JP2010126783A - Copper alloy sheet or strip for electronic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copper alloy sheet or strip, which hardly causes a deformation of a lead in a lead frame and requires a short period of time for stress relief annealing after press working. <P>SOLUTION: The copper alloy sheet or strip for an electronic material has a composition including 0.02-3.0 mass% in total of one or more additive elements selected from the group consisting of Cr, Zn, Sn, Zr, Fe, P, Mg, Mn, Al and Co, and the balance Cu with unavoidable impurities. The residual stress of the sheet or strip at a position 1 &mu;m deep from the surface is 50 MPa or lower by the absolute value, and the tensile strength is lowered by 40 MPa or more by the heat treatment of heating the sheet or strip at a temperature of 500&deg;C for one minute. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a copper alloy plate or strip for electronic materials, and more particularly to a Cu-Cr-based or Cu-Fe-P-based alloy plate or strip suitable as a lead frame material.

  The lead frame is a thin metal plate used as an internal wiring of a semiconductor device. As a lead frame material, a copper alloy is often used instead of a conventional Fe-based material (Fe-42% Ni or the like) from the viewpoint of conductivity and heat dissipation. Copper alloys used in lead frames are excellent in repeated bendability, press workability, etching properties, solderability, flatness, plating properties, etc. in addition to the basic properties of high strength and high electrical conductivity. Is required.

  Typical examples of copper alloys for lead frames include Cu-Cr alloys and Cu-Fe-P alloys, examples of which are given below.

Japanese Patent Application Laid-Open No. 52-85920 (Patent Document 1) describes that the coexistence of Fe and P improves the strength, and further improves the stress corrosion cracking resistance. : A copper alloy containing 0.02 to 0.50 wt%, P: 0.01 to 0.1 wt%, with the balance being essentially Cu, having excellent stress corrosion cracking resistance and high strength (Claim 1).
According to claim 2 of the document, as a method for producing the copper alloy, a casting containing Fe: 0.02 to 0.50 wt%, P: 0.01 to 0.1 wt%, and the balance being essentially Cu. After the ingot is hot-rolled, it is cooled from 700 ° C. to room temperature (however, the cooling rate between 700 ° C. and 450 ° C. is 25 ° C./min or more), and further cold worked, then 350 to 550 It describes a method characterized in that the final annealing is carried out at 5 ° C. for 5 minutes to 180 minutes.

Japanese Patent Laid-Open No. 2007-177274 (Patent Document 2) discloses a copper alloy in which Mg is further added to a Cu—Fe—P alloy to improve the strength and the bending workability is not deteriorated. It is described that the crystal grains of the structure are refined and the variation of the individual crystal grain sizes is suppressed. Specifically, in mass%, Fe: 0.01-3.0%, P: 0.01-0.4%, Mg: 0.1-1.0%, respectively, the balance copper and unavoidable Alloy consisting of mechanical impurities, the crystal grain size measured by the crystal orientation analysis method with a backscattered electron diffraction image system mounted on a field emission scanning electron microscope, the following average crystal grain size is 5 μm or less, and the following average crystal A copper alloy having high strength and excellent bending workability, characterized in that the standard deviation of the particle diameter is 1.5 μm or less is described (claim 1).
In claim 9 of this document, as a method for producing the copper alloy, a copper alloy sheet is obtained by a process including copper alloy casting, hot rolling, cold rolling, recrystallization annealing, precipitation annealing, and cold rolling. The end temperature of the hot rolling is 550 ° C. to 850 ° C., the cold rolling rate in the subsequent cold rolling is 70 to 98%, and the average temperature increase rate in the subsequent recrystallization annealing is 50 ° C./s or more. A method is described in which the subsequent average cooling rate is set to 100 ° C./s or more, and the cold rolling rate in the subsequent cold rolling is set to a range of 10 to 30%.

In JP-A-10-287939 (Patent Document 3), an appropriate amount of a predetermined alloy element is contained, and the size of crystallized matter or precipitate and the crystal grain size are appropriately controlled, whereby lead frame materials and terminals are provided. A copper alloy for electrical and electronic equipment has been described that maintains properties such as strength and conductivity required for electrical and electronic equipment materials such as materials and improved punchability.
Specifically, it contains 0.1 to 0.4 wt% of Cr, less than 0.2 wt% (including 0 wt%) of Zr, 0.002 to 0.2 wt% of rare earth elements, and one of Pb and Bi A total of 0.002 to 0.2 wt% of the above, the balance being made of Cu and inevitable impurities, the size of crystallized substances and precipitates is less than 3 μm, and the grain size is less than 20 μm A copper alloy for electrical and electronic equipment having excellent workability is described (claim 1).
In paragraph 0014 of the document, as a method for producing the copper alloy, a molten copper alloy adjusted to a predetermined component is cast at a cooling rate of 5 ° C./second or more to obtain an ingot, which is heated at a temperature of 800 to 1000 ° C. Hot working, the obtained hot work material is rapidly cooled at a cooling rate of 10 ° C./second or more, and then subjected to cold working and annealing treatment at a temperature of 350 to 600 ° C. for 30 seconds to 6 hours at least once. A method is described in which after repeated application, cold working is performed at a working rate of 60% or less.

