Foil material made of copper-silver alloy, and method for producing foil material made of copper-silver alloy

Abstract

This foil material is made of a copper-silver alloy containing 10-20 mass % of silver, with the balance being copper and unavoidable impurities. The tensile strength of the foil material in the direction perpendicular to the rolling direction is greater than 1250 MPa. The electrical conductivity of the foil material is 50% IACS or more. The Vickers hardness of the foil material in the direction perpendicular to the rolling direction is 300 HV or more. The shear zone area ratio of the foil material in a cross-section viewed from the direction perpendicular to the rolling direction is within the range of 40-70%.

Description

Foil material made of copper-silver alloy, method for manufacturing foil material made of copper-silver alloy

[0001] The present invention relates to a foil material made of a copper-silver alloy and a method for manufacturing the same.

[0002] Probe pins for semiconductor inspection are used for the electrical inspection of semiconductor wafers. In recent years, due to the high performance of electronic devices, the densification of various circuits used in them has been promoted. In addition, in the inspection of highly densified semiconductor wafers, probe pins for semiconductor inspection that can be arranged with a small diameter and a narrow pitch are used. In recent years, in wafer inspection, a probe card called a MEMS type probe card is used, and probe pins formed from a foil material are used from the viewpoints of the number of probes, the freedom of shape, and dimensional accuracy. High strength and high conductivity are required for these probe pins, and performance that can withstand photolithography, laser processing, etc. is also required.

[0003] Patent Document 1 describes a copper alloy plate material containing 6 to 13% by mass of silver, having a tensile strength of 1000 to 1250 MPa, and a conductivity of 60 to 90% IACS. The copper alloy plate material of Patent Document 1 is manufactured by casting an alloy material containing a predetermined amount of silver to obtain an ingot, and then performing a first cold rolling treatment, a solution treatment, a second cold rolling treatment, an aging treatment, and a third cold rolling treatment in sequence.

[0004] International Publication No. 2019 / 031612

[0005] However, since MEMS probes formed from a foil material are used continuously, for example, when a copper alloy foil material manufactured by the method described in Patent Document 1 is formed and adopted, if the tensile strength is low, it is necessary to frequently replace the semiconductor inspection probe due to wear, and the inspection cost tends to increase. Thus, when the copper alloy foil material described in Patent Document 1 is adopted for a semiconductor inspection probe, there is room for consideration regarding the tensile strength, Vickers hardness, and conductivity required for the foil material.

[0006] The main object of the present invention is to provide a foil material made of a copper-silver alloy and a method for manufacturing the same, which are excellent in tensile strength, Vickers hardness, and conductivity required for a foil material that can be used for a semiconductor inspection probe.

[0007] To solve the above problems, according to one aspect of the present invention, a copper-silver alloy foil material is provided, which contains 10 to 20% by mass of silver, with the remainder being copper and unavoidable impurities, wherein the tensile strength in the direction perpendicular to rolling is greater than 1250 MPa, the electrical conductivity is 50% IACS or more, the Vickers hardness in the direction perpendicular to rolling is 300 HV or more, and the shear band area ratio in the cross section viewed from the direction perpendicular to rolling is in the range of 40 to 70%.

[0008] To solve the above problems, according to one aspect of the present invention, a method for manufacturing a copper-silver alloy foil is provided, comprising the steps of: preparing a copper-silver alloy manufactured by a continuous casting method, containing 10 to 20% by mass of silver, with the remainder being copper and unavoidable impurities; and subjecting the copper-silver alloy to a rolling treatment, wherein the foil material after the rolling treatment has a tensile strength of more than 1250 MPa in the direction perpendicular to the rolling, an electrical conductivity of 50% IACS or more, a Vickers hardness of 300 HV or more in the direction perpendicular to the rolling, and a shear band area ratio in the cross-section viewed from the direction perpendicular to the rolling within the range of 40 to 70%.

[0009] According to the present invention, it is possible to provide a copper-silver alloy foil material that is excellent in tensile strength, Vickers hardness, and conductivity required for foil materials, as well as a method for manufacturing the same.

[0010] Figure 1 is a diagram illustrating the rolling direction, the direction perpendicular to rolling, and the direction normal to the rolling surface. Figure 2 is a flowchart of the method for manufacturing the copper-silver alloy foil material of the present invention.

[0011] The following describes a copper-silver alloy foil material (hereinafter also simply referred to as "foil material") and a method for manufacturing the same according to one embodiment of the present invention. However, the foil material and its manufacturing method according to the present invention are not limited to the embodiments shown below. In this specification, the "~" indicating a numerical range includes both an upper and lower limit.

