced-pressure atmosphere to form a film, which is accelerated by gas transportation. It is considered that the kinetic energy of the raw material particles collides with the object to be converted into local thermal energy, thereby realizing the coupling between the object and the particles and between the particles.
JP 2001-181859 A Japanese Patent Laid-Open No. 2002-20878 JP 2002-320879 A JP 2003-247080 A JP 2003-251227 A

  By the way, in general, the thermal expansion coefficient differs greatly between the metal material constituting the object and the insulating material forming the insulating film. For this reason, there has been a problem that thermal stress is generated at the interface between the object and the insulating coating as the temperature changes, and the adhesion of the insulating coating is reduced.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an insulating film forming method that prevents a decrease in adhesive film adhesion due to thermal stress caused by a difference in thermal expansion coefficient between an object and an insulating material. It is to provide.

  In order to achieve the above object, the invention according to claim 1 sprays an aerosol, in which fine particles of an insulating material are dispersed in a gas, onto a target object from a nozzle, and forms an insulating film made of the insulating material on the surface of the target object. In the insulating film forming method to be formed, an inflow port through which the aerosol flows, an ejection port from which the aerosol is ejected, and a flow path that guides the aerosol that flows in from the inflow port to the ejection port, the flow path in contact with the aerosol The aerosol is sprayed onto the object using a nozzle that is coated on the surface with the same metal as the main component of the object with a predetermined thickness corresponding to the area of the insulating coating formed on the object surface. It is characterized by that.

  According to a second aspect of the present invention, in the first aspect of the invention, an aerosol in which fine particles of an insulating material are dispersed in a gas is sprayed from a nozzle onto an object, and an insulating film made of the insulating material is formed on the surface of the object. In the insulating film forming method, the nozzle body is provided with an inflow port through which the aerosol flows, an ejection port through which the aerosol is ejected, and a flow path for guiding the aerosol inflow from the inflow port to the ejection port. A metal block provided with a flow path communicating with a jet outlet is disposed at the tip of the main body, and the insulating coating is formed on the object surface by the same metal as the metal that is the main component of the object. It is characterized in that aerosol is sprayed onto an object using a nozzle formed in a predetermined dimension corresponding to the area.

  According to the first aspect of the present invention, the surface of the flow path of the nozzle through which the aerosol passes is scraped by the fine particles of the insulating material that passes at high speed, and the scraped metal particles are jetted onto the target object together with the fine particles of the insulating material. However, the amount of metal particles deposited on the surface of the target object decreases, and the amount of metal mixed in the insulating coating is the largest near the interface. When the distance from the interface decreases and the distance from the interface exceeds a predetermined distance, the metal is not mixed. As a result, since the same metal as the main component of the object is mixed in the interface between the insulating film and the object surface, the thermal expansion coefficient in the vicinity of the interface between the insulating film and the object is very close. Thus, the adhesion between the two can be improved, and further, since no metal is mixed in the vicinity of the surface of the insulating coating, it is possible to suppress a decrease in the insulating characteristics (insulation breakdown voltage) of the insulating coating.

  According to the second aspect of the invention, the metal block is scraped off on the surface of the flow path of the nozzle through which the aerosol passes by the fine particles of the insulating material passing at high speed, and the scraped metal particles are jetted onto the object to form the fine particles of the insulating material. At the same time, a film is formed on the surface of the object, but the amount of metal particles deposited on the surface of the object also decreases as the amount of metal particles scraped off as time elapses. The number decreases as the distance from the interface increases, and the metal is not mixed when the distance from the interface exceeds a predetermined distance. As a result, since the same metal as the main component of the object is mixed in the interface between the insulating film and the object surface, the thermal expansion coefficient in the vicinity of the interface between the insulating film and the object is very close. Thus, the adhesion between the two can be improved, and further, since no metal is mixed in the vicinity of the surface of the insulating coating, it is possible to suppress a decrease in the insulating characteristics (insulation breakdown voltage) of the insulating coating. Furthermore, since the amount of metal mixed in the insulating coating can be adjusted by the size of the metal block, the range of coverage for the area of the insulating coating formed on the surface of the object can be expanded.

