U.S. patent application number 11/140425 was filed with the patent office on 2006-01-19 for copper-titanium alloys excellent in strength, conductivity and bendability, and method for producing same.
This patent application is currently assigned to Nikko Metal Manufacturing Co., Ltd.. Invention is credited to Takaaki Hatano, Chihiro Izumi.
Application Number | 20060011275 11/140425 |
Document ID | / |
Family ID | 35496792 |
Filed Date | 2006-01-19 |
United States Patent
Application |
20060011275 |
Kind Code |
A1 |
Izumi; Chihiro ; et
al. |
January 19, 2006 |
Copper-titanium alloys excellent in strength, conductivity and
bendability, and method for producing same
Abstract
The present invention provides a titanium copper alloy excellent
in strength, electrical conductivity and bendability, characterized
in that it consists essentially of 1.5 to 2.3% by mass of Ti,
balance Cu and inevitable impurities; said alloy having a 0.2%
yield strength of 750 MPa or greater; an electrical conductivity of
17% IACS or greater; and a relationship represented by the formula:
MBR/t.ltoreq.0.04.times.YS-30,in which, YS is a 0.2% yield strength
(MPa), and MBR/t is a ratio of a minimum bending radius (MBR; mm)
for no cracking when said alloy is subjected to W bend test
according to JIS H3130 standard along a transverse direction to a
rolling direction, to a thickness (t; mm) of test piece.
Inventors: |
Izumi; Chihiro;
(Kanagawa-ken, JP) ; Hatano; Takaaki;
(Kanagawa-ken, JP) |
Correspondence
Address: |
DRINKER BIDDLE & REATH;ATTN: INTELLECTUAL PROPERTY GROUP
ONE LOGAN SQUARE
18TH AND CHERRY STREETS
PHILADELPHIA
PA
19103-6996
US
|
Assignee: |
Nikko Metal Manufacturing Co.,
Ltd.
Kanagawa-ken
JP
|
Family ID: |
35496792 |
Appl. No.: |
11/140425 |
Filed: |
May 27, 2005 |
Current U.S.
Class: |
148/682 ;
148/411; 420/492 |
Current CPC
Class: |
C22F 1/08 20130101; C22C
9/00 20130101 |
Class at
Publication: |
148/682 ;
148/411; 420/492 |
International
Class: |
C22F 1/08 20060101
C22F001/08; C22C 9/00 20060101 C22C009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 1, 2004 |
JP |
2004-162934 |
Claims
1. A titanium copper alloy excellent in strength, electrical
conductivity and bendability, consisting essentially of 1.5 to 2.3%
by mass of Ti, balance Cu and inevitable impurities; said alloy
having a 0.2% yield strength of 750 MPa or greater; an electrical
conductivity of 17% IACS or greater; and a relationship represented
by the formula: MBR/t.ltoreq.0.04.times.YS-30, in which, YS is a
0.2% yield strength (MPa), and MBR/t is a ratio of a minimum
bending radius (MBR; mm) for no cracking when said alloy is
subjected to W bend test according to JIS H3130 standard along a
transverse direction to a rolling direction, to a thickness (t; mm)
of test piece.
2. The titanium copper alloy according to claim 1, having an
electrical conductivity of 20% IACS or greater.
3. The titanium copper alloy according to claim 1, having a 0.2%
yield strength of 800 MPa or greater.
4. The titanium copper alloy according to any one of the preceding
claims; said alloy having Cu--Ti intermetallic compound phases
observed in a cross section transverse to the rolling direction
whose diameters are 2.0 .mu.m or less; and an area ratio (S; %) of
Cu--Ti intermetallic compound phases observed in the cross section
transverse to the rolling direction whose diameters are 0.02 to 2.0
.mu.m may have a relationship with Ti content ([Ti]; % by mass)
represented by the formula:
8.1.times.[Ti]-11.5.ltoreq.S.ltoreq.7.5; and said alloy having an
average grain size of 2 to 10 .mu.m in the cross section transverse
to the rolling direction as measured by JIS H0501 standard
intercept method.
5. A method for producing from an ingot the titanium copper alloy
according to any one of claims 1 to 3, comprising sequential steps
of a hot rolling, a cold rolling, a solution treatment, a cold
rolling, and an aging treatment; a reduction ratio of said cold
rolling before said solution treatment being 89% or greater, a
heating temperature T (.degree. C.) for said solution treatment
being in a range represented by the formula:
[6580/{7.35-ln[Ti]}]-333.ltoreq.T.ltoreq.[6580/{7.35-ln[Ti]}]-273,
an average cooling rate in said solution treatment being
300.degree. C./s or greater, a reduction ratio of said cold rolling
before said aging treatment being 10 to 70%, a heating temperature
for said aging treatment being 350 to 450.degree. C., a heating
hold time for said aging treatment being 5 to 20 hours, and an
average cooling rate from the heating temperature for said aging
treatment being 10 to 50.degree. C./h.
