Heat treatment method for electroformed Fe-Ni alloy foil and electroformed Fe-Ni alloy foil

Abstract

The present invention relates to a heat treatment method capable of reducing shape deformation such as curl together with a low coefficient of thermal expansion through thermo-mechanical heat treatment of an Fe-Ni alloy foil. The heat treatment method according to the present invention is characterized by applying pressure to the Fe-Ni alloy foil when annealing the Fe-Ni alloy foil produced by electroforming.

Description

Detailed Description of the Invention

[0001] 〔Technical Field〕 The present invention relates to a method for heat-treating an Fe-Ni alloy foil produced by electroforming plating, and more particularly, to a heat treatment method capable of reducing the occurrence of shape deformation such as curl and wrinkles during heat treatment with a low coefficient of thermal expansion through thermo-mechanical heat treatment, and an Fe-Ni alloy foil produced by the method.

[0002] 〔Background Art〕 A fine metal mask (hereinafter referred to as "FMM") used in the deposition process of an OLED display is manufactured through the melting, casting, rolling, and etching processes of an invar alloy having a very low coefficient of thermal expansion.

[0003] Currently, OLED displays applied to smartphones are at the QHD level (600 ppi), but in order to increase the resolution to the next-generation UHD level (1,000 ppi or more), the height of the hole wall of the FMM needs to be reduced to 10 μm or less so as not to interfere with the deposition of OLED materials.

[0004] However, since it is impossible to manufacture an invar thin plate with a thickness of 25 μm or less through the rolling process, until now, etching has been used after rolling to reduce the thickness to about 13 μm to cope with the high resolution of OLEDs. However, in the top-down method such as melting, casting, rolling, and etching, it is very difficult to manufacture an ultra-thin foil with a thickness of 10 μm or less due to reasons such as the presence of inclusions and the increase in production costs, and there is a problem that the manufacturing cost increases significantly.

[0005] Therefore, a method of manufacturing an Fe-Ni alloy foil or a fine metal mask using the electroforming method, which is a bottom-up method, has been considered.

[0006] In the case of Fe-Ni alloy foils and FMMs produced by electroforming plating, since they do not have a low value of 3 ppm / °C or less (preferably 2 ppm / °C or less), which is the coefficient of thermal expansion required for FMMs, a heat treatment process for reducing the coefficient of thermal expansion and improving mechanical properties is always necessary.

[0007] However, in reality, shape deformation (in the case of Fe-Ni alloy foils, the occurrence of curl or wrinkles; in the case of FMMs, pattern deformation) occurs at a considerable level during the heat treatment process, and thus they have not been used in the production of FMMs until now.

[0008] 〔Summary of the Invention〕 〔Problems to be Solved by the Invention〕 One object of the present invention is to provide a heat treatment method for Fe-Ni alloy foils that suppresses deformation occurring during the heat treatment of Fe-Ni alloy foils produced by electroforming plating and has a low coefficient of thermal expansion and good mechanical properties.

[0009] Another object of the present invention is to provide an electroformed Fe-Ni alloy foil having a low coefficient of thermal expansion and excellent mechanical properties.

[0010] 〔Means for Solving the Problems〕 One aspect of the present invention is to provide a heat treatment method for Fe-Ni alloy foils in which pressure is applied to the Fe-Ni alloy foils when annealing the Fe-Ni alloy foils produced by electroforming plating.

[0011] In the heat treatment method for Fe-Ni alloy foils, the annealing may be performed at a temperature of 180 to 600°C.

[0012] In the heat treatment method for Fe-Ni alloy foils, the annealing may be performed for 1 minute to 12 hours or less.

[0013] In the heat treatment method for Fe-Ni alloy foils, the pressure applied to the Fe-Ni alloy foils may be 0.1 KPa or more.

[0014] In the heat treatment method of the Fe-Ni alloy foil, a tensile force can be applied to the Fe-Ni alloy foil in at least one direction simultaneously with pressure.

