Metal foil for spring member, manufacturing method of metal foil for spring member, and manufacturing method of spring member

Abstract

The present invention provides a metal foil for a spring member that can suppress dimensional variations in a spring member formed by wet etching of a metal foil, a method for manufacturing the metal foil for a spring member, and a method for manufacturing the spring member. [Solution] The thickness of the metal foil is 100 μm or more and 200 μm or less. The differential elongation rate in a central region RC in the width direction DW of the metal foil is larger than the differential elongation rates in a first end region RE1 and a second end region RE2 in the width direction DW. The differential elongation rate decreases from the central region RC toward the first end region RE1, and also decreases from the central region RC toward the second end region RE2. The maximum differential elongation rate in the central region RC is 30×10 -5 The maximum value of the differential elongation rate in each of the first end region RE1 and the second end region RE2 is 10×10 -5 The following is the result.

Description

[Technical Field]

[0001] The present disclosure relates to a metal foil for a spring member, a method for manufacturing the metal foil for a spring member, and a method for manufacturing a spring member. [Background technology]

[0002] Camera modules installed in electronic devices with cameras, such as tablet terminals and smartphones, are equipped with drive mechanisms that enable autofocus and zoom. Known drive mechanisms include a lens drive system and a sensor drive system. A lens drive system drive mechanism is equipped with a spring member that enables the position of the lens in the direction of the lens's optical axis. In contrast, a sensor drive system drive mechanism is equipped with a spring member that enables the position of the image sensor in the direction of the lens's optical axis (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-059345 [Patent Document 2] Japanese Patent Publication No. 2020-170170 Summary of the Invention [Problem to be solved by the invention]

[0004] The leaf springs included in the spring members are required to satisfy a specific spring load or deflection within a limited volume. To satisfy the requirements for the spring load and deflection, the spring members must be made of a metal with high hardness. Furthermore, to satisfy the requirements for the spring load and deflection, the spring members must also have a predetermined thickness or greater. Therefore, the metal foil for the spring members is also required to have a predetermined thickness or greater.

[0005] On the other hand, metal foils for spring members are manufactured by rolling a base material. As described above, metal foils for spring members are required to have a predetermined thickness. Therefore, when manufacturing the metal foil, it is difficult to perform rolling a sufficient number of times to eliminate uneven deformation of the base material due to rolling. This can result in, for example, different differential elongation rates of the metal foil at different positions in the width direction of the metal foil, resulting in the metal foil having a wavy shape with repeated irregularities in the length direction.

[0006] The first example of a corrugated shape is a central stretch, and the second example is an edge stretch. In a central stretch, the differential elongation rate at the center in the width direction of the metal foil is greater than the differential elongation rate at each end. As a result, the metal foil stretches in the width direction and has multiple peaks that are repeated along the length direction. On the other hand, in an edge stretch, the differential elongation rate at each end in the width direction of the metal foil is greater than the differential elongation rate at the center. As a result, the metal foil has multiple peaks that are repeated along the length direction at each end.

[0007] The corrugation of the metal foil causes different portions of the metal foil to be in contact with the etching solution during wet etching of the metal foil to produce a spring member. For example, when the corrugation of the metal foil is center-stretched, the etching solution flows faster along the peaks and valleys between the peaks toward the edges in the width direction. In contrast, when the corrugation of the metal foil is edge-stretched, fatigued etching solution tends to accumulate in the valleys between the peaks in the width direction of the metal foil, and the etching solution accumulated in the valleys is difficult to replace.

[0008] Such non-uniformity in the flow of the etching solution causes dimensional variations in the spring member manufactured by wet etching of the metal foil. The dimensional variations tend to increase as the metal foil is in contact with the etching solution for a longer period of time. Therefore, as described above, in spring members that are required to have a certain thickness or more, the dimensional variations caused by the corrugated shape of the metal foil tend to become significant. [Means for solving the problem]

[0009] A metal foil for a spring member that solves the above-mentioned problems is a band-shaped metal foil used to manufacture a spring member by wet etching. The thickness of the metal foil is 100 μm or more and 200 μm or less. The shapes along the length of the metal foil at each position in the width direction of the metal foil are different from each other, and each shape is a wave shape with unevenness that repeats in the length direction of the metal foil. The length in the length direction of the surface of the metal foil is a surface distance, and the minimum value of the surface distances at each position in the width direction of the metal foil is a minimum surface distance. The ratio of the difference between the surface distance at each position in the width direction of the metal foil and the minimum surface distance to the minimum surface distance is the differential elongation rate in the length direction. The differential elongation rate in a central region in the width direction of the metal foil is greater than the differential elongation rates in first end regions and second end regions in the width direction, and the differential elongation rate decreases from the central region toward the first end region and from the central region toward the second end region. The maximum value of the differential elongation rate in the central region is 30×10 -5 The maximum value of the differential elongation rate in each of the first end region and the second end region is 10×10 or less. -5 The following is the result.

[0010] A method for manufacturing a metal foil for a spring member that solves the above-mentioned problems is a method for manufacturing a metal foil for a spring member, which is a band-shaped metal foil used to manufacture a spring member by wet etching. The method for manufacturing a metal foil for a spring member includes rolling a base material to obtain the metal foil. The thickness of the metal foil is 100 μm or more and 200 μm or less. The shapes along the length direction of the metal foil at each position in the width direction of the metal foil are different from each other, and each shape is a wave shape with unevenness that repeats in the length direction of the metal foil. The length in the length direction on the surface of the metal foil is the surface distance, and the smallest value of the surface distances at each position in the width direction of the metal foil is the minimum surface distance. The ratio of the difference between the surface distance at each position in the width direction of the metal foil and the minimum surface distance to the minimum surface distance is the differential elongation rate in the length direction. A method for manufacturing a metal foil for a spring member includes the steps of: a) forming a metal foil having a central region in the width direction of the metal foil, the central region having a differential elongation rate greater than the differential elongation rates of first end regions and second end regions in the width direction; a differential elongation rate decreasing from the central region toward the first end region and decreasing from the central region toward the second end region; and a maximum differential elongation rate in the central region of the metal foil of 30×10 -5 the maximum value of the differential elongation rate in the first end region and the second end region is 10 × 10 -5 and rolling the base material as follows:

[0011] A method for manufacturing a spring member for solving the above problems includes forming a resist mask on a band-shaped metal foil and patterning the metal foil by wet etching using the resist mask. The thickness of the metal foil is 100 μm or more and 200 μm or less. Shapes along the length of the metal foil at each position in the width direction of the metal foil are different from each other, and each shape is a wave shape with unevenness that repeats in the length direction of the metal foil. The length in the length direction of the surface of the metal foil is a surface distance, and the minimum value of the surface distances at each position in the width direction of the metal foil is a minimum surface distance. The ratio of the difference between the surface distance at each position in the width direction of the metal foil and the minimum surface distance to the minimum surface distance is the differential elongation rate in the length direction. The differential elongation rate in a central region in the width direction of the metal foil is greater than the differential elongation rates in first end regions and second end regions in the width direction, and the differential elongation rate decreases from the central region toward the first end region and from the central region toward the second end region. The maximum value of the differential elongation rate in the central region is 30×10 -5 The maximum value of the differential elongation rate in the first end region and the second end region is 10×10 or less. -5 The following is the result.

