Metal treatment – Stock – Copper base
Reexamination Certificate
2001-04-10
2002-11-19
Ip, Sikyin (Department: 1741)
Metal treatment
Stock
Copper base
C148S682000, C420S476000
Reexamination Certificate
active
06482276
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a copper alloy suitable for a lead frame material, a terminal and/or connector material, a switch material, or the like, processed in a desired shape through a process including a punching step. Further the present invention relates to a method for manufacturing the copper alloy.
BACKGROUND OF THE INVENTION
Conventionally, a copper-series material with excellent electric and thermal conductivity, as well as iron-series material, is frequently employed for a lead frame material or a terminal material. Such a copper-series material is also employed for a semiconductor device member, whose heat radiation property has been important in accordance with the advancement of high integration and miniaturization of the semiconductor member.
When a copper-series material is used for a lead frame, the material must have excellent plating properties for precious metal (such as Ag or Pd) or solder, and surface smoothness, as well as electric and thermal conductivity.
Although a variety of lead frame copper alloys were developed to meet such requirements in the past, not many such copper alloys were satisfactory. Thus, only several types of the alloys are employed now. Among them, a Cu—Cr—Sn-series alloy is recognized as being compatible with high conductivity and high mechanical strength, so that it is one of the most frequently used alloys.
In the meantime, although a punching method or etching method is generally applied for lead frame mold processing, the punching method is frequently used from the standpoint of productivity.
However, with respect to the conventional Cu—Cr—Sn-series alloy, burring or generation of processing powder occurs during punching, that causes short-circuiting between leads or reduced dimensional precision of a lead frame. If burring occurs, the metal die maintenance cycle is made short, and the manufacturing cost increases. In particular, these problems are significant in a multi-pin type lead frame.
For a lead frame manufacturer, low-cost lead frames are demanded according to the fast-grow of semiconductor industry. Thus, they are important tasks how the rate of operation of punching facilities is raised, and how punch faults are decreased and product yields are increased. In particular, in the lead frame made of the Cu—Cr—Sn-series alloy, with its demand increased, significant improvement of punchability (punching processability) is strongly desired.
SUMMARY OF THE INVENTION
(1) A copper alloy with excellent punchability, comprising 0.2 to 0.35 wt % of Cr, 0.1 to 0.5 wt % of Sn, and 0.1 to 0.5 wt % of Zn, the balance being made of Cu and unavoidable impurities, wherein, in a Cu matrix, a precipitation phase A of Cr or a Cr compound of 0.1 to 10 &mgr;m in maximum diameter, is provided, at a density in number of 1×10
3
to 3×10
5
/mm
2
, and a precipitation phase B of Cr or a Cr compound of 0.001 to 0.030 &mgr;m in maximum diameter, is provided, at a density in number that is 10 times or more of that of the precipitation phase A (hereinafter, this copper alloy is referred to as a first embodiment of the present invention).
(2) A copper alloy with excellent punchability, comprising 0.2 to 0.35 wt % of Cr, 0.1 to 0.5 wt % of Sn, and 0.1 to 0.5 wt % of Zn, and further comprising at least one selected from the group consisting of 0.001 to 0.06 wt % of Pb, 0.001 to 0.06 wt % of Bi, 0.005 to 0.1 wt % of Ca, 0.005 to 0.1 wt % of Sr, 0.005 to 0.1 wt % of Te, 0.005 to 0.1 wt % of Se, and 0.005 to 0.1 wt % of a rare earth element, in a total amount of 0.001 to 0.1 wt %, the balance being made of Cu and unavoidable impurities, wherein, in a Cu matrix, a precipitation phase A of Cr or a Cr compound of 0.1 to 10 &mgr;m in maximum diameter, is provided, at a density in number of 1×10
3
to 3×10
5
/mm
2
, and a precipitation phase B of Cr or a Cr compound of 0.001 to 0.030 &mgr;m in maximum diameter, is provided, at a density in number that is 10 times or more of that of the precipitation phase A (hereinafter, this copper alloy is referred to as a second embodiment of the present invention).