[0015] In the heat treatment method of the Fe-Ni alloy foil, a tensile force is applied to the Fe-Ni alloy foil in two directions simultaneously with pressure, and the two directions may be directions perpendicular to each other.

[0016] In the heat treatment method of the Fe-Ni alloy foil, gas-quenching can be performed after the annealing step.

[0017] In the heat treatment method of the Fe-Ni alloy foil, the gas-quenching may be cooling in an inert gas atmosphere.

[0018] In the heat treatment method of the Fe-Ni alloy foil, the gas-quenching can be performed in a sealed space filled with an inert gas.

[0019] In the heat treatment method of the Fe-Ni alloy foil, the annealing of the Fe-Ni invar alloy foil can be performed by a continuous heat treatment process that is performed in the process of being continuously fed into and passing through a heating furnace.

[0020] In the heat treatment method of the Fe-Ni alloy foil, a tensile force may be applied to the Fe-Ni invar alloy foil on the advancing direction side during the continuous heat treatment process.

[0021] In the heat treatment method of the Fe-Ni alloy foil, the application of the pressure during the continuous heat treatment process may be performed in a state where the advancement of the Fe-Ni alloy foil is temporarily stopped.

[0022] In the heat treatment method of the Fe-Ni alloy foil, a tensile force may be applied to the Fe-Ni invar alloy foil in a direction perpendicular to the advancing direction during the continuous heat treatment steel process.

[0023] In the heat treatment method of the Fe-Ni alloy foil, tensile forces may be applied to both sides in the advancing direction of the Fe-Ni Invar alloy foil and in the direction perpendicular to the advancing direction during the continuous heat treatment step.

[0024] In the heat treatment method of the Fe-Ni alloy foil, the continuous heat treatment step may be continuously performed by being connected to the electroforming plating step of the Fe-Ni Invar alloy foil in a roll-to-roll manner.

[0025] Another aspect of the present invention is an Fe-Ni alloy foil manufactured by electroforming plating, wherein 90% or more of the total volume of the Fe-Ni alloy foil has a face-centered cubic (FCC) structure, and the Fe-Ni alloy foil having the maximum peak intensity at (111) during XRD analysis is provided.

[0026] In the Fe-Ni alloy foil, the average crystal grain size of the Fe-Ni alloy foil may be 100 nm or less, preferably 80 nm or less, and more preferably 50 nm or less.

[0027] In the Fe-Ni alloy foil, the tensile strength of the Fe-Ni alloy foil may be 0.7 to 1.5 GPa.

[0028] In the Fe-Ni alloy foil, the content of Ni may be 33 to 43 mass%.

[0029] In the Fe-Ni alloy foil, the thickness of the Fe-Ni alloy foil may be 15 μm or less, 14 μm or less, 13 μm or less, 12 μm or less, 11 μm or less, 10 μm or less, 9 μm or less, 8 μm or less, 7 μm or less, 6 μm or less, or 5 μm or less. The thickness is exemplary and the present invention should not be construed as excluding thicknesses exceeding 15 μm.

[0030] The Fe-Ni alloy foil may be used as a fine metal mask or an OLED encapsulant, but the uses are exemplary and should not be construed as being limited by these uses.

[0031] 〔Advantages of the Invention〕 According to the present invention, it is possible to reduce deformations such as curl and wrinkles generated during the heat treatment process of Fe-Ni alloy foil manufactured by electroforming.

[0032] Also, according to the present invention, it is possible to produce a current collector foil with a thickness of 10 μm or less from Fe-Ni alloy foil on a large area.

[0033] 〔Brief Description of the Drawings〕 FIG. 1 is a schematic view showing a thermo-mechanical heat treatment method according to an embodiment of the present invention.

[0034] FIG. 2 is a view showing the shapes of the sample of Example 1 (gas quenching) and the sample of Example 2 (furnace cooling).

