Cu-Ni-Sn Based Copper Alloy Foil, Copper Rolled Product, Electronic Device Parts and Autofocus Camera Module

Abstract

Provided is a thinner CuNiSn based copper alloy foil that has a foil thickness of 0.1 mm or less, has improved solder wettability and improved solder adhesion strength, and can be suitably used as a conductive spring material for use in electronic device parts such as autofocus camera modules; a copper rolled product; an electronic device part; and an autofocus camera module. The CuNiSn based copper alloy foil according to one embodiment of the present invention has a foil thickness of 0.1 mm or less; and contains from 14% by mass to 22% by mass of Ni, from 4% by mass to 10% by mass of Sn, the balance being copper and inevitable impurities; and has a maximum height roughness Rz of from 0.1 m to 1 m, on a surface in a direction parallel to a rolling direction.

Claims

1. A CuNiSn based copper alloy foil having a foil thickness of 0.1 mm or less, the CuNiSn based copper alloy foil comprising: from 14% by mass to 22% by mass of Ni; and from 4% by mass to 10% by mass of Sn; the balance being Cu and inevitable impurities; and the CuNiSn based copper alloy having a maximum height roughness Rz of from 0.1 m to 1 m, on a surface in a direction parallel to a rolling direction.

2. The CuNiSn based copper alloy foil according to claim 1, wherein the CuNiSn based copper alloy foil has a tensile strength of 1100 MPa or more in a direction parallel to the rolling direction.

3. The CuNiSn based copper alloy foil according to claim 1, wherein the CuNiSn based copper alloy foil has a total content of Mn, Ti, Si, Al, Zr, B, Zn, Nb, Fe, Co, Mg, and Cr of from 0% by mass to 1.0% by mass.

4. A copper rolled product comprising the CuNiSn based copper alloy foil according to claim 1.

5. An electronic device part comprising the CuNiSn based copper alloy foil according to claim 1.

6. The electronic device part according to claim 5, wherein the electronic device part is an autofocus camera module.

7. An autofocusing camera module comprising: a lens; a spring member for elastically biasing the lens to an initial position in an optical axis direction; and an electromagnetic driver configured to generate electromagnetic force for withstanding a biasing force of the spring member so that the lens can be driven in the optical axis direction, wherein the spring member comprises the CuNiSn based copper alloy foil according to claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0029] FIG. 1 is a cross-sectional view showing an autofocus camera module according to one embodiment of the present invention.

[0030] FIG. 2 is an exploded perspective view of the autofocus camera module in FIG. 1.

[0031] FIG. 3 is a cross-sectional view showing the operation of the autofocus camera module in FIG. 1.

[0032] FIG. 4 is a graph showing an example of measurement results of a solder adhesive strength test in Examples.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Embodiments of the present invention will be described in detail below.

[0034] A CuNiSn based copper alloy foil according to one embodiment of the present invention has a foil thickness of 0.1 mm or less; and contains from 14% by mass to 22% by mass of Ni, from 4% by mass to 10% by mass of Sn, the balance being copper and inevitable impurities; and has a maximum height roughness Rz of from 0.1 m to 1 m, on a surface in a direction parallel to a rolling direction.

Ni Concentration

[0035] The CuNiSn based copper alloy foil according to the present invention has a Ni concentration of from 14% by mass to 22% by mass. Ni contributes to solute strengthening, precipitation strengthening, and improvement of strength due to spinodal decomposition by an aging treatment, in the alloy. Further, Ni ensures stress relaxation resistance and heat resistance (high strength maintainability at elevated temperature). If the Ni content is less than 14% by mass, the strength will not be improved during age hardening. On the other hand, if Ni is contained in an amount more than 22% by mass, a decrease in conductivity will become remarkable, which is not preferable in terms of cost. From this viewpoint, the Ni concentration is preferably from 14.5% by mass to 21.5% by mass, and more preferably from 15% by mass to 21% by mass.

Sn Concentration

[0036] The CuNiSn based copper alloy foil according to the present invention has a Sn concentration of from 4% by mass to 10% by mass. Sn contributes to improvement of strength of the alloy due to spinodal decomposition by an aging treatment in the alloy without significantly decreasing the conductivity of the alloy. If the Sn content is less than 4%, the spinodal decomposition will hardly occur. On the other hand, if Sn is contained in an amount more than 10% by mass, a low melting point composition will tend to be formed and segregation will be remarkable, so that workability is impaired. Therefore, the Sn concentration is preferably from 4.5% by mass to 9% by mass, and more preferably from 5% by mass to 8% by mass.