[0012] According to the above-mentioned configurations, even if the metal foil for a spring member has a corrugated shape in which the differential elongation rate is large in the central region in the width direction, the flow of the etching solution supplied to the metal foil for a spring member is prevented from becoming uneven. As a result, even if a spring member is manufactured by wet etching a thick metal foil for a spring member having a thickness of 100 μm to 200 μm, the dimensional variation of the spring member within the plane of the metal foil is prevented.

[0013] In the above-mentioned metal foil for spring members, the central portion of the metal foil for spring members in the width direction may be the central portion of the central region in the width direction, and the length of the central region in the width direction may be 30% of the length of the metal foil in the width direction; the first end region may include a first end portion of the metal foil for spring members in the width direction, and the length of the first end region in the width direction may be 20% of the length of the metal foil in the width direction; and the second end region may include a second end portion of the metal foil for spring members in the width direction, and the length of the second end region in the width direction may be 20% of the length of the metal foil in the width direction.

[0014] The metal foil for a spring member described above prevents the gradient of the differential elongation rate between the central region and each end region from becoming large compared to when the central region is shorter and the end regions are longer, thereby further preventing the flow of etching solution supplied to the metal foil from becoming uneven.

[0015] In the metal foil for a spring member, the unit length in the width direction is 300 mm, and the average value of the elongation difference rate per unit length is 10 × 10 -5 It may be the following: According to the metal foil for a spring member, the differential elongation rate in the longitudinal direction is suppressed over the entire unit length, and therefore the flatness of the metal foil is improved.

[0016] In the metal foil for a spring member, the metal foil may contain any one selected from the group consisting of stainless steel alloy, beryllium copper, nickel-tin copper, phosphor bronze, Corson alloy, and titanium copper.

[0017] According to the above-mentioned metal foil for spring members, the metal foil for spring members has high hardness, which makes it easy for the degree of rolling to vary within the metal foil 10, so the effect of the upper limit value of the elongation difference rate in the central region and each end region is more pronounced. [Effects of the Invention]

[0018] According to the metal foil for a spring member, the method for manufacturing the metal foil for a spring member, and the method for manufacturing a spring member of the present disclosure, dimensional variation can be reduced in a spring member formed by wet etching of a metal foil. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a perspective view showing the structure of a metal foil for a spring member according to one embodiment of the metal foil for a spring member. [Figure 2] FIG. 2 is a plan view showing the metal foil for measurement. [Figure 3] FIG. 3 is a diagram showing a graph for explaining the differential elongation rate together with the cross-sectional structure of the metal foil for measurement. [Figure 4] FIG. 4 is a graph for explaining the differential elongation rate. [Figure 5] FIG. 5 is a plan view showing the structure of a spring member according to one embodiment of the spring member. [Figure 6] FIG. 6 is a process diagram showing one step in one embodiment of the method for producing metal foil for spring members. [Figure 7] FIG. 7 is a process diagram showing one step in one embodiment of the method for producing metal foil for spring members. [Figure 8] FIG. 8 is a process diagram showing one step in one embodiment of a method for manufacturing a spring member. [Figure 9] FIG. 9 is a process diagram showing one step in one embodiment of a method for manufacturing a spring member. [Figure 10] FIG. 10 is a process diagram showing one step in one embodiment of a method for manufacturing a spring member. [Figure 11] FIG. 11 is a process diagram showing one step in one embodiment of a method for manufacturing a spring member. [Figure 12] FIG. 12 is a process diagram showing one step in one embodiment of a method for manufacturing a spring member. [Figure 13] FIG. 13 is a plan view showing the structure of the metal foil used for measurement in each example and each comparative example, along with its dimensions. [Figure 14]FIG. 14 is a graph showing the distribution of the elongation difference in the width direction of the metal foil of Example 1. [Figure 15] FIG. 15 is a graph showing the distribution of the elongation difference in the width direction of the metal foil of Example 2. [Figure 16] FIG. 16 is a graph showing the distribution of the differential elongation rate in the width direction of the metal foil of Example 3. [Figure 17] FIG. 17 is a graph showing the distribution of the elongation difference in the width direction of the metal foil of Comparative Example 1. [Figure 18] FIG. 18 is a graph showing the distribution of the elongation difference in the width direction of the metal foil of Comparative Example 2. [Figure 19] FIG. 19 is a table showing the calculation results of the differential elongation rate for each metal foil at each position in the width direction. [Figure 20] FIG. 20 is a table showing the results of measuring the variation in width of spring members manufactured using each metal foil. DETAILED DESCRIPTION OF THE INVENTION

[0020] An embodiment of a metal foil for a spring member, a method for manufacturing the metal foil for a spring member, and a method for manufacturing a spring member will be described with reference to FIGS.

[0021] [Metal foil for spring components] The metal foil for a spring member will be described with reference to FIG. As shown in FIG. 1, a metal foil 10 for a spring member (hereinafter also referred to as metal foil 10) is used to manufacture a spring member by wet etching. The metal foil 10 is a rolled material formed from a metal having a high enough hardness to realize the spring load or deflection required for a spring member 20 (see FIG. 5). The metal foil 10 has a strip shape. The metal foil 10 has a shape that follows a two-dimensional plane defined by a length direction DL and a width direction DW. In the metal foil 10, the length in the length direction DL is significantly longer than the length in the width direction DW.

[0022] The metal foil 10 has a front surface 10F and a back surface 10R opposite to the front surface 10F. The thickness T of the metal foil 10 is the distance between the front surface 10F and the back surface 10R. The thickness of the metal foil 10 is within the range of 100 μm to 200 μm. The thickness T of the metal foil 10 has a uniformity such that the ratio of the difference between the maximum and minimum values ​​of the thickness T of the metal foil 10 to the average value of the thickness T of the metal foil 10 is 3% or less.

[0023] The metal foil 10 includes a plurality of peaks 10A and valleys 10B located between the peaks 10A. Each peak 10A extends along the width direction DW. The peaks 10A are arranged at intervals along the length direction DL. The peaks 10A and valleys 10B of the metal foil 10 are formed by the difference in the elongation rate of the metal foil 10 at each position in the width direction DW.