[0035] FIG. 3 is a result of measuring the coefficient of thermal expansion in the 50 to 100 °C range of the sample of Example 1 (gas quenching) and the sample of Example 2 (furnace cooling).

[0036] FIG. 4 is a view showing the shapes of the sample of Example 3 before and after heat treatment.

[0037] FIG. 5 is a view showing the shapes of the sample of Example 4 before and after heat treatment.

[0038] FIG. 6 is a view showing the shapes of the sample of Example 5 before and after heat treatment.

[0039] FIG. 7 is a view showing the shapes of the sample of Example 6 before and after heat treatment.

[0040] FIG. 8 is a view showing the shapes of the sample of Comparative Example 1 before and after heat treatment.

[0041] FIG. 9 is a view showing the shapes of the sample of Comparative Example 2 before and after heat treatment.

[0042] FIG. 10 is a diagram showing the process of measuring the deformation rate through the length change of the sample of Example 7 and the sample of Example 8.

[0043] FIG. 11 is a diagram showing the measurement results of the deformation rate of the patterned sample before heat treatment, the sample of Example 7, and the sample of Example 8.

[0044] [Best Mode for Carrying Out the Invention] Hereinafter, the present invention will be described more specifically with reference to preferred embodiments. In the following description, descriptions of technologies widely known in the art and the like will be omitted. However, those skilled in the art can easily understand the characteristic configurations and their effects of the present invention through the following examples, and can implement the present invention without any particular difficulty.

[0045] The present inventors have found that when applying a thermo-mechanical method and a cooling method in which pressure is applied during the heat treatment of an Fe-Ni alloy foil formed by electroforming, deformation such as curl generated during the heat treatment process can be suppressed, the coefficient of thermal expansion can be reduced, and the mechanical properties can also be improved, leading to the present invention.

[0046] FIG. 1 is a schematic diagram for explaining the thermo-mechanical heat treatment method according to the present invention.

[0047] As shown in FIG. 1, on one side of a continuous heating furnace having a substantially rectangular parallelepiped shape, an inlet for supplying an Fe-Ni alloy foil manufactured by electroforming is formed, and on the other side, an outlet for discharging the Fe-Ni alloy foil heat-treated for a predetermined time is formed.

[0048] The Fe-Ni alloy foil introduced into the heating furnace can be pressurized using a pressing device during the heat treatment, or pressurization can be performed by placing a weight for a predetermined time.

[0049] The pressurization process is preferably performed in a stopped state where the Fe-Ni alloy foil introduced into the heating furnace does not move. However, for example, in the case of the method of placing a weight, pressurization can also be performed while it is moving.

[0050] Meanwhile, a tensile force may be applied from both sides in the advancing direction by rolls on both sides of the Fe-Ni alloy foil simultaneously with the pressing process. Also, a tensile force may be applied from both sides in the width direction of the Fe-Ni alloy foil perpendicular to the advancing direction. That is, a step of pressing by a press in a state where a predetermined tensile force is applied from the length and width directions of the Fe-Ni alloy foil may be performed.

[0051] The pressing force by the press or the weight is preferably applied at 0.1 KPa or more. However, when the pressing force is less than 0.1 KPa, it is difficult to suppress deformations such as curl and wrinkles generated during the heat treatment process.

[0052] Also, when manufacturing the Fe-Ni alloy foil in a continuous process such as a roll-to-roll process, if the applied pressing force is excessive, it may be difficult to execute in the continuous process, or damage to the Fe-Ni alloy foil may occur during the roll-to-roll process. Therefore, the pressing force may be 10 MPa or less, 5 MPa or less, 1 MPa or less, 100 KPa or less, 50 KPa or less, 10 KPa or less, 5 KPa or less, more preferably 4.5 KPa or less, and most preferably 4 KPa or less.

[0053] The pressing time by the press may be from 1 second to 1 hour. However, when the pressing time is less than 1 second, it is difficult to suppress the generation of curl, and when it exceeds 1 hour, the productivity may be excessively reduced. The preferable pressing time may be from 10 seconds to 30 minutes.