Other Additive Elements

[0037] The CuNiSn based copper alloy foil according to the present invention may have a total content of Mn, Ti, Si, Al, Zr, B, Zn, Nb, Fe, Co, Mg and Cr of from 0% by mass to 1.0% by mass. When at least one element selected from the group consisting of Mn, Ti, Si, Al, Zr, B, Zn, Nb, Fe, Co, Mg and Cr is contained, an increase in strength can be expected due to solid solution in the matrix or formation of deposited particles. The total content of these elements may be 0% by mass, i.e., these elements may not be contained. The reason why the upper limit of the total content of these elements is 1.0% by mass is that the amount of more than 1.0% by mass cannot provide any further increase in the strength, as well as it will lead to degradation of workability and a material that is easily cracked during rolling.

[0038] The total content of Mn, Ti, Si, Al, Zr, B, Zn, Nb, Fe, Co, Mg and Cr may be typically from 0.05% by mass to 1.0% by mass, and more typically from 0.1% by mass to 1.0% by mass.

Tensile Strength

[0039] A tensile strength required for the CuNiSn based copper alloy foil suitable as the conductive spring material for the autofocus camera module is 1100 MPa or more, and preferably 1200 MPa or more, and more preferably 1300 MPa or more. In the present invention, the tensile strength of the CuNiSn based copper alloy foil was measured in a direction parallel to a rolling direction, and the tensile strength is measured in accordance with JIS Z2241-2011 (Metal Material Tensile Test Method).

Surface Roughness

[0040] The CuNiSn based copper alloy foil according to the present invention has a maximum height roughness Rz of from 0.1 m to 1 m on the surface of the alloy in the direction parallel to the rolling direction. This allows a required improved solderability to be ensured and adhesion strength by solder to be improved, which are advantageous for production of, in particular an autofocus camera module if the copper metal foil is used for the autofocus camera module.

[0041] Here, the reason why the maximum height roughness Rz in the direction parallel to the rolling direction is specified is that the surface roughness significantly varies in the direction parallel to the rolling direction between the cases where an amount of oil pits during rolling is high and where an amount of oil pits is low.

[0042] More particularly, as long as the maximum height roughness Rz in the rolling parallel direction is within the range of from 0.1 m to 1 m, an actual surface area is not too large, so that the solder tends to wet and spread. Further, there are also moderate irregularities, so that adhesion of the solder is improved. It should be noted that a maximum height roughness Rz in a direction perpendicular to the rolling direction is also preferably from 0.1 m to 1 m.

[0043] In other words, if the maximum height roughness Rz in the direction parallel to the rolling direction is less than 0.1 m, an anchor effect cannot be obtained, and the adhesion is poor. On the other hand, if the maximum height roughness Rz in the direction parallel to the rolling direction is more than 1 m, it will take much time to wet the solder, so that the solder wettability is poor.

[0044] From this viewpoint, the maximum height roughness Rz on the surface in the direction parallel to the rolling direction is more preferably from 0.1 m to 0.4 m, and even more preferably from 0.1 m to 0.25 m.

[0045] The maximum height roughness Rz can be determined by taking a roughness curve having a reference length of 300 m along a direction parallel to the rolling direction or a direction perpendicular to the rolling direction of the CuNiSn based copper alloy foil, and measuring it from the curve in accordance with JIS B0601 (2013).

Thickness of Copper Alloy Foil

[0046] The CuNiSn based copper alloy foil according to the present invention has a foil thickness of 0.1 mm or less, and in a typical embodiment a foil thickness of from 0.018 mm to 0.08 mm, and in a more typical embodiment a foil thickness of from 0.02 mm to 0.05 mm.

Producing Method

[0047] As will be described below, the CuNiSn based copper alloy foil according to the present invention can be produced by working processes that carries out melting, casting, homogenization annealing, hot rolling, cold rolling 1, a solution treatment, cold rolling 2, an aging treatment, cold rolling 3 (final cold rolling) and a rust prevention treatment in this order.

