Method for joining resin and metal

A joining method for joining a resin member and a metal member by heating is provided. Joining of the resin member and metal member is performed by heating a joining interface of the resin member and metal member to a temperature in a range of equal to or higher than a decomposition temperature of the resin member and lower than a temperature at which gas bubbles are generated in the resin member and by cooling a surface of the resin member on the opposite side from a joining surface thereof with the metal member to a temperature that is lower than the melting point of the resin member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a joining method and a joining apparatus for joining a resin and a metal by heating.

2. Description of the Related Art

Resin members and metal members are usually joined together by using an adhesive, but in order to simplify the joining process and comply with the Volatile Organic Compounds (VOC) regulations, physical concavities and convexities are formed on the joining surface of the metal member with the resin member or chemical functional groups are modified by performing surface treatment such as acid or alkali treatment or a primer treatment, or a joint body of a resin and a metal is obtained by conducting insert molding of a thermoplastic resin on the joining surface of the metal member with the resin member.

In a case where a metal member and a resin member are joined together by a process in which, as mentioned above, the joining surface of the metal member with the resin member is subjected to a surface treatment, although no adhesive is used, a large amount of surface treatment agent such as an acid, an alkali, or a primer treatment agent is used and, therefore, when the spent surface treatment agent is discarded, environmental load is created. In addition, the surface-treated metal member has to be cleaned and dried, and a long time is required for the cleaning and drying operations. As a result, the aforementioned process is unsuitable for parts that require high productivity, such as automotive parts or the like. A problem associated with a process in which a metal member and a resin member are joined by insert molding a thermoplastic resin on the metal member, is that limitations are placed on the shape of the joint body.

Accordingly, for example, Japanese Patent Application Publication No. 5-185521 (JP-A-5-185521) describes a method for joining a resin member and a metal member within a short period by a simple process without using an adhesive or a surface treatment agent and without creating environmental load, wherein the resin member is joined to the metal member by heating and melting.

In a case where the resin member is heated, as mentioned hereinabove, to a melting temperature or softening temperature, the softened resin member deforms according to concavities and convexities of the metal member surface and the two members are joined by the anchor effect demonstrated due to such deformation, but a sufficient joining strength cannot be obtained in joining by the anchor effect alone. Furthermore, the resin member is heated by a hot atmosphere inside an oven or with a heater, but if the heating temperature is too high, gas bubbles are generated inside the resin and these bubbles cause crack generation in the resin member after joining. In addition, where the entire resin member is heated, the resin member is entirely melted and design properties of the outer surface of the resin member are lost. The resultant problem is that the application range of the joint of the resin member and metal member is limited.

SUMMARY OF THE INVENTION

The invention provides a joining method and a joining apparatus for a resin and a metal by which a resin member and a metal member are joined within a short period by a simple process, without creating environmental load, a sufficient joining strength can be obtained, and design properties of the outer surface of the resin member are not degraded.

The first aspect of the invention relates to a joining method for joining a resin and a metal by heating. By this joining method, the joining of the resin and the metal is performed by heating a joining interface of the resin and the metal to a temperature in a range of equal to or higher than a decomposition temperature of the resin and lower than a temperature at which gas bubbles are generated in the resin. With such a joining method, no surface treatment agent is used, a necessary and sufficient joining strength may be obtained within a short time, and environmental load in the process of joining the resin and metal may be reduced. Further, the occurrence of cracks that originate from gas bubbles at the joining interface of the resin and metal may be prevented after the joining of the resin and metal, and the joining strength of the resin and metal may be ensured.

In the joining method according to the abovementioned aspect, the joining interface of the resin and metal is heated from a surface of the metal on the opposite side from a joining surface thereof with the resin, and a surface of the resin on the opposite side from a joining surface thereof with the metal is cooled to a temperature that is lower than a melting point of the resin. With such a joining method, no surface treatment agent is used, a necessary and sufficient joining strength may be obtained within a short time, and environmental load in the process of joining the resin and metal may be reduced. Further, because the joining of the resin and metal is performed, while preventing the resin from thermal deformation during joining of the resin and metal, the design property of the external surface of the joint body of the resin and metal on the side of the resin is not reduced and the product value of the joint body may be increased.

