JP6391618B2 - Titanium copper foil and manufacturing method thereof - Google Patents

Description

  The present invention relates to a Cu-Ti alloy foil having excellent strength suitable for use in a conductive spring material such as an autofocus camera module.

  An electronic component called an autofocus camera module is used for a camera lens portion of a cellular phone. The autofocus function of the mobile phone camera is based on the electromagnetic force generated by moving the lens in a certain direction and passing a current through the coil wound around the lens by the spring force of the material used for the autofocus camera module. The lens is moved in the direction opposite to the direction in which the spring force of the material works. The camera lens is driven by such a mechanism, and the autofocus function is exhibited.

  For an autofocus camera module, a Cu—Ni—Sn-based copper alloy foil having a foil thickness of 0.1 mm or less and a tensile strength of 1100 MPa or more or a 0.2% proof stress has been used. However, due to the recent cost reduction request, titanium copper foil having a relatively low material price than Cu—Ni—Sn based copper alloys has come to be used, and its demand is increasing.

  Since the Cu—Ti alloy contains Ti, which is an extremely active element, a strong oxide film is generated in the aging treatment in the final process. Since such a strong oxide film significantly reduces solder wettability, an aging treatment is performed on a relatively thick Cu—Ti alloy such as a titanium copper plate or a strip as described in Patent Document 1, for example. Later, chemical polishing (pickling) and mechanical polishing are generally performed to remove the oxide film.

To remove the oxide film with the Cu—Ti alloy, first, chemical polishing is performed. Since the oxide film of Cu-Ti alloy containing titanium oxide is very stable against acid, chemical polishing is highly corrosive chemical such as a solution of hydrogen peroxide in hydrofluoric acid or sulfuric acid. It is necessary to use a polishing liquid.
However, when a chemical polishing solution having such a strong corrosive force is used, not only the oxide film but also the non-oxidized portion may be corroded, and uneven unevenness or discoloration occurs on the surface after chemical polishing. There is a fear. Further, the corrosion does not proceed uniformly, and the oxide film may remain locally. Therefore, in order to remove surface irregularities, discoloration, and residual oxide film, mechanical polishing is performed using, for example, a buff after the chemical polishing.
After mechanical polishing, the final surface treatment is a rust prevention treatment to produce a plate / strip product. An aqueous solution of benzotriazole (BTA) is used for the rust-proofing treatment of the titanium copper foil, similar to the one used for general copper and copper alloy plates and strips.

Japanese Patent No. 4068413

  By the way, in the case of a titanium copper foil having a relatively thin thickness, unlike the case of a titanium copper plate / strip, it is difficult to perform mechanical polishing using a buff. There are two reasons for this, the first is related to foil passing through the mechanical polishing line, and the second is related to thickness control in the mechanical polishing line.

  Regarding the foil passing through the mechanical polishing line, which is the first reason, when a buff is used, the buff is caught on the titanium copper foil as the baffle rotates, and the titanium copper foil may break starting from the caught point. . In the buffing, the surface of the titanium copper foil is polished by rotating around the central axis of a cylindrical buffule. The bafrol is a resin in which abrasive grains (SiC and other abrasive grains) are dispersed and fixed to a sponge-like organic fiber. The lump of resin is caught by the edge of the titanium copper foil where it is uneven, and the strength of the titanium copper foil It breaks when a tension exceeding is applied.

  Regarding the plate thickness control in the mechanical polishing line, which is the second reason, the cylindrical baffle is loaded with a rolling load to polish, and the titanium copper foil has a line passing through it. Tension is applied. This rolling load and tension both have a more or less periodic vibration component, and this vibration is called chattering. Depending on the chattering period, each vibration may resonate. When the resonance is large, a tatami pattern appears on the polished surface to be mechanically polished by chattering. A pattern generated by chattering is called a chatter mark. This indicates that the amount of polishing differs according to the pattern, in other words, the amount of polishing of the titanium copper foil varies. Here, in the case of titanium copper foil, since the thickness is smaller than that of the titanium copper plate / strip, the influence of the variation in the polishing amount is large. That is, when the titanium copper foil is buffed, the variation in thickness increases, and when this is used as a spring, the variation in spring characteristics increases, which is not preferable.