[0048] To produce the CuNiSn based copper alloy foil according to the present invention, homogenization annealing should be carried out in order to eliminate segregation generated during solidification after melting and casting. If the homogenization annealing is not carried out, a surface shape of the final product will be affected and the hot workability of the ingot will be poor. For the homogenization annealing, for example, a temperature of 900 C. is maintained for 3 hours.

[0049] After the homogenization annealing, for example, hot rolling can be carried out at 800 C. with a degree of working of about 50%. However, the hot rolling may be omitted.

[0050] The subsequent cold rolling 1 is carried out in order to perform a solution treatment with a predetermined thickness. For the cold rolling 1, a higher degree of working is preferable in order to obtain fine crystal grains in the subsequent solution treatment, and for example, the degree of working may be about 90%.

[0051] The solution treatment should be carried out at or higher than a temperature at which second phase particles are not precipitated and at or lower a temperature at which liquid phase appears. Among such temperature ranges, a lower temperature of the solution treatment is more preferable, because it will not cause a decrease in strength, which will offset an increase in strength due to coarsening of crystal grains and development of a modulated structure. Specifically, the temperature of the solution treatment is, for example, from 720 C. to 850 C., and more preferably in a range of from solidus temperature to 800 C.

[0052] The cold rolling 2 is performed in order to increase strength before an aging treatment by introducing dislocation by rolling and also to increase strength after the aging treatment. Recrystallized grains obtained by the solution treatment in the cold rolling 2 are stretched.

[0053] To obtain the effect of increasing the strength as described above, the cold rolling 2 is preferably carried out at a rolling reduction rate (draft) of 55% or more, and more preferably 60% or more, and further preferably 65% or more. If the rolling reduction rate is less than 55%, it will be difficult to obtain a tensile strength of 1100 MPa or more. The upper limit of the rolling reduction rate is not particularly defined from the viewpoint of the strength intended by the present invention, but it does not industrially exceed 99.8%.

[0054] The cold rolling 2 is followed by an aging treatment. The aging treatment causes spinodal decomposition, so that a modulated structure is developed. The aging treatment is carried out at a temperature of from 350 to 500 C. for a heating time of from 3 minutes to 300 minutes. If the heating temperature is lower than 350 C., it will be difficult to obtain a tensile strength of 1100 MPa or more. If the temperature is higher than 500 C., precipitation will proceed and it will be difficult to obtain a tensile strength of 1100 MPa or more, and an oxide film will be excessively formed. If the heating time is less than 3 minutes or more than 300 minutes, it will be difficult to obtain a tensile strength of 1100 MPa or more.

[0055] To obtain the CuNiSn based copper alloy foil according to the present invention, it is important to use a rolling mill having a roll with a small diameter, control the rolling reduction rate and roll a final pass with a work roll having predetermined roughness, in a final cold rolling (cold rolling 3) after performing the aging treatment.

[0056] More particularly, since the CuNiSn based copper alloy foil is a high strength and hard foil which is not easily crushed, the final cold rolling is preferably carried out using a rolling mill provided with a small diameter roll having a diameter of from 30 mm to 120 mm. If the roll diameter is too large, the CuNiSn based copper alloy foil cannot be crushed to an intended thickness, and an amount of biting of a rolling oil during the rolling will be increased, so that oil pits may be easily generated. If the roll diameter is too small, the rolling speed will be restricted to a low level, so that there is concern that productivity will be decreased. For those reasons, it is more preferable to use a roll having a roll diameter of from 40 mm to 100 mm.

[0057] In the final cold rolling, the oil pits are formed on the surface of the foil, thereby resulting in a change of the surface roughness Rz of the CuNiSn based copper alloy foil to be produced. Therefore, the rolling reduction rate of the final pass of the final cold rolling is preferably from 9% to 35%. If the rolling reduction rate is too large, an amount of rolling oil entrapped between the rolling roll and the material will be decreased, so that the surface roughness Rz of the produced CuNiSn based copper alloy foil is decreased, which will lead to a decrease in solder adhesion. On the other hand, if the rolling reduction rate is too small, the amount of rolling oil entrapped between the rolling roll and the material will be increased, so that the surface roughness Rz of the produced CuNiSn based copper alloy foil is increased, which will lead to deterioration of solder wettability. Therefore, the rolling reduction rate of the final pass is preferably from 9% to 30%.