  Hereinafter, an embodiment in which the technical idea of the present invention is applied to an insulating film forming method of forming an aluminum oxide (alumina) film (insulating film) as an insulating material on the surface of an object by an aerosol deposition method will be described. However, the present invention is characterized by a nozzle for injecting aerosol, and the basic configuration of the aerosol deposition method is well known in the art, and therefore detailed description and illustration are omitted.

(Embodiment 1)
As shown in FIG. 1, the nozzle 1 used in the insulating film forming method of the present embodiment is configured by bonding two plate-like members 2 and 3 formed of a metal material (for example, SUS316L stainless steel). ing.

  Each of the plate-like members 2 and 3 has a flat hexagonal shape and is overlapped and joined in the thickness direction. As shown in FIGS. 2A to 2D, the plate-like member 2 on one side has a first groove portion 2a and a second groove portion 2b that are recessed in the joint surface. The first groove 2a has a uniform width and depth, and one end is open to the wide side end face of the plate-like member 2 (see FIG. 2C). The second groove 2b is smaller and more uniform in width and depth than the first groove 2a, and one end is open to a narrow side end surface of the plate-like member 2 (see FIG. 2 (b)). Here, between the first groove 2a and the second groove 2b on the joint surface of the plate-like member 2, a buffer groove 2c that connects both the grooves 2a and 2b is formed in a recessed manner. The buffer groove 2c has the same width and depth on one end as those of the first groove 2a and communicates with the first groove 2a, and has a width and depth on the other end of the second groove 2b. It is the same as that of the second groove portion 2b and is formed in a shape in which the width dimension and the depth dimension change linearly from one end to the other end.

  On the other hand, the plate-like member 3 on the other side has the same width and length as the first groove 2a of the plate-like member 2 and one end as shown in FIGS. A third groove portion 3a having an opening at a wide side end surface of the plate-like member 3 (see FIG. 2G), a width dimension and a length dimension are the same as those of the buffer groove portion 2c of the plate-like member 2; A buffer groove 3b communicating with the third groove 3a is recessed in the joint surface.

  Thus, when the two plate-like members 2 and 3 are joined to each other at the joining surfaces to constitute the nozzle 1, the first groove portion 2a and the third groove portion 3a are formed as shown in FIG. A second flow path formed by a joint surface between the second groove 2b of the plate-like member 2 and the plate-like member 3, and a buffer flow path constituted by a joint surface between the buffer groove 2c and the plate-like member 3. Is formed in the nozzle 1, and an inlet into which the aerosol flows is opened to the wide side end surface of the nozzle 1 (see FIG. 1 (c)). The nozzle from which the aerosol is ejected opens at the narrow side end face of the nozzle 1 (see FIG. 1B).

  Here, the titanium carbide coating 4 and the alumina (aluminum oxide) coating are formed on the inner surface and inner bottom surface of the second groove 2b of the plate-like member 2 serving as the second flow path and the joining surface of the plate-like member 3. 5, a metal film 6 made of the same metal as the main component of the object is formed (see FIG. 1E).

  Next, a nozzle 1 having a total length of 20 mm and a nozzle size of 0.5 mm × 10 mm is prepared, and an alumina insulating coating is formed on the surface of the object (tough pitch copper substrate) by an aerosol deposition method using the nozzle 1 How to do will be described. A titanium carbide film 4 having a thickness of 5 μm is formed on the surface of the second flow path of the nozzle 1 by a plasma CVD method, and an alumina film 5 having a thickness of 10 μm is formed on the film 4. A metal film 6 having a film thickness of 1 μm formed by vacuum-depositing copper is formed on 5.

  First, alumina particles having a purity of 99.9% (particle size of 1 μm or less) are accommodated in a container (hereinafter referred to as an aerosolization chamber), and after the pressure inside the aerosolization chamber is reduced to 200 Pa, nitrogen gas is supplied at a rate of 7 minutes per minute. Introduced at a flow rate of liters and stirred to aerosolize. One end of a small diameter transport pipe is connected to the aerosolization chamber, and the inlet of the nozzle 1 is connected to the other end of the transport pipe introduced into the film forming chamber. An object is placed on a stage (hereinafter referred to as an XYZ stage) provided in a film forming chamber, and a jet port of a nozzle 1 disposed above the XYZ stage is provided. It faces the object. The XYZ stage is movable in a horizontal plane and a vertical plane, and reciprocates the target in the horizontal plane so that the film thickness of the insulating coating formed on the target surface is uniform.

