JP7624820B2 - Joining structure, joining method, and manufacturing method of case and resin member - Google Patents

Description

The present invention relates to a joining structure and joining method for joining a resin member and a metal member via a sealing material, as well as a manufacturing method for a case and a resin member.

For example, Patent Document 1 (Patent Publication No. 5278443) describes how, when joining and sealing a resin timing chain cover to a metal cylinder block and cylinder head of an engine, the joining surface of the timing chain cover is first subjected to plasma treatment, a metal sprayed film is formed on the joining surface of the timing chain cover, the surface of the metal sprayed film is then subjected to plasma treatment, a paste-like gasket is applied onto the metal sprayed film, and the timing chain cover is joined and sealed to the cylinder block and cylinder head.

Patent No. 5278443

In the structure of Patent Document 1, before forming the metal sprayed film on the joining surface of the timing chain cover, the joining surface of the timing chain cover is subjected to plasma treatment in order to increase the adhesive strength between the two, and furthermore, after the metal sprayed film is formed, the surface of the metal sprayed film must be subjected to plasma treatment. This not only increases the number of steps and reduces productivity, but also requires a device to perform plasma treatment, which has the disadvantage of increasing equipment costs. However, if the metal sprayed film is formed on the joining surface of the timing chain cover without performing plasma treatment, or if a paste-like gasket is applied to the surface of the metal sprayed film without performing plasma treatment, the adhesive strength will be weakened and problems such as peeling will be more likely to occur.

The problem that the present invention aims to solve is to provide a joining structure and joining method that can strengthen the joining force between a resin member and a metal member while reducing the number of steps and reducing equipment costs, as well as a method for manufacturing a case and a resin member.

In order to solve the above problems, the present invention provides a joining structure in which a joining surface of a resin member and a joining surface of a metal member are joined via a sealing material, the metal member is formed in a case shape from aluminum, the resin member is formed in a shape that covers an opening or a through hole of the metal member from polyphenylene sulfide resin, and a metal film with a film thickness of 0.05 μm or more and 1 μm or less is formed by sputtering on at least a portion of the joining surface of the resin member.

In this joining structure, a metal film having a thickness of 0.05 μm or more and 1 μm or less is formed by sputtering on at least a part of the joining surface of the resin member, so that the metal film formed on the joining surface of the resin member plays a role of strengthening the joining force between the resin member and the metal member through the sealing material. In this case, since the metal film formed on the joining surface of the resin member is formed by sputtering, unlike the metal sprayed film of Patent Document 1, even if the metal film is formed without performing plasma treatment on the joining surface of the resin member, the adhesive force between the joining surface of the resin member and the metal film can be ensured. Moreover, since a high-purity metal film can be formed by sputtering, unlike the metal sprayed film of Patent Document 1, even if the sealing material is applied to the surface of the metal film without performing plasma treatment on the surface of the metal film, the adhesive force of the sealing material to the metal film is not weakened, and the adhesive force can be ensured. Furthermore, since the thickness of the metal film is set to 0.05 μm or more and 1 μm or less, the effect of increasing the adhesive force as a metal film and the effect of preventing the metal film from peeling off from the joining surface of the resin member can be ensured. This is because, if the thickness of the metal film is less than 0.05 μm, the metal film becomes too thin and the effect of enhancing the adhesive strength of the metal film with the sealing material is insufficient; on the other hand, if the thickness of the metal film is more than 1 μm, the total stress of the metal film (= internal stress x film thickness) becomes too large, making it more likely that problems such as peeling of the metal film will occur due to the difference in thermal expansion coefficient between the resin member and the metal film.
Moreover, in the present invention, the metal member is made of aluminum and the resin member is made of polyphenylene sulfide resin, so that the resin member and the metal member to be joined are made of materials with similar linear expansion coefficients. Therefore, when the resin member is placed over the metal member formed into a case shape and joined, the degrees of expansion and contraction are similar even when a temperature change occurs, and the metal member and the resin member can be stably joined via the sealant.

In this case, if the thickness of the metal film is set to 0.05 μm or more and 0.2 μm or less, the total stress of the metal film can be appropriately reduced, effectively avoiding problems such as peeling of the metal film due to the difference in thermal expansion coefficient between the resin member and the metal film.

Furthermore, by using a liquid gasket (FIPG) as a sealing material, sufficient sealing performance can be ensured along with adhesive strength.