[0012] (Composition of Foil Material) As shown in Figure 1, in the following description, the rolling direction of the foil material 10 will be referred to as RD (rolling direction), the direction perpendicular to rolling as TD (transverse direction), and the direction normal to the rolling surface as ND (normal direction). Note that RD and TD can be determined by the presence or absence of shear bands when observing the cross-section.

[0013] The foil material 10 of this embodiment is manufactured by rolling a copper-silver alloy. The copper-silver alloy is an alloy containing silver, with the remainder being copper and unavoidable impurities. Examples of unavoidable impurities include tin, beryllium, zinc, nickel, magnesium, aluminum, titanium, zirconium, indium, silicon, and phosphorus. There may be one type of unavoidable impurity or two or more types. The silver content is appropriately selected according to the desired properties of the foil material 10, but is in the range of 10 to 20% by mass, and more preferably in the range of 13 to 17% by mass. If the silver content is within this range, the conductivity described later can be 50% IACS or higher.

[0014] The thickness of the foil material is not particularly limited, but in this embodiment, it is in the range of 0.01 to 0.20 mm. If the thickness of the foil material 10 is within this range, it can be used in a semiconductor inspection probe. The width and length of the foil material 10 are not particularly limited.

[0015] The tensile strength of the foil material 10 in the direction perpendicular to the rolling direction (TD direction) is greater than 1250 MPa, and preferably 1300 MPa or more. If the tensile strength in the direction perpendicular to the rolling direction (TD direction) is within the above range, the desired durability can be achieved when used in a semiconductor inspection probe. In this embodiment, the tensile strength is measured using three strip-shaped test pieces in accordance with JIS Z2241:2011, and the average value of the measurements obtained from the three test pieces is taken as the tensile strength.

[0016] The conductivity of the foil material 10 is 50% IACS or higher, preferably 55% IACS or higher. The upper limit of the conductivity is not particularly limited, but is approximately 85% IACS. If the conductivity of the foil material 10 is within the above range, it is possible to appropriately determine whether or not current is flowing when used in a semiconductor inspection probe. The method for measuring conductivity is not particularly limited. In this embodiment, conductivity can be measured by the double-bridge method. Specifically, the electrical resistance of the foil material 10 is measured indoors, and the conductivity is calculated. The distance between voltage terminals is 100 mm.

[0017] The Vickers hardness of the foil material 10 in the direction perpendicular to the rolling direction (TD direction) is 300 HV or higher. If the Vickers hardness in the direction perpendicular to the rolling direction (TD direction) is within the above range, the desired durability can be achieved when used in a semiconductor inspection probe. In this embodiment, the Vickers hardness is measured in accordance with JIS Z 2244:2009.

[0018] The shear band area ratio in the cross-section of the foil material 10 viewed from the direction perpendicular to the rolling direction (TD direction) is in the range of 40 to 70%, and preferably in the range of 45 to 65%. If the shear band area ratio exceeds 70%, the processability deteriorates, and the possibility of fracture during processing and the occurrence of pinhole defects increases. On the other hand, if the shear band area ratio is less than 40%, the required tensile strength and hardness cannot be sufficiently obtained, and wear will be accelerated when used in semiconductor inspection probes. If the shear band area ratio is within the above range, the foil material 10 will have the desired resistance and Vickers hardness, and the processability and bending strength will not decrease too much. In this embodiment, the shear band area ratio is determined as follows. In this embodiment, the Confidence Index (CI) value of EBSD measurement was used as an index for shear bands. The CI value takes a value of 0 to 1. By using the CI value, the quality of crystallinity at the observation point can be evaluated, and the CI value will be low in areas where deformation is concentrated, such as shear bands. In this embodiment, if the CI value of a measurement point is 0.1 or less, it is determined that a shear band has formed at that measurement point. EBSD measurement is performed over the entire measurement range, and the total area of ​​the portion where the CI value is 0.1 or less (total area S2 (μm²)) is calculated. ２)) is determined. Then, the area S1 (μm) of the measurement range where the EBSD measurement will be performed is determined. ２ Total area S2 (μm²) ２ The ratio (S2 / S1) of the portion with a CI value of 0.1 or less is referred to as the "total area ratio of the portion with a CI value of 0.1 or less" or the "shear band area ratio". The total area ratio (S2 / S1) of the portion with a CI value of less than 0.1 is in the range of 0 to 100%. If no shear bands exist within the measurement range, the total area ratio is 0%, and if shear bands exist throughout the entire metal structure within the measurement range, it is 100%. In this embodiment, an EBSD device (DigiView 5; AMETEK) is used, and analysis is performed using analysis software (OIM Analysis; AMETEK). In EBSD measurement, the measurement range is set to the area inside the top 10% of the surface, and the measurement is performed with a step interval of 0.05 μm or 0.025 μm. The EBSD data is analyzed with image analysis software to obtain the CI value, and the area ratio of the shear band is evaluated (calculation of the total area ratio of the portion with a CI value of less than 0.1).

