A method for improving the surface flatness of an etching-type heat dissipation alloy strip

Abstract

This invention relates to a method for improving the surface flatness of etched heat-dissipating alloy strips, comprising: sequentially performing a first leveling treatment and a second leveling treatment on the etched heat-dissipating alloy strips; wherein, the first leveling treatment includes: stacking several etched heat-dissipating alloy strips into an etched heat-dissipating alloy strip group, and applying a compressive stress of 20kg-500kg to the etched heat-dissipating alloy strip group at an annealing temperature of 100℃-400℃, maintaining it for 1h-5h, to perform the first leveling treatment on the etched heat-dissipating alloy strips; the second leveling treatment includes: passing the etched heat-dissipating alloy strip after the first leveling treatment through a leveling device several times at a speed of 5m / min-30m / min, to perform the second leveling treatment on the etched heat-dissipating alloy strips; the leveling device includes: several pairs of leveling rollers. The surface flatness improvement method of this invention, through the first leveling treatment and the second leveling treatment, can fully meet the flatness index requirements and stability requirements of etched heat-dissipating alloy strips.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal smelting and processing technology, and in particular to a method for improving the surface flatness of etched heat dissipation alloy strips. Background Technology

[0002] As microelectronic devices such as smartphones continue to evolve towards ultra-thin and high-performance designs, the energy consumption of internal electronic components is also increasing. The heat generated during operation can easily accumulate rapidly, leading to high temperatures that directly affect the performance, reliability, and lifespan of electronic devices. Therefore, the heat dissipation performance of heat dissipation modules in microelectronic devices is crucial. The heat dissipation materials used in these modules are primarily copper or aluminum alloy strips, often etched into plates, sheets, or multiple sheets. To ensure good heat dissipation, the etched copper and aluminum heat dissipation sheets are required to have high surface flatness. This ensures a high degree of contact and stability between the heat source (such as the CPU chip) and the heat sink, thus solving the problem of localized overheating of heat-generating electronic components. Generally, etching manufacturers require the surface flatness of the heat dissipation alloy strip to be less than 0.1 mm, with the etched surface requiring a flatness of less than 0.05 mm.

[0003] Currently, the main methods for maintaining the surface flatness of etched heat dissipation alloy strips are: ① Performing online stress-relief annealing on the etched heat dissipation alloy strips, by adjusting parameters such as annealing temperature, annealing speed, and tension, to release the internal processing stress of the etched heat dissipation alloy strips, thereby improving the surface flatness of the etched heat dissipation alloy strips; ② Performing leveling annealing on the etched heat dissipation alloy strips using a specific leveling annealing device, where after the etched heat dissipation alloy strips soften at high temperatures, vertical pressure is applied to the etched heat dissipation alloy strips by a pressure block to correct and improve the surface flatness of the etched heat dissipation alloy strips.

[0004] For example, patent CN115287495A discloses a copper alloy strip for a semi-etched lead frame and its preparation method, which involves adjusting the annealing temperature to 470℃-520℃, the annealing speed to 70-90m / min, and the straightening tension to 200N / mm. 2 -300N / mm 2 To ensure that the plate shape of the copper alloy strip is no higher than 3I and the warpage of the lead frame after semi-etching is no higher than 0.10mm, the equipment investment is high and it is difficult to guarantee that all the processing internal stress is released. The residual processing internal stress will still lead to poor surface flatness, so the surface flatness is unstable.

[0005] For example, patent CN111500843A discloses a leveling and annealing fixture and process for metal substrates used in electronic packaging. By using a specific leveling and annealing fixture, the etched heat dissipation alloy strip is kept at 800°C for 1 hour to achieve a good leveling effect. However, since the annealing temperature is higher than the recrystallization temperature, it will affect the structure and properties of the material, which is not conducive to the use of the heat dissipation strip.

[0006] Therefore, there is an urgent need for a method to improve the surface flatness of etched heat dissipation alloy strips. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for improving the surface flatness of etched heat dissipation alloy strips.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The first aspect of the present invention is to provide a method for improving the surface flatness of an etched heat dissipation alloy strip, comprising:

[0010] The etched heat dissipation alloy strip is subjected to a first leveling treatment and a second leveling treatment in sequence; wherein,

[0011] The first leveling process includes: stacking several of the etched heat dissipation alloy strips into an etched heat dissipation alloy strip group, and applying a compressive stress of 20kg-500kg to the etched heat dissipation alloy strip group at an annealing temperature of 100℃-400℃, and maintaining it for 1h-5h, so as to perform the first leveling process on the etched heat dissipation alloy strips.

