JP2011246740A - Cu-Co-Si BASED ALLOY SHEET OR STRIP FOR ELECTRONIC MATERIAL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper alloy sheet or strip which when a lead frame is formed from the copper alloy sheet or strip, hardly causes deformation of the lead in the lead frame and achieves shortening of annealing time required for stress relieving after the lead frame is press worked.SOLUTION: The copper alloy sheet or strip for an electronic material has a composition containing, by mass, 0.4 to 3.0% Co and 0.09 to 1.0% Si, and the balance Cu with inevitable impurities, wherein the absolute value of the residual stress in a depth of 1 μm from the surface is ≤50 MPa, and also tensile strength is reduced by ≥40 MPa by heat treatment of performing heating at 500°C for 1 min.

Description

  The present invention relates to a Cu—Co—Si alloy plate or strip for electronic materials, and more particularly to a Cu—Co—Si 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.

  Conventionally, copper alloy products for lead frames have been developed to improve such characteristics. Examples are given below.

Claim 1 of Japanese Patent Publication No. Sho 62-31059 (Patent Document 1) includes Ni: 1.0 to 3.5 wt%, Si: 0.2 to 0.9 wt%, and Mn: 0.02 to 1.0 wt. %, Zn: 0.1-5.0 wt%, Sn: 0.1-2.0 wt%, Mg: 0.001-0.01 wt%, and further selected from Cr, Ti, Zr There is disclosed a lead frame material for a semiconductor characterized by containing one or two or more of 0.001 to 0.01 wt% and the balance being substantially made of Cu.
According to claim 2 of this document, as a method for producing the lead frame material, a copper alloy ingot having the above composition is hot-rolled and then cooled from a temperature of 600 ° C. or more to a rate of 5 ° C./second or more. After the cold working, annealing is performed at a temperature of 400 to 600 ° C. for 5 minutes to 4 hours, and then temper finish rolling is performed, and then annealing at a temperature of 400 to 600 ° C. for 5 to 60 seconds is performed. A method of performing is disclosed. The short-time annealing at a temperature of 400 to 600 ° C. for 5 to 60 seconds in the final step is considered to recover the elongation lowered by rolling, reduce the residual stress, and make it uniform.
According to this document, the above lead frame material has high strength and high stiffness strength, and further has excellent heat-resistant peelability of solder, and is also excellent in hot workability. .

In JP-A-7-258805 (Patent Document 2), 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 3) 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). ).

Japanese Patent Publication No.62-31059 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.

  The present invention completed on the basis of the above knowledge includes, in one aspect, Co: 0.4 to 3.0% by mass, Si: 0.09 to 1.0% by mass, the balance being Cu and inevitable impurities. A copper alloy plate or strip for electronic materials, the absolute value of the residual stress at a depth of 1 μm from the surface is 50 MPa or less, and the tensile strength is 40 MPa or more by heat treatment heated at a temperature of 500 ° C. for 1 minute. It is a copper alloy plate or strip that decreases.

  In one embodiment of the copper alloy sheet or strip according to the present invention, the absolute value of the residual stress is 0 to 50 MPa.

  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 another embodiment of the copper alloy sheet 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 another embodiment of the copper alloy plate or strip according to the present invention, the tensile strength (TS) is 500 to 700 MPa.

  In still another embodiment of the copper alloy plate or strip according to the present invention, one or more selected from Cr, Ni, Mg, Mn, Fe, Sn, Zn, Al, and P are further added. Up to 1.0% by mass.

  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.

  The Cu—Co—Si alloy according to the present invention belongs to an alloy system generally called a Corson alloy. Cu-Co-Si based alloy is a kind of precipitation hardening type copper alloy. By aging treatment of solution-treated supersaturated solid solution, fine Co-Si based intermetallic compound particles are uniformly dispersed, At the same time as the strength increases, the amount of solid solution elements in the copper decreases, 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.

Co and Si addition amounts Co and Si form Co—Si compound particles (such as Co ₂ Si) as an intermetallic compound by performing an appropriate heat treatment, and can increase the strength without deteriorating conductivity.
If the addition amount of Si or Co is too small, the desired strength cannot be obtained, and if it is too large, the strength can be increased, but the electrical conductivity is remarkably lowered and the hot workability is lowered. Since Si reacts with C and reacts with O, if the addition amount is large, a very large amount of inclusions are formed, which causes breakage during bending.

  Therefore, a suitable Si addition amount is 0.09 to 1.0% by mass, preferably 0.09 to 0.8%. A suitable Co addition amount is 0.4 to 3.0% by mass, preferably 0.4 to 2.5% by mass.

