Low-expansion invar alloy foil as well as preparation method and application thereof

Abstract

The invention discloses a low-expansion invar alloy foil and a preparation method and application thereof, and belongs to the technical field of electronic information materials.The preparation method comprises the following steps that periodic reversing square-wave pulse electro-deposition is conducted on an invar alloy plating solution, then heat treatment is conducted on the electro-deposited invar alloy foil, and the low-expansion invar alloy foil is obtained. And preparing to obtain the low-expansion invar alloy foil. Wherein the conditions in the periodic commutation square wave pulse electrodeposition process are as follows: the forward conduction working time is 50-500ms, the forward duty ratio is 30%-70%, the forward pulse frequency is 10-500Hz, and the forward current density is 30-80mA / cm < 2 >; the reverse conduction working time is 50-500 ms, the reverse duty ratio is 30%-70%, the reverse pulse frequency is 10-500 Hz, and the reverse current density is 5-20 mA / cm < 2 >. According to the method, the thickness of a cathode deposition diffusion layer is reduced through periodic reversing square wave pulse electrodeposition, and mass transfer of Fe < 2 + > is promoted, so that the iron content of the alloy foil is improved and stabilized, and the ultrathin invar alloy foil with uniform components is obtained. And the obtained alloy foil is subjected to heat treatment to regulate and control the crystal face orientation and the grain size, so that the linear thermal expansion coefficient is reduced, and the preparation of the low-expansion invar alloy foil is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic information material preparation, and in particular relates to a low-expansion Invar alloy foil and a preparation method and application thereof. Background Art

[0002] Organic light-emitting diodes (OLEDs) have attracted significant attention for their high brightness, high contrast, vibrant colors, and lightweight portability. They are widely used as key semiconductor devices to replace traditional liquid crystal displays (LCDs). Fine metal masks (FMMs) are a core component of OLED displays, significantly impacting their performance. Invar alloy foil, due to its very low coefficient of thermal expansion over a wide temperature range, is considered the optimal substrate for preparing fine metal masks (FMMs). While this material has significant market demand and economic benefits, it must meet stringent requirements, including near-zero inclusions, an extremely low coefficient of thermal expansion, and ultra-thinness.

[0003] Generally speaking, the thinner the Invar foil, the higher the resolution of the OLED display. Invar foil with an industrial thickness of more than 20μm is usually produced by a rolling process. Rolling Invar foil includes multiple processes such as smelting and forging, hot rolling or cold rolling, annealing and pickling. The process is complex, the equipment is large, there are many inclusions, and the high rolling pressure makes the thickness and width of the product dimensional accuracy and surface quality control technology very difficult and complicated. The thinner the alloy rolling thickness, the higher the rolling cost, and it is accompanied by problems such as weakened rigidity, difficult processing and increased defects. It is very difficult to obtain ultra-thin Invar foil through rolling. Therefore, it is difficult to obtain a resolution higher than quarter high definition (QHD) for rolled Invar foil.

[0004] Electrodeposition has the advantages of low cost, near zero inclusion, and precise control of composition and thickness, and is considered to be a very advantageous method for preparing near zero inclusion ultra-thin strips. 2+ The reduction of iron is not conducive to the improvement and stability of the iron content of Invar alloy foil. Summary of the Invention

[0005] In response to the above technical problems, the present invention proposes a low expansion Invar alloy foil and a preparation method and application thereof.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention:

[0008] A method for preparing a low expansion Invar alloy foil comprises the following steps:

[0009] Performing periodic reversing square wave pulse electrodeposition on an Invar alloy plating solution, and then heat treating the Invar alloy foil obtained by the electrodeposition to prepare the low expansion Invar alloy foil;

[0010] The conditions during the periodic commutation square wave pulse electrodeposition process are:

[0011] Forward conduction working time: 50-500ms, forward duty cycle: 30%-70%, forward pulse frequency: 10-500Hz, forward current density: 30-80mA / cm 2 Reverse conduction working time: 50-500ms, reverse duty cycle: 30%-70%, reverse pulse frequency: 10-500Hz, reverse current density: 5-20mA / cm 2 .

[0012] Beneficial effect: The present invention reduces the thickness of the cathode deposition diffusion layer through periodic commutation square wave pulse electrodeposition, promotes Fe 2+ The resulting alloy foil is then heat treated to control its crystal orientation and grain size, thereby reducing the linear thermal expansion coefficient and achieving the production of low-expansion Invar alloy foil.