In the joining method according to the abovementioned aspect, the joining of the resin and metal is performed by interposing a thin film having an electric resistance higher than that of the metal in the interface of the resin and metal and high-frequency heating the thin film from a surface of the resin on the opposite side from a joining surface thereof with the metal. As a result, even when the metal is constituted by a material with a high thermal conductivity and a low electric resistance, the efficiency of heat input to the joining region of the metal and resin may be increased, the joining interface of the metal and resin may be adequately heated for joining by a simple process and within a short time, and a sufficient joining strength may be obtained.

Further, in the joining method according to the abovementioned aspect, a thin film having a laser reflectance lower than that of the metal is interposed in the interface of the resin and metal, the resin is constituted by a material that can transmit laser radiation, and the joining of the resin and metal is performed by emitting laser radiation toward the thin film from a surface of the resin on the opposite side from a joining surface thereof with the metal and heating the thin film. As a result, even when the metal has a high reflectance of laser radiation, the efficiency of heat input to the joining region of the metal and resin may be increased, the joining interface of the metal and resin may be adequately heated for joining by a simple process and within a short time, and a sufficient joining strength may be obtained.

Further, in the joining method according to the abovementioned aspect, a concavity into which the heated resin can penetrate is formed in a zone of the metal around a joining region of the resin and metal. As a result, the softened resin penetrates inside the concavity and an anchor effect is produced when the metal and resin are joined, thereby making it possible to increase the joining strength of the metal and resin after joining.

The second aspect of the invention relates to a joining apparatus that is used when a resin and a metal are joined by heating. The joining apparatus includes a heating tool that heats a joining interface of the resin and the metal from a surface of the metal on the opposite side from a joining surface thereof with the resin, and a cooling tool that cools a surface of the resin on the opposite side from a joining surface thereof with the metal to a temperature that is lower than a melting point of the resin. With such a configuration, a necessary and sufficient joining strength may be obtained within a short time and environmental load in the process of joining the resin and metal may be reduced without using a surface treatment agent. Further, because the joining of the resin and metal may be performed, while preventing the resin from thermal deformation during joining of the resin and metal, the product value of the joint body may be increased, without reducing the design property of the external surface of the joint body of the resin and metal on the side of the resin.

Further, in the joining apparatus according to the abovementioned aspect, the heating tool heats the joining interface of the resin and metal to a temperature in a range of equal to or higher than a decomposition temperature of the resin and lower than a temperature at which gas bubbles are generated in the resin. With such configuration, no surface treatment agent is used, a necessary and sufficient joining strength may be obtained within a short time, and environmental load in the process of joining the resin and metal may be reduced. Further, the occurrence of cracks that originate from gas bubbles at the joining interface of the resin and metal may be prevented, and the joining strength of the resin and metal may be ensured.

In accordance with the invention, no surface treatment agent is used, a necessary and sufficient joining strength may be obtained within a short time, and environmental load in the process of joining the resin and metal may be reduced.

DETAILED DESCRIPTION OF EMBODIMENTS

An embodiment of the invention will be described below with reference to the appended drawings.

As shown inFIG. 1, in a joining method of the present embodiment in which a resin member4and a metal member3are joined together, in a state in which the resin member4and metal member3are stacked, the two are joined by heating a joining interface of the resin member4and metal member3to a predetermined temperature with a heating body1, which is a heating tool.

More specifically, for example, the joining interface of the resin member4and metal member3is heated by bringing the heating body1into contact with the surface of the metal member3on the opposite side from the joining surface thereof with the resin member4. Further, the heating with the heating body1is conducted so that the joining surface5of the resin member4with the metal member3assumes a temperature in a range of equal to or higher than the decomposition temperature of the resin member4and lower than a temperature at which gas bubbles are generated in the resin member4.

In this case, as shown inFIG. 2, the decomposition temperature tb of the resin member4is higher than the melting point ta of the resin member4, and the temperature tc at which gas bubbles are generated in the resin member4is higher than the decomposition temperature tb of the resin member4. Further, the temperature td of the heating body1is higher than the temperature tc at which gas bubbles are generated in the resin member4(in other words, (temperature td of the heating body1)>(temperature tc at which gas bubbles are generated in the resin member4)>(decomposition temperature tb of the resin member4)>(melting point ta of the resin member4)). When the resin member4and metal member3are joined, the joining of the two is performed by holding the joining interface of the resin member4and metal member3, strictly speaking, the joining surface5of the resin member4, at a temperature within a range of equal to or higher than the decomposition temperature of the resin member4and lower than the temperature at which gas bubbles are generated in the resin member4(this range is included in the hatched portion inFIG. 2), during a predetermined time period ΔT.