The precipitate of Co—Si compound particles is generally composed of a stoichiometric composition, and the mass ratio of Co and Si is the mass composition ratio of Co ₂ Si, which is an intermetallic compound (atomic weight of Co × 2: atomic weight of Si × By bringing the ratio close to 1), that is, by setting the mass ratio of Co and Si to Co / Si = 3 to 7, preferably 3.5 to 5, good electrical conductivity can be obtained. If the Co ratio is higher than the above mass composition ratio, the electrical conductivity tends to decrease, and if the Si ratio is higher than the above mass composition ratio, the hot workability tends to deteriorate due to coarse Co-Si crystallized products.

Addition amount of other elements The copper alloy sheet or strip according to the present invention is one or two selected from Cr, Ni, Mg, Mn, Fe, Sn, Zn, Al and P in addition to Co and Si. The above can be contained up to 1.0% by mass in total. Hereinafter, the action of each element and the preferred content will be described.

(1) Cr, Ni
Cr and Ni are dissolved in Cu and suppress the coarsening of crystal grains during the solution treatment. Also, the alloy strength is raised. During the aging treatment, silicide is formed and deposited, which can contribute to improvement in strength and conductivity. These additive elements may be positively added because they do not substantially lower the electrical conductivity. However, if the added amount is large, the characteristics may be adversely affected. Therefore, it is preferable to add one or both of Cr and Ni to a total of 1.0% by mass, and preferably 0.005 to 1.0% by mass.
(2) Mg, Mn
Since Mg and Mn react with O, the deoxidation effect of the molten metal can be 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 0.5% by mass in total, and it is preferable to add 0.005 to 0.4% by mass.
(3) Sn
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, and preferably 0.1 to 0.4% by mass. However, when adding both Mg and Sn, in order to suppress the adverse effect on the electrical conductivity, the total concentration of both is up to 1.0 mass%, preferably up to 0.8 mass%.
(4) Zn
Zn has an effect of suppressing solder embrittlement. However, if the amount added is large, the electrical conductivity decreases, so it is preferable to add up to 0.5% by mass, and preferably 0.1 to 0.4% by mass.
(5) Fe, Al, P
These elements are also elements that can improve the alloy strength. What is necessary is just to add as needed. However, if the addition amount is large, the characteristics deteriorate depending on the added element. Therefore, it is preferable to add up to 0.5% by mass, and it is preferable to add 0.005 to 0.4% by mass.

  Since the above Cr, Ni, Mg, Mn, Sn, Zn, Fe, Al, and P tend to impair manufacturability when the total exceeds 1.0% by mass, the total is preferably 1.0% by mass or less. More preferably, the content is 0.5% by mass or less.

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 strip or plate. 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 heated at a temperature of 500 ° C. for 1 minute” is a heat treatment condition assuming a strain relief annealing after pressing. 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 particle mainly refers to silicide, but is not limited to this. Crystallized substances generated in the solidification process of melt casting and precipitates generated in the subsequent cooling process, after hot rolling It refers to precipitates generated in the cooling process, precipitates generated in the cooling process after solution treatment, and precipitates generated in 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 500 to 700 MPa, typically 550 to 650 MPa. If there is this level of tensile strength (TS), good punchability can be exhibited during press working.

Manufacturing Method Next, a method for manufacturing a copper alloy plate or strip according to the present invention will be described.
The copper alloy plate or strip according to the present invention can be manufactured by adopting a conventional manufacturing process for a Corson alloy plate or strip, except that some steps are devised.

  An outline of a conventional manufacturing process of a Corson-based copper alloy sheet or strip will be outlined. First, using an atmospheric melting furnace, raw materials such as electrolytic copper, Co, and Si 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 plate having a desired thickness and characteristics. Heat treatment includes solution treatment and aging treatment. In the solution treatment, silicide (eg, a Co—Si compound) is solid-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, silicide (eg, Co—Si 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, and 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 for strain relief annealing is too high, the surface of the material is oxidized, which adversely affects etching characteristics and plating characteristics. In addition, a precipitate of a compound composed of Co and Si is likely to be coarsened in a high temperature region. On the other hand, if the holding temperature 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. 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 950 ° 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 1070 ° 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.