Japanese Patent Laid-Open No. 2001-181757 (Patent Document 4) discloses that the punching workability is improved by coexisting a coarse precipitate phase A and a fine precipitate phase B of Cr or Cr compound in a Cu matrix. Are listed.
Specifically, a copper alloy containing 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 the balance being Cu and inevitable impurities In the Cu matrix, the precipitated phase A of Cr or Cr compound having a maximum diameter of 0.1 to 10 μm is present at a number density of 1 × 10 ^{3 to} 3 × 10 ⁵ pieces / mm ² , and A copper alloy having excellent punchability, wherein the precipitation phase B of Cr or Cr compound having a maximum diameter of 0.001 to 0.030 μm is present at a number density of 10 times or more the number density of the precipitation phase A Is described.

  In claim 5 of this document, at least hot working and cold working are performed as a method for producing the copper alloy, heat treatment is performed at a temperature of 880 to 980 ° C. before the hot working, and before the cold working. Or the method characterized by performing an aging treatment at the temperature of 360-470 degreeC later is described.

JP-A-2005-113180 (Patent Document 5) discloses a CrSi compound having a predetermined size and number density in a Cu matrix in order to ensure etching processability while improving press punching processability. It is described that it is finely precipitated and limits the size of Cr compounds other than CrSi.
Specifically, Cr includes 0.1 to 0.25 wt%, Si includes 0.005 to 0.1 wt%, Zn includes 0.1 to 0.5 wt%, Sn includes 0.05 to 0.5 wt%, In a copper alloy consisting of the balance copper and unavoidable impurities in a Cr / Si weight ratio of Cr / Si in the range of 3-25, a CrSi compound having a size of 0.05 μm to 10 μm is 1 × in the copper matrix. An electron excellent in etching workability and punching workability, characterized by having a number density of 10 ^{3 to} 5 × 10 ⁵ pieces / mm ² and having a Cr compound other than the CrSi compound having a size of 10 μm or less. A copper alloy for equipment is described (claim 1).

  In claim 3 of the document, as a method for producing the copper alloy, a Cu—Cr—Si—Zn—Sn alloy ingot, or the Cu—Cr—Si—Zn—Sn—Zr alloy ingot is added to 850 to 980. A method is described in which a hot working is performed after heating at a temperature of ° C., and then cold rolling and a heat treatment at a temperature of 400 to 600 ° C. are repeated.

In JP-A-7-258805 (Patent Document 6), Ti and Fe are added to a Cu—Cr—Zr alloy, or one or two of Zn, Sn, In, Mn, P, Mg, or Si are added. In addition to adding more than seeds, the raw material is a copper alloy in which the content ratio of each component is strictly adjusted, and the crystal grain size is controlled by regulating the solution treatment conditions, and further cooling under specific conditions is performed. When cold working, aging, final cold working and final annealing are performed, materials with improved properties such as strength, electrical conductivity, bending workability, spring characteristics, Ag plating properties, and solder joint reliability are obtained. (Paragraph 0009).
In the first aspect, Cr: 0.05 to 0.40%, Zr: 0.03 to 0.25%, Fe: 0.10 to 1.80%, Ti: 0.00. 10 to 0.80%, and “0.10% ≦ Ti ≦ 0.60%” satisfies the Fe / Ti weight ratio of 0.66 to 2.6, and “0.60% <Ti ≦ 0.80% ”, a copper alloy material satisfying an Fe / Ti weight ratio of 1.1 to 2.6 with the balance being Cu and inevitable impurities. 1) Solution at a temperature below 950 ° C. 2) Cold working at a working degree of 50-90%, 3) Aging treatment at a temperature of 300-580 ° C., 4) Cold working at a working degree of 16-83%, 5) 350- A method for producing a high-strength, high-conductivity copper alloy material for electronic equipment is described, which is characterized by sequentially performing annealing at a temperature of 700 ° C. in this order. 5) is strain relief annealing, and it is described that after the final cold working, the spring property is improved and the ductility is restored.

JP 2003-286527 A (Patent Document 7) has a purpose of providing copper or a copper alloy having sufficient dimensional accuracy and shape characteristics when the copper or copper alloy is heat-treated at its annealing temperature. The copper or copper alloy is characterized by having a shrinkage ratio of 0.01% or less before and after the heat treatment, and having a plate shape and a steepness (parameter indicating flatness) of 0.5% or less. (Claim 1).
As a manufacturing process of the copper or copper alloy, after rolling to the final plate thickness in the same manner as general copper and copper-based alloys, if necessary, correct the shape with a tension leveler, etc., and then perform low-temperature annealing with a continuous annealing furnace However, it is described that the in-furnace tension is set in the range of 1.0 to 8.5% of the 0.2% proof stress of the material before passing through the continuous annealing furnace (paragraph 0020). ).
JP 52-85920 A JP 2007-177274 A Japanese Patent Laid-Open No. 10-287939 JP 2001-181757 A JP-A-2005-113180 JP 7-258805 A JP 2003-286527 A

With the progress of high integration and miniaturization of semiconductor devices, the level of demand for copper alloys used as materials for lead frames is becoming higher. When forming a lead frame with a fine pitch (for example, about 200 pins), the width and pitch of the inner lead part are extremely narrow, so that they are easily affected by residual stress during press working (punching) and lead deformation is likely to occur. . Therefore, conventionally, after the copper alloy plate or strip is pressed, strain relief annealing for removing the residual stress has been performed for the purpose of ensuring the flatness of the inner lead.
However, since the strain relief annealing after the press working occupies a large proportion in the lead frame lead time, a material having a short time required for the strain relief annealing is desirable.

  Accordingly, it is an object of the present invention to provide a copper alloy plate or strip that does not easily cause lead deformation of a lead frame and that requires a short time for strain relief annealing after press working.

