JP2002285261A - Copper alloy having excellent strength stability and heat resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper alloy which can secure stable strength, and can exhibit excellent heat resistance hardly lowering hardness even when being subjected to heat treatment such as stress relieving annealing. SOLUTION: The copper alloy contains, as a chemical component, by mass, 1.0 to 3.0% Fe, and in which the volume fraction of crystallized and precipitated products having the average grain size of 0.05 to 10 μm is controlled to 0.5 to 10%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a case where the dispersion of characteristics such as mechanical strength, which is widely used in the industrial fields such as electric / electronic and mechanical fields, is small, and heat treatment such as strain relief annealing is performed. In particular, the present invention relates to a copper alloy excellent in heat resistance with almost no decrease in strength. still,
The copper alloy of the present invention is used in various fields as described above. Hereinafter, as a typical application example, description will be made focusing on a case where the copper alloy is used for a lead frame which is a semiconductor component.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become lighter, thinner and smaller, the size and weight of copper alloy parts used for lead frames, terminals, connectors, and the like constituting the electronic devices have been advanced.

[0003] Copper alloys for semiconductor lead frames include:
Conventionally, a copper alloy containing Fe has been generally used, in particular, Fe: 2.1 to 2.6%, P: 0.015 to
A copper alloy (CDA194 alloy) containing 0.15% and Zn: 0.05 to 0.20% has strength,
Due to its excellent electrical and thermal conductivity, it is widely used as an international standard alloy.

[0004] In processing a lead frame, it is common to stamp a copper alloy plate having the above-mentioned chemical composition into a multi-pin shape. In order to cope with the reduction in size and weight, the copper alloy plate as a raw material has been reduced in thickness and the number of pins has been increased, and the pins after the stamping tend to have irregular stress due to residual stress. Therefore, usually, a multi-pin shaped copper alloy sheet obtained by stamping is subjected to heat treatment (strain relief annealing) to remove the distortion. However, when such a heat treatment is performed, the material is easily softened, and it is difficult to maintain the mechanical strength before the heat treatment. In the manufacturing process, from the viewpoint of improving productivity, it is required to perform the heat treatment at a higher temperature and for a shorter time. Therefore, there is a strong demand for ensuring excellent heat resistance that can withstand heat treatment at high temperatures and maintain strength.

To solve such a problem, Fe,
The main components such as P and Zn are specified, and other Sn, M
Techniques for controlling trace added elements such as g and Ca have been proposed. However, since such component control alone cannot sufficiently cope with the above-mentioned copper alloy parts, such as miniaturization, weight reduction, and securing properties such as strength, in recent years, the internal structure of copper alloys and the precipitation state of precipitates have been developed. Is being proposed.

For example, Japanese Patent Application Laid-Open No. 10-324935 discloses that
Japanese Patent Application Laid-Open No. H11-80862 discloses a technique in which the ratio between the number of particles having a particle diameter of 100 ° or more and the number of particles having a particle diameter of less than 100 ° is defined to improve the strength and conductivity. Discloses a technique for improving the heat resistance by specifying the volume fraction of fine Fe particles having a diameter of 40 nm or less.

The above technique controls the particle size of fine precipitates, but the particle size of such fine precipitates changes sensitively because the heat treatment may cause the precipitates to form a solid solution. Since it is easy to control the dislocation, the dislocation moves and disappears, and the pinning effect varies. Therefore, there is a problem that the characteristics of the obtained copper alloy are also likely to vary.

Japanese Unexamined Patent Publication (Kokai) No. 4-272161 discloses a method for producing a copper alloy material in which a variation in characteristics such as mechanical strength is stabilized.
A step of heating to 100 to 930 ° C. or higher or removing an oxide film is required, and further study is required from the viewpoint of cost and productivity.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is an object of the present invention to secure a stable strength and perform a heat treatment such as a strain relief annealing. Even in such a case, an object of the present invention is to provide a copper alloy exhibiting excellent heat resistance such that the strength hardly decreases.