[0058] Furthermore, it is effective that the work roll used is made of die steel and the final pass is subjected to the rolling by a work roll having an arithmetic average roughness Ra of 0.1 pm or less on the surface. If the arithmetic average roughness Ra of the work roll in the final pass is larger, the surface roughness Rz of the material would tend to exceed 1 m. The arithmetic average roughness Ra of the work roll is determined by taking a roughness curve having a reference length of 400 m in the longitudinal direction, that is, in a direction corresponding to the direction perpendicular to the rolling direction of the above material, and measuring it in accordance with JIS B0601.

[0059] It should be noted that aging annealing may be performed after the cold rolling 2. In general, after the aging treatment, surface pickling, polishing or the like is performed in order to remove the oxide film or oxide layer formed on the surface. In the present invention, it is also possible to subject the surface to pickling, polishing or the like after the aging treatment.

[0060] The final cold rolling can be followed by a rust prevention treatment. The rust prevention treatment can be carried out under the same conditions as those of the prior art, and an aqueous solution of benzotriazole (BTA) or the like can be used.

Application

[0061] The CuNiSn based copper foil according to the present invention can be suitably used in various applications, in particular as a material for electronic parts such as switches, connectors, jacks, terminals, and relays, and more particularly as a conductive spring member for use in electronic device parts such as autofocus camera modules.

[0062] For example, the autofocus module can include a lens; a spring member for elastically biasing the lens to an initial position in the optical axis direction; and an electromagnetic drive means configured to generate electromagnetic force for withstanding the biasing force of the spring member so that the lens can be driven in the optical axis direction. In this case, the spring member can be the CuNiSn based copper alloy foil according to the present invention.

[0063] By way of example, the electromagnetic driving means can include a U-shaped cylindrical yoke; a coil housed inside an inner peripheral wall of the yoke, and a magnet enclosing the coil and housed inside the outer peripheral wall of the yoke.

[0064] FIG. 1 is a sectional view showing an example of the autofocus camera module according to the present invention, FIG. 2 is an exploded perspective view of the autofocus camera module in FIG. 1, and FIG. 3 is a cross-sectional view showing the operation of the autofocus camera module in FIG. 1.

[0065] An autofocus camera module 1 includes: a U-shaped cylindrical yoke 2; a magnet 4 attached to an outer wall of the yoke 2; a carrier 5 provided with a lens 3 in a central position; a coil 6 attached to the carrier 5; a base 7 to which the yoke 2 is attached; a frame 8 supporting the base 7; two spring members 9a, 9b for supporting the carrier 5 at the upper and lower positions; and two caps 10a, 10b covering these upper and lower positions. These two spring member 9a, 9b are the same articles, and support the carrier 5 by holding it from the upper and lower positions in the same positional relationship, while functioning as a power supply route to the coil 6. The carrier 5 moves upward by applying an electric current to the coil 6. It should be noted that the wordings upper and lower are used herein as needed, and they refer to upper and lower in FIG. 1 and the upper represents a positional relationship that is directed from the camera to a subject.

[0066] The yoke 2 is a magnetic material such as soft iron, and assumes a U-shaped cylindrical shape whose upper surface portion is closed, and has cylindrical inner wall 2a and outer wall 2b. A ring-shaped magnet 4 is attached (adhered) to the inner surface of the U-shaped outer wall 2b.

[0067] The carrier 5 is a formed product made of a synthetic resin or the like, which has a cylindrical structure with a bottom portion, and the carrier 5 supports the lens in the central position, and binds the pre-formed coil 6 onto the bottom surface outwardly so that the coil 6 is mounted thereon. The yoke 2 is integrated by fitting it to the inner periphery of the base 7 which is a rectangular resin formed article, and the whole yoke 2 is further secured by the frame 8 which is a resin formed article.

[0068] The spring members 9a, 9b are fixed by holding their outermost peripheral portions by the frame 8 and the base 7, respectively, and the cutout grooves arranged per 120 on the inner peripheral portion are fitted to the carrier 5 and fixed by thermal caulking or the like.

[0069] The spring member 9b and the base 7 as well as the spring member 9a and the frame 8 are fixed by adhesive and thermal caulking, respectively, and further the cap 10b is attached to the bottom surface of the base 7, and the cap 10a is attached to the upper portion of the frame 8, and the spring member 9b is sandwiched between the base 7 and the cap 10b and the spring member 9a is sandwiched between the frame 8 and the cap 10a, so that they are adhered.

