TW201940710A - Cu-Ni-Si-based copper alloy strip which is provided with improved strength and high flatness - Google Patents

Abstract

The present invention provides a Cu-Ni-Si-based copper alloy strip with improved strength and high flatness, and a method for producing the same. The Cu-Ni-Si copper alloy strip includes Ni: 1.5 to 4.5% by mass, Si: 0.4 to 1.1% by mass, and the balance including Cu and unavoidable impurities, and is provided with a conductivity of 30% IACS or more and a tensile strength of 800 MPa or more. According to JCBA-T326-2014, when the steepness in the rolling direction is measured at 5 or more points with a pitch of 25 mm or less along the vertical rolling direction orthogonal to the rolling direction, the average value of steepness is 0.5 or less, and the deviation rate of the steepness expressed by (deviation of steepness/average value of steepness)×100 is 12% or less.

Description

   Cu-Ni-Si series copper alloy bar   

The present invention relates to a Cu-Ni-Si-based copper alloy strip that can be suitably used in the manufacture of electronic parts such as electronic materials.

In recent years, with the miniaturization of IC packages, miniaturization and even multi-pinning of lead frames, various terminals and connectors of electronic devices are required. In particular, a structure in which electrode pads are arranged on a land of an LSI package called a QFN (quad flat non-leaded package) without exposing lead pins has been developed, and further multi-pin, narrow Spacing.

Here, when the lead frame is formed, the lead frame material needs to be etched. Further, in order to improve the productivity of the lead frame, it is required to widen the material width of the copper alloy strip as a material. Therefore, the material of the copper alloy strip used for the lead frame is required to have a large width and excellent flatness, and especially flatness after etching.

In addition, these copper alloys are required to have high strength and high electrical conductivity. As a material for lead frames, an age-precipitated Cu-Ni-Si-based copper alloy is used (Patent Document 1).

[Prior technical literature]

[Patent Literature]

[Patent Document 1] Japanese Unexamined Patent Publication No. 4-231419

However, as a method of correcting the shape of the material to improve the flatness, there is skin pass rolling. However, because of the high strength of the Cu-Ni-Si-based copper alloy, it is impossible to use the surface rolling to sufficiently shape correct. Therefore, there are cases where the flatness is not good. In addition, Patent Document 1 describes that surface rolling is performed after stress-relief annealing is performed. Although the strength of the material can be secured, the flatness cannot be sufficiently improved.

That is, the present invention has been made in order to solve the above problems, and an object thereof is to provide a Cu-Ni-Si-based copper alloy bar having improved strength and high flatness.

After various studies, the inventors have found that by implementing intermediate relaxation annealing before controlling the surface rolling of Cu-Ni-Si-based copper alloy and controlling the surface rolling processability, the workability of the material can be improved without compromising Strength, and can improve the flatness after surface rolling.

That is, the Cu-Ni-Si-based copper alloy strip of the present invention contains Ni: 1.5 to 4.5% by mass, Si: 0.4 to 1.1% by mass, and the remaining portion contains Cu and unavoidable impurities, and has a conductivity of 30% IACS or more, The tensile strength is 800 MPa or more. When the urgency of the rolling direction is measured at 5 points or more in a rolling orthogonal direction orthogonal to the rolling direction at a distance of 25 mm or less according to JCBA-T326-2014, the above-mentioned urgency is 0.5. Hereinafter, the deviation ratio of the urgency expressed by (the deviation of the urgency / the average value of the urgency) × 100 is 12% or less.

Furthermore, it is preferable to contain one or more selected from the group consisting of Mg, Fe, P, Mn, Co, and Cr in a total amount of 0.005 to 0.8% by mass.

According to the present invention, a Cu-Ni-Si-based copper alloy strip having high strength and high flatness can be obtained.