  Thus, titanium copper foil is difficult to mechanically polish using a buff etc. compared to titanium copper plate / strip, and effective removal of oxide film by chemical polishing and mechanical polishing like titanium copper plate / strip is effective. Have difficulty.

  In order to cope with this, it is conceivable to suppress the formation of an oxide film by heat treatment. However, if the generation of an oxide film during heat treatment is suppressed, the desired discoloration resistance cannot be obtained in the rust prevention treatment performed in the final surface treatment. This is because oxygen is involved as a reactive species in a chemical reaction in which a rust-preventing film is formed by benzotriazole (BTA), and a sound rust-preventing film is not generated without oxygen. When buffing is performed, the outermost surface generates heat due to scratching of the abrasive grains, and the temperature rises to form an oxide film. Thanks to this oxide film, a rust-proofing treatment with benzotriazole (BTA) produces a sound rust-proof coating and provides the desired discoloration resistance. Therefore, from the viewpoint of discoloration resistance, it can be said that an oxide film should be actively generated in the heat treatment.

  On the other hand, when the formation of an oxide film is promoted in the heat treatment, as described above, the solderability required as a conductive spring material for an autofocus camera module or the like is significantly deteriorated. In particular, titanium copper contains titanium, which is an active and easily oxidizable element, so it cannot be said that the solderability is superior to other copper and copper alloys. As for the solder itself, lead-free solder has been widely used in recent years for health reasons, and lead-free solder is inferior in solderability compared to conventional lead-containing solder.

  Therefore, it is difficult to perform mechanical polishing to remove an oxide film generated by heat treatment with a titanium copper foil having a relatively thin thickness, thereby achieving both required solderability and discoloration resistance in the prior art. I couldn't.

  An object of the present invention is to solve such a problem, and has an excellent balance between discoloration resistance and solderability, and is used as a conductive spring material used in electronic device parts such as an autofocus camera module. It aims at providing the titanium copper foil which can be used suitably, and its manufacturing method.

The inventor, even if the surface oxide film is a thin titanium copper foil, by providing a predetermined oxygen-concentrated layer, a sound rust preventive film is produced in the rust preventive treatment, and good discoloration resistance is obtained. In addition, it has been newly found that such an oxygen enriched layer does not deteriorate the solderability.
And, such an oxygen-concentrated layer is subjected to hot rolling, first cold rolling, solution treatment and second cold rolling in the same manner as in the past, followed by aging treatment under predetermined conditions, The knowledge that it can produce | generate by performing the oxidation process of a predetermined condition after the aging treatment was acquired.

Based on such knowledge, the titanium copper foil of the present invention contains 1.5 to 5.0% by mass of Ti, the balance is made of copper and unavoidable impurities, and the oxygen concentration of the surface layer measured by XPS analysis is less than 33 atomic%, the surface layer, the oxygen concentration measured by XPS analysis is less than 5 atomic% or more 33 atomic%, and has an oxygen enriched layer is less than 1/2 of the maximum oxygen concentration, The oxygen-enriched layer has a thickness of 0.2 nm to 2.0 nm.

  Here, the thickness of the titanium copper foil is preferably 0.1 mm or less.

  The titanium copper foil preferably has a tensile strength in the direction parallel to the rolling direction of 1100 MPa or more.

  The titanium copper foil is composed of one or more elements selected from Al, Ag, B, Co, Fe, Mg, Mn, Mo, Ni, P, Si, Cr, and Zr in a total amount of 0 to 1. Further, it may be contained in an amount of 0.0% by mass.