At the same time as the heating is performed with the heating body1in the above-described manner, a cooling body2, which is a cooling tool, is brought into contact with the surface of the resin member4on the opposite side from the joining surface5, and the surface of the resin member4on the opposite side from the joining surface5is cooled to a temperature less than the melting point of the resin member4.

In other words, in a state in which the resin member4and metal member3are stacked, the joining of the resin member4and metal member3is performed by heating the joining surface5of the resin member4that is in contact with the joining interface with the metal member3to a temperature in a range of equal to or higher than the decomposition temperature of the resin member4and lower than the temperature at which gas bubbles are generated in the resin member4and cooling the surface of the resin member4on the opposite side from the joining surface5to a temperature that is lower than the melting point of the resin member4.

In a case where the joining of the resin member4and metal member3is performed by heating the resin member4to the melting point ta, the two are joined only because the joining surface5of the resin member4that has reached the melting temperature and softened is deformed along the peaks and valleys of the joining surface of the metal member3and the anchor effect is demonstrated. By contrast, where the joining surface5of the resin member4is heated, as described hereinabove, to a temperature equal to or higher than the decomposition temperature of the resin member4, the resin member4at the joining surface5is decomposed and fusion active groups are created at the joining surface5. The fusion active groups that are created at the joining surface5of the resin member4are bonded by intermolecular forces to the joining surface of the metal member3with the resin member4, and joining by the intermolecular forces of the fusion active groups is conducted in addition to the joining by the anchor effect on the joining interface of the resin member4and metal member3, whereby a high joining strength can be obtained.

The joining is thus conducted with a joining apparatus including a heating body1that heats the joining interface of the resin member4and metal member3from a surface of the metal member3on the opposite side from the joining surface thereof with the resin member4, and a cooling body2that cools the surface of the resin member4on the opposite side from the joining surface5thereof with the metal member3to a temperature that is lower than a melting point of the resin member4.

In other words, because the resin member4and metal member3are joined by heating the joining surface5of the resin member4to a temperature in a range of equal to or higher than a decomposition temperature of the resin member4and lower than a temperature at which gas bubbles are generated in the resin member4, neither an adhesive nor a surface treatment agent such as an acid, an alkali, and a primer treatment agent is used, a necessary and sufficient joining strength can be obtained within a short time, and environmental load in the process of joining the resin member4and metal member3can be reduced. Further, because the heating temperature of the joining surface5of the resin member4is less than a temperature at which gas bubbles are generated in the resin member4, no gas bubbles are generated at the joining surface5of the resin member4by heating, the occurrence of cracks that originate from gas bubbles at the joining interface of the resin member4and metal member3can be prevented, and the joining strength of the resin member4and metal member3can be ensured after the resin member4and metal member3have been joined.

In addition, when the resin member4and metal member3are joined, the surface of the resin member4on the opposite side from the joining surface5is cooled to a temperature that is lower than the melting point of the resin member4. Therefore, this surface is not deformed by heating. Because the resin member4can be prevented from thermal deformation during joining of the resin member4and metal member3, the design property of the external surface of the joint body of the resin member4and metal member3on the side of the resin member4is not reduced and the product value of the joint body can be increased.

For example, various ferrous metals, stainless steel, aluminum materials (including aluminum alloys), magnesium materials (including magnesium alloys), and copper materials (including copper alloys) can be used as the material constituting the metal member3, but this list is not limiting and other metal materials may be also used.

For example, nylon resins, polyester resins, acrylonitrile butadiene styrene (ABS) resins, and other thermoplastic resins of general use, engineering plastics of general use, super-engineering plastics, and thermoplastic elastomers can be used as the material constituting the resin member4. A filler such as carbon fibers, glass fibers, talc, mica, kaolin, and calcium carbonate that increases the mechanical strength and the like may be admixed to the resin member4.