[0024] As described above, the metal foil 10 is formed from a metal having a high enough hardness to achieve the spring load or deflection required for the spring member 20 manufactured using the metal foil 10. The metal foil 10 may be formed from, for example, a stainless steel alloy or a copper alloy. The stainless steel alloy may be, for example, a stainless steel alloy specified in JIS G 4313:2011 "Stainless steel strip for springs." The copper alloy may be, for example, a copper alloy specified in JIS H 3130:2018 "Beryllium copper, titanium copper, phosphor bronze, nickel-tin copper, and nickel silver plate and strip for springs."

[0025] The metal foil 10 preferably contains any one selected from the group consisting of stainless steel alloy, beryllium copper, nickel-tin copper, phosphor bronze, Corson alloy, and titanium-copper, which gives the metal foil 10 high hardness, thereby enabling the durability of the spring member formed from the metal foil 10 to be increased.

[0026] The Vickers hardness of the metal foil 10 may be, for example, HV150 or more, HV200 or more, or HV250 or more. The Vickers hardness is a value measured by a method conforming to JIS Z 2244:2009 "Vickers hardness test - Test method." The tensile strength of the metal foil 10 is, for example, 600 N / mm 2 It may be 700N / mm or more. 2 It may be 800N / mm or more. 2 The tensile strength is a value measured by a method conforming to JIS Z 2241:2011 "Method of tensile testing for metallic materials."

[0027] [Expansion rate] The differential elongation rate will be described with reference to FIGS. When the metal foil 10 is placed on a horizontal surface, the position of the surface of the metal foil 10 relative to the horizontal surface, that is, the height, is the surface position.

[0028] As shown in FIG. 2, in measuring the surface position, the rolled metal foil 10 is first cut in a slitting process so that the dimension of the metal foil 10 in the width direction DW is a width W, thereby obtaining a strip-shaped metal foil 10. The obtained metal foil 10 is then wound into a roll. Next, a slitting process is performed in which the metal foil 10 is cut across the entire width direction DW, i.e., the entire width, thereby cutting out a measurement foil 10M as a portion of the metal foil 10 in the length direction DL. The width W of the measurement foil 10M in the width direction DW is equal to the dimension of the metal foil 10 in the width direction DW. Next, the surface position of the surface 10MS of the measurement foil 10M at each position in the length direction DL is measured at predetermined intervals in the width direction DW. The range in which the surface position is measured is the measurement range ZL.

[0029] The measurement range ZL excludes the non-measurement ranges ZE, which are both ends of the measurement foil 10M in the length direction DL. The measurement range ZL also excludes non-measurement ranges (not shown), which are both ends of the measurement foil 10M in the width direction DW. The slitting process for cutting the metal foil 10 may create new waveforms in the measurement foil 10M that are different from the waveforms of the metal foil 10. The length of each non-measurement range ZE in the length direction DL is the range in which such new waveforms may be created, and is excluded from the measurement of the surface position. The length of each non-measurement range ZE in the length direction DL is, for example, 100 mm. In order to exclude new waveforms created by the slitting process in the width direction as well, the length of the non-measurement range in the width direction DW is, for example, 10 mm from the end of the width direction DW.

[0030] Fig. 3 is a graph showing an example of the surface position at each position in the length direction DL of the measurement foil 10M. Fig. 3 is a diagram showing the cross-sectional structure of the measurement foil 10M at a cross section including the length direction DL, as well as the surface position of the measurement foil 10M. Fig. 3 shows an example of a portion having three waves in the length direction DL among each portion in the width direction DW.

[0031] As shown in Figure 3, the positions in the length direction DL where the height is measured are arranged at intervals that allow the waveform irregularities of the metal foil 10 to be copied. The positions in the length direction DL where the height is measured are arranged at equal intervals of, for example, 1 mm or more and 20 mm or less in the length direction DL. The length of the broken line LW connecting the heights of the positions in the length direction DL is calculated as the surface distance La. The differential elongation rate of the metal foil 10 in the length direction DL is determined by the following equation 1. That is, if the smallest value of the surface distances La at the positions in the width direction DW of the metal foil 10 is defined as the minimum surface distance Lm, the ratio of the difference between each surface distance La and the minimum surface distance Lm to the minimum surface distance Lm is the differential elongation rate. Elongation difference rate = (La - Lm) / Lm ... (Equation 1)

[0032] FIG. 4 shows an example of the differential elongation rate in the length direction DL at each position in the width direction DW of the metal foil 10. 4, the differential elongation rate of the metal foil 10 has a maximum value in the central region RC in the width direction DW, decreases from the central region RC toward the first end region RE1 in the width direction DW, and decreases from the central region RC toward the second end region RE2 in the width direction DW.

[0033] The central portion PC of the metal foil 10 in the width direction DW is the central portion of the central region RC in the width direction DW. The length of the central region RC in the width direction DW is 30% of the length of the metal foil 10 in the width direction DW. The first end region RE1 includes a first end E1 of the metal foil 10 in the width direction DW, and the length of the first end region RE1 in the width direction DW is 20% of the length of the metal foil 10 in the width direction DW. The second end region RE2 includes a second end E2 of the metal foil 10 in the width direction DW, and the length of the second end region RE2 in the width direction DW is 20% of the length of the metal foil 10 in the width direction DW.

[0034] The metal foil 10 includes, in the width direction DW, a first intermediate region RI1 located between the first end region RE1 and the central region RC, and a second intermediate region RI2 located between the second end region RE2 and the central region RC. The differential elongation rate in the first intermediate region RI1 decreases from the central region RC toward the first end region RE1. The differential elongation rate in the second intermediate region RI2 decreases from the central region RC toward the second end region RE2.

[0035] The metal foil 10 satisfies the following six conditions. (Condition 1) The thickness T of the metal foil 10 is 100 μm or more and 200 μm or less. (Condition 2) The differential elongation rate in the central region RC in the width direction DW of the metal foil 10 is greater than the differential elongation rates in the first end region RE1 and the second end region RE2 in the width direction DW. (Condition 3) The differential elongation rate decreases from the central region RC toward the first end region RE1. (Condition 4) The differential elongation rate decreases from the central region RC toward the second end region RE2. (Condition 5) The maximum value of the expansion differential rate in the central region RC is 30 × 10 -5 The following is the result.

[0036] (Condition 6) The maximum value of the differential elongation rate in each of the first end region RE1 and the second end region RE2 is 10×10 -5 The following is the result.

