TWI625403B - Cu-Ni-Si series copper alloy bar and manufacturing method thereof - Google Patents

Abstract

Provided are a Cu-Ni-Si-based copper alloy strip having improved strength and reduced surface unevenness after etching, and a method for manufacturing the same.

A Cu-Ni-Si-based copper alloy bar containing Ni: 1.5 to 4.5 mass%, Si: 0.4 to 1.1 mass%, electrical conductivity of 30% IACS or higher, tensile strength of 800 MPa or more, and the Euler angle ( 1, Φ, 2) The polar density of the crystal orientation in all Euler angles is less than 12, the Euler angle is the rotation angle that will be the axis perpendicular to the plane containing the [001] orientation of the crystal and the ND direction of the material Let Φ be the rotation angle with the ND direction as the axis. 1. Record the rotation angle with the [001] direction as the axis In the case of 2, by rotating only with the ND axis as the rotation axis After 1, only Φ is rotated in order to make the ND axis coincide with the z axis, and finally only rotates around the [001] axis 2, and the angles at which the ND, TD, and RD of the material coincide with the [001], [010], and [100] of the crystal.

Description

Cu-Ni-Si series copper alloy bar and manufacturing method thereof

The present invention relates to a Cu-Ni-Si-based copper alloy bar and a manufacturing method thereof which can be preferably used for manufacturing electronic parts such as electronic parts.

In recent years, with the miniaturization of IC packages, miniaturization of lead frames, various terminals of electronic devices, connectors, and the like have been required, and more pins have been required. In particular, a structure called quan flat non-leaded package (quad flat non-leaded package) has been developed to dispose electrode pads on the LSI package's pads without lead pins, further requiring multi-pin, Narrow pitch. In order to increase the number of pins of the lead frame and the like, it is necessary to perform microfabrication by etching. Therefore, it is required to increase the strength of the copper alloy as a material and to improve the etchability.

Therefore, a technique has been proposed in which the number of inclusions is limited to suppress deterioration of etching properties due to coarse inclusions (Patent Document 1).

[Patent Document 1] Japanese Patent Laid-Open No. 2001-49369

However, if the number of inclusions is limited, although the etching failure is improved, it cannot be improved. Surface irregularities generated in the base material of the copper alloy itself. Therefore, there is a problem in that a rough surface called "orange peel" is generated on the surface after etching, preventing fine processing. In addition, by using a special etching solution or the like, it is possible to reduce the unevenness of the surface after the etching, but there is a possibility that the etching operation is complicated and the productivity is lowered or the cost is increased.

That is, the present invention has been made in order to solve the above-mentioned problems, and an object thereof is to provide a Cu-Ni-Si-based copper alloy strip having improved strength and reduced surface unevenness after etching, and a method for producing the same.

The present inventors conducted various studies, and found that if the pole density of all crystal orientations of the copper alloy is 12 or less, the difference in etching speed between the crystal orientations becomes smaller, and the surface unevenness after etching becomes lower. Etching (for example, soft etching) is improved.

That is, the Cu-Ni-Si-based copper alloy strip of the present invention contains Ni: 1.5 to 4.5% by mass and Si: 0.4 to 1.1% by mass. The remaining portion is made of Cu and unavoidable impurities. The tensile strength is 800 MPa or more. Regarding the Euler angle ( 1, Φ, 2) The polar density of the crystal orientation in all Euler angles is less than 12, the Euler angle is the rotation angle that will be the axis perpendicular to the plane containing the [001] orientation of the crystal and the ND direction of the material. Let Φ be the rotation angle with the ND direction as the axis. 1. Record the rotation angle with the [001] direction as the axis In the case of 2, by rotating only with the ND axis as the rotation axis After 1, in order to make the ND axis coincide with the z axis, only rotate Φ, and finally only rotate around the [001] axis 2 and the angle at which the ND, TD, and RD of the material are consistent with the crystal [001], [010], and [100].

Preferably, it further contains 0.005 to 0.8 mass% of one or more selected from the group consisting of Mg, Fe, P, Mn, Co, and Cr.

The method for manufacturing a Cu-Ni-Si-based copper alloy bar according to the present invention is that after hot-rolling an ingot of a Cu-Ni-Si-based copper alloy bar, the solution treatment, aging treatment, and diffusion heat treatment are sequentially performed, and then Cold rolling after diffusion heat treatment at a processing rate of 40% or more, wherein the Cu-Ni-Si-based copper alloy strip contains Ni: 1.5 to 4.5% by mass, Si: 0.4 to 1.1% by mass, and the remaining portion is composed of Cu and inevitable impurities .

