JP7553305B2 - Manufacturing method of composite member, and composite member - Google Patents

Description

This disclosure relates to a method for manufacturing a composite member, and to a composite member.

Patent Document 1 discloses a method for manufacturing a composite member. In this manufacturing method, a composite member is manufactured by joining a metal member and a resin member. The surface of the metal member is roughened by laser processing. The resin member is joined to the roughened surface of the metal member, which creates an anchor effect and increases the flow resistance of the joint. Therefore, the composite member manufactured by these manufacturing methods has excellent joint strength and airtightness.

JP 2018-94777 A

Metals are strong compared to glass, ceramics, or resins, making them a promising base material for composite members. The manufacturing method described in Patent Document 1 leaves room for improvement in terms of further improving the bonding strength and airtightness of composite members that use metal members as base materials.

According to one aspect of the present invention, there is provided a method for manufacturing a composite member in which a metal member and a resin member are bonded together. The manufacturing method includes a laser processing step of laser processing the surface of the metal member, and a bonding step of directly bonding the resin member to the laser-processed surface of the metal member. The laser processing step forms a plurality of recesses on the surface of the metal member, each having an inner surface with a surface roughness of 20 nm or more and 1000 nm or less.

According to this manufacturing method, the surface of the metal member is laser processed. After laser processing, a plurality of recesses are formed on the surface of the metal member, which contribute to the anchor effect and the flow resistance of the joint. The plurality of recesses have an inner surface with a surface roughness of 20 nm or more and 1000 nm or less. A surface roughness of 20 nm or more increases the surface area of the metal member. This improves the anchor effect and increases the flow resistance of the joint. A surface roughness of 1000 nm or less improves the filling of the resin member into the recesses. This improves the anchor effect and increases the flow resistance of the joint. From the above, it is possible to provide a manufacturing method for a composite member with excellent joint strength and airtightness.

In one embodiment, the depth of the multiple recesses may be 15 μm or more and 60 μm or less. In this case, since the depth of the recesses is 15 μm or more, the surface area of the metal member is further increased and the flow resistance of the joint is further increased. Since the depth of the recesses is 60 μm or less, the time required for the laser processing process is shortened and productivity is improved.

In one embodiment, the laser processing step may form multiple dot-shaped recesses using a pulsed laser. In this case, the surface area of the metal component is further increased.

In one embodiment, the multiple recesses may be circular or rectangular in plan view. In the case of circular recesses, the area of the bonded interface is large and the length of the flow path at the bonded interface can be increased, so the flow path resistance can be increased. In the case of rectangular recesses, the area of the bonded interface is even larger than in the case of circular recesses. Furthermore, in the case of rectangular recesses, the flow path at the interface is bent at a right angle, so the flow path resistance can be even larger than in the case of circular recesses.

In one embodiment, the multiple recesses may have a width of 20 μm or more and 150 μm or less. The more recesses that receive the shear force, the more the load at the point of stress concentration is dispersed. However, if the width of the recesses is too small, good filling of the resin member is hindered. Therefore, by making the width of the recesses 20 μm or more and 150 μm or less, the joining strength is improved.

In one embodiment, the laser processing step may form multiple recesses at a density of 40% or more and 100% or less. In this case, the surface area of the metal component is further increased.

In one embodiment, the laser processing step may form multiple continuous groove-like recesses using a pulsed laser. In this case, damage to the metal member can be reduced.

In one embodiment, the laser processing step may arrange multiple recesses at a pitch that is greater than or equal to 1 and less than or equal to 2 times the laser spot diameter. The recesses that are actually formed are usually larger than the laser spot diameter. Therefore, with this configuration, multiple recesses can be arranged efficiently.

In one embodiment, the laser processing step may arrange multiple recesses through a wall portion that is lower than the surface of the metal member. In this case, multiple recesses can be arranged at high density.

In one embodiment, the laser processing step may arrange multiple recesses via a wall portion having the surface of the metal member as its apex. In this case, the joint surface with the resin member does not have sharp protrusions that could serve as the starting point for cracks in the resin member. This prevents cracks from occurring in the resin member.

In one embodiment, the laser processing step may form multiple recesses so that the inclination angle of the inner surface is 40 degrees or more and 80 degrees or less. In this case, since the inclination angle of the inner surface of the recess is 40 degrees or more, the flow resistance of the joint is further increased and the airtightness is further improved. Since the inclination angle of the inner surface of the recess is 80 degrees or less, destruction starting from the top of the recess is less likely to occur.

In one embodiment, the laser processing step may form a joining texture made of dross in the non-laser irradiated portion. In this case, the flow resistance of the joint is further increased, and the airtightness is further improved.

In one embodiment, the laser processing step may form a bonding texture made of an oxide in the non-laser irradiated portion. In this case, the flow resistance of the joint is further increased, and the airtightness is further improved.

In one embodiment, the material of the metal member may be iron, copper, or aluminum. In this case, iron, copper, and aluminum are materials that are easy to laser process, so that the laser processing surface for joining can be efficiently formed.