[0013] Optionally, the Invar alloy plating solution includes the following components:

[0014] Soluble nickel salt, soluble iron salt, pH buffer, ion complexing agent, brightener, antioxidant, surfactant and deionized water.

[0015] Furthermore, the mass ratio of nickel salt to iron salt in the Invar alloy plating solution is (235-280): (60-100).

[0016] Furthermore, the soluble nickel salt includes nickel sulfate hexahydrate and nickel chloride hexahydrate; and / or,

[0017] The soluble iron salt is ferrous sulfate heptahydrate; and / or,

[0018] The pH buffer is boric acid; and / or

[0019] The ion complexing agent is sodium citrate; and / or,

[0020] The brightening agent is saccharin (o-benzoylsulfonyl imide); and / or,

[0021] The antioxidant is ascorbic acid; and / or,

[0022] The surfactant is sodium lauryl sulfate.

[0023] The plating solution of the present invention uses a sulfuric acid-chloride system as the primary nickel-iron salt system, which has high solubility and good conductivity. Boric acid improves the stability of the plating solution; sodium citrate promotes iron-nickel co-deposition; saccharin improves the surface brightness of the coating; ascorbic acid effectively prevents oxidation of the plating solution and the coating; and sodium dodecylsulfonate reduces surface defects in the alloy foil. Through the synergistic effect of these components, the plating solution of the present invention can achieve efficient, stable, and quality-controlled deposition of Invar alloy.

[0024] Furthermore, the invar alloy plating solution includes the following components in terms of mass concentration:

[0025] 10-20 g / L boric acid, 200-220 g / L nickel sulfate hexahydrate, 35-60 g / L nickel chloride hexahydrate; 30-50 g / L sodium citrate, 2-4 g / L saccharin, 0.2-0.5 g / L sodium dodecyl sulfate, 5-10 g / L ascorbic acid and 60-100 g / L ferrous sulfate heptahydrate.

[0026] Furthermore, the temperature of the Invar alloy plating solution is 50-70° C., and the pH value is 2-4.

[0027] Beneficial effects: The Invar alloy plating solution provided by the present invention is conducive to achieving a stable electrodeposition process, controlling the nickel-iron ratio of the product Invar alloy foil, and uniformity of the alloy foil composition by scientifically proportioning the components within the mass concentration range and precisely controlling the temperature range.

[0028] Optionally, the conditions during the heat treatment are:

[0029] In pure hydrogen atmosphere, pressure of 1×10 3 ~1×10 6 Pa, heat to 600-900°C at a heating rate of 5-7°C / min, keep at this temperature for 30-120 minutes, and cool to room temperature.

[0030] Beneficial effects: The heat treatment system of the present invention is beneficial to controlling grain growth and crystal plane orientation, reducing the thermal expansion coefficient of the Invar alloy foil, and thus obtaining a low-expansion Invar alloy foil.

[0031] The second technical solution of the present invention:

[0032] A low expansion Invar alloy foil is prepared by the above preparation method.

[0033] Optionally, the low expansion Invar alloy foil has an average iron content of 62-66% wt.%, and an average thermal expansion coefficient of less than 1×10 -6 / ℃, thickness is 15-20μm.

[0034] Beneficial Effects: By adjusting the pulse parameters, the present invention obtains an Invar alloy foil with a smooth surface, uniform composition, and easily controllable thickness. Furthermore, through a controlled atmosphere heat treatment process, the thermal expansion properties of the Invar alloy foil are optimized, resulting in an iron content (mass fraction) of 64±2%, a thickness of approximately 15-20 μm, and an average thermal expansion coefficient (in the temperature range of 25-150°C) of less than 1×10 -6 / ℃ low expansion Invar alloy foil.

[0035] That is, the Invar alloy foil prepared by the preparation process of the present invention with strong controllability, simple operation and low cost greatly improves the shortcomings of traditional electrodeposited Invar alloy foil such as uneven composition and high thermal expansion coefficient.

[0036] The third technical solution of the present invention:

[0037] The invention discloses an application of a low expansion Invar alloy foil in the preparation of electronic information materials and semiconductor devices.

