Manufacturing process of copper-aluminum composite belt with caulking groove structure

Abstract

The invention provides a manufacturing process of a copper-aluminum composite belt with a caulking groove structure, and relates to the field of copper-aluminum composite materials. The manufacturing process comprises the following steps: S1, preparing a special-shaped copper strip; the upper plate surface of the special-shaped copper strip is a convex arc surface, the lower plate surface of the special-shaped copper strip is a plane or a concave arc surface, and the width of the upper plate surface is greater than that of the lower plate surface; at least one caulking groove is formed in the lower plate surface, the groove bottom surface of the caulking groove is a concave arc surface, and at least one of the two groove edge surfaces inclines outwards; s2, the lower plate face, provided with the caulking groove, of the special-shaped copper strip is placed on the molten aluminum, and the special-shaped copper strip obliquely enters the roll gap in the length direction of the caulking groove to be subjected to cast-rolling compounding with the molten aluminum; after casting and rolling compounding, ensuring that the two groove edge surfaces are inclined outwards; s3, cold rolling and annealing; and S4, forming processing. According to the invention, the groove bottom angle and the groove top angle of the caulking groove are obtuse angles after cast rolling, so that the stress generated in a corner area when molten aluminum is solidified is reduced, and the anti-stripping performance of the copper-aluminum composite belt is effectively improved.

Description

Technical Field

[0001] The present invention specifically relates to a manufacturing process of a copper-aluminum composite strip with an embedded groove structure, and relates to the field of copper-aluminum composite materials. Background Art

[0002] Copper-aluminum composite materials combine the respective advantages of copper and aluminum materials, and have the characteristics of high conductivity, thermal conductivity, light weight, corrosion resistance, and low overall cost. They are widely used in electricity, semiconductors, electronic devices, new energy vehicles and other fields.

[0003] There are many kinds of copper-aluminum composite materials, and they need to be processed into copper-aluminum composite materials of different shapes and structures according to customer requirements, such as copper-aluminum composite strips with embedded groove structures. Figure 1 , a copper-aluminum composite strip with an embedded groove structure, which uses a copper strip with an embedded groove structure as a base material, and uses a copper-aluminum solid-liquid composite process to composite a layer of aluminum material on the copper strip. The copper-aluminum solid-liquid composite process is a composite process in which a copper strip is covered on semi-molten aluminum liquid for casting and rolling. Compared with the mechanical press-in embedding process, the copper-aluminum solid-liquid composite process has the advantages of higher interface bonding strength, lower production cost, and suitability for continuous production.

[0004] Refer to the attached Figure 2 Setting up the embedded groove structure can increase the contact area and heat dissipation of copper and aluminum. However, in actual testing, it was found that the copper-aluminum composite belt had defects at the four corners of the embedded groove structure. Among them, the defect at the corner of point A was the largest, and the defect at the corner of point B was smaller than the defect at the corner of point A. After loading the test force, peeling first occurred at the corner of point A of the embedded groove structure. In further tests, it was found that the smaller the corner, the larger the defect, and the easier it was for copper and aluminum to peel off. Summary of the invention

[0005] In order to overcome the deficiencies in the background technology, the present invention discloses a manufacturing process for a copper-aluminum composite strip with an embedded groove structure, the purpose of which is to solve the problem of defects in the embedded groove part in the prior art, which easily causes copper-aluminum peeling.

[0006] The present invention adopts the following technical solution: Technical Solution 1: A manufacturing process of a copper-aluminum composite strip with an embedded groove structure, comprising the following steps: S1: preparing a special-shaped copper strip; when viewed from the cross-sectional direction, the upper plate surface of the special-shaped copper strip is a convex arc surface, the lower plate surface is a plane or a concave arc surface, the width of the upper plate surface is greater than the width of the lower plate surface; at least one embedding groove is provided on the lower plate surface, the bottom surface of the embedding groove is a concave arc surface, and at least one of the two groove side surfaces is inclined outward; S2: placing the lower plate surface of the profiled copper strip with the embedded groove on the aluminum liquid, and making the profiled copper strip tilt along the length direction of the embedded groove into the roller gap to perform cast-rolling compounding with the aluminum liquid; after the cast-rolling compounding, ensure that both groove edges are tilted outwards; S3: cold rolling and annealing; S4: Forming process.