In one embodiment, the material of the resin member may be a thermoplastic resin. In this case, the resin can be filled into the recesses formed on the surface of the metal member by contacting the thermoplastic resin in a heated state with the surface of the metal member.

According to another aspect of the present disclosure, a composite member is provided. The composite member includes a metal member having an inner surface with a surface roughness of 20 nm or more and 1000 nm or less, the metal member having a surface on which a plurality of recesses are provided, and a resin member in direct contact with the surface of the metal member having the plurality of recesses.

In this composite member, the surface of the metal member is provided with multiple recesses that contribute to the anchor effect and the flow resistance of the joint. The multiple recesses have an inner surface with a surface roughness of 20 nm or more and 1000 nm or less. A surface roughness of 20 nm or more increases the surface area of the metal member. This improves the anchor effect and increases the flow resistance of the joint. A surface roughness of 1000 nm or less improves the filling of the resin member into the recesses. This improves the anchor effect and increases the flow resistance of the joint. From the above, a joint member with excellent joint strength and airtightness can be provided.

In one embodiment, in a cross section perpendicular to the surface of the metal member, the metal member may have metal spheres spaced from the inner surface and surrounded by the resin member at a density of 4 pieces/mm or more and 50 pieces/mm or less. In this case, by making the density 4 pieces/mm or more, the bonding strength and airtightness are further improved. By making the density 50 pieces/mm or less, the filling ability of the resin member into the recesses is improved.

According to one aspect and embodiment of the present disclosure, a manufacturing method for a composite member and a composite member having excellent bonding strength and airtightness are provided.

FIG. 1 is a perspective view showing a composite member according to an embodiment. 2 is a cross-sectional view of the composite member taken along line II-II in FIG. 1. FIG. 2 is a photograph showing an example of a cross section of a composite member. 4 is a flowchart of a method for manufacturing a composite member according to an embodiment. 1 is a cross-sectional view of a metal member laser-processed in a laser processing step according to an embodiment. FIG. FIG. 2 is a photograph showing an example of a surface of a metal member. FIG. 2 is a photograph showing an example of a surface of a metal member. FIG. 2 is a photograph showing an example of a surface of a metal member. FIG. 2 is a photograph showing an example of a surface of a metal member. 11 is a diagram for explaining the relationship between the diameter of a recess formed independently and the pitch. FIG. FIG. 2 is a plan view of an example of a metal member in which a rectangular recess is formed. FIG. 13 is a cross-sectional view showing a case where the diameter of a single recess is smaller than the pitch. 11 is a cross-sectional view for explaining an inclination angle of an inner surface of a recess. FIG. 13 is a cross-sectional view showing a case where the inclination angle of the inner surface of the recess is greater than 80 degrees. FIG. FIG. 2 is a top view of a mold used for injection molding. 16 is a cross-sectional view of the mold taken along line XVI-XVI in FIG. 15. 11 is a diagram for explaining the relationship between the width of a recess and the area of a region subjected to a shear force. FIG.

The following describes the embodiment with reference to the drawings. In the following description, the same or equivalent elements are given the same reference numerals, and duplicate explanations are omitted. In the present embodiment, "bonding strength" is described as "shear strength."

[Composite material]
Fig. 1 is a perspective view showing a composite member 1 according to an embodiment. As shown in Fig. 1, the composite member 1 includes a metal member 2 and a resin member 3. The composite member 1 is a member in which the metal member 2 and the resin member 3 are integrated by bonding. As an example, the metal member 2 and the resin member 3 are each a plate-shaped member. The resin member 3 is in direct contact with a surface 2a of the metal member 2. In Fig. 1, the resin member 3 is in direct contact with a portion of the surface of the metal member 2 (the contact surface 4 of the metal member 2), and has a lap joint structure.

The material of the metal member 2 is, for example, iron, copper, or aluminum. The material of the resin member 3 is, for example, a thermoplastic resin such as polyphenylene sulfide (PPS), polypropylene (PP), polyphthalamide (PPA), polybutylene terephthalate (PBT), polyamide (PA), acrylonitrile butadiene styrene (ABS), or polyether ether ketone (PEEK).

Figure 2 is a cross-sectional view of the composite member 1 taken along line II-II in Figure 1. As shown in Figure 2, the metal member 2 has a plurality of recesses 5 provided in a portion (contact surface 4) of its surface 2a. The recesses 5 have an inner surface 5a with a surface roughness (Ra) of 20 nm or more and 1000 nm or less, more preferably 20 nm or more and 500 nm or less. The surface roughness of the inner surface 5a is a linear roughness in accordance with JIS B0601:1994/2001. The surface roughness of the inner surface 5a is coarser than the surface roughness of the portion of the surface 2a where the recesses 5 are not provided.

The surface roughness of the inner surface 5a is measured, for example, by image analysis of a micrograph of the cross section of the composite member 1. The cross section of the composite member 1 is created, for example, by an ion milling device. Cutting with a grindstone or processing the cross section with a laser causes thermal effects and mechanical damage to the composite member 1. Ion milling can suppress the thermal effects and mechanical damage to the composite member 1. An example of an ion milling device that can be used is the IB-19500CP manufactured by JEOL. The surface roughness of the inner surface 5a may be measured, for example, by a white light interference microscope after the resin member 3 is removed.

