A method for controlling the stress-relief plate shape of copper alloy foil strip

Abstract

This invention provides a method for stress-relief and shape control of copper alloy strip foil. The method first performs medium-temperature stress-relief tension straightening on the copper alloy strip foil, with the medium temperature ranging from 480℃ to 550℃. Then, the treated copper alloy strip foil is acid-washed and wound up, followed by a secondary tension bending straightening. This method for stress-relief and shape control of copper alloy strip foil not only eliminates residual internal stress in the copper alloy strip foil using conventional air-cushion annealing furnaces, but also improves the shape, solving the current requirements for internal stress in the deep processing of copper alloy strip foil in China, especially the requirements for semi-etching in high-end frame materials. The etched copper plate does not exhibit warping or twisting.

Description

Technical Field

[0001] This invention belongs to the field of copper alloy processing technology, and specifically relates to a method for controlling the stress-relieving plate shape of copper alloy foil strips. Background Technology

[0002] Due to their excellent electrical and mechanical properties, copper alloys are commonly used in lead frames for large-scale integrated circuits. The main function of copper alloy integrated lead frames is to provide a mechanical support carrier for the chip and to serve as a conductive and thermally conductive medium. They connect the chip / device circuits to form electrical signal paths and also function as the packaging shell.

[0003] In the processing of integrated lead frames, hot and cold rolling processes can generate residual internal stress. This stress can lead to varying degrees of deformation in copper alloys during subsequent deep processing such as etching, stamping, and shearing, resulting in issues like etching warping and twisting, and inconsistent thickness during stamping. Therefore, effectively reducing residual stress in copper alloys through process adjustments without altering the material's mechanical and electrical properties remains a persistent technical challenge in the copper processing industry.

[0004] The main methods for eliminating or reducing residual internal stress in copper alloy strips and foils are bell-type annealing and continuous unfolding annealing. These processes can effectively reduce residual stress, but they cannot improve the strip shape. Improving the strip shape of copper alloy strips and foils generally involves tension bending straightening, but this method alters the state of residual stress in the strip and foil, thus failing to effectively eliminate or reduce it.

[0005] Therefore, how to eliminate the internal stress of copper alloys through process adjustments without changing the material's basic properties such as shape, mechanical properties, and electrical properties still needs to be addressed. Summary of the Invention

[0006] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. To this end, the present invention provides a method for stress-relief plate shape control of copper alloy foil strips, which eliminates the internal stress of copper alloys without changing the material's basic properties such as plate shape, mechanical properties, and electrical properties.

[0007] The first aspect of the present invention provides a method for controlling the stress-relieving plate shape of copper alloy strip foil, comprising the following steps:

[0008] S1: Perform medium-temperature stress-relieving tension straightening on the copper alloy strip foil, wherein the medium temperature range is 480℃~550℃;

[0009] S2: Pickling the copper alloy strip foil processed in step S1 and then winding it up;

[0010] S3: Perform secondary tension bending and straightening on the copper alloy strip foil after step S2.

[0011] One technical solution of the present invention regarding the stress-relieving plate shape control method for copper alloy strip foil has at least the following beneficial effects:

[0012] Regarding the stress relief plate shape control method for copper alloy strip foil, the commonly used method is to use a tensioned air cushion furnace for unfolding low-temperature continuous annealing. The annealing tension is generally 30MPa to 50MPa. However, the tension of the existing air cushion furnace annealing furnace is far from meeting the requirements. In view of the above reasons, this invention achieves the coordinated control of residual stress and plate shape of the strip foil by medium-temperature low-tension stress relief annealing combined with secondary tension bending and straightening.

[0013] The stress-relief plate shape control method of the present invention for copper alloy strip foil can not only eliminate the residual internal stress of copper alloy strip foil using the existing conventional air cushion annealing furnace, but also improve the plate shape. It solves the current requirements for internal stress in the deep processing of copper alloy strip foil in China, especially the requirements for semi-etching of high-end frame materials. The etched copper plate does not warp or twist.

[0014] The medium-temperature stress-relief tension straightening in step S1 and the secondary tension bending straightening in step S3 are processes designed based on the characteristics of residual stress distribution on the plate surface formed by medium-temperature low-tension stress-relief straightening, and their order cannot be changed.

[0015] According to some embodiments of the present invention, in step S1, during the medium-temperature stress relief tension straightening process, the unit tension is controlled to be 5MPa to 8MPa.