[0054] Also, the tensile force applied to the Fe-Ni alloy foil is preferably 500 MPa or less. This is because when it exceeds 500 MPa, damage such as tearing of the Fe-Ni alloy foil may occur during the tensile process.

[0055] The temperature of the heating furnace can be maintained within the range of 180 to 600 °C depending on the electroforming state. If the temperature of the heating furnace is maintained below 180 °C or above 600 °C, it is difficult to keep the thermal expansion coefficient of the heat-treated Fe-Ni alloy foil at 3 ppm / °C or less (preferably 2 ppm / °C or less, more preferably 1 ppm / °C or less).

[0056] Also, in order to reduce curl and wrinkle generation during the heating process, the heating temperature can be maintained within the range of 440 to 520 °C, and it is more preferable to maintain it within the range of 450 to 510 °C.

[0057] The time for which the Fe-Ni alloy foil is maintained in the heating furnace can be longer than the minimum time for phase transformation and 12 hours or less. If the heating time is less than the minimum time for phase transformation, it is difficult to lower the thermal expansion coefficient. If it exceeds 12 hours, the efficiency of the continuous process will decrease and excessive energy costs may occur, which is not preferable. For example, the heating time (maintenance time in the heat treatment furnace) may be 10 minutes to 12 hours.

[0058] The Fe-Ni alloy foil discharged from the heating furnace is preferably rapidly cooled through gas quenching. The gas quenching is a process of performing vacuum treatment to remove air after sealing a predetermined space, and then introducing a gas into the space and charging the heat-treated Fe-Ni alloy foil into the space for cooling. The gas used for gas quenching is preferably an inert gas such as argon, nitrogen, or a mixed gas thereof, but is not necessarily limited thereto.

[0059] The temperature of the gas during the gas quenching may be 50 °C or less, 40 °C or less, 30 °C or less, or 25 °C or less.

[0060] <Example 1> An Fe-36Ni alloy foil with a thickness of about 10 μm produced through an electroforming process was cut into a size of 50 mm in width and 60 mm in length.

[0061] The cut test pieces were heated at a heating rate of 10 °C / min and heated at 430 °C for 30 minutes. The heating was carried out in the atmosphere, but may be carried out in an inert gas atmosphere such as nitrogen or argon if necessary.

[0062] Also, during heating, a block (weight) of 2.5 kg was placed on the Fe-36Ni alloy foil, and pressure was applied for 30 minutes in such a manner (pressure: 8.17 KPa).

[0063] After the heat treatment, gas quenching was performed by putting the heated Fe-36Ni alloy foil into a sealed space filled with argon (about 25 °C) gas for cooling.

[0064] <Example 2> Heat treatment was performed in the same manner as in Example 1 using the same alloy foil, except that it was cooled in the furnace after the pressure heat treatment.

[0065] <Example 3> An Fe-33Ni alloy foil with a thickness of about 10 μm produced through an electroforming plating process was cut into a size of about 100 mm in width and about 120 mm in length.

[0066] The cut test pieces were heated at a heating rate of 10 °C / min and heated at 480 °C for 30 minutes. The heating atmosphere was a vacuum atmosphere (1×10-3 torr), but may be an air atmosphere or an inert gas atmosphere such as nitrogen, argon, or a mixed gas thereof depending on the case.

[0067] Also, during heating, a block (weight) of 2.5 kg was placed on the Fe-33Ni alloy foil, and pressure was applied for 30 minutes in such a manner (pressure: about 2.17 KPa). After the heat treatment, gas quenching was performed by putting the heated Fe-33Ni alloy foil into a sealed space filled with argon (about 25 °C) gas for cooling.

[0068] <Example 4> The alloy foil was heat-treated in the same manner as in Example 3, except that the heat treatment was performed at 500 °C.

[0069] <Example 5> The alloy foil was heat-treated in the same manner as in Example 3, except that it was heat-treated at 500 °C using an Fe-36Ni alloy foil.