[0010]

The copper alloy according to the present invention, which has excellent strength stability and heat resistance, has an Fe content of 1.0 to 3.0.
% (In the case of a chemical component, it means mass%) and a crystal having an average particle size of 0.05 μm or more and 10 μm or less.
The precipitate is intended to have a volume fraction of 0.5% or more and 10% or less, and further, the number of crystals / precipitates having an average particle diameter of 0.05 μm or more and 10 μm or less. Is preferably 1000 / mm ² or more.

In order to further improve the properties such as strength stability and heat resistance, P: 0.01 to 0.1% and Zn: 0.01
~ 1.0%, Sn, Al, C
It is effective to contain at least one element selected from the group consisting of r, Ti, Mg, Mn and Ca in a range of 0.01% or more and 0.5% or less.

The term "crystal / precipitate" refers to a crystallized or precipitated substance or a mixture thereof which crystallizes or precipitates in a copper alloy, and its chemical component composition is limited. Instead, it refers to crystals / precipitates of various chemical components such as Fe-Ti, Mn-P, Cr-P, etc., in addition to those of Fe alone and Fe-P. The “average particle size” refers to the average value of the diameters of the centers of gravity of the respective crystals and precipitates.

In controlling the morphology of crystals and precipitates in the copper alloy so as to satisfy the above requirements, the temperature at the inlet side in the hot rolling step is set to 900 to 1000 ° C., and the temperature at the final pass outlet side is set to 600 to 850 ° C. It is very effective to set the average cooling rate from the entrance side to the exit side of the final pass at 0.1 to 5 ° C./sec.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have realized a copper alloy which is excellent in strength stability and hardly causes a decrease in strength even when heat treatment such as strain relief annealing is performed under the above-described circumstances. Aiming at, we examined from various angles. as a result,
The present inventors have found that the above object can be achieved satisfactorily by regulating the Fe content in the copper alloy and appropriately controlling the density of crystals and precipitates of a specific size, and have reached the present invention.

First, the reason why the size and density are specified in controlling the crystals and precipitates in the copper alloy in the present invention will be described in detail.

In the present invention, crystals / precipitates having an average particle size of 0.05 μm or more and 10 μm or less are targeted, but those having such a particle size are too small in the average particle size. This is because crystals and precipitates may re-dissolve during heat treatment such as strain relief annealing, which is difficult to control, and is not effective for stabilizing properties such as strength. Further, the control of the crystals / precipitates of 10 μm or less is that the crystals / precipitates of this size are
This is because, during heat treatment such as strain relief annealing, the recovery and recrystallization of crystals are suppressed, which effectively reduces the hardness, that is, ensures heat resistance, and is also effective in ensuring workability and wire bonding properties.

When the average particle size is 0.05 μm or more,
If the proportion of crystals and precipitates of 0 μm or less in the copper alloy is small, the dislocation movement / disappearance and the pinning effect are not sufficiently exhibited, so that nucleation and grain growth of recrystallization progress and the strength decreases. Tends to deteriorate over time. In addition, the recovery and recrystallization of crystals generated during heat treatment such as strain relief annealing cannot be effectively suppressed, so that it is difficult to ensure heat resistance. Therefore, in the present invention, the average particle size is 0.1.
Crystals and precipitates of not less than 05 μm and not more than 10 μm are present in a volume fraction of 0.5% or more, preferably 0.6% or more.

However, even if the proportion of the crystals and precipitates having an average particle size of 0.05 μm or more and 10 μm or less in the copper alloy is too large, it becomes a nucleus of recrystallization during heat treatment such as strain relief annealing. Since there are many starting points, recrystallization is promoted, and on the contrary, the hardness after the heat treatment is reduced. Therefore, when the average particle size is 0.05 μm or more, 10 μm
Crystals and precipitates of m or less should be suppressed to 10% or less, preferably 9% or less in volume fraction.

In order to more reliably exhibit the strength stability and heat resistance of the copper alloy, the crystal and precipitate having an average particle diameter of 0.05 μm or more and 10 μm or less have a particle density of 1000 μm or less.
It is preferable to control the number of pieces / mm ² or more.

