Invar sheet and surface control method thereof

Abstract

The application provides an inconel alloy plate and a surface control method thereof. The surface control method of the inconel alloy plate comprises the following steps: a thinning step, which comprises rolling the incoming material by at least two passes using a first work roll and rolling oil with a first kinematic viscosity, so as to obtain a thinned plate; in the rolling process, the rolling oil between the first work roll and the incoming material forms an oil film with a first thickness; a smoothing step, which comprises rolling the thinned plate by at least one pass using a second work roll and rolling oil with a second kinematic viscosity; in the rolling process, the rolling oil between the second work roll and the thinned plate forms an oil film with a second thickness; the oil film with the second thickness extrudes the surface of the thinned plate to form a plurality of oil pits, so as to obtain the inconel alloy plate. The oil pits obtained by extrusion of the oil film have a small planar area and a shallow depth, and the AOI defect detection rate in the subsequent precise metal mask manufacturing process can be reduced.

Description

Invar alloy sheet and its surface control method Technical Field

[0001] This invention relates to the field of alloy surface treatment technology, and more specifically, to an Invar alloy sheet and a method for controlling its surface. Background Technology

[0002] Invar alloys, also known as low-expansion alloys, are typically represented by Fe-Ni36 series alloys (iron-nickel based alloys, such as grade 4J36). The core characteristic of Invar alloys is their extremely low coefficient of thermal expansion (linear expansion coefficient typically ≤1.5×10⁻⁶) over a wide temperature range from room temperature to 300°C. -6 ( / ℃), while possessing excellent mechanical processing properties and dimensional stability, it is widely used in fields with extremely high requirements for dimensional accuracy and environmental adaptability, such as semiconductors, aerospace, and precision instruments, for example, precision metal masks in the semiconductor field.

[0003] Before manufacturing a precision metal mask, Invar alloy sheets need to be produced through processes such as melting and rolling. These sheets are then etched to obtain the precision metal mask. After obtaining the precision metal mask, its surface morphology needs to be inspected using Automatic Optical Inspection (AOI). Specifically, this involves acquiring grayscale values ​​of different areas on the mask's surface, calculating multiple grayscale differences, and determining whether a defect has formed based on the magnitude of these differences. For example, during rolling, oil pits are easily formed on the sheet surface. The deeper the oil pit, the darker the color during AOI inspection. Grayscale values ​​are then acquired from smooth surfaces and different oil pit locations, and the grayscale differences are calculated. Larger grayscale differences are more likely to be identified as defects by AOI. Longer oil pits result in more locations with grayscale differences, leading to more defects detected by AOI. An excessively high AOI defect rate can negatively impact product yield.

[0004] Generally, grinding rolls or texturing rolls are used in the rolling process of Invar alloy sheets. Texturing rolls require grinding with a grinding wheel and sandblasting to ensure the surface roughness of the rolls. After grinding with a grinding wheel, circumferential grinding marks are easily formed on the surface of the grinding roll. After rolling with grinding rolls, these grinding marks are transferred to the surface of the Invar alloy sheet, forming rolling marks along the rolling direction. These marks are generally deep and long, resulting in greater grayscale differences detected by AOI and making defects easier to detect. In the other type of rolling process using texturing rolls, the Rz (grayscale difference) is inherently large. When these marks are transferred to the strip surface, they result in large grayscale differences detected by AOI, making defects easier to detect. This leads to a higher number of defects detected by AOI and an overall decrease in product yield.

[0005] Furthermore, deeper and longer marks can reduce the etching accuracy in subsequent etching processes, further reducing product yield. Summary of the Invention

[0006] This application addresses the shortcomings of existing methods by proposing an Invar alloy sheet and its surface control method to solve the technical problems of long and deep marks formed on the surface of Invar alloy sheet after rolling, resulting in a large number of defects detected by AOI and a reduced product yield.

