JP6355671B2 - Cu-Ni-Si-based copper alloy strip and method for producing the same - Google Patents

Description

  The present invention relates to a Cu-Ni-Si-based copper alloy strip that can be suitably used for manufacturing electronic parts such as electronic materials, and a method for manufacturing the same.

In recent years, along with the miniaturization of IC packages, miniaturization of lead frames, various terminals of electronic devices, connectors, and the like, and hence the increase in the number of pins has been demanded. In particular, a structure called QFN (quad flat non-leaded package), in which electrode pads are arranged on the land of an LSI package and lead pins are not output, has been developed. . In order to increase the number of pins of these lead frames and the like, fine processing by etching is required. Therefore, it is required to improve the strength of the copper alloy as a material and improve the etching property.
In view of this, a technique has been proposed in which the number of inclusions is regulated to prevent a decrease in etching property due to coarse inclusions (Patent Document 1).

JP 2001-49369 A

However, when the number of inclusions is restricted, the etching failure is improved, but the surface unevenness generated in the copper alloy base material itself cannot be improved. For this reason, there is a problem that roughness called “arabi” occurs on the surface after etching, which hinders fine processing. Further, it is possible to reduce the surface unevenness after etching by using a special etching solution or the like, but the etching work becomes complicated, which may lead to a decrease in productivity and an increase in cost.
That is, the present invention has been made to solve the above problems, and provides a Cu—Ni—Si based copper alloy strip having improved strength and reduced surface irregularities after etching, and a method for producing the same. Objective.

  As a result of various studies by the inventors, if the pole density of all crystal orientations of the copper alloy is all 12 or less, the difference in the etching rate due to each crystal orientation becomes small, and the surface unevenness after etching becomes low and the etching becomes low. It has been found that the property (for example, soft etching property) is improved.

  That is, the Cu—Ni—Si based copper alloy strip of the present invention contains Ni: 1.5 to 4.5 mass%, Si: 0.4 to 1.1 mass%, and consists of the balance Cu and inevitable impurities. A Cu—Ni—Si copper alloy strip having a conductivity of 30% IACS or more, a tensile strength of 800 MPa or more, and a direction perpendicular to the plane including the [001] orientation of the crystal and the ND direction of the material. When the rotation angle about the axis is Φ, the rotation angle about the ND direction is φ1, and the rotation angle about the [001] direction is φ2, after rotating the ND axis as the rotation axis by φ1, In order to make the ND axis and the z axis coincide with each other, it is rotated by Φ, and finally it is rotated by φ2 around the [001] axis, so that the ND, TD, RD of the material and the [001], [010], [100] of the crystal ] For Euler angles (φ1, Φ, φ2) Pole density of the crystal orientation in all Euler angle is 12 or less.

  Furthermore, it is preferable to contain 0.005-0.8 mass% of 1 or more types chosen from the group of Mg, Fe, P, Mn, Co, and Cr in total.

The method for producing a Cu—Ni—Si based copper alloy strip according to the present invention is the method for producing a Cu—Ni—Si based copper alloy strip according to claim 1, wherein Ni: 1.5 to 4.5 mass. %, Si: 0.4 to 1.1% by mass, and after hot rolling a Cu—Ni—Si based copper alloy strip ingot consisting of the remainder Cu and inevitable impurities, solution treatment, aging treatment, material Diffusion heat treatment is performed in this order at a temperature of 220 to 280 ° C. and a soaking time of 24 hours or more , and cold rolling is performed after the diffusion heat treatment at a working degree of 40% or more.

  According to the present invention, it is possible to obtain a Cu—Ni—Si based copper alloy strip having high strength and reduced surface unevenness after etching.

It is a figure which shows Euler angles ((phi) 1, (phi), (phi) 2). FIG. 6 is a diagram showing a crystal orientation distribution function ODF of Example 4. 14 is a diagram showing a crystal orientation distribution function ODF of Comparative Example 18. FIG. It is a figure which shows (phi) 2 of 19 graphs of FIG. 2, FIG. It is a figure which shows (PHI) and (phi) 1 of 19 graphs of FIG. 2, FIG.

