JP2001158927A - Copper alloy excellent in hot workability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a copper alloy free from the generation of casting cracks and cracks at hot working and moreover excellent in mechanical properties and heat resistance. SOLUTION: This copper alloy contains, by weight, 1.8 to 2.3% Fe, 0.01 to 0.1% P, 0.05 to 1.0% Zn, 0.05 to 0.3% Sn, 4 to 100 ppm C, and the balance Cu.

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 more particularly to a Cu--Fe based copper alloy which does not crack during hot working.

[0002]

2. Description of the Related Art Conventionally, as a copper alloy used for electronic parts such as lead frames of semiconductor devices or electric parts such as terminals and connectors, Fe is contained in an amount of 1.5 to 3% by weight, and 0.01% by weight. 0.1% by weight of P and 0.03%
There is known a copper alloy containing 1% by weight of Zn, the balance being an alloy composition composed of Cu and unavoidable impurities, and having both excellent strength and conductivity.

[0003] In this Cu-Fe-based alloy, it is said that excellent strength and conductivity can be obtained when the content of Fe is 1.5 to 3% by weight. %, The Fe-based crystallites tend to become large when Fe is present in excess of 0.1%. Therefore, it is common practice to set the amount of Fe to 1.5 to 2.3% by weight. is there.

[0004] Usually, the following procedure is performed to manufacture a lead frame or the like from this copper alloy. First, a raw material is melted so as to have the above-mentioned composition, a molten metal of a copper alloy is adjusted, and this is cast continuously or semi-continuously to produce an ingot. A hot rolled sheet is manufactured by hot rolling at a high temperature.

[0005] Next, after the produced hot-rolled sheet is water-cooled and face-milled, cold rolling, aging heat treatment and surface polishing are repeatedly performed, and the final rolling and strain relief annealing are performed to obtain a copper alloy. The strip is manufactured, and thereafter, the copper alloy strip is subjected to metal working such as pressing, punching, bending, or the like, and is subjected to plating to obtain a predetermined lead frame, terminal, connector, or the like.

[0006]

However, according to the conventional copper alloy of this kind, there is a problem that a crack is easily generated at an edge portion of a hot-rolled material during casting or hot rolling. . Once a hot-rolled material that has cracked ears has a built-in defect caused by grain boundary cracking during hot working, even if the cracked edge is removed after processing into a copper alloy strip For this reason, when a lead frame is manufactured using such a copper alloy strip, there is a possibility that breakage of the lead during punching or bending, or cracking or plating swelling during the heat treatment stage may occur frequently.

Accordingly, an object of the present invention is to provide a copper alloy excellent in hot workability which can prevent casting cracks and edge cracks during hot working. Another object of the present invention is to provide a copper alloy having improved mechanical properties and heat resistance and excellent hot workability as compared with a conventional Cu-Fe alloy.

[0008]

According to the present invention, 1.8 to 2.3% by weight of Fe and 0.
01-0.1% by weight, Zn is 0.05-1.0% by weight,
0.05 to 0.3% by weight of Sn and 4 to 100% of C
An object of the present invention is to provide a copper alloy excellent in hot workability, characterized in that it contains ppm by weight and the balance consists of a Cu alloy.

Generally, in continuous or semi-continuous casting of a copper alloy or the like, the inside of the ingot except for a few mm is solidified in a gradually cooled form. For this reason, in the cooling process after solidification, the alloy element exceeding the limit and solid-solubilized is precipitated in the crystal grain boundaries and crystal grains.

On the other hand, the solid solution of Fe in Cu of a Cu-Fe alloy at room temperature is 0.3% or less, and therefore, for example, Cu-2.3% Fe-0.03% P- 0.12%
In the case of a copper alloy of Zn, not more than 2% of Fe precipitates in the crystal grain boundaries and in the crystal grains.
When a large amount of is precipitated, it is difficult for the grain boundary to slip at a high temperature, so that the high temperature strength of the grain boundary is deteriorated and cracks occur during hot working.