As a white light interference microscope, for example, the IS-R100 manufactured by Shinto S Precision Co., Ltd. can be used. As a method for removing the resin member 3, for example, a method of dissolving it with a solvent can be used. For example, if the material of the resin member 3 is polyamide, a solvent such as aniline or ethylene chlorohydrin can be used. As a method for removing the resin member 3, a method of decomposing and removing it using atmospheric pressure plasma can also be used.

The depth of the recesses 5 is 15 μm or more and 60 μm or less, more preferably 20 μm or more and 55 μm or less. The depth of the recesses 5 is determined as the depth at the deepest position of each recess 5 with the surface 2a as the reference plane, that is, the average value of the maximum depth. The depth of the recesses 5 can also be determined by image analysis of a micrograph of the cross section of the composite member 1. The depth of the recesses 5 may be measured, for example, by a white light interference microscope after removing the resin member 3.

The multiple recesses 5 are arranged at pitch A. The multiple recesses 5 are arranged via wall portions 6. In this example, the height of the wall portions 6 is equal to the height of the surface 2a. The wall portions 6 have the surface 2a as their top. The pitch A is, for example, 20 μm or more and 150 μm or less. The pitch A is the center-to-center distance between a pair of adjacent recesses 5.

The resin member 3 is joined to the metal member 2 with a portion of the resin member 3 inserted into the recess 5. Such a structure is formed, for example, by injection molding. The composite member 1 may also be joined by a method other than injection molding, for example, press molding, vibration joining, or ultrasonic joining.

Figure 3 is a photograph showing an example of a cross section of a composite member 1 (Test Example 21 described later). As shown in Figure 3, in a cross section perpendicular to the surface 2a (see Figure 1), the metal member 2 has spherical metal 2b spaced from the inner surface 5a of the recess 5 and surrounded by the resin member 3. Although the spherical metal 2b appears to be completely surrounded by the resin member 3 in the cross section, it is actually connected to the inner surface 5a and is part of the metal member 2. In a cross section perpendicular to the surface 2a, the metal member 2 has spherical metal 2b at a density of 4 pieces/mm or more and 50 pieces/mm or less. The density of the spherical metal 2b is defined as the number of spherical metal 2b per unit length (1 mm) in a direction parallel to the surface 2a in a cross section perpendicular to the surface 2a.

As described above, in the composite member 1 according to this embodiment, the surface 2a of the metal member 2 that is in direct contact with the resin member 3 is provided with a plurality of recesses 5 that contribute to the anchor effect and the flow resistance of the joint. The plurality of recesses 5 have an inner surface 5a with a surface roughness of 20 nm or more and 1000 nm or less. The surface roughness of 20 μm or more increases the surface area of the joint of the metal member 2. As a result, when the molten resin member 3 flows into the recesses 5 and is welded to the metal member 2, the anchor effect is improved and the flow resistance of the joint is increased. The surface roughness of 1000 μm or less improves the filling of the recesses 5 with the resin member 3. As a result, the anchor effect is improved and the flow resistance of the joint is increased. From the above, a composite member 1 having excellent joint strength and airtightness can be provided.

The metal member 2 has metal spheres 2b at a density of 4 pieces/mm or more in a cross section perpendicular to the surface 2a. The metal spheres 2b are connected to the inner surface 5a of the recess 5, providing an anchor effect. This further improves the bonding strength and airtightness. By setting the density to 50 pieces/mm or less, the filling of the resin member 3 into the recess 5 is improved.

The material of the metal member 2 is, for example, iron, copper, or aluminum. Iron, copper, and aluminum are materials that are easy to laser process, so that the laser-processed surface for joining can be efficiently formed. The material of the resin member 3 is a thermoplastic resin. By contacting the heated thermoplastic resin with the laser-processed surface of the metal member 2, the resin can be filled into the recess 5 formed on the surface 2a of the metal member 2. The joining interface formed by transferring the resin into the surface roughness of the inner surface 5a of the recess 5 exerts an anchor effect, and high shear strength can be obtained. Methods for transferring the resin include injection molding and press molding using a heated mold.

[Method of manufacturing composite member]
4 is a flowchart of the manufacturing method MT of the composite member 1 according to the embodiment. As shown in FIG. 4, the manufacturing method MT includes a preparation step S10, a laser processing step S12, and a joining step S14. First, a metal member 2 is prepared in the preparation step S10. Then, a laser processing step S12 is performed to laser-process the surface 2a of the prepared metal member 2. Finally, a joining step S14 is performed to directly join the resin member 3 to the laser-processed surface 2a of the metal member 2. Details of the laser processing step S12 and the joining step S14 will be described below.