[0037] In a metal foil 10 that satisfies conditions 2, 3, and 4, the differential elongation rate due to rolling is greater in the central region RC than in the first end region RE1 and the second end region RE2. Therefore, the central region RC is convex relative to the end regions RE1 and RE2, i.e., forms peaks 10A, corresponding to the difference in differential elongation rate between the central region RC and the end regions RE1 and RE2. As a result, the etching solution supplied to the metal foil 10 during wet etching of the metal foil 10 flows from the central region RC toward the end regions RE1 and RE2 according to the difference in surface position between the central region RC and the end regions RE1 and RE2, and then flows from the end regions RE1 and RE2 to the outside of the metal foil 10. As a result, the etching solution is less likely to remain in the central region RC, and the etching solution flows more vigorously in the end regions RE1 and RE2 due to the difference in surface position.

[0038] This flow occurs not only in the peaks 10A caused by the difference in the elongation ratio, but also in the valleys 10B located between the peaks 10A. In the valleys 10B, the etching liquid flows from the peaks 10A to the valleys 10B in the longitudinal direction DL according to the difference in surface position between the peaks 10A and the valleys 10B, so a flow of the etching liquid similar to that in the peaks 10A occurs.

[0039] As a result, in the spring member 20 attached to each end region RE1, RE2 of the metal foil 10, etching progresses easily in the portion corresponding to the second spring portion 23B (see FIG. 5) extending along the length direction DL, while etching progresses less in the portion corresponding to the first spring portion 23A (see FIG. 5) extending along the width direction DW. This causes variations in the amount of etching between the spring portions 23A, 23B included in one spring member 20.

[0040] In this regard, the metal foil 10 of the present disclosure satisfies condition 5, thereby preventing the surface position of the central region RC from becoming excessively high. This prevents the etching solution supplied to the central region RC from flowing forcefully from the central region RC toward each of the end regions RE1, RE2 according to the difference in the elongation differential rate. Furthermore, since the metal foil 10 simultaneously satisfies conditions 5 and 6, the difference in surface position between the central region RC and each of the end regions RE1, RE2 is reduced. This prevents the etching solution from flowing according to the difference in surface position at each position on the metal foil 10.

[0041] Moreover, since the metal foil 10 of the present disclosure satisfies condition 1, it is possible to suppress dimensional variation in the spring member 20 manufactured by etching the metal foil 10, even when the metal foil 10 is thick enough to easily cause unevenness in the surface position and the etching time is accordingly long.

[0042] Thus, according to the metal foil 10 of the present disclosure, even if the metal foil 10 has a corrugated shape in which the differential elongation rate is large in the central region RC in the width direction DW, the flow of the etching solution supplied to the metal foil 10 is prevented from becoming uneven. As a result, even if the spring member 20 is manufactured by wet etching a thick metal foil 10 having a thickness of 100 μm or more and 200 μm or less, the occurrence of dimensional variation in the spring member within the plane of the metal foil 10 is prevented.

[0043] Furthermore, the central region RC and the end regions RE1, RE2 are set within the above-mentioned ranges in the width direction DW. Therefore, the gradient of the elongation difference between the central region RC and the end regions RE1, RE2 is prevented from becoming large compared to when the central region RC is shorter and the end regions RE1, RE2 are longer. This further prevents the flow of the etching solution supplied to the metal foil 10 from becoming uneven.

[0044] When the spring member 20 is manufactured from the metal foil 10, liquids such as a developer, a stripper, and a cleaning liquid are supplied to the metal foil 10 in addition to the etching liquid. The developer is a liquid for developing the resist layer located on the surface of the metal foil 10. The stripper is a liquid for stripping the resist layer remaining on the surface of the metal foil 10 after etching. The cleaning liquid is a cleaning liquid for removing the developer from the surface, a cleaning liquid for removing the etching liquid from the surface, a cleaning liquid for removing the stripper from the surface, and a cleaning liquid for removing the stripper from the surface. The metal foil 10 of the present disclosure can also improve the uniformity of processing using these liquids, not just the etching liquid.

[0045] Furthermore, the metal foil 10 of the present disclosure can ensure adhesion between the resist layer and the metal foil 10 and the precision of exposure of the resist layer. Furthermore, the metal foil 10 of the present disclosure can also reduce misalignment when the metal foil 10 is transported using a roll-to-roll method, which, combined with the fact that non-uniformity in the liquid flow is unlikely to occur, can further improve the uniformity of processing.

[0046] In this way, the metal foil 10 that satisfies conditions 1 to 6 and the effects obtained by the metal foil 10 can only be derived by recognizing the issues that arise in surface processing using liquids due to the difference between the differential elongation rate in the central region RC and the differential elongation rate in each end region RE1, RE2.

[0047] The metal foil 10 may further satisfy the following condition 7. (Condition 7) The unit length in the width direction DW is 300 mm, and the average value of the elongation difference rate per unit length is 10 × 10 -5 The following is the result.

[0048] When the metal foil 10 satisfies condition 7, the differential elongation rate in the length direction DL is suppressed over the entire unit length, thereby improving the flatness of the metal foil 10. When the unit length in the width direction DW is equal to the entire length of the metal foil 10 in the width direction DW, the average value over the entire width direction of the metal foil 10, including the central region RC, is 10 × 10 -5Since the above condition is satisfied, the flatness of the metal foil 10 is improved.

[0049] The metal foil 10 may further satisfy at least one of the following conditions 8 and 9. That is, the metal foil 10 may satisfy only one of conditions 8 and 9, or may satisfy both conditions 8 and 9.

[0050] (Condition 8) In each of the first end region RE1 and the second end region RE2, the minimum value of the differential elongation rate is 1.0 × 10 -5 That's all. (Condition 9) In the central region RC, the minimum value of the expansion differential rate is 5.0 × 10 -5 That's all.

[0051] When the metal foil 10 satisfies at least one of conditions 8 and 9, it is possible to reduce the load in manufacturing the metal foil 10 compared to when the minimum value of the differential elongation rate of the metal foil 10 is a smaller value.

[0052] [Spring member] The spring member 20 will be described with reference to Fig. 5. Fig. 5 schematically shows the planar structure of the spring member 20 as seen from a viewpoint opposite to the plane in which the spring member 20 extends.

[0053] As shown in FIG. 5, the spring member 20 includes an outer frame portion 21, an inner frame portion 22, and a spring portion 23. In the example shown in FIG. 5, the outer shape of the outer frame portion 21 is octagonal, and the outer shape of the inner frame portion 22 is circular. The spring portion 23 has a folded line shape. The outer shapes of the outer frame portion 21 and the inner frame portion 22 may be changed depending on the shapes of other members included in the drive mechanism of the camera module in which the spring member 20 is mounted, i.e., members other than the spring member 20. The inner frame portion 22 is located within an area defined by the outer frame portion 21. The spring portion 23 connects the inner frame portion 22 to the outer frame portion 21.