[0007] In one aspect, embodiments of this application provide a surface control method for Invar alloy sheets, comprising:

[0008] The thinning step includes: rolling the incoming material with a first work roll and rolling oil of a first kinematic viscosity for at least two passes to obtain a thinned sheet, wherein during the rolling process, the rolling oil between the first work roll and the incoming material forms an oil film of a first thickness; in the last pass, the surface roughness Ra of the first work roll is <0.2μm and the surface roughness Rz is <1μm.

[0009] The leveling step includes: using a second work roll in conjunction with rolling oil of a second kinematic viscosity to roll the thinned sheet at least once. During the rolling process, the rolling oil between the second work roll and the thinned sheet forms an oil film of a second thickness. The oil film of the second thickness squeezes the surface of the thinned sheet to form multiple oil pits, thereby obtaining an Invar alloy sheet. The surface roughness of the Invar alloy sheet satisfies 0.05μm < Ra < 0.15μm, and the depth of the oil pits is not greater than 0.2μm.

[0010] The second thickness is greater than the first thickness, the diameter of the second working roll is greater than the diameter of the first working roll, and the second kinematic viscosity is greater than the first kinematic viscosity.

[0011] In some embodiments, the rolling speed in the leveling step is lower than the rolling speed in the thinning step.

[0012] In some embodiments, the rolling speed in the leveling step is not less than 20 m / min and not more than 40 m / min.

[0013] In some embodiments, the surface roughness Ra of the second working roll is <0.05 μm.

[0014] In some embodiments, the diameter of the second working roll is not less than 60 mm and not more than 120 mm, and the contact deformation zone between the second working roll and the thinned sheet is greater than 5%.

[0015] In some embodiments, the first kinematic viscosity is no greater than 8 mm. 2 / s, second kinematic viscosity greater than 8 And less than 16 .

[0016] In some embodiments, the total deformation of the thinning step is not less than 50%.

[0017] In some embodiments, the tension during the leveling step is not less than 350. and not greater than 550 .

[0018] In some embodiments, the diameter of the first working roll is not less than 20 mm and not more than 40 mm.

[0019] Secondly, embodiments of this application provide an Invar alloy sheet, manufactured by any of the surface control methods provided in the first aspect above;

[0020] The surface of the Invar alloy sheet has multiple oil pits;

[0021] The surface roughness of the Invar alloy sheet must meet the requirements of 0.05μm < Ra < 0.15μm, and the depth of the oil pit must not exceed 0.2μm.

[0022] The beneficial effects of the technical solutions provided in this application include:

[0023] This application adjusts the surface roughness of the first work roll in the thinning step, making the thinned sheet material easier to roll in the leveling step. This allows for the extrusion of smaller, shallower oil pits based on the oil film during the leveling step, thereby improving the surface morphology of the Invar alloy sheet. Compared to the rolling marks transferred by the texturing roll in the prior art, the oil pits obtained by the oil film extrusion in this application have a smaller surface area and shallower depth. While meeting the surface roughness requirements of the Invar alloy sheet, this reduces the AOI defect detection rate in the subsequent precision metal mask manufacturing process, while also improving the etching accuracy and product yield. Furthermore, a certain number of oil pits can improve the adhesion of the photoresist during the subsequent manufacturing of the precision metal mask, thus ensuring the manufacturing reliability of the precision metal mask.

[0024] Specifically, (1) in the leveling step, two key measures were adopted to promote the formation of a thicker rolling oil film: a. The kinematic viscosity of the rolling oil in the leveling step is greater than that in the thinning step. By using rolling oil with higher kinematic viscosity in the leveling step, the fluidity of the rolling oil can be reduced, which can increase the possibility of the rolling oil remaining between the second work roll and the thinned plate; b. The diameter of the second work roll in the leveling step is greater than that of the first work roll in the thinning step. By increasing the diameter of the work roll in the leveling step, the area of ​​the contact deformation zone between the second work roll and the thinned plate during rolling can be increased, thereby expanding the area where the rolling oil exists between the second work roll and the thinned plate, and further increasing the possibility of forming a thicker oil film.

