JP2018094604A - Ultrasonic bonding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic bonding method of dissimilar materials that restricts deviation between a material to be bonded and a tool, so that bonding strength is improved.SOLUTION: In an ultrasonic bonding method, a body to be bonded obtained by laminating plural materials to be bonded, is subjected to ultrasonic oscillation in a pressurized state so that the materials to be bonded are joined. In the ultrasonic bonding method, on a tool side where the ultrasonic oscillation is generated, materials to be bonded that are composed of a material with a relatively low yield strength among the plural materials to be bonded or with a 0.2% yield strength are placed to be subjected to the ultrasonic oscillation. At least one of the plural materials to be bonded is preferably stainless steel.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an ultrasonic bonding method for bonding a plurality of materials to be bonded. In particular, the present invention relates to an ultrasonic bonding method suitable for bonding materials to be bonded made of different materials.

  Laser welding and caulking are attracting attention as joining methods that enable dissimilar material joining. However, these joining methods still have problems from the viewpoints of thermal effects and design properties. On the other hand, a joining technique using ultrasonic waves has attracted attention as a technique that enables new dissimilar material joining.

In general, ultrasonic bonding removes inactive layers such as adsorbed molecules and oxide layers present at the interface by friction by ultrasonic waves by applying pressure to the contact surfaces and vibrating them, and then bringing the new metal surfaces into direct contact with each other. In this state, the temperature is raised by friction, so that the components can diffuse and join at the interface. As shown in FIG. 6, two materials to be joined are stacked and sandwiched by a tool of an ultrasonic joining device. The lower plate 4 located on the lower side is supported by the tool 2 (anvil) of the ultrasonic bonding apparatus. A tool 1 (horn) that ultrasonically vibrates with respect to the upper plate 3 positioned on the upper side, and during the joining, the ultrasonic vibration from the horn 1 to the joining portion is applied while pressing the upper plate 3 and the lower plate 4. Communicated. When the horn 1 vibrates from side to side, a reaction force 8 is generated along with the movement of the horn 1, and the reaction force 8 causes friction at the joint. The heating region 5 is formed by the heat generated by the friction, and the joining is performed by the diffusion and the anchor effect occurring at the contact interface between the materials to be joined. In this way, after the ultrasonic vibration is applied for a predetermined time, the upper plate 3 and the lower plate 4 are joined.

  In order to stably apply the excitation force by ultrasonic waves to the interface of the materials to be joined, it is desired that there is little deviation between the tool and the materials to be joined when ultrasonic waves are applied. Patent Document 1 proposes the use of a tool having a convex portion corresponding to a material to be joined in order to prevent a deviation between the tool and the material to be joined in ultrasonic joining of a hard material and a soft material. Has been. However, when the method of Patent Document 1 is applied, as the ultrasonic bonding is repeated, the contact condition with the material to be bonded is changed due to wear of the tool tip, so that there is a possibility that the bonding condition varies. Moreover, since it is necessary to prepare various tools according to various materials, there also exists a subject that manufacturing cost is required.

JP 2006-212687 A

  The present invention has been devised in order to solve the above-described problems, and in a method for ultrasonic bonding of different materials, a bonding method capable of preventing a shift between a material to be bonded and a tool and improving bonding strength. The purpose is to provide.

  The present inventors have found that when applying ultrasonic vibration, the bonding strength after ultrasonic bonding differs depending on the degree of mechanical properties of the material to be bonded arranged on the side of the ultrasonically vibrating tool. It was completed. Specifically, the present invention provides the following.

(1) The present invention is an ultrasonic bonding method for bonding the materials to be bonded by applying ultrasonic vibration under pressure to a bonded body in which a plurality of materials to be bonded are laminated. Then, on the tool side that generates the ultrasonic vibration, the bonded material made of a material having a relatively low yield strength or 0.2% proof stress among a plurality of the bonded materials is disposed, This is an ultrasonic bonding method that applies sonic vibration.

(2) The present invention is the ultrasonic bonding method according to (1), wherein at least one of the materials to be bonded is stainless steel.

  ADVANTAGE OF THE INVENTION According to this invention, the joining strength of the product joined by the dissimilar material can be improved.