According to the present invention, by adding a specific alloying element in a specific amount, a crystal grain of a cast structure is refined, and precipitation of Fe at a crystal grain boundary is suppressed. It improves the hot workability by improving the medium and high temperature strength and the medium to high temperature brittleness, and also improves the properties in terms of mechanical properties and heat resistance. State the basis for setting the amount.

[0012] Fe has a function of improving the strength and heat resistance by dissolving and precipitating in Cu, and at least 1.8% by weight is required to obtain a material sufficient for this function. Also, if the amount exceeds 2.3% by weight,
The Fe particles that crystallize or precipitate during casting become huge,
This leads to problems such as deterioration of metal workability such as press working, deterioration of the obtained lead frame at the time of soldering, and swelling of plating. Therefore, the amount of Fe added is
It is limited to 1.8 to 2.3% by weight. A more preferable addition amount can be set to 1.9 to 2.2% by weight.

[0013] P is mixed in for deoxidation when the copper alloy is melted and cast. The addition amount is 0.01 to 0 in order to obtain a sufficient deoxidizing effect at the lower limit and to maintain the deoxidizing effect at the upper limit and to maintain conductivity and workability at the upper limit. .1% by weight. A more preferable addition amount is 0.02 to
0.05% by weight.

Zn has a deoxidizing and degassing effect, Cu
Has the effect of suppressing migration due to the formation of migration, and in order to obtain these effects, at least 0.05% by weight is required. Further, the upper limit value must be set to 1.0% by weight, and if it exceeds this value, the conductivity is reduced, so that it is necessary to avoid it. A more preferable range can be set to 0.08 to 0.2% by weight.

[0015] Sn is incorporated for improving strength and heat resistance as a solid solution in Cu and dispersing crystallization of Fe particles during casting. For these purposes, at least 0.05% by weight is required, while the addition amount is 0.3%.
If the content exceeds the weight percentage, the mixing effect is saturated and the conductivity is reduced. A more preferable Sn content is 0.1 to 0.2% by weight.

C has the effect of reacting with Fe in the molten metal to form Fe—C particles that serve as crystal nuclei, thereby reducing the size of the cast structure. , The content must be set to 4 to 100 ppm by weight. When the amount of C is less than 4 ppm by weight, the above-mentioned effect cannot be obtained. On the contrary, when the amount of C exceeds 100 ppm by weight, coarse Fe-C particles of 0.01 mm or more are formed. Become. More preferable C amount is 5 to 5
It can be set in the range of 0 ppm by weight.

The copper alloy according to the present invention naturally contains impurities which are inevitably mixed, and other components can be added as long as the object of the present invention is not impaired.

[0018]

Next, an embodiment of a copper alloy excellent in hot workability according to the present invention will be described. Electrocopper is shielded from the atmosphere by coating with carbon powder, melted in a low-frequency induction melting furnace, and then subjected to component adjustment by adding elements other than C shown in Table 1, and then coated with carbon powder. The amount of C shown in Table 1 was contained in the melted alloy using low frequency induction stirring.

[0019]

[Table 1]

Next, each of these melts is cast into a mold through a casting gutter coated with carbon powder, and the thickness thereof is set to 1 mm.
50mm, width 450mm, and length 3500mm
After producing these copper alloy ingots, they were hot-rolled at a temperature of 950 ° C. to produce a hot-rolled sheet having a thickness of 11 mm. The hot rolling operation requires a rolling reduction of about 18 per pass.
%, And conditions were set such that the final rolling temperature was 650 ° C. or lower.

Next, the upper and lower surfaces of the hot-rolled sheet thus obtained are chamfered into a sheet having a thickness of 10 mm, and the sheet is cold-rolled to be rolled to a thickness of 2 mm. An aging heat treatment at 1 ° C. for 1 hour was performed. Next, the oxide film is removed from the surface of the heat-treated plate,
Next, cold rolling is performed to obtain a sheet material having a thickness of 0.8 mm, and then final rolling is performed at a reduction ratio of 75% to obtain a sheet material having a thickness of 0.2 mm.
Was obtained.