  In the present invention, it is preferable to carry out the solution treatment at a high temperature because Co, which is difficult to dissolve, is added. However, if it is too high, the recrystallized grains become coarse, and therefore, for example, 800 ° C. to 1070 ° C. Preferably, the temperature is 950 ° C to 1050 ° C. The solution treatment time may be determined in consideration of the solid solution state and the size of the recrystallized grains, but is typically controlled to 480 seconds or less, preferably 240 seconds or less, more preferably 120 seconds or less. To do. However, since the number of coarse second phase particles may not be reduced if the time during which the material temperature is maintained at the maximum temperature is too short, it is preferably 10 seconds or more, and 20 seconds or more. More preferably.

  From the viewpoint of preventing the precipitation of the second phase particles and the coarsening of the recrystallized grains, the cooling rate after the solution treatment is preferably as high as possible. Specifically, the average cooling rate when the material temperature decreases from the solution treatment temperature to 400 ° C. is preferably 15 ° C./s or more, and more preferably 50 ° C./s or more.

  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
A copper alloy containing Co: 1.5% by mass, Si: 0.35% by mass and composed of the balance Cu and inevitable impurities is melted at 1300 ° C. in a high-frequency melting furnace to form an ingot having a thickness of 30 mm. Casted. 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, the solution treatment was performed under the condition of 950 ° C. × 120 seconds, and then cooled in water to room temperature. Under the present circumstances, the average cooling rate when cooling from 950 degreeC which is solution treatment temperature to 400 degreeC was 35 degreeC / s.
Next, an aging treatment was performed in an argon atmosphere under each condition shown in Table 1, 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 1).
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 1).

The characteristic evaluation was performed by the following method.
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.

No. For 1, 2, 3, 7 and 8, the conditions for cold rolling and strain relief annealing were both appropriate, so that the residual stress was 50 MPa or less and the tensile strength before and after heat treatment was heated at 500 ° C. for 1 minute. The difference in strength was 40 MPa or more.
No. In No. 4, strain relief annealing was performed excessively, and the strength was lowered to an unfavorable level. Therefore, the difference in strength in the heat treatment at 500 ° C. for 1 minute became insufficient.
No. In No. 5, the residual stress was not sufficiently controlled before the strain relief annealing. When the residual stress was reduced to a usable level by strain relief annealing, the strength decreased to an undesirable level. Therefore, the difference in strength in the heat treatment at 500 ° C. for 1 minute became insufficient.
No. 6 is No.6. Similar to 5, residual stress was not sufficiently controlled before strain relief annealing. As a result of strain relief annealing under conditions where desirable strength remains, the residual stress was not sufficiently reduced.
No. No. 9 had a temperature increase rate during strain relief annealing that was too high. No. 10 had a cooling rate during annealing that was too low. Since No. 11 was too long for the strain relief annealing, the strength was lowered to an unfavorable level. Therefore, the difference in strength in the heat treatment at 500 ° C. for 1 minute became insufficient.
No. Since the holding time of No. 12 was too short, the residual stress after stress relief annealing became high.
No. Since the holding temperature of No. 13 was too high, the strength decreased to an unfavorable level. Therefore, the difference in strength in the heat treatment at 500 ° C. for 1 minute became insufficient.
No. Since the holding temperature of No. 14 was too low, the residual stress after strain relief annealing became high.

Example 2
Except for changing the alloy composition as shown in Table 3, no. Each test plate was manufactured under the same manufacturing conditions as in No. 1, and the characteristics were examined in the same manner. The results are shown in Table 4. It can be seen that the effects of the present invention can be obtained even when various additive elements are added.

Claims (7)

  Co: 0.4 to 3.0% by mass, Si: 0.09 to 1.0% by mass, a copper alloy plate or strip for electronic materials composed of the balance Cu and inevitable impurities, To 1 μm depth of the residual stress is 50 MPa or less, and a copper alloy plate or strip whose tensile strength is reduced by 40 MPa or more by heat treatment at a temperature of 500 ° C. for 1 minute.   The copper alloy sheet or strip according to claim 1, wherein the absolute value of the residual stress is 0 to 50 MPa.   The copper alloy sheet or strip according to claim 1 or 2, wherein the difference in tensile strength between 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 any one of claims 1 to 3, wherein 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.   The copper alloy sheet or strip according to any one of claims 1 to 4, wherein the tensile strength (TS) is 500 to 700 MPa.   Furthermore, 1 type or 2 types or more selected from Cr, Ni, Mg, Mn, Fe, Sn, Zn, Al, and P are contained to 1.0 mass% in total, The any one of Claims 1-5 description Copper alloy plate or strip.   The copper alloy plate or strip according to any one of claims 1 to 6, wherein the electronic material is a lead frame.