6. A method for producing from an ingot the titanium copper alloy
according to claim 4, comprising sequential steps of a hot rolling,
a cold rolling, a solution treatment, a cold rolling, and an aging
treatment; a reduction ratio of said cold rolling before said
solution treatment being 89% or greater, a heating temperature T
(.degree. C.) for said solution treatment being in a range
represented by the formula:
[6580/{7.35-ln[Ti]}]-333.ltoreq.T.ltoreq.[6580/{7.35-ln[Ti]}]-273,
an average cooling rate in said solution treatment being
300.degree. C./s or greater, a reduction ratio of said cold rolling
before said aging treatment being 10 to 70%, a heating temperature
for said aging treatment being 350 to 450.degree. C., a heating
hold time for said aging treatment being 5 to 20 hours, and an
average cooling rate from the heating temperature for said aging
treatment being 10 to 50.degree. C./h.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to copper-titanium alloys
excellent in strength, electrical conductivity and bendability, and
to a method for producing the same.
BACKGROUND OF THE INVENTION
[0002] In accordance with the recent trend toward miniaturization
and lightening of electronic devices, miniaturization and
lightening (thinner thickness and finer pitch) of electric or
electronic components such as connector and the like are ongoing.
Since thinner thickness and finer pitch of connector lead to a
reduction in cross section area of contact part thereof, a decrease
in contact-pressure and electrical conductivity caused by the
decrease of cross section area needs to be compensated for. Metal
materials used for the contact part are thus required to have
higher strength and electrical conductivity. In addition, metal
materials used need to have good bendability as they will be
subjected to a severe bending work.
[0003] Recently, an increasing amount of age-hardening type copper
alloys has been used as high strength copper alloys. In
age-hardening type copper alloys, their strength is enhanced by an
aging treatment of supersaturated solid solution obtained by a
solution treatment to generate a uniform dispersion of fine
precipitates in them.
[0004] Among the age-hardening type copper alloys, copper alloy
containing Ti (hereinafter called "titanium copper alloy") is
widely used for a variety of terminals and connectors of electronic
devices since it possesses high strength and excellent bendability.
Titanium copper alloy currently available on an industrious scale
is based on JIS C1990, which contains 2.9 to 3.5% by mass of Ti.
This is because sufficient strength cannot be obtained when less
content of Ti is used, as indicated in working examples of JP
07-258803A and JP 2002-356726A, etc.
[0005] High beryllium copper alloy (JIS C1720) is also known as
age-hardening type high strength copper alloy as well as titanium
copper alloy. Titanium copper alloy has comparable strength and
bendability, and superior stress relaxation properties as compared
with the high beryllium copper alloy, so the former is more
appropriate than the latter for applications where higher thermal
resistance is required such as burn-in-socket, etc. On the
contrary, in terms of electrical conductivity, it is the current
state of the art that titanium copper alloy, which has 10 to 16%
IACS, is inferior to the high beryllium copper alloy, which has 20%
IACS. Accordingly, the high beryllium copper alloy is used in
applications where higher electrical conductivity is needed.
However, the high beryllium copper alloy has such problems that it
possesses toxicity and its production process is complicated and
costly. Therefore, an expectation for titanium copper alloy is
further increasing.
[0006] As dissolution of Ti in copper matrix causes a decrease in
electrical conductivity, the amount of dissolved Ti may be reduced
to increase electrical conductivity by precipitating Ti as Cu--Ti
intermetallic compound phases. JP 2004-285408A improves the
electrical conductivity of titanium copper alloy containing 2.5 to
4.5% by mass of Ti by adjusting the precipitation amount of Cu--Ti
intermetallic compound phases. However, according to the inventors'
research, the titanium copper alloy disclosed in the specification
exhibited significantly deteriorated bendability. As a reason for
this deterioration in bendability, it was confirmed that coarse
Cu--Ti intermetallic compound phases became starting points of
crack. In particular, bendability was significantly deteriorated
when there existed Cu--Ti intermetallic compound phases having a
diameter of greater than 2 .mu.m. Proper adjustment of grain size
and final rolling process may enable titanium copper alloy to
achieve both high strength and bendability at the same time as
disclosed in JP 2002-356726A, for example. However, no technology
has achieved well-balanced improvement in all of the strength,
bendability and electrical conductivity of titanium copper
alloy.
SUMMARY OF THE INVENTION
[0007] Therefore, it is an object of the present invention to
provide a titanium copper alloy excellent in strength, conductivity
and bendability.
[0008] The present inventors have conducted extensive research in
order to provide titanium copper alloy having electrical
conductivity comparable to the high beryllium copper alloy as well
as excellent strength and bendability. As a result, it was found
that titanium copper alloy having desired strength, bendability and
electrical conductivity can be obtained by adjusting Ti
concentration, Cu--Ti intermetallic compound phase size, area ratio
and average grain size to optimal ranges.
