JP4459067B2 - High strength and high conductivity copper alloy - Google Patents

Description

  The present invention relates to a high-strength, high-conductivity copper alloy used for electrical and electronic parts such as lead frames, terminals, connectors, etc., and in particular, a high-strength, high-conductivity copper alloy excellent in shear workability such as press punching. About.

  Conventionally, various electric / electronic parts as described above are generally required to have characteristics such as high strength, high conductivity, and bending workability. Therefore, Cu—Fe—P system having these characteristics is required. Many copper alloys are used. For example, C19210 alloy (Fe: 0.05 to 0.15 mass%, P: 0.025 to 0.040 mass%) is a standard because it is excellent in strength and conductivity among copper alloys. Many are used as alloys.

  With recent reductions in the size and size of various electrical and electronic devices, the electrical and electronic components used therefor are increasingly required to be miniaturized. For example, lead frames used in semiconductor elements such as ICs are strongly required to reduce lead widths and lead-to-lead distances and improve their dimensional accuracy for miniaturization. The requirements for technology and materials that enable punching of such miniaturized parts with high dimensional accuracy are the same for electrical and electronic parts such as terminals and connectors. Furthermore, in order to improve the productivity of the press punching process, there is a strong demand for a material that can reduce the wear of the mold used for the punching process and extend the life of the mold.

  However, the high-strength and high-conductivity copper alloy (for example, C19210 alloy) as described above is close to pure copper in which the addition of different elements is suppressed as much as possible in order to ensure high conductivity (conductivity: about 90% IACS). Since it has a composition, it has the feature of being rich in ductility. However, in the case of punching processing, this acts reversely and the shear rate (the area ratio of the shear surface in the cut surface) increases, so that the lead width and the distance between the leads are reduced and the dimensional accuracy is improved. When the clearance of the punching die is reduced, “sag” and “burr” are likely to occur, and on the contrary, there may be a problem that the dimensional accuracy is lowered. In addition, since the shear rate at the time of punching is large, the contact time between the material and the mold becomes long, so that there is a case in which problems such as increased mold wear and shortened mold life occur.

  When the above problems occur, C19400 alloy (Fe: 2.1 to 2.6%, P: 0.015 to 0.15%, Zn: 0.05 to 0.20%) or C50715 Responding to changes to materials with a large amount of different elements such as alloys (Fe: 0.05 to 0.15%, P: 0.025 to 0.040%, Sn: 1.5 to 2.5%) There was a case. Since these alloys have a large amount of different elements compared to C19210 alloy, the ductility is small, and as a result, the shear rate during punching is small, the lead width and the distance between leads are reduced, the dimensional accuracy is improved, and the mold wear is reduced. Can handle the decline. However, on the other hand, since the amount of different elements is large, inevitably a significant decrease in conductivity (C19400 alloy: conductivity 65% IACS, C19210 alloy: conductivity 35% IACS) is unavoidable.

From the above situation, in order to improve the shear workability of the Cu—Fe—P based copper alloy, proposals shown in the following Patent Documents 1 and 2 have been made. However, in Patent Document 1 described below, since Sn is added at a relatively high concentration, the shear workability is improved, but the conductivity is inevitably lowered. Moreover, although the following patent document 2 is a proposal which tries to improve shear workability in the state which ensured high electrical conductivity, the addition of Pb is permitted for it. Certainly, Pb is an element that can effectively improve the shear workability, but it is not desirable from the environmental viewpoint.
In addition, various proposals have been made as shown in Patent Documents 3 to 7 below. However, in these patent documents 3, 4 and 7, it is presumed that the action of lowering the shear rate is insufficient, and in patent document 5, the process of coarsely growing the precipitate is complicated and expensive. In order to reduce the rate, it is necessary to add a relatively large amount of alloy components, which also increases the cost.

JP-A-62-164843 JP-A-2-209441 JP-A 62-96630 JP-A-6-33170 Japanese Patent Laid-Open No. 10-130755 JP 11-256255 A JP 2000-328158 A

  Therefore, the present invention provides a Cu-Fe-P-based copper alloy used for electrical and electronic parts such as lead frames, terminals, connectors, etc. while maintaining characteristics such as high strength, high conductivity and bending workability. The purpose is to improve shear workability such as press punching. Specifically, an object is to provide a high-strength, high-conductivity copper alloy having a low shear rate when punching is performed. It is also an object of the present invention to provide such a copper alloy at a low cost. In addition, in this invention, a shear rate means the area ratio of the shear surface in a cut surface.

The high-strength and high-conductivity copper alloy according to the present invention includes Fe: 0.01 to 0.5 mass%, P: 0.01 to 0.3 mass%, and Mg, Si, Cr, Ti, Zr, and Al. 0.001 to 0.1% by mass of at least one element among them, Fe / P being a mass ratio of Fe and P is 0.5 to 6.0, and the balance is from Cu and inevitable impurities. In the copper alloy structure, particles mainly containing at least one oxide of Mg, Si, Cr, Ti, Zr, and Al are included, and the distribution density of particles having a major axis of 0.1 μm or more is 0. 0.1 to 100 particles / 100 μm ² , and the distribution density of particles having a major axis exceeding 10 μm is 0.001 particles / 100 μm ² or less. The distribution density of particles having a major axis exceeding 10 μm is preferably 0/100 μm ² . The said copper alloy can also contain Zn: 0.005-0.5 mass% and / or Sn: 0.001-0.5 mass% further.