[0016] Below 5MPa, it is not easy to keep the foil flat during annealing; above 8MPa, the foil is prone to micro-plastic deformation at high temperature. Therefore, 5MPa to 8MPa is a suitable tension range.

[0017] According to some embodiments of the present invention, in step S1, during the medium-temperature stress relief tension straightening process, the moving speed of the copper strip is controlled to be 5m / min to 50m / min.

[0018] Controlling the copper strip's moving speed to 5m / min to 50m / min allows the copper strip sufficient time to relieve stress in a medium-temperature environment.

[0019] According to some embodiments of the present invention, in step S3, during the secondary tension bending straightening process, the unit tension is controlled to be 10MPa to 20MPa.

[0020] During the secondary tension bending process, the unit tension should be controlled between 10MPa and 20MPa. If it is below 10MPa, it will not be able to uniformly regulate the distribution of residual stress on the foil surface, nor will it be able to effectively control the shape of the plate. If it is above 20MPa, it will result in excessive residual stress on the surface. Therefore, 5MPa to 8MPa is a suitable tension range.

[0021] According to some embodiments of the present invention, the method further includes, before step S1, sequentially unwinding, degreasing, brushing once, and drying the copper alloy strip foil.

[0022] Degreasing is the process of using a degreasing agent to clean the surface of the copper strip after it has been uncoiled, removing any residual rolling oil.

[0023] The first scrubbing involves scrubbing with both cold and hot water to remove any residual degreasing solution.

[0024] According to some embodiments of the present invention, the temperature of the primary drying is 50°C to 70°C.

[0025] The purpose of drying and cleaning the copper strip is to ensure that the copper strip is dry.

[0026] According to some embodiments of the present invention, the method further includes, after step S3, performing secondary brushing, passivation, secondary drying and winding on the copper alloy strip foil in sequence.

[0027] The second washing process involves both cold and hot water washing to remove residual acid from the copper strip surface after pickling.

[0028] Passivation is the process of applying a passivating agent to the copper strip after a second cleaning.

[0029] According to some embodiments of the present invention, the temperature of the secondary drying is 50°C to 70°C.

[0030] The secondary drying process is to ensure the dryness of the wound copper strip.

[0031] According to some embodiments of the present invention, the thickness of the copper alloy foil is 0.05 mm to 0.30 mm.

[0032] According to some embodiments of the present invention, the copper alloy foil includes copper alloy foil for lead frames.

[0033] According to some embodiments of the present invention, the lead frame is made of copper alloy foil, including grades C19400 and C1850. Attached Figure Description

[0034] Figure 1 This is a schematic diagram showing the location distribution of stress test points in Examples 1 to 4. Detailed Implementation

[0035] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0036] In some embodiments of the present invention, a method for controlling the stress-relieving plate shape of copper alloy strip foil is provided, comprising the following steps:

[0037] S1: Perform medium-temperature stress-relieving tension straightening on copper alloy strip foil, with the medium temperature range being 480℃~550℃;

[0038] S2: Pickling the copper alloy strip foil processed in step S1 and then winding it up;

[0039] S3: Perform secondary tension bending and straightening on the copper alloy strip foil after step S2.

[0040] It is understandable that the common method for controlling the stress relief plate shape of copper alloy strip foil is to use a tensioned air cushion furnace for unfolding low-temperature continuous annealing, with the annealing tension generally being 30MPa to 50MPa. However, the tension of existing air cushion furnace annealing furnaces is far from meeting the requirements. In view of the above reasons, this invention achieves coordinated control of residual stress and plate shape of strip foil by medium-temperature low-tension stress relief annealing combined with secondary tension bending and straightening.

[0041] It can also be understood that the stress relief plate shape control method of the copper alloy strip foil of the present invention can not only eliminate the residual internal stress of the copper alloy strip foil by using the existing conventional air cushion annealing furnace, but also improve the plate shape, solve the current requirements of deep processing of copper alloy strip foil in China for internal stress, especially the requirements of semi-etching for high-end frame materials, and the etched copper plate does not warp or twist.

[0042] It should be noted that the medium-temperature stress relief tension straightening in step S1 and the secondary tension bending straightening in step S3 are processes designed based on the characteristics of residual stress distribution on the plate surface formed by medium-temperature low-tension stress relief straightening, and the order of the two cannot be changed.