[0007] The present invention adopts special-shaped copper strip, and its beneficial effects are as follows: 1. The disadvantage of copper-aluminum casting and rolling is that stress will be generated in the corner area after the aluminum liquid solidifies, especially in the acute angle or right angle. The smaller the angle, the greater the stress. The present invention can make the bottom angle and top angle of the groove become obtuse angles after casting and rolling, reducing the stress generated in the corner area when the aluminum liquid solidifies, and effectively improving the anti-peeling performance of the copper-aluminum composite belt.

[0008] 2. The obtuse angle structure increases the contact area between the aluminum liquid and the groove edge, which is beneficial to improving the bonding strength and conductivity of the copper-aluminum composite.

[0009] 3. The upper plate surface is a convex arc surface, so that the thickness of the middle part of the special-shaped copper strip is greater than that of the two sides. When casting and rolling with aluminum liquid, the casting roller can generate a greater rolling force at the embedded groove part, which is beneficial to improve the composite strength of aluminum liquid at the embedded groove part.

[0010] 4. The special-shaped copper strip enters the roll gap along the length direction of the embedded groove and is cast and rolled with the aluminum liquid, so that the rolling deformation part of the special-shaped copper strip first appears at the part with higher convex arc surface, and then extends to both sides, which is beneficial to improve the composite strength of the lower plate surface, embedded groove and aluminum liquid.

[0011] 5. The special-shaped copper strip is tilted into the roller gap along the length direction of the embedding groove, which is conducive to completely discharging the air between the special-shaped copper strip and the aluminum liquid, and improving the bonding strength and conductivity of the copper-aluminum composite.

[0012] Improved technical solution 2 based on technical solution 1: the width of the upper plate surface is greater than the width of the lower plate surface.

[0013] After implementing Technical Solution 2, the beneficial effect is as follows: the width of the upper plate surface is greater than the width of the lower plate surface, so that an obtuse angle is formed between the lower plate surface and the side plate surface, and an acute angle is formed between the upper plate surface and the side plate surface, thereby transferring the stress weak point from the obtuse angle to the acute angle, ensuring the composite strength of the bottom of the groove and the aluminum liquid.

[0014] Improved technical solution 3 based on technical solution 1 or 2: In S1, a rounded corner is set between the lower panel surface and the side panel surface.

[0015] After implementing Technical Solution 3, the beneficial effect is that compared with the blunt angle, the aluminum liquid will produce smaller stress after solidification at the rounded corner.

[0016] Improved technical solution 4 based on technical solution 2: the angle between the lower panel surface and the side panel surface is 110-150°.

[0017] After implementing technical solution 4, the beneficial effect is: the larger the sharp angle, the smaller the stress, but too large an angle will cause material waste. The angle of 110-150° combines the composite strength and economy of the copper-aluminum composite strip.

[0018] Improved technical solution 5 based on technical solution 1: In S1, a continuous extrusion or rolling process is used to prepare special-shaped copper strip.

[0019] After implementing technical solution 5, the beneficial effect produced is that the special-shaped copper strip can be efficiently prepared by using a continuous extrusion process or a special-shaped roller rolling process.

[0020] Improved technical solution 6 based on technical solution 1: In S2, the special-shaped copper strip is cleaned and shot blasted before casting and rolling.

[0021] After implementing technical solution 6, the beneficial effects are: cleaning can remove the oxide film, grease, and impurities on the surface of the special-shaped copper strip, which is beneficial to improving the wettability and composite strength of the special-shaped copper strip and the aluminum liquid. Shot blasting can form tiny concave and convex surfaces on the surface of the special-shaped copper strip, which is beneficial to increasing the composite area of ​​the special-shaped copper strip and the aluminum liquid.

[0022] Improved technical solution 7 based on technical solution 1: In S4, the forming process includes milling, slitting and grinding.

[0023] After implementing Technical Solution 7, the beneficial effect is that copper-aluminum composite strips for different purposes have different forming requirements, and can be made to meet the use requirements of different copper-aluminum composite strips through milling, slitting and grinding.