  The film forming chamber is depressurized by a vacuum pump (for example, a rotary pump and a booster pump) so as to have a pressure lower than that in the aerosol forming chamber, and the aerosol flows through the carrier pipe by the gas flow generated by the pressure difference in both chambers. It is transferred to the deposition chamber. Further, the fine particles of the insulating material (alumina) transported by the gas are accelerated by passing through the flow path (second flow path) of the nozzle 1 having a very small diameter, and are ejected from the nozzle 1 to the target object. An insulating material film (insulating film) is formed on the surface of the object. At this time, the metal coating 6 covering the surface of the second flow path of the nozzle 1 is scraped off by the accelerated fine particles, and a part of the scraped metal particles is ejected from the jet outlet together with the fine particles of the insulating material. An insulating coating mixed with metal (copper) is formed on the surface of the object.

  Thus, the second flow path surface (metal coating 6) of the nozzle 1 through which the aerosol passes by the fine particles of the insulating material (alumina) that passes at high speed is scraped off, and the scraped metal particles are jetted onto the object. The film is formed on the surface of the object together with the fine particles of the insulating material. However, the metal particles scraped off with the passage of time decrease, and the ratio of the metal particles formed on the surface of the object also decreases. The amount in the vicinity of the interface is the largest, and the amount decreases as the distance from the interface increases. When the distance from the interface exceeds a predetermined distance, the metal is not mixed. For example, in this embodiment, the thickness of the metal coating 6 is 1 μm, and the thickness of the insulating coating formed on the surface of the object is 10 μm. When the distance from the object surface (interface) is 2 μm or more, the metal is mixed into the insulating coating. It wasn't. Therefore, since the same metal (copper) as the main component of the object (copper) is mixed in the interface between the insulating film and the object surface, thermal expansion in the vicinity of the interface between the insulating film and the object is performed. The coefficient becomes very close and the adhesion between them can be improved.

  Here, if the metal that is a conductor is mixed in the entire insulating film, there is a risk that the insulating characteristics (insulation withstand voltage) of the insulating film will deteriorate. However, as described above, the metal is mixed in the insulating film. The film thickness of the metal coating 6 is set so that the nozzle 1 ejects an amount of metal only in the vicinity of the interface with the object surface in the coating, in other words, only in the vicinity of the interface with the object surface. Therefore, no metal is mixed in the vicinity of the surface of the insulating coating, and as a result, a decrease in the insulating characteristics (insulation breakdown voltage) of the insulating coating can be suppressed.

(Embodiment 2)
Since the basic configuration of the nozzle 1 used in the insulating film forming method of the present embodiment is the same as that of the nozzle 1 of the first embodiment, common components are denoted by the same reference numerals, and illustration and description thereof are omitted. .

  Hereinafter, a nozzle 1 having a total length of 20 mm and a jet nozzle size of 0.5 mm × 10 mm is formed, and an alumina insulating film is formed on the surface of the object (brass substrate) by an aerosol deposition method using the nozzle 1. A method will be described. Note that a titanium carbide coating 4 having a thickness of 5 μm is formed on the surface of the second flow path of the nozzle 1 by plasma CVD as in the first embodiment, and an alumina coating 5 having a thickness of 10 μm is formed on the coating 4. Further, a metal film 6 having a film thickness of 0.5 μm formed by vacuum-depositing copper is formed on the film 5.

  First, alumina particles having a purity of 99.9% (particle size of 1 μm or less) are accommodated in an aerosolization chamber, the pressure in the aerosolization chamber is reduced to 200 Pa, helium gas is introduced at a flow rate of 10 liters per minute, and stirring is performed. And aerosolize. An object is placed on an XYZ stage provided in the film formation chamber, and a nozzle 1 disposed above the XYZ stage is opposed to the object.