It is a figure which shows the test material of the ultrasonic joining test in an Example. It is a figure which shows the joining strength by which the ultrasonic joining in the Example was carried out. It is a figure which shows the relationship between joining strength and joining time. It is a figure which shows the external appearance of the test body surface after joining. It is a figure which shows the cross section of the tool impression on the test body surface. It is a schematic diagram for demonstrating the principle of ultrasonic bonding.

  Hereinafter, specific embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention.

  The present embodiment relates to an ultrasonic bonding method for bonding a plurality of materials to be bonded by ultrasonic vibration, and a material having a relatively low yield strength among the plurality of materials to be bonded on the tool side that generates ultrasonic vibrations. An ultrasonic bonding method in which the material to be bonded is disposed and ultrasonic vibration is applied.

(Material to be joined)
A material having a relatively low yield strength on the side of a tool (hereinafter also referred to as a “horn”) that generates ultrasonic vibrations when a plurality of materials to be joined are mounted on an ultrasonic bonding apparatus. It is preferable to arrange a material to be joined. When ultrasonic vibration is applied to the stacked objects to be bonded under such an arrangement relationship, slippage between the horn and the material to be bonded is suppressed by the biting between the horn and the material to be bonded, and the ultrasonic wave It is possible to effectively transmit the excitation force due to the to the bonded material interface.

  About a to-be-joined material, various metal materials, such as steel, aluminum, an aluminum alloy, copper, and a copper alloy, can be used. It is preferable that at least one material to be joined is stainless steel. Ferritic, austenitic and martensitic stainless steels can be used, and stainless steels such as SUS304 and SUS430 are preferred.

(Ultrasonic vibration)
The objects to be bonded are bonded to each other by applying ultrasonic vibration under pressure to the objects to be bonded in which a plurality of materials to be bonded are stacked. For ultrasonic bonding, conditions of a frequency of 20 kHz, an amplitude of 0 to 60 μm, and a pressing force at the start of vibration of 44 to 600 N can be used.

(Ultrasonic bonding test)
Commercially available stainless steel (SUS304, SUS304-1 / 2H, SUS430) and aluminum alloy (Al7075) having the components shown in Table 1 were used as test materials.

  Table 2 shows the mechanical properties (0.2% yield strength, tensile strength, elongation) of the test materials. The indentation depth shown in Table 2 means the depth of the indentation formed when a tool (horn) is brought into contact with one test material with a pressure of 400 N. The depth of the indentation was measured at any three locations in the contact area, and the average value was shown.

  A test material having a length of 75 mm and a width of 20 mm was cut out from a cold-rolled sheet having a thickness of 0.4 mm. The surface finish was subjected to # 400 buffing after annealing pickling. When the surface roughness of the test material after polishing was measured, Ra (arithmetic average roughness) was about 0.05 μm.

  An ultrasonic bonding test was performed using an ultrasonic bonding apparatus (manufactured by Emerson Japan). As shown in FIG. 1, two test materials, the upper plate 3 and the lower plate 4, were laminated so as to overlap each other at a length of 20 mm. In the illustrated joint 12, the horn 1 of the device was brought into contact with the upper plate side, and the lower plate side was supported by the anvil 2 of the device. Thereafter, ultrasonic vibration with a frequency of 20 kHz is generated, and the upper plate 3 and the lower plate 4 are attached by applying an ultrasonic excitation force to the vicinity of the interface 5 between the upper plate 3 and the lower plate 4 of the test material. Joined. The ultrasonic bonding test was performed by changing the ultrasonic vibration conditions in the following range.

・ Amplitude: 0 to 60 (μm)
-Joining time: 0.1 to 0.5 (s)
・ Vibration start pressure: 69-500 (N)
・ There is no pressure hold after the end of vibration.

  The upper plate 3 and the lower plate 4 of the test body 11 were bonded at the bonding interface 5 by the horn 2 and the anvil 3 of the ultrasonic bonding apparatus. As shown in FIG. 1, the contact portion 12 that comes into contact with the horn 2 is located approximately at the center of the portion where the upper plate 3 and the lower plate 4 overlap, and has a length of about 5 mm and a width of about 5 mm along the longitudinal direction. It corresponded to a size of 10 mm.

(Measurement of bonding strength)
The bonding strength was determined by measuring the shear tensile strength (MPa) according to JIS Z3136. Using a material testing machine (manufactured by Shimadzu Corporation), a tensile test was performed at a tensile speed of 5 mm / min, and the shear tensile strength was measured. The shear tensile strength was measured for three tensile test pieces, and the maximum value was adopted. The bonding area was 5 mm × 10 mm = 50 mm ² which is the contact portion of the horn. The measurement result regarding the bonding strength is shown in FIG.