Moreover, the manufacturing method of the titanium copper foil of this invention is a method of manufacturing one of the titanium copper foils mentioned above , Comprising : Ti is contained by 1.5-5.0 mass%, and the remainder is copper and unavoidable An ingot made of impurities is cast, and the ingot is heated for 2 hours to 20 hours at a temperature of 200 to 300 ° C by hot rolling, first cold rolling, solution treatment, second cold rolling, and 200 to 300 ° C. An aging treatment is performed in this order, and after the aging treatment, an oxidation treatment in which heating is performed at a temperature of 150 to 200 ° C. for 5 hours to 10 hours and an antirust treatment are performed in this order.

  Moreover, in this manufacturing method, it is preferable that the reduction rate in the second cold rolling is 55% or more.

  Moreover, in this manufacturing method, after the oxidation treatment, third cold rolling with a reduction rate of 35% or more can be performed.

  According to the present invention, it is possible to provide a titanium copper foil in which discoloration resistance and solderability are achieved at a high level by providing a predetermined oxygen-concentrated layer on the surface layer. Such a titanium copper foil can be suitably used as a conductive spring material used for electronic device parts such as an autofocus camera module.

It is a graph which shows typically the oxygen profile of the surface layer obtained by XPS analysis in titanium copper foil of one embodiment of the present invention. It is a graph which shows typically the oxygen profile of the surface layer obtained by XPS analysis in titanium copper foil of other embodiments of the present invention.

Hereinafter, embodiments of the present invention will be described in detail.
The titanium copper foil of one embodiment of the present invention contains 1.5 to 5.0% by mass of Ti, the balance is made of copper and unavoidable impurities, and the surface layer is oxygen measured by XPS analysis. Having an oxygen-enriched layer having a concentration of 5 atomic% or more and less than 33 atomic% and 1/2 or more of the maximum oxygen concentration, wherein the oxygen-enriched layer has a thickness of 0.2 nm to 2.0 nm is there.

(Ti concentration)
In the titanium copper foil which concerns on this invention, Ti density | concentration shall be 1.5-5.0 mass%. Titanium copper increases strength and electrical conductivity by dissolving Ti in a Cu matrix by solution treatment and dispersing fine precipitates in the alloy by aging treatment.
If the Ti concentration is less than 1.5% by mass, precipitation of precipitates is insufficient and desired strength cannot be obtained. If the Ti concentration exceeds 5.0% by mass, the workability deteriorates and the material is easily cracked during rolling. Considering the balance between strength and workability, the preferable Ti concentration is 2.9 to 3.5% by mass.

(Other additive elements)
In the titanium copper foil according to the present invention, the total amount of one or more of Al, Ag, B, Co, Fe, Mg, Mn, Mo, Ni, P, Si, Cr and Zr is 0 to 1.0% by mass. By containing, strength can be further improved. The total content of these elements is 0, that is, these elements may not be included. The reason why the upper limit of the total content of these elements is set to 1.0% by mass is that if it exceeds 1.0% by mass, the workability deteriorates and the material is easily cracked during hot rolling.

(Tensile strength)
The tensile strength required for a titanium copper foil suitable as a conductive spring material for an autofocus camera module is 1100 MPa or more, and more preferably 1300 MPa or more. In the present invention, the tensile strength in a direction parallel to the rolling direction of the titanium copper foil is measured, and the tensile strength is measured in accordance with JIS Z 2241 (metal material tensile test method).

(Oxygen enriched layer)
The titanium copper foil of the present invention has an oxygen concentrated layer on the surface layer, and the thickness of the oxygen concentrated layer is 0.2 to 2.0 nm.
Here, the oxygen-enriched layer means that the oxygen concentration measured by XPS analysis (X-ray photoelectron spectroscopy) is 5 atomic% or more and less than 33 atomic%, and the maximum of the oxygen-enriched layer in the depth direction. A layer having an oxygen concentration of 1/2 or more. Due to the presence of such an oxygen-enriched layer on the surface layer, it is possible to improve the discoloration resistance by the rust prevention treatment while ensuring the required solderability.

