JP2002363667A - Copper alloy having excellent hot workability and machinability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a copper alloy in which the generation of intergranular cracking on hot working can be prevented, and which has excellent machinability in the surface. SOLUTION: The copper alloy has a composition containing, by weight, 1.8 to 2.5% Fe, 0.001 to 0.1% P, 0.01 to 1.0% Zn and 0.02 to 0.1% Sn, and the balance Cu with inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper alloy having excellent hot workability and machinability, and more particularly to a copper alloy capable of preventing generation of grain boundary cracks during hot working and having excellent surface machinability. Copper alloy.

[0002]

2. Description of the Related Art Conventionally, as a copper alloy used for a lead frame or a connector terminal of a semiconductor device,
Copper containing 1.8-2.5% by weight of Fe, 0.001-0.1% by weight of P, and 0.01-1.0% by weight of Zn, the balance being Cu and unavoidable impurities Alloys are known.

[0003] Usually, the following procedure is performed to manufacture a processed product such as a lead frame from this copper alloy. First, a copper alloy having the above composition is heated to form a molten metal, which is cast continuously or semi-continuously to produce an ingot.
A hot-rolled sheet having a thickness of about 10 mm is formed by hot rolling at a high temperature of 00 to 1000 ° C, and immediately cooled with water.

[0004] Next, after the obtained hot-rolled sheet is chamfered to remove oxide scale, cold rolling, aging heat treatment and surface polishing are repeatedly performed, followed by final rolling and strain-relieving annealing. After forming an alloy strip having a thickness of 3 mm, the alloy strip is subjected to press working, bending work, and the like, and is subjected to plating to obtain a predetermined processed product. This copper alloy has excellent properties in terms of strength and conductivity, and is therefore considered to be an optimal material particularly as a component for a lead frame for forming a semiconductor device.

[0005]

However, according to the conventional copper alloy of this type, there is a problem that an edge portion is apt to cause grain boundary cracking called edge cracking during hot rolling. In the case of severe grain boundary cracking, the rolling operation may be stopped if it is severe. It often appears as a defect, and therefore, this ear cracking phenomenon is regarded as an important problem that cannot be allowed in performing the rolling operation and ensuring quality.

According to a conventional copper alloy having the above composition,
In surface cutting after hot rolling, there is also a problem that the machinability is inferior, and therefore, it has a drawback of shortening the tool life of the face mill, and it is easy to leave a peeling residual portion due to this. It also has quality issues.

Accordingly, it is an object of the present invention to provide a copper alloy which can prevent the occurrence of grain boundary cracks during hot working and has excellent surface machinability.

[0008]

According to the present invention, 1.8 to 2.5% by weight of Fe and 0.1% by weight of P are used in order to achieve the above object.
001 to 0.1% by weight, 0.01 to 1.0% by weight of Zn, and 0.02 to 0.1% by weight of Sn, with the balance being Cu and unavoidable impurities. An object of the present invention is to provide a copper alloy excellent in characteristic hot workability and machinability.

[0009] The precipitation-type copper alloy to which the present invention is directed has the property that an alloy element that does not form a solid solution in copper precipitates in crystal grains or at crystal grain boundaries. The compound of Fe and P precipitated at the crystal grain boundaries serves as a resistance component of grain boundary slip during hot working, and thus acts as a main cause of lowering hot workability to generate grain boundary cracks. I do. In addition, a coarse compound of Fe and P having a particle size of 1 μm or more, which is one of the precipitates in the crystal grains, has a higher rigidity than the parent phase and is less likely to be deformed. Act on.

On the other hand, in the case of the copper alloy of the present invention,
By adding Sn, the precipitation of the compound of Fe and P at the grain boundary is suppressed, and further, the precipitation of the coarse compound of Fe and P in the crystal grain is suppressed, and the fine precipitate of Fe is crystallized. It has the property of precipitating uniformly within the grains. As a result, the hot workability and the machinability after hot working are guaranteed, and a high-quality copper alloy can be provided. For this purpose, the content of each component is an important factor. Hereinafter, the reason for adding each component and the reason for setting the content will be described.