(Observation of specimen surface and bonding interface)
After ultrasonic bonding, the surface state in which the upper plate and the lower plate of the test body were in contact with the ultrasonic bonding apparatus was observed with a magnifying glass. Moreover, the test body was cut | disconnected and the state of the joining interface vicinity was observed with the microscope.

(Measurement results and evaluation)
2 shows the test material No. 1 shown in Table 1. 1-No. 4 shows the shear tensile strength (hereinafter also referred to as “joining strength”) of a test body in which an upper plate and a lower plate made of 4 are combined.

<When the same type of test material is used>
First, the joint strength of the test body combining the same kind of test materials was measured, and the relationship between the joint strength and the ultrasonic amplitude was examined. As a material to be joined, test material No. 1 (SUS304), test material No. 2 (SUS430) was selected, and both the upper plate and the lower plate were subjected to ultrasonic bonding with a bonding time of 0.3 seconds and a vibration starting pressure of 280 N using a test body made of the same test material. . The amplitude was 28 μm, 35 μm, 42 μm, 49 μm, and 56 μm. The measurement result of SUS304 is shown in Reference Example 1 (-□-) in FIG. 2, and the measurement result of SUS430 is shown in the curve of Reference Example 2 (-◯-) in FIG.

  As shown in FIG. 2, each of the test materials of SUS304 and SUS430 showed a tendency that the bonding strength increased with an increase in amplitude. In the case of the test material of SUS430, the bonding strength when the amplitude was 56 μm was about 30 MPa. On the other hand, the bonding strength of SUS304 decreased when it exceeded 42 μm and showed a change having a peak value. The bonding strength of SUS430 when the amplitude of the peak value was 42 μm was slightly lower than that of SUS304.

  Next, the influence of the bonding time on the bonding strength was examined. Using a test body made of the same material of SUS304 and SUS430, the bonding strength obtained by changing the bonding time was measured. The amplitude was 56 μm, the pressure for starting vibration was 280 N, and the joining time was 0.1 seconds, 0.3 seconds, and 0.5 seconds. FIG. 3 shows the measurement results. According to FIG. 3, the test material of SUS304 showed an increase in bonding strength with an increase in bonding time, and exhibited a bonding strength of about 10 MPa at a bonding time of 0.5 seconds. On the other hand, the test material of SUS430 showed an increase in the bonding strength with an increase in the bonding time, but when it exceeded about 0.3 seconds, the bonding strength tended to decrease. For SUS430, it is assumed that the part once joined was destroyed by excessive vibration time.

<When different types of test materials are used>
Next, the bonding strength when different types of test materials were combined was measured. As shown in Table 3, test specimens were prepared in four types of combinations. In all cases, the test materials for the upper plate are different materials, while the lower plate is made of SUS430 test material for each of Invention Example 1, Comparative Example 2, and Comparative Example 3. The joining time and the vibration starting pressurizing force were performed under the same conditions as in the case of the same type of test material, and the amplitude was 42 μm where the joining strength of the test specimen according to SUS304 showed the peak value. The measurement results are shown in FIG.

  Comparative Example 1 is a combination of test materials in which the upper plate is SUS430 and the lower plate is SUS304. As shown in FIG. 2, in Comparative Example 1, the same bonding strength as that of the specimens (Reference Example 1 and Reference Example 2) made of the same material of SUS304 and SUS430 described above was obtained. On the other hand, Example 1 of the present invention in which the upper plate is combined with SUS304 and the lower plate with SUS430 test materials so as to have an inverse relationship with the combination of Comparative Example 1, the test body of Comparative Example 1 and Reference Example 1, The bonding strength was higher than that of the test piece made of the same kind of material.

  Therefore, the surface of the specimen was observed. FIG. 4 shows an example of the surface appearance of the upper and lower plates of the test specimens joined under the conditions of an amplitude of 56 μm, a joining time of 0.3 seconds, and a vibration starting pressure 280N. 4A is an example of a test body in which the upper and lower plates of SUS304 are joined, and FIG. 4B is an example of a test body in which the upper and lower plates of SUS430 are joined. As shown in FIGS. 4A and 4B, horn impressions remained on the surface of the upper plate, and anvil impressions remained on the surface of the lower plate. According to the indentation on the surface of the upper plate arranged on the horn side, the indentation of SUS430 was wider than the indentation of SUS304, and the horn slipped.