[0025] (2) In the leveling step, a thicker oil film can largely isolate the second work roll from the surface of the thinned plate, thereby minimizing the transfer of grinding marks from the surface of the second work roll to the surface of the Invar alloy plate, thus avoiding the formation of rolling marks along the rolling direction and avoiding the formation of long and deep oil pits. Moreover, since the area of ​​the contact deformation zone between the second work roll and the thinned plate is increased, a high-pressure environment is formed between the second work roll, the oil film, and the thinned plate. Under high pressure, the thicker oil film can squeeze the thinned plate, forming an indefinite number of oil pits. Compared with the rolling marks transferred by the texturing roll in the prior art, the oil pits obtained by the oil film extrusion in this embodiment have a smaller planar area and shallower depth, which can improve the morphology of the Invar alloy plate surface, so that the surface of the Invar alloy plate can meet a certain surface roughness and also improve the adhesion of the photoresist.

[0026] (3) Considering that if the surface roughness does not meet the rolling requirements, the Invar alloy sheet that meets the requirements for manufacturing precision metal mask cannot be obtained, this application uses a first working roll with a surface roughness Ra < 0.2 μm and Rz < 1 μm, so that the surface roughness of the thinned sheet is close to Ra < 0.2 μm and Rz < 1 μm. After rolling through the leveling step, the surface morphology of the Invar alloy sheet can be optimized so that its surface roughness meets the requirements of 0.05 μm < Ra < 0.15 μm and the depth of the oil pit is not greater than 0.2 μm.

[0027] Additional aspects and advantages of this application will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of this application. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 is a schematic flowchart of a surface control method for Invar alloy sheet provided in an embodiment of this application;

[0030] Figure 2 is a structural schematic diagram of the flattening step in a surface control method for Invar alloy sheet provided in an embodiment of this application;

[0031] Figure 3 is a schematic diagram of the surface of the Invar alloy sheet provided in the embodiment of this application.

[0032] Figure label:

[0033] 100 - Second working roll;

[0034] 200-Thinned sheet material. Detailed Implementation

[0035] The embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the embodiments described below with reference to the accompanying drawings are exemplary descriptions for explaining the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions of the embodiments of this application.

[0036] Those skilled in the art will understand that, unless specifically stated otherwise, the terms "described" and "the" as used herein may also include plural forms. It should be further understood that the term "comprising" as used in this application's specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude other features, information, data, steps, operations, elements, components, and / or combinations thereof supported by this art. It should be understood that when we say an element is "connected" to another element, the element may be directly connected to the other element, or it may mean that the element and the other element are connected through an intermediate element. The term "and / or" as used herein refers to at least one of the items defined by the term; for example, "A and / or B" can be implemented as "A," or as "B," or as "A and B."

[0037] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0038] This application provides a surface control method for Invar alloy plates. A flowchart of this method is shown in Figure 1. The method includes steps S1-S2:

[0039] S1: Thinning step, including: rolling the incoming material with a first working roll and rolling oil of a first kinematic viscosity for at least two passes to obtain a thinned plate 200, wherein the rolling oil between the first working roll and the incoming material forms an oil film of a first thickness during the rolling process; in the last pass, the surface roughness Ra of the first working roll is <0.2μm (micrometers) and the surface roughness Rz is <1μm.

[0040] S2: The leveling step includes: using a second work roll 100 in conjunction with rolling oil of a second kinematic viscosity to roll the thinned sheet 200 at least once. During the rolling process, the rolling oil between the second work roll 100 and the thinned sheet 200 forms an oil film of a second thickness. The oil film of the second thickness squeezes the surface of the thinned sheet 200 to form multiple oil pits, thereby obtaining an Invar alloy sheet. The surface roughness of the Invar alloy sheet satisfies 0.05μm < Ra < 0.15μm, and the depth of the oil pits is not greater than 0.2μm.

[0041] The second thickness is greater than the first thickness, the diameter of the second working roll 100 is greater than the diameter of the first working roll, and the second kinematic viscosity is greater than the first kinematic viscosity.