[0024] Improved technical solution 8 based on technical solution 7: In S4, during milling, the copper-clad surface is first milled with the aluminum-clad surface of the copper-aluminum composite strip as a reference to ensure the distance from the bottom surface of the groove to the copper-clad surface, and then the aluminum-clad surface is milled with the copper-clad surface as a reference to ensure the final thickness of the copper-aluminum composite strip.

[0025] After implementing Technical Solution 8, the beneficial effect produced is that the milling process can ensure the size requirements of the copper-aluminum composite strip. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Attached Figure 1 Shown is a schematic diagram of the overall structure of the copper-aluminum composite strip.

[0027] Attached Figure 2 The attached Figure 1 Schematic diagram of the local structure.

[0028] Attached Figure 3Shown is a schematic diagram of the special-shaped copper strip in Example 1.

[0029] Attached Figure 4 Shown is a schematic diagram of copper-aluminum casting and rolling bonding.

[0030] Attached Figure 5 Shown is a front view of a profiled copper strip as it enters the roll gap.

[0031] Attached Figure 6 Shown is a side view of a profiled copper strip as it enters the roll gap.

[0032] Attached Figure 7 Shown is a schematic diagram of the structure of the copper-aluminum composite strip after cast-rolling composite.

[0033] Attached Figure 8 Shown is a schematic diagram of edge milling of a copper-aluminum composite strip.

[0034] Attached Fig. 9 Shown is a schematic diagram of the special-shaped copper strip in Example 2.

[0035] Attached Fig.10 Shown is a schematic diagram of the structure of the copper-aluminum composite strip after cast-rolling composite in Example 2.

[0036] Attached Fig.11 Shown is a schematic structural diagram of a high-voltage connector in Example 3.

[0037] Attached Fig.12 Shown is a schematic diagram of the special-shaped copper strip in Example 3.

[0038] Attached Fig.13 Shown is a schematic diagram of the structure of the copper-aluminum composite strip after cast-rolling composite in Example 3.

[0039] Attached Fig.14 Shown is a schematic diagram of milling a copper-aluminum composite strip.

[0040] Attached Fig.15 Shown is a schematic diagram of slitting a copper-aluminum composite strip.

[0041] In the attached figure: 1. Copper-aluminum composite strip; 1.1. Copper-clad surface; 1.2. Aluminum-clad surface; 1.3. Copper strip; 1.4. Aluminum insert; 2. Special-shaped copper strip; 2.1. Upper plate surface; 2.2. Lower plate surface; 2.3. Side plate surface; 2.4. Groove bottom surface; 2.5. Groove side surface; 2.6. Fillet; 3. Furnace; 4. Casting nozzle; 5. Molten aluminum; 6. Casting roller. DETAILED DESCRIPTION

[0042] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these preferred embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. It should be noted that in the description of the present invention, the terms "front", "rear", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and other terms indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description, and does not indicate or imply that the device or component must have a specific orientation and positional relationship, and therefore cannot be understood as a limitation of the present invention. It should also be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the internal connection of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0043] Embodiment 1: again refer to the attached Figure 1 A copper-aluminum composite belt for heat dissipation of electronic devices. The copper-aluminum composite belt uses copper belt as the base material and is composited with aluminum material. The copper-coated surface is the conductive surface, and the aluminum-coated surface is the heat dissipation surface. Although the electrical conductivity and thermal conductivity of aluminum are not as good as those of copper, aluminum heats up faster and has a greater temperature difference with the environment. Under the same air volume, aluminum has better heat dissipation than copper. A plurality of embedded grooves are provided in the copper belt, which increases the contact area between copper and aluminum and improves the heat dissipation of the copper-aluminum composite belt.

[0044] The manufacturing process of the copper-aluminum composite strip comprises the following steps: S1: Preparation of special-shaped copper strip Refer to the attached Figure 3 . Observed from the cross-sectional direction, the upper plate surface 2.1 of the special-shaped copper strip 2 is a convex arc surface, and the lower plate surface 2.2 is a flat surface. A plurality of embedded grooves are provided on the lower plate surface 2.2 (for the convenience of showing the details, see the attached Figure 3 Only five grooves are shown in the figure). The groove bottom surface 2.4 of the groove is a concave arc surface. The groove side surfaces 2.5 of the groove located in the middle are both inclined outwards; the groove side surfaces 2.5 of the grooves located on both sides are perpendicular to the lower plate surface 2.2, and the groove side surfaces 2.5 close to the outside are inclined outwards and form an obtuse angle with the lower plate surface 2.2.