  Next, a cross section near the tool indentation on the upper plate was observed. FIG. 5 is an example of a test body joined under the conditions of an amplitude of 56 μm, a joining time of 0.3 seconds, and a vibration start pressure of 400 N. FIG. 5A shows the joining of the upper and lower plates of SUS304. 5 (b) is an example of a test body in which the upper plate and the lower plate of SUS430 are joined. As shown in (a) and (b) of FIG. 5, it was found that the test material of SUS304 has a large degree of indentation, and the amount of bite of the horn is larger than that of SUS430. As described above, SUS430 has a 0.2% yield strength (yield strength) higher than that of SUS304, so that the horn does not bite sufficiently, and slipping occurs between the horn and the test material. It is presumed that I could not tell you.

  According to the above test results, when ultrasonic bonding is performed, if the conditions such as amplitude, bonding time, vibration start pressure, etc. are the same, the material to be bonded with a low yield strength is horn compared to the material with a large yield strength. The degree of biting is large, and the grip force between the horn and the material to be joined is strong. Therefore, it is possible to efficiently transmit the excitation force to the materials to be joined, and it is considered that good joining strength can be obtained.

  When ultrasonic bonding is performed, a tool (horn) that vibrates ultrasonically contacts the upper plate, and an excitation force is applied. If slip occurs between the horn and the upper plate, a sufficient excitation force may not be applied to the joint interface. According to the mechanical properties shown in Table 2, SUS304 has a 0.2% yield strength (yield strength) smaller than SUS430. For this reason, in Example 1 of the present invention, the upper plate made of the test material of SUS304 bites the horn moderately compared to the test material of SUS430, so that the sliding between the horn and the test material is suppressed and sufficient excitation force is obtained. It is speculated that a high bonding strength was obtained.

  On the other hand, the test material of SUS430 is a material having a 0.2% yield strength (yield strength) higher than that of SUS304. Therefore, in Comparative Example 1, the horn bites into the upper plate shallowly, slipping occurs between the horn and the test material, and a sufficient excitation force is not applied to the bonding interface. It is presumed that the bonding strength was low.

  According to the above results, when ultrasonic bonding is performed using a different material to be bonded, a tool that generates ultrasonic waves from a material having a relatively low yield strength or 0.2% proof stress. It has been found that the arrangement on the side is effective in improving the bonding strength.

  Next, as shown in Table 3, in Comparative Examples 2 and 3, as in Example 1 of the present invention, the lower plate applies the test material of SUS430, while the upper plate is 0.2 higher than SUS430. An ultrasonic bonding test was performed by applying different materials having% proof stress (yield strength). In Comparative Example 2, the upper plate had the test material No. 3 (SUS304-1 / 2H) and Comparative Example 3, the upper plate is the test material No. 4 (Al7075). As shown in FIG. 2, the bonding strengths of Comparative Examples 2 and 3 were lower than those of Invention Example 1 and Comparative Example 1.

According to the above result, it is effective to improve the joining strength by arranging the material to be joined having a relatively low yield strength or 0.2% proof stress on the side of the ultrasonically vibrating tool. It could be confirmed. Furthermore, as shown in Table 3, it was found that as the 0.2% yield strength ratio (yield strength ratio) between the upper plate test material and the lower plate test material increases, the bonding strength tends to decrease. .

1 Tool (horn)
2 Tools (Anvil)
3 Upper plate 4 Lower plate 5 Heating zone 6 Pressurization 7 Ultrasonic vibration 8 Reaction force 11 Specimen 12 Contact part

Claims (2)

An ultrasonic bonding method for bonding the materials to be bonded by applying ultrasonic vibration under pressure to the objects to be bonded in which a plurality of materials to be bonded are laminated,
On the side of the tool that generates the ultrasonic vibration, the member to be bonded made of a material having a relatively low yield strength or 0.2% proof stress among a plurality of the members to be bonded is disposed, and the ultrasonic vibration An ultrasonic bonding method.   The ultrasonic bonding method according to claim 1, wherein at least one of the materials to be bonded is stainless steel.