[0009] The present inventors have discovered that the bendability
deterioration in the titanium copper alloy disclosed in the
aforementioned JP 2004-285408 is due to coarse Cu--Ti intermetallic
compound phases precipitated in a large amount. According to the
present invention, smaller amount of coarse Cu--Ti intermetallic
compound phases may be precipitated by reducing Ti concentration.
Moreover, titanium copper alloy has been optimized in the structure
and the production process so that desired strength and bendability
at the reduced Ti concentration can be achieved.
[0010] (1) The present invention is directed to a titanium copper
alloy excellent in strength, electrical conductivity and
bendability, consisting essentially of 1.5 to 2.3% by mass of Ti,
balance Cu and inevitable impurities;
said alloy having a 0.2% yield strength of 750 MPa or greater; an
electrical conductivity of 17% IACS or greater; and a relationship
represented by the formula: MBR/t.ltoreq.0.04.times.YS-30, in
which, YS is a 0.2% yield strength (MPa), and MBR/t is a ratio of a
minimum bending radius (MBR; mm) for no cracking when said alloy is
subjected to W bend test according to JIS H3130 standard along a
transverse direction to a rolling direction, to a thickness (t; mm)
of test piece.
[0011] (2) The titanium copper alloy may have an electrical
conductivity of 20% IACS or greater.
[0012] (3) The titanium copper alloy may have a 0.2% yield strength
of 800 MPa or greater.
[0013] (4) The titanium copper alloy may have Cu--Ti intermetallic
compound phases observed in a cross section transverse to the
rolling direction whose diameters are 2.0 .mu.m or less; and an
area ratio (S; %) of Cu--Ti intermetallic compound phases observed
in the cross section transverse to the rolling direction whose
diameters are 0.02 to 2.0 .mu.m may have a relationship with Ti
content ([Ti]; % by mass) represented by the formula:
8.1.times.[Ti]-11.5.ltoreq.S.ltoreq.7.5; and the titanium copper
alloy may have an average grain size of 2 to 10 .mu.m in the cross
section transverse to the rolling direction as measured by JIS
H0501 standard intercept method.
[0014] (5) The titanium copper alloy may be produced from an ingot
by a production process comprising sequential steps of a hot
rolling, a cold rolling, a solution treatment, a cold rolling, and
an aging treatment;
a reduction ratio of said cold rolling before said solution
treatment being 89% or greater,
a heating temperature T (.degree. C.) for said solution treatment
being in a range represented by the formula:
[6580/{7.35-ln[Ti]}]-333.ltoreq.T.ltoreq.[6580/{7.35-ln[Ti]}]-273,
an average cooling rate in said solution treatment being
300.degree. C./s or greater,
a reduction ratio of said cold rolling before said aging treatment
being 10 to 70%,
a heating temperature for said aging treatment being 350 to
450.degree. C.,
a heating hold time for said aging treatment being 5 to 20 hours,
and
an average cooling rate from the heating temperature for said aging
treatment being 10 to 50.degree. C./h.
DETAILED DESCRIPTION OF THE INVENTION
[0015] (1) Electrical Conductivity
[0016] When materials are used for a variety of terminals and
connectors, an increase in their electrical conductivity leads to a
decrease in the amount of heat generated by energization. An
electrical conductivity of 17% IACS or greater is needed to achieve
heat generation as low as that achieved by the high beryllium
copper alloy. An electrical conductivity of 20% IACS or greater is
more preferable.
[0017] (2) 0.2% Yield Strength
[0018] When a 0.2% yield strength of materials used as connectors
becomes less than 750 MPa, it is not possible to obtain contact
resistance as low as that of the high beryllium copper alloy even
when their electrical conductivity is adjusted to 17% IACS or
greater. This is due to a decrease in contact pressure at an
electric contact, causing an increase of the contact resistance.
Consequently, a 0.2% yield strength of 750 MPa or greater is
needed. A 0.2% yield strength of 800 MPa or greater is more
preferable.
[0019] (3) Bendability
[0020] When materials are used for a variety of terminals and
connectors, the balance between 0.2% yield strength and bendability
is important. The present inventors have found a certain measure to
meet the requirements for connector materials after a quantitative
analysis of the relationship between 0.2% yield strength and
bendability required for recent electronic components with the use
of titanium copper alloys containing 1.5 to 2.3% by mass of Ti and
having conductivity of 17% IACS or greater. Specifically, a
titanium copper alloy having the following relationship may have
well-balanced strength and bendability, meeting the recent
requirements in this field. The relationship is represented by the
formula: MBR/t.ltoreq.0.04.times.YS-30,
in which:
YS is a 0.2% yield strength (MPa) and
MBR/t is a ratio of a minimum bending radius (MBR; mm) for no
cracking when said alloy is subjected to W bend test according to
JIS H3130 standard along a transverse direction to a rolling
direction, to a thickness (t; mm) of test piece.