[0045] The preparation of the special-shaped copper strip can adopt a continuous extrusion process or a rolling process. Both processes can efficiently prepare the special-shaped copper strip 2. In addition, the special-shaped copper strip 2 should be cleaned and shot blasted before casting and rolling. Pickling can remove the oxide film, grease, and impurities on the surface of the special-shaped copper strip, which is beneficial to improving the wettability and composite strength of the special-shaped copper strip and the aluminum liquid. Shot blasting can form tiny concave and convex surfaces on the surface of the special-shaped copper strip, which is beneficial to increase the composite area of ​​the special-shaped copper strip and the aluminum liquid.

[0046] S2: Casting and rolling composite Refer to the attached Figure 4 The casting and rolling equipment includes a melting furnace 3, a casting nozzle 4 and a pair of casting and rolling rollers 6, and the profiled copper strip 2 is arranged on one side of the roller gap entrance. During the casting and rolling compounding, the lower plate surface 2.2 of the profiled copper strip 2 with the embedded groove is placed on the aluminum liquid 5, and the profiled copper strip 2 is tilted along the length direction of the embedded groove to enter the roller gap and cast and roll compound with the aluminum liquid 5.

[0047] Refer to the attached Figure 5 and attached Figure 6 . The special-shaped copper strip 2 is tilted into the roller gap along the length direction of the embedded groove, which is conducive to completely discharging the air between the special-shaped copper strip 2 and the aluminum liquid 5, and improving the bonding strength and conductivity of the copper-aluminum composite. Secondly, since the upper plate surface 2.1 is a convex arc surface and the groove bottom surface 2.4 of the embedded groove is a concave arc surface, the thickness of the middle part of the special-shaped copper strip 2 is greater than that of the two sides. When casting and rolling with the aluminum liquid 5, the casting roller 6 can generate a greater rolling force at the embedded groove part, which is conducive to improving the composite strength of the aluminum liquid 5 at the embedded groove part. More importantly, the rolling of the special-shaped copper strip 2 by the casting roller 6 is not only thinning in the thickness direction, but also extending in the width direction and length direction. The rolling deformation part first appears in the part with a higher convex arc surface (upper plate surface), and then extends to both sides (width direction).

[0048] Refer to the attached Figure 7 , attached Figure 7 The structure diagram of the copper-aluminum composite strip after casting and rolling is shown. Figure 7It can be seen that after the profiled copper strip 2 is rolled by the casting roller 6, the upper plate surface 2.1 is rolled from a convex arc surface to a flat surface, and the groove bottom surface 2.4 of the embedded groove is also rolled from a concave arc surface to a flat surface. Since the casting roller 6 has an extension effect on the profiled copper strip 2 in the width direction, the inclination angles of the two groove side surfaces 2.5 of the embedded groove located in the middle are basically unchanged. The groove side surfaces 2.5 close to the inner side of the embedded groove located on both sides are tilted outward from the original vertical state, and the outward tilt angle of the groove side surfaces 2.5 close to the outer side is decreasing. In this way, the two groove side surfaces 2.5 of all embedded grooves are tilted outward in an open state, and the groove bottom angle and groove top angle are both obtuse angles. It is also worth noting that since the upper plate surface 2.1 is a convex arc surface and the lower plate surface 2.2 is a plane, the extension length of the upper plate surface 2.1 after casting is greater than the extension length of the lower plate surface 2.2, and an obtuse angle structure is also formed between the lower plate surface 2.2 and the side plate surface 2.3.