[0043] In some embodiments of the present invention, in step S1, during the medium-temperature stress relief tension straightening process, the unit tension is controlled to be 5MPa to 8MPa.

[0044] Below 5MPa, it is not easy to keep the foil flat during annealing; above 8MPa, the foil is prone to micro-plastic deformation at high temperature. Therefore, 5MPa to 8MPa is a suitable tension range.

[0045] In some embodiments of the present invention, in step S1, during the medium-temperature stress relief tension straightening process, the moving speed of the copper strip is controlled to be 5m / min to 50m / min.

[0046] Controlling the copper strip's moving speed to 5m / min to 50m / min allows the copper strip sufficient time to relieve stress in a medium-temperature environment.

[0047] According to some embodiments of the present invention, in step S3, during the secondary tension bending straightening process, the unit tension is controlled to be 10MPa to 20MPa.

[0048] During the secondary tension bending process, the unit tension should be controlled between 10MPa and 20MPa. If it is below 10MPa, it will not be able to uniformly regulate the distribution of residual stress on the foil surface, nor will it be able to effectively control the shape of the plate. If it is above 20MPa, it will result in excessive residual stress on the surface. Therefore, 5MPa to 8MPa is a suitable tension range.

[0049] In some embodiments of the present invention, the method further includes, before step S1, sequentially unwinding, degreasing, brushing once, and drying the copper alloy strip foil.

[0050] Degreasing is the process of using a degreasing agent to clean the surface of the copper strip after it has been uncoiled, removing any residual rolling oil.

[0051] The first scrubbing involves scrubbing with both cold and hot water to remove any residual degreasing solution.

[0052] In some embodiments of the present invention, the drying temperature is 50°C to 70°C.

[0053] The purpose of drying and cleaning the copper strip is to ensure that the copper strip is dry.

[0054] In some embodiments of the present invention, the method further includes, after step S3, sequentially performing secondary washing, passivation, secondary drying, and winding on the copper alloy strip foil.

[0055] The second washing process involves both cold and hot water washing to remove residual acid from the copper strip surface after pickling.

[0056] Passivation is the process of applying a passivating agent to the copper strip after a second cleaning.

[0057] In some embodiments of the present invention, the temperature for secondary drying is 50°C to 70°C.

[0058] The secondary drying process is to ensure the dryness of the wound copper strip.

[0059] In some embodiments of the present invention, the thickness of the copper alloy foil is 0.05 mm to 0.30 mm.

[0060] In some embodiments of the present invention, the copper alloy foil includes copper alloy foil for lead frames.

[0061] In some embodiments of the present invention, the lead frame is made of copper alloy foil, including grades C19400 and C1850.

[0062] The technical solution of the present invention will be better understood below with reference to specific embodiments.

[0063] Example 1

[0064] In this embodiment, stress-relief plate shape control was performed on copper alloy strip foil with grade C19400. Performance requirements: hardness HV120-140, semi-etched.

[0065] The specific method is as follows:

[0066] Step 1, unwinding: The copper strip with a thickness of 0.3 mm is unwound, and its residual stress distribution is shown in Table 1.

[0067] The second step is degreasing: Use a degreasing agent to clean the residual rolling oil on the surface of the uncoiled copper strip.

[0068] The third step is a single scrubbing: scrub with cold and hot water separately to remove any residual degreasing solution;

[0069] Step 4, Drying: Dry the washed copper strip at 60℃ to ensure it is dry;

[0070] Step 5, medium-temperature stress relief tension straightening: Temperature: 550℃; Tension: control unit tension 8MPa; Speed: copper strip moving speed is 20m / min, allowing sufficient time for the copper strip to eliminate stress in the medium-temperature environment; its residual stress distribution is shown in Table 2.

[0071] Step 6, pickling: to eliminate slight oxidation on the surface of the copper strip after medium-temperature low-tension stress straightening;

[0072] Step 7: Roll up

[0073] Step 8: Secondary tension bending and straightening, controlling the unit tension at 18MPa;

[0074] Step 9, rinsing: Rinse with cold and hot water to remove residual acid from the copper strip surface after pickling;

[0075] Step 10, passivation: Passivate the copper strip after the second brushing with a passivating agent;

[0076] Step 11, Drying: Dry the passivated copper strip surface at 50℃ to ensure the dryness of the wound copper strip;

[0077] Step 12, winding and packaging: The dried copper strip is wound and packaged.