In a case where the resin member4is constituted by a nonpolar resin that has absolutely no functional groups, the joining of the resin member4and metal member3may be conducted after subjecting the joining surface5of the resin member4to a typical dry surface treatment such as plasma treatment or corona treatment, without using a surface treatment agent such as an acid, an alkali, or a primer treatment agent. By so joining the resin member4and metal member3after performing the dry surface treatment, it is possible to introduce fusion active groups to the joining surface5by the surface treatment method with a low environmental load and increase the joining strength.

Further, in a case where the resin member4is constituted by a nonpolar resin that has absolutely no functional groups, the joining of the resin member4and metal member3is preferably conducted after roughening the joining surface of the metal member3with the resin member4by using a polishing tool such as sandpaper or forming peaks and valleys on the joining surface of the metal member3with the resin member4by electron beam processing or laser processing. Where the joining surface of the metal member3with the resin member4is thus provided with roughness or peaks and valleys, the heated resin member4can penetrate into the joining surface of the metal member3and demonstrate the anchor effect.

Further, the heating body1can be constituted by a high-temperature substance (solid, liquid, or gaseous) that can heat the joining surface5of the resin member4to a temperature in a range of equal to or higher than a decomposition temperature of the resin member4and lower than a temperature at which gas bubbles are generated in the resin member4and can be configured so that the heating of the joining surface5be performed by bringing the high-temperature substance into contact with the surface of the metal member3on the opposite side from the joining surface thereof with the resin member4. Further, the heating body1can be constituted to heat the joining surface5, for example, by electric resistance heating, high frequency, infrared radiation, or laser radiation, or to heat the joining surface5by using friction heat created by vibrations or ultrasound. These examples are not limiting and other heating means may be also used.

The cooling body2can be constituted by a low-temperature substance (solid, liquid, or gaseous) that can cool the surface of the resin member4on the opposite side from the joining surface5thereof to a temperature that is less than the melting point of the resin member4, but such a configuration is not limiting and other cooling bodies may be also used.

An embodiment will be explained below in which, as shown inFIG. 3, the metal member3and resin member4are joined by using rod-shaped members as the heating body1and cooling body2, bringing the rod-shaped heating body1into contact with the surface of the metal member3on the opposite side from the joining surface thereof with the resin member4to conduct heating and similarly bringing the rod-shaped cooling body2into contact with the surface of the resin member4on the opposite side from the joining surface5to conduct cooling.

The heating body1and cooling body2of the present embodiment are formed to a shape similar to that of a gun of a spot welding machine. More specifically, the heating body1and cooling body2are substantially cylindrical columnar members in which the end portions thereof on the side that will come into contact with the metal member3and resin member4, respectively, are tapered, and these cylindrical columnar members are disposed on both sides of the metal member3and resin member4in a state in which the metal member3and resin member4are stacked. The heating body1is pressed against the metal member3, the cooling body2is pressed against the resin member4, and the metal member3and resin member4are pressed together in a state in which the metal member3and resin member4are stacked. As a result, the joining surface5of the resin member4is melted by heat from the heating body1and also decomposed, thereby joining the resin member4to the metal member3. In this case, the surface of the resin member4that has come into contact with the cooling body2is cooled by the cooling body2and, therefore, prevented from thermal deformation. Because the heating body1and cooling body2are formed to a shape similar to that of a gun of a spot welding machine, a line and system of the spot welding machine can be used in the process of joining the metal member3and resin member4.

Further, as shown inFIG. 4, the heating body1and cooling body2may be constituted by roller members. The heating body1and cooling body2constituted by roller member are disposed opposite each other at a distance equal to or slightly less than the thickness of the metal member3and resin member4in a stacked state thereof.

By feeding the metal member3and resin member4in a stacked state thereof between the heating body1and cooling body2disposed opposite each other and squeezing the metal member3and resin member4in a stacked state thereof by the heating body1and cooling body2, the joining surface5of the resin member4is melted by the heat of the heating body1and decomposed, whereby the metal member3and resin member4are joined together. In this case, the surface of the resin member4that comes into contact with the cooling body2is cooled by the cooling body2and, therefore, prevented from thermal deformation. When the joining of the metal member3and resin member4is performed, the metal member3and resin member4that have been fed between the roll-shaped heating body1and cooling body2are successively conveyed by rotation of the heating body1and cooling body2, thereby making it possible to join the metal member3and resin member4continuously, as in seam welding.