[0011] Fe is added to improve strength and heat resistance by precipitating it in Cu, and at least 1.8% by weight is required to make this function sufficient. . On the other hand, if the amount exceeds 2.5% by weight, coarse crystals of Fe are formed during casting, causing bending cracks or plating swelling, and the conductivity is greatly reduced. Therefore, F
The content of e needs to be limited to 1.8 to 2.5% by weight. More preferable Fe content is 2.
It can be set to 0 to 2.3% by weight.

P is mixed in as a deoxidizing component for removing oxygen mixed in the molten metal when the copper alloy is melted and cast. At the lower limit, the content is set to obtain a sufficient deoxidizing effect, and at the upper limit, excess P
In order to prevent core cracks due to precipitation at the crystal grain boundaries and the like, or grain boundary cracks during hot working,
It is set to 0.001 to 0.1% by weight. Note that the upper limit of this range is also a boundary value at which the deoxidizing effect is saturated. A more preferable P content for obtaining the above effects is 0.1.
It is set to be 0.01 to 0.04% by weight.

Zn has a deoxidizing and degassing effect and Cu
Has an effect of suppressing the migration of the compound, and at least 0.01% by weight is required to make these effects effective. The upper limit is 1.0
It is necessary to set the weight%, and if it exceeds this, it is necessary to avoid the conductivity since the conductivity is lowered. As a more preferable range, it can be set to 0.05 to 0.2% by weight.

The precipitation of the compound of Fe and P at the crystal grain boundaries is suppressed, and the precipitation of the same compound in the crystal grains is prevented so that the content of Sn, which causes fine and uniform precipitation of Fe, is set at 0.1%. The reason for limiting the amount to 02 to 0.1% by weight is 0.02%.
When the content is less than 0.1% by weight, it is insufficient to secure these effects. Conversely, when the content is more than 0.1% by weight, the decrease in conductivity becomes remarkable and the core cracks easily occur during casting. It depends. In order to enhance the above-described effects to a higher level, it is preferable to set the Sn content to 0.05 to 0.08% by weight. In addition, in addition of Sn,
There is a secondary effect of improving strength, heat resistance and stress relaxation characteristics.

[0015] In the copper alloy of the present invention, the addition of Si in addition to the above components is a preferred embodiment. Si
Has the property of refining the cast structure of the copper alloy of the present invention, and therefore, its addition is called grain boundary cracking at the center of the ingot, which is caused by tensile stress at the time of casting, so-called core. This is effective in suppressing the occurrence of cracks.

The preferred Si content is 0.001 to
If it is within the range of 0.05% by weight, and if it is less than 0.001% by weight, it is difficult to obtain a sufficient effect for refining the cast structure and thereby preventing the core cracking. In addition, the amount of slag at the time of melting and casting increases, leading to clogging of a nozzle or roughening of an ingot, and the likelihood of lowering the conductivity increases. More preferable Si content is 0.005 to
It can be set to 0.02% by weight.

[0017]

Next, an embodiment of a copper alloy excellent in hot workability and machinability according to the present invention will be described. Electrolytic copper was melted at 1200 ° C. in a medium-frequency crucible-type melting furnace under a charcoal coating in the air, and P was added to perform deoxidation to obtain a P-deoxidized copper melt, which is shown in Table 1. The components of Examples, Comparative Examples and Conventional Examples were adjusted by adding each element.

Next, the molten metal is cast semi-continuously through a casting gutter coated with charcoal into an ingot having a sectional size of 230 mm × 460 mm. After that, the temperature was set to 950 ° C. and the rolling reduction per pass was set to about 20%, and hot rolling was performed to produce a hot-rolled sheet having a thickness of 12 mm. Next, the upper and lower surfaces of the hot rolled sheet were each 0.7
After cutting by 5 mm each to make a thickness of 10.5 mm, this plate was repeatedly subjected to rolling and annealing to form a copper alloy strip having a thickness of 0.2 mm.

Table 1 shows the presence or absence of core cracks in the cross section of the ingot, the average grain size of the ingot, the density of grain boundary precipitates in the ingot, the elongation at break of the ingot in the high-temperature tensile test, and the heat. Table 2 shows the presence or absence of edge cracks during cold rolling and the presence or absence of peeling off during surface grinding. Table 2 also shows the electrical conductivity, tensile strength, softening temperature, and stress of a 0.2 mm thick copper alloy strip. Indicates the relaxation rate. The evaluation of each of these characteristics was performed as follows.