In this case, the metal film may be formed only on a part of the joint surface of the resin member, but for example, if the resin member is formed in a case shape to house the electronic unit, the joint surface may be formed continuously around the entire circumference of the opening edge, and the metal film may be formed continuously around the entire circumference of the joint surface. In this way, sufficient sealing can be ensured between the resin member housing the electronic unit and the metal member.

In addition, in the sputtering process for forming the metal film, it is advisable to set the deposition temperature of the metal film to 30°C or higher and 150°C or lower. By setting the deposition temperature of the metal film to 150°C or lower, it becomes easier to form a metal film with a thickness of 1 μm or less, and thermal stress can be reduced, making it possible to more effectively avoid problems such as peeling of the metal film. Furthermore, by setting the deposition temperature of the metal film to 30°C or higher, it is possible to prevent poor deposition.

FIG. 1 is a vertical cross-sectional view showing a state in which a metal case and a resin lid are joined together in one embodiment of the present invention. FIG. 2 is an external perspective view showing a state in which the resin lid body and the resin cap have been removed from the metal case (state before the sputtering step). FIG. 3 is an external perspective view showing a resin lid body on which a metal film is formed by sputtering. FIG. 4 is a perspective view showing the appearance of a resin cap on which a metal film is formed by sputtering.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electronic unit housing case 10 will be described below.
As shown in Figures 1 and 2, the electronic unit storage case 10 of this embodiment is composed of parts such as a metal case 11 which is a metal member formed into a case shape to store an electronic unit (not shown) such as a power control unit, which is an in-vehicle electrical component, a resin lid body 12 which is a resin member that covers the top opening of the metal case 11, and a resin cap 14 which is a resin member that covers a through hole 13 for wiring, drain, etc. formed on the side of the metal case 11.

Here, the metal case 11 is formed from a metal such as aluminum, SUS, iron, or copper. On the other hand, the resin lid 12 and the resin cap 14 are molded into a predetermined shape from a resin such as polyphenylene sulfide resin, polypropylene, or polyamide. The metal case 11 and the resin lid 12, or the metal case 11 and the resin cap 14, are preferably formed from materials with similar linear expansion coefficients so that they can be tightly attached even when a temperature difference occurs.

Next, a structure for joining the resin lid body 12 and the resin cap 14 to the metal case 11 will be described.
As shown in FIG. 2 , the joining surface 11a is formed in a flat rectangular frame shape continuously around the entire periphery of the edge of the top opening of the metal case 11, and the joining surface 13a is formed in a circular ring shape continuously around the entire periphery of the edge of the opening of the through hole 13 on the side of the metal case 11.

On the other hand, as shown in Fig. 3, the joining surface (lower surface) of the resin lid 12 has a joining surface 12a having the same shape as the joining surface 11a of the metal case 11. As shown in Fig. 4, the joining surface of the resin cap 14 has a joining surface 14a having the same shape as the joining surface 13a around the through hole 13 of the metal case 11.

Metal films 15, 16 with a thickness of 0.05 μm to 1 μm (more preferably 0.05 μm to 0.2 μm) are formed by sputtering on the joining surfaces 12a, 14a of the resin lid 12 and 14a, respectively, continuously around the entire circumference of the joining surfaces 12a, 14a. The width W (see Figures 3 and 4) of the metal films 15, 16 may be the same as the width of the joining surfaces 12a, 14a, or may be slightly narrower. The metal films 15, 16 are formed of a metal such as aluminum or SUS.

A silicone-based liquid gasket (Formed In Place Gasket: FIPG) is used as the sealant 17 that joins the resin lid 12 and the resin cap 14 to the metal case 11. This sealant 17 (liquid gasket) is applied to the surfaces of the metal films 15, 16 formed on the joining surfaces 12a, 14a of the resin lid 12 and the resin cap 14, and then hardens in an elastic state to exert adhesive strength. Therefore, after applying the sealant 17 to the surfaces of the metal films 15, 16 formed on the joint surfaces 12a, 14a of the resin lid 12 and the resin cap 14, the resin lid 12 and the resin cap 14 are placed on the joint surfaces 11a, 13a of the metal case 11 before the sealant 17 hardens, and the sealant 17 on the surfaces of the metal films 15, 16 is brought into sufficient contact with the joint surfaces 11a, 13a of the metal case 11, and the sealant 17 is allowed to harden, thereby joining the resin lid 12 and the resin cap 14 to the metal case 11 and sealing the opening and the through hole 13 of the metal case 11. The joint surfaces 12a, 14a of the resin lid 12 and the resin cap 14 may be flat, or may be non-flat with small steps or irregularities to increase the adhesive strength with the sealant 17.