  The present inventor has made extensive studies to solve the above problems, and has a certain degree of strength even after the residual stress on the surface is removed by strain relief annealing performed in the final manufacturing stage of the copper alloy plate or strip. The present inventors have found that the material is advantageous for solving the above problems. It has been found that when a lead frame is manufactured using this material, lead deformation is unlikely to occur, and strain relief annealing after press working can be performed in a short time.

  In one aspect, the present invention completed based on the above knowledge is a total of one or more additive elements selected from the group consisting of Cr, Zn, Sn, Zr, Fe, P, Mg, Mn, Al, and Co. A copper alloy plate or strip for an electronic material having a composition comprising 0.02 to 3.0% by mass and the balance being Cu and inevitable impurities, and the absolute value of the residual stress at a depth of 1 μm from the surface is 50 MPa. It is a copper alloy plate or strip that has a tensile strength that is reduced by 40 MPa or more by a heat treatment that is performed at a temperature of 500 ° C. for 1 minute.

In one embodiment, a copper alloy plate or strip according to the present invention is a copper alloy plate or strip for electronic materials having a composition shown in any one of 1) to 4) below, at a depth of 1 μm from the surface: It is a copper alloy plate or strip whose absolute value of residual stress is 50 MPa or less and whose tensile strength is reduced by 40 MPa or more by heat treatment heated at a temperature of 500 ° C. for 1 minute.
1) Cr: 0.1 to 0.5% by mass, balance Cu and unavoidable impurities 2) Cr: 0.1 to 0.5% by mass, Si, Zn, Sn And one or more selected from the group consisting of Zr up to a total of 1.0% by mass, a composition consisting of the balance Cu and inevitable impurities 3) Fe: 0.02-3.0% by mass, 4: Fe: 0.02-3.0 mass%, P: 0.02-0.15 mass% containing P: 0.02-0.15 mass% and consisting of remainder Cu and inevitable impurities And further containing one or more selected from the group consisting of Ni, Mg, Mn, Zn and Sn up to 1.0% by mass in total, and the composition consisting of the balance Cu and inevitable impurities

  In another embodiment of the copper alloy sheet or strip according to the present invention, the difference in tensile strength before and after the heat treatment heated at a temperature of 500 ° C. for 1 minute is 40 to 100 MPa.

  In still another embodiment of the copper alloy plate or strip according to the present invention, the average particle size of the second phase particles having a particle size in the range of 10 to 1000 nm is 20 to 200 nm.

  In still another embodiment of the copper alloy plate or strip according to the present invention, the tensile strength (TS) is 400 to 650 MPa, preferably 500 to 650 MPa.

  In still another embodiment of the copper alloy plate or strip according to the present invention, the copper alloy plate or strip described above has a 0.2% proof stress of 350 to 600 MPa, preferably 450 to 600 MPa.

  In yet another embodiment of the copper alloy plate or strip according to the present invention, the electronic material is a lead frame.

  In the case of conventional materials, when residual stress is removed by strain relief annealing performed at the final stage of the copper alloy sheet or strip manufacturing process, the flatness and other properties are improved, but the strength falls, and in this state, pressing is performed. As a result, deformation such as twisting was likely to occur in the lead portion. However, the newly developed material has good punchability because it retains high strength even during press working.

  In addition, the newly developed material can shorten the time required for strain relief annealing performed for flattening the lead frame after press working, compared to the conventional material. In other words, the degree of strength reduction when the strain relief annealing is performed under the same conditions increases.

In one aspect, the copper alloy according to the present invention includes one or more additive elements selected from the group consisting of Cr, Zn, Sn, Zr, Fe, P, Mg, Mn, Al, and Co in a total of 0. 0.02 to 3.0% by mass, and the composition consists of the balance Cu and inevitable impurities.
Cr, Zn, Sn, Zr, Fe, P, Mg, Mn, Al, and Co cannot obtain a desired strength if their total content is too low, while high strength can be achieved if their total content is too high. The conductivity is insufficient. Therefore, the total content of these additive elements is 0.02 to 3.0 mass%, preferably 0.02 to 2.0 mass%, more preferably 0.02 to 1.5 mass%. .

  The strengthening mechanism varies depending on the above elements. Sn, Zn, Mg, P, Mn and Al are solid solution types, and Cr, Zr, Fe and Co are aging precipitation types. In the solid solution type, the solute atoms dissolve in the crystal and the surrounding atomic arrangement is disturbed, and the elastic strain field and the electron distribution state are disturbed. Strengthened. In the case of the aging precipitation type, by aging the supersaturated solid solution that has been subjected to solution treatment, fine intermetallic compound particles of each additive element are uniformly dispersed, the strength of the alloy is increased, and at the same time, the solid solution in copper The amount of elements is reduced and electrical conductivity is improved. For this reason, a material excellent in mechanical properties such as strength and spring property and having good electrical conductivity and thermal conductivity can be obtained.

  The absolute value of the residual stress at a depth of 1 μm from the surface, which is a feature of the copper alloy plate or strip according to the present invention, is 50 MPa or less, and the tensile strength is 40 MPa by heat treatment heated at a temperature of 500 ° C. for 1 minute. The characteristic of lowering can be expressed regardless of whether it is an aging precipitation type or a solid solution type, and the composition is not particularly limited. However, Cu—Cr alloys and Cu—Fe—P alloys are not limited to the present invention. This is an exemplary embodiment and will be described in detail below.