[0042] In this embodiment, by adjusting the surface roughness of the first work roll in the thinning step, the thinned sheet 200 obtained after the thinning step is more easily rolled using the leveling step. This allows for the extrusion of shallow, small-area oil pits based on the oil film between the second work roll 100 and the thinned sheet 200 during the leveling step, thereby improving the surface morphology of the Invar alloy sheet. Compared to the rolling marks based on texturing rolls in the prior art, the oil pits obtained by oil film extrusion in this embodiment have smaller areas and shallower depths. While meeting the surface roughness requirements of the Invar alloy sheet, this reduces the AOI defect detection rate in the subsequent precision metal mask manufacturing process and improves the etching accuracy and product yield of the precision metal mask. Furthermore, a certain number of oil pits can improve the adhesion of the photoresist during the subsequent manufacturing of the precision metal mask, thus ensuring the manufacturing reliability of the precision metal mask.

[0043] Specifically, (1) in the leveling step, two key measures were adopted to promote the formation of a thicker rolling oil film: a. The kinematic viscosity of the rolling oil in the leveling step is greater than that in the thinning step. By using rolling oil with higher kinematic viscosity in the leveling step, the fluidity of the rolling oil can be reduced, increasing the possibility of the rolling oil remaining between the second work roll 100 and the thinned plate 200; b. The diameter of the second work roll 100 in the leveling step is greater than that of the first work roll in the thinning step. By increasing the diameter of the work roll in the leveling step, the area of ​​the contact deformation zone between the second work roll 100 and the thinned plate 200 during rolling can be increased, thereby expanding the area where the rolling oil exists between the second work roll 100 and the thinned plate 200, further increasing the possibility of forming a thicker oil film. As shown in Figure 2, when the second work roll 100 rolls the thinned plate 200, part of the surface of the thinned plate 200 contacts the surface of the second work roll 100, forming a contact deformation zone.

[0044] (2) In the leveling step, the thicker oil film can largely isolate the surface of the second work roll 100 from the surface of the thinned plate 200, thereby minimizing the transfer of grinding marks from the surface of the second work roll 100 to the surface of the Invar alloy plate, thus avoiding the formation of rolling marks along the rolling direction and avoiding the formation of long and deep oil pits. Moreover, since the contact deformation area between the second work roll 100 and the thinned plate 200 is increased, a high-pressure environment is formed between the second work roll 100, the oil film, and the thinned plate 200. Under high pressure, the thicker oil film can squeeze the thinned plate 200, forming an indefinite number of oil pits.

[0045] As shown in Figure 3, the surface of the Invar alloy sheet after the oil pit is extruded is shown. Compared with the rolling marks transferred by the texturing roller in the prior art, the oil pit obtained by the oil film extrusion in this embodiment has a smaller plane area and shallower depth, which can improve the morphology of the Invar alloy sheet surface. This allows the surface of the Invar alloy sheet to meet a certain surface roughness while also improving the adhesion of the photoresist.

[0046] (3) Considering that if the surface roughness does not meet the rolling requirements, the Invar alloy sheet that meets the requirements for manufacturing precision metal photomasks cannot be obtained, this application uses a first work roll with a surface roughness Ra < 0.2 μm and Rz < 1 μm, so that the surface roughness of the thinned sheet 200 is close to Ra < 0.2 μm and Rz < 1 μm. After rolling in the leveling step, the surface morphology of the Invar alloy sheet can be optimized, so that the surface roughness meets the requirements of 0.05 μm < Ra < 0.15 μm and the depth of the oil pit is not greater than 0.2 μm. The use of a first work roll with a surface roughness Ra < 0.2 μm and Rz < 1 μm in this application can avoid the rolling flow lines in the thinning step being too deep, resulting in the presence of longitudinal rolling flow lines along the rolling direction after the leveling step.

[0047] Optionally, in the embodiments of this application, the planar area of ​​the oil pit obtained by oil film extrusion is relatively small, not exceeding 70. .

[0048] It should be noted that Ra and Rz values ​​are used to quantify the surface roughness. Ra is the arithmetic mean deviation value, and Rz is the ten-point height value of micro-irregularity. This is the same as in the existing technology and will not be elaborated here.