  Hereinafter, the Cu—Ni—Si based copper alloy strip according to the embodiment of the present invention will be described. In the present invention, “%” means “% by mass” unless otherwise specified.

First, the reasons for limiting the composition of the copper alloy strip will be described.
<Ni and Si>
Ni and Si form precipitation particles of intermetallic compounds mainly composed of Ni ₂ Si in which Ni and Si are fine by performing an aging treatment, and remarkably increase the strength of the alloy. Further, the conductivity is improved with the precipitation of Ni ₂ Si in the aging treatment. However, when the Ni concentration is less than 1.5% or the Si concentration is less than 0.4%, the desired strength cannot be obtained even if the other component is added. Further, when the Ni concentration exceeds 4.5%, or when the Si concentration exceeds 1.1%, sufficient strength can be obtained, but the conductivity becomes low, and further coarse Ni that does not contribute to the improvement of the strength. -Si-based particles (crystallized substances and precipitates) are generated in the matrix phase, and bending workability, etching properties and plating properties are reduced. Therefore, the Ni content is 1.5 to 4.5%, and the Si content is 0.4 to 1.1%. Preferably, the Ni content is 1.6 to 3.0%, and the Si content is 0.4 to 0.7%.

<Other elements>
Furthermore, in the above alloy, for the purpose of improving the strength, heat resistance, stress relaxation resistance, etc. of the alloy, one or more selected from the group of Mg, Fe, P, Mn, Co and Cr is added in a total of 0.005 to 0.8. It can be contained by mass%. When the total amount of these elements is less than 0.005% by mass, the above effect does not occur, and when it exceeds 0.8% by mass, the desired properties can be obtained, but the conductivity and bending workability may be deteriorated.

<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 element increases, heat generation due to energization increases, so the conductivity of the copper alloy strip is set to 30% IACS or higher.
Further, the tensile strength TS is set to 800 MPa or more in order to prevent deformation of the lead frame during wire bonding and to maintain the shape.

<Polar density of each crystal orientation>
In the Cu—Ni—Si based copper alloy strip according to the embodiment of the present invention, the rotation angle about the direction perpendicular to the plane including the [001] orientation of the crystal and the ND direction of the material is Φ, and the ND direction is the axis. In order to make the ND axis and the z axis coincide with each other after the rotation angle is expressed as φ1 and the rotation angle about the [001] direction as φ2, the ND axis is rotated by φ1. By rotating only by φ2 around the [001] axis, and the Euler angle that is a set of angles at which the ND, TD, and RD of the material and the [001], [010], and [100] of the crystal coincide with each other. For (φ1, Φ, φ2), the pole density of crystal orientation of all Euler angles (each of φ1, Φ, φ2 is 0 to 90 °) is 12 or less.

Here, as shown in FIG. 1, the Euler angles (φ1, Φ, φ2) are rotated by φ1 with the ND axis as a rotation axis, and then rotated by Φ to match the ND axis and the z axis, Finally, a pair of angles (φ1, Φ, φ2) in which the ND, TD, RD of the material and the [001], [010], [100] of the crystal coincide with each other by rotating by φ2 around the [001] axis. Say. Euler angles (φ1, Φ, φ2) are represented by the Bunge method shown in FIG. “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 the crystal orientations of the Cu—Ni—Si based copper alloy strip according to the embodiment of the present invention is all 12 or less, the difference in etching rate due to each crystal orientation becomes small, and the surface irregularities after etching Becomes lower and the etching property is improved. As a result, the etching accuracy is improved and fine processing is possible. For example, the number of pins such as a lead frame can be reduced and the pitch can be reduced.

On the other hand, if the pole density of the crystal orientation at any Euler angle exceeds 12, the etching rate of the crystal orientation is greatly different from the etching rate of other orientations, and the surface unevenness after etching becomes large.
The lower limit of the crystal orientation pole density is not particularly limited, but the lower limit is 1 which is the pole density of random orientation similar to copper powder.
As a method for controlling the pole density of all crystal orientations to 12 or less, “diffusion heat treatment and subsequent cold rolling” may be performed after the aging treatment. The diffusion heat treatment and the cold rolling after the diffusion heat treatment will be described later.