  Cu-Cr-based and Cu-Fe-P-based alloys are a kind of precipitation-hardening type copper alloys, and by aging treatment of solution-treated supersaturated solid solutions, Cr-based, Fe-based and P-based fine metals, respectively. The intermetallic particles are uniformly dispersed, the strength of the alloy is increased, and at the same time, the amount of the solid solution element in the copper is reduced and the electrical conductivity is improved. For this reason, a material excellent in mechanical properties such as strength and spring property and having good electrical conductivity and thermal conductivity can be obtained.

Composition of Cu-Cr alloy (Cr)
Cr dissolves in Cu and suppresses the coarsening of crystal grains during solution treatment. Also, the alloy strength is raised. When Cr alone or Si is added during the aging treatment, silicide is formed and deposited, which can contribute to improvement in strength and conductivity. However, if the added amount of Cr is too small, the desired strength cannot be obtained, and if it is too large, a high strength can be achieved, but the electrical conductivity is remarkably lowered, and the hot workability is also lowered. Further, when Cr is added in a large amount, the melting temperature becomes high, and Cr that is not solid-solved in copper is not preferable because it causes surface defects during pin holes and Ag plating. Therefore, the Cr content is 0.1 to 0.5% by mass. The content of Cr is preferably 0.15 to 0.4 mass%, more preferably 0.2 to 0.4 mass%.

(Si, Zn, Sn and Zr)
The Cu-Cr alloy further contains one or more selected from the group consisting of Si, Zn, Sn, and Zr up to 1.0% by mass, preferably up to 0.5% by mass. be able to.

Si combines with Cr to form Cr—Si based metal compound particles. Fine Cr—Si-based metal compound particles improve press workability. However, if the addition amount is small, the effect cannot be obtained. On the other hand, if the addition amount is large, Si dissolved in the Cu matrix increases and the conductivity decreases, so it is necessary to add up to 0.1% by mass. Preferably, 0.005 to 0.1% by mass is added, more preferably 0.01 to 0.1% by mass.
Zn has an effect of suppressing solder embrittlement. However, since the electrical conductivity decreases when the addition amount is large, it is preferable to add up to 0.5% by mass, more preferably 0.1 to 0.5% by mass, and 0.2 to 0.5% by mass. It is even more preferable to add%.
Sn contributes to improvement in strength. However, the conductivity decreases significantly as the amount increases. Therefore, Sn is preferably added up to 0.5% by mass, more preferably 0.05 to 0.5% by mass, and even more preferably 0.1 to 0.5% by mass.
Zr precipitates during the aging treatment and has a function of improving strength while suppressing a decrease in conductivity. However, if the amount is increased, the conductivity is significantly lowered. Therefore, Zr is preferably added up to 0.2% by mass, more preferably 0.005 to 0.2% by mass, and even more preferably 0.005 to 0.1% by mass.

Composition of Cu-Fe-P alloy (Fe)
Fe is subjected to an appropriate heat treatment to form single Fe or Fe—P-based metal compound particles, and can be increased in strength without deteriorating conductivity. In particular, Fe—P-based metal compound particles formed by bonding with P have a high strength improving effect. However, if the added amount of Fe is too small, the desired strength cannot be obtained, and if it is too large, high strength can be measured, but the electrical conductivity is remarkably lowered, and the hot workability is also lowered. Therefore, the Fe content is 0.02 to 3.0 mass%. The content of Fe is preferably 0.02 to 2.0 mass%, more preferably 0.05 to 2.0 mass%.

(P)
In addition to having a deoxidizing action, P combines with Fe to form Fe—P-based metal compound particles, and can increase the strength without deteriorating the electrical conductivity. However, since the desired strength cannot be obtained if the amount of P is too large or too small, the P content is 0.02 to 0.15% by mass. The content of P is preferably 0.02 to 0.08% by mass, more preferably 0.02 to 0.05% by mass.

  There are several types of Fe—P-based metal compounds, and it is said that Fe: P = 3: 1 or 2: 1 (atomic ratio). Therefore, favorable electrical conductivity can be obtained preferably by adding Fe / P = 2 to 3 in atomic ratio. If the ratio is higher than the above ratio, the conductivity tends to decrease, and if the ratio is lower than the above ratio, coarse particles are likely to crystallize, and hot workability tends to deteriorate.

(Ni, Mg, Mn, Zn and Sn)
The Cu-Fe-P alloy further contains one or more selected from the group consisting of Ni, Mg, Mn, Zn and Sn up to 1.0% by mass, preferably 0.5% by mass. % Can be contained.

  Ni forms Ni—P-based metal compound particles by performing an appropriate heat treatment, and can increase the strength without deteriorating the electrical conductivity. However, if the amount of Ni added is too small, the desired strength cannot be obtained. If it is too large, high strength can be measured, but the electrical conductivity is remarkably lowered, and the hot workability is lowered. Therefore, the Ni content is 0.1 to 1.0% by mass. The content of Ni is preferably 0.2 to 1.0 mass%, more preferably 0.2 to 0.8 mass%.

  There are several types of Ni-P-based metal compounds, and it is said that Ni: P = 3: 1, 5: 2, or 12: 5 (atomic ratio). Therefore, preferable electrical conductivity can be obtained by setting Ni / P = 2 to 3 in atomic ratio. If it is higher than these ratios, the conductivity tends to decrease, and if it is lower, coarse particles tend to crystallize and the hot workability tends to deteriorate.