  When the thickness of the oxygen-concentrated layer is less than 0.2 nm, or when the oxygen concentration of the oxygen-concentrated layer is too low, such as less than 5 atomic%, a sound rust-proof coating is not generated in the rust-proofing process, and the resistance to discoloration There is concern about deterioration. If the thickness of the oxygen-concentrated layer exceeds 2.0 nm, solderability may be deteriorated. In the portion where the oxygen concentration exceeds 33%, solderability deteriorates due to the formation of an oxide film.

In the present invention, the structure of the titanium copper foil surface layer is defined from the profile of the oxygen concentration of the surface layer of the titanium copper foil obtained by XPS analysis. In the surface layer of the titanium copper foil, there are at least two phases of an oxygen-concentrated layer and a parent phase from the surface to the inside, and in some cases, an oxide film (CuO, Cu ₂ O), an oxygen-concentrated layer, and There may be three phases of the mother phase.

In each of FIGS. 1 and 2, different in Ruchi Tan copper foil shows a profile of the oxygen concentration of the surface layer obtained by XPS analysis schematically. In the graphs of FIGS. 1 and 2, the horizontal axis represents the sputtering depth, and the vertical axis represents the oxygen concentration. The position where the sputtering depth is 0 nm indicates the surface of the titanium copper foil. As shown in FIGS. 1 and 2, titanium copper foil used as a conductive spring material for an autofocus module or the like has a low oxygen concentration in the surface layer, so an oxide film (CuO, Cu ₂ O), an oxygen concentrated layer, a rust preventive film A profile that clearly recognizes and distinguishes the layers and matrix is not obtained, but a curve with a peak in oxygen concentration is obtained. In many cases, the peak of the oxygen concentration exists in a site located inside away from the surface, but there is a case where the peak exists not on the inside but on the surface, that is, at a sputtering depth of 0 nm in FIGS. . In any case, there are places where the oxygen concentration is maximum in the surface layer of the titanium copper foil, and here, this oxygen concentration is referred to as the maximum value of the oxygen concentration of the surface layer existing on the surface side of the parent phase.

The maximum value of the oxygen concentration in the surface layer is generally determined by the composition of the oxide. For example, when the oxide is CuO, the maximum value of the oxygen concentration of the surface layer is 50 atomic%, and when the oxide is Cu ₂ O, the maximum value of the oxygen concentration of the surface layer is 33 atomic%. . However, when the surface of a titanium copper foil for a conductive spring material such as an autofocus module is analyzed by XPS analysis, various values of oxygen concentration are obtained. This is also considered to be due to the fact that an oxide containing Ti or the like as well as Cu may be present. In the present invention, based on the composition of Cu ₂ O as an oxide, if there is a range in which oxygen at a concentration of 33 atomic% or more is detected even if the value is inconsistent with the stoichiometric composition, all of them are oxidized. Considered a membrane. This is because the region where the oxygen concentration is 33 atomic% or more adversely affects discoloration resistance and solderability. Further, a range where the oxygen concentration is less than 33% is regarded as an oxygen-enriched layer or a mother phase.

In the present invention, the oxide film thickness and the oxygen-concentrated layer thickness are defined for the case where the maximum value of the oxygen concentration of the surface layer is 33 atomic% or more and the case where it is less than 33 atomic%.
That is, when the maximum value of the oxygen concentration of the surface layer is 33 atomic% or more, as shown in FIG. 1, the oxygen concentration becomes 33 atomic% after passing the maximum value from the surface (sputtering depth is 0 nm). The distance to the sputtering depth is the thickness of the oxide film. The distance from the sputtering depth at which the oxygen concentration is 33 atomic% to the sputtering depth at which the oxygen concentration is ½ of the maximum oxygen concentration of the oxygen concentrated layer is defined as the thickness of the oxygen concentrated layer.
Alternatively, when the maximum value of the oxygen concentration in the surface layer is less than 33 atomic%, as shown in FIG. 2, the oxygen concentration is the maximum oxygen concentration (max value in FIG. 2) from the surface (sputtering depth is 0 nm). The distance to the sputtering depth, which is 1/2 of the value (1 / 2max in FIG. 2), is the thickness of the oxygen-enriched layer. In this case, it can be considered that the oxide film is not included.