[0021] (4) Ti Content
[0022] When titanium copper alloys undergo an aging treatment,
spinodal decomposition occurs to form a modulated structure of
titanium concentration in base metal, thereby very high strength
can be obtained. It is difficult to obtain a 0.2% yield strength of
750 MPa or greater in case where titanium copper alloys have a
titanium content of less than 1.5% by mass. On the other hand, when
titanium copper alloys have a titanium content of greater than 2.3%
by mass, coarse Cu--Ti intermetallic compound phases having a
diameter of greater than 2 .mu.m will precipitate in case where the
titanium copper alloys have been produced according to a condition
mentioned below under which an electrical conductivity of 17% or
greater can be obtained, thus deteriorating bendability of
material. The titanium copper alloy of the present invention
therefore is defined to have a titanium content of 1.5 to 2.3% by
mass, preferably 1.6 to 2.0% by mass.
[0023] By the way, titanium copper alloys having Ti concentration
in said range have never put to practical use. Though such alloys
have been reported in patent literatures, none of them has achieved
well-balanced improvements in all of the strength, bendability and
electrical conductivity. For example, JP 2002-356726 discloses in
the working example 1 an alloy containing 1.7% by mass of Ti. This
alloy has an electrical conductivity of 20.3% IACS, which is
comparable to that of the alloy according to the present invention.
However, its 0.2% yield strength is no more than 710 MPa. Moreover
JP 2002-356726 discloses in the examples 2 alloys each containing
1.5% and 2.3% by mass of Ti. Again, they failed to achieve
well-balanced improvements in both strength and electrical
conductivity because they have a 0.2% yield strength of 720 MPa and
1180 MPa, and an electrical conductivity of 26.4% IACS and 10.2%
IACS, respectively.
[0024] (5) Diameter of Cu--Ti Intermetallic Compound Phase
[0025] The amount of dissolved Ti can be reduced by precipitating
Ti as Cu--Ti intermetallic compound phase, thereby increasing
electrical conductivity of titanium copper alloys. However, when
the diameter of the minimum circle to surround any one piece of
Cu--Ti intermetallic phases (i.e., the maximum diameter of the
Cu--Ti intermetallic compound phases) observed in a cross section
transverse to a rolling direction exceeds 2.0 .mu.m, such phase may
become the cause of crack during a bending process carried out on
material, resulting in a decrease in bendability. Therefore Cu--Ti
intermetallic compound phases are preferably 2 .mu.m or less in
diameter.
[0026] (6) Area Ratio of Cu--Ti Intermetallic Compound Phase
[0027] It is important to generate a sufficient amount of Ti
precipitation and to reduce the amount of dissolved Ti as much as
possible so that titanium copper alloys can have higher electrical
conductivity. In other words, an increase in the precipitation
amount of Cu--Ti intermetallic compound phase leads to an increase
in electrical conductivity. Moreover, material may have higher
strength by precipitation of finer Cu--Ti intermetallic compound
phases.
[0028] The present inventors have found that titanium copper alloys
containing Ti in an amount ranging from 1.5 to 2.3% by mass can
achieve an electrical conductivity of 17% IACS or greater when it
meets the following relationship represented by the formula:
S.gtoreq.8.1.times.[Ti]-11.5: in which: the symbol S is an area
ratio (%) of the Cu--Ti intermetallic compound phases whose
diameters are 0.02 to 2.0 .mu.m observed in a cross section
transverse to a rolling direction; and [Ti] is a titanium content
(% by mass). The present inventors have also found that S exceeding
7.5% causes reduction in bendability, which makes it difficult to
maintain the balance between 0.2% yield strength and bendability as
defined by the present invention even if the precipitated Cu--Ti
intermetallic compound phases have diameters of 2.0 .mu.m or less.
Therefore, it is preferable that the area ratio S of Cu--Ti
intermetallic compound phases has a relationship represented by the
formula: 8.1.times.[Ti]-11.5.ltoreq.S.ltoreq.7.5. Moreover it has
been found that an electrical conductivity of 20% IACS or greater
can be obtained, while maintaining the relationship between 0.2%
yield strength and bendability as defined by the present invention
if the relationship 8.1.times.[Ti]-9.5.ltoreq.S.ltoreq.7.5 is
fulfilled with [Ti]=1.5 to 2.0% by mass.
[0029] (7) Average Grain Size
[0030] When an average grain size in a cross section transverse to
a rolling direction exceeds 10 .mu.m as measured by JIS H0501
standard intercept method, the strength of material cannot be
sufficiently improved by the mechanism of fine grain size, making
it difficult to achieve a 0.2% yield strength of 750 MPa or
greater. When the average grain size is adjusted to less than 2
.mu.m, non-recrystallized structure region may remain. The
remaining of non-recrystallized structure region has an adverse
effect on bendability of material. Therefore the titanium copper
alloy of the present invention preferably has an average grain size
of 2 to 10 .mu.m in a cross section transverse to a rolling
direction.