[0019] (Method for manufacturing foil material) Next, the method for manufacturing the foil material 10 will be described. Figure 2 is a flowchart of the method for manufacturing the copper-silver alloy foil material 10 of the present invention.

[0020] As shown in Figure 2, the present invention provides a method for manufacturing a copper-silver alloy foil, comprising the steps of: preparing a copper-silver alloy manufactured by a continuous casting method (S110); applying a rolling treatment (S120); applying an annealing treatment (S130); and applying a rolling treatment again (S140).

[0021] In the step of preparing the copper-silver alloy (S110), a copper-silver alloy having a predetermined composition is prepared by continuous casting. In this embodiment, the copper-silver alloy contains 10 to 20% by mass of silver, with the remainder being copper and unavoidable impurities. In this embodiment, the conductivity is set to 50% IACS or higher by including silver in the range of 10 to 20% by mass.

[0022] In this embodiment, a copper-silver alloy is formed by a continuous casting method. Here, "continuous casting method" is a method of obtaining a long, continuous casting by gradually drawing out the molten metal while it cools in a mold and solidifies. With continuous casting, the constituent elements of the copper-silver alloy are more easily dispersed uniformly, so the solution treatment process, which consists of a high-temperature heat treatment process and a rapid cooling process, can be omitted. Furthermore, with continuous casting, the microstructure of the copper-silver alloy (such as the grain size that takes into account the characteristics of the final shape of the foil material, and the control of the precipitate layer remaining at the grain boundaries) can be easily controlled during continuous casting. Therefore, by appropriately managing this microstructure control, it is expected that the grain size, which has been reduced in advance, can be maintained until the final shape of the foil material, thereby improving the hardness and strength of the foil material. In addition, if the grain size of the foil material can be reduced by appropriately managing the microstructure, the generation of burrs when cutting the foil material can be suppressed, and an improvement in yield can be expected.

[0023] The thickness of the copper-silver alloy after continuous casting is not particularly limited. The thickness of the copper-silver alloy after continuous casting can be appropriately designed according to the properties required for the finished foil material. The thickness of the copper-silver alloy after continuous casting is in the range of 10 to 50 mm. If the thickness of the copper-silver alloy after casting is less than 10 mm, it may not be possible to achieve the required degree of cold working (reduction), and the necessary hardness may not be obtained. On the other hand, if the thickness of the copper-silver alloy after casting exceeds 50 mm, the processing limit may be reached at a relatively thick stage, and there is a risk of cracking, especially at the edges.

[0024] The casting speed in the continuous casting method is not particularly limited. The casting speed in the continuous casting method can be appropriately designed according to the characteristics of the foil material 10. The casting speed in the continuous casting method is preferably in the range of 1 to 50 mm / min.

[0025] After continuous casting, the copper-silver alloy is subjected to precipitation hardening heat treatment. In this process, solutes dissolved in the copper-silver alloy are precipitated to increase its hardness. The heating temperature for the precipitation hardening heat treatment is, for example, in the range of 400 to 500°C, and the heating time is, for example, in the range of 5 to 15 hours.

[0026] In the rolling process (S120), the copper-silver alloy is subjected to rolling after precipitation hardening heat treatment. Subsequently, the copper-silver alloy, which has been precipitation hardened and cooled, is subjected to rolling. Here, "rolling" refers to a process in which a continuous force is applied to the base material to thin the copper-silver alloy. In this embodiment, the rolling is performed by rotating a pair of parallel-arranged rolls and passing the copper-silver alloy between these rolls. The type of rolling is not particularly limited. Examples of rolling types include cold rolling, hot rolling, and warm rolling. In this embodiment, the type of rolling is cold rolling. The thickness of the copper-silver alloy after rolling is not particularly limited, but is in the range of 0.01 to 20 mm.