[0054] In the example shown in FIG. 5, the spring member 20 includes four spring portions 23. The spring members 20 are attached to the metal foil 10 such that two of the four spring portions 23 sandwich the inner frame portion 22 in the length direction DL and the other two spring members 20 sandwich the inner frame portion 22 in the width direction DW. Of the four spring portions 23, the spring portions 23 that sandwich the inner frame portion 22 in the length direction DL are first spring portions 23A. Of the four spring portions 23, the spring portions 23 that sandwich the inner frame portion 22 in the width direction DW are second spring portions 23B. Each first spring portion 23A includes a plurality of leaf springs 23A1 extending along the width direction DW. Each second spring portion 23B includes a plurality of leaf springs 23B1 extending along the length direction DL.

[0055] The length of the leaf spring 23A1 included in the first spring portion 23A along the longitudinal direction DL is the spring width SWA of the leaf spring 23A1. The length of the leaf spring 23B1 included in the second spring portion 23B along the width direction DW is the spring width SWB of the leaf spring 23B1.

[0056] The lens drive type drive mechanism may include one spring member 20 or a pair of spring members 20. When the drive mechanism includes one spring member 20, the spring member 20 and the lens are aligned with a gap between them in the optical axis direction of the lens. When the drive mechanism includes a pair of spring members 20, the pair of spring members 20 are arranged to sandwich the lens in the optical axis direction of the lens. When the drive mechanism includes a pair of spring members 20, the pair of spring members 20 are arranged to sandwich the lens in the optical axis direction of the lens. When the position of the inner frame portion 22 connected to each outer frame portion 21 changes relative to that outer frame portion 21 in the optical axis direction, the position of the lens in the optical axis direction of the lens changes. This makes it possible to correct camera shake using the lens drive type drive mechanism.

[0057] The sensor-driven drive mechanism may include one spring member 20 or a pair of spring members 20. When the drive mechanism includes one spring member 20, the spring member 20 and the image sensor are aligned with a gap between them in the optical axis direction of the lens. When the drive mechanism includes a pair of spring members 20, the pair of spring members 20 are arranged to sandwich the image sensor in the optical axis direction of the lens. When the drive mechanism includes a pair of spring members 20, the pair of spring members 20 are arranged to sandwich the image sensor in the optical axis direction of the lens. When the position of the inner frame portion 22 connected to each outer frame portion 21 changes relative to that outer frame portion 21 in the optical axis direction, the position of the image sensor in the optical axis direction of the lens changes. This makes it possible to correct camera shake using the sensor-driven drive mechanism.

[0058] The camera module is provided with a drive mechanism including the above-described spring member 20. Electronic devices in which the camera module is mounted may be, for example, mobile phone terminals, smartphones, tablet terminals, and notebook personal computers.

[0059] [Method for manufacturing metal foil for spring components] A method for producing the metal foil 10 will be described with reference to FIGS. The method for manufacturing the metal foil 10 includes rolling a base material to obtain the metal foil 10. Rolling the base material involves rolling the base material so that the metal foil 10 satisfies the above-mentioned conditions 1 to 6. The method for manufacturing the metal foil 10 will be described in more detail below with reference to the drawings.

[0060] 6 and 7 show a schematic diagram of the process of rolling the base material to form the metal foil 10. FIG. 6, when the metal foil 10 is manufactured, first, a strip-shaped base material BM1 extending along a rolling direction DR is prepared. The rolling direction DR is parallel to the longitudinal direction DL of the metal foil 10. Next, the base material BM1 is transported along the transport direction toward a rolling mill RE equipped with a pair of rolling rolls RL1 and RL2 so that the rolling direction DR of the base material BM1 and the transport direction in which the base material BM1 is transported are parallel.

[0061] When the base material BM1 reaches between the pair of rolling rolls RL1, RL2, the base material BM1 is rolled by the pair of rolling rolls RL1, RL2. This reduces the thickness of the base material BM1 and stretches the base material BM1 along the conveying direction, thereby obtaining a rolled material BM2. The rolled material BM2 is wound around a core C. Note that the rolled material BM2 may be handled in a stretched strip shape without being wound around a core C. The thickness of the rolled material BM2 is within the range of 100 μm to 200 μm.

[0062] As shown in Fig. 7, in order to remove residual stress accumulated inside the rolled material BM2 formed by rolling the base material BM1, the rolled material BM2 is annealed using an annealing device AE. This results in a metal foil 10. The rolled material BM2 is annealed while being pulled along the conveying direction, so that a metal foil 10 can be obtained in which residual stress is reduced compared to the rolled material BM2 before annealing.

[0063] As described above, the material forming the base material BM1 may include any one selected from the group consisting of stainless steel alloy, beryllium copper, nickel-tin copper, phosphor bronze, Corson alloy, and titanium-copper. Because these metals have high hardness, in other words, they are less likely to stretch than metals with lower hardness, i.e., softer metals, variations in the degree of rolling are likely to occur within the base material BM1. Furthermore, variations in the degree of rolling are likely to occur among multiple base materials BM1. Because the metal foil 10 has high hardness and therefore is prone to variations in the degree of rolling within the metal foil 10, the effect of the upper limit values ​​of the differential elongation rates in the central region RC and each of the end regions RE1 and RE2 is more pronounced.

[0064] The manufacturing method of the metal foil 10 may include a step of selecting the metal foil 10 from the annealed rolled material. In this case, after preparing a plurality of rolled materials obtained through rolling and annealing, the surface distance in the length direction DL of each rolled material is measured at each position in the width direction DW. Then, using the measured surface distance, the differential elongation rate in the length direction DL at each position in the width direction DW is calculated. Next, from the plurality of rolled materials, a rolled material that satisfies the above-mentioned conditions 1 to 6 is selected as the metal foil 10. The selected metal foil 10 is used to manufacture the spring member 20.

[0065] In this way, the conditions for sorting the metal foil 10 in the sorting step include conditions 1 to 6. Note that the conditions for sorting the metal foil 10 in the sorting step may also include at least one of conditions 7 to 9. That is, the conditions for sorting the metal foil 10 in the sorting step may include only one of conditions 7 to 9, or may include two or more of them.

[0066] In the production of the metal foil 10, the rotational speed of the rolling rolls RL1 and RL2, the pressing force between the rolling rolls RL1 and RL2, the temperature of the rolling rolls RL1 and RL2, the number of rolling rolls RL1 and RL2, and the annealing temperature of the rolling material BM2 are set so that conditions 1 to 6 are satisfied. Alternatively, the rolling mill RE may include, for example, a pair of backup rolls, an intermediate roll, and a pair of work rolls, each of which is the rolling roll RL1 and RL2. The work rolls may also be crown rolls. In this case, the crown amount of the work rolls, the diameter of the work rolls, the shift amount of the work rolls in the width direction DW, and the shift amount of the intermediate rolls in the width direction DW may be set so that conditions 1 to 6 are satisfied.