[0070] <Example 6> The alloy foil was heat-treated in the same manner as in Example 3, except that it was heat-treated at 500 °C using an Fe-42Ni alloy foil.

[0071] <Comparative Example 1> The alloy foil was heat-treated in the same manner as in Example 5, except that it was heat-treated at 530 °C using an Fe-36Ni alloy foil.

[0072] <Comparative Example 2> The alloy foil was heat-treated in the same manner as in Example 6, except that it was heat-treated at 430 °C using an Fe-42Ni alloy foil.

[0073] <Example 7> In order to confirm the deformed state before and after heat treatment, an Fe-36Ni alloy foil with a thickness of about 10 μm produced through an electroforming plating process was patterned using a laser so that octagonal holes were regularly arranged.

[0074] The thus-patterned Fe-36Ni alloy foil was cut into a size of 30 mm in width and 71 mm in length.

[0075] The cut test piece was heated at a heating rate of 10 °C / min and heated at 450 °C for 1 hour. The heating was performed in the air, but may be performed in an inert gas atmosphere such as nitrogen or argon if necessary.

[0076] Also, during heating, a pressure of 2.5 kg was applied for 30 minutes by placing a block weighing 2.5 kg on the patterned Fe-36Ni alloy foil.

[0077] After the heat treatment, gas quenching was performed by putting the heated Fe-36Ni alloy foil into a sealed space filled with argon (about 25 °C) gas for cooling.

[0078] <Example 8> Heat treatment was carried out in the same manner as in Example 7, except that the alloy foil was cooled in the furnace without gas quenching after the heat treatment, i.e., furnace cooling was performed.

[0079] 〔Evaluation of curl or wrinkle generation of Fe-Ni alloy foil〕 Figure 2 is a diagram showing the shapes of the samples of Example 1 and Example 2. It was confirmed that the amount of curl generated was relatively small in the sample cooled by gas quenching after pressure-heat treatment like the sample of Example 1 compared to the sample of Example 2 cooled by furnace cooling. Through this, it was confirmed that in the case of an Fe-Ni alloy foil on which no pattern is formed, it is more preferable to perform gas quenching after pressure-heat treatment to reduce the deformation of the Fe-Ni alloy foil.

[0080] Figures 4 to 7 are diagrams showing the shapes of the samples of Example 3 to Example 6 before and after heat treatment, and Figures 8 and 9 are diagrams showing the shapes of the samples of Comparative Example 1 and Comparative Example 2 before and after heat treatment, respectively.

[0081] As confirmed from Figures 4 to 7, according to the heat treatment method according to Examples 3 to 6 of the present invention, almost no curl or wrinkle was observed after heat treatment even in the samples that initially had curl or wrinkle.

[0082] On the other hand, as confirmed from Figures 8 and 9, in the cases of Comparative Examples 1 and 2, curl and wrinkle occurred after heat treatment, which is judged to be the result of the heat treatment temperatures of the electroformed Fe-Ni alloy foils being 430 °C and 530 °C, respectively.

[0083] 〔Measurement of coefficient of thermal expansion of Fe-Ni alloy foil〕 Figure 3 shows the results of measuring the coefficients of thermal expansion of the samples of Example 1 and Example 2 in the temperature range of 50 to 100 °C.

[0084] As confirmed from FIG. 3, the coefficient of thermal expansion in the temperature range of 50 to 100°C was relatively lower for the sample cooled by gas quenching after pressure-heat treatment like the sample of Example 1 than for the sample of Example 2 cooled by furnace cooling.

[0085] Then, it can be seen that even when having the same alloy composition, the gas quenching method is advantageous for obtaining an Fe-Ni alloy foil having a lower coefficient of thermal expansion.