According to the present invention, a Cu-Ni-Si-based copper alloy strip having high strength and reduced surface unevenness after etching can be obtained.

Figure 1 shows the Euler angle ( 1, Φ, 2).

FIG. 2 is a graph showing a crystal orientation distribution function ODF of Example 4. FIG.

FIG. 3 is a graph showing a crystal orientation distribution function ODF of Comparative Example 18. FIG.

FIG. 4 is a diagram showing the 19 patterns in FIG. 2 and FIG. 3. Figure of 2.

Fig. 5 shows the Φ, 19 of the 19 figures in Fig. 2 and Fig. 3 Figure 1.

Hereinafter, a Cu-Ni-Si-based copper alloy bar according to an embodiment of the present invention will be described. In addition, in this invention,% is set as the mass% unless there is particular notice.

First, the reasons for limiting the composition of the copper alloy bars will be described.

<Ni and Si>

Ni and Si are subjected to aging treatment, and Ni and Si form precipitated particles of intermetallic compounds mainly composed of fine Ni ₂ Si, thereby significantly increasing the strength of the alloy. In addition, with the precipitation of Ni ₂ Si during the aging treatment, the conductivity is improved. However, when the Ni concentration is less than 1.5%, or when the Si concentration is less than 0.4%, the required strength cannot be obtained even if another component is added. In addition, when the Ni concentration exceeds 4.5%, or when the Si concentration exceeds 1.1%, although sufficient strength is obtained, the conductivity is reduced, and coarse Ni- Si-based particles (crystals and precipitates) reduce bending workability, etching properties, and plating properties. Therefore, the content of Ni is set to 1.5 to 4.5%, and the content of Si is set to 0.4 to 1.1%. The content of Ni is preferably 1.6 to 3.0%, and the content of Si is preferably 0.4 to 0.7%.

<Other elements>

Furthermore, in order to improve the strength, heat resistance, and stress relaxation resistance of the alloy, the above alloy may further contain 0.005 to 0.8% by mass of one or more members selected from the group consisting of Mg, Fe, P, Mn, Co, and Cr. . If the total amount of these elements is less than 0.005 mass%, the above-mentioned effects will not be produced, and if it exceeds 0.8 mass%, the required characteristics may be obtained but the conductivity or bendability may be reduced.

<Conductivity and tensile strength TS>

The Cu-Ni-Si-based copper alloy strip according to the embodiment of the present invention has a conductivity of 30% IACS or more and a tensile strength TS of 800 MPa or more.

As the operating frequency of the semiconductor device increases, the heat generation due to the energization increases, so the conductivity of the copper alloy strip is set to 30% IACS or more.

In addition, in order to prevent deformation and the like of the lead frame during wire bonding and maintain the shape, the tensile strength TS is set to 800 MPa or more.

<Extreme density of each crystal orientation>

The Cu-Ni-Si-based copper alloy strip according to the embodiment of the present invention relates to the Euler angle ( 1, Φ, 2), all Euler angles ( 1, Φ, The polar density of the crystal orientation is 2 or less, respectively. The Euler angle is the rotation angle recorded on the axis perpendicular to the plane containing the [001] orientation of the crystal and the ND direction of the material. Let Φ be the rotation angle with the ND direction as the axis 1. Record the rotation angle with the [001] direction as the axis In the case of 2, by rotating only with the ND axis as the rotation axis After 1, only Φ is rotated in order to make the ND axis coincide with the z axis, and finally only rotates around the [001] axis 2 and the angle at which the ND, TD, and RD of the material are consistent with the crystal [001], [010], and [100].

Here, as shown in Figure 1, Euler angle ( 1, Φ, 2) Refers to rotation only with the ND axis as the rotation axis After 1, in order to make the ND axis coincide with the z axis, only rotate Φ, and finally only rotate around the [001] axis 2 The set of angles that make the ND, TD, and RD of the material coincide with [001], [010], and [100] of the crystal ( 1, Φ, 2). Euler angle 1, Φ, 2) It is expressed by the Bunge method shown in FIG. 1. "RD" is the rolling direction, "ND" is the direction perpendicular to the rolling surface, and "TD" is the width direction.

If the pole density of all orientations of the Cu-Ni-Si-based copper alloy strip according to the embodiment of the present invention is 12 or less, the difference in etching speed between the crystal orientations will be reduced, and the surface unevenness after etching will be reduced to improve the etching properties. As a result, the etching accuracy is improved and the fine processing can be performed. For example, it is possible to increase the number of pins and narrow the pitch of the lead frame.