[0031] (8) Method for Production
[0032] The present inventors have found that titanium copper alloys
that meet the characteristics of the present invention can be
obtained through a production process comprising sequential steps
of melting and casting of a raw material, and a hot rolling, a cold
rolling, a solution treatment, a cold rolling and an aging
treatment on a resulting ingot, on condition that each of the cold
rolling before the solution treatment, the solution treatment, the
cold rolling after the solution treatment and the aging treatment
is appropriately adjusted. The specific conditions of the
abovementioned steps are discussed below.
[0033] Cold Rolling Before Solution Treatment
[0034] In recrystallization of material, strain introduced by a
cold rolling process can be nucleus for recrystallization. The
higher reduction ratio in the cold rolling before the solution
treatment can introduce more strain, which promotes formation of an
increasing number of recrystallization grains and restriction of
grain growth, resulting in finer grain size. An average grain size
of 10 .mu.m or less can be obtained by using a reduction ratio of
89% or greater in the cold rolling before the solution
treatment.
[0035] Solution Treatment
[0036] Solution treatment on titanium copper alloy is generally
carried out at a temperature equal to or greater than that where
solubility of Ti in Cu corresponds to the content of Ti. However,
solution treatment at this temperature range results in grain size
of 10 .mu.m or greater. The present inventors have determined by
experiment a heating temperature range for solution treatment to
steadily obtain grain size of 2 to 10 .mu.m. Specifically, if the
solution treatment is carried out at temperatures T (.degree. C.)
according to the formula: T>[6580/{7.35-ln[Ti]}]-273, grain size
would grow 10 .mu.m or greater, thus making it difficult to obtain
a 0.2% yield strength of 750 MPa or greater. On the contrary, if
the solution treatment is carried out at temperatures T (.degree.
C.) according to the formula: T<[6580/{7.35-ln[Ti]}]-273, grain
size would grow less than 2 .mu.m, thus deteriorating bendability
of material. If the solution treatment is carried out at
temperatures T (.degree. C.) according to the formula:
[6580/{7.35-ln[Ti]}]-333.ltoreq.T.ltoreq.[6580/{7.35-ln[Ti]}]-273,
a grain size of from 2 to 10 .mu.m can be obtained.
[0037] Moreover, if an average cooling rate from the heating
temperature to 25.degree. C. is less than 300.degree. C./s, Cu--Ti
intermetallic compound phases with diameters of greater than 2.0
.mu.m would precipitate on grain boundaries during the cooling of
material. This is apt to produce cracks in grain boundaries when a
bending stress is applied to material. Therefore, an average
cooling rate in the solution treatment is preferably 300.degree.
C./s or greater. The cooling method used here is not limited to any
particular methods but water-cooling method is generally
employed.
[0038] Reduction Ratio in Cold Rolling After Solution Treatment
[0039] When the reduction ratio in the cold rolling after the
solution treatment becomes less than 10%, an increase of strength
by work hardening cannot be expected, making it difficult to obtain
a 0.2% yield strength of 750 MPa or greater. Moreover, with such a
low reduction ratio, the precipitation rate of Ti--Cu intermetallic
compound phase decreases in the following aging treatment step
since strain introduced by the cold rolling process also decreases,
thus making it difficult to obtain an electrical conductivity of
17% IACS or greater. On the contrary, the reduction ratio over 70%
may decrease ductility, causing a significant deterioration in
bendability. Consequently, it becomes difficult to meet the
relationship between 0.2% yield strength and bendability defined in
the present invention. Therefore, the reduction ratio in the cold
rolling after the solution treatment is preferably 10 to 70%. In
order to obtain better relationship between 0.2% yield strength and
bendability, the reduction ratio of 40 to 65% is more
preferable.
[0040] Aging Treatment
In order to generate precipitation of Cu--Ti intermetallic compound
phase as defined in the present invention in the aging treatment,
the aging condition can be adjusted as follows, for example.
[0041] (1) Heating Temperature
[0042] When the heating temperature is less than 350.degree. C., a
0.2% yield strength of 750 MPa or greater and an electrical
conductivity of 17% IACS or greater cannot be obtained due to
insufficient precipitation of Cu--Ti intermetallic compound phase.
When the heating temperature is over 450.degree. C., strength and
bendability decreases due to coarsening of Cu--Ti intermetallic
compound phase. Therefore, the heating temperature is preferably
350 to 450.degree. C. The term "heating temperature" herein means
the temperature inside the furnace to heat material.
[0043] (2) Hold Time at Heating Temperature
[0044] When the hold time at the heating temperature is less than 5
hours, it is difficult to obtain an electrical conductivity of 17%
IACS or greater due to insufficient precipitation of Cu--Ti
intermetallic compound phase. When the hold time is over 20 hours,
strength and bendability decreases due to coarsening of Cu--Ti
intermetallic compound phase. Therefore, the hold time at the
heating temperature is preferably 5 to 20 hours. The term "hold
time" herein means time between when the material temperature
reaches the furnace temperature and when cooling is started.