<Manufacture of Cu-Ni-Si-based copper alloy strip>
The Cu—Ni—Si based copper alloy strip according to the embodiment of the present invention is usually obtained by hot rolling an ingot, cold rolling, solution treatment, aging treatment, diffusion heat treatment, cold rolling after diffusion heat treatment, strain relief annealing. It can be manufactured in the order of. Cold rolling before solution treatment is not essential, and may be performed as necessary. Moreover, you may implement cold rolling as needed after solution treatment and before an aging treatment. Between the above steps, grinding, polishing, shot blasting, pickling and the like for removing oxide scale on the surface can be appropriately performed.

The solution treatment is a heat treatment in which a silicide such as a Ni—Si compound is dissolved in a Cu matrix and the Cu matrix is recrystallized at the same time. The solution treatment can also be performed by hot rolling.
In the aging treatment, silicide dissolved in the solution treatment is precipitated as fine particles of an intermetallic compound mainly composed of Ni ₂ Si. This aging treatment increases strength and conductivity. The aging treatment can be performed, for example, under conditions of 375 to 625 ° C. and 0.5 to 50 hours, whereby the strength can be improved.

<Diffusion heat treatment and cold rolling after diffusion heat treatment>
After the aging treatment, diffusion heat treatment is performed. The diffusion heat treatment can be performed, for example, under conditions where the material temperature is 220 to 280 ° C. and the soaking time is 24 hours or more.
In the aging treatment, Ni and Si in the matrix (base material) are precipitated as an intermetallic compound such as Ni ₂ Si as described above. However, Ni and Si in the matrix in the vicinity of the precipitated particles are consumed, and Ni is compared with the surroundings. , Si concentration decreases. That is, a concentration gradient of Ni and Si is generated from the precipitate particle / matrix boundary toward the surrounding matrix. When such a concentration gradient occurs in the matrix, a difference in concentration (composition) becomes a difference in structure, and an orientation having a pole density greater than 12 is generated.
Therefore, by performing diffusion heat treatment to be low-temperature heating, Ni and Si diffuse so that the concentration gradient in the matrix is reduced and uniform, and the structure after rolling does not collect in one direction (the extreme density is Lower).

When the temperature of the diffusion heat treatment is less than 220 ° C. or the time is less than 24 hours, the diffusion heat treatment becomes insufficient, the concentration gradient of the base material (matrix) is not reduced, the composition becomes nonuniform, and the extreme density is 12 A crystal orientation exceeding 1 is generated.
When the temperature of the diffusion heat treatment exceeds 280 ° C., the diffusion heat treatment becomes excessive, the precipitation of intermetallic compounds mainly containing Ni ₂ Si becomes remarkable, and the composition of the base material (matrix) becomes nonuniform as well. As a result, the polar density of the crystal orientation exceeds 12.
The diffusion heat treatment time may be 24 hours or longer, but is preferably 24 to 36 hours.

Next, after the diffusion heat treatment, cold rolling (cold rolling after diffusion heat treatment) is performed at a workability of 40% or more. A recrystallized structure remains by the solution treatment described above, and even if the diffusion heat treatment is sufficiently performed, the extreme density is increased.
Therefore, if cold rolling with a workability of 40% or more is performed after the diffusion heat treatment, the recrystallized texture generated by the solution treatment can be eliminated by the processing. In addition, the above-described precipitated particles such as Ni ₂ Si suppress the occurrence of aggregation in a specific direction by rolling. By combining these effects, the pole density is reduced.
If the degree of work of cold rolling after diffusion heat treatment is less than 40%, it is difficult to sufficiently eliminate the recrystallized structure remaining by solution treatment, and crystal orientation with a pole density exceeding 12 is generated.