[0070] The lead wire of one of the coils 6 is extended upward passing through the groove provided on the inner peripheral surface of the carrier 5, and soldered to the spring member 9a. The other lead wire is extended downward passing through the groove provided on the bottom surface of the carrier 5, and soldered to the spring member 9b.

[0071] The spring members 9a, 9b are plate springs made of the CuNiSn based copper alloy foil according to the present invention. They have spring properties and elastically energize the lens 3 to the initial position in the optical axis direction. At the same time, they also act as power supply paths to the coil 6. One position on the outer peripheral portion of each of the spring members 9a, 9b projects outward, thereby acting as a power supply terminal.

[0072] The cylindrical magnet 4 is magnetized in the radial (diameter) direction and forms a magnetic path passing through the inner wall 2a, the upper surface portion and the outer wall 2b of the U-shaped yoke 2, and the coil 6 is disposed in the gap between the magnet 4 and the inner wall 2a.

[0073] The spring members 9a, 9b have the same shape, and are attached in the same positional relationship as shown in FIGS. 1 and 2, so that any axial deviation can be suppressed when the carrier 5 moves upward. Since the coil 6 is manufactured by pressure molding after winding, the accuracy of the finished outer diameter of the coil can be improved, thereby allowing the coil to be easily arranged in a predetermined narrow gap. The carrier 5 abuts to the base 7 at the lowest position and abuts to the yoke 2 at the uppermost position, and it will be thus equipped with the abutting mechanisms in the upper and bottom vertical direction, thereby preventing any detachment.

[0074] FIG. 3 shows a sectional view when upwardly moving the carrier 5 having the lens 3 for the autofocus, by applying an electric current to the coil 6. When an electric power is applied to the power supply terminals of the spring members 9a, 9b, the electric current flows through the coil 6, and an upward electromagnetic force acts on the carrier 5. On the other hand, restoring force of two linked spring members 9a, 9b downwardly acts on the carrier 5. Therefore, the distance of upward movement of the carrier 5 will correspond to a position where the electromagnetic force and the restoring force are balanced. This will allow determination of the moving amount of the carrier 5 according to the amount of the electric current applied to the coil 6.

[0075] Since the upper spring member 9a supports the upper surface of the carrier 5 and the lower spring member 9b support the lower surface of the carrier 5, the restoring force will equally work downward on the upper and lower surfaces of the carrier 5, so that any axial displacement of the lens 3 can be suppressed.

[0076] Therefore, for the upward movement of the carrier 5, no guide by a rib or the like is needed and used. Since there is no sliding friction by the guide, an amount of movement of the carrier 5 will be purely controlled by the balance between the electromagnetic force and the restoring force, thereby achieving smooth and accurate movement of the lens 3. This will achieve autofocusing with reduced blurring of the lens.

[0077] In addition, although the magnet 4 has been described as one having the cylindrical shape, the magnet is not limited to this shape, and may be divided into three to four parts and magnetized in the radial direction, which may be fixed by adhering to the inner surface of the outer wall 2b of the yoke 2.

EXAMPLES

[0078] The CuNiSn based copper alloy foil according to the present invention was experimentally produced and its effects were confirmed as described below. However, the description herein is merely for the purpose of illustration and is not intended to be limited thereto.

Production Conditions

[0079] Production of prototype was carried out as follows. Electrolytic copper or oxygen-free copper as a main raw material and nickel (Ni) and tin (Sn) as sub-raw materials were melted in a high-frequency melting furnace in a vacuum or in an argon atmosphere to cast into a copper alloy ingot having a size of 454590 mm and each composition shown in Table 1. Here, depending Inventive Examples or Comparative Examples, 25% MnCu (Mn), 10% FeCu (Fe), 10% CoCu (Co), zinc (Zn), Si, 10% MgCu mother alloy (Mg), sponge titanium (Ti), sponge zirconium (Zr), and the like, were used as further sub-raw materials, so as to form each component shown in Table 1.

[0080] Each ingot as described above was subjected to homogenization annealing by maintaining the ingot at 900 C. for 3 h, followed by hot rolling at 800 C. with a degree of working of 50%, followed by cold rolling with a working degree of 90%, and followed by a solution treatment for heating the ingot at 1800 C. for 5 minutes. Each sample was then rapidly cooled by placing the sample in a water tank. Cold rolling 2 was then performed, where the rolling was carried out to a foil thickness of from 0.07 to 0.27 mm with a rolling reduction rate of from 88 to 97%. An aging treatment was then performed by heating the sample at 400 C. for 2 hours. Here, the temperature of the aging treatment was selected so as to maximize the tensile strength after the aging treatment.