[0045] (3) Average Cooling Rate
[0046] In the ageing treatment, precipitation of Cu--Ti
intermetallic compound phase does not occur in a sufficient amount
to obtain an electrical conductivity of 17% IACS or greater when an
average cooling rate from the heating temperature to 200.degree. C.
is faster than 50.degree. C./h. On the contrary, when the average
cooling rate is slower than 10.degree. C./h, precipitation of
Cu--Ti intermetallic compound phase significantly increases, which
causes the area ratio of Cu--Ti intermetallic compound phases
having diameters of 0.02 to 2.0 .mu.m to exceed 7.5%, resulting in
deterioration of bendability. Therefore, an average cooling rate
from the heating temperature to 200.degree. C. is preferably 10 to
50.degree. C./h.
[0047] The present invention can provide titanium copper alloys
that are excellent in strength, bendability and electrical
conductivity so that they can adapt to the recent trend toward
miniaturization and thinness in electronic devices
EXAMPLES
[0048] Melting and casting was carried out in a high-frequency
vacuum melting furnace using electrolytic cathode copper as raw
material to form various compositions of ingots (60 mm
width.times.30 mm thickness) as listed in Table 1, followed by a
hot rolling at 900.degree. C. to obtain a thickness of 8 mm. After
that, a cold rolling before a solution treatment, the solution
treatment, a cold rolling after the solution treatment, and an
aging treatment were conducted under the conditions listed in Table
1 to modify average grain size, Cu--Ti intermetallic compound phase
size, and area ratio. In the solution treatment, cooling was
initiated after holding the test piece temperature at the
designated temperature given in Table 1 for one minute. Cooling
process used here was air-cooling, Ar gas spray, water spray, or
immersion in water, and the amount of sprayed Ar gas and water was
varied to obtain different cooling rates. A thermocouple was welded
to the test piece so that cooling rate to 25.degree. C. (ambient
temperature) could be measured. In the aging treatment, cooling
rate was varied by controlling furnace temperature. Average cooling
rate for test piece was measured from the heating temperature to
200.degree. C.
[0049] 0.2% yield strength, electrical conductivity, bendability
(MBR/t), average grain size in a cross section transverse to a
rolling direction, and size and area ratio of Cu--Ti intermetallic
compound phase were evaluated for each alloy obtained through the
above mentioned method.
[0050] 0.2% yield strength was measured according to JIS Z2241
standard using a tensile test machine. Electrical conductivity was
measured by four-terminal method according to JIS H0505.
Bendability was evaluated as follows. A strip test piece 10 mm in
width and 50 mm in length was cut out with the longitudinal
direction of the specimen being a direction transverse to a rolling
direction (Bad way). W bend test (JIS H3130) was conducted on the
specimen at various bend radiuses to evaluate a ratio (MBR/t) of
minimum bend radius for no cracking (mm) to thickness (mm) of test
piece by comparing convex surface appearance of bent portion with
the evaluation standard according to JBMA T307: 1999 technical
standard by Japan Copper and Brass Association.
[0051] In the measurement of average grain size (.mu.m), it was
determined according to the intercept method (JIS H0501 standard).
The cross section transverse to a rolling direction was etched
using water (100 mL)/FeCl.sub.3 (5 g)/HCl (10 mL), and observed the
crystal grains by a scanning electron microscope.
[0052] Observation of Cu--Ti intermetallic compound phases
precipitated in alloy was made by the use of FE-SEM (XL30SFEG, FEI
Company Japan Ltd.). Material was subjected to abrasion on its
cross section transverse to a rolling direction using #150
waterproof abrasive paper, followed by mirror-polish with a
finish-polishing agent in which colloidal silica having a diameter
of 40 nm was suspended. The resulting specimen was then subjected
to carbon evaporating. Backscattered electron images having a field
of view of 100 .mu.m.sup.2 at a magnification of 1000.times. were
observed in different 5 fields of view for each alloy. The diameter
of the minimum circle that can surround each Cu--Ti intermetallic
compound phase present within the observation field of view and
area ratio were then determined by the use of an image analysis
system. In evaluation of Cu--Ti intermetallic compound phase size,
alloy was evaluated as "Yes" if it contains Cu--Ti intermetallic
compound phase having a diameter of greater than 2.0 .mu.m, and
evaluated as "No" if it contains no Cu--Ti intermetallic compound
phase having a diameter of greater than 2.0 .mu.m. In evaluation of
area ratio, area ratio was defined as the total area of Cu--Ti
intermetallic compound phases having a diameter of 0.02 to 2.0
.mu.m divided by the total area of observation field of view.