[Laser processing process]
In the laser processing step S12, for example, a pulsed laser is used. FIG. 5 is a cross-sectional view of the metal member 2 laser-processed in the laser processing step S12 according to the embodiment. FIGS. 6 to 9 are photographs showing an example of the surface 2a of the metal member 2. The photograph in FIG. 6 is an example of the surface of a metal member made of copper (JIS: C1020) (Test Example 1 described later). The photographs in FIG. 7 and FIG. 8 are examples of the surface of a metal member made of iron (JIS: SPCC) (Test Examples 9 and 13 described later). The photograph in FIG. 9 is an example of the surface of a metal member made of aluminum (JIS: A5052) (Test Example 23 described later).

In the laser processing step S12, a plurality of recesses 5 as shown in Figures 5 to 9 are formed on the surface 2a of the metal member 2. As described above, the surface roughness of the inner surface 5a of the recesses 5 is 20 nm or more and 1000 nm or less, more preferably 20 nm or more and 500 nm or less. The surface roughness of the inner surface 5a is adjusted by the laser irradiation conditions. As in the case of the composite member 1, the surface roughness of the inner surface 5a can be measured, for example, by a white light interference microscope or image analysis of a cross-sectional micrograph. The cross section of the metal member 2 is created in the same manner as the cross section of the composite member 1.

As described above, the depth of the recess 5 is 15 μm or more and 60 μm or less, and more preferably 20 μm or more and 55 μm or less. The depth of the recess 5 is adjusted by the laser irradiation conditions. As in the case of the composite member 1, the depth of the recess 5 can be measured, for example, by a white light interference microscope or image analysis of a cross-sectional micrograph.

In the laser processing step S12, a plurality of dot-shaped recesses 5 are formed by a pulsed laser. In the laser processing step S2, a plurality of recesses 5 are formed at a density of 40% or more and 100% or less. In a plan view (seen from a direction perpendicular to the surface 2a), the plurality of recesses 5 are, for example, circular (see Figures 6, 7, and 9) or rectangular (see Figure 8). The width A1 of the recesses 5 is, for example, 20 μm or more and 150 μm or less. In the case of a circular recess 5, the width A1 of the recess 5 is the diameter of the recess 5, and in the case of a rectangular recess 5, the width A1 of the recess 5 is the length of one side of the recess 5.

In the laser processing step S12, the multiple recesses 5 are arranged at a pitch A that is 1 to 2 times the laser spot diameter. For example, when the laser spot diameter is 50 μm, the pitch A is 50 to 100 μm. In the examples shown in FIGS. 6 to 9, the multiple recesses 5 are arranged in a lattice or matrix, and the pitch A is equal to each other in the vertical and horizontal directions, but the pitch A may be different from each other in the vertical and horizontal directions. The multiple recesses 5 may be arranged in a staggered pattern or randomly.

A method for forming a rectangular recess 5 will be described with reference to Figs. 10 and 11. Fig. 10 is a diagram for explaining the relationship between the diameter B of a circular recess formed alone and the pitch A. The diameter B is usually larger than the spot diameter of the laser. Fig. 11 is an example of a plan view of a metal member 2 in which a rectangular recess 5 is formed. As shown in Fig. 10, the diameter B of the single recess shown by the dashed line is larger than the pitch A (B>A), so that a recess 5 having a shape different from that of the single recess is formed. Between adjacent recesses 5, a wall portion 6 that is lower than the surface 2a, which is a non-irradiated portion, is formed. In this example, the laser processing step S12 can be said to arrange a plurality of recesses 5 via a wall portion 6 that is lower than the surface 2a. The depth C of the wall portion 6 is a depth based on the surface 2a. The wall portion 6 is lower than the surface 2a by the depth C. In this example, a plurality of recesses 5 can be arranged at high density without gaps.

As shown in FIG. 11, a plurality of rectangular recesses 5 are arranged in a lattice pattern with a pitch A. A single recess is circular as shown by the dashed line. A rectangular recess 5 is formed because the diameter B of a single recess is larger than the pitch A (B>A). Here, the pitch A is equal in the vertical and horizontal directions, so the recess 5 is square. If the pitch A is different in the vertical and horizontal directions, the recess 5 will be rectangular. In a plan view, the wall 6 is linear, constituting the four sides of the recess 5. The width A1 of the recess 5 is equal to the distance between a pair of adjacent wall portions 6. When B>A, the width A1 becomes infinitesimally close to the pitch A (A1≒A).

12 is a cross-sectional view of a single recess in which the diameter B is smaller than the pitch A. In this case, the diameter B is equal to the width A1 of the recess 5 (B=A1). As shown in FIG. 12, a wall 6 having the surface 2a, which is a non-irradiated portion, as its apex is formed between adjacent recesses 5. In this example, the laser processing step S12 can be said to arrange multiple recesses 5 via wall 6 having the surface 2a of the metal member 2 as its apex. In this configuration, the joint surface with the resin member 3 does not have a sharp protrusion that can be the starting point of a crack in the resin member 3. Therefore, cracks are suppressed from occurring in the resin member 3. This is particularly effective for hard and brittle types of resin that are prone to crack propagation. When the diameter B is equal to or smaller than the pitch A (B≦A), the smaller the pitch A, the greater the surface area of the metal member 2, improving the connection strength and adhesion as well as the airtightness.