[0038] Compared with the prior art, the present invention has the following advantages and technical effects:

[0039] During the electrodeposition process, the present invention adjusts the parameters of the periodic commutation square wave pulse, such as the forward and reverse conduction time, the forward and reverse duty cycle, and the forward and reverse frequency, to regulate the iron-nickel ratio and composition uniformity of the deposited alloy foil. The reverse current is beneficial for obtaining a smooth Invar alloy foil surface. Furthermore, a heat treatment process is performed to optimize the thermal expansion properties of the Invar alloy foil, ultimately obtaining an ultra-thin Invar alloy foil with near-zero expansion.

[0040] The present invention greatly improves the shortcomings of traditional electrodeposited Invar alloy foil, such as uneven composition and high thermal expansion coefficient. The Invar alloy foil obtained by the method of the present invention not only has uniform composition and easy-to-control thickness, but also can optimize the comprehensive performance of the Invar alloy foil. It is an important method for obtaining Invar alloy foil with near-zero thermal expansion. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0042] Figure 1 The process flow chart of preparing low expansion Invar alloy foil of the present invention is as follows;

[0043] Figure 2 This is a schematic diagram of the periodic commutation square wave pulse current waveform and parameters of the present invention;

[0044] Figure 3 The macromorphology (a), surface morphology (b), point scanning EDS (c), cross section (d), and element distribution map (e) of the low expansion Invar alloy foil finally obtained in Example 1 of the present invention are shown;

[0045] Figure 4 The macromorphology (a), surface morphology (b), point scanning EDS (c), cross section (d), and element distribution map (e) of the low expansion Invar alloy foil finally obtained in Example 2 of the present invention are shown;

[0046] Figure 5 The macromorphology (a), surface morphology (b), point scanning EDS (c), cross section (d), and element distribution map (e) of the low expansion Invar alloy foil finally obtained in Example 3 of the present invention are shown;

[0047] Figure 6 The macromorphology (a), surface morphology (b), point scanning EDS (c), cross section (d), and element distribution map (e) of the low expansion Invar alloy foil finally obtained in Example 4 of the present invention are shown;

[0048] Figure 7 The macromorphology (a), surface morphology (b), point scanning EDS (c), cross section (d), and element distribution map (e) of the low expansion Invar alloy foil finally obtained in Example 5 of the present invention are shown;

[0049] Figure 8 The macromorphology (a), surface morphology (b), point scanning EDS (c), cross section (d), and element distribution map (e) of the low expansion Invar alloy foil finally obtained in Example 6 of the present invention are shown;

[0050] Figure 9 Element distribution diagram of the cross section of the iron-nickel alloy foil prepared in Comparative Example 1;

[0051] Figure 10 The thermal expansion coefficient curves of the low expansion Invar alloy foils finally obtained in Examples 1 to 6 and the iron-nickel alloy foils prepared in Comparative Examples 1 and 2 in the temperature range of 25 to 150°C are shown. DETAILED DESCRIPTION

[0052] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0053] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0054] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0055] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0056] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0057] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing a low expansion Invar alloy foil, comprising the following steps:

[0058] Step 1: Prepare an Invar alloy plating solution: Dissolve a soluble metal salt, pH buffer, ion complexing agent, brightener, antioxidant, and surfactant in deionized water, thoroughly dissolve, and mix to obtain a plating solution. Allow the solution to stand for 24 hours and then filter.

[0059] Step 2, pulse electrodeposition: using a high-purity titanium plate as a cathode and a high-purity nickel plate or a high-purity iron plate as an anode, using the plating solution obtained in step 1, and adopting periodic commutation square wave pulse electrodeposition to obtain Invar alloy foil.

[0060] Step 3: Controlled atmosphere heat treatment: The Invar alloy foil obtained in step 2 is heat treated in a specific atmosphere and temperature to obtain a low expansion Invar alloy foil.

[0061] In some optional embodiments, the Invar electroplating solution in step (1) is prepared as follows:

[0062] Dissolve boric acid (pH buffer) in 50-70° C. deionized water, and then add nickel sulfate hexahydrate and nickel chloride hexahydrate (soluble metal nickel salts) to obtain a nickel salt aqueous solution;

[0063] Sodium citrate (ion complexing agent), saccharin (brightening agent), sodium lauryl sulfate (surfactant), and ascorbic acid (antioxidant) are sequentially dissolved in 50-70° C. deionized water to obtain an additive aqueous solution;

[0064] The nickel salt aqueous solution and the additive aqueous solution are mixed, and then ferrous sulfate heptahydrate (soluble metallic iron salt) is dissolved in the mixed solution, fully dissolved and mixed to obtain a plating solution. The plating solution is allowed to stand for 24 hours and then filtered for use.