P‧‧‧Pitch

S1, S2‧‧‧Measurement points

2‧‧‧ height distribution in rolling direction

l‧‧‧wave length

h‧‧‧ wave height

FIG. 1 is a diagram showing an example of a top view of a material strain of a Cu—Ni—Si based copper alloy strip according to an embodiment of the present invention.

Fig. 2 is a schematic diagram showing a method for measuring the severity.

Fig. 3 is a schematic diagram showing a method for measuring flatness during processing of a lead frame.

FIG. 4 is a schematic diagram following FIG. 3.

Hereinafter, a Cu-Ni-Si-based copper alloy strip according to an embodiment of the present invention will be described. In addition, about% in the alloy composition of the present invention, unless otherwise specified, it means mass%.

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

<Ni and Si>

Regarding Ni and Si, Ni and Si are formed into precipitated particles of intermetallic compounds mainly composed of fine Ni ₂ Si by aging treatment, thereby significantly increasing the strength of the alloy. In addition, as Ni ₂ Si is precipitated during the aging treatment, the conductivity is improved.

However, when the Ni concentration is less than 1.5% or the Si concentration is less than 0.4%, the required strength cannot be obtained even if other components are added. In addition, when the Ni concentration exceeds 4.5% or the Si concentration exceeds 1.1%, sufficient strength can be obtained, but the conductivity decreases. 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 contain at least one selected from the group consisting of Mg, Fe, P, Mn, Co, and Cr in a total amount of 0.005 to 0.8%. If the total amount of these elements is less than 0.005%, the above-mentioned effect will not be produced; if it exceeds 0.8%, the required characteristics may be obtained, but the conductivity 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 semiconductor device becomes more functional and the processing capacity is increased, the electric heating of the lead frame and other circuits will increase, 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.

<Severity>

The average value of the severity in the rolling direction of the Cu-Ni-Si-based copper alloy strip according to the embodiment of the present invention is 0.5 or less, and is expressed by (deviation of severity D / average of severity Av) × 100. The deviation rate DR is less than 12%.

JCBA-T326-2014 specifies the severity. As shown in Figure 1, the change in the rolling direction of the surface of the Cu-Ni-Si-based copper alloy strip and the height (rolling) in the rolling direction are determined to determine the severity. degree.

Specifically, as shown in FIG. 2, the distance from the trough to the trough of the waveform in the rolling height distribution 2 is taken as the wave length l, and the distance from the straight line connecting the trough to the trough is taken as the wave length. The height h is expressed as the severity = (h / l) × 100 (%).

In addition, as shown in FIG. 1, the height distribution 2 in the rolling direction is measured at measurement points S1, S2,... At a distance P of 5 mm or less in the rolling orthogonal direction, and the average value is taken as the urgency. Mean Av.

When the average value of the severities Av is 0.5 or less, the flatness of the raw materials during the processing of the lead frame is high, so the wire bondability becomes good, and the defects in the assembly process are reduced.

Then, the deviation D of the severities obtained by measuring 5 or more points as described above is obtained, and the deviation rate DR of the severities is obtained from (the deviation D of the severities / the average value of the severities Av) × 100 (%).

If the deviation rate of severity is less than 12%, it means that the edge wave and center wave shapes of Cu-Ni-Si based copper alloy bars are suppressed. Even if the material width is large, the flatness will be improved. .

As a method of controlling the average value Av of the jerkiness to be 0.5 or less and the deviation rate of the jerkiness to be 12% or less, the conditions for defining the relaxation annealing and subsequent surface rolling as described below can be cited.

<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, post-aging cold rolling, relaxation annealing, and surface rolling. . Cold rolling before solution treatment is not necessary, and it can be performed as needed. In addition, if necessary, cold rolling may be performed after the solution treatment and before the aging treatment. Between the above processes, in order to remove the scale on the surface, grinding, grinding, shot blasting, pickling, etc. may 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 used for hot rolling.

In the aging treatment, the silicide solution-dissolved by the solution treatment is precipitated as fine particles of the intermetallic compound mainly composed of Ni ₂ Si. In this aging treatment, strength and electrical conductivity are increased. The aging treatment can be performed at, for example, 375 to 625 ° C. for 1 to 50 hours, thereby improving the strength.