Figure 13 is a cross-sectional view for explaining the inclination angle θ of the inner surface 5a of the recess 5. The inclination angle θ is defined as the angle between a virtual line L1 indicating the 50% depth of the recess 5 and a straight line L2 in a cross section perpendicular to the surface 2a of the metal member 2. The straight line L2 is a straight line connecting the intersection P of the inner surface 5a and the virtual line L1 to the apex 5t of the recess 5. The 50% depth of the recess 5 is calculated as a relative value based on the 100% depth and 0% depth defined below. The virtual line L1 is a straight line parallel to the surface 2a, and is set for each recess 5.

The 100% depth of the recess 5 is the depth of the bottommost part 5b of the recess 5 in a cross section perpendicular to the surface 2a. The bottommost part 5b of the recess 5 is the part that is deepest from the surface 2a in a cross section perpendicular to the surface 2a. The 0% depth of the recess 5 is the depth of the topmost part 5t of the recess 5 in a cross section perpendicular to the surface 2a. The topmost part 5t of the recess 5 is the part that is highest from the bottommost part 5b in a cross section perpendicular to the surface 2a. In other words, in a cross section perpendicular to the surface 2a, the topmost part 5t is the higher of the tops of the left and right wall surfaces that form the recess 5. The height of the topmost part 5t is equal to or lower than the surface 2a.

Figure 14 is a cross-sectional view of the recess 5 when the inclination angle θ of the inner surface 5a is greater than 80 degrees. Thus, when the inclination angle θ is greater than 80 degrees, the apex 5t is more likely to be the starting point of fracture than when the inclination angle θ is 80 degrees or less. Note that while Figure 14 only shows a single recess 5, when comparing the difference in the brittleness of the apex 5t depending on the inclination angle θ, it is necessary to match conditions other than the inclination angle θ, such as the width of the apex 5t.

In the laser processing step S12, a joining texture consisting of dross (see FIG. 7) or oxide (see FIG. 8) may be formed in the non-laser irradiated portion by laser irradiation. Dross is metal particles scattered by laser irradiation. Dross increases the surface area of the metal member 2, improving the joining strength between the metal member 2 and the resin member 3, and increasing the flow resistance of the joint, thereby improving airtightness. Oxides are metal particles scattered by laser irradiation that are oxidized by high heat. Oxides increase the surface area of the metal member 2 more than dross, further improving the joining strength, further increasing the flow resistance of the joint, and further improving airtightness. These joining textures can be formed by adjusting the laser processing conditions.

[Joining process]
For example, injection molding is performed as the joining step S14. Here, insert molding is performed. In insert molding, an insert is attached to a predetermined mold, resin is injected, and the resin is held for a predetermined time to harden. Thereafter, residual stress in the resin is removed by heat treatment. In addition to injection molding, for example, press molding, vibration bonding, or ultrasonic bonding may be performed as the joining step S14.

Figure 15 is a top view of a mold used for injection molding. Figure 16 is a cross-sectional view of the mold taken along line XVI-XVI in Figure 15. As shown in Figures 15 and 16, the mold 20 has a mold body 21 (upper mold 21a and lower mold 21b). Between the upper mold 21a and the lower mold 21b, there is a space 22 for mounting an insert (here, the metal member 2) and a space 23 into which resin is injected. A resin injection port is provided on the upper surface of the upper mold 21a. The resin injection port is connected to the space 23 via the sprue 24, the runner 25, and the gate 26. A pressure sensor 27 and a temperature sensor 28 are provided in the space 23, and detect the pressure and temperature of the space 23. Based on the detection results of the pressure sensor 27 and the temperature sensor 28, the parameters of a molding machine (not shown) are adjusted to manufacture a molded product. The parameters include the mold temperature, resin temperature during filling, filling pressure, injection rate, holding time, pressure during holding, heat treatment temperature, heat treatment time, etc. The molded product formed by the mold 20 has a lap joint structure that is joined over a specified area.

A molding machine (not shown) performs molding using the above-mentioned mold 20 as the joining step S14. First, the mold 20 is opened, the metal member 2 is attached to the space 22, and the mold 20 is closed. Then, the molding machine injects molten resin having a set resin temperature into the inside of the mold 20 from the resin injection port. The injected resin passes through the sprue 24, the runner 25, and the gate 26 and fills the space 23. The molding machine controls the filling pressure and injection rate of the resin based on the detection result of the pressure sensor 27. The molding machine controls the mold temperature to be a set value based on the detection result of the temperature sensor 28. Also, the molding machine controls the pressure to be a set value for a set retention time based on the detection result of the pressure sensor 27. Then, the molding machine performs heat treatment based on the set heat treatment temperature and heat treatment time. Then, the molding machine opens the mold 20 and takes out the composite member 1 in which the metal member 2 and the resin member 3 are integrated. When the joining step S14 is completed, the flowchart shown in FIG. 4 is completed. This produces the composite member 1 shown in Figure 1.