[0065] In some optional embodiments, in the Invar plating solution in step (1), the boric acid concentration is 10-20 g / L, the nickel sulfate hexahydrate and nickel chloride hexahydrate concentrations are 200-220 g / L and 35-60 g / L, respectively; the sodium citrate concentration is 30-50 g / L, the saccharin concentration is 2-4 g / L, the sodium dodecyl sulfate concentration is 0.2-0.5 g / L, the ascorbic acid concentration is 5-10 g / L, and the ferrous sulfate heptahydrate concentration is 60-100 g / L. The plating solution temperature is 50-70° C., and the pH is 2-4.

[0066] In some optional embodiments, the cathode used in step (2) is a high-purity titanium plate, and the anode is a high-purity nickel or high-purity iron plate. A dual-pulse power supply is used to provide a periodic commutation square wave pulse current (current waveform and parameters are as follows Figure 2 (as shown), the forward pulse current and reverse pulse parameters are independently adjustable. When a forward square wave pulse is applied for electrodeposition, iron and nickel co-deposition occurs at the cathode. However, when a reverse square wave pulse is applied, the alloy foil deposited on the cathode undergoes anodic dissolution, with iron dissolving preferentially over nickel, thus replenishing the iron ions consumed in the solution during forward deposition. The forward pulse current parameters are as follows: forward conduction duration: 50-500ms; forward duty cycle: 30%-70%; forward pulse frequency: 10-500Hz; forward current density: 30-80mA / cm 2 The reverse pulse current parameters are as follows: reverse conduction working time: 50-500ms; reverse duty cycle: 30%-70%; reverse pulse frequency: 10-500Hz; reverse current density: 5-20mA / cm 2 .

[0067] In some optional embodiments, the specific gas in step (3) is pure hydrogen with a pressure of 1×10 3 ~1×10 6 Pa, heating rate is 5-7℃ / min, holding temperature is 600-900℃, holding time is 30-120 minutes, after the holding is completed, cool down to room temperature at a rate of 5-7℃ / min.

[0068] Unless otherwise specified, the "room temperature" in the present invention refers to 20-30°C.

[0069] The raw materials used in the present invention are all purchased from the market.

[0070] The technical solution of the present invention is further illustrated by the following examples.

[0071] Example 1

[0072] A method for preparing a low expansion Invar alloy foil comprises the following steps:

[0073] (1) dissolving boric acid (pH buffer) in 50° C. deionized water, and then adding nickel sulfate hexahydrate and nickel chloride hexahydrate (soluble metal nickel salts) to obtain a nickel salt aqueous solution;

[0074] Sodium citrate (ion complexing agent), saccharin (brightening agent), sodium dodecyl sulfate (surfactant), and ascorbic acid (antioxidant) are sequentially dissolved in 50° C. deionized water to obtain an additive aqueous solution;

[0075] The nickel salt aqueous solution and the additive aqueous solution are mixed evenly, and then ferrous sulfate heptahydrate (soluble metallic iron salt) is dissolved in the mixed solution, fully dissolved and mixed evenly to obtain a plating solution. The plating solution is allowed to stand for 24 hours and then filtered for use.

[0076] In the above-mentioned Invar alloy plating solution, the concentration of boric acid is 10 g / L, the concentration of nickel sulfate hexahydrate is 220 g / L, the concentration of nickel chloride hexahydrate is 35 g / L, the concentration of sodium citrate is 30 g / L, the concentration of saccharin is 2 g / L, the concentration of sodium dodecyl sulfate is 0.2 g / L, the concentration of ascorbic acid is 5 g / L, the concentration of ferrous sulfate heptahydrate is 60 g / L, and the pH of the plating solution is 2.5.