  Since Mg and Mn react with O, the deoxidizing effect of the molten metal is obtained. In general, it is an element added as an element for improving the alloy strength. The most famous effect is the improvement of stress relaxation characteristics, so-called creep resistance. In recent years, with the high integration of electronic devices, a high current flows, and in a semiconductor package with low heat dissipation such as a BGA type, the material may be deteriorated by heat, which causes a failure. In particular, when mounted on a vehicle, there is a concern about deterioration due to heat around the engine, and heat resistance is an important issue. For these reasons, it is an element that may be positively added. However, if the amount added is too large, the adverse effect on bending workability cannot be ignored. Therefore, it is preferable to add one or both of Mg and Mn to 1.0% by mass in total, more preferably 0.01 to 1.0% by mass, and 0.01 to 0.5% by mass added. Even more preferably.

  Zn has an effect of suppressing solder embrittlement. However, since the electrical conductivity decreases when the addition amount is large, it is preferable to add up to 1.0% by mass, more preferably 0.01 to 1.0% by mass, and 0.01 to 0.8% by mass. It is even more preferable to add%.

  Sn has the same effect as Mg. However, unlike Mg, the amount dissolved in Cu is large, so it is added when more heat resistance is required. However, the conductivity decreases significantly as the amount increases. Therefore, Sn is preferably added up to 0.5% by mass, more preferably 0.05-0.5% by mass, and even more preferably 0.05-0.3% by mass.

Residual stress In the present invention, the residual stress of the copper alloy is defined. Residual stress is the stress that exists in the material without external force or thermal gradient. Residual stress occurs as a result of non-uniform deformation due to heat treatment or cold working. If residual stress remains, it becomes difficult to obtain a flat strip or plate. If the flatness is impaired, the dimensional accuracy when pressed is adversely affected. In general, the residual stress is widely distributed inside the rolled material, and in the case of the rolled material, the gradient of the residual stress in the vicinity of the surface layer is often high.
Therefore, in the present invention, the absolute value of the residual stress at a depth of 1 μm from the surface is regulated to 50 MPa or less. The absolute value of the residual stress is preferably 30 MPa or less, more preferably 20 MPa or less. Therefore, the copper alloy according to the present invention has an absolute value of residual stress of, for example, 0 to 50, typically 5 to 50 MPa. The absolute value is used because there are two types of residual stress: tension and compression. The smaller the absolute value, the better the flatness.

In the present invention, the “absolute value of residual stress at a depth of 1 μm from the surface” means that measured by the following method. First, a test plate having a size of width 20 mm × length 200 mm is cut out from a copper alloy plate or strip. The rolling direction is the longitudinal direction. While gradually removing the surface layer on one side of the test piece using an etching solution, the curvatures φ _x and φ _y in the length direction (x) and the width direction (y) of the remaining test piece at each depth are measured. This is repeated until the plate thickness is halved. The curvature is obtained by measuring the warpage of the specimen. The curvature of the test piece is considered as a part of the circumference, and the reciprocal of the radius corresponding to this circle is the curvature. The curvature can be easily obtained mathematically by measuring the length and height of the strings. Thereafter, the relationship between the etching depth a and the curvature is plotted in the figure, and the absolute value σ _x (a) of the residual stress in the rolling direction (x) at the etching depth a = 1 μm from the surface is measured by the following formula. This method is a well-known method called the “Truting-Read method”, and is described in, for example, the following references.
References: Shigeru Yoneya, “Generation and Countermeasures for Residual Stress”, Yokendo Co., Ltd., p. 54-56, 1975

Strength reduction by heat treatment In the present invention, it is further specified that the tensile strength is reduced by 40 MPa or more by heat treatment heated at a temperature of 500 ° C. for 1 minute. “Heat treatment that is heated at a temperature of 500 ° C. for 1 minute” is a heat treatment condition that assumes strain relief annealing after press working. In the present invention, this heat treatment is performed by a method in which a copper alloy plate or strip to be tested is left in an argon atmosphere furnace heated to 500 ° C. for 1 minute, and then removed from the furnace and air-cooled. In the present invention, the tensile strength (TS) is a value obtained when a tensile test in the rolling parallel direction is performed according to JIS Z 2241.

  When the absolute value of the residual stress is reduced to 50 MPa or less, if it is a conventional copper alloy, most of the strength obtained by strain hardening is lost and softened, and further at a temperature of 500 ° C. for 1 minute. Even if heat treatment is performed, the strength does not decrease so much, and the rate at which the strength decreases (° C./s) is slow. On the other hand, if strength that is advantageous for press working is left, a conventional copper alloy will have a residual stress with a considerable magnitude, so that the desired flatness cannot be ensured.

  However, in the copper alloy according to the present invention, as will be described later, by devising the manufacturing conditions, heat treatment is further performed at a temperature of 500 ° C. for 1 minute while the absolute value of the residual stress is as small as 50 MPa or less. When it performs, it has the characteristic that intensity | strength falls 40 MPa or more. This means that the strength due to strain hardening remains even after the residual stress is removed, which improves the shearability during press working. The decrease in strength before and after the heat treatment heated at a temperature of 500 ° C. for 1 minute is preferably 50 MPa or more, more preferably 55 MPa or more, and even more preferably 60 MPa or more. However, if the difference in strength reduction is to be increased, the internal strain before the heat treatment must also be increased, and in this case, the residual stress also increases. Therefore, the decrease in strength is preferably 100 MPa or less, and more preferably 70 MPa or less.