[0012] The second leveling process includes: passing the etched heat dissipation alloy strip after the first leveling process through the leveling device several times at a speed of 5m / min-30m / min to perform a second leveling process on the etched heat dissipation alloy strip.

[0013] The leveling device includes several pairs of leveling rollers.

[0014] The surface flatness of alloy strip is mainly related to its shape and residual stress. Poor shape determines poor macroscopic flatness, such as side bending, while residual stress after processing determines poor microscopic flatness, such as slight deformation and low flatness, thus failing to meet processing accuracy requirements. Generally, the shape of alloy coil can be guaranteed by two processes: coil stress-relief annealing and online tension bending and straightening, usually reaching within 10I. However, this is far from sufficient for the high surface flatness requirements of alloy strip. Under the premise of conventional shape control, this invention adds a first leveling treatment and a second leveling treatment to jointly improve the surface flatness of alloy strip.

[0015] The first leveling treatment is a hot leveling method. By heating the material to a temperature below the recrystallization temperature, it achieves low-temperature stress relief without causing recrystallization, which would affect the material's structure and properties. At the same time, a certain compressive stress is applied, causing selective elongation of different parts of the material and promoting surface smoothness. Therefore, the control of annealing temperature, annealing time, and compressive stress in the first leveling treatment is very important. If the annealing temperature is too high or the annealing time is too long, the material is prone to recovery recrystallization, which leads to changes in the material's structure and properties, reduced hardness and strength, and softening of the material, making it difficult to meet the application requirements. If the annealing temperature is too low or the annealing time is too short, the recovery distortion energy brought by annealing is insufficient, which is not enough to eliminate internal stress, and the improvement in smoothness is not obvious.

[0016] Preferably, the process further includes: performing stress-relief annealing, stretching and straightening, and shearing treatments on the etched heat dissipation alloy strip in sequence, followed by the first leveling treatment.

[0017] Preferably, in the stress-relief annealing process, the first annealing temperature is 100℃-400℃.

[0018] Preferably, in the stress-relief annealing process, the first annealing time is 2h-5h.

[0019] Preferably, in the tensile straightening process, the unit tension is 10 N / mm. 2 -50N / mm 2 .

[0020] Preferably, in the stretching and straightening process, the speed is 10m / min-100m / min.

[0021] Preferably, the shearing process includes: longitudinal shearing and / or transverse shearing.

[0022] Preferably, in the longitudinal shearing process, the width is 50mm-500mm.

[0023] Preferably, in the cross-cutting process, the length is 50mm-500mm.

[0024] Preferably, in the first leveling process, the annealing temperature is 200℃-400℃.

[0025] Preferably, in the first leveling process, the ratio (F / t') of the compressive stress (F) applied to the etched heat dissipation alloy strip group to the stack thickness (t') of the etched heat dissipation strip group is not less than 0.5 kg / mm ​​and not more than 4.0 kg / mm.

[0026] A certain amount of compressive stress is beneficial for the selective elongation of different parts of the material and promotes surface flatness. However, when performing compressive stress annealing and straightening by stacking, the thickness of the stacked material has a certain impact on the elongation effect of the compressive stress. When the ratio (F / t') of the compressive stress (F) to the stack thickness (t') of the etched heat sink strip group is less than 0.5 kg / mm, the overall compressive stress does not reach the yield limit of the heat sink strip group, making it difficult to achieve the effect of elongation deformation, and the flatness improvement effect is not obvious. When the ratio (F / t') of the compressive stress (F) to the stack thickness (t') of the etched heat sink strip group is greater than 4.0 kg / mm, the overall compressive stress on the heat sink strip group is likely to exceed the yield limit, thereby producing a serious negative deformation effect and greatly affecting the flatness of the strip. Therefore, in this invention, the ratio (F / t') of the compressive stress (F) applied to the etched heat sink alloy strip group to the stack thickness (t') of the etched heat sink strip group is not less than 0.5 kg / mm ​​and not more than 4.0 kg / mm.

[0027] Preferably, in the first leveling process, the compressive stress is 50 kg to 200 kg.

[0028] Preferably, in the first leveling process, the holding time is 3h-4.5h.