As described above, according to the manufacturing method MT, the surface 2a of the metal member 2 is laser processed. After the laser processing, the surface 2a of the metal member 2 is formed with a plurality of recesses 5 that contribute to the anchor effect and the flow resistance of the joint. The plurality of recesses 5 have an inner surface 5a with a surface roughness of 20 nm or more and 1000 nm or less. The surface roughness of 20 μm or more increases the surface area of the metal member 2. This improves the anchor effect, and the flow path of the joint becomes complex, increasing the flow resistance. The surface roughness of 1000 μm or less improves the filling of the resin member 3 into the recesses 5. This improves the anchor effect and increases the flow resistance of the joint. From the above, it is possible to provide a manufacturing method for a composite member 1 with excellent joint strength and airtightness.

The depth of the multiple recesses 5 is 15 μm or more and 60 μm or less. Because the depth of the recesses 5 is 15 μm or more, the surface area of the metal member 2 is further increased and the flow resistance of the joint is further increased. Because the depth of the recesses 5 is 60 μm or less, the time required for the laser processing step L2 is shortened and productivity is improved. In addition, the filling ability of the resin member 3 into the recesses 5 is further improved.

In the laser processing step L2, a pulsed laser is used to form multiple dot-shaped recesses 5. This further increases the surface area of the metal member 2. The recesses 5 are circular or rectangular in plan view. In the case of a circular recess 5, the area of the bonding interface is larger and the length of the flow path at the bonding interface can be increased, so the flow path resistance can be increased. In the case of a rectangular recess 5, the area of the bonding interface is even larger than in the case of a circular recess 5. Furthermore, in the case of a rectangular recess 5, the flow path at the interface is bent at a right angle, so the flow path resistance can be further increased compared to the case of a circular recess in which the flow path at the interface is bent gently along a circle.

The width A1 of the recess 5 is 20 μm or more and 150 μm or less. FIG. 17 is a diagram for explaining the relationship between the width of the recess and the area of the region receiving the shear force. The width A1 of the recess 5 shown in FIG. 17(a) is larger than the width A1 of the recess 5 shown in FIG. 17(b). The arrow F indicates the direction of the shear force. The hatched region of the inner surface 5a of the recess 5 receives the shear force. As can be seen from FIG. 17(a) and FIG. 17(b), the smaller the width A1, the larger the total area of the region receiving the shear force can be. This can improve the bonding strength. On the other hand, if the width A1 is too small, good filling of the resin member is hindered.

In the laser processing step L2, multiple recesses 5 are formed at a density of 40% or more and 100% or less. Since the density of the recesses 5 is 40% or more, the surface area of the metal member 2 is further increased. The density of the recesses 5 may be 60% or less. By setting the density of the recesses 5 to 60% or less, the time required for the laser processing step is shortened and productivity is improved.

In the laser processing step L2, multiple recesses 5 are arranged at a pitch between 1 and 2 times the laser spot diameter. The diameter of the recesses 5 that are actually formed is usually larger than the laser spot diameter. Therefore, with this configuration, multiple recesses 5 can be arranged efficiently.

In the laser processing step L2, multiple recesses 5 are formed so that the inclination angle θ of the inner surface 5a is 40 degrees or more and 80 degrees or less. Because the inclination angle θ is 40 degrees or more, the flow resistance of the joint is further increased so that pressure loss of the fluid occurs, and the airtightness is further improved. Because the inclination angle θ is 80 degrees or less, destruction starting from the apex 5t of the recess 5 is unlikely to occur.

Although the present embodiment has been described above, the present invention is not limited to the above embodiment, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[Modification of the laser processing process]
In the laser processing step S12, a continuous groove-shaped recess 5 may be formed. In this case, the surface roughness of the inner surface 5a of the recess 5 is 20 nm or more and 1000 nm or less. The continuous groove-shaped recess 5 may be formed by a pulse laser. In this case, damage to the metal member 2 can be reduced. In addition, the processing depth (depth of the recess 5) and the surface roughness of the inner surface 5a of the recess 5 are easily controlled. Furthermore, a metal oxide film is formed on the processed surface of the metal member 2, and oxygen atoms on the surface and the resin material are hydrogen-bonded. In laser processing, the metal surface is more likely to be oxidized because it becomes hotter than metal processing such as mechanical processing and blasting, but the oxidation of the metal surface can be suppressed by using a pulse laser. In the laser processing step S12, a plurality of groove-shaped recesses 5 may be arranged at a pitch of 1 to 2 times the spot diameter of the laser.

[Modifications of the base material and resin member]
Although the metal member 2 and the resin member 3 according to the above embodiment are shown as plate-shaped members, the shape is not limited thereto, and any shape that allows them to come into contact with each other can be adopted. The resin member 3 according to the above embodiment is in contact with a part of the surface of the metal member 2, but may be in contact with the entire surface of the metal member 2.

[Modifications of injection molding]
The injection molding is not limited to insert molding, but may be outsert molding.

Below, examples and comparative examples are described to explain the effects of the embodiments. Note that the present disclosure is not limited to these examples.