A large decrease in strength in the strain relief annealing after press working, that is, a large degree of reduction in strain means that the lead frame after press working is easily flattened. In addition, in the copper alloy according to the present invention, it can be said that it is a surprising result that this is achieved in a short time despite the great decrease in strength in the strain relief annealing. Although it is not intended that the present invention be limited by theory, it is believed that this is due to the following reasons.
Residual stress is generated by pressing in the material after pressing. For this reason, unless the residual stress is removed by heat treatment, the material is warped. The residual stress is removed by heat treatment in a shorter time as the degree of strain before heat treatment is larger. This is because the movement, coalescence, and annihilation of dislocations due to heat treatment are considered to be performed more efficiently as the dislocation density is higher. Simply put, it is thought that the rate of encountering another dislocation is high when the dislocation moves. Therefore, in addition to the dislocations introduced into the press work, the presence of distortion (dislocations) before the press work effectively removes the residual stress by heat treatment. In the present invention, since the strength reduction is suppressed while removing the residual stress, the strain (dislocation) before the press working is larger than the conventional one, so that the strain removal by the heat treatment after the press working is extremely short. It is thought that it was made. By removing the strain, the internal stress is reduced and a flat material is obtained.

Second Phase Particles In one embodiment of the copper alloy plate or strip according to the present invention, the average particle size of the second phase particles having a particle size in the range of 10 to 1000 nm is 20 to 200 nm. By setting the average particle size of the second phase particles in such a range, the effect of improving the strength by precipitation hardening can be fully enjoyed. In addition, since the second phase particles having such a particle size range can suppress the movement of the transition, there is an effect of suppressing the strength reduction in the strain relief annealing performed at the final stage of manufacturing the copper alloy plate or strip. However, the average particle size of the second phase particles having a particle size in the range of 10 to 1000 nm is preferred because the effect of shortening the time in the strain relief annealing performed after the press working tends to be reduced when the precipitate having a small particle size is excessive. Is 100-200 nm.

  In the present invention, the second-phase particles mainly refer to intermetallic compound particles, but are not limited to this. Crystallized substances generated in the solidification process of melt casting, precipitates generated in the subsequent cooling process, hot It refers to precipitates generated during the cooling process after rolling, precipitates generated during the cooling process after solution treatment, and precipitates generated during the aging process. The reason why the range of the particle size of the second phase particles used for calculating the average particle size is limited to 10 to 1000 nm is that it is difficult to count particles less than 10 nm, and more than 1000 nm (1 μm). This is because the number of coarse crystallized substances and precipitates is small, the effect of improving the strength by precipitation is small, and even coarse foreign substances mixed by chance may be counted.

  The particle size and number of the second phase particles can be measured by SEM observation after etching a cross section parallel to the rolling direction of the material. In the present invention, the particle size of the second phase particles refers to the diameter of the smallest circle surrounding the particles when observed by SEM under such conditions.

Tensile strength (TS)
If the tensile strength (TS) is increased too much, it becomes difficult to suppress the residual stress to a desired level. In this case, the residual stress cannot be removed in the strain relief annealing performed at the final stage of the manufacturing process of the copper alloy sheet or strip, and it becomes difficult to obtain a flat material. On the other hand, if the tensile strength is too small, the residual stress is low, but the deformation due to punching is large, the dimensional accuracy is inferior, and the press workability is deteriorated. In one embodiment of the copper alloy plate or strip according to the present invention, the tensile strength (TS) is 400 to 650 MPa. If there is this level of tensile strength (TS), good punchability can be exhibited during press working.
Moreover, in one embodiment of the copper alloy plate or strip according to the present invention, the 0.2% proof stress is 350 to 600 MPa.

Manufacturing Method Next, a method for manufacturing a copper alloy plate or strip according to the present invention will be described.
The copper alloy sheet or strip according to the present invention can be manufactured by adopting a conventional manufacturing process of a general aging precipitation type copper alloy system, except that some processes are devised.

  The conventional manufacturing process of an aging precipitation type copper alloy sheet or strip will be outlined. First, using an atmospheric melting furnace, raw materials such as electrolytic copper, Cr, Fe, Ni, and P are melted to obtain a molten metal having a desired composition. Then, this molten metal is cast into an ingot. Thereafter, hot rolling is performed, and cold rolling and heat treatment are repeated to finish a strip or foil having a desired thickness and characteristics. Heat treatment includes solution treatment and aging treatment. In the solution treatment, an intermetallic compound corresponding to the alloy composition is dissolved in the Cu matrix, and at the same time, the Cu matrix is recrystallized. The solution treatment may be combined with hot rolling. In the aging treatment, the intermetallic compound dissolved in the solution treatment is precipitated as fine particles. This aging treatment increases strength and conductivity. Cold rolling is performed after aging, and then strain relief annealing is performed. Between the above steps, grinding, polishing, shot blast pickling and the like for removing oxide scale on the surface are appropriately performed.

  In producing a copper alloy sheet or strip according to the present invention, it is important to avoid operations that cause residual stress as much as possible while creating high strength in the pre-stage of strain relief annealing performed in the final stage. . By doing so, it is only necessary to remove a slight residual stress at the time of the strain relief annealing, so that a desired strength can be left even after the strain relief annealing. In order to suppress the occurrence of residual stress while ensuring a desired strength in the pre-stage of strain relief annealing, for example, in cold rolling before strain relief annealing, the rolling reduction per pass is preferably as small as possible. The rolling reduction per pass is preferably 30% or less, more preferably 25% or less. By reducing the rolling reduction, there is also an effect that the distribution of the generated residual stress becomes uniform. However, if the rolling reduction per pass is too small, the productivity will deteriorate, so it is preferable to adjust it appropriately in relation to the residual stress generated. Although the reduction ratio of the entire cold rolling before the stress relief annealing depends on the balance with the aging treatment conditions, it is preferably 25% or more, more preferably 30% or more in order to obtain sufficient strength. .