  Here, in the present invention, Cu, Ti, C and O are targeted as analytical elements in XPS analysis, and the O concentration is obtained from these four elements. Cu and Ti are main components of the titanium copper foil, and C is a main component of the rust preventive coating. Elements other than these four elements are not considered due to the fact that the detected amount is very small.

The sputtering rate in the XPS analysis is 1.0 to 3.0 nm / min in terms of SiO ₂ , and the sputtering is performed once for 0.1 minute, and the component analysis is performed for each sputtering. The O concentration profile is affected by this sputtering rate. Therefore, in some cases, if the sputtering rate is analyzed as 1.0 nm / min, it is included in the scope of the present invention, and if the sputtering rate is analyzed as 3.0 nm / min, it may not be included in the scope of the present invention. Even in such a case, the oxygen concentration layer thickness and the oxide film thickness within the range of the present invention are measured by any setting within the range of 1.0 to 3.0 nm / min. Are included in the present invention. The same applies to the sputtering time. In the present invention, the sputtering time is set to 0.1 minutes.

In XPS analysis, information on whether or not the compound is present, for example, information on whether or not CuO or Cu ₂ O is present, from the energy shift amount (chemical shift) at the photoelectron peak position. Can be obtained. Titanium copper foil used as a conductive spring material for autofocus modules and the like has a low surface layer oxygen concentration and a large error, so there is a discrepancy between the identification based on the energy shift amount (chemical shift) and the composition obtained from the oxygen concentration profile. Things can happen. However, even if there is such a contradiction between the two, the present invention adopts the above definition based on the oxygen concentration profile, and ignores the result of identification based on the energy shift amount (chemical shift). In addition, depending on the setting conditions of the XPS analysis, it is conceivable that measurement results included in the scope of the present invention and measurement results not included in the scope of the present invention may be obtained. In such a case, they are included in the scope of the present invention. . In other words, titanium copper foil that is not included in the scope of the present invention by XPS analysis under any conditions is excluded from the present invention. In addition, analysis methods other than XPS analysis, for example, results such as AES analysis (Auger analysis) and GDS analysis (glow discharge emission spectroscopy) should be considered when examining whether or not they are included in the technical scope. Absent.

(Oxide film)
The surface oxide film is preferably as thin as possible or absent. The oxide film may be present on the surface side from the depth position where the oxygen concentration measured by the XPS analysis is 33 atomic%. If the thickness of the oxide film is thick, the solderability is deteriorated.

(Thickness of copper foil)
In one embodiment of the titanium copper foil of the present invention, the foil thickness is 0.1 mm or less, in a typical embodiment the foil thickness is 0.018 mm to 0.08 mm, and in a more typical embodiment the foil The thickness is 0.02 mm to 0.05 mm.

(Production method)
In order to manufacture the titanium copper foil as described above, first, raw materials such as electrolytic copper and Ti are melted in a melting furnace to obtain a molten metal having a desired composition. Then, this molten metal is cast into an ingot. In order to prevent oxidative wear of titanium, melting and casting are preferably performed in a vacuum or in an inert gas atmosphere. After that, typically, the ingot is typically subjected to hot rolling, first cold rolling, solution treatment, second cold rolling, aging treatment, oxidation treatment, third cold rolling, and rust prevention treatment in this order. Perform and finish to foil with desired thickness and properties.