An overlapping test piece conforming to ISO19095-2:2015 was created as follows. First, multiple metal members made of copper (JIS: C1020), iron (JIS: SPCC), and aluminum (JIS: A5052) were prepared. The size of the metal members was 10 mm x 45 mm x 1.5 mm.

Next, a plurality of dot-shaped recesses were formed on the surface of each metal member by laser processing using a pulsed laser. A laser cleaner manufactured by Shinto S Precision Co., Ltd. was used for the laser processing. The laser output was 200 W, the wavelength was 1065 nm, and the laser spot diameter was 50 μm. The processing time was 30 seconds/cm2 or ^less in each case. Here, by changing the conditions such as the laser scanning pitch, the number of pulses, and the processing time, multiple types of metal members having different surface shapes were created for each material of copper, iron, and aluminum.

The surface shape of the laser-processed metal parts was measured before the joining process. For the measurement, a white light interference microscope IS-R100 manufactured by Shinto S Precision Co., Ltd. was used. The surface shape of the metal parts specifically includes the depth of the recesses, the width of the recesses, the density of the recesses, the pitch of the recesses, the surface roughness of the inner surface of the recesses, and the inclination angle of the recesses. The inclination angle of the recesses was measured by image analysis of a micrograph of the cross section of the test piece. The cross section of the test piece was created using an ion milling device IB-19500CP manufactured by JEOL. The depth of the recesses, the width of the recesses, the pitch of the recesses, the surface roughness of the inner surface of the recesses, and the inclination angle of the recesses were calculated as the average value of the values obtained by measuring at least 5% or more of the recesses formed in the joint. Here, 5% to 10% of the number of recesses were measured. In other words, when the number of recesses formed in the joint was 20,000, the average value was calculated by measuring 1,000 to 2,000 recesses.

Next, a resin member was bonded to the laser-machined surface of each metal member using the bonding device shown in Figures 15 and 16. The material of the resin member was polyphenylene sulfide (PPS). The mold temperature was 140°C, the resin temperature was 270°C, the filling pressure was 60 MPa, and the injection rate was 64.2 cm ³ /s. During holding, the holding pressure was 40 MPa, and the holding time was 8 s. During heat treatment, the heat treatment temperature was 130°C, and the heat treatment time was 2 h. Through this process, the resin member was bonded to each metal member, and test pieces 1 to 29 of the composite member were obtained. In test pieces 1 to 6, the metal member was made of copper. In test pieces 7 to 19, the metal member was made of iron. In test pieces 20 to 29, the metal member was made of aluminum.

Next, the airtightness and shear strength of the resulting composite members were evaluated. The airtightness was evaluated using a helium leak test conforming to ISO19095-3:2015. The shear strength was evaluated using a method conforming to ISO19095-2:2015.

Table 1 shows the measurement results of the surface shape of the metal member in test pieces 1 to 29, the evaluation results of the airtightness, and the evaluation results of the shear strength. In Table 1, the surface shape of the metal member is shown as the depth of the recess, the width of the recess, the density of the recess, the pitch of the recess, the surface roughness of the inner surface of the recess, and the inclination angle of the recess. The evaluation results of the airtightness are shown as "A" when the leakage amount in the helium leak test is less than 5×10 ⁻⁷ Pa·m ³ /s, and "B" when the leakage amount is 5×10 ⁻⁷ Pa·m ³ /s or more. The evaluation results of the shear strength are shown as "A" when the shear strength is 30 MPa or more, "B" when the shear strength is 20 MPa or more and less than 30 MPa, "C" when the shear strength is less than 20 MPa, and "D" when not joined.

Among test examples 1 to 6 in which the metal member was made of copper (JIS: C1020), test pieces 1 and 2 had high airtightness and shear strength. In test piece 6, the resin member was not bonded. In test piece 6, the density of the recesses was only 2.8%, and it is believed that the surface area of the metal member was too small, so the resin member was not bonded. In test pieces 3 to 5, the leakage amount was 5×10 ⁻⁷ Pa·m ³ /s or more, and the shear strength was less than 20 MPa. In test pieces 3 to 5, the density of the recesses was less than 40%, and it is believed that the surface area of the metal member was also insufficient.

Of test examples 7 to 19 in which the metal member was made of iron (JIS: SPCC), test pieces 8 to 14 had high airtightness and shear strength. The resin member did not bond to test pieces 18 and 19. It is believed that in test piece 18, the surface roughness of the inner surface of the recess exceeded 1200 nm, which deteriorated the filling of the resin member into the recess and prevented the resin member from bonding. In test piece 19, the density of the recess was only 5.2%, and the surface area of the metal member was too small, which is why the resin member did not bond.

In the test pieces 15 and 17, the leakage amount was 5×10 ⁻⁷ Pa·m ³ /s or more, and the shear strength was less than 20 MPa. In the test pieces 15 and 17, the density of the recesses was less than 40%, and it is considered that the surface area of the metal member was insufficient. In the test piece 7, the leakage amount was 5×10 ⁻⁷ Pa·m ³ /s or more, and the shear strength was less than 30 MPa. In the test piece 7, the depth of the recesses was less than 15 μm, so the flow resistance of the connection part was low, and as a result, it is considered that the airtightness was low. In the test piece 16, the leakage amount was 5×10 ⁻⁷ Pa·m ³ /s or more. In the test piece 16, the depth of the recesses exceeded 60 μm, so it is considered that the filling of the resin member into the recesses was insufficient, and the airtightness was low.