On the other hand, if the extreme density of the crystal orientation in any Euler angle exceeds 12, the etching rate of the crystal orientation is significantly different from that of other orientations, and the surface unevenness after etching becomes larger.

The lower limit of the extreme density of the crystal orientation is not particularly limited, and the extreme density of the same random orientation of copper powder is 1 as the lower limit.

As a method of controlling the extreme density of all crystal orientations to 12 or less, there may be mentioned: "diffuse heat treatment and subsequent cold rolling" after the aging treatment. The diffusion heat treatment and the cold rolling after the diffusion heat treatment will be described below.

<Manufacture of Cu-Ni-Si series copper alloy strip>

The Cu-Ni-Si-based copper alloy strip according to the embodiment of the present invention can generally be manufactured by sequentially hot rolling, cold rolling, solution treatment, aging treatment, diffusion heat treatment, cold rolling after diffusion heat treatment, and relaxation annealing in order. . Cold rolling before solution treatment is not necessary, and can also be implemented as needed. Alternatively, cold rolling may be performed after the solution treatment and before the aging treatment as needed. During the above steps, grinding, grinding, shot blasting, pickling, etc. for removing scale on the surface may be performed as appropriate.

The solution treatment is a heat treatment in which a silicide such as a Ni-Si compound is dissolved in the Cu matrix while the Cu matrix is recrystallized. It may also be subjected to a solution treatment by hot rolling.

The aging treatment precipitates the silicide dissolved in the solid solution treatment as fine particles of an intermetallic compound mainly composed of Ni ₂ Si. By this aging treatment, strength and electrical conductivity are increased. The aging treatment can be performed under conditions of, for example, 375 to 625 ° C. for 0.5 to 50 hours, whereby strength can be increased.

<Diffusion heat treatment and cold rolling after diffusion heat treatment>

After the aging treatment, a diffusion heat treatment is performed. The diffusion heat treatment can be performed under conditions such as a material temperature of 220 to 280 ° C. and a soaking time of 24 hours or more.

In the aging treatment, Ni and Si in the matrix (base material) are precipitated in the form of intermetallic compounds such as Ni ₂ Si, but Ni and Si in the matrix near the precipitated particles are consumed. The concentration is lower than the surroundings. That is, the concentration gradients of Ni and Si are generated from the precipitated particles and the boundary of the matrix toward the surrounding matrix. In addition, if such a concentration gradient is generated in the matrix, the difference in concentration (composition) becomes the difference in tissue, and an orientation with a pole density greater than 12 is generated.

Therefore, by performing a diffusion heat treatment that becomes low-temperature heating, the concentration gradient in the matrix decreases, and Ni and Si diffuse in a uniform manner, so that the rolled structure does not converge in one direction (the pole density decreases).

When the temperature of the diffusion heat treatment does not reach 220 ° C or the time does not reach 24 hours, the diffusion heat treatment becomes insufficient, the concentration gradient of the base material (matrix) does not decrease, the composition becomes non-uniform, and the extreme density exceeds Crystal orientation of 12.

When the temperature of the diffusion heat treatment exceeds 280 ° C, the diffusion heat treatment becomes excessive, the precipitation of intermetallic compounds mainly composed of Ni ₂ Si becomes significant, and the composition of the base material (matrix) becomes non-uniform. The extreme density of crystalline orientation exceeds 12.

The time for the diffusion heat treatment may be 24 hours or more, and is preferably 24-36 hours.

Then, after the diffusion heat treatment, cold rolling was performed at a workability of 40% or more (cold rolling after the diffusion heat treatment). The recrystallized structure remains due to the above-mentioned solid solution treatment, and this causes the extremely high density even if the diffusion heat treatment is sufficiently performed.

Therefore, if cold rolling with a working degree of 40% or more is performed after the diffusion heat treatment, the recrystallized aggregate structure generated by the solution treatment can be eliminated by processing. In addition, the generation of aggregates of the precipitated particles such as Ni ₂ Si and the like in a specific orientation is suppressed by the rolling process. By balancing these effects, the extreme density is reduced.

If the workability of the cold rolling after the diffusion heat treatment is less than 40%, it is difficult to sufficiently eliminate the recrystallized structure remaining due to solid solution, resulting in a crystal orientation with an extreme density exceeding 12.