If the temperature and time of the aging treatment are not within the above-mentioned ranges, there may be a case where the amount of precipitation of Ni ₂ Si is small and sufficient strength cannot be obtained. If the temperature and time of the aging treatment exceed the above ranges, the precipitates may coarsen or re-solidify, and the strength or conductivity may not be sufficiently improved.

<Cold rolling after aging>

Then, after the aging treatment, cold rolling (cold rolling after aging) can be performed at a working degree of 40% or more. Cold rolling after aging can impart processing strain to the material to increase strength.

If the workability of cold rolling after aging is less than 40%, it may be difficult to sufficiently increase the strength. The workability of cold rolling after aging is preferably 40 to 90%. If the processing degree exceeds 90%, the conductivity may decrease due to the processing strain of the strong processing.

The workability after cold rolling after aging refers to the rate of change of the thickness after cold rolling after aging with respect to the material thickness before cold rolling after aging.

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.

<Relaxation annealing>

Relaxation annealing was performed after cold rolling after aging. The relaxation annealing may be performed under ordinary conditions, and may be performed under conditions of, for example, 300 ° C. to 550 ° C. and a holding time of 5 seconds to 300 seconds. Thereby, a part of the inside of the material is removed to restore the ductility, so that the surface rolling can be used for shape correction. It is particularly desirable to set the ΔTS after relaxation annealing to 10 to 30 MPa. If the ΔTS is less than 10 MPa, the ductility cannot be sufficiently restored, and the surface rolling cannot be used for shape correction. When △ TS exceeds 30 MPa, the processability is good, but the TS may not reach 800 MPa due to the decrease in strength due to annealing.

Furthermore, △ TS (MPa) is expressed as (tensile strength TS (MPa) of the material before relaxation annealing)-(tensile strength TS (MPa) of the material immediately after relaxation annealing). Generally, △ TS> 0.

<Surface rolling>

The shape of the material is corrected by surface rolling with a working degree of 0.4 to 1.6% after relaxation annealing. If the workability of surface rolling is less than 0.4%, shape correction cannot be performed sufficiently, rolling strain remains, and flatness may not be improved. If the degree of processing exceeds 1.6%, the material will generate new strain by being exposed to a high pressure, and thus there may be cases where flatness cannot be improved.

<Final Relaxation Annealing>

Final relaxation annealing can also be performed after surface rolling. The final relaxation annealing can be performed under the same conditions as the relaxation annealing before the surface rolling described above, whereby the elasticity of the material which is reduced by the surface rolling can be restored.

[Example 1]

Samples of each example and each comparative example were prepared as follows.

Using electrolytic copper as a raw material, a copper alloy having a composition shown in Table 1 was melted and cast using an atmospheric melting furnace. This ingot was hot-rolled at 950 ° C. until the sheet thickness reached 10 mm. After hot rolling, grinding was performed to obtain a material with a width of 600 mm, and then cold rolling, solution treatment, and aging treatment were sequentially performed.

Then, post-ageing cold rolling was performed at the working degrees shown in Table 1 until the sheet thickness reached 0.152 mm. Furthermore, relaxation annealing was performed under the conditions (ΔTS) shown in Table 1, followed by surface rolling at the processing degree shown in Table 1, and then final relaxation annealing was performed to obtain a sample.

<Conductivity (% IACS)>

About the obtained sample, the electrical conductivity (% IACS) at 25 ° C. was measured in accordance with JIS H0505 and the 4-terminal method.

<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, using each sample, a test piece No. JIS13B was produced using a press so that the stretching direction was the rolling direction. The conditions of the tensile test were set as follows: a test piece width of 12.7 mm, room temperature (15 to 35 ° C), a tensile speed of 5 mm / min, and a gage length of 50 mm.