The degree of cold rolling after diffusion heat treatment is preferably 40 to 90%. If the degree of work exceeds 90%, the extreme density of a specific orientation increases due to strong working, which exceeds the effect of suppressing the growth of the specific orientation by the precipitated particles, and a crystal orientation with a pole density exceeding 12 may occur.
The degree of workability of cold rolling after diffusion heat treatment is the rate of change in thickness due to cold rolling after diffusion heat treatment relative to the material thickness 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, but may be 0.03 to 0.6 mm, for example.

Samples of Examples and Comparative Examples were prepared as follows.
Using copper as a raw material, copper alloys having the compositions shown in Tables 1 and 2 were melted using an atmospheric melting furnace and cast into ingots having a thickness of 20 mm and a width of 60 mm. This ingot was hot-rolled at 950 ° C. to a plate thickness of 10 mm. After hot rolling, grinding, cold rolling, and solution treatment were performed in this order.
Next, an aging treatment and a diffusion heat treatment were performed in this order under the conditions shown in Tables 1 and 2. Thereafter, cold rolling was performed after the diffusion heat treatment at the processing levels shown in Tables 1 and 2, and a stress relief annealing was performed at 100 to 200 ° C. for 1 to 30 seconds to obtain a sample having a plate thickness of 0.126 mm.

<Conductivity (% IACS)>
About the obtained sample, the electrical conductivity (% IACS) of 25 degreeC was measured by 4 terminal method based on JISH0505.

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

<Polar density of crystal orientation>
About the obtained sample, the positive electrode point measurement of the surface of the sample was performed using the X ray diffraction method. The X-ray diffractometer was measured by the Schulz reflection method using RINT-2000 manufactured by Rigaku Corporation. The measurement conditions are as follows.
X-ray source: cobalt, acceleration voltage: 30 kV, tube current: 100 mA, divergence slit: 1 °, divergence length limit slit: 1.2 mm, scattering slit: 7 mm, light receiving slit: 7 mm
α angle step: 5 °, β angle step: 5 °, counting time: 2 seconds / step However, in the reflection method, measurement becomes difficult when the X-ray incidence angle with respect to the sample surface becomes shallow. The ranges are 0 ° ≦ α ≦ 75 ° and 0 ° ≦ β ≦ 360 ° on the positive dot diagram (where α is an axis perpendicular to the rotational axis of the goniometer for diffraction defined in the Schulz method, β is parallel to the rotational axis) The right axis).

The obtained measurement results are converted into pole figures using the Pole Figure DataProcessing software manufactured by Rigaku Corporation, and the crystal orientation distribution function ODF is analyzed by a crystal orientation distribution function analysis program (product name: Standard ODF) for cubic crystals manufactured by Norm Engineering Co., Ltd. (Orientation Distration Function) was calculated, and the polar density of crystal orientation at all Euler angles was output. And the maximum value of pole density was calculated | required from them. The Euler angle is output from the above software in 5 ° increments.
In a material having a completely random crystal orientation, the pole density of the crystal orientation at all Euler angles is 1, and the value normalized with respect to this value is the numeric value of the pole density of the sample.

  2 and 3 show the crystal orientation distribution function ODF of Example 4 and Comparative Example 18 described later, respectively. Here, FIG. 2 and FIG. 3 show a list of 19 graphs, 5 in the vertical direction and 4 in the horizontal direction, except for the display at the lower right, and φ2 (0 to 90 °: 5 °) of each graph. The step is shown in FIG. In addition, as shown in FIG. 5, the vertical axis of each graph is Φ and the horizontal axis is φ1, and the value of Φ = 0 to 90 ° is taken from the top to the bottom of the box indicating each graph. The value of Φ1 = 0 to 90 ° is taken from the left to the right of the box indicating.

<Etching property>
Spray both sides of the obtained sample with an aqueous ferric chloride solution at a liquid temperature of 40 ° C. adjusted to a concentration of 47 baume for 1 to 5 minutes to a plate thickness of 0.063 mm (half the original 0.126 mm thickness). It adjusted so that it might become, and etched. Arithmetic average roughness Ra according to JIS B0601 (2013) was measured using a confocal microscope (manufactured by Lasertec Co., Ltd., model number: HD100D) with the etched surface having a reference length of 0.8 mm in the parallel direction of rolling and an evaluation length of 4 mm. .
When the arithmetic average roughness Ra after etching is less than 0.15 μm, there are few irregularities after etching and the etching property is excellent.