In the sputtering process for forming the metal films 15 and 16, any of the following methods may be used: magnetron sputtering, bipolar sputtering, DC (direct current) sputtering, RF (radio frequency) sputtering, reactive sputtering, ion beam sputtering, etc.

Before sputtering, the resin lid 12 (resin cap 14) is masked except for the joining surface 12a (14a) so that the metal film 15 (16) is formed only on the joining surface 12a (14a). The material used for masking should be a tape or plate made of a material that is heat resistant and can withstand a vacuum, for example, Kapton (registered trademark) adhesive tape. Sputtering has the advantage that the metal film 15 (16) can be formed on a smaller area than thermal spraying.

In addition, to measure the maximum surface temperature (film formation temperature) of the joining surface 12a (14a) of the resin lid 12 (resin cap 14) during sputtering, multiple temperature measurement stickers that change color at different temperatures are attached to multiple locations on the joining surface 12a (14a), and the temperature is measured using one of the multiple temperature measurement stickers that has changed color. In this case, the multiple temperature measurement stickers can be designed so that the temperatures at which they change color differ by a predetermined temperature (e.g., 10°C). This film formation temperature measurement can be performed at the test production stage before production begins, and the operating conditions of the sputtering device can be adjusted so that the film formation temperature falls within the appropriate temperature range of 30°C to 150°C before actual production begins.

For example, when forming a metal film 15 (16) with a thickness of 0.2 μm, the power of the sputtering device should be 10 kW, the film formation time should be 14 seconds, and the surface temperature of the joining surface 12a (14a) should be 50°C to 60°C. By sputtering, a metal film 15 (16) with a thickness of 0.05 μm or more can be easily formed on the joining surface 12a (14a) of the resin lid 12 (resin cap 14).

In addition, if the thickness of the metal film 15 (16) becomes too thick, the total stress of the metal film 15 (16) becomes too large, and the metal film 15 (16) becomes more likely to peel off from the joining surface 12a (14a) of the resin lid body 12 (resin cap 14), so it is preferable to set the thickness of the metal film 15 (16) to 1 μm or less. This makes it difficult for the metal film 15 (16) to peel off from the joining surface 12a (14a) of the resin lid body 12 (resin cap 14).

For reference, the total stress of the metal film 15 (16) increases in proportion to the film thickness, as can be seen from the calculation using the following formula [1]. The greater the total stress, the more likely the metal film 15 (16) is to peel off.

Total stress = internal stress x film thickness … [1]
Internal stress = thermal stress + true stress … [2]
Here, the true stress is the stress applied to the resin lid 12 (resin cap 14), and the true stress is the same in both sputtering and thermal spraying.

The thermal stress is calculated using the following formula [3].
Thermal stress = Ef・Δα・ΔT/(1-vf) ...[3]
Here, Ef is the Young's modulus of the metal film 15 (16).

Δα is the difference in thermal expansion coefficient between the metal film 15 (16) and the resin lid body 12 (resin cap 14). Therefore, in order to reduce thermal stress, the metal film 15 (16) and the resin lid body 12 (resin cap 14) should be made of materials that have a small difference in thermal expansion coefficient between them.

ΔT is the temperature difference between the film formation temperature and room temperature. Sputtering has a lower film formation temperature than thermal spraying, so ΔT is smaller for sputtering than for thermal spraying. The film formation temperature for thermal spraying is up to 300°C, while the film formation temperature for sputtering is 30°C to 150°C.

vf is the Poisson's ratio of the metal film 15 (16). If the metal used in sputtering is the same as the metal used in thermal spraying, vf is the same for sputtering and thermal spraying.

Therefore, in order to keep the total stress of the metal film 15 (16) calculated by the above formula [1] within an appropriate range and make the metal film 15 (16) less likely to peel off, it is preferable that the metal film 15 (16) and the resin lid body 12 (resin cap 14) are formed from materials with a small difference in thermal expansion coefficient between them, and it is preferable that the film thickness of the metal film 15 (16) be 0.05 μm or more and 1 μm or less, and that the film formation temperature be 30°C or more and 150°C or less.