[0049] It should be noted that "surface morphology" and "surface roughness" of Invar alloy substrates are two related but distinct concepts. The quality of the surface morphology of an Invar alloy substrate is not equivalent to the quality of its surface roughness. Surface morphology is a macroscopic and comprehensive evaluation that describes the overall geometric characteristics of the surface. It includes not only the microscopic undulations measured by surface roughness but also more macroscopic texture features (such as the shape of pits). In contrast, surface roughness (such as Ra and Rz values) is merely a quantitative parameter of morphology at the microscopic scale; a product that meets the roughness standard may be judged as having a poor surface morphology due to its surface texture. Specifically, in this application, the purpose is not to manufacture the lowest possible surface roughness, but rather to control the uniformity of the Invar alloy substrate morphology, ensure reasonable pit size, and improve the adhesion of the photoresist while maintaining a certain level of surface roughness, thereby guaranteeing the manufacturing reliability of the precision metal mask.

[0050] It should be noted that the roller diameter is the diameter of the work roller.

[0051] Optionally, the incoming material in this application is an alloy sheet with a thickness of 0.1~0.3 mm. The total deformation in the thinning step is not less than 50%, that is, the thickness of the thinned sheet 200 is not greater than 0.15 mm. This is suitable for the rolling mechanism of the leveling step and can ensure that the desired Invar alloy sheet is obtained after the leveling step rolling.

[0052] In some embodiments, the rolling speed in the leveling step is lower than the rolling speed in the thinning step.

[0053] In this embodiment, compared to the thinning step, the rolling speed in the leveling step is reduced. The lower speed is beneficial for the rolling oil to enter between the second work roll 100 and the thinned plate 200. In addition, the lower speed can also improve the uniformity of the multiple oil pits extruded by the oil film. This can avoid the problem of uneven oil pit depth caused by uneven pressure distribution due to excessive rolling speed, which leads to uneven oil film thickness distribution. This can further improve the morphology of the Invar alloy plate.

[0054] In some embodiments, the rolling speed in the leveling step is not less than 20 m / min and not more than 40 m / min.

[0055] In this embodiment, the rolling speed in the thinning step is greater than 60 m / min, while the rolling speed in the leveling step is not less than 20 m / min and not greater than 40 m / min. Compared with the rolling speed in the thinning step, the rolling speed is reduced to between 20 m / min and 40 m / min. This rolling speed, together with the rolling oil of the second kinematic viscosity and the second work roll 100, increases the possibility of generating an oil film of the second thickness.

[0056] In some embodiments, the surface roughness Ra of the second working roller 100 is <0.05 μm.

[0057] In this embodiment, compared to the first working roll, the second working roll 100 has a lower surface roughness, meaning its surface is smoother and more conducive to forming uniform oil pits. Furthermore, the lower the surface roughness of the second working roll 100, the easier it is to form a "closed area" between the thinned sheet 200 and the second working roll 100, firmly locking the oil film between them and further ensuring the formation of an oil film of the second thickness.

[0058] In some embodiments, the thinning step further includes the following steps:

[0059] The first working roll is ground with a 400# (mesh) diamond grinding wheel.

[0060] The leveling process also includes the following steps:

[0061] The second working roller 100 is ground with an 800# diamond grinding wheel and polished with silk cloth.

[0062] In this embodiment, the first working roll and the second working roll 100 are ground with different types of grinding wheels, which can precisely control the surface state of the different working rolls so that the first working roll and the second working roll 100 have different surface roughness.

[0063] In some embodiments, the diameter of the second working roll 100 is not less than 60 mm and not more than 120 mm, and the contact deformation area between the second working roll 100 and the thinned sheet 200 is greater than 5%.

[0064] In this embodiment, with the thickness of the thinned sheet 200 not exceeding 0.15 mm, the diameter of the second work roll 100 is in the range of 60-120 mm. Larger diameter rolling requires greater rolling force, resulting in greater elastic flattening of the second work roll 100. The contact deformation zone between the second work roll 100 and the thinned sheet 200 exceeds 5%. When the contact deformation zone exceeds 5%, the friction mechanism between the thinned sheet 200 and the second work roll 100 changes from sliding to partial adhesion. The enormous frictional resistance in the adhesion zone strongly impedes metal flow. To force the deformation to continue, the unit pressure in the deformation zone increases sharply, thus forming a high-pressure zone. Within the high-pressure zone, the second-thickness oil film compresses the surface of the thinned sheet 200, forming multiple oil pits, resulting in an Invar alloy sheet.