[0077] (2) Place the cathode high-purity titanium plate and the anode high-purity nickel plate in parallel and vertically in an electrolytic cell, use the plating solution obtained in step (1), and use a dual-pulse power supply to provide a periodic commutation square wave pulse current for electrodeposition. The forward pulse current parameters are as follows: forward conduction working time: 300ms; forward duty cycle: 60%; forward pulse frequency: 100Hz; forward current density: 30mA / cm 2 The reverse pulse current parameters are as follows: reverse conduction time: 300ms; reverse duty cycle: 50%; reverse pulse frequency: 100Hz; reverse current density: 5mA / cm 2 , the electrodeposition temperature is 50℃, the time is 50min, and Invar alloy foil is obtained on the cathode titanium substrate.

[0078] (3) The Invar alloy foil obtained in step (2) was placed in high-purity hydrogen at a pressure of 1×10 5 Pa, heating rate of 5℃ / min, holding temperature of 600℃, holding time of 120min, after the holding, cooling to room temperature at a rate of 5℃ / min to obtain low expansion Invar alloy foil.

[0079] Figure 3 The macromorphology (a), surface morphology (b), point scanning EDS (c), cross section (d) and element distribution map (e) of the Invar alloy foil obtained in this example. Figure 3 As can be seen from the figure, the surface of the Invar alloy foil is smooth and crack-free. The iron content of the alloy foil is 63.78wt.%, and the nickel content is 36.22wt.%. The thickness of the alloy foil is about 15μm, the cross section is dense, the composition is evenly distributed, and the average iron content is about 63.93wt.%. The thermal expansion properties of the Invar alloy foil are as follows: Figure 10 As shown in Table 1, the average thermal expansion coefficient of the final prepared Invar alloy foil in the temperature range of 25 to 150 ° C is 0.49×10 -6 / ℃.

[0080] Example 2

[0081] A method for preparing a low expansion Invar alloy foil comprises the following steps:

[0082] The difference between Example 2 and Example 1 lies in the pulse parameters: the forward pulse parameters are as follows: forward conduction working time: 500ms; forward duty cycle: 50%; forward pulse frequency: 10Hz; forward current density: 40mA / cm 2 The reverse pulse parameters are as follows: reverse conduction time: 200ms; reverse duty cycle: 50%; reverse pulse frequency: 10Hz; reverse current density: 10mA / cm 2 , the electrodeposition temperature is 50℃, and the electrodeposition time is 40min.

[0083] Figure 4 The macromorphology (a), surface morphology (b), point scanning EDS (c), cross section (d) and element distribution map (e) of the Invar alloy foil obtained in this example. Figure 4 As can be seen from the figure, the surface of the Invar alloy foil is smooth and crack-free. The iron content of the alloy foil is 63.21wt.%, and the nickel content is 36.79wt.%. The thickness of the alloy foil is about 15μm, the cross section is dense, the composition is evenly distributed, and the average iron content is about 63.79wt.%. The thermal expansion properties of the Invar alloy foil are as follows: Figure 10 As shown in Table 1, the average thermal expansion coefficient of the final prepared Invar alloy foil in the temperature range of 25 to 150 ° C is 0.46×10 -6 / ℃.

[0084] Example 3

[0085] A method for preparing a low expansion Invar alloy foil comprises the following steps:

[0086] (1) dissolving boric acid (pH buffer) in deionized water at 60° C., and then adding nickel sulfate hexahydrate and nickel chloride hexahydrate (soluble metal nickel salts) to obtain a nickel salt aqueous solution;

[0087] Sodium citrate (ion complexing agent), saccharin (brightening agent), sodium dodecyl sulfate (surfactant), and ascorbic acid (antioxidant) are sequentially dissolved in 60° C. deionized water to obtain an additive aqueous solution;

[0088] The nickel salt aqueous solution and the additive aqueous solution are mixed evenly, and then ferrous sulfate heptahydrate (soluble metallic iron salt) is dissolved in the mixed solution, fully dissolved and mixed evenly to obtain a plating solution. The plating solution is allowed to stand for 24 hours and then filtered for use.

[0089] In the above-mentioned Invar alloy plating solution, the concentration of boric acid is 15 g / L, the concentration of nickel sulfate hexahydrate is 200 g / L, the concentration of nickel chloride hexahydrate is 50 g / L, the concentration of sodium citrate is 35 g / L, the concentration of saccharin is 2 g / L, the concentration of sodium dodecyl sulfate is 0.2 g / L, the concentration of ascorbic acid is 5 g / L, the concentration of ferrous sulfate heptahydrate is 80 g / L, and the pH of the plating solution is 3.5.