[0029] Preferably, in the second leveling process, the leveling device includes at least 21 pairs of leveling rollers.

[0030] Preferably, in the second leveling process, the diameter of the leveling roller is not higher than 30 mm.

[0031] The second leveling process is cold leveling, which involves using several pairs of staggered leveling rollers to repeatedly bend the material up and down with a small radius of curvature, causing plastic deformation. At the same time, the elastic recovery effect restores the material surface to a flat state. Therefore, the leveling rollers in the cold leveling process have very high requirements. The number and diameter of the leveling rollers determine the effect of the up and down bending leveling. If the number of leveling rollers is too small, the material will bend up and down less many times, resulting in uneven plastic deformation and insignificant improvement in surface flatness. If the number of leveling rollers is too large, the leveling process becomes complicated to control, and the contact of multiple rollers is not conducive to the surface quality of the material and increases the risk of surface scratches.

[0032] In addition, if the diameter of the leveling roller is too large, the material is prone to excessive bending during the leveling process, which is not conducive to the surface flatness; if the diameter of the leveling roller is too small, the radius of curvature of the bending deformation is too small, and the leveling effect is not obvious. Therefore, the number and diameter of the leveling rollers are very important.

[0033] Preferably, in the second leveling process, the etched heat dissipation alloy strip passes through the leveling device 2-12 times.

[0034] The number of times the second leveling process is performed directly affects the surface flatness and uniformity of the leveled part, i.e., the processing index. Due to processing, sheet materials contain multiple sets of dimensional directions, such as parallel and perpendicular rolling directions, front and back directions of a plane, as well as the entry and exit sides of the leveling process. To achieve uniform surface flatness, the material needs to undergo multi-roller cyclic extension deformation in all directions. When the number of times the material passes through the leveling device is less than 2, it is difficult to guarantee the uniformity of at least one set of dimensional directions, which is not conducive to improving surface flatness. When the number of times the material passes through the leveling device is more than 12, the more leveling is performed, the more detrimental it is to the surface quality of the material, and the greater the risk of surface scratches. Therefore, in this invention, the number of times the etched heat dissipation alloy strip passes through the leveling device is 2-12.

[0035] Preferably, in the second leveling process, the gap between the leveling rollers through which the etched heat dissipation alloy strip passes each time is not lower than the gap between the corresponding leveling rollers through which the etched heat dissipation alloy strip passed the previous time.

[0036] Preferably, in the second leveling process, the ratio (l / t) of the gap (l) between the first pair of leveling rollers to the thickness (t) of the etched heat dissipation alloy strip is not less than -11.5 and not more than -5.5.

[0037] Preferably, in the second leveling process, the ratio (l / t) of the roll gap (l) between the last pair of leveling rolls to the thickness (t) of the etched heat dissipation alloy strip is not less than -4 and not more than -0.5.

[0038] The key point of the second leveling process is that the bending deformation of the leveled part must exceed its yield point to achieve a leveling effect. The gap between the staggered leveling rollers directly determines the magnitude of the leveling force on the leveled part. Therefore, the gap between the leveling rollers is the core factor determining the leveling effect. For the leveling of etched heat dissipation alloy strips, the gap between the rollers should increase with each pass to ensure that the bending moment gradually decreases, thereby improving the overall surface flatness. Generally, the gap between the first pair of leveling rollers should be large enough to ensure that the internal load on the material causes a specific part of the cross-section to begin full flow, resulting in a large-scale bending deformation. The gap between the last pair of leveling rollers should allow for localized flow. The movement of the rollers helps to compensate for deformation. At the same time, the thickness and shape of the material are directly related to the size of the roller gap. When the ratio (l / t) of the roller gap (l) between the first pair of leveling rollers to the thickness (t) of the etched heat dissipation alloy strip exceeds the range of -11.5 to -5.5, the leveling effect is not obvious when it is higher than -5.5. When it is lower than -11.5, the material surface exhibits negative deformation, which is not conducive to improving the flatness. When the ratio (l / t) of the roller gap (l) between the last pair of leveling rollers to the thickness (t) of the etched heat dissipation alloy strip exceeds the range of -4 to -0.5, the deformation cannot be compensated when it is higher than -0.5. When it is lower than -4, the flatness effect is lost at the exit.