[0086] 〔Evaluation of Degree of Deformation of Pattern Shape〕 FIG. 10 is a diagram showing the measurement process of the deformation rate through the change in length of the sample of Example 7 and the sample of Example 8, and FIG. 11 is a diagram showing the measurement results of the deformation rate of the sample before heat treatment of the patterned Fe-Ni alloy foil, the sample of Example 7, and the sample of Example 8.

[0087] Taking one octagonal hole having a symmetric structure as shown in the left figure of FIG. 10 as a reference, a 16×16 pattern with 16 holes each in the horizontal and vertical directions of the sample is taken as one unit. As shown in the right figure, the length in the horizontal direction of the pattern (hereinafter, A1), the length in the vertical direction (hereinafter, A2), and the lengths in the diagonal directions (hereinafter, B1 and B2) are measured. After comparing and analyzing the non-heat-treated sample and the heat-treated samples (Example 7 and Example 8), the deformation rate is measured through the change in length and shown in FIG. 11.

[0088] For the samples of Example 7 and Example 8 that had undergone the heat treatment process, the four length deformation rates over A1 to B2 were relatively low at the level of 0.86 to 0.40. However, for the sample of Example 7 that was gas quenched, although the overall deformation amount was relatively lower than that of the sample of Example 8, the difference in the deformation amount within the sample was relatively large. That is, it shows that there are differences in the shape deformation characteristics depending on the cooling method.

[0089] As described above, the present invention has been described with reference to preferred embodiments, but it should be understood that the present invention is not limited by the above-described embodiments. That is, the present invention can be variously modified and corrected within the scope of the following claims, and all of these belong to the scope of the present invention. Therefore, the present invention is limited only by the claims and their equivalents.

Brief Description of the Drawings

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Claims

1. A heat treatment method for an Fe-Ni alloy foil, characterized by annealing the Fe-Ni alloy foil produced by electroforming plating under pressure.

2. The heat treatment method for an Fe-Ni alloy foil according to Claim 1, wherein the annealing is performed at a temperature of 180 to 600 °C in the range of 10 minutes to 12 hours.

3. The heat treatment method for an Fe-Ni alloy foil according to Claim 1, wherein the pressure is 0.1 kPa or more.

4. The heat treatment method for an Fe-Ni alloy foil according to Claim 1, wherein a tensile force is applied to the Fe-Ni alloy foil together with the pressure.

5. The heat treatment method for an Fe-Ni alloy foil according to Claim 4, wherein the tensile force is applied in two directions, and the two directions are perpendicular to each other.

6. The heat treatment method for an Fe-Ni alloy foil according to any one of Claims 1 to 5, wherein gas quenching is performed in an inert gas atmosphere after the annealing step.

7. The heat treatment method for an Fe-Ni alloy foil according to Claim 1, wherein the annealing is performed by a continuous heat treatment step performed in a process of continuously charging and passing the Fe-Ni alloy foil through a heating furnace.

8. The heat treatment method for an Fe-Ni alloy foil according to Claim 7, wherein applying the pressure during the continuous heat treatment step is performed in a state where the progress of the Fe-Ni alloy foil is temporarily stopped.

9. The heat treatment method for an Fe-Ni alloy foil according to Claim 7, wherein a tensile force is applied to the advancing direction side of the Fe-Ni alloy foil during the continuous heat treatment step.

10. An Fe-Ni alloy foil produced by electroforming plating, wherein the content of Ni contained in the Fe-Ni alloy is 33 to 43% by mass, and 90% or more of the total volume of the Fe-Ni alloy foil has a face-centered cubic (FCC) structure, and the peak intensity is maximum at (111) during XRD analysis.

11. The Fe-Ni alloy foil according to Claim 10, wherein the average grain size of the Fe-Ni alloy foil is 50 nm or less.

12. The Fe-Ni alloy foil according to Claim 10, wherein the thickness of the Fe-Ni alloy foil is 15 µm or less.

13. The Fe—Ni alloy foil according to claim 10, wherein the Fe—Ni alloy foil is for a fine metal mask or an OLED encapsulant.

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