[0049] After solidification, aluminum liquid will generate stress at the corners, especially at acute angles or right angles. The smaller the angle, the greater the stress. The area where stress concentration exists is the weak area, just like unpacking a box, the film with the tightest edge is the easiest to tear. After casting and rolling, the present invention can make the two groove edges of the embedded groove tilt outward, and the bottom angle and the top angle of the groove are both obtuse, which effectively reduces the stress generated in the corner area of ​​the embedded groove when the aluminum liquid solidifies.

[0050] After casting and rolling, the lower plate surface 2.2 and the side plate surface 2.3 form an obtuse angle, and the upper plate surface 2.1 and the side plate surface 2.3 form an acute angle, which is equivalent to transferring the stress weak point from the obtuse angle to the acute angle. Therefore, the defect at the corner of point D is greater than the defect at the corner of point C. The corner of point D is the largest defect in this area and is most prone to copper-aluminum peeling.

[0051] Again refer to the attached Figure 2 Attached Figure 2 The reason why the two groove edges of the middle groove are tilted to one side is that the extension of the casting roll to the profiled copper strip in the width direction is not taken into account, resulting in an acute angle at the corner of point A and an obtuse angle at the corner of point B. After the test force is loaded, the peeling first appears at the corner of point A of the groove structure, and then extends to other parts.

[0052] S3: Cold rolling and annealing Cold rolling can further reduce the thickness of the copper-aluminum composite strip and improve the quality of the plate shape. The role of annealing is to reduce rolling stress.

[0053] S4: Forming Refer to the attached Figure 8 In this embodiment, the forming process is edge milling. The corners at point C and point D have defects, and the corner at point D is the largest weak point in the area, so the area most prone to copper-aluminum peeling can be milled off by edge milling.

[0054] Example 2: Refer to the attached Fig. 9 and attached Fig.10 The special-shaped copper strip in this embodiment is different from that in Embodiment 1 in that: 1. The width of the upper plate surface 2.1 is greater than that of the lower plate surface 2.2, and an obtuse angle structure is formed between the lower plate surface 2.2 and the side plate surface 2.3, and an acute angle structure is formed between the upper plate surface 2.1 and the side plate surface 2.3. After casting and rolling, the acute angle will become smaller and the obtuse angle will become larger, thereby transferring the stress weak point from the obtuse angle to the acute angle, ensuring the composite strength of the special-shaped copper strip and aluminum.

[0055] 2. The angle between the lower plate surface 2.2 and the side plate surface 2.3 is 110-150°. The larger the angle, the smaller the stress, but too large an angle will cause waste of materials. The angle of 110-150° combines the composite strength and economy of the copper-aluminum composite strip.

[0056] 3. A fillet 2.6 is provided between the lower plate surface 2.2 and the side plate surface 2.3. After the fillet is provided, the aluminum liquid will generate smaller stress after solidification at the fillet 2.6.

[0057] 4. The lower plate surface 2.2 is a concave arc surface. Compared with the plane, the lower plate surface is a concave arc surface, which offsets the extension of the casting roller on the special-shaped copper strip in the width direction to a certain extent.

[0058] 5. The two groove side surfaces 2.5 of the embedded grooves on both sides are inclined inwards, and the inward inclination angle of the groove side surface close to the center line is smaller than the inward inclination angle of the groove side surface far from the center line. After casting and rolling, the inward inclination angle of the groove side surface 2.5 close to the center line will increase, and the inward inclination angle of the groove side surface 2.5 far from the center line will decrease, so as to ensure that the embedded groove has a better symmetrical structure after casting and cold rolling.

[0059] Example 3: Refer to the attached Fig.11 . A high-voltage connector made of a copper-aluminum composite strip, which is used to connect lithium batteries for new energy vehicles. The high-voltage connector uses a copper strip 1.3 as a conductive substrate, and a groove with a depth of 1mm and a width of 12mm is processed on the copper strip 1.3, and an aluminum insert 1.4 is compounded in the groove. After copper and aluminum are compounded, the aluminum insert 1.4 and the copper strip 1.3 are required to have good conductivity and bonding strength. The reason why the aluminum insert 1.4 is embedded in the copper strip 1.3 is that copper has poor weldability and aluminum needs to be used as a welding material.