The metal member3may have the following configuration. Thus, as shown inFIGS. 5 to 7, slits (cavities)3acan be formed in the metal member3on the circumference of a joining region6of the metal member3and resin member4. The slits3apass through the metal member3in the joining direction thereof to the resin member4and are formed in a plurality of places on the circumference of the joining region6.

As shown inFIG. 6, portions where the slits3aare formed in the metal member3are cavities. Therefore, heat transfer between two sides of the metal member3that sandwich the slits3a(between a zone on the inner side of the slits3aand zone outside the slits) is prevented. Therefore, heat supplied from the heating body1through the metal member3to the joining interface of the metal member3and resin member4can be prevented from diffusing to the outside in the plane direction of the joining region6and the joining region6can be efficiently heated. Further, because heat is not transferred to the outside of the slits3a, the joining of the metal member3and resin member4is not conducted, thereby enabling the joining region6to be controlled with good accuracy.

At the joining surface5of the resin member4, because the resin member4melts within a region somewhat wider than the joining region6, the molten and softened resin member4penetrates into the slits3a, as shown inFIG. 8. Thus, an anchor effect is produced in the portion where the resin member4has penetrated into the slits3aof the metal member3and, therefore, the joining strength of the metal member3and resin member4after joining can be increased.

Thus, by forming the slits3aon the circumference of the joining region6in the metal member3, it is possible to inhibit heat transfer between the portions of the metal member3on both sides of the slits3a, and the heat that is supplied to the joining interface of the metal member3and resin member4from the heating body1via the metal member3is prevented from diffusing to the outside in the plane direction of the joining region6(seeFIG. 6).

As shown inFIG. 7, the slits3aare formed so as to cover the entire region on the circumference of the joining region6, but the ratio at which the circumference of the joining region6is covered may be changed appropriately. Thus, the region covered by the slits3acan be appropriately determined correspondingly to the degree to which the diffusion of heat transferred to the joining region6in the plane direction is inhibited. Further, the slits3athat are formed in the metal member3may be formed by cutting with a cutting tool or machining, e.g., punching, and also by processing with a laser or electron beam.

Instead of forming the above-described slits3ain the metal member3, it is also possible to form grooves3b, as shown inFIGS. 9 and 10, as a structure that prevents heat transfer to the outside of the joining region6. The grooves3bare formed from the surface of the metal member3on the opposite side from the joining surface thereof with the resin member4toward the joining interface side. In other words, the grooves3bare opened at the surface of the metal member3on the opposite side from the joining surface thereof with the resin member4and are closed and have a bottom portion on the joining interface side of the metal member3with the resin member4.

Similarly to the slits3a, the grooves3bare formed in a plurality of places on the circumference of the joining region6, and heat supplied from the heating body1to the joining interface of the metal member3and resin member4through the metal member3can be prevented from diffusing to the outside in the plane direction of the joining region6. In a case where the grooves3bare formed as a configuration that inhibits the diffusion of heat transferred to the joining region6to the outside in the plane direction, a bottom portion is formed in the grooves3bat the joining interface side of the metal member3and resin member4and the grooves3bdo not pass as the aforementioned slits3athrough the metal member3. Therefore, the rigidity of the metal member3can be increased by comparison with that in the case in which the slits3aare formed in the metal member3.

Grooves3cand grooves3dcan be also formed respectively on the joining interface side of the metal member3with the resin member4and on the surface side on the opposite side from the joining interface side, as shown inFIG. 11, as a structure that prevents heat transfer to the outside of the joining region6. The grooves3care opened at the joining surface of the metal member3with the resin member4and have a bottom in the intermediate portion in the thickness direction of the metal member3. The grooves3dare opened at the surface on the opposite side from the joining interface and have a bottom in the intermediate portion in the thickness direction of the metal member3. The grooves3cand grooves3dare disposed in substantially identical positions in the plane direction of the metal member3, and the grooves3cshare bottom portions with the grooves3d.