[0081] After the aging treatment, cold rolling 3 (final cold rolling) was carried out to process the sample from a thickness of 0.14 mm (from 0.07 to 0.27 mm) to the product thickness with a degree of working of from 70% to 79%. In the cold rolling 3, the diameter of the work roll and the final pass rolling reduction rate were varied in each inventive example and comparative example, as shown in Table 1.

[0082] Each prototype thus obtained was evaluated as follows:

Surface Roughness

[0083] A roughness curve having a reference length of 300 m was taken along a direction parallel to the rolling direction of the prototype, and the maximum height roughness Rz was measured from the curve in accordance with JIS B0601 (2013).

Solder Wettability/Solder Adhesion

[0084] A soldering test was carried out using solder of Pb-free solder M705 series from Senju Metal Industry Co., Ltd. In the evaluation of solder wettability, soldering was carried out by the same procedure as the meniscograph method with a solder checker (SAT-2000 available from REHSCA CO., LTD.) and appearance of the soldered portion was observed, in accordance with JIS C60068-2-54. The measurement conditions are as follows. The sample was degreased with acetone as a pretreatment. The sample was then pickled with an aqueous 10 vol % sulfuric acid solution. The solder test temperature was 2455 C. The flux was not specified, but GX 5 available from Asahi Chemical Research Laboratory Co., Ltd. was used. Further, the immersion depth was 2 mm, the immersion time was 10 seconds, the immersion rate was 25 mm/sec, and the width of the sample was 10 mm. For evaluation criteria, each sample was evaluated by visual observation with a stereoscopic microscope at 20 magnitudes, and a sample in which the entire surface of the soldered portion was covered with the solder was evaluated as good (O), and a sample in which a part or all of the soldered portion was not covered with the solder was evaluated as poor (x). Further, in the evaluation of solder adhesion, a peel strength of 1 N or more was evaluated as O, and a peel strength of less than 1 N was evaluated as . The peeling strength was measured by using a CuNiSn based copper alloy foil having a plating layer and a pure copper foil (Alloy No. C1100 defined in JIS H3100 (2012); a foil thickness of from 0.02 mm to 0.05 mm) joined together via a lead-free solder (Sn-3.0 mass % Ag-0.5mass % Cu). The CuNiSn based copper alloy foil was in the form of a strip having a width of 15 mm and a length of 200 mm, the pure copper foil was in the form of a strip having a width of 20 mm and a length of 200 mm. A lead-free solder (a diameter of 0.40.02 mm, a length of 1201 mm) was placed on an area of 30 mm15 mm at each central portion in the long direction so as to be within the above area, and then joined together at a joining temperature of 245 C.5 C. After the joining, the adhesion strength is measured by performing a 180 peeling test at a rate of 100 mm/min. An average value of loads (N) in a section of 40 mm from 30 mm to 70 mm of peeling displacement is determined to be the adhesion strength. An example of measurement results in the solder adhesion strength test is shown in FIG. 4.