[0067] [Method for manufacturing spring components] A method for manufacturing the spring member 20 will be described with reference to FIGS. The method for manufacturing the spring member 20 includes forming a resist mask on a strip-shaped metal foil 10 and patterning the metal foil 10 by wet etching using the resist mask. The metal foil 10 satisfies the above-mentioned conditions 1 to 6. The method for manufacturing the spring member 20 will be described below with reference to the drawings.

[0068] 8, when manufacturing the spring member 20, first, a first resist layer PR1 is formed on the front surface 10F of the metal foil 10, and a second resist layer PR2 is formed on the back surface 10R. Note that, although the resist layers PR1 and PR2 are formed from positive photoresists in the examples described with reference to FIGS. 8 to 12, each of the resist layers PR1 and PR2 may be formed from negative photoresists.

[0069] 9, a first photomask PM1 is placed on the first resist layer PR1, and a second photomask PM2 is placed on the second resist layer PR2. Then, the first resist layer PR1 is exposed using the first photomask PM1, and the second resist layer PR2 is exposed using the second photomask PM2.

[0070] As shown in FIG. 10, the exposed resist layers PR1 and PR2 are developed, thereby forming a first resist mask RM1 from the first resist layer PR1 and a second resist mask RM2 from the second resist layer PR2.

[0071] 11, the metal foil 10 is wet-etched using resist masks RM1 and RM2. During this process, the metal foil 10 is etched from both the front surface 10F and the back surface 10R. As a result, through-holes are formed in the metal foil 10, penetrating the metal foil 10 in the thickness direction, resulting in the formation of an outer frame portion 21, an inner frame portion 22 spaced from the outer frame portion 21, and spring portions 23 connecting the inner frame portion 22 to the outer frame portion 21.

[0072] In this case, because the metal foil 10 satisfies conditions 1 to 6, dimensional variations are suppressed in the leaf springs 23A1, 23B1 included in the spring portion 23 of the spring member 20. Furthermore, because the metal foil 10 satisfies conditions 1 to 6, it is possible to obtain a spring member 20 in which dimensional variations are suppressed within a predetermined range without changing the wet etching conditions depending on the differential elongation rate of the metal foil 10. Therefore, in manufacturing the spring member 20, it is not necessary to change the wet etching conditions depending on the differential elongation rate, so it is also possible to eliminate errors in combining variations in the differential elongation rate and the wet etching conditions. Note that, for example, when spray etching is performed, the wet etching conditions include the amount of spray and the arrangement of the spray relative to the metal foil 10.

[0073] As shown in FIG. 12, after the resist masks RM1 and RM2 are removed from the etched metal foil 10, an etching pattern corresponding to the spring member 20 can be cut out from the etched metal foil 10, thereby obtaining the spring member 20.

[0074] [Example] An example and a comparative example will be described with reference to FIGS. [Example 1] First, a base material BM1 made of titanium copper (C1990, JIS H 3130:2018) was rolled to form a rolled material BM2, and then a slitting process was performed to cut the rolled material BM2 to a desired size in the width direction DW, thereby adjusting the length of the rolled material BM2 in the width direction DW. Subsequently, the rolled material BM2 was annealed to obtain a metal foil 10 of Example 1 having a length in the width direction DW of 300 mm and a thickness of 150 μm.

[0075] Next, as shown in Figure 13, a test foil 10M of Example 1 having a length in the longitudinal direction DL of 500 mm was cut out from the metal foil 10 of Example 1. Subsequently, the surface distance in the longitudinal direction DL of the cut-out test foil 10M was measured, and then the measured surface distance was used to calculate the elongation difference rate. At this time, the following conditions were used as the measurement conditions for the surface distance.

[0076] Measuring device: Nikon Corporation CNC image measuring system VMR-6555 Measurement range ZL length direction DL length: 300 mm Length of non-measurement range ZE in the length direction DL: 100 mm Measurement interval in the length direction DL: 1 mm Measurement interval in width direction DW: 15 mm

[0077] The calculation results of the elongation difference rate in Example 1 are shown in Fig. 14 and Fig. 19. The average value of the elongation difference rate per unit length in the width direction DW was 7.5 × 10 -5 It was.

[0078] [Examples 2 and 3 and Comparative Examples 1 and 2] In Example 2, the shift amount of the work roll in the width direction DW was changed compared to Example 1, and the rolling reduction was increased compared to Example 1, resulting in a metal foil 10 of Example 2 having a thickness of 120 μm. In Example 3, the shift amount of the work roll in the width direction DW was changed compared to Examples 1 and 2, and the rolling reduction was decreased compared to Example 1, resulting in a metal foil 10 of Example 3 having a thickness of 200 μm. In Comparative Example 1, a work roll with a larger crown amount than the work roll used to produce the metal foil 10 of Example 3 was used, resulting in a metal foil 10 of Comparative Example 1 having a thickness of 150 μm. In Comparative Example 2, a work roll with a larger crown amount than the work roll used to produce the metal foil 10 of Comparative Example 1 was used, resulting in a metal foil 10 of Comparative Example 2 having a thickness of 150 μm.

[0079] The calculation results of the elongation difference rate in Example 2 are shown in Figs. 15 and 19. The average value of the elongation difference rate per unit length in the width direction DW was 11.7 × 10 -5 The calculation results of the elongation difference rate in Example 3 are shown in Fig. 16 and Fig. 19, and the average value of the elongation difference rate per unit length in the width direction DW was 8.1 × 10 -5 The calculation results of the elongation difference rate in Comparative Example 1 are shown in Fig. 17 and Fig. 19, and the average value of the elongation difference rate per unit length in the width direction DW was 19.9 × 10 -5 The calculation results of the elongation difference rate in Comparative Example 2 are shown in Fig. 18 and Fig. 19, and the average value of the elongation difference rate per unit length in the width direction DW was 68.8 × 10 -5 It was.

[0080] [Metal foil etching] Resist masks RM1 and RM2 having a plurality of openings corresponding to the shape of the spring members 20 were formed on the front and back surfaces of each measurement foil 10M. Then, the measurement foil 10M was wet-etched from both the front and back surfaces using the two resist masks RM1 and RM2. For the measurement foil 10M, unit areas each corresponding to one spring member 20 and having a 20 mm square shape were arranged in a grid pattern at equal intervals in both the length direction DL and the width direction DW. Therefore, for each of the resist masks RM1 and RM2, unit patterns corresponding to the shape of one spring member 20 were also arranged in a grid pattern at equal intervals in both the length direction DL and the width direction DW.