  The obtained results are shown in Tables 1 and 2.

  As is clear from Tables 1 and 2, in each example where the pole density of the crystal orientation at all Euler angles is 12 or less, the strength is high and the lead deformation is small, and the surface roughness after etching is reduced. It was.

On the other hand, in Comparative Examples 1 to 4 in which the diffusion heat treatment was not performed, the pole density of the crystal orientation exceeded 12, and the etching surface unevenness increased. In Comparative Example 3, since the Ni content was less than the specified range, the tensile strength was less than 800 MPa. In Comparative Example 4, since the Ni and Si contents exceeded the specified range, the conductivity was less than 30% IACS.
In Comparative Examples 5 to 9 in which the temperature of the diffusion heat treatment exceeded 280 ° C., the pole density of the crystal orientation exceeded 12, and the etching surface unevenness increased. This is thought to be due to the fact that silicide precipitation was prominent due to the high temperature of the diffusion heat treatment, and a concentration gradient (non-uniform composition) occurred in Ni and Si in the matrix. In Comparative Example 9, since the Ni and Si contents exceeded the specified range, the conductivity was less than 30% IACS.

In Comparative Examples 10 and 11 in which the temperature of the diffusion heat treatment is less than 220 ° C. and in Comparative Examples 12 to 16 in which the time of the diffusion heat treatment is less than 24 hours, the pole density of the crystal orientation exceeds 12, and the etching surface irregularities It became high. In Comparative Example 15, since the Ni content was less than the specified range, the tensile strength was less than 800 MPa. In Comparative Example 16, since the Si content exceeded the specified range, the conductivity was less than 30% IACS.
Also in Comparative Examples 17 to 21 in which the degree of cold rolling after diffusion heat treatment was less than 40%, the pole density of the crystal orientation exceeded 12, and the etching surface unevenness increased. In Comparative Example 20, since the Si content was less than the specified range, the tensile strength was less than 800 MPa. In Comparative Example 21, since the Ni and Si contents exceeded the specified range, the conductivity was less than 30% IACS.

Claims (3)

It is a Cu—Ni—Si based copper alloy strip containing Ni: 1.5 to 4.5% by mass, Si: 0.4 to 1.1% by mass, the balance being Cu and inevitable impurities,
Conductivity is 30% IACS or more, tensile strength is 800 MPa or more,
The rotation angle about the direction perpendicular to the plane including the [001] orientation of the crystal and the ND direction of the material is Φ, the rotation angle about the ND direction is φ1, and the rotation angle about the [001] direction is When written as φ2,
After rotating by φ1 with the ND axis as the rotation axis, it is rotated by φ to match the ND axis and the z axis, and finally rotated by φ2 around the [001] axis, so that the materials ND, TD, RD And Euler angles (φ1, Φ, φ2), which are pairs of angles where [001], [010], and [100] of the crystal coincide with each other, Cu polarities of crystal orientations at all Euler angles are 12 or less. -Ni-Si type copper alloy strip. The Cu-Ni-Si-based copper alloy strip according to claim 1, further comprising 0.005 to 0.8 mass% in total of at least one selected from the group consisting of Mg, Fe, P, Mn, Co and Cr. Hot rolling an ingot of Cu—Ni—Si based copper alloy strip containing Ni: 1.5 to 4.5 mass%, Si: 0.4 to 1.1 mass%, and remaining Cu and inevitable impurities after solution treatment, aging treatment, claim material temperature 220 to 280 ° C., the soaking time perform diffusion heat treatment of 24 hours or more in this order, for further diffusion heat treatment after cold rolling at a working ratio of 40% or more 1 Or the manufacturing method of Cu-Ni-Si type | system | group copper alloy strip | line of 2 description .