[0065] In some embodiments, the first kinematic viscosity is no greater than 8. (mm² / s), second kinematic viscosity greater than 8 And less than 16 The second thickness is not less than 1μm.

[0066] In this embodiment, during the thinning step, the first kinematic viscosity of the rolling oil is no greater than 8. The rolling oil serves a cooling and lubricating function, without needing to form oil pits; it only needs to facilitate rolling. During the leveling step, the second kinematic viscosity of the rolling oil is relatively high. While serving a cooling and lubricating function, it also forms a second thickness of rolling oil between the second work roll 100 and the thinned plate 200. This rolling oil thickness is not less than 1 μm, exceeding the thickness of the rolling oil film during normal rolling. Under the high pressure of the contact deformation zone, this excess oil film forms small oil pits with a depth not exceeding 0.2 μm. This embodiment suppresses oil film escape along the rolling direction, thereby suppressing the formation of longer oil pits extending along the rolling direction.

[0067] In some embodiments, the tension during the leveling step is not less than 350. (N / mm²) and not greater than 550 .

[0068] In this embodiment, the tension during the leveling step is 350. ~550 In this process, while ensuring that the thinned sheet 200 has a suitable flatness, it also retains a certain degree of flexibility, allowing the thinned sheet 200 to have room for deformation, thus ensuring the effective implementation of the flattening step.

[0069] In some embodiments, the roll diameter of the first working roll is not less than 20 mm and not greater than 40 mm.

[0070] In this embodiment, the roll diameter of the first working roll is between 20 mm and 40 mm, and rolling can be carried out in multiple passes, ensuring that the total rolling deformation is greater than 50%, laying a foundation for the leveling step, ensuring the smooth progress of the leveling step, and also ensuring that the desired Invar alloy sheet can be obtained after the leveling step.

[0071] The present application also provides the following specific embodiments:

[0072] In the above step S1, the incoming material is rolled in at least two passes using the first working roll in combination with the rolling oil with the first kinematic viscosity, including the following steps:

[0073] For the incoming material with a thickness of 0.1 - 0.3 mm and an area of 0.15 500 mm², based on a four-column twenty-high rolling mill, in combination with the rolling oil with the first kinematic viscosity, at least 4 passes of rolling are carried out. In the last pass, a fine roll with 0.1 < Ra < 0.2 μm and 0.05 < Rz < 1 μm is used, the deformation per pass is greater than 20%, and the roll diameter of the working roll is 20 mm - 40 mm.

[0074] In the above step S2, the thinned sheet 200 is rolled in at least one pass using the second working roll 100 in combination with the rolling oil with the second kinematic viscosity, including the following steps:

[0075] For the thinned sheet 200 obtained in the thinning step, a four-high rolling mill is used, and at least one pass of rolling is carried out in combination with the rolling oil with the second kinematic viscosity.

[0076] Among them, the four-high rolling mill includes a pair of second working rolls 100 and backup rolls above and below the sheet. Each pair of second working rolls 100 and backup rolls are vertically aligned. The roll diameter of the backup roll is greater than that of the second working roll 100. The four-high rolling mill improves the flatness control accuracy through the small-diameter working roll and ensures the rolling stability through the large-diameter backup roll, and is specifically used to improve the surface quality, flatness and mechanical properties of the strip (such as eliminating the yield plateau and improving the surface finish).

[0077] In the embodiments of the present application, in combination with the thinning step and the leveling step, oil pits with a smaller planar area and a shallower depth can be obtained based on oil film extrusion, thereby improving the surface topography of the Invar alloy sheet.

[0078] The present application also provides specific data support for the surface control method. Please refer to the following table. The following table shows specific embodiments of a surface control method for Invar alloy sheets. Through experiments, oil pits with a smaller planar area and a shallower depth can be obtained, and the detection rate is significantly reduced in the subsequent AOI inspection.