[0081] In the unit pattern, the opening widths of the resist masks RM1 and RM2 corresponding to the gaps between the leaf springs 23A1 and 23B1 were set to 100 μm, and the pitch between adjacent leaf springs 23A1 and 23B1 was set to 200 μm in the portion of the spring member 20 where the folded spring portion 23 was formed. Here, the pitch between adjacent leaf springs 23A1 and 23B1 refers to the distance between the center lines of the adjacent leaf springs 23A1 and 23B1 that are parallel to each other in the etching pattern design.

[0082] In addition, multiple unit patterns were formed on each of the resist masks RM1 and RM2 so that, in a planar view facing the surface 10MS of the measurement foil 10M, the entirety of one unit pattern of the resist mask RM1 located on the surface 10MS of the measurement foil 10M overlaps the entirety of one unit pattern of the resist mask RM2 located on the back surface of the measurement foil 10M.

[0083] Using these resist masks RM1 and RM2, a plurality of etching patterns corresponding to the shapes of the spring members 20 were formed in the measurement foil 10M. In the etching patterns, the design values ​​of the spring widths SWA and SWB of the spring portion 23 in a plan view were set to 30 μm.

[0084] [Method of measuring spring width] The spring portion 23 of the spring member 20 included in each of the etched measurement foils 10M was embedded in synthetic resin. Then, the embedded spring portion 23 was cut using a microtome to expose a cross section of the spring portion 23 in a plane perpendicular to the extension direction of the leaf springs 23A1 and 23B1 included in the spring portion 23. For one spring portion 23, a cross section in a plane perpendicular to the extension direction of the leaf spring 23A1 and a cross section in a plane perpendicular to the extension direction of the leaf spring 23B1 were exposed.

[0085] The spring widths SWA and SWB of the leaf springs 23A1 and 23B1 of each etched pattern on the surface 10MS of the measurement foil 10M were measured. Then, for each of the regions RC, RE1, and RE2, the variation was calculated by subtracting the minimum value from the maximum value of all the measured values ​​of the spring widths SWA and SWB. Furthermore, for each of the regions RC, RE1, and RE2, the difference value was calculated by subtracting the spring width SWB from the spring width SWA in each unit pattern, and the directional difference of the spring widths was calculated as the average of the difference values ​​in each of the regions RC, RE1, and RE2.

[0086] When measuring the spring widths SWA and SWB of the spring portion 23, a digital microscope (VHX-7000, manufactured by Keyence Corporation) was used, and the magnification of the objective lens in the digital microscope was set to 200 times.

[0087] [Evaluation results] [Expansion rate] As shown in Figs. 14 and 19, in Example 1, the maximum value of the elongation difference rate in the central region RC was 24.9 × 10 -5 The maximum value of the differential elongation rate in the first end region RE1 is 4.2 × 10 -5 The maximum value of the differential elongation rate in the second end region RE2 is 2.8 × 10 -5 15 and 19, in Example 2, the maximum value of the elongation difference rate in the central region RC was 29.3 × 10 -5 The maximum value of the differential elongation rate in the first end region RE1 is 7.5 × 10 -5 The maximum value of the differential elongation rate in the second end region RE2 is 9.7 × 10 -5 16 and 19, in Example 3, the maximum value of the elongation difference rate in the central region RC was 18.7 × 10 -5 The maximum value of the differential elongation rate in the first end region RE1 is 3.8 × 10 -5 The maximum value of the differential elongation rate in the second end region RE2 is 3.2 × 10 -5 It was recognized that this was the case.

[0088] As shown in Figs. 17 and 19, in Comparative Example 1, the maximum value of the elongation difference rate in the central region RC was 46.8 × 10 -5 The maximum value of the differential elongation rate in the first end region RE1 is 10.1 × 10 -5 The maximum value of the differential elongation rate in the second end region RE2 is 4.2 × 10 -5 18 and 19, in Comparative Example 2, the maximum value of the elongation difference rate in the central region RC was 149.9 × 10 -5 The maximum value of the differential elongation rate in the first end region RE1 is 11.9 × 10 -5 The maximum value of the differential elongation rate in the second end region RE2 is 24.4 × 10 -5 It was recognized that this was the case.

[0089] Spring width As shown in Figure 20, the variation in spring widths SWA and SWB was greatest in the central region RC for all measurement foils 10M, and it was found that the variation in the central region RC in Comparative Examples 1 and 2 was greater than the variation in the central region RC in Examples 1 to 3.

[0090] These results indicate that because the central region RC includes peaks 10A due to differences in the differential expansion rate, the amount of etching solution supplied to each position in the central region RC is likely to vary, which in turn leads to variations in the spring width resulting from etching. Furthermore, in Comparative Examples 1 and 2, the maximum value of the differential expansion rate in the central region RC is larger than in Examples 1 to 3, and therefore the slope of the differential expansion rate is also larger. This means that the amount of etching solution supplied to each position in the central region RC is even more likely to vary, resulting in even more variation in the spring width. In other words, in Examples 1 to 3, the maximum value of the differential expansion rate in the central region RC is smaller than in Comparative Examples 1 and 2, and therefore the slope of the differential expansion rate is also smaller. This means that the amount of etching solution supplied to each position in the central region RC is less likely to vary, resulting in less variation in the spring width.

[0091] On the other hand, it was found that the directional difference of the spring width was similar regardless of the position in the width direction DW in Examples 1 to 3. In contrast, it was found that in Comparative Examples 1 and 2, the difference between the directional difference of the spring width in the end regions RE1, RE2 and the directional difference of the spring width in the central region RC was large, and the directional difference of the spring width in the end regions RE1, RE2 itself was also large.

[0092] From these results, it can be said that in Examples 1 to 3, the maximum value of the differential elongation rate in the central region RC is small, and the difference between the differential elongation rate in the central region RC and the differential elongation rate in each end region RE1, RE2 is also small, so the directional difference in spring width is suppressed.

[0093] As described above, according to one embodiment of the metal foil for a spring member, the method for manufacturing the metal foil for a spring member, and the method for manufacturing a spring member, the following effects can be obtained. (1) Even if the metal foil 10 has a corrugated shape in which the differential elongation rate is large in the central region RC in the width direction DW, the flow of the etching solution supplied to the metal foil 10 is prevented from becoming uneven. As a result, even if the spring member 20 is manufactured by wet etching a thick metal foil 10 having a thickness of 100 μm or more and 200 μm or less, the occurrence of dimensional variations in the spring member within the plane of the metal foil 10 is prevented.