[0085] These results are shown in Table 1

TABLE-US-00001 TABLE 1 Final Cold Prototype Rolling Roughness Tensile Final in Strength Component (% by mass) Work Pass Product Rolling Spreading (MPa) in Mn, Ti, Si, Al, Zr, B, Roll Rolling Thick- Parallel of Rolling Zn, Nb, Fe, Co, Si, Diameter Reduction ness Direction Solder Solder Parallel Ni Sn Mg, Cr (mm) Rate (%) (mm) Rz (m) Wetting Adhesion Direction Inventive Example 1 15.0 8.0 60 35 0.04 0.11 1350 Inventive Example 2 15.0 8.0 60 9 0.04 0.96 1200 Inventive Example 3 15.0 8.0 60 30 0.04 0.15 1280 Inventive Example 4 15.0 8.0 60 27 0.04 0.38 1330 Inventive Example 5 15.0 8.0 60 24 0.04 0.52 1220 Inventive Example 6 15.0 8.0 60 21 0.04 0.61 1280 Inventive Example 7 15.0 8.0 60 18 0.04 0.77 1210 Inventive Example 8 15.0 8.0 60 15 0.04 0.82 1350 Inventive Example 9 15.0 8.0 60 12 0.04 0.91 1280 Inventive Example 10 15.0 8.0 30 30 0.02 0.13 1420 Inventive Example 11 15.0 8.0 40 30 0.03 0.18 1360 Inventive Example 12 15.0 8.0 60 30 0.05 0.45 1320 Inventive Example 13 15.0 8.0 100 30 0.06 0.8 1280 Inventive Example 14 15.0 8.0 120 30 0.08 0.9 1250 Inventive Example 15 21.0 5.2 60 30 0.03 0.23 1480 Inventive Example 16 22.0 10.0 60 30 0.02 0.43 1520 Inventive Example 17 14.0 4.0 60 30 0.04 0.22 1100 Inventive Example 18 15.0 8.0 0.2Fe 60 30 0.04 0.39 1380 Inventive Example 19 15.0 8.0 0.1Fe, 0.1Ti 60 30 0.04 0.34 1470 Inventive Example 20 15.0 8.0 0.1B, 0.4Cr, 0.4Ag 60 30 0.04 0.28 1510 Inventive Example 21 15.0 8.0 0.1Mo, 0.05Si, 0.1Co 60 30 0.04 0.26 1500 Inventive Example 22 15.0 8.0 0.1Mg, 0.1P 60 30 0.04 0.22 1460 Inventive Example 23 15.0 8.0 0.1Mn, 0.1Ni, 0.2Zr 60 30 0.04 0.31 1450 Inventive Example 24 15.0 8.0 0.2Al, 0.2Zn 60 30 0.04 0.28 1370 Inventive Example 25 15.0 8.0 0.1Nb, 0.1Cr 60 30 0.04 0.31 1380 Comparative Example 1 15.0 8.0 60 5 0.04 1.2 1350 Comparative Example 2 15.0 8.0 60 40 0.04 0.08 1340 Comparative Example 3 15.0 8.0 20 30 0.04 0.08 1350 Comparative Example 4 15.0 8.0 140 30 0.04 1.2 1350 Comparative Example 5 10.0 3.0 60 30 0.04 0.15 960 Comparative Example 6 24.0 5.0 Cracks Occurred in Hot Rolling Comparative Example 7 15.0 12.0 0.4Mg, 0.5Zr, 0.2Si Cracks Occurred in Hot Rolling Comparative Example 8 15.0 12.0 0.3Fe, 0.4Nb, 0.4Zn Cracks Occurred in Hot Rolling

[0086] As can be seen from Table 1, in Inventive Examples 1 to 25, each final pass was set to a predetermined rolling reduction rate using the work roll having a predetermined diameter in the final cold rolling, so that the maximum height roughness Rz in the direction parallel to the rolling direction (the rolling parallel direction) was from 0.1 to 1.0 m, resulting in good spreading of solder wetting and good solder adhesion.

[0087] On the other hand, in Comparative Example 1, the maximum height roughness Rz in the rolling parallel direction was higher due to the decreased rolling reduction rate of the final pass, so that the spreading of solder wetting was poor. In Comparative Example 2, the rolling reduction rate was higher, so that the maximum height roughness Rz in the rolling parallel direction was decreased and the solder adhesion was deteriorated.

[0088] In Comparative Example 3, the diameter of the work roll used in the final cold rolling was smaller, so that the maximum height roughness Rz in the rolling parallel direction was decreased and the solder adhesion was poor. In Comparative Example 4, the work roll diameter was too large, so that the maximum height roughness Rz in the rolling parallel direction was increased, and the solder wettability was deteriorated.

[0089] In Comparative Example 5, the contents of Sn and Ni were lower, so that the tensile strength was less than 1100 MPa.

[0090] In Comparative Examples 6, 7 and 8, cracks occurred in the hot rolling due to higher contents of Sn, Ni or sub-raw materials, so that prototypes could not be produced.

[0091] In view of the foregoing, it was found that the present invention could improve the solder wettability and solder adhesion strength of the thinner CuNiSn based copper alloy foil having a foil thickness of 0.1 mm or less.

DESCRIPTION OF REFERENCE NUMERALS

[0092] 1 auto focus camera module [0093] 2 york [0094] 3 lens [0095] 4 magnet [0096] 5 carrier [0097] 6 coil [0098] 7 base [0099] 8 frame [0100] 9a upper spring member [0101] 9b lower spring member [0102] 10a, 10b cap