Further, similarly to the slits3a, the grooves3cand3dare formed in a plurality of places on the circumference of the joining region6, and heat supplied from the heating body1to the joining interface of the metal member3and resin member4through the metal member3can be prevented from diffusing to the outside in the plane direction of the joining region6. Thus, in a case where the grooves3cand3dare formed as a configuration that inhibits the diffusion of heat transferred to the joining region6to the outside in the plane direction, a bottom portion of each pair of grooves3cand3dis formed between the grooves3cand grooves3dof the metal member3, and the grooves3cand3ddo not pass as the aforementioned slits3athrough the metal member3. Therefore, the rigidity of the metal member3can be increased by comparison with that in the case in which the slits3aare formed in the metal member3. Further, the melted and softened resin member4penetrates into the grooves3c, thereby generating the anchor effect in the portions where the resin member4has penetrated into the grooves3cof the metal member3.

Grooves3esuch as shown inFIGS. 12 and 13can be also formed as a structure that prevents heat transfer to the outside of the joining region6. The grooves3eare formed from the joining surface of the metal member3with the resin member4toward the surface on the opposite side from the joining surface. In other words, the grooves3eare opened at the joining surface of the metal member3with the resin member4and are closed and have a bottom at the surface of the metal member3on the opposite side from the joining surface of the metal member3with the resin member4.

Similarly to the slits3a, the grooves3eare formed in a plurality of places on the circumference of the joining region6, and heat supplied to the joining interface of the metal member3and resin member4can be prevented from diffusing to the outside in the plane direction of the joining region6. In a case where the grooves3eare formed as a configuration that inhibits the diffusion of heat transferred to the joining region6to the outside in the plane direction, a bottom portion of the groove3eis formed at the surface of the metal member3on the opposite side from the joining surface thereof with the resin member4and the grooves3edo not pass, as the aforementioned slits3a, through the metal member3. Therefore, the rigidity of the metal member3can be increased by comparison with that in the case in which the slits3aare formed in the metal member3.

In the configuration in which the grooves3bshown inFIGS. 9 and 10are formed in the metal member3, the heating body1shown inFIG. 3etc. may be disposed at the surface side opposite from the joining surface side of the metal member3with the resin member4, and the joining interface of the metal member3and resin member4may be heated from the side of the metal member3. Further, in the configuration in which the grooves3eshown inFIGS. 12 and 13are formed in the metal member3, the joining interface of the metal member3and resin member4may be heated from the side of the resin member4by using the below-described high-frequency heating apparatus11or laser irradiation apparatus12. Further, in the configuration in which the slits3ashown inFIGS. 5 to 7and grooves3cand3dshown inFIG. 11are formed in the metal member3, the heating may be performed from the side of the metal member3or from the side of the resin member4.

Further, as shown inFIG. 14, when the joining interface of the metal member3with the resin member4is heated, the high-frequency heating apparatus11may be used as the heating tool. When the joining interface is heated by using the high-frequency heating apparatus11, a thin film8is inserted between the metal member3and resin member4, and the high-frequency heating apparatus11is disposed on the surface side of the resin member4on the opposite side from the joining surface5.

The heating method in which the thin film8is inserted between the metal member3and resin member4and the joining interface of the metal member3and resin member4is heated using the high-frequency heating apparatus11can be applied when the metal member3is a non-magnetic material having a low thermal conductivity and a low electric resistance, such as aluminum (Al) and copper (Cu).

In this case, a magnetic material with an electric resistance higher than that of the metal member3, for example, a metal material such as iron (Fe), nickel (Ni), and cobalt (Co) may be used as the thin film8. The thin film8may be provided by subjecting the joining surface of the metal member3with the resin member4to various processing methods, for example, electroplating, spraying, or cold spraying with the aforementioned metal materials. The metal member3and resin member4are joined together by stacking the metal member3provided with the thin film8with the resin member4and then high-frequency heating the thin film8interposed in the joining interface of the metal member3with the resin member4using the high-frequency heating apparatus11.

Generally, in a case where the metal member3is constituted by a material with a high thermal conductivity and a low electric resistance, such as aluminum (Al) and copper (Cu), when the metal member3is heated from the surface on the side opposite from the joining surface thereof with the resin member4and the joining interface is heated by the heat transferred to the metal member3, the heat transferred to the metal member3from the surface on the opposite side from the joining surface diffuses over a large range, the efficiency of heat input to the joining region6of the metal member3and resin member4is low, and the heat input range is difficult to control.

By contrast, when the thin film8is interposed in the joining interface of the metal member3and resin member4and the thin film8is directly heated by the high-frequency heating apparatus11disposed on the side of the resin member4, the joining surface5of the resin member4is heated to a temperature in a range of equal to or higher than a decomposition temperature of the resin member4and lower than a temperature at which gas bubbles are generated in the resin member4.