[0090] (2) Place the cathode high-purity titanium plate and the anode high-purity iron plate in parallel and vertically in an electrolytic cell, use the plating solution obtained in step (1), and use a dual-pulse power supply to provide a periodic commutation square wave pulse current for electrodeposition. The forward pulse current parameters are as follows: forward conduction working time: 300ms; forward duty cycle: 40%; forward pulse frequency: 300Hz; forward current density: 50mA / cm 2 The reverse pulse current parameters are as follows: reverse conduction time: 200ms; reverse duty cycle: 50%; reverse pulse frequency: 100Hz; reverse current density: 10mA / cm 2 , the electrodeposition temperature is 60℃, the electrodeposition time is 30min, and Invar alloy foil is obtained on the cathode titanium substrate.

[0091] (3) The Invar alloy foil obtained in step (2) was placed in high-purity hydrogen at a pressure of 1×10 3 Pa, heating rate of 7℃ / min, holding temperature of 750℃, holding time of 60min, and cooling to room temperature at a rate of 7℃ / min after the holding period.

[0092] Figure 5 The macromorphology (a), surface morphology (b), point scanning EDS (c), cross section (d) and element distribution map (e) of the Invar alloy foil obtained in this example. Figure 5 As can be seen from the figure, the surface of the Invar alloy foil is smooth and crack-free. The iron content of the alloy foil is 65.18wt.%, and the nickel content is 34.82wt.%. The thickness of the alloy foil is about 15μm, the cross section is dense, the composition is evenly distributed, and the average iron content is about 65.25wt.%. The thermal expansion properties of the Invar alloy foil are as follows: Figure 10As shown in Table 1, the average thermal expansion coefficient of the final prepared Invar alloy foil in the temperature range of 25 to 150 ° C is 0.51×10 -6 / ℃.

[0093] Example 4

[0094] A method for preparing a low expansion Invar alloy foil comprises the following steps:

[0095] The difference between Example 4 and Example 3 lies in the pulse parameters: in step (2), the forward pulse parameters are as follows: forward conduction working time: 400ms; forward duty cycle: 30%; forward pulse frequency: 300Hz; forward current density: 50mA / cm 2 The reverse pulse parameters are as follows: reverse conduction time: 100ms; reverse duty cycle: 70%; reverse pulse frequency: 500Hz; reverse current density: 10mA / cm 2 , the electrodeposition temperature is 60℃, and the electrodeposition time is 30min.

[0096] Figure 6 The macromorphology (a), surface morphology (b), point scanning EDS (c), cross section (d) and element distribution map (e) of the Invar alloy foil obtained in this example. Figure 6 As can be seen from the figure, the surface of the Invar alloy foil is smooth and crack-free. The iron content of the alloy foil is 65.22wt.%, and the nickel content is 34.78wt.%. The thickness of the alloy foil is about 15μm, the cross section is dense, the composition is evenly distributed, and the average iron content is about 65.61wt.%. The thermal expansion properties of the Invar alloy foil are as follows: Figure 10 As shown in Table 1, the average thermal expansion coefficient of the final prepared Invar alloy foil in the temperature range of 25 to 150 ° C is 0.58×10 -6 / ℃.

[0097] Example 5

[0098] A method for preparing a low expansion Invar alloy foil comprises the following steps:

[0099] (1) dissolving boric acid (pH buffer) in deionized water at 70° C., and then adding nickel sulfate hexahydrate and nickel chloride hexahydrate (soluble metal nickel salts) to obtain a nickel salt aqueous solution;

[0100] Sodium citrate (ion complexing agent), saccharin (brightening agent), sodium dodecyl sulfate (surfactant), and ascorbic acid (antioxidant) are sequentially dissolved in 70° C. deionized water to obtain an additive aqueous solution;

[0101] The nickel salt aqueous solution and the additive aqueous solution are mixed evenly, and then ferrous sulfate heptahydrate (soluble metallic iron salt) is dissolved in the mixed solution, fully dissolved and mixed evenly to obtain a plating solution. The plating solution is allowed to stand for 24 hours and then filtered for use.