Presence / absence of core cracks: The ingot was cut to a thickness of 2 mm, and the cut surface was cut to a thickness of 1 mm.・ Average particle size: After examining the number of crystals per unit area, calculate the radius of the spherical crystal from the reciprocal,
This radius was defined as the average particle size. -Grain boundary precipitate density: Calculated as the number of grain boundary precipitates per unit length by observing the cross-sectional structure.

High-temperature tensile test: A JIS No. 14A test piece was used, the diameter of the parallel portion was 10 mm, and the test was performed at 900 ° C. and in an Ar atmosphere. -Presence / absence of peeling: Facing was performed under the same operating conditions of the facing machine, and the surface after facing was observed. Softening temperature: When the sample was heated, the heating temperature at which 80% of the tensile strength before heating was maintained was taken as the softening temperature. Stress relaxation rate: Stress relaxation rate after standing for 100 hours under the conditions of a stress load of 400 N / mm 2 and a temperature of 150 ° C.

[0022]

[Table 1]

According to Table 1, the copper alloys according to the examples show a low density of grain boundary precipitates, and therefore have a high level of elongation at break in a high-temperature tensile test, and have an edge crack (a grain boundary crack) during hot rolling. ), The copper alloy according to the conventional example has a high grain boundary precipitate density, and therefore has a small elongation at break at high temperatures, so that ear cracks occur during hot rolling. Is recognized.

[0024] In addition, in terms of the surface machinability, in the case of the embodiment, complete chamfering was completed, whereas in the case of the conventional example, the remaining unpeeled portion was left. There is a clear difference between them. These differences are caused by the presence or absence of Sn, and the effect of adding Sn in the present invention is remarkable.

However, the effect of the addition of Sn increases as the content increases, but if the content exceeds the specified amount according to the present invention, the ingot may cause a core crack in the ingot as in Comparative Example 2. Need to be avoided. In addition, it is necessary to avoid setting the content to be low, and if this is not maintained, the characteristics of the grain boundary precipitate density and the elongation at high temperature rupture will be insufficient as in Comparative Example 1, and the hot work based on these will be insufficient. Sufficient results cannot be obtained in rolling workability and surface facing workability.

Table 1 clearly demonstrates why the present invention limits the Sn content to a specific range. In addition, Comparative Example 2 did not generate edge cracks during hot rolling and peeling residue during surface facing, but in the subsequent annealing step,
The occurrence of surface swelling and peeling has been confirmed. .

[0027]

[Table 2] Table 2 shows that the copper alloy strip obtained by the example of the present invention
It indicates that the copper alloy according to the present invention has sufficient performance in various properties including electric conductivity, and that the copper alloy according to the present invention has sufficient practicality from these properties. Is recognized.

In Table 1, it is noteworthy that Example 3 containing Si as an additive component exhibited an average crystal grain size of the ingot of 1/10 or less of that of the other examples. The presence of Si is a result of the refinement of the cast structure, which means that the core cracks in the center of the ingot due to tensile stress during casting are suppressed. In implementing the present invention, based on the above facts, S
An embodiment in which i is added is preferable.

[0029]

As described above, according to the copper alloy of the present invention, 1.8 to 2.5% by weight of Fe, 0.00
1 to 0.1% by weight of P and 0.01 to 1.0% by weight of Z
n, an alloy composition comprising 0.02 to 0.1% by weight of Sn, the balance of Cu and unavoidable impurities to provide a copper alloy excellent in hot workability and machinability, Its usefulness is great.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koichi Kotoku 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi Cable, Ltd. General Research Laboratory 5F067 EA04 5G301 AA08 AA09 AA19 AA20 AA23 AA30 AB20 AD03 AD05

Claims (3)

[Claims] (1) 1.8-2.5% by weight of Fe and 0.0% of P
0.01 to 0.1% by weight, 0.01 to 1.0% by weight of Zn,
And Sn in an amount of 0.02 to 0.1% by weight, with the balance being C
A copper alloy excellent in hot workability and machinability, characterized by having an alloy composition of u and unavoidable impurities. 2. The copper alloy having excellent hot workability and machinability according to claim 1, wherein said alloy composition contains an appropriate amount of Si. 3. The method according to claim 1, wherein the content of said Si is 0.001 to 0.001.
The copper alloy having excellent hot workability and machinability according to claim 2, wherein the content is set within a range of 0.05% by weight.