[0039] Further, in the second leveling process, the etched heat dissipation alloy strip passes through the leveling device 6 times; when the etched heat dissipation alloy strip passes through the leveling device for the first two times, the ratio (l / t) of the roll gap (l) between the first pair of leveling rollers to the thickness (t) of the etched heat dissipation alloy strip is not less than -11.5 and not more than -9.5, and the ratio (l / t) of the roll gap (l) between the last pair of leveling rollers to the thickness (t) of the etched heat dissipation alloy strip is not less than -4 and not more than -2.5; when the etched heat dissipation alloy strip passes through the leveling device for the middle two times, the ratio (l / t) of the roll gap (l) between the first pair of leveling rollers to the thickness (t) of the etched heat dissipation alloy strip is not less than -4 and not more than -2.5. The ratio (l / t) of the thickness (t) of the gold strip is not less than -9.5 and not more than -7.5, and the ratio (l / t) of the roll gap (l) between the last pair of leveling rollers to the thickness (t) of the etched heat dissipation alloy strip is not less than -2.5 and not more than -1.0; when the etched heat dissipation alloy strip passes through the leveling device for the last two times, the ratio (l / t) of the roll gap (l) between the first pair of leveling rollers to the thickness (t) of the etched heat dissipation alloy strip is not less than -7.0 and not more than -5.5, and the ratio (l / t) of the roll gap (l) between the last pair of leveling rollers to the thickness (t) of the etched heat dissipation alloy strip is not less than -2.0 and not more than -0.5.

[0040] Preferably, a plurality of the leveling rollers of the leveling device define a first direction; in the second leveling process, the etched heat-dissipating alloy strip enters the leveling device in a direction parallel to the first direction; or / and, in the second leveling process, the etched heat-dissipating alloy strip enters the leveling device in a direction intersecting the first direction.

[0041] Preferably, each pair of leveling rollers in the leveling device includes: a first leveling roller located on the lower side and a second leveling roller located on the upper side; the etched heat dissipation alloy strip has a first surface and a second surface opposite to the first surface; in the second leveling process, the first surface and the second surface are alternately used as the surfaces close to the first leveling roller when the etched heat dissipation alloy strip enters the leveling device.

[0042] To ensure the flatness improvement effect and achieve good flatness stability, the material must enter the leveling device sequentially from different sets of dimensional directions. Simultaneously, the roller gap at the entry point from each set of dimensional directions must conform to the principle of gradually increasing roller gap, ensuring the uniformity and comprehensiveness of the cyclic bending deformation during multiple leveling processes. Therefore, this invention designs the material to enter the leveling device sequentially from multiple sets of dimensional directions.

[0043] A second aspect of the present invention is to provide an etched heat dissipation alloy strip, said etched heat dissipation alloy strip being prepared by the surface flatness improvement method as described above.

[0044] Preferably, the residual stress of the etched heat dissipation alloy strip is not higher than 35 MPa.

[0045] Preferably, the standard deviation of the residual stress of the etched heat dissipation alloy strip is not higher than 10 MPa.

[0046] Preferably, the flatness of the etched heat dissipation alloy strip is less than 0.1 mm.

[0047] Preferably, the process capability index of the etched heat dissipation alloy strip is higher than 1.33.

[0048] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0049] The surface flatness improvement method of the present invention, through a first leveling process and a second leveling process, can not only fully meet the flatness index requirements and stability requirements of etched heat dissipation alloy strips, but also does not require additional investment in high-cost equipment. Detailed Implementation

[0050] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0052] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0053] Example

[0054] This embodiment provides a method for improving the surface flatness of etched heat dissipation alloy strips, including:

[0055] The etched heat dissipation alloy strip is subjected to stress-relief annealing, tensile straightening, shearing, first leveling, second leveling, and surface cleaning in sequence; wherein,

[0056] The parameters of the stress-relief annealing process include: a first annealing temperature and a first annealing time;

[0057] The parameters of the stretching and straightening process include: unit tension and speed;

[0058] The shearing process includes: longitudinal shearing and transverse shearing;

[0059] The first leveling process includes: stacking several of the etched heat dissipation alloy strips into an etched heat dissipation alloy strip group, applying compressive stress to the etched heat dissipation alloy strip group at an annealing temperature, and holding it for a certain period of time to perform the first leveling process on the etched heat dissipation alloy strips.

[0060] The second leveling process includes: passing the etched heat dissipation alloy strip, which has undergone the first leveling process, through the leveling device several times at a certain speed to perform a second leveling process on the etched heat dissipation alloy strip.