  The conditions for the hot rolling and the subsequent first cold rolling may be the conventional conditions used in the production of titanium copper, and there are no special requirements here. The solution treatment may be performed under conventional conditions, but can be performed at a temperature of 700 to 1000 ° C. for 5 seconds to 30 minutes, for example.

  In order to obtain the above-mentioned strength, it is preferable to set the reduction ratio of the second cold rolling to 55% or more. More preferably, it is 60% or more, More preferably, it is 65% or more. When the rolling reduction is less than 55%, it becomes difficult to obtain a tensile strength of 1100 MPa or more. The upper limit of the rolling reduction is not particularly defined from the viewpoint of the strength intended by the present invention, but industrially does not exceed 99.8%.

  The heating temperature for the aging treatment is 200 to 300 ° C., and the heating time is 2 to 20 hours. When the heating temperature is less than 200 ° C., it becomes difficult to obtain a tensile strength of 1100 MPa or more. If it exceeds 300 ° C., an oxide film or an oxygen-enriched layer is excessively generated. When the heating time is less than 2 hours or exceeds 20 hours, it becomes difficult to obtain a tensile strength of 1100 MPa or more.

  Further, in order to obtain the oxygen-enriched layer described above, an oxidation treatment is performed after the aging treatment. The oxidation treatment is a temperature and time at which the electrical conductivity and strength are not changed by the heat treatment, and is a temperature and time within a range in which an excessive oxide film and oxygen-enriched layer are not formed. And Specifically, the heating temperature is 150 to 200 ° C., and the heating time is 5 to 10 hours. If the heating temperature or the heating time is below the lower limit of the range, a desired oxygen-concentrated layer cannot be obtained. When the heating temperature or the heating time exceeds the upper limit of the range, an oxygen-enriched layer having an excessive thickness is generated or an oxide film is generated. In the above description, the aging treatment and the oxidation treatment have been described as a two-step heat treatment performed separately and continuously. However, the present invention is not limited to this, and the aging treatment can be performed if a desired oxygen-concentrated layer can be obtained. It is also possible to incorporate an oxidation treatment into the cooling process in the treatment and perform a one-step heat treatment.

The aging treatment described above is preferably performed in a reducing gas mixed with hydrogen in order to suppress the formation of an oxide film or an oxygen-enriched layer. Furthermore, it is effective to set the hydrogen concentration to 50% by volume or more and to set the dew point to −40 ° C. or less. Nitrogen or argon can be used as the inert gas. The pressure of the gas is not limited, but usually a pressure slightly higher than atmospheric pressure can be employed.
In addition, the above-described oxidation treatment is preferably performed in an inert gas in order to appropriately generate an oxygen concentrated layer. Furthermore, it is effective to set the dew point to −30 ° C. or lower and −40 ° C. or higher. Nitrogen or argon can be used as the inert gas. The pressure of the gas is not limited, but usually a pressure slightly higher than atmospheric pressure can be employed.
In addition, when it implements on an industrial scale unlike implementation by test research, hydrogen gas, nitrogen gas, and argon gas inevitably contain a water | moisture content, for example, a dew point is about 0 degreeC. When a copper alloy is heated in a heat treatment furnace using a gas containing moisture as an atmosphere, the copper alloy may be oxidized by the moisture. In addition, hydrogen gas is generally a reducing gas, but even if it is 100% hydrogen gas, the copper alloy may be oxidized by moisture. Therefore, it is necessary to remove the moisture of the atmospheric gas before introducing it into the heat treatment furnace regardless of the type of gas.

  The reduction ratio of the third cold rolling is preferably set to 35% or more. More preferably, it is 40% or more, More preferably, it is 45% or more. When the rolling reduction is less than 35%, it becomes difficult to obtain a tensile strength of 1100 MPa or more. The upper limit of the rolling reduction is not particularly defined from the viewpoint of the intended strength, but does not exceed 99.8% industrially. Note that the third cold rolling can be omitted for applications that do not require such a high strength.