When the average particle size is 0.05 μm or more and 10 μm
Crystals and precipitates of m or less are preferably in a state of being uniformly dispersed in the compound, but even in a state of being uniformly dispersed, the higher the density of the size particles is, the more the dislocation is. The movement and extinction and the pinning effect are sufficiently exhibited to suppress the growth of recrystallized grains, and also to sufficiently suppress the recovery and recrystallization even when heat treatment such as strain relief annealing is performed. You can do it. Therefore, in the present invention,
It is preferable to control the particle density of crystals / precipitates having an average particle diameter of 0.05 μm or more and 10 μm or less to be 1000 particles / mm ² or more, and more preferably 1100 particles / m 2.
m ² or more.

The crystallization / precipitation state of the crystals / precipitates is determined by FE
-Observed by SEM at a magnification of 1000 to 10000 times,
The obtained image was examined by image analysis. The average particle size of the crystals / precipitates is obtained by calculating the average value of the diameters of the centers of gravity of the crystals / precipitates.
m, the volume fraction of crystals and precipitates is 100 μm × 100
μm, and the average particle size is 0.05μ.
The number of crystals / precipitates having a size of m or more and 10 μm or less occupying 1 mm ² is obtained by observing 10 visual fields with 100 μm × 100 μm as one visual field and multiplying the number obtained therefrom by 10 times.

Next, the reason for defining the chemical components in the copper alloy in the present invention will be described in detail.

Fe is an element necessary for precipitating in a copper alloy to improve the strength, and in order to effectively exhibit such an effect, 1.0% or more, preferably 1.2% or more. Need to be added. However, if it is contained excessively, a large amount of coarse crystals and precipitates are generated during the production of the ingot, thereby deteriorating the ductility of the copper alloy and lowering the conductivity. In addition, in heating or intermediate annealing performed during hot rolling from an ingot to a thin plate, giant precipitates of Fe are generated and hot rolling workability is deteriorated, or giant crystals and precipitates of Fe are produced in the final product. , Causing a decrease in strength after strain relief annealing, that is, a deterioration in heat resistance. Therefore, F
The amount of e needs to be suppressed to 3.0% or less, preferably 2.8% or less.

In the present invention, by defining the contents of P and Zn, it is possible to further increase the strength stability and heat resistance of the copper alloy and to secure characteristics such as solder adhesion.

That is, P is an element which has a deoxidizing effect and is also effective for forming crystals and precipitates with Fe and strengthening the precipitation of the copper alloy. To effectively exert such an effect, In the presence of an appropriate amount of Fe as described above,
The content should be 1% or more, preferably 0.02% or more. However, even if the P content is too large, the solid solubility limit of Fe is reduced, and a large amount of coarse crystals and precipitates are produced during ingot production, and a large number of crystal recovery nuclei during annealing are present to promote the recovery. As a result, the strength after annealing decreases. It also causes a decrease in conductivity. Therefore, the P content is preferably suppressed to 0.1% or less, more preferably 0.09% or less.

Zn is an effective element for suppressing the peeling of tin and solder used for joining electronic components, and it is preferable to add 0.01% or more to effectively exhibit such an effect. It is more preferably at least 0.1%.
However, even if it is added excessively, the effect is saturated and the molten tin and the spreadability of the solder are rather deteriorated.
It is preferably controlled to 0% or less, more preferably 0.1%.
9% or less.

In addition, Sn, Al, Cr, Ti, Mg, Mn
It is also effective to obtain the following improvement effect by adding at least one kind selected from the group consisting of Ca and Ca.

That is, the above Sn, Al, Cr, Ti, M
g, Mn, and Ca are elements that contribute to heat resistance by forming a solid solution in the copper alloy, and have an effect of minimizing a decrease in strength even when heat treatment such as annealing is performed. However, if it is added excessively, macrosegregation occurs during casting, so that coarse crystals and precipitates are easily generated, and a decrease in conductivity is also easily caused. Therefore, Sn, Al, Cr, Ti,
Each of at least one element selected from the group consisting of Mg, Mn, and Ca is 0.01% or more, and each of the elements is 0.1% or more.
It is preferable to add within the range of 5% or less, and more preferably, the lower limit is 0.05% and the upper limit is 0.45%.