Of test examples 20 to 29 in which the metal member was made of aluminum (JIS: A5052), test pieces 20 to 24 had high airtightness and shear strength. In test pieces 28 and 29, the resin member was not bonded. In test piece 28, the surface roughness of the inner surface of the recess exceeded 1600 nm, which is thought to have deteriorated the filling of the resin member into the recess. Furthermore, in test piece 28, the density of the recess was only 6.1%, which is thought to have made the surface area of the metal member too small. In test piece 29, the surface roughness of the inner surface of the recess exceeded 2000 nm, which is thought to have deteriorated the filling of the resin member into the recess. Furthermore, in test piece 29, the depth of the recess was less than 15 μm, which is thought to have made the resin member not bonded sufficiently.

In the test pieces 25 to 27, the leakage amount was 5×10 ⁻⁷ Pa·m ³ /s or more. In the test pieces 26 and 27, the shear strength was less than 20 MPa. In the test pieces 26 and 27, the density of the recesses was less than 40%, and it is considered that the surface area of the metal member was insufficient. Furthermore, in the test piece 26, the surface roughness of the inner surface of the recesses exceeded 1000 nm, and it is considered that the filling of the resin member into the recesses was deteriorated. In the test piece 25, the depth of the recesses exceeded 60 μm, and it is considered that the filling of the resin member into the recesses was insufficient compared to the test examples 20 to 24, and the airtightness and shear strength were lower.

In test examples 18, 26, 28, and 29, where the surface roughness of the inner surface of the recess exceeds 1000 nm, it was confirmed that airtightness and shear strength were not sufficiently ensured. It was also confirmed that in test examples 3 to 6, 15, 17 to 19, and 26 to 28, where the density of the recess is less than 40%, airtightness and shear strength were not sufficiently ensured.

1...composite member, 2...metal member, 2a...surface, 2b...spherical metal, 5...recess, 5a...inner surface, 6...wall, A...pitch, θ...tilt angle.

Claims (14)

A method for manufacturing a composite member in which a metal member and a resin member are joined, comprising the steps of:
a laser processing step of laser processing a surface of the metal member;
a joining step of directly joining the resin member to the surface of the metal member that has been laser-processed;
Including,
The laser processing step includes forming a plurality of recesses having an inner surface with a surface roughness of 20 nm to 1000 nm and a depth of 15 μm to 60 μm at a density of 40% to 100% on the surface of the metal member ,
A method for manufacturing a composite member, wherein the material of the metal member is iron . The method for manufacturing a composite member according to claim 1 , wherein the laser processing step forms the plurality of dot-shaped recesses with a pulsed laser. The method for manufacturing a composite member according to claim 2 , wherein the plurality of recesses are circular or rectangular in plan view. The method for manufacturing a composite member according to claim 2 or 3 , wherein the plurality of recesses have a width of 20 μm or more and 150 μm or less. The method for manufacturing a composite member according to claim 1, wherein the laser processing step forms the multiple recesses in the form of continuous grooves using a pulsed laser. The method for manufacturing a composite member according to any one of claims 1 to 5 , wherein in the laser processing step, the plurality of recesses are arranged at a pitch that is equal to or greater than 1 time and equal to or less than 2 times a laser spot diameter. The method for manufacturing a composite member according to claim 1 , wherein the laser processing step arranges the plurality of recesses via a wall portion that is lower than a surface of the metal member. The method for manufacturing a composite member according to any one of claims 1 to 6 , wherein the laser processing step arranges the plurality of recesses via a wall portion having a top portion on the surface of the metal member. The method for manufacturing a composite member according to any one of claims 1 to 8 , wherein the laser processing step forms the plurality of recesses so that an inclination angle of the inner surface is between 40 degrees and 80 degrees. The method for manufacturing a composite member according to any one of claims 1 to 9 , wherein the laser processing step forms a joining texture made of dross in the non-laser irradiated portion. The method for producing a composite member according to any one of claims 1 to 9 , wherein the laser processing step forms a joining texture made of an oxide in the non-laser irradiated portion. The method for manufacturing a composite member according to any one of claims 1 to 11 , wherein the material of the resin member is a thermoplastic resin. A metal member having an inner surface with a surface roughness of 20 nm to 1000 nm and having a plurality of recesses with a depth of 15 μm to 60 μm provided on the surface at a density of 40% to 100% ;
a resin member in direct contact with a surface of the metal member on which the plurality of recesses are provided ,
A composite member, wherein the material of the metal member is iron . 14. The composite material according to claim 13, wherein in a cross section perpendicular to the surface of the metal member, the metal member has spherical metal particles spaced from the inner surface and surrounded by the resin member at a density of 4 particles/mm or more and 50 particles/ mm or less.

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