The workability of cold rolling after the diffusion heat treatment is preferably 40 to 90%. If the degree of processing exceeds 90%, there is a case where the extreme density of a specific orientation increases due to strong machining, and the effect of suppressing the growth of the specific orientation by precipitating particles is increased, resulting in a crystal orientation with an extreme density of more than 12.

The workability of cold rolling after diffusion heat treatment is the rate of change of the thickness obtained by cold rolling after diffusion heat treatment relative to the thickness of the material immediately before cold rolling after diffusion heat treatment.

The thickness of the Cu-Ni-Si-based copper alloy strip of the present invention is not particularly limited, and may be, for example, 0.03 to 0.6 mm.

[Example]

Samples of Examples and Comparative Examples were prepared as follows.

Using electrolytic copper as a raw material, a copper alloy having the composition shown in Tables 1 and 2 was melted using an atmospheric melting furnace, and cast into an ingot having a thickness of 20 mm × width of 60 mm. This ingot was hot-rolled at 950 ° C until the thickness became 10 mm. After hot rolling, grinding, cold rolling, and solution treatment are performed sequentially.

Then, under the conditions shown in Tables 1 and 2, aging treatment and diffusion heat treatment were sequentially performed. Thereafter, cold rolling was performed after diffusion heat treatment at the processing degrees shown in Tables 1 and 2, and relaxation relaxation annealing was performed at 100 to 200 ° C for 1 to 30 seconds to obtain a sample having a thickness of 0.126 mm.

<Conductivity (% IACS)>

The obtained sample was measured for electrical conductivity (% IACS) at 25 ° C. by a 4-terminal method based on JIS H0505.

<Tensile strength (TS)>

About the obtained sample, the tensile strength (TS) in the direction parallel to a rolling direction was measured using the tensile tester according to JIS-Z2241, respectively. First, from each sample, a JIS13B test piece was produced using a press so that the tensile direction became the rolling direction. The conditions of the tensile test were set to a test piece width of 12.7 mm, room temperature (15 to 35 ° C.), a tensile speed of 5 mm / min, and a gauge length of 50 mm.

<Extreme density of crystal orientation>

The obtained sample was measured for the positive point on the surface of the sample using the X-ray diffraction method. The X-ray diffraction device was measured using RINT-2000 manufactured by Rigaku Co., Ltd. and measured by the Schulz reflection method. The measurement conditions are as follows.

X-ray source: Cobalt, acceleration voltage: 30kV, tube current: 100mA, divergence slit: 1 °, divergence longitudinal limit slit: 1.2mm, diffusion slit: 7mm, light receiving slit: 7mm

α angle step: 5 °, β angle step: 5 °, counting time: 2 seconds / step

However, in the reflection method, if the incident angle of X-rays to the sample surface becomes smaller, it is difficult to measure. Therefore, the angle range that can be actually measured becomes 0 ° ≦ α ≦ 75 °, 0 ° ≦ β ≦ 360 ° (where α: an axis perpendicular to the rotation axis of the diffraction goniometer specified in the Schultz method, β: an axis parallel to the above rotation axis).

For the obtained measurement results, pole mapping was performed using software Pole Figure Data Processing manufactured by Rigaku Co., Ltd., and a crystal orientation distribution function for cubic crystals manufactured by Norm Engineering Co., Ltd. was used. The analysis program (product name: Standard ODF) finds the crystal orientation distribution function ODF (Orientation Dsitribution Function) and outputs the extreme density of crystal orientation in all Euler angles. Then, the maximum value of the extreme density was obtained from them. Furthermore, Euler angles are output from the software described above every 5 °.

Furthermore, in a material having a completely random crystal orientation, the extreme density of the crystal orientation in all Euler angles becomes 1, so the value obtained by normalizing this value is the value of the extreme density of the sample.

In addition, FIG. 2 and FIG. 3 respectively show the crystal orientation distribution function ODF of Example 4 and Comparative Example 18 described below. Here, Fig. 2 and Fig. 3 show the 19 figures in the vertical direction and 4 in the horizontal direction except the lower right display. 2 (0 to 90 °: every 5 °) is shown in FIG. 4. As shown in FIG. 5, the vertical axis of each figure is Φ, and the horizontal axis is 1. Take the value of Φ = 0 ~ 90 ° from the top of the box representing each figure, and take the value of Φ 1 = 0 ~ 90 ° from the left to the right of the box representing each figure.