In addition, a small amount of P contained in the copper alloy
b, Ni, Si, Be, Zr and In in total of 0.1
%, The effect of the present invention obtained by defining the chemical components as described above can be more effectively exerted.

The elements contained in the steel of the present invention, in addition to those described above, have unavoidable impurities introduced depending on the conditions of raw materials, materials, production facilities and the like, and further adversely affect the achievement of the object of the present invention. The case where an allowable element such as no S is included is also included in the technical scope of the present invention.

In the present invention, in order to control the crystals / precipitates to have the above-mentioned crystallization / precipitation form, it is effective to perform hot rolling under the following conditions in the production.

That is, the entry temperature in hot rolling is set to 90
By setting the temperature to 0 ° C. or higher, preferably 910 ° C. or higher, the re-solid solution of the crystals / precipitates by soaking before hot rolling is promoted, and the influence of segregation appearing in the ingot is eliminated to remove the crystals / precipitates. Can be satisfactorily dispersed. However, even if the entry-side temperature is too high, a large amount of coarse Fe-P-based precipitates are generated during soaking before hot rolling, which causes deterioration of properties such as strength. Entry temperature at 10
The temperature is set to 00 ° C or lower, preferably 990 ° C or lower.

By setting the final pass exit side temperature in hot rolling to 600 ° C. or higher, not only can precipitates formed by hot rolling be prevented from growing and becoming coarse, but also precipitates formed during the annealing step. The strength and heat resistance can be secured by maintaining the amount of fine Fe-based precipitates, and it is preferably 610 ° C. or higher. However, even if the final pass exit side temperature is too high, the formation of crystals and precipitates of the size specified in the present invention becomes insufficient, and properties such as strength cannot be sufficiently stabilized. Pass outlet temperature is 850
° C or lower, preferably 840 ° C or lower.

Further, by controlling the average cooling rate from the entrance side to the exit side of the final pass to 0.1 to 5 ° C./s,
The amount of crystals and precipitates having an average particle size of 0.05 μm or more and 10 μm or less can be appropriately controlled.

If the average cooling rate is too slow, crystals and precipitates grow to a coarse size and the degree of dispersion is not uniform, which is not preferable. Therefore, the average temperature decreasing rate from the entrance side to the exit side of the final pass is set to 0.1 ° C./s or more, preferably 0.2 ° C./s or more. On the other hand, if the average cooling rate is too high, the hot rolling time will be short, and the generation of crystals and precipitates of the size specified in the present invention will be insufficient. As a result, the characteristics such as strength become unstable, so that the average cooling rate from the entrance side to the exit side of the final pass is 5 ° C./s.
Or less, preferably 4 ° C./s or less.

[0036]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. Modifications can be made, and all of them are included in the technical scope of the present invention.

After the copper alloys having the chemical components shown in Table 1 were melted in a coreless furnace, they were ingot by semi-continuous casting to obtain an ingot having a thickness of 50 mm × width 200 mm × length 500 mm. After heating each ingot, the conditions shown in Table 2 (entrance temperature, exit temperature, average cooling rate from entrance to exit of last pass)
Then, hot rolling was performed to obtain a thickness of 16 mm, and after facing, cold rolling and intermediate annealing were repeated to obtain a copper alloy sheet having a thickness of about 0.15 mm.

The average cooling rate from the entry side to the exit side of the final pass in Table 2 is appropriately adjusted by controlling the amount of cooling water / injection speed, controlling the roll speed, and changing the plate thickness during the pass. is there.

[0039]

[Table 1]

[0040]

[Table 2]

A test piece was arbitrarily taken out of the copper alloy plate obtained as described above, and the conductivity was measured. The conductivity is
A strip-shaped test piece was processed by milling and measured by a double-bridge resistance measuring device.