When manufacturing the electronic unit housing case 10 described above, the molding process of forming the resin lid body 12 (resin cap 14) having the joint surface 12a (14a) by molding the resin into a predetermined shape and then the sputtering process of forming the metal film 15 (16) having a thickness of 0.05 μm to 1 μm on at least a part of the joint surface 12a (14a) by sputtering may be performed in the company's own factory, or the company may purchase the resin lid body 12 (resin cap 14) molded by another company and only perform the sputtering process of forming the metal film 15 (16) having a thickness of 0.05 μm to 1 μm on at least a part of the joint surface 12a (14a) of the resin lid body 12 (resin cap 14) in-house.

In addition, the process of manufacturing the metal case 11 and/or the process of joining the resin lid 12 (resin cap 14) and the metal case 11 via the sealing material 17 may be performed in-house or by another company.

According to the present embodiment described above, in the joining structure in which the joining surface 12a (14a) of the resin lid body 12 (resin cap 14) and the joining surface 11a (13a) of the metal case 11 are joined via the sealing material 17, a metal film 15 (16) having a thickness of 0.05 μm or more and 1 μm or less is formed by sputtering on at least a part of the joining surface 12a (14a) of the resin lid body 12 (resin cap 14), so that the metal film 15 (16) formed on the joining surface 12a (14a) of the resin lid body 12 (resin cap 14) plays a role in strengthening the joining force between the resin lid body 12 (resin cap 14) and the metal case 11 via the sealing material 17.

In this case, the metal film 15 (16) formed on the joining surface 12a (14a) of the resin lid body 12 (resin cap 14) is formed by sputtering, so unlike the metal sprayed film in Patent Document 1, even if the metal film 15 (16) is formed without performing plasma treatment on the joining surface 12a (14a) of the resin lid body 12 (resin cap 14), the adhesive strength between the joining surface 12a (14a) of the resin lid body 12 (resin cap 14) and the metal film 15 (16) can be ensured. Moreover, since a high-purity metal film 15 (16) can be formed by sputtering, unlike the metal sprayed film in Patent Document 1, even if the sealing material 17 is applied to the surface of the metal film 15 (16) without performing plasma treatment on the surface of the metal film 15 (16), the adhesive strength of the sealing material 17 to the metal film 15 (16) is not weakened, and the adhesive strength can be ensured.

Furthermore, since the thickness of the metal film 15 (16) is set to 0.05 μm or more and 1 μm or less, the effect of increasing the adhesive strength of the metal film 15 (16) and the effect of preventing the metal film 15 (16) from peeling off from the joining surface 12a (14a) of the resin lid body 12 (resin cap 14) can be ensured. This is because if the thickness of the metal film 15 (16) is less than 0.05 μm, the thickness of the metal film 15 (16) becomes too thin and the effect of increasing the adhesive strength of the metal film 15 (16) with the seal material 17 is insufficient. On the other hand, if the thickness of the metal film 15 (16) is thicker than 1 μm, the total stress of the metal film 15 (16) becomes too large, and problems such as peeling of the metal film 15 (16) due to the difference in thermal expansion coefficient between the resin lid body 12 (resin cap 14) and the metal film 15 (16) are likely to occur.

In this case, if the thickness of the metal film 15 (16) is set to 0.2 μm or less, the total stress of the metal film 15 (16) can be appropriately reduced, so that problems such as peeling of the metal film 15 (16) due to the difference in thermal expansion coefficient between the resin lid body 12 (resin cap 14) and the metal film 15 (16) can be more reliably avoided.

In addition, in this embodiment, in the sputtering process for forming the metal film 15 (16), the deposition temperature for the metal film 15 (16) is set to 150°C or less, which makes it easier to form the metal film 15 (16) to a thickness of 1 μm or less, reduces thermal stress, and more reliably avoids problems such as peeling of the metal film 15 (16).

In this embodiment, the metal film 15 (16) is formed continuously around the entire circumference of the joining surface 12a (14a) of the resin lid body 12 (resin cap 14) by sputtering, but the metal film may be formed intermittently on the joining surface 12a (14a) by sputtering.