[0078] The distribution of its residual stress is shown in Table 3.

[0079] Table 1

[0080]

[0081] Table 2

[0082]

[0083] Table 3

[0084]

[0085] Example 2

[0086] In this embodiment, stress-relief plate shape control was performed on copper alloy strip foil with grade C19400. Performance requirements: hardness HV120-140, semi-etched.

[0087] The specific method is as follows:

[0088] The first step is uncoiling: the copper strip with a thickness of 0.254 mm is uncoiled, and the stress distribution during uncoiling is shown in Table 4.

[0089] The second step is degreasing: Use a degreasing agent to clean the residual rolling oil on the surface of the uncoiled copper strip.

[0090] The third step is a single scrubbing: scrub with cold and hot water separately to remove any residual degreasing solution;

[0091] Step 4, Drying: Dry the washed copper strip at 60℃ to ensure it is dry;

[0092] Step 5, medium-temperature stress relief tension straightening: Temperature: 550℃; Tension: control the unit tension to 8MPa; Speed: the copper strip moving speed is 25m / min, so that the copper strip has sufficient time to relieve stress in the medium-temperature environment;

[0093] Step 6, pickling: to eliminate slight oxidation on the surface of the copper strip after medium-temperature low-tension stress straightening;

[0094] Step 7: Roll up

[0095] Step 8: Secondary tension bending and straightening, controlling the unit tension at 15MPa;

[0096] Step 9, rinsing: Rinse with cold and hot water to remove residual acid from the copper strip surface after pickling;

[0097] Step 10, passivation: Passivate the copper strip after the second brushing with a passivating agent;

[0098] Step 11, Drying: Dry the passivated copper strip surface at 50℃ to ensure the dryness of the wound copper strip;

[0099] Step 12, winding and packaging: The dried copper strip is wound and packaged.

[0100] The distribution of residual stress is shown in Table 5.

[0101] Table 4

[0102]

[0103] Table 5

[0104]

[0105] Example 3

[0106] In this embodiment, stress-relief plate shape control was performed on copper alloy strip foil with grade C19400. Performance requirements: hardness HV120-140, semi-etched.

[0107] The specific method is as follows:

[0108] Step 1, Uncoiling: Uncoiling the 0.203mm thick copper strip;

[0109] The second step is degreasing: Use a degreasing agent to clean the residual rolling oil on the surface of the uncoiled copper strip.

[0110] The third step is a single scrubbing: scrub with cold and hot water separately to remove any residual degreasing solution;

[0111] Step 4, Drying: Dry the washed copper strip at 60℃ to ensure it is dry;

[0112] Step 5, medium-temperature stress relief tension straightening: Temperature: 520℃; Tension: control the unit tension at 8MPa; Speed: the copper strip moving speed is 30m / min, allowing the copper strip sufficient time to relieve stress in the medium-temperature environment;

[0113] Step 6, pickling: to eliminate slight oxidation on the surface of the copper strip after medium-temperature low-tension stress straightening;

[0114] Step 7: Roll up

[0115] Step 8: Secondary tension bending and straightening, controlling the unit tension at 15MPa;

[0116] Step 9, rinsing: Rinse with cold and hot water to remove residual acid from the copper strip surface after pickling;

[0117] Step 10, passivation: Passivate the copper strip after the second brushing with a passivating agent;

[0118] Step 11, Drying: Dry the passivated copper strip surface at 50℃ to ensure the dryness of the wound copper strip;

[0119] Step 12, winding and packaging: The dried copper strip is wound and packaged.

[0120] The distribution of its residual stress is shown in Table 6.

[0121] Table 6

[0122]

[0123] Example 4

[0124] In this embodiment, stress-relief plate shape control was performed on copper alloy strip foil with grade C18045. Performance requirements: hardness HV120-140, semi-etched.

[0125] The specific method is as follows:

[0126] Step 1, uncoiling: The copper strip with a thickness of 0.203 mm is uncoiled, and its residual stress distribution is shown in Table 7.

[0127] The second step is degreasing: Use a degreasing agent to clean the residual rolling oil on the surface of the uncoiled copper strip.