[0061] The parameters of the second leveling process also include: the number of pairs of leveling rollers in the leveling device, the roller diameter of the leveling rollers, the ratio (l / t) of the roller gap (l) between the first pair of leveling rollers to the thickness (t) of the etched heat dissipation alloy strip, the ratio (l / t) of the roller gap (l) between the last pair of leveling rollers to the thickness (t) of the etched heat dissipation alloy strip, the direction in which the etched heat dissipation alloy strip enters the leveling device, and the surface of the etched heat dissipation alloy strip that is close to the first leveling roller when it enters the leveling device.

[0062] Those skilled in the art should understand that the stretching and straightening treatment and shearing treatment described in this application are conventional techniques in the field and do not require additional definition.

[0063] It should be noted that, in this application, stacking refers to placing one of the etched heat dissipation alloy strips on top of another etched heat dissipation alloy strip, and the overlap rate between two adjacent etched heat dissipation alloy strips is not less than 99.5%.

[0064] In a preferred embodiment, the leveling device in this application is a high-precision leveling device, but those skilled in the art should understand that the several pairs of leveling rollers in this application can not be provided solely by the high-precision leveling device.

[0065] It should be noted that the high-precision leveling device includes several pairs of staggered leveling rollers. When the metal strip is transported between these pairs of leveling rollers, it is bent repeatedly with decreasing deformation to remove internal stress and thus achieve good surface flatness. When both pairs of leveling rollers are tangent to the same horizontal line, the gap between them is zero. Thus, those skilled in the art should understand that when any one of the pair of leveling rollers has a horizontal tangent, if the other leveling roller intersects this horizontal tangent, the gap between them is less than zero. For example, in the i-th second leveling process, the etched heat-dissipating alloy strip enters the leveling device in a direction parallel to the first direction, and the first surface of the etched heat-dissipating alloy strip is positioned close to the first leveling roller; in the (i+1)-th second leveling process, the etched heat-dissipating alloy strip enters the leveling device in a direction parallel to the first direction, and the second surface of the etched heat-dissipating alloy strip is positioned close to the first leveling roller; in the j-th second leveling process, the etched heat-dissipating alloy strip enters the leveling device in a direction perpendicular to the first direction, and the first surface of the etched heat-dissipating alloy strip is positioned close to the first leveling roller; in the (j+1)-th second leveling process, the etched heat-dissipating alloy strip enters the leveling device in a direction perpendicular to the first direction, and the second surface of the etched heat-dissipating alloy strip is positioned close to the first leveling roller.

[0066] Examples 1-7

[0067] Examples 1-7 differ only in the parameters, as shown in the table below:

[0068] ;

[0069] ;

[0070] ;

[0071] ;

[0072] ;

[0073] The relationship in the table above refers to the relationship between the direction in which the etched heat dissipation alloy strip enters the leveling roller in each second leveling process and the direction defined by several pairs of leveling rollers; the surface refers to the surface of the etched heat dissipation alloy strip that is close to the first leveling roller when it enters the leveling device in each second leveling process. If the surface is an etched surface, it is recorded as positive; if the surface is a surface opposite to the etched surface, it is recorded as negative.

[0074] Comparative Example

[0075] This comparative example provides another method for improving the surface flatness of etched heat dissipation alloy strips, including:

[0076] The etched heat dissipation alloy strip is subjected to tension annealing, tensile straightening and shearing in sequence.

[0077] Comparative Examples 1-2

[0078] Comparative Examples 1 and 2 differ only in the parameters, as shown in the table below:

[0079] ;

[0080] Detection Examples

[0081] Examples 1-7 and Comparative Examples 1-2 were tested, and the test content and methods are as follows:

[0082] The residual stress of the etched heat dissipation alloy strip was tested according to the ASTM E1426-2014 Standard Test Method for Determining the X-Ray Elastic Constants for Use in the Measurement of Residual Stress using X-Ray Diffraction.

[0083] Take a 50mm×50mm sample from the etched heat dissipation alloy strip, and randomly select 20 points on the sample. Detect the residual stress according to the "ASTM E1426-2014 Standard Test Method for Determining the X-Ray Elastic Constants for Use in the Measurement of Residual Stress using X-Ray Diffraction", and calculate the standard deviation.