  In general, after heat treatment, pickling or polishing of the surface is performed to remove the oxide film or oxide layer formed on the surface. In the present invention, the surface can be pickled or polished after the heat treatment. However, attention should be paid so that the oxygen-concentrated layer of the titanium copper foil of the present invention does not deviate from the predetermined thickness and oxygen concentration range by such pickling or polishing. Moreover, low temperature annealing may be performed after 2nd cold rolling, and oxidation treatment may be performed after that. However, in this case, the effect of the present invention is not exhibited unless the conditions for low-temperature annealing and oxidation treatment correspond to the conditions for aging treatment and oxidation treatment described above.

  Regardless of whether the above pickling or polishing is performed or not, a rust prevention treatment is performed after the heat treatment. This rust prevention treatment can be performed under the same conditions as before, and an aqueous solution of benzotriazole (BTA) or the like can be used.

(Use)
Although the titanium copper foil of the present invention is not limited, it can be suitably used as a material for electronic device parts such as switches, connectors, jacks, terminals, and relays, and in particular, electronic device parts such as autofocus camera modules. It can be suitably used as a conductive spring material used in the above.

  Next, the titanium copper foil of the present invention was actually made on a trial basis and its performance was evaluated, which will be described below. However, the description here is for illustrative purposes only and is not intended to be limiting.

  An alloy containing Ti at a predetermined concentration and the balance consisting of copper and inevitable impurities was used as an experimental material, and the oxide film thickness, oxygen concentrated layer thickness, maximum oxygen concentration, solderability and discoloration resistance of this material were investigated. .

<Production conditions>
The prototype was manufactured as follows. First, 2.5 kg of electrolytic copper was melted in a vacuum melting furnace, and Ti was added so as to obtain a predetermined concentration of Ti. This molten metal was cast into a cast iron mold to produce an ingot having a thickness of 30 mm, a width of 60 mm, and a length of 120 mm.
This ingot was heated at 950 ° C. for 3 hours and subjected to hot rolling for rolling to a thickness of 10 mm. Grinding was performed by removing the oxidized scale produced by hot rolling with a grinder. The thickness after this grinding was 9 mm. Next, first cold rolling was performed, and the sheet was rolled to a thickness of 1.5 mm. In the subsequent solution treatment, the sample was placed in an electric furnace heated to 800 ° C. and held for 5 minutes, and then the sample was placed in a water bath and rapidly cooled. Then, second cold rolling was performed, and rolling was performed to a foil thickness of 0.03 mm at a reduction rate of 98%. Thereafter, heating was performed at 280 ° C. for 10 hours to 22 hours as an aging treatment, and further, heating was performed under various conditions as an oxidation treatment. Here, this temperature of the aging treatment was selected so that the tensile strength after aging was maximized. Thereafter, a rust prevention treatment was performed. Here, an aqueous solution of Thiolite C71P1 manufactured by Chiyoda Chemical was used as the rust prevention treatment liquid. The third cold rolling was not performed.
The following evaluations were performed on the samples manufactured as described above.

<Oxide film thickness and oxygen concentration layer>
Cu, Ti, C, and O were analyzed using XPS analysis, and the oxide film thickness, the oxygen-enriched layer thickness, and the maximum oxygen concentration were determined from the concentration profile in the depth direction.
The XPS analysis conditions were as follows.
・ Device: ULVAC-PHI Co., Ltd. 5600MC
・ Achieving vacuum: 2.0 × 10 ^-9 Torr
・ Detection area: 800μφ
・ Ion species: Ar ⁺
・ Acceleration voltage: 3kV
-Sweep area: 4mm x 4mm
Sputtering speed: 1.8 nm / min in terms of SiO ₂ Sputtering time: 0.1 minute Frequency of component analysis: one analysis per sputtering