[0128] The third step is a single scrubbing: scrub with cold and hot water separately to remove any residual degreasing solution;

[0129] Step 4, Drying: Dry the washed copper strip at 60℃ to ensure it is dry;

[0130] Step 5, medium-temperature stress relief tension straightening: Temperature: 550℃; Tension: control the unit tension to 8MPa; Speed: the copper strip moving speed is 15m / min, so that the copper strip has sufficient time to relieve stress in the medium-temperature environment;

[0131] Step 6, pickling: to eliminate slight oxidation on the surface of the copper strip after medium-temperature low-tension stress straightening;

[0132] Step 7: Roll up

[0133] Step 8: Secondary tension bending and straightening, controlling the unit tension at 25MPa;

[0134] Step 9, rinsing: Rinse with cold and hot water to remove residual acid from the copper strip surface after pickling;

[0135] Step 10, passivation: Passivate the copper strip after the second brushing with a passivating agent;

[0136] Step 11, Drying: Dry the passivated copper strip surface at 50℃ to ensure the dryness of the wound copper strip;

[0137] Step 12, winding and packaging: The dried copper strip is wound and packaged.

[0138] The distribution of its residual stress is shown in Table 8.

[0139] Table 7

[0140]

[0141] Table 8

[0142]

[0143] The location distribution of stress test points in Examples 1 to 4 is as follows: Figure 1 As shown. Figure 1 In this context, TD refers to the vertical rolling direction, and RD refers to the parallel rolling direction.

[0144] As described in this article, the commonly used method for stress relief and shape control of copper alloy strip foil is to use a tensioned air cushion furnace for unfolding low-temperature continuous annealing. The annealing tension is generally 30MPa to 50MPa. However, the tension of existing air cushion furnace annealing furnaces is far from meeting the requirements. In view of the above reasons, this invention achieves coordinated control of residual stress and shape of the strip foil by medium-temperature low-tension stress relief annealing combined with secondary tension bending and straightening.

[0145] The stress-relief plate shape control method of the present invention for copper alloy strip foil can not only eliminate the residual internal stress of copper alloy strip foil using the existing conventional air cushion annealing furnace, but also improve the plate shape. It solves the current requirements for internal stress in the deep processing of copper alloy strip foil in China, especially the requirements for semi-etching of high-end frame materials. The etched copper plate does not warp or twist.

[0146] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for controlling the stress-relief plate shape of a copper alloy strip foil, characterized in that, Includes the following steps: S1: Perform medium-temperature stress-relieving tension straightening on the copper alloy strip foil, wherein the medium temperature range is 480℃~550℃; S2: Pickling the copper alloy strip foil processed in step S1 and then winding it up; S3: Perform secondary tension bending and straightening on the copper alloy strip foil after step S2; In step S1, during the medium-temperature stress-relief tension straightening process, the unit tension is controlled to be 5MPa to 8MPa.

2. The method for controlling the stress-relief plate shape of copper alloy strip foil according to claim 1, characterized in that, In step S1, during the medium-temperature stress relief tension straightening process, the moving speed of the copper strip is controlled to be 5m / min to 50m / min.

3. The method for controlling the stress-relief plate shape of copper alloy strip foil according to claim 1, characterized in that, In step S3, during the secondary tension bending straightening process, the unit tension is controlled to be 10MPa to 20MPa.

4. The method for controlling the stress-relief plate shape of copper alloy strip foil according to claim 1, characterized in that, The stress-relief plate shape control method for copper alloy strip foil further includes, before step S1, sequentially unwinding, degreasing, brushing once, and drying the copper alloy strip foil.

5. The method for controlling the stress-relief plate shape of copper alloy strip foil according to claim 4, characterized in that, The temperature for the first drying step is 50℃~70℃.

6. The method for controlling the stress-relief plate shape of copper alloy strip foil according to claim 1, characterized in that, The stress-relief plate shape control method for copper alloy strip foil further includes, after step S3, performing secondary washing, passivation, secondary drying, and winding of the copper alloy strip foil in sequence.

7. The method for controlling the stress-relief plate shape of copper alloy strip foil according to claim 6, characterized in that, The temperature for the secondary drying is 50℃~70℃.

8. The method for controlling the stress-relief plate shape of copper alloy strip foil according to any one of claims 1 to 7, characterized in that, The thickness of the copper alloy strip foil is 0.05mm to 0.30mm.

9. The method for controlling the stress-relief plate shape of copper alloy strip foil according to any one of claims 1 to 7, characterized in that, The copper alloy foil includes copper alloy foil for lead frames.

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