From each copper alloy plate, four 50 mm square plates were arbitrarily sampled for each sample, and the hardness, hardness variation, hardness after annealing, and decrease in hardness after annealing were determined. .

The hardness was measured by applying a load of 0.5 kg to each of the four 50 mm square plates using a micro-Vickers hardness tester. The difference between the highest and lowest values was taken.
After heating the four 50 mm square plates at 450 ° C. for 3 minutes, the micro Vickers hardness was measured again with a load of 0.5 kg, and the hardness reduction was determined from the difference from the hardness before heating. .

The morphology of crystals / precipitates having an average particle size of 0.05 μm or more and 10 μm or less was evaluated by image analysis using an image observed with a scanning electron microscope. In detail, Hitachi S4500 type FE-
SEM (Field Emission Scanning Electron Microscope)
canning Electron Microscopy) at a magnification of 1000
The observation was performed by observing a visual field of 100 μm × 100 μm at a magnification of ２０20,000.

In the above field emission scanning electron microscope,
Observation with backscattered electrons is the object of the present invention.
It is preferable because the existence state of crystals and precipitates at the level of 05 μm can be clearly grasped. Also, if the observation magnification is too high, fine crystals and precipitates can be observed well,
For samples where the distribution of crystals / precipitates in the copper alloy is sparse, the crystallization / precipitation morphology cannot be fully understood,
If the observation magnification is too low, a submicron-level fine compound cannot be detected. Therefore, the volume fraction of crystals / precipitates of several μm level is obtained at a magnification of about 1000 times, and the volume fraction of fine crystals / precipitates of a submicron level is obtained at a magnification of about 10,000 times. It is desirable to use the observation in combination.

The crystals and precipitates present in the copper alloy of the present invention have various chemical composition compositions as described above, and their sizes vary from a few nm level to a few μm level. Image analysis was performed on crystals / precipitates having an average particle size of 0.05 μm or more and 10 μm or less effective for achieving the target.

Image analysis of the image observed by the above method was performed, and the crystal having an average particle size of 0.05 μm or more and 10 μm or less was analyzed.
The size, volume fraction and particle density of the precipitate were determined. Media analysis software includes MEDIA CYBERN
Image-Pro Plus manufactured by ETICS was used.

The size (average particle size) of each crystal / precipitate is obtained by calculating the average value of the diameter of the center of gravity of the crystal / precipitate. Further, a crystal having an average particle diameter of 0.05 μm or more and 10 μm or less.
The volume fraction of the precipitate is as follows: the crystal of the above-mentioned size occupying one visual field (100 μm × 100 μm) in each 50 mm square plate material.
The area ratio of the precipitate was determined, and the average value over five visual fields was determined. The average particle diameter is 0.05 μm or more and 10 μm or less. The number of crystals / precipitates of the above size is determined in a total of 10 visual fields when 100 μm × 100 μm is defined as 1 visual field, and the obtained value is multiplied by 10 times. And the number of crystals / precipitates of the above size existing in 1 mm ² was determined. Tables 3 to 5 show these measurement results.

[0049]

[Table 3]

[0050]

[Table 4]

[0051]

[Table 5]

From Tables 3, 4 and 5, it is found that No. 3 satisfying the requirements of the present invention. In Nos. 1 to 15, variations in hardness are small and stable strength can be secured. Further, even when heat treatment such as strain relief annealing is applied, the amount of decrease in hardness is small, the heat resistance is excellent, and the conductivity can be ensured.

On the other hand, no. In Nos. 16 to 34, any of the requirements specified in the present invention are not satisfied, so that the obtained strength varies, the strength is significantly reduced after the heat treatment, or the conductivity is unfavorable.