<Severity>

Regarding the obtained sample (600 mm width in the rolling direction and 1000 mm length in the rolling direction), according to JCBA-T326-2014, a non-contact 3-dimensional measuring machine was used, with the center portion in the rolling direction as the center, and The severity of the rolling direction was measured at a total of 5 points at a pitch of 25 mm.

Then, as described above, the deviation D between the mean value Av of the severity and the severity is calculated, and the deviation ratio DR of the severity is calculated as (Deviation of the severity D /) × 100 (%).

<Flatness during Lead Frame Processing>

Regarding the obtained sample (600 mm width in the rolling direction and 20 mm length in the rolling direction), as shown in FIG. 3, one surface of the sample was etched by an etching solution having a Baume degree of 47 and 40 ° C. A slit pattern with a lead length of 8 mm, a width of 0.25 mm, and a lead pitch of 0.5 mm was formed. The slit pattern is a plurality of leads LE arranged in a comb shape adjacent to each other in a rolling right angle direction, and simulates an inner lead portion of the lead frame.

Next, as shown in FIG. 4, the lead frame after the etching process is placed on the stage T with the etched surface facing upward, and the height HL of each lead LE from the stage T is measured from the direction in which the lead LE extends. 150% of the thickness t of the lead LE is specified as the standard height HS. When the length LR of the rolling right angle between the leads LE in the region where each height HL is continuously below HS is 550 mm or more, even if the lead frame is processed, It is also considered that the flatness of the lead frame is excellent.

The obtained results are shown in Table 1.

From Table 1, it can be seen that in the cases where the deviation rate of the severity is 12% or less, the tensile strength is 800 MPa or more, the average value of the severity is 0.5 or less, the deviation rate of the severity is 12% or less, the lead frame Excellent flatness during processing (after etching).

In the case of Comparative Example 1 in which the ΔTS during relaxation annealing is less than 10 MPa, the average value of the jerkiness exceeds 0.5, the deviation rate of the jerkiness exceeds 12%, and the flatness during processing of the lead frame is poor.

In the case of Comparative Example 2 in which the ΔTS during relaxation annealing exceeds 30 MPa, the tensile strength does not reach 800 MPa.

In the case of Comparative Example 3 where the surface rolling reduction exceeds 1.6%, the surface rolling delay is deformed, the severity exceeds 0.5, and the deviation of the severity exceeds 12%. Therefore, the flatness during processing of the lead frame is poor.

In the case of Comparative Example 4 where the workability of the surface rolling was less than 0.4%, the surface rolling was not sufficiently shape-corrected, so the urgency exceeded 0.5, and the deviation rate of the urgency exceeded 12%. Therefore, the flatness during processing of the lead frame is poor.

In the case of Comparative Example 5 where the workability of cold rolling after aging was less than 40%, the tensile strength did not reach 800 MPa.

In the case of Comparative Example 6 in which the contents of Ni and Si exceeded a predetermined range, the electrical conductivity did not reach 30% IACS.

In the case of Comparative Example 7 in which the contents of Ni and Si did not reach the predetermined range, the tensile strength did not reach 800 MPa.

In the case of Comparative Example 8 in which the total content of the additive elements exceeded 0.8% by mass, the electrical conductivity did not reach 30% IACS.

Claims (2)

    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, and the remainder containing Cu and unavoidable impurities, and having a conductivity of 30% IACS or more, stretched The strength is 800 MPa or more. When JCBA-T326-2014 is used to measure the severity of more than 5 points in the rolling direction orthogonal to the rolling direction at a distance of 25 mm or less, the average value of the above severity is 0.5 or less, and the deviation rate of the urgency expressed by (the deviation of the urgency / the average of the urgency) x 100 is 12% or less.         For example, the Cu-Ni-Si-based copper alloy bar according to item 1 of the patent application scope further contains one or more selected from the group consisting of Mg, Fe, P, Mn, Co, and Cr in a total amount of 0.005 to 0.8% by mass.