[0079] Table 1. Specific embodiments of a surface control method for Invar alloy plates.

[0080]

[0081] Based on the same inventive concept, this application also provides an Invar alloy sheet, which is manufactured by any of the surface control methods provided in the foregoing embodiments.

[0082] The surface of the Invar alloy sheet has multiple oil pits.

[0083] The surface roughness of the Invar alloy sheet must meet the requirements of 0.05μm < Ra < 0.15μm, and the depth of the oil pit must not exceed 0.2μm.

[0084] In this embodiment, the surface control method is similar to that provided in the previous embodiments, and will not be repeated here. The Invar alloy sheet in this embodiment is obtained by rolling through an adjusted thinning step and a newly added leveling step. The oil pits have a small planar area and shallow depth. While meeting the surface roughness requirements of the Invar alloy sheet, this reduces the AOI defect detection rate in the subsequent precision metal mask manufacturing process, while also improving the etching accuracy and product yield of the precision metal mask. Furthermore, a certain number of oil pits can improve the adhesion of the photoresist during the subsequent manufacturing of the precision metal mask, thereby ensuring the manufacturing reliability of the precision metal mask.

[0085] By applying the embodiments of this application, at least the following beneficial effects can be achieved:

[0086] (1) In the leveling step, two key measures were adopted to promote the formation of a thicker rolling oil film: a. The kinematic viscosity of the rolling oil in the leveling step is greater than that in the thinning step. By using rolling oil with higher kinematic viscosity in the leveling step, the fluidity of the rolling oil can be reduced, which can increase the possibility of the rolling oil being held between the second work roll 100 and the thinned plate 200; b. The diameter of the second work roll 100 in the leveling step is greater than that of the first work roll in the thinning step. By increasing the diameter of the work roll in the leveling step, the area of ​​the contact deformation zone between the second work roll 100 and the thinned plate 200 during the rolling process can be increased, thereby expanding the area where the rolling oil exists between the second work roll 100 and the thinned plate 200, and further increasing the possibility of forming a thicker oil film.

[0087] (2) In the leveling step, the thicker oil film can largely isolate the second working roll 100 from the surface of the thinned plate 200, thereby minimizing the transfer of grinding marks from the surface of the second working roll 100 to the surface of the Invar alloy plate, thus avoiding the formation of rolling marks along the rolling direction and avoiding the formation of long and deep oil pits. Moreover, since the area of ​​the contact deformation zone between the second working roll 100 and the thinned plate 200 is increased, a high-pressure environment is formed between the second working roll 100, the oil film, and the thinned plate 200. Under high pressure, the thicker oil film can squeeze the thinned plate 200, forming an indefinite number of oil pits. Compared with the rolling marks transferred by the texturing roll in the prior art, the oil pits obtained by the oil film extrusion in this embodiment have a smaller planar area and shallower depth, which can improve the morphology of the Invar alloy plate surface, so that the surface of the Invar alloy plate can meet a certain surface roughness and also improve the adhesion of the photoresist.

[0088] (3) Considering that if the surface roughness does not meet the rolling requirements, the Invar alloy sheet that meets the requirements for manufacturing precision metal photomasks cannot be obtained, this application uses a first work roll with a surface roughness Ra < 0.2 μm and Rz < 1 μm, so that the surface roughness of the thinned sheet 200 is close to Ra < 0.2 μm and Rz < 1 μm. After rolling in the leveling step, the surface morphology of the Invar alloy sheet can be optimized, so that the surface roughness meets the requirements of 0.05 μm < Ra < 0.15 μm and the depth of the oil pit is not greater than 0.2 μm. The use of a first work roll with a surface roughness Ra < 0.2 μm and Rz < 1 μm in this application can avoid the rolling flow lines in the thinning step being too deep, resulting in the presence of longitudinal rolling flow lines along the rolling direction after the leveling step.