<Etchability>

For both sides of the obtained sample, spray the ferric chloride aqueous solution with the concentration adjusted to 47 Baume and the liquid temperature of 40 ° C for 1 to 5 minutes so that the plate thickness becomes 0.063 mm (the original thickness of 0.126 mm) Adjust and etch. Using a confocal microscope (manufactured by Laser Technology, model: HD100D), the etched surface was set to a reference length of 0.8 mm in the rolling parallel direction and an evaluation length of 4 mm. The arithmetic mean roughness Ra according to JIS B0601 (2013) was measured. .

If the arithmetic average roughness Ra after the etching is less than 0.15 μm, there will be less unevenness after the etching, and the etching will be excellent.

The obtained results are shown in Tables 1 and 2.

According to Tables 1 and 2, it can be known that in the cases of the examples where the polar density of the crystal orientation in all Euler angles is 12 or less, the lead wire with high strength has less deformation and the surface unevenness after etching is reduced.

On the other hand, in the cases of Comparative Examples 1 to 4 in which the diffusion heat treatment was not performed, the extreme density of the crystal orientation exceeded 12, and the surface unevenness of the etching was high. In addition, since the content of Ni in Comparative Example 3 did not reach the predetermined range, the tensile strength did not reach 800 MPa. Moreover, since the content of Ni and Si exceeded the predetermined range in Comparative Example 4, the electrical conductivity did not reach 30% IACS.

In the cases of Comparative Examples 5 to 9 where the temperature of the diffusion heat treatment exceeds 280 ° C, the extreme density of the crystal orientation exceeds 12, and the surface unevenness of the etching is high. The reason is considered to be that the silicide precipitates significantly due to the high temperature of the diffusion heat treatment, and the concentration gradient (uneven composition) of Ni and Si in the matrix occurs. In addition, since the content of Ni and Si exceeds the predetermined range in Comparative Example 9, the electrical conductivity does not reach 30% IACS.

In the cases of Comparative Examples 10 and 11 where the temperature of the diffusion heat treatment is less than 220 ° C and the cases of Comparative Examples 12 to 16 where the time of the diffusion heat treatment is less than 24 hours, the extreme density of the crystal orientation exceeds 12, and the etched surface High unevenness. In addition, since the content of Ni in Comparative Example 15 did not reach the predetermined range, the tensile strength did not reach 800 MPa. In Comparative Example 16, since the content of Si exceeded the predetermined range, the electrical conductivity did not reach 30% IACS.

In the cases of Comparative Examples 17 to 21 where the workability of cold rolling after the diffusion heat treatment was less than 40%, the extreme density of the crystal orientation also exceeded 12, and the surface roughness of the etching was high. In addition, since the content of Si in Comparative Example 20 did not reach the predetermined range, the tensile strength did not reach 800 MPa. In Comparative Example 21, since the contents of Ni and Si exceeded a predetermined range, the electrical conductivity did not reach 30% IACS.

Claims (3)

A Cu-Ni-Si series copper alloy bar, containing Ni: 1.5 ~ 4.5 mass%, Si: 0.4 ~ 1.1 mass%, the remaining part is composed of Cu and unavoidable impurities, the conductivity is above 30% IACS, and the tensile strength 800MPa or more, regarding Euler angle ( 1, Φ, 2) The pole density of the crystal orientation in all Euler angles is 12 or less. The Euler angle is in a direction perpendicular to the plane containing the [001] orientation of the crystal and the ND direction of the material. The rotation angle of the axis is denoted as Φ, and the rotation angle of the axis with the ND direction is denoted as 1. Record the rotation angle with the [001] direction as the axis In the case of 2, by rotating only with the ND axis as the rotation axis After 1, only Φ is rotated in order to make the ND axis coincide with the z axis, and finally only rotates around the [001] axis 2, and the angles at which the ND, TD, and RD of the material coincide with the [001], [010], and [100] of the crystal. For example, the Cu-Ni-Si-based copper alloy bar according to item 1 of the scope of the patent application further contains 0.005 to 0.8% by mass of one or more members selected from the group consisting of Mg, Fe, P, Mn, Co, and Cr. A method for manufacturing a Cu-Ni-Si-based copper alloy strip is based on hot-rolling an ingot of a Cu-Ni-Si-based copper alloy strip, followed by sequential solution treatment, aging treatment, diffusion heat treatment, and further processing. After cold-rolling after diffusion heat treatment at a temperature of 40% or more, the Cu-Ni-Si-based copper alloy strip contains Ni: 1.5 to 4.5% by mass and Si: 0.4 to 1.1% by mass, and the remaining portion is composed of Cu and inevitable impurities.