Where the thin film8disposed at the joining interface of the metal member3and resin member4is thus directly heated, the efficiency of heat input in the joining region6can be increased even when the metal member3is constituted by a material with a high thermal conductivity and a low electric resistance. Further, by constituting the heating body1by the high-frequency heating apparatus11and forming the heating coil of the high-frequency heating apparatus11to a size corresponding to the size of the joining region6, it is possible to control the range of heat input to the joining interface of the metal member3and resin member4. As a result, joining can be performed by adequately heating the joining interface of the metal member3and resin member4within a short period by a simple process and a sufficient joining strength can be obtained. In the above-described configuration, only the high-frequency heating apparatus11is used as the heating tool that heats the joining interface of the metal member3and resin member4, but the high-frequency heating apparatus11may be used together with the heating body1and/or cooling body2.

Further, as shown inFIG. 15, in a case where the joining interface of the metal member3and resin member4is heated, the laser irradiation apparatus12can be used as the heating body1and heating can be performed by irradiating the joining interface with the laser radiation from the laser irradiation apparatus12. In a case where heating is performed by irradiating the joining interface with the laser radiation from the laser irradiation apparatus12, a thin film9is interposed between the metal member3and resin member4and the laser irradiation apparatus12is disposed at the surface on the side opposite from the side of the joining surface5of the resin member4.

The heating method in which the thin film9is inserted between the metal member3and resin member4and the joining interface of the metal member3and resin member4is heated using laser radiation from the laser irradiation apparatus12can be applied when the metal member3is a material having a low thermal conductivity and a high reflectance of laser radiation in the infrared region, such as aluminum (Al) and copper (Cu).

In this case, the resin member4may be constituted by a material that can transmit the laser radiation, and a metal material with reflectance of laser radiation in the infrared region lower than that of the metal member3, for example, iron (Fe), nickel (Ni), cobalt (Co), and zinc (Zn) may be used as the thin film9. The thin film9may be provided by subjecting the joining surface of the metal member3with the resin member4to various processing methods, for example, electroplating, spraying, or cold spraying with the aforementioned metal materials.

The metal member3and resin member4are joined together by stacking the metal member3provided with the thin film9with the resin member4and then heating the joining interface by irradiating the thin film9interposed in the joining interface of the metal member3with the resin member4with laser radiation, from the laser irradiation apparatus12. The laser irradiation apparatus12may be constituted by an apparatus that emits infrared laser radiation, such as a yttrium aluminum garnet (YAG) laser, a semiconductor laser, or a CO2laser.

Generally, in a case where the metal member3is constituted by a material with a high reflectance of infrared laser radiation, such as aluminum (Al) and copper (Cu), even when the joining surface of the metal member3with the resin member4is irradiated with laser radiation, most of the radiation is reflected at the joining surface. As a result, the heating efficiency is poor and the metal member3and resin member4are difficult to join together by heating by irradiation with laser radiation.

By contrast, where the thin film9is interposed in the joining interface of the metal member3and resin member4and laser radiation is emitted toward the thin film9from the laser irradiation apparatus12disposed on the side of the resin member4, the joining surface5of the resin member4is heated to a temperature in a range of equal to or higher than a decomposition temperature of the resin member4and lower than a temperature at which gas bubbles are generated in the resin member4.

Where the thin film9disposed at the joining interface of the metal member3and resin member4is thus heated by laser radiation, the efficiency of heat input in the joining region6can be increased even when the metal member3is constituted by a material with a high reflectance of laser radiation and joining of the metal member3and resin member4can be easily realized by heating by irradiation with laser radiation. Further, by constituting the heating body1by the laser irradiation apparatus12and forming the irradiation range of laser radiation from the laser irradiation apparatus12to a size corresponding to the size of the joining region,6, it is possible to control the range of heat input to the joining interface of the metal member3and resin member4. As a result, joining can be performed by adequately heating the joining interface of the metal member3and resin member4within a short period by a simple process and a sufficient joining strength can be obtained. In the above-described present example, only the laser irradiation apparatus12is used as the heating tool that heats the joining interface of the metal member3and resin member4, but the laser irradiation apparatus12may be used together with the heating body1and/or cooling body2.