<Solderability>
A soldering test was performed using each of Pb solder and Cu-Sn solder. The wet ones were judged as ◯, and the ones with repelling were judged as ×.
In accordance with JIS C0053 (1996), soldering was performed by a solder checker (SAT-5000 manufactured by Reska Co.) in the same procedure as the meniscograph method, and the appearance of the soldered portion was observed. The measurement conditions are as follows. The sample was degreased using acetone as a pretreatment. Next, it pickled using 10 vol% sulfuric acid aqueous solution. As the solder, 60% Pb-40% Sn was used as the Pb-based solder, and Sn-3Ag-0.5Cu was used as the Cu-Sn-based solder. The test temperature for Pb solder was 235 ° C., and the test temperature for Cu—Sn solder was 250 ° C. GX5 manufactured by Asahi Chemical Laboratory was used for the flux. The immersion depth was 5 mm, the immersion time was 10 seconds, the immersion speed was 15 mm / second, and the sample width was 10 mm. The evaluation criteria are a visual observation with a 20-fold stereo microscope, and the soldering part that is covered with solder is judged as good (O), and there is a part of the soldering part or the whole surface where the solder repels. The one where the background of the titanium copper foil was visible was regarded as defective (x).

<Discoloration resistance>
A discoloration test was conducted in a hot and humid environment containing hydrogen sulfide. Those that did not change color were judged as ◯, and those that changed color as x.
Cut into a strip-shaped test piece with a width of 20 mm and a length of 50 mm, degreased with acetone as a pretreatment of the sample, and then exposed to a hydrogen sulfide atmosphere of 3 ppm hydrogen sulfide, 40 ° C., 50% RH for 20 minutes. The degree of discoloration was visually evaluated. Here, titanium copper foil whose surface was polished with # 4000 emery paper was used as a reference, and in the same manner as above, the one that did not change color was marked with ◯, and the one that changed color more strongly was marked with ×.
These evaluation results are shown in Tables 1 and 2 together with predetermined manufacturing conditions.

Inventive Examples 1 to 26, which are within the scope of the present invention, were excellent in both solderability and discoloration resistance.
Comparative Examples 1 to 4 were inferior in discoloration resistance because the oxidation treatment conditions deviated from the lower limit of the preferred range. In Comparative Examples 5 to 11, the aging treatment or oxidation treatment conditions deviated from the upper limit of the preferred range, and the solderability was inferior. In Comparative Example 12, the Ti component was outside the lower limit and the tensile strength was low. In Comparative Examples 13 to 14, the Ti component or the subcomponent exceeded the upper limit, and cracking occurred and could not be processed.

Claims (5)

Ti is contained at 1.5 to 5.0% by mass, the balance is made of copper and inevitable impurities, the oxygen concentration of the surface layer measured by XPS analysis is less than 33 atomic%, and the surface layer was measured by XPS analysis. An oxygen concentration layer having an oxygen concentration of 5 atomic% or more and less than 33 atomic% and 1/2 or more of the maximum oxygen concentration, and the thickness of the oxygen concentration layer is 0.2 nm to 2.0 nm. Titanium copper foil.   The titanium copper foil according to claim 1, wherein the foil thickness is 0.1 mm or less.   The titanium copper foil according to claim 1 or 2, wherein the tensile strength in a direction parallel to the rolling direction is 1100 MPa or more.   The element further contains one or more elements selected from Al, Ag, B, Co, Fe, Mg, Mn, Mo, Ni, P, Si, Cr, and Zr in a total amount of 0 to 1.0% by mass. The titanium copper foil as described in any one of 1-3. Casting an ingot containing Ti in an amount of 1.5 to 5.0% by mass and copper and inevitable impurities, hot rolling, first cold rolling, solution treatment, second Cold rolling and an aging treatment in which heating is performed at a temperature of 200 to 300 ° C. for 2 hours to 20 hours are performed in this order, and after the aging treatment, oxidation is performed at a temperature of 150 to 200 ° C. for 5 hours to 10 hours. The manufacturing method of the titanium copper foil as described in any one of Claims 1-4 including performing a process and a rust prevention process in this order.