That is, No. In Nos. 16 to 21, the production conditions did not satisfy the requirements specified in the present invention, and the obtained copper alloy had a large variation in hardness, and resulted in a decrease in hardness after annealing. The reason for such a result is that In the case of No. 16, the inlet temperature is too low and excessive crystals
The formation of a precipitate, In No. 17, since the entrance temperature was too high, the particle density of the generated crystals / precipitates was below the range of the present invention. In No. 18, since the final pass exit side temperature was too low, the crystal / precipitate grew to a coarse size, and the number of crystals / precipitate of the size specified in the present invention could not be secured. . In No. 19, the exit temperature on the final pass side was too high, and the number of crystals and precipitates specified in the present invention could not be secured sufficiently. In addition, No. In No. 20, the number of crystals / precipitates of the size specified in the present invention could not be sufficiently secured because the average cooling rate from the entry side to the exit side of hot rolling was too high. In the case of No. 21, it can be mentioned that, because the average cooling rate was too slow, the crystals / precipitates grew to a coarse size and the volume fraction exceeded the specified range.

No. In No. 22, since the Fe amount was below the specified range, sufficient crystals and precipitates could not be generated, and the desired strength could not be stably obtained.
No. In No. 23, since the amount of Fe was too large, excessive crystals / precipitates were generated, resulting in poor heat resistance and conductivity.

No. In No. 24, since the amount of P was too small, a sufficient amount of crystals and precipitates were not generated, and the desired strength could not be stably obtained. No. No. 25 resulted in inferior heat resistance and conductivity due to too much P content. In addition, No. In No. 26, since the Zn content was too small, peeling occurred when soldering was performed. Also, N
o. In the case of No. 27, since the Zn content was too large, the result was rather indicative of a poor soldering.

No. In 28-34, Sn, Al, C
Since the added amount of r, Ti, Mg, Mn or Ca was too large, the conductivity was deteriorated.

It should be noted that the variation in the hardness after the strain relief annealing is small if the variation in the hardness before the annealing is small.

[0059]

The present invention is configured as described above,
By controlling the size and density of the crystals and precipitates to be crystallized and precipitated in the copper alloy as in the present invention, stable strength can be ensured, and even when heat treatment such as strain relief annealing is performed. Thus, it was possible to obtain a copper alloy exhibiting excellent heat resistance that hardly causes a decrease in hardness. With the realization of such a copper alloy, it has become possible to supply electronic components such as lead frames and the like which are lighter and have higher quality.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22F 1/00 661 C22F 1/00 661A 683 683 691 691B 692 692A (72) Inventor Yasuaki Sugizaki Takatsuka, Nishi-ku, Kobe-shi Kobe Steel Research Institute Kobe Research Institute, Kobe Steel, Ltd. Kobe Research Institute, Ltd. (72) Inventor Yoshio Hemi 1-5-5, Takatsukadai, Nishi-ku, Kobe, Japan Inventor Junichi Osako 14-1, Nagafuminatocho, Shimonoseki City, Yamaguchi Prefecture Kobe Steel, Ltd.

Claims (5)

[Claims] 1. A crystal / precipitate satisfying Fe: 1.0 to 3.0% (mean% by mass in the case of a chemical component; the same applies hereinafter) and having an average particle size of 0.05 μm or more and 10 μm or less A copper alloy excellent in strength stability and heat resistance, characterized by having a volume fraction of 0.5% or more and 10% or less. 2. The method according to claim 1, wherein said average particle size is not less than 0.05 μm.
^2. The copper alloy according to claim 1, wherein the number of crystals / precipitates having a size of not more than μm is not less than 1000 / mm ² . 3. P: 0.01 to 0.1%, Zn:
The copper alloy according to claim 1 or 2, which satisfies 0.01 to 1.0%. 4. Further, Sn, Al, Cr, Ti, Mg, M
The copper alloy according to any one of claims 1 to 3, wherein the copper alloy contains at least one element selected from the group consisting of n and Ca in an amount of 0.01% or more and 0.5% or less. . 5. The method for producing a copper alloy according to claim 1, wherein the temperature on the inlet side in the hot rolling step is 900 to 1000 ° C., and the temperature on the final pass outlet side is 600 to 1000 ° C. A method for producing a copper alloy having excellent strength stability and heat resistance, wherein the temperature is 850 ° C. and the average cooling rate from the entrance side to the exit side of the final pass is 0.1 to 5 ° C./sec.