  The fine particles of the insulating material (alumina) transported from the aerosol forming chamber to the film forming chamber are accelerated by passing through the flow path (second flow path) of the nozzle 1 having a small diameter, and are targeted from the nozzle 1 outlet. A film of insulating material (insulating film) is formed on the surface of the object by being sprayed onto the object. At this time, the metal coating 6 covering the surface of the second flow path of the nozzle 1 is scraped off by the accelerated fine particles, and a part of the scraped metal particles is ejected from the jet outlet together with the fine particles of the insulating material. An insulating coating mixed with metal (copper) is formed on the surface of the object.

  Here, when the film thickness of the metal film 6 is 0.5 μm and the film thickness of the insulating film formed on the surface of the object is 15 μm, the ratio of metal contamination is the highest near the interface, and the object surface ( The metal was not mixed in the insulating coating when it was 2 μm or more away from the interface.

(Embodiment 3)
Since the basic configuration of the nozzle 1 used in the insulating film forming method of the present embodiment is the same as that of the nozzle 1 of the first embodiment, common components are denoted by the same reference numerals, and illustration and description thereof are omitted. .

  Hereinafter, a nozzle 1 having a total length of 20 mm and a jet nozzle size of 0.5 mm × 10 mm is prepared, and an alumina insulating coating is formed on the surface of the object (aluminum substrate) by an aerosol deposition method using the nozzle 1. A method will be described. Note that a titanium carbide coating 4 having a thickness of 5 μm is formed on the surface of the second flow path of the nozzle 1 by plasma CVD as in the first embodiment, and an alumina coating 5 having a thickness of 10 μm is formed on the coating 4. Further, a metal film 6 having a thickness of 0.5 μm formed by vacuum vapor deposition of aluminum is formed on the film 5.

  First, alumina particles having a purity of 99.9% (particle size of 1 μm or less) are accommodated in an aerosolization chamber, and after the pressure in the aerosolization chamber is reduced to 200 Pa, nitrogen gas is introduced at a flow rate of 7 liters per minute and stirred. And aerosolize. An object is placed on an XYZ stage provided in the film formation chamber, and a nozzle 1 disposed above the XYZ stage is opposed to the object.

  The fine particles of the insulating material (alumina) transported from the aerosol forming chamber to the film forming chamber are accelerated by passing through the flow path (second flow path) of the nozzle 1 having a small diameter, and are targeted from the nozzle 1 outlet. A film of insulating material (insulating film) is formed on the surface of the object by being sprayed onto the object. At this time, the metal coating 6 covering the surface of the second flow path of the nozzle 1 is scraped off by the accelerated fine particles, and a part of the scraped metal particles is ejected from the jet outlet together with the fine particles of the insulating material. An insulating coating mixed with metal (aluminum) is formed on the surface of the object.

  Here, when the thickness of the metal coating 6 is 0.5 μm and the thickness of the insulating coating formed on the surface of the object is 12 μm, the ratio of metal contamination is the highest near the interface, and the surface of the object ( The metal was not mixed in the insulating coating when it was 1 μm or more away from the interface.

(Embodiment 4)
As shown in FIG. 3, the nozzle 10 used in the insulating film forming method of the present embodiment is a nozzle body 11 formed by bonding two plate-like members 12 and 13 formed of a metal material (for example, stainless steel). And a metal block 14 that is formed of the same metal as the main component of the metal material constituting the object and covers the surface of the nozzle body 11 including the ejection port.

  Each of the plate-like members 12 and 13 has a flat hexagonal shape and is overlapped and joined in the thickness direction. The plate-like member 12 on one side has a first groove portion 12a and a second groove portion 12b that are recessed in the joint surface. The first groove portion 12a has a uniform width dimension and depth dimension, and one end portion opens to a wide side end face of the plate-like member 12 (see FIG. 3C). The second groove portion 12b is smaller and more uniform in width and depth than the first groove portion 12a, and one end portion is open to a narrow side end surface of the plate-like member 12 (see FIG. 3 (b)). Here, between the first groove 12a and the second groove 12b on the joint surface of the plate-like member 12, a buffer groove 12c that connects both the grooves 12a and 12b is provided in a recessed manner. The buffer groove 12c has the same width and depth on one end as the first groove 12a and communicates with the first groove 12a, and the width and depth on the other end have a second groove 12b. It is the same as that of the second groove portion 12b and is formed in a shape in which the width dimension and the depth dimension change linearly from one end to the other end.