[0053] Table 2 shows the evaluation result for each alloy. Any
alloy of Examples 1 to 10 fulfilled Ti content, grain size, Cu--Ti
intermetallic compound phase size and area ratio defined by the
present invention, and exhibited an electrical conductivity of 17%
IACS or greater and a 0.2% yield strength of 750 MPa or greater,
the relationship between 0.2% yield strength and MBR/t also within
the range defined by the present invention. In particular, alloys
of Examples 2, 4, 7 and 10, which had a Ti content of 1.5 to 2.0%
by mass and area ratio S of intermetallic compound phases
satisfying the formula 8.1.times.[Ti]-11.5.ltoreq.S.ltoreq.7.5,
exceed an electrical conductivity of 20% IACS. In addition, alloys
of Examples 2 and 5, which had a Ti content of 1.6 to 2.0% by mass
with the reduction ratio of the cold rolling after the solution
treatment of 40 to 65%, exhibited better bendability (MBR/t)
compared with that of other Examples having similar 0.2% yield
strength, while exhibiting higher 0.2 yield strength compared with
that of other Examples having similar bendability.
[0054] On the contrary, the alloy of Comparative Example 11 cannot
achieve a 0.2% yield strength of 750 MPa or greater due to the too
low Ti concentration.
[0055] In Comparative Example 12, coarse Cu--Ti intermetallic
compound phases with a size of 2.0 .mu.m or greater are
precipitated due to the too high Ti concentration. The alloy cannot
achieve bendability defined by the present invention since it had
the area ratio of Cu--Ti intermetallic compound phases beyond the
range defined by the present invention.
[0056] In Comparative Example 13, the average grain size after the
solution treatment exceeds 10 .mu.m with a 0.2% yield strength less
than 750 MPa due to the low cold rolling reduction ratio before the
solution treatment.
[0057] The alloy of Comparative Example 14 cannot achieve
bendability defined by the present invention since the solution
treatment was carried out at a lower temperature than the range
defined by the present invention and thus non-recrystallized
structure region remains, and moreover, both the Cu--Ti
intermetallic compound phase size and the area ratio exceed the
range defined by the present invention.
[0058] The alloy of Comparative Example 15 had the average grain
size of greater than 10 .mu.m, and cannot achieve a 0.2% yield
strength of 750 MPa or greater when the aging treatment was carried
out under the condition which gives an electrical conductivity of
17% IACS or greater. This is due to the solution treatment
temperature, which was beyond the range defined by the present
invention.
[0059] The alloy of Comparative Example 16 cannot achieve
bendability defined by the present invention since the average
cooling rate is so slow that coarse Cu--Ti intermetallic compound
phases having a size of 2.0 .mu.m or greater are precipitated.
[0060] In Comparative Example 17, a 0.2% yield strength of 750 MPa
or greater cannot be achieved due to the too low cold rolling
reduction ratio after the solution treatment. An electrical
conductivity of 17% IACS or greater cannot be also achieved since
the precipitation rate in the aging treatment was so slow that the
area ratio of Cu--Ti intermetallic compound phases was below the
range defined by the present invention.
[0061] The alloy of Comparative Example 18 cannot achieve
bendability defined by the present invention due to the too high
cold rolling reduction ratio after the solution treatment.
[0062] In Comparative Example 19, a 0.2% yield strength of 750 MPa
or greater cannot achieved due to the insufficient aging caused by
the too low heating temperature in the aging treatment. An
electrical conductivity of 17% IACS or greater cannot be also
achieved since the area ratio of Cu--Ti intermetallic compound
phases was below the range defined by the present invention.
[0063] In Comparative Example 20, the relationship between 0.2%
yield strength and bendability defined by the present invention is
not fulfilled since the heating temperature in the aging treatment
is so high that coarsening of Cu--Ti intermetallic compound phases
is occurred due to overaging.
[0064] The alloy of Comparative Example 21 cannot achieve an
electrical conductivity of 17% IACS or greater since the heating
hold time in the aging treatment is so short that the area ratio of
Cu--Ti intermetallic compound phases is below the range defined by
the present invention.
[0065] In Comparative Example 22, the relationship between 0.2%
yield strength and bendability defined by the present invention is
not fulfilled since the heating hold time in the aging treatment is
so long that coarsening of Cu--Ti intermetallic compound phases is
occurred due to overaging.
[0066] The alloy of Comparative Example 23 cannot achieve an
electrical conductivity of 17% IACS or greater since the average
cooling rate in the aging treatment is so fast that the area ratio
of Cu--Ti intermetallic compound phases is below the range defined
by the present invention.