[0084] Randomly select a 4×4 grid on the etched heat dissipation alloy strip, test its flatness according to CN202310329999.3, and calculate the process capability index.

[0085] The test results are shown in the table below:

[0086] ;

[0087] As can be seen from the table above, the surface flatness improvement method of the present invention, through the first leveling treatment and the second leveling treatment, obtains an etched heat dissipation alloy strip with a residual stress not higher than 35 MPa, a standard deviation of residual stress not higher than 10 MPa, a flatness lower than 0.1 mm, and a process capability index higher than 1.33, which fully meets the index requirements and stability requirements of the flatness of the etched heat dissipation alloy strip.

[0088] In summary, the surface flatness improvement method of the present invention, through the first leveling process and the second leveling process, can not only fully meet the flatness index requirements and stability requirements of etched heat dissipation alloy strips, but also eliminates the need for additional high-cost equipment.

[0089] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A method for improving the surface flatness of an etched heat dissipation alloy strip, characterized in that, include: The etched heat dissipation alloy strip is subjected to a first leveling treatment and a second leveling treatment in sequence; wherein, The first leveling process includes: stacking several of the etched heat dissipation alloy strips into an etched heat dissipation alloy strip group, and applying a compressive stress of 20kg-500kg to the etched heat dissipation alloy strip group at an annealing temperature of 100℃-400℃, and maintaining it for 1h-5h, so as to perform the first leveling process on the etched heat dissipation alloy strips. The second leveling process includes: passing the etched heat dissipation alloy strip after the first leveling process through the leveling device several times at a speed of 5m / min-30m / min to perform a second leveling process on the etched heat dissipation alloy strip. The leveling device includes several pairs of leveling rollers.

2. The surface flatness improvement method according to claim 1, characterized by, Also includes: After the etched heat dissipation alloy strip is subjected to stress-relief annealing, tensile straightening and shearing in sequence, the first leveling process is performed.

3. The surface flatness improvement method according to claim 2, characterized by, In the aforementioned tension straightening process, the unit tension is 10 N / mm. 2 -50N / mm 2 The speed is 10m / min-100m / min.

4. The surface flatness improvement method according to claim 2, characterized by, The shearing process includes: longitudinal shearing and / or transverse shearing; in the longitudinal shearing, the width is 50mm-500mm; in the transverse shearing, the length is 50mm-500mm.

5. The surface flatness improvement method according to claim 1, characterized by, In the first leveling process, the ratio of the compressive stress applied to the etched heat dissipation alloy strip group to the stack thickness of the etched heat dissipation alloy strip group is not less than 0.5 kg / mm ​​and not more than 4.0 kg / mm.

6. The surface flatness improvement method according to claim 1, characterized by, In the second leveling process, the leveling device includes: at least 21 pairs of leveling rollers; the roller diameter of the leveling rollers is not higher than 30 mm; the etched heat dissipation alloy strip passes through the leveling device 2-12 times; the roller gap between the leveling rollers through which the etched heat dissipation alloy strip passes each time is not lower than the roller gap between the corresponding leveling rollers through which the etched heat dissipation alloy strip passed the previous time.

7. The surface smoothness improvement method according to claim 6, characterized in that, The ratio of the gap between the first pair of leveling rollers to the thickness of the etched heat dissipation alloy strip is not less than -11.5 and not more than -5.5; the ratio of the gap between the last pair of leveling rollers to the thickness of the etched heat dissipation alloy strip is not less than -4 and not more than -0.

5.

8. The surface flatness improvement method according to claim 1, characterized by, The leveling device defines a first direction for a plurality of pairs of leveling rollers; in the second leveling process, the etched heat-dissipating alloy strip enters the leveling device in a direction parallel to the first direction; or / and, in the second leveling process, the etched heat-dissipating alloy strip enters the leveling device in a direction intersecting the first direction.

9. The surface flatness improvement method according to claim 1, characterized by, Each pair of leveling rollers in the leveling device includes: a first leveling roller located on the lower side and a second leveling roller located on the upper side; the etched heat dissipation alloy strip has a first surface and a second surface opposite to the first surface; in the second leveling process, the first surface and the second surface are alternately used as the surfaces of the etched heat dissipation alloy strip that are close to the first leveling roller when it enters the leveling device.

10. An etching-type heat dissipation alloy strip, characterized by, The etched heat dissipation alloy strip is prepared by the surface flatness improvement method as described in any one of claims 1-9.