[0027] In the annealing process (S130), the copper-silver alloy is heated again after the rolling process. Here, "annealing" refers to a heating process to remove residual stress from the copper-silver alloy after the rolling process. The heating temperature in the annealing process is, for example, in the range of 320 to 450°C, and the heating time is, for example, in the range of 30 to 50 hours.

[0028] In the step of applying the rolling treatment again (S140), the annealed copper-silver alloy is rolled again to obtain the foil material 10. The rolling treatment is the same as the rolling treatment described above. In this embodiment, the thickness of the foil material after rolling is not particularly limited, but is in the range of 0.01 to 0.20 mm.

[0029] The annealing process (S130) and the re-rolling process (S140) are optional. In this case, the rolling process (S120) is performed by rolling the foil material to its desired thickness. The thickness of the foil material 10 at this time is, for example, within the range of 0.01 to 0.20 mm.

[0030] In this embodiment, the shear zone area ratio is kept within the range of 40-70% by combining precipitation hardening heat treatment, annealing treatment, and rolling treatment under predetermined conditions.

[0031] (Effects) As described above, according to the present invention, the foil material has a tensile strength of more than 1250 MPa in the direction perpendicular to rolling, an electrical conductivity of 50% IACS or more, a Vickers hardness of 300 HV or more in the direction perpendicular to rolling, and a shear band area ratio in the cross section viewed from the direction perpendicular to rolling is in the range of 40 to 70%, making it ideal as a foil material for semiconductor inspection probes.

[0032] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited in any way by these examples, and modifications to the embodiments are possible without departing from the spirit of the invention.

[0033] (Manufacturing of Foil Material) For the manufacturing of the foil material of Example 1, a raw material containing a predetermined amount of Ag and the remainder being Cu was heated at 1000 to 1400°C to prepare molten metal. The molten metal was poured into a mold and cooled to room temperature within 10 minutes to cast a plate material with a thickness of 30 mm and a width of 100 mm. Next, a precipitation hardening heat treatment was performed by heating at 450°C for 10 hours. Finally, the foil material of Example 1 was obtained by cold rolling to a thickness of 0.050 mm. The degree of cold working at this time was calculated using the following formula and was 6.4%. Degree of cold working = Ln (Cross-sectional area after precipitation hardening heat treatment or annealing treatment / Cross-sectional area after rolling treatment)

[0034] The foil material of Example 2 was manufactured in the same manner as the foil material of Example 1, except that the obtained foil material was rolled to a thickness of 0.020 mm. The degree of cold working at this time was 7.3%.

[0035] For the production of the foil material in Example 3, a raw material containing a predetermined amount of Ag and the remainder being Cu was heated at 1000 to 1400°C to prepare molten metal. The molten metal was poured into a mold and cooled to room temperature within 10 minutes to cast a plate material with a thickness of 30 mm and a width of 100 mm. Next, a precipitation hardening heat treatment was performed by heating at 450°C for 10 hours, followed by cold rolling. Then, an annealing treatment was performed by heating at 370°C for 40 hours. The thickness after the annealing treatment was 4 mm. Finally, the foil material of Example 3 was obtained by cold rolling again to a thickness of 0.02 mm. The degree of cold working at this time was 5.3%.

[0036] Except for changing the manufacturing silver content, foil thickness, and degree of cold working of the foil materials in Examples 4-7 and Comparative Examples 1 and 3-5 as shown in Table 1, the foil materials of Examples 4-7 and Comparative Examples 1 and 3-5 were obtained in the same manner as the foil material of Example 3.

[0037] Manufacturing of the foil material of Comparative Example 2 In the manufacturing method of the foil material of Comparative Example 2, a metal material containing 10% by mass of silver, with the remainder being copper and unavoidable impurities, was heated at 750°C for 2 hours, and then cooled with water to obtain a copper-silver alloy (solution treatment). Then, the foil material of Comparative Example 2 was obtained in the same manner as the foil material of Example 3, except that the presence or absence of annealing treatment, the thickness of the foil material, and the cold working rate were changed as shown in Table 1.

[0038] The shear band area ratio was analyzed using an EBSD device (DigiView 5; AMETEK) and analysis software (OIM Analysis; AMETEK) in a cross-section of the foil material viewed from the direction perpendicular to the rolling direction (TD direction). For foil materials with a thickness of 0.05 mm or more, the measurement step size was 0.05 μm, and the measurement range was within a 30 × 30 μm area inside the top 10% of the surface. For foil materials with a thickness of less than 0.05 mm, the measurement step size was 0.025 μm, and the measurement range was within a 15 × 15 μm area inside the top 10% of the surface.