[0089] (4) Compared with the thinning step, reducing the rolling speed in the leveling step is beneficial for the rolling oil to enter between the second working roll 100 and the thinned plate 200. In addition, the low speed can also improve the uniformity of multiple oil pits extruded by the oil film, and can avoid the problem of uneven oil pit depth caused by uneven pressure distribution due to excessive rolling speed, which can further improve the morphology of Invar alloy plate.

[0090] (5) Compared with the first working roll, the second working roll 100 has a lower surface roughness, that is, the surface of the second working roll 100 is flatter, which is more conducive to forming uniform oil pits. In addition, the lower the surface roughness of the second working roll 100, the easier it is to form a "closed area" between the thinned plate 200 and the second working roll 100, and firmly lock the oil film between the thinned plate 200 and the second working roll 100, further ensuring the generation of the second thickness oil film.

[0091] (6) Based on the thickness of the thinned sheet 200 not exceeding 0.15 mm, the diameter of the second work roll 100 is in the range of 60~120 mm. Large roll diameter rolling requires large rolling force, and the elastic flattening of the second work roll 100 is large. The contact deformation zone between the second work roll 100 and the thinned sheet 200 is greater than 5%. When the contact deformation zone is greater than 5%, the friction mechanism between the thinned sheet 200 and the second work roll 100 will change from sliding to partial adhesion. The huge frictional resistance in the adhesion zone will strongly hinder the metal flow. In order to force the deformation to continue, the unit pressure in the deformation zone will increase sharply, thus forming a high-pressure zone. In the high-pressure zone, the second-thickness oil film squeezes the surface of the thinned sheet 200 to form multiple oil pits, resulting in Invar alloy sheet.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for surface control of Invar alloy sheet, characterized in that, include: The thinning step includes: rolling the incoming material at least two times using a first work roll and rolling oil of a first kinematic viscosity to obtain a thinned sheet. During the rolling process, the rolling oil between the first work roll and the incoming material forms an oil film of a first thickness. In the last pass, the surface roughness Ra of the first work roll is <0.2 μm, and the surface roughness Rz is <1 μm. The leveling step includes: rolling the thinned sheet at least once using a second work roll and rolling oil of a second kinematic viscosity. During the rolling process, the rolling oil between the second work roll and the thinned sheet forms an oil film of a second thickness. The oil film of the second thickness compresses the surface of the thinned sheet to form multiple oil pits, resulting in an Invar alloy sheet. The surface roughness of the Invar alloy sheet satisfies 0.05 μm < Ra < 0.15 μm, and the depth of the oil pits is not greater than 0.2 μm. The second thickness is greater than the first thickness, the roll diameter of the second work roll is greater than the roll diameter of the first work roll, and the second kinematic viscosity is greater than the first kinematic viscosity.

2. The surface control method according to claim 1, characterized in that, The rolling speed in the leveling step is less than the rolling speed in the thinning step.

3. The surface control method according to claim 2, characterized in that, The rolling speed in the leveling step shall be no less than 20 m / min and no more than 40 m / min.

4. The surface control method according to claim 1, characterized in that, The surface roughness Ra of the second working roller is less than 0.05 μm.

5. The surface control method according to claim 1, characterized in that, The diameter of the second working roll is not less than 60 mm and not more than 120 mm, and the contact deformation zone between the second working roll and the thinned sheet is greater than 5%.

6. The surface control method according to claim 1, characterized in that, The first kinematic viscosity is no greater than 8 The second kinematic viscosity is greater than 8 And less than 16 。 7. The surface control method according to claim 1, characterized in that, The total deformation in the thinning step shall not be less than 50%.

8. The surface control method according to claim 1, characterized in that, The tension during the leveling step shall not be less than 350. and not greater than 550 。 9. The surface control method according to claim 1, characterized in that, The diameter of the first working roll is not less than 20mm and not more than 40mm.

10. An Invar alloy sheet, characterized in that, The surface control method described in any one of claims 1-9 is used to manufacture the Invar alloy sheet; the surface of the Invar alloy sheet has multiple oil pits; the surface roughness of the Invar alloy sheet satisfies 0.05μm < Ra < 0.15μm, and the depth of the oil pits is not greater than 0.2μm.

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