In addition, in this embodiment, the case is made of metal and the lid (cap) that covers it is made of resin, but the opposite configuration may be used, where the case is made of resin and the lid (cap) that covers it is made of metal. In this case, a metal film with a thickness of 0.05 μm to 1 μm is formed by sputtering on at least a portion of the joining surface of the resin case, and then the resin case and the metal lid (metal cap) are joined via a sealant.

In addition, the present invention is not limited to cases that house electronic units, but may also be cases that house things other than electronic units, and furthermore, is not limited to cases, but may be shapes other than cases. In short, as long as the structure is one in which a resin member and a metal member are joined via a sealing material, the present invention can be applied and implemented even if the shape is other than a case.

DESCRIPTION OF SYMBOLS 10...electronic unit housing case, 11...metal case (metal member), 11a...joint surface, 12...resin lid (resin member), 12a...joint surface, 13...through hole, 13a...joint surface, 14...resin cap (resin member), 14a...joint surface, 15, 16...metal film, 17...sealing material (liquid gasket)

Claims (12)

In a joining structure in which a joining surface of a resin member and a joining surface of a metal member are joined via a sealant,
The metal member is made of aluminum and formed into a case shape,
the resin member is made of polyphenylene sulfide resin and is formed into a shape that covers the opening or the through hole of the metal member,
A joint structure, characterized in that a metal film having a thickness of 0.05 μm or more and 1 μm or less is formed by sputtering on at least a part of the joint surface of the resin member. The junction structure described in claim 1, characterized in that the thickness of the metal film is 0.05 μm or more and 0.2 μm or less. The joining structure according to claim 1 or 2, characterized in that the sealing material is a liquid gasket. In a case where a joining surface of a resin member and a joining surface of a metal member are joined via a sealant,
the metal member is made of aluminum and formed in a case shape to house an electronic unit, and a joint surface is formed continuously around the entire periphery of an opening edge of the metal member;
the resin member is made of polyphenylene sulfide resin and is formed into a shape that covers the opening or the through hole of the metal member,
A case characterized in that a metal film having a thickness of 0.05 μm or more and 1 μm or less is continuously formed by sputtering over the entire periphery of the joining surface of the resin member. 1. A method for joining a joining surface of a metal member formed of aluminum in a case shape to a joining surface of a resin member formed of polyphenylene sulfide resin in a shape that covers an opening or a through hole of the metal member , the method comprising the steps of:
a sputtering step of forming a metal film having a thickness of 0.05 μm or more and 1 μm or less on at least a part of the joining surface of the resin member by sputtering;
and then a joining step of joining a joining surface of the resin member and a joining surface of the metal member via a sealant. The bonding method according to claim 5, characterized in that in the sputtering process, the metal film is formed to a thickness of 0.05 μm or more and 0.2 μm or less. The bonding method according to claim 5 or 6, characterized in that in the sputtering process, the deposition temperature of the metal film is set to 30°C or higher and 150°C or lower. The joining method according to any one of claims 5 to 7, characterized in that a liquid gasket is used as the sealing material in the joining process. A method for manufacturing a resin member having a joining surface for joining, via a sealant, to a metal member formed in an aluminum case shape, comprising:
a molding step of forming the resin member having the joining surface by molding a polyphenylene sulfide resin into a shape that covers the opening or the through hole of the metal member ;
and then a sputtering step of forming a metal film having a thickness of 0.05 μm or more and 1 μm or less on at least a part of the joining surface by sputtering. In the molding step, the resin member is molded into a case shape to accommodate an electronic unit in the resin member, and the joining surface is formed continuously around an entire periphery of an opening edge portion of the case.
10. The method for producing a resin member according to claim 9, wherein in the sputtering step, the metal film is formed continuously over the entire periphery of the joining surface. A method for manufacturing a resin member having a joining surface for joining, via a sealant, to a metal member formed in an aluminum case shape, comprising:
obtaining a resin member molded from polyphenylene sulfide resin into a shape that covers the opening or through hole of the metal member, the resin member having the joining surface;
a sputtering step of forming a metal film having a thickness of 0.05 μm or more and 1 μm or less by sputtering on at least a part of the joining surface of the obtained resin member. The method for manufacturing a resin member according to any one of claims 9 to 11, characterized in that in the sputtering process, the deposition temperature of the metal film is set to 30°C or higher and 150°C or lower.

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