[0067] The alloy of Comparative Example 24 cannot achieve
bendability defined by the present invention since the average
cooling rate in the aging treatment is so slow that the area ratio
of Cu--Ti intermetallic compound phases is beyond the range defined
by the present invention. TABLE-US-00001 TABLE 1 Production
conditions Solution treatment Reduction Possible heating Reduction
Aging treatment ratio before temperature range Actual ratio after
Hold time at Ti content solution according to the Heating Average
solution Heating heating Average (% by treatment present invention
temperature cooling rate treatment temperature temperature cooling
rate No. mass) (%) (.degree. C.) * 1 (.degree. C.) (.degree. C./s)
(%) (.degree. C.) (h) (.degree. C./h) Exmples 1 2.21 90.5
671.about.731 705 350 35 430 8 37 2 1.87 94.3 646.about.706 689 416
40 390 10 20 3 1.50 98.1 615.about.675 658 650 18 350 20 45 4 2.00
96.5 658.about.718 704 704 33 450 8 33 5 1.77 89.2 638.about.698
685 541 43 400 5 18 6 2.08 94.2 661.about.721 700 912 67 380 12 40
7 1.52 97.3 616.about.676 670 634 24 410 10 27 8 1.66 95.8
629.about.689 678 419 13 370 15 36 9 2.30 91.9 677.about.737 710
617 30 420 7 48 10 1.58 96.6 622.about.682 650 568 52 400 5 16
Comparative 11 1.25 95.1 590.about.650 629 498 44 390 12 41
examples 12 2.62 97.4 697.about.757 738 749 29 420 5 34 13 2.03
86.0 658.about.718 698 579 27 400 10 17 14 2.21 93.7 671.about.731
650 666 48 370 20 26 15 1.72 98.0 634.about.694 750 908 37 440 6 31
16 1.54 96.6 618.about.678 659 150 32 380 12 22 17 1.69 94.8
631.about.691 662 764 5 440 8 13 18 1.98 92.2 654.about.714 707 497
80 430 10 41 19 2.17 95.9 668.about.728 710 815 15 335 20 12 20
1.83 92.7 642.about.702 690 394 62 460 5 48 21 1.51 97.1
615.about.675 666 517 40 400 3 10 22 1.96 91.6 652.about.712 692
618 27 410 35 47 23 2.28 94.6 675.about.735 705 807 33 450 10 100
24 1.91 96.5 649.about.709 677 555 30 380 8 5 * 1: [6580/[7.35 -
In[Ti]}] - 333 .ltoreq. T .ltoreq. [6580/[7.35 - In[Ti]}] - 273
[0068] TABLE-US-00002 TABLE 2 Properties of produced alloys Area
ratio of Cu--Ti intermetallic Existence of compound phase; S (%)
Average Cu--Ti intermetallic Possible range 0.2% Yield Bendability
* 2 Electrical Grain compound phase according to Strength 0.04
.times. MBR/t of conductivity size exceeding the present Measured
No. (MPa) YS - 30 test piece (% IACS) (.mu.m) 2.0 .mu.m diameter
invention * 3 value Examples 1 852 4.1 3.0 19.6 6.2 No
6.4.about.7.5 6.8 2 855 4.2 1.8 20.7 4.3 No 3.6.about.7.5 6.5 3 767
0.7 0 17.2 2.1 No 0.6.about.7.5 1.3 4 811 2.4 1.6 22.8 7.2 No
4.7.about.7.5 7.1 5 845 3.8 1.7 18.8 5.1 No 2.8.about.7.5 3.9 6 890
5.6 4.8 18.7 9.8 No 5.3.about.7.5 6.2 7 773 0.9 0 20.4 3.9 No
0.8.about.7.5 4.9 8 792 1.7 0.6 17.9 2.5 No 1.9.about.7.5 2.8 9 875
5.0 3.9 18.4 8.4 No 7.1.about.7.5 7.3 10 814 2.6 1.4 20.2 3.3 No
1.3.about.7.5 5.8 Comparative 11 715 0 0 20.5 4.8 No 0.about.7.5
0.4 examples 12 830 3.2 5.9 18.1 8.2 Yes 7.5 or greater 9.4 13 735
0 0 19.4 15.7 No 4.9.about.7.5 5.2 14 853 4.1 8.4 19.6 Not
recrystallized Yes s 10.1 15 729 0 0.5 18.2 24.4 No 2.4.about.7.5
2.6 16 771 0.8 2.4 18.6 2.9 Yes 1.0.about.7.5 2.5 17 692 0 0 15.4
5.9 No 2.2.about.7.5 1.1 18 897 5.9 8.7 21.4 7.1 No 4.5.about.7.5
7.8 19 730 0 0 14.3 9.7 No 6.1.about.7.5 3.4 20 721 0 1.2 22.6 4.2
Yes 3.3.about.7.5 8.9 21 774 1.0 0.6 15.9 2.3 No 0.7.about.7.5 0.3
22 733 0 1.4 21.1 3.7 Yes 4.4.about.7.5 8.4 23 825 3.0 2.1 16.2 5.2
No 7.0.about.7.5 6.4 24 835 3.4 4.1 21.6 2.8 No 4.0.about.7.5 7.9 *
2: MBR/t .ltoreq. 0.04 .times. YS - 30 * 3: 8.1 .times. [Ti] - 11.5
.ltoreq. S .ltoreq. 7.5
[0069] Equivalents
[0070] Although the particular embodiments of the present invention
are described expressly by the specification and appended claims of
the present application, those embodiments are illustrative and not
restrictive. As one of ordinary skill in the art can readily
appreciate many variations from the disclosure of the present
invention, such variations are also included in the present
invention. The scope of the present invention should be defined by
the appended claims and inclusive of its equivalents.
* * * * *