  On the other hand, the plate-like member 13 on the other side has the same width and length as the first groove 12a of the plate-like member 12, and one end is open on the wide side end face of the plate-like member 13. A third groove 13a (see FIG. 3C), and a buffer groove 13b having the same width and length as the buffer groove 12c of the plate-like member 12 and communicating with the third groove 13a. The joint surface is recessed.

  Thus, if the nozzle body 11 is formed by joining the two plate-like members 12 and 13 at the joint surfaces, the first groove portion 12a and the third groove portion 13a as shown in FIG. 1, a second flow path composed of a joint surface between the second groove portion 12 b of the plate-like member 12 and the plate-like member 13, and a buffer flow passage composed of a joint surface between the buffer groove portion 12 c and the plate-like member 13. Are formed in the nozzle body 11, and an inlet to which the aerosol flows is an entrance to the first flow path, and opens to a wide side end surface of the nozzle body 11 (see FIG. 3C). Further, an outlet from the second flow path, which ejects aerosol, opens to a narrow side end surface of the nozzle body 11 (see FIG. 3B).

  Here, a titanium carbide coating (not shown) and alumina (not shown) are respectively formed on the inner surface and inner bottom surface of the second groove portion 12b of the plate-like member 12 serving as the second flow path and the joint surface of the plate-like member 13. A film (not shown) of aluminum oxide is laminated.

  The metal block 14 includes two plate-like metal members 15 and 16 formed in a flat hexagonal shape, and the two plate-like metal members 15 and 16 are arranged in the thickness direction with the nozzle body 11 sandwiched therebetween. And is joined to the nozzle body 11 in an overlapping manner. The plate-like metal members 15 and 16 are formed on the nozzle body 11 except for the protrusions 15a and 16a that protrude forward from the tip of the nozzle body 11 with the nozzle opening and the bottom and narrow sides with the inlet opening. The body portions 15b and 16b covering the surface are integrally formed, and the body portions 15b and 16b are joined to the surfaces of the plate-like members 12 and 13, respectively. Here, a gap (flow path) formed between the protruding portions 15 a and 16 a of the plate-like metal members 15 and 16 communicates with the jet outlet at the tip of the nozzle body 11.

  Next, a nozzle main body 11 having a total length of 20 mm and a jet nozzle size of 0.5 mm × 10 mm is prepared, and projecting portions 15a and 16a from the tip of the nozzle main body 11 where the jet port opens forward (upward in FIG. 3A). The nozzle 10 is combined with the nozzle body 11 with a metal block 14 that protrudes by 10 mm and the opposing surfaces of the protrusions 15a and 16a protrude inward (in the direction of narrowing the gap (flow path)) from the surface of the alumina coating. A method of forming an insulating coating of alumina on the surface of an object (aluminum-magnesium alloy substrate) by an aerosol deposition method using this nozzle 10 will be described. A titanium carbide film having a thickness of 5 μm is formed on the surface of the second flow path of the nozzle body 11 by a plasma CVD method, and an alumina film having a thickness of 10 μm is formed on the film. The opposing surfaces of the protrusions 15a and 16a protrude inwardly by 5 μm from the surface of the alumina coating.

  First, alumina particles having a purity of 99.9% (particle size of 1 μm or less) are accommodated in an aerosolization chamber, and after the pressure in the aerosolization chamber is reduced to 200 Pa, nitrogen gas is introduced at a flow rate of 7 liters per minute and stirred. And aerosolize. An object is placed on an XYZ stage provided in the film forming chamber, and a nozzle 10 disposed above the XYZ stage is opposed to the object. The XYZ stage reciprocates in the range of 100 mm at a speed of 1 mm or more per second.