(3) A copper alloy with excellent punchability, comprising 0.2 to 0.35 wt % of Cr, 0.1 to 0.5 wt % of Sn, 0.1 to 0.5 wt % of Zn, and 0.005 to 0.1 wt % of Si, the balance being made of Cu and unavoidable impurities, wherein, in a Cu matrix, a precipitation phase A of Cr or a Cr compound of 0.1 to 10 &mgr;m in maximum diameter, is provided, at a density in number of 1×10
3
to 3×10
5
/mm
2
, and a precipitation phase B of Cr or a Cr compound of 0.001 to 0.030 &mgr;m in maximum diameter, is provided, at a density in number that is 10 times or more of that of the precipitation phase A (hereinafter, this copper alloy is referred to as a third embodiment of the present invention).
(4) A copper alloy with excellent punchability, comprising 0.2 to 0.35 wt % of Cr, 0.1 to 0.5 wt % of Sn, 0.1 to 0.5 wt % of Zn, 0.005 to 0.1 wt % of Si, and further comprising at least one selected from the group consisting of 0.001 to 0.06 wt % of Pb, 0.001 to 0.06 wt % of Bi, 0.005 to 0.1 wt % of Ca, 0.005 to 0.1 wt % of Sr, 0.005 to 0.1 wt % of Te, 0.005 to 0.1 wt % of Se, and 0.005 to 0.1 wt % of a rare earth element, in a total amount of 0.001 to 0.1 wt %, the balance being made of Cu and unavoidable impurities, wherein, in a Cu matrix, a precipitation phase A of Cr or a Cr compound of 0.1 to 10 &mgr;m in maximum diameter, is provided, at a density in number of 1×10
3
to 3×10
5
/mm
2
, and a precipitation phase B of Cr or a Cr compound of 0.001 to 0.030 &mgr;m in maximum diameter, is provided, at a density in number that is 10 times or more of that of the precipitation phase A (hereinafter, this copper alloy is referred to as a fourth embodiment of the present invention).
(5) A method of manufacturing a copper alloy with excellent punchability as stated in any one of the above (1) to (4), by subjecting the copper alloy at least to a hot working and a cold working, wherein heat treatment is applied at a temperature of 880 to 980° C. before the hot working, and aging treatment is applied at a temperature of 360 to 470° C. before or after the cold working.
DETAILED DESCRIPTION OF THE INVENTION
Although the present invention relates to a copper alloy particularly suitable for a lead frame material, it is applicable to general materials manufactured in a process containing punching, such as a terminal material used for automobiles or a connector material used for commercially available equipment.
The copper alloy of the present invention is primarily characterized in that, in a Cu matrix, there coexist a precipitation phase A of coarse Cr or a Cr component of 0.1 to 10 &mgr;m in maximum diameter, for improving punchability, and a precipitation phase B of fine Cr or a Cr compound of 0.001 to 0.030 &mgr;m (1 nm to 30 nm) in maximum diameter, for ensuring mechanical strength. The maximum diameter referred to here means the diameter of a sphere when a precipitation phase is spherical; a long diameter when the phase is elliptical; and the maximum length when the phase is bar-shaped.
The inventors conducted research for a copper alloy-series and found out that an ideal precipitation state of Cr or a Cr compound can be achieved by specific amount of components and definition of manufacturing conditions, to obtain a copper alloy with excellent practicality.
The copper alloy of the present invention is preferably manufactured by subjecting it to heat treatment at 880 to 980° C. before hot working, to precipitate coarse Cr or a Cr compound, and further subjecting it to aging treatment at 360 to 470° C., to precipitate fine Cr or a Cr compound.
Now, reasons for defining alloy components of a copper alloy according to the present invention will be described.
Conventionally, when Cr was added into Cu, only precipitation and hardening of Cr were expected. The size of each of the precipitation phases of Cr or a Cr compound dispersing in the Cu matrix, was 0.001 to 0.030 &mgr;m in maximum diameter, and almost no coarse precipitati
Hirai Takao
Ohyama Yoshimasa
Usami Takayuki
Ip Sikyin
Knobbe Martens Olson & Bear LLP
The Furukawa Electric Co. Ltd.
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