Further, in the strain relief annealing performed in the final stage, it is advantageous to slow the temperature increase rate and increase the cooling rate. Thereby, the residual stress on the surface is uniformly reduced, and uneven distribution of the residual stress is prevented. As a result, flatness is also improved. In addition, when the rate of temperature increase is too high, it is effective for reducing the residual stress, but dislocations in the material easily move and the strength decreases greatly. Even when the cooling rate is too low, the movement of dislocations during cooling cannot be suppressed, and the strength decreases.
Therefore, the average rate of temperature rise when the material temperature rises from 25 ° C. to 400 ° C. is preferably 80 to 200 ° C./second, and more preferably 80 to 100 ° C./second. Further, the average cooling rate when the material temperature is cooled from 500 ° C. to 200 ° C. is preferably 10 ° C./second or more, and more preferably 15 ° C./second.
Such a cooling rate can be achieved by air cooling if the plate thickness is about 0.3 mm or less, but water cooling is still better. However, even if the cooling rate is increased too much, the shape of the product is deteriorated, so that it is preferably 30 ° C./second or less, and more preferably 20 ° C./second or less. If the holding temperature of the strain relief annealing is too high, the surface of the material is oxidized, which adversely affects the etching characteristics and plating characteristics, whereas if it is too low, the residual stress cannot be removed. Therefore, the holding temperature is preferably 400 to 600 ° C, more preferably 450 to 550 ° C. The holding time at the holding temperature is preferably 5 to 30 seconds, more preferably 5 to 20 seconds because the residual stress cannot be removed if the holding time is too short, but the strength decreases greatly if it is too long.

  In the copper alloy plate or strip according to the present invention, the average particle size of the second phase particles is also defined, but various means known to those skilled in the art can be adopted as means for refining the second phase particles. Achievable. An exemplary control method is described below.

  In order to prevent the coarsening of the second phase particles, it is important to control the conditions of hot rolling and solution treatment. Coarse crystals are inevitably produced during the solidification process during casting, and coarse precipitates are inevitably produced during the cooling process. Therefore, in the subsequent process, it is necessary to dissolve these second phase particles in the matrix phase.

  Hot rolling is preferably performed after holding at 850 ° C. or higher for 1 hour or longer. When Cr that does not dissolve easily is added, a higher temperature may be set, but if it exceeds 1050 ° C., the material may be dissolved. The temperature at the end of hot rolling may end at a high temperature of 600 ° C. or higher. However, when it is difficult to form a solution in a later step, it is more effective to end at a lower temperature. In the cooling process after completion of hot rolling, it is preferable to suppress the precipitation of the second phase particles by increasing the cooling rate as much as possible. Water cooling is the most effective method for speeding up the cooling.

  Similarly, in the solution treatment, the second phase particles can be dissolved by setting the solution treatment temperature to 850 ° C. to 1050 ° C. Cooling after the solution treatment should be fast.

  The conditions for the aging treatment may be those conventionally used as useful for refining the precipitates, but note that the temperature and time are set so that the precipitates do not become coarse. If an example of the conditions of an aging treatment is given, it will be 0.5 to 50 hours in the temperature range of 375-625 degreeC, More preferably, it is 1 to 40 hours in the temperature range of 400-600 degreeC. The cooling rate after the aging treatment hardly affects the size of the precipitates.

  In addition to the lead frame, the copper alloy plate or strip according to the present invention requires connectors having high strength and high electrical conductivity (or thermal conductivity), pins, terminals, relays, switches, secondary It can be used for electronic equipment parts such as battery foil materials.

  Examples of the present invention will be described below together with comparative examples, but these examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the invention.

Example 1
Each copper alloy having the alloy composition shown in Table 1 was melted at 1300 ° C. in a high-frequency melting furnace, and cast into an ingot having a thickness of 30 mm. Next, the ingot was heated at 1000 ° C. for 1 hour, and then hot-rolled to a plate thickness of 10 mm (the material temperature at the end of hot rolling was 500 ° C.) and rapidly cooled in water. After surface chamfering to a thickness of 8 mm for removing scale on the surface, intermediate cold rolling was performed. Next, solution treatment was performed under conditions of 800 ° C. × 1 hour, and then cooled to room temperature in water. Next, an aging treatment was performed in an argon atmosphere under each condition shown in Table 2, and cold rolled to a thickness of 0.15 mm. At this time, in order to investigate the influence of the reduction ratio of one pass on the residual stress, the maximum reduction ratio for each pass was changed by the test plate, and the total reduction ratio was 30% or more (Table 2).
Finally, strain relief annealing was performed. It implemented using the convection type heat processing furnace in argon atmosphere. At this time, the average heating rate when the test plate temperature is raised from 25 ° C. to 400 ° C., the holding temperature, the holding time at the holding temperature, and the average cooling rate when the test plate temperature is lowered from 500 to 200 ° C. are tested. Varies with the plate (Table 2).

The characteristic evaluation was performed by the following method, and the results are shown in Table 3.
Regarding the strength, a tensile test in the rolling parallel direction was performed according to JIS Z 2241, and the tensile strength (TS) and 0.2% proof stress were measured.
The electrical conductivity (% IACS) was determined by volume resistivity measurement using a double bridge.
The average particle size of the second phase particles is a second phase in which the particle size is in the range of 10 to 1000 nm by observing 10 fields of view with a transmission electron microscope (HITACHI-H-9000) on a cross section parallel to the rolling direction. The number and particle size of the particles were calculated.
The residual stress was determined by the method described above.
The decrease in the tensile strength before and after the heat treatment heated at 500 ° C. for 1 minute was determined by the method described above.