[0102] In the above-mentioned Invar alloy plating solution, the concentration of boric acid is 20 g / L, the concentration of nickel sulfate hexahydrate is 200 g / L, the concentration of nickel chloride hexahydrate is 60 g / L, the concentration of sodium citrate is 40 g / L, the concentration of saccharin is 4 g / L, the concentration of sodium dodecyl sulfate is 0.5 g / L, the concentration of ascorbic acid is 10 g / L, the concentration of ferrous sulfate heptahydrate is 100 g / L, and the pH of the plating solution is 2.

[0103] (2) Place the cathode high-purity titanium plate and the anode high-purity nickel plate in parallel and vertically in an electrolytic cell, use the plating solution obtained in step (1), and use a dual-pulse power supply to provide a periodic commutation square wave pulse current for electrodeposition. The forward pulse current parameters are as follows: forward conduction working time: 400ms; forward duty cycle: 40%; forward pulse frequency: 100Hz; forward current density: 80mA / cm 2 The reverse pulse current parameters are as follows: reverse conduction time: 100ms; reverse duty cycle: 60%; reverse pulse frequency: 100Hz; reverse current density: 20mA / cm 2 , the electrodeposition temperature is 70℃, the electrodeposition time is 20min, and Invar alloy foil is obtained on the cathode titanium substrate.

[0104] (3) The Invar alloy foil obtained in step (2) was placed in high-purity hydrogen at a pressure of 1×10 6 The temperature was kept at 900°C for 30 min, and then cooled to room temperature at a rate of 5°C / min.

[0105] Figure 7 The macromorphology (a), surface morphology (b), point scanning EDS (c), cross section (d) and element distribution map (e) of the Invar alloy foil obtained in this example. Figure 7 The surface of the Invar alloy foil is smooth and crack-free. The iron content of the alloy foil is 64.20wt.%, and the nickel content is 35.80wt.%. The thickness of the alloy foil is about 15μm, the cross section is dense, the composition is evenly distributed, and the average iron content is about 64.18wt.%. The thermal expansion properties of the Invar alloy foil are as follows: Figure 10 As shown in Table 1, the average thermal expansion coefficient of the final prepared Invar alloy foil in the temperature range of 25 to 150 ° C is 0.60×10 -6 / ℃.

[0106] Example 6

[0107] A method for preparing a low expansion Invar alloy foil comprises the following steps:

[0108] The difference between Example 6 and Example 5 lies in the pulse parameters: in step (2), the forward pulse parameters are as follows: forward conduction working time: 200ms; forward duty cycle: 70%; forward pulse frequency: 500Hz; forward current density: 70mA / cm 2 The reverse pulse parameters are as follows: reverse conduction time: 50ms; reverse duty cycle: 30%; reverse pulse frequency: 200Hz; reverse current density: 10mA / cm 2 , the electrodeposition temperature is 70℃, and the electrodeposition time is 40min.

[0109] Figure 8 The macromorphology (a), surface morphology (b), point scanning EDS (c), cross section (d) and element distribution map (e) of the Invar alloy foil obtained in this example. Figure 8 The surface of the Invar alloy foil is smooth and crack-free. The iron content of the alloy foil is 63.60wt.%, and the nickel content is 36.40wt.%. The thickness of the alloy foil is about 16μm, the cross section is dense, the composition is evenly distributed, and the average iron content is about 63.55wt.%. The thermal expansion properties of the Invar alloy foil are as follows: Figure 10 As shown in Table 1, the average thermal expansion coefficient of the final prepared Invar alloy foil in the temperature range of 25 to 150 ° C is 0.71×10 -6 / ℃.

[0110] Comparative Example 1

[0111] The only difference between Comparative Example 1 and Example 1 is that the electrodeposition process in step (2) adopts direct current with a current density of 30 mA / cm 2 , the other conditions are the same.

[0112] Figure 9 The element distribution diagram of the cross section of the iron-nickel alloy foil obtained in comparative example 1 is shown. The iron content of the cross section of the iron-nickel alloy foil varies greatly, and the composition distribution is uneven. The average iron content of the iron-nickel alloy foil is only about 55.23 wt.%, which is far below the range of Invar alloy foil (Fe: 62-66% wt.%). The thermal expansion properties of the iron-nickel alloy foil are shown in Figure 1. Figure 10 As shown in Table 1, the average thermal expansion coefficient of the iron-nickel alloy foil prepared in this comparative example in the temperature range of 25-150°C is 4.11×10 -6 / ℃, much higher than Examples 1-6.