  The pressure in the film formation chamber is reduced by the vacuum pump so as to be lower than that in the aerosol formation chamber, and the aerosol is transferred to the film formation chamber through the transfer pipe by the gas flow caused by the pressure difference between the two chambers. And the clearance gap (flow path) in which the fine particle of the insulating material (alumina) accelerated through the 2nd flow path of the nozzle main body 11 is formed between the protrusion parts 15a and 16a of the metal block 14 from the jet nozzle of the nozzle main body 11. And is sprayed onto the object to form an insulating film on the surface of the object. At this time, the protrusions 15a and 16a of the metal block 14 are scraped off by the accelerated fine particles, and a part of the scraped metal particles is ejected from the ejection port together with the fine particles of the insulating material. An insulating film mixed with the metal (aluminum) constituting the block 14 is formed.

  Thus, the metal block 14 of the nozzle 10 through which the aerosol passes by the fine particles of the insulating material (alumina) that passes at high speed is scraped off, and the scraped metal particles are jetted onto the target object together with the fine particles of the insulating material. Although the film is deposited on the surface, the percentage of metal particles deposited on the surface of the target object is reduced as the amount of metal particles scraped off over time, and the amount of metal contamination in the insulating coating is the largest near the interface, When the distance from the interface decreases and the distance from the interface exceeds a predetermined distance, the metal is not mixed. For example, in this embodiment, the film thickness of the insulating film formed on the surface of the object is 20 μm, and no metal is mixed in the insulating film when it is separated from the object surface (interface) by 5 μm or more. Therefore, since the same metal (aluminum) as the main component of the object (aluminum) is mixed in the interface between the insulating film and the object surface, thermal expansion in the vicinity of the interface between the insulating film and the object is performed. Since the coefficients are very close to each other and the adhesion between them can be improved, and since no metal is mixed in the vicinity of the surface of the insulating coating, it is possible to suppress a decrease in the insulating properties (insulation breakdown voltage) of the insulating coating. Furthermore, the amount of metal mixed in the insulating coating is the size of the protrusions 15a, 16a of the metal block 14, specifically, the protrusion amount (flow path) by which the protrusions 15a, 16a protrude forward from the tip of the nozzle body 11. Of the insulating coating formed on the surface of the object, since the opposing surfaces of the protruding portions 15a and 16a can be adjusted by the protruding amount (flow channel width) protruding in the opposite direction from the surface of the alumina coating. The range that can be handled is expanded.

The nozzle in Embodiment 1 of this invention is shown, (a) is a top view, (b) is a top view, (c) is a bottom view, (d) is a right cross-sectional view, (e) is a 2nd flow path. FIG. The plate-shaped member which comprises a nozzle same as the above is shown, (a)-(d) is a top view, a top view, a bottom view, and a right sectional view of a plate-like member on one side, and (e)-(h) are already It is a top view, a top view, a bottom view, and a right sectional view of a plate-like member on one side. The nozzle in Embodiment 4 of this invention is shown, (a) is a top view, (b) is a top view, (c) is a bottom view, (d) is a right sectional view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nozzle 2 Plate-shaped member 2a 1st groove part 2b 2nd groove part 3 Plate-shaped member 3a 3rd groove part 6 Metal film

Claims (2)

In an insulating film forming method in which an aerosol in which fine particles of an insulating material are dispersed in a gas is sprayed from a nozzle onto an object, and an insulating film made of the insulating material is formed on the surface of the object.
The main component of the target object is provided on the surface of the flow path that comes into contact with the aerosol, having an inlet into which the aerosol flows in, a jet outlet through which the aerosol is jetted, and a flow path that guides the aerosol flowing in from the inlet to the jet outlet. Insulating film formation characterized by spraying aerosol onto an object using a nozzle coated with the same metal as the above metal with a predetermined thickness corresponding to the area of the insulating coating formed on the surface of the object Method. In an insulating film forming method in which an aerosol in which fine particles of an insulating material are dispersed in a gas is sprayed from a nozzle onto an object, and an insulating film made of the insulating material is formed on the surface of the object.
The nozzle body is provided with an inlet into which the aerosol flows, an outlet from which the aerosol is ejected, and a flow path that guides the aerosol flowing from the inlet to the outlet, and at the tip of the nozzle body at which the ejection opening opens, A metal block provided with a communication channel is disposed, and the metal block is a predetermined metal corresponding to the area of the insulating coating formed on the surface of the object by the same metal as the main component of the object. An insulating film forming method, wherein an aerosol is sprayed onto an object using a nozzle having a dimension.

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