Example 2 (comparison)
Each copper alloy having the alloy composition shown in Table 4 was melted at 1300 ° C. in a high-frequency melting furnace, and cast into an ingot having a thickness of 30 mm. Next, the ingot was heated at 1000 ° C. for 1 hour, and then hot-rolled to a plate thickness of 10 mm (the material temperature at the end of hot rolling was 500 ° C.) and rapidly cooled in water. After surface chamfering to a thickness of 8 mm for removing scale on the surface, intermediate cold rolling was performed. Next, solution treatment was performed under conditions of 800 ° C. × 1 hour, and then cooled to room temperature in water. Next, an aging treatment was performed in an argon atmosphere under each condition shown in Table 5, and cold-rolled to a thickness of 0.15 mm. At this time, in order to investigate the effect of the rolling reduction of one pass on the residual stress, the maximum rolling reduction for each pass was changed by the test plate, and the total rolling reduction was set to 30% or more (Table 5).
Finally, strain relief annealing was performed. It implemented using the convection type heat processing furnace in argon atmosphere. At this time, the average heating rate when the test plate temperature is raised from 25 ° C. to 400 ° C., the holding temperature, the holding time at the holding temperature, and the average cooling rate when the test plate temperature is lowered from 500 to 200 ° C. are tested. Varies with the plate (Table 5).

  The characteristic evaluation was performed in the same manner as in Example 1, and the results are shown in Table 6.

  No. The compositions of 19 to 36 are No. It is the same as the composition of 1-18.

Discussion No. In Nos. 1 to 18, since the conditions of cold rolling and stress relief annealing were both appropriate, the residual stress was 50 MPa or less, and the difference in tensile strength before and after heat treatment heated at a temperature of 500 ° C. for 1 minute was 40 MPa. That's it.
No. Nos. 19, 20, 29, and 30 had a high maximum rolling reduction for each pass of cold rolling, and the residual stress after strain relief annealing was high. No. In 19 and 29, the difference in strength in the heat treatment at 500 ° C. for 1 minute was also insufficient.
No. Nos. 21 and 31 were reduced in strength because the rate of temperature increase during strain relief annealing was too high. Therefore, the difference in strength in the heat treatment at 500 ° C. for 1 minute became insufficient.
No. Since 22 and 32 had the cooling rate too low, the intensity | strength fell, respectively. Therefore, the difference in strength in the heat treatment at 500 ° C. for 1 minute became insufficient.
No. Since the holding time at the time of strain relief annealing was too long, No. 23 and 33 each had reduced strength. Therefore, the difference in strength in the heat treatment at 500 ° C. for 1 minute became insufficient.
No. Since 24 and 34 had too short holding time, the residual stress after strain relief annealing became high.
No. 25, 28 and 35 were too high in retention time. Therefore, recovery was promoted while being held, and the strength was lowered, and the strength difference in the heat treatment at 500 ° C. × 1 minute became insufficient.
No. In Nos. 26, 27 and 36, since the holding temperature was too low, the residual stress after the strain relief annealing became high. Furthermore, no. No. 27 also increased the residual stress after strain relief annealing because the maximum rolling reduction for each pass of cold rolling was high.

Claims (7)

  Contains 0.02 to 3.0% by mass in total of one or more additive elements selected from the group consisting of Cr, Zn, Sn, Zr, Fe, P, Mg, Mn, Al and Co, and the balance A copper alloy plate or strip for electronic materials having a composition comprising Cu and inevitable impurities, the absolute value of residual stress at a depth of 1 μm from the surface being 50 MPa or less, and heating at a temperature of 500 ° C. for 1 minute A copper alloy sheet or strip whose tensile strength is reduced by 40 MPa or more by heat treatment. A copper alloy plate or strip for electronic materials having the composition shown in any one of 1) to 4) below, wherein the absolute value of residual stress at a depth of 1 μm from the surface is 50 MPa or less, and 500 ° C. A copper alloy plate or strip whose tensile strength is reduced by 40 MPa or more by heat treatment heated at a temperature of 1 min.
1) Cr: 0.1 to 0.5% by mass, balance Cu and unavoidable impurities 2) Cr: 0.1 to 0.5% by mass, Si, Zn, Sn And one or more selected from the group consisting of Zr up to a total of 1.0% by mass, a composition consisting of the balance Cu and inevitable impurities 3) Fe: 0.02-3.0% by mass, 4: Fe: 0.02-3.0 mass%, P: 0.02-0.15 mass% containing P: 0.02-0.15 mass% and consisting of remainder Cu and inevitable impurities A composition comprising one or more selected from the group consisting of Ni, Mg, Mn, Zn, and Sn up to 1.0% by mass in total, the balance being Cu and inevitable impurities.   The copper alloy sheet or strip according to claim 2, wherein the difference in tensile strength before and after the heat treatment heated at 500 ° C for 1 minute is 40 to 100 MPa.   The copper alloy plate or strip according to claim 2 or 3, wherein the second phase particles having a particle size in the range of 10 to 1000 nm have an average particle size of 20 to 200 nm.   The copper alloy sheet or strip according to any one of claims 2 to 4, wherein the tensile strength (TS) is 400 to 650 MPa.   The copper alloy sheet or strip according to any one of claims 2 to 5, having a 0.2% proof stress of 350 to 600 MPa.   The copper alloy plate or strip according to any one of claims 2 to 6, wherein the electronic material is a lead frame.