[0113] Comparative Example 2

[0114] The only difference between Comparative Example 2 and Example 3 is that the heat treatment step (3) was not performed.

[0115] like Figure 10As shown in Table 1, the average thermal expansion coefficient of the Invar alloy foil prepared in this comparative example in the temperature range of 25-150°C is 8.56×10 -6 / ℃, much higher than Examples 1-6.

[0116] From the analysis results of the embodiments and comparative examples, it can be seen that the iron-nickel alloy foil prepared by periodic commutation square wave pulse current and heat treatment can reach the composition of Invar alloy, and the thermal expansion coefficient is less than 1×10 -6 / °C. Using direct current electrodeposition, the iron content of the iron-nickel alloy foil cannot reach the range of Invar foil. Using periodically commutated square-wave pulse current without heat treatment, the thermal expansion coefficient of the iron-nickel alloy foil cannot meet the requirements of low-expansion Invar foil. This shows that the synergistic effect of periodically commutated square-wave pulse current and heat treatment greatly improves the thermal expansion properties of the iron-nickel alloy.

[0117] Table 1 shows the average iron content and average thermal expansion coefficient of the iron-nickel alloy foils prepared in Examples 1-6 and Comparative Examples 1-2.

[0118] Table 1

[0119]

[0120] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a low expansion Invar alloy foil, characterized in that: The following steps are involved: Performing periodic reversing square wave pulse electrodeposition on an Invar alloy plating solution, and then heat treating the Invar alloy foil obtained by the electrodeposition to prepare the low expansion Invar alloy foil; The conditions during the periodic commutation square wave pulse electrodeposition process are: Forward conduction working time: 50-500ms, forward duty cycle: 30%-70%, forward pulse frequency: 10-500Hz, forward current density: 30-80mA / cm 2 Reverse conduction working time: 50-500ms, reverse duty cycle: 30%-70%, reverse pulse frequency: 10-500Hz, reverse current density: 5-20mA / cm 2 .

2. The method for preparing a low expansion Invar alloy foil according to claim 1, characterized in that: The invar alloy plating solution comprises the following components: Soluble nickel salt, soluble iron salt, pH buffer, ion complexing agent, brightener, antioxidant, surfactant and water.

3. The method for preparing a low expansion Invar alloy foil according to claim 2, characterized in that: The mass ratio of the soluble nickel salt to the soluble iron salt in the Invar alloy plating solution is (235-280): (60-100).

4. The method for preparing a low expansion Invar alloy foil according to claim 3, characterized in that: The soluble nickel salts include nickel sulfate hexahydrate and nickel chloride hexahydrate; and / or, The soluble iron salt is ferrous sulfate heptahydrate; and / or, The pH buffer is boric acid; and / or The ion complexing agent is sodium citrate; and / or, The brightening agent is saccharin; and / or, The antioxidant is ascorbic acid; and / or, The surfactant is sodium lauryl sulfate.

5. The method for preparing a low expansion Invar alloy foil according to claim 4, characterized in that: According to mass concentration, the invar alloy plating solution includes the following components: 10-20 g / L boric acid, 200-220 g / L nickel sulfate hexahydrate, 35-60 g / L nickel chloride hexahydrate; 30-50 g / L sodium citrate, 2-4 g / L saccharin, 0.2-0.5 g / L sodium dodecyl sulfate, 5-10 g / L ascorbic acid and 60-100 g / L ferrous sulfate heptahydrate.

6. The method for preparing a low expansion Invar alloy foil according to claim 1, characterized in that: The temperature of the Invar alloy plating solution is 50-70° C., and the pH value is 2-4.

7. The method for preparing a low expansion Invar alloy foil according to claim 1, characterized in that: The conditions during the heat treatment are: In pure hydrogen atmosphere, pressure of 1×10 3 ~1×10 6 Under Pa conditions, the temperature is increased to 600-900°C at a heating rate of 5-7°C / min and kept at this temperature for 30-120 minutes.

8. A low expansion Invar alloy foil, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 7.

9. The low expansion Invar alloy foil according to claim 8, characterized in that: The low expansion Invar alloy foil has an average iron content of 62-66% by weight, and an average thermal expansion coefficient of less than 1×10 -6 / ℃, thickness is 15-20μm.

10. Use of the low expansion Invar alloy foil according to claim 8 or 9 in electronic information materials and semiconductor devices.

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