[0060] The manufacturing process of the copper-aluminum composite strip 1 comprises the following steps: S1: Preparation of special-shaped copper strip Refer to the attached Fig.12 The special-shaped copper strip in this embodiment is different from that in Embodiment 1 in that the groove bottom surface 2.4 of the embedding groove has an inner arc surface with a larger curvature.

[0061] S2: Casting and rolling composite Refer to the attached Fig.13 . Fig.13 It can be seen that the curvature of the inner arc surface will become smaller after casting and rolling, but the groove bottom surface 2.4 is still an arc surface, so that the groove bottom angle is larger than the groove top angle, which in disguise transfers the stress weak point from the groove bottom angle to the groove top angle.

[0062] S3: Cold rolling and annealing S4: Forming The difference between this embodiment and embodiment 1 is that the forming process includes milling, slitting and grinding steps.

[0063] S4.1: Milling Refer to the attached Fig.14 First, the copper-clad surface 1.1 is milled based on the aluminum-clad surface 1.2 of the copper-aluminum composite strip 1 to ensure the distance from the groove bottom surface 2.4 to the copper-clad surface 1.1, and then the aluminum-clad surface 1.2 is milled based on the copper-clad surface 1.1 to remove the weak area at the top corner of the groove while ensuring the final thickness of the copper-aluminum composite strip 1.

[0064] S4.2: Slitting Refer to the attached Fig.15 The copper-aluminum composite strip 1 is cut by a precision cutting machine so that the cut strips meet the design requirements of the high-voltage connector.

[0065] S4.3: Polishing.

[0066] It should be understood that the embedding groove of the present invention is not limited to the above-mentioned shape, but may also be other shapes such as a T-slot, a dovetail slot, etc.

[0067] It is worth noting that the contents not described in detail in the above embodiments are prior art. It is also worth noting that for those skilled in the art, any addition, subtraction, replacement and improvement made under the structure and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A process for manufacturing a copper-aluminum composite strip with an embedded groove structure, characterized in that: The following steps are involved: S1: preparing a special-shaped copper strip; when viewed from the cross-sectional direction, the upper plate surface of the special-shaped copper strip is a convex arc surface, and the lower plate surface is a plane or a concave arc surface; at least one embedding groove is provided on the lower plate surface, the bottom surface of the embedding groove is a concave arc surface, and at least one of the two groove side surfaces is inclined outward; S2: placing the lower plate surface of the profiled copper strip with the embedded groove on the aluminum liquid, and making the profiled copper strip tilt along the length direction of the embedded groove into the roller gap to perform cast-rolling compounding with the aluminum liquid; after the cast-rolling compounding, ensure that both groove edges are tilted outwards; S3: cold rolling and annealing; S4: Forming process.

2. A process for manufacturing a copper-aluminum composite strip with an embedded groove structure as claimed in claim 1, characterized in that: In S1, the width of the upper plate surface is greater than the width of the lower plate surface.

3. A process for manufacturing a copper-aluminum composite strip with an embedded groove structure as claimed in claim 1 or 2, characterized in that: In S1, a rounded corner is provided between the lower plate surface and the side plate surface.

4. A process for manufacturing a copper-aluminum composite strip with an embedded groove structure as claimed in claim 2, characterized in that: The angle between the lower panel surface and the side panel surface is 110-150°.

5. The manufacturing process of the copper-aluminum composite strip with an embedded groove structure according to claim 1, characterized in that: In S1, a continuous extrusion or rolling process is used to prepare the special-shaped copper strip.

6. A process for manufacturing a copper-aluminum composite strip with an embedded groove structure as claimed in claim 1, characterized in that: In S2, the special-shaped copper strip is cleaned and shot blasted before casting and rolling.

7. A process for manufacturing a copper-aluminum composite strip with an embedded groove structure as claimed in claim 1, characterized in that: In S4, forming processing includes milling, slitting and grinding.

8. A process for manufacturing a copper-aluminum composite strip with an embedded groove structure as claimed in claim 7, characterized in that: During milling, the copper-clad surface is first milled based on the aluminum-clad surface of the copper-aluminum composite strip to ensure the distance from the bottom surface of the groove to the copper-clad surface, and then the aluminum-clad surface is milled based on the copper-clad surface to ensure the final thickness of the copper-aluminum composite strip.

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