[0094] (2) When the central region RC and the end regions RE1, RE2 are set within the above-mentioned ranges in the width direction DW, the gradient of the elongation difference between the central region RC and the end regions RE1, RE2 is prevented from becoming large compared to when the central region RC is shorter and the end regions RE1, RE2 are longer. This further prevents the flow of the etching solution supplied to the metal foil 10 from becoming uneven.

[0095] (3) The average value of the differential elongation rate per unit length in the width direction (DW) is 1 × 10 -5 If it is equal to or less than this, the differential elongation rate in the length direction DL is suppressed over the entire unit length, and therefore the flatness of the metal foil 10 is improved.

[0096] (4) When the metal foil 10 includes any one selected from the group consisting of stainless steel alloy, beryllium copper, nickel-tin copper, phosphor bronze, Corson alloy, and titanium-copper, the metal foil for spring members has high hardness. This makes it easy for the degree of rolling to vary within the metal foil 10, and therefore the effect of the upper limit values ​​of the differential elongation rates in the central region RC and each of the end regions RE1 and RE2 becomes more pronounced.

[0097] The above-described embodiment can be modified as follows. [Metal foil manufacturing method] In the rolling process, a rolling mill equipped with multiple pairs of rolls can be used, and BM1 can be rolled using multiple pairs of rolls. Using multiple pairs of rolls also allows for greater flexibility in the control parameters required to satisfy conditions 1 to 6.

[0098] In the annealing step, it is also possible to anneal the rolled material BM2 wound around the core C, rather than pulling the rolled material BM2 in the longitudinal direction DL. Note that, in the method of annealing the rolled material BM2, the metal foil 10 may develop a warping tendency depending on the roll diameter. Therefore, depending on the material of the metal foil 10 and the size of the roll diameter when wound around the core C, it is preferable to anneal the rolled material BM2 while pulling it.

[0099] The metal foil 10 can also be manufactured by alternately repeating the rolling step and the annealing step multiple times. After annealing the rolled material BM2, the rolled material BM2 may be cut so that the dimension in the width direction DW becomes the width W. This also makes it possible to obtain a metal foil 10 having the width W in the width direction DW. [Explanation of symbols]

[0100] 10...Metal foil for spring components 20...Spring member 21...Outer frame 22...Inner frame 23...Spring part E1...first end E2…Second end PC…Central part RC…Central area RE1...first end area RE2…Second end area

Claims

1. A metal foil for a spring member, which is a band-shaped metal foil used to manufacture a spring member by wet etching, The thickness of the metal foil is 100 μm or more and 200 μm or less, the shapes of the metal foil along the length direction at each position in the width direction of the metal foil are different from each other, and each shape is a wave shape having concaves and convexes repeated in the length direction of the metal foil, the length in the longitudinal direction on the surface of the metal foil is a surface distance; the minimum value of the surface distances at each position in the width direction of the metal foil is the minimum surface distance, The ratio of the difference between the surface distance at each position in the width direction of the metal foil and the minimum surface distance to the minimum surface distance is the differential elongation rate in the length direction, The differential elongation rate in the central region in the width direction of the metal foil is larger than the differential elongation rates in the first end region and the second end region in the width direction, the differential elongation rate decreases from the central region toward the first end region and decreases from the central region toward the second end region, The maximum value of the differential elongation rate in the central region is 30×10 －５ is as follows: The maximum value of the differential elongation rate in each of the first end region and the second end region is 10×10 －５ is Metal foil for spring components.

2. the central portion in the width direction of the metal foil for a spring member is the central portion in the width direction of the central region, and the length of the central region in the width direction is 30% of the length of the metal foil in the width direction; the first end region includes a first end portion of the metal foil for a spring member in the width direction, and the length of the first end region in the width direction is 20% of the length of the metal foil in the width direction; The second end region includes a second end portion in the width direction of the metal foil for a spring member, and the length of the second end region in the width direction is 20% of the length of the metal foil in the width direction. The metal foil for a spring member according to claim 1 .

3. The unit length in the width direction is 300 mm, The average value of the elongation difference rate per unit length is 10 × 10 －５ is The metal foil for a spring member according to claim 1 or 2.

4. The metal foil includes any one selected from the group consisting of stainless steel alloy, beryllium copper, nickel-tin copper, phosphor bronze, Corson alloy, and titanium copper. The metal foil for a spring member according to claim 1 or 2.

5. A method for manufacturing a metal foil for a spring member, which is a metal foil having a belt shape and is used to manufacture a spring member by wet etching, comprising: rolling a base material to obtain the metal foil; The thickness of the metal foil is 100 μm or more and 200 μm or less, the shapes of the metal foil along the length direction at each position in the width direction of the metal foil are different from each other, and each shape is a wave shape having concaves and convexes repeated in the length direction of the metal foil, the length in the longitudinal direction on the surface of the metal foil is a surface distance; the minimum value of the surface distances at each position in the width direction of the metal foil is the minimum surface distance, The ratio of the difference between the surface distance at each position in the width direction of the metal foil and the minimum surface distance to the minimum surface distance is the differential elongation rate in the length direction, The differential elongation rate in the central region in the width direction of the metal foil is larger than the differential elongation rates in the first end region and the second end region in the width direction, the differential elongation rate decreases from the central region toward the first end region and decreases from the central region toward the second end region, The maximum value of the differential elongation rate in the central region is 30×10 －５ is as follows: The maximum value of the differential elongation rate in the first end region and the second end region is 10×10 －５ The base material is rolled as follows: A method for manufacturing metal foil for spring members.

6. forming a resist mask on a strip-shaped metal foil; patterning the metal foil by wet etching using the resist mask, The thickness of the metal foil is 100 μm or more and 200 μm or less, the shapes of the metal foil along the length direction at each position in the width direction of the metal foil are different from each other, and each shape is a wave shape having concaves and convexes repeated in the length direction of the metal foil, the length in the longitudinal direction on the surface of the metal foil is a surface distance; the minimum value of the surface distances at each position in the width direction of the metal foil is the minimum surface distance, The ratio of the difference between the surface distance at each position in the width direction of the metal foil and the minimum surface distance to the minimum surface distance is the differential elongation rate in the length direction, The differential elongation rate in the central region in the width direction of the metal foil is larger than the differential elongation rates in the first end region and the second end region in the width direction, the differential elongation rate decreases from the central region toward the first end region and decreases from the central region toward the second end region, The maximum value of the differential elongation rate in the central region is 30×10 －５ is as follows: The maximum value of the differential elongation rate in the first end region and the second end region is 10×10 －５ is A method for manufacturing a spring member.

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