Table 1 shows the state of occurrence of cracks, the crystal structure, and the characteristics of the finished alloy strip during hot rolling in the examples and comparative examples. The observation of cracks was performed for each rolling pass, and the number of passes in which the cracks occurred was displayed. The average crystal grain size and the maximum Fe crystallization size in the table are 1 point for 3 points near the surface in the cross section of the copper alloy ingot and 3 points at the center in the cross section (same in each example). The observation area per point was set to 20 mm × 20 mm, and the crystal structure was observed and the result of measurement was shown. The softening temperature was a test temperature at which the Vickers hardness after heating was 90% of the Vickers hardness before heating when the sample was heated at a predetermined test temperature for 5 hours.

According to Table 1, it is clear that in Examples 1 to 4, Sn and C
In Comparative Example 1 containing no Sn, cracks occurred at the edge of the hot-rolled sheet in the third pass, and in Comparative Example 2 containing no Sn, cracks occurred in the second pass. are doing. Furthermore, in the case of Comparative Example 3 in which the content of C is less than the range limited by the present invention and Comparative Example 4 not containing C, edge cracks and surface cracks occurred in the first and third passes. And collapsed on the fifth and fourth passes, respectively.

The difference in the hot workability is due to the crystal structure, and Examples 1 to 4 having excellent hot workability were found to have a small average crystal grain size of 3 mm or less and 0.01 mm
Compared to having the following fine Fe crystallization dimensions, Comparative Examples 1 to 4 show significantly larger values,
This difference in crystal structure appears as a difference in hot workability. In addition, between Examples 1 to 4 and Comparative Examples 1 and 2, a large difference is observed in mechanical properties of tensile strength and elongation, and a remarkable difference is also observed in a softening temperature indicating heat resistance.

In the case of Comparative Examples 5 and 6, in which Sn and C are contained in amounts exceeding the limits specified by the present invention, both show good hot workability. However, when these are compared with Examples 1 to 4, Comparative Example 5 is significantly inferior in tensile strength, elongation and electrical conductivity, while Comparative Example 6
Is extremely coarse in Fe crystallization size,
The mechanical properties of tensile strength and elongation are also inferior, and especially the elongation properties are remarkably low.

As shown in Table 1, the copper alloy of the present invention, which contains Fe, P, Zn, Sn and C at the same time and is established by setting the respective contents within a specific range, has an average of 3 mm or less. Grain size and F of 0.01mm or less
e Prevent cracking of the hot-rolled sheet at the time of hot working by making it a fine cast structure having a crystallized dimension,
In the alloy strip obtained through hot working and cold working, 53
0 N / mm2 or more tensile strength, 4.5% or more elongation, 6
It provides electrical conductivity of 6% IACS or more and softening temperature characteristics of 430 ° C. or more, and has characteristics that are optimal as raw materials for lead frames and the like.

[0027]

As described above, according to the copper alloy of the present invention, 1.8 to 2.3% by weight of Fe and 0.01% by weight
0.1% by weight of P and 0.05% to 1.0% by weight of Zn
And 0.05 to 0.3% by weight of Sn, 4 to 100% by weight of C, and a balance of Cu, whereby copper having excellent hot workability, mechanical properties and heat resistance is obtained. It provides an alloy, and is very useful for electrical components such as connectors and terminals for electronic components such as transistors and lead machines for integrated circuits.

Claims (3)

[Claims] (1) 1.8 to 2.3% by weight of Fe and 0.0% of P
1 to 0.1% by weight, 0.05 to 1.0% by weight of Zn, S
n is 0.05 to 0.3% by weight, and C is 4 to 100%.
A copper alloy excellent in hot workability, characterized in that it contains ppm by weight and has a composition consisting of Cu and inevitable impurities. 2. The hot workability according to claim 1, wherein the casting having the composition has an average crystal grain size of 3 mm or less and a Fe crystallization size of 0.01 mm or less. Excellent copper alloy. 3. The copper alloy strip having the above-mentioned composition is 530 N /
mm2 tensile strength, 4.5% elongation, 66% I
The copper alloy excellent in hot workability according to claim 1, wherein the copper alloy has a conductivity of ACS or higher and a softening temperature of 430 ° C or higher.