[0039] (Evaluation) Tensile strength was measured on three strip-shaped test pieces in accordance with JIS Z2241:2011, and the average value obtained from the three test pieces was taken as the tensile strength.

[0040] Vickers hardness was measured using a Vickers hardness tester in accordance with JIS Z 2244:2009.

[0041] The conductivity was calculated using the average cross-sectional area method after measuring the electrical resistance of a test piece measuring 5 mm in width and 100 mm in length with a double-bridge resistance measuring device.

[0042] Processability was judged based on whether or not cracks or pinholes occurred during rolling and whether or not the material could be processed to the specified thickness. The criteria for judgment are as follows: ○: No cracks or pinholes occurred during rolling ×: Cracks or pinholes occurred during rolling

[0043] Table 1 shows the manufacturing conditions and evaluation results for each foil material.

[0044]

[0045] As shown in Table 1, when the manufacturing conditions were the continuous casting method (when no solution heat treatment was performed: Examples 1 to 7), the tensile strength in the rolling perpendicular direction was over 1250 MPa, the conductivity was 50% or more, the Vickers hardness in the rolling perpendicular direction was 300 HV or more, and the shear band area ratio in the cross section viewed from the rolling perpendicular direction was within the range of 40 to 70%, and a foil material suitable for semiconductor inspection probes and the like could be manufactured.

[0046] On the other hand, for the foil material of Comparative Example 2 that did not employ the continuous casting method, the shear band area ratio in the cross section viewed from the rolling perpendicular direction exceeded 70%, the workability deteriorated, and the possibility of breakage during processing and generation of pinhole defects increased. Also, for the foil material of Comparative Example 3 where the continuous casting method was employed but the shear band area ratio in the cross section viewed from the rolling perpendicular direction exceeded 70%, the workability deteriorated, and the possibility of breakage during processing and generation of pinhole defects increased. On the other hand, for the foil materials of Comparative Examples 1, 4, and 5 that employed the continuous casting method and had a shear band area ratio in the cross section viewed from the rolling perpendicular direction of less than 40%, the required tensile strength and hardness could not be sufficiently obtained, and it was considered that wear would occur quickly when used for semiconductor inspection probes.

[0047] The foil material of the present invention can be used for various applications such as semiconductor inspection probes.

[0048] 10 Foil material

Claims

1. A copper-silver alloy foil material containing 10 to 20% by mass of silver, with the remainder being copper and unavoidable impurities, wherein the tensile strength in the direction perpendicular to the rolling direction is greater than 1250 MPa, the electrical conductivity is 50% IACS or higher, the Vickers hardness in the direction perpendicular to the rolling direction is 300 HV or higher, and the shear band area ratio in the cross-section viewed from the direction perpendicular to the rolling direction is in the range of 40 to 70%.

2. A copper-silver alloy foil material according to claim 1, characterized in that the tensile strength in the direction perpendicular to the rolling is greater than 1300 MPa.

3. A method for manufacturing a copper-silver alloy foil, comprising the steps of: preparing a copper-silver alloy manufactured by a continuous casting method, containing 10 to 20% by mass of silver, with the remainder being copper and unavoidable impurities; and subjecting the copper-silver alloy to a rolling treatment, wherein the foil after the rolling treatment has a tensile strength of over 1250 MPa in the direction perpendicular to the rolling, an electrical conductivity of 50% IACS or more, a Vickers hardness of 300 HV or more in the direction perpendicular to the rolling, and a shear band area ratio in the cross-section viewed from the direction perpendicular to the rolling within the range of 40 to 70%.

4. A method for manufacturing a copper-silver alloy foil according to claim 3, further comprising the steps of: annealing the copper-silver alloy that has been subjected to the rolling treatment; and re-rolling the copper-silver alloy that has been subjected to the annealing treatment, wherein the foil after the re-rolling treatment has a tensile strength in the direction perpendicular to the rolling direction of more than 1250 MPa, an electrical conductivity of 50% IACS or more, a Vickers hardness in the direction perpendicular to the rolling direction of 300 HV or more, and a shear band area ratio in the cross-section viewed from the direction perpendicular to the rolling direction of 40 to 70%.

5. A method for manufacturing a copper-silver alloy foil according to claim 3, characterized in that the tensile strength in the direction perpendicular to the rolling is greater than 1300 MPa.

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