According to the present invention, while maintaining characteristics such as high strength, high conductivity and bending workability in Cu-Fe-P based copper alloys used for electrical and electronic parts such as lead frames, terminals and connectors, Shear processability such as press punching can be improved (shear rate is reduced). By improving the shear workability, it is difficult for “sag” and “burr” to occur, and it is possible to perform punching with high dimensional accuracy even for miniaturized parts. Further, there is an advantage that the wear of the punching die is reduced, the die life can be extended, and the productivity is improved.
Further, the copper alloy of the present invention has few alloy components, and rolling and heat treatment after melting and casting can be performed by a usual method, and there is an advantage that it can be manufactured at a low cost because it does not require a complicated process.

The reason why the composition and structure of the copper alloy according to the present invention are limited as described above will be described below.
(Fe: 0.01 to 0.5% by mass)
Fe is an element necessary for improving strength and heat resistance by precipitating as fine precipitate particles in a copper alloy. If the content is less than 0.01%, fine precipitate particles are insufficient. Therefore, the content of 0.01% or more is necessary to effectively exhibit the effect of increasing the strength. However, if the content exceeds 0.5%, an increase in electrical conductivity cannot be achieved. Further, if it is attempted to increase the precipitation amount of the precipitate particles in order to increase the conductivity, the precipitation particles are coarsened, and on the contrary, the fine precipitate particles are insufficient. For this reason, intensity | strength falls and high intensity | strength and high electrical conductivity cannot be made compatible. Therefore, the Fe content is in the range of 0.01 to 0.5 mass%. In order to further increase the electrical conductivity, the Fe content is more preferably 0.25% by mass or less.

(P: 0.01 to 0.3% by mass)
P is an element necessary for improving the strength and heat resistance of the copper alloy by forming a precipitate with Fe, in addition to having a deoxidizing action. If the content is less than 0.01%, fine precipitate particles are insufficient. Therefore, the content of 0.01% or more is necessary to effectively exhibit the effect of increasing the strength. However, if it exceeds 0.3% and is contained excessively, the electrical conductivity is lowered, and a high electrical conductivity cannot be achieved. Moreover, hot workability also falls. Therefore, the P content is in the range of 0.01 to 0.3% by mass. In order to further increase the electrical conductivity, the P content is more preferably 0.15% by mass or less.

(Fe / P: 0.5-6.0)
In order to effectively deposit fine precipitate particles and achieve high strength and high conductivity, not only the individual content ranges of Fe and P but also the mass ratio of Fe and P (Fe / P) Must also be specified. If Fe / P is less than 0.5, P becomes excessive and is dissolved in the copper matrix, the conductivity is lowered, and high conductivity cannot be achieved. On the other hand, when Fe / P exceeds 6.0, on the contrary, Fe becomes excessive and coarsely generated as single Fe particles, so that the strength decreases. Therefore, Fe / P is set to a range of 0.5 to 6.0. In order to further increase the electrical conductivity, Fe / P is more preferably in the range of 2.0 to 4.0.

(At least one element of Mg, Si, Cr, Ti, Zr, Al: 0.001 to 0.1% by mass)
Mg, Si, Cr, Ti, Zr, and Al all react with O (oxygen) in the molten copper at the time of melting and casting to become particles mainly composed of oxide, and are dispersed in the copper alloy structure or hot rolled. It reacts with dissolved O (oxygen) in the base material to produce particles mainly composed of oxide, and has the effect of improving press punchability. When these oxide-based particles are dispersed in the copper alloy structure, it becomes a source of microcracks due to stress applied during shearing, and the shear workability can be effectively improved. That is, it becomes easy to break and the shear rate becomes small. If the amount of Mg, Si, Cr, Ti, Zr, Al is less than 0.001%, the number of particles mainly composed of oxide is insufficient. It is necessary to contain 001% or more. However, if the content exceeds 0.1% by mass, the amount of elements that are in a solid solution state without reacting with O (oxygen) in the molten copper increases, resulting in a decrease in conductivity. Therefore, the content of Mg, Si, Cr, Ti, Zr, and Al is set to 0.001 to 0.1% by mass.

(Zn: 0.005 to 0.5 mass%)
Zn is an element effective in improving the heat-resistant adhesion of solder used for joining electronic components and Sn plating used for ensuring the reliability of electrical contacts and suppressing thermal delamination. In order to exhibit such an effect effectively, it is preferable to contain 0.005% or more. However, if it exceeds 0.5% and is contained excessively, it not only deteriorates the wetting and spreading properties of solder and molten Sn but also decreases the conductivity. Therefore, Zn is selectively contained in the range of 0.005 to 0.5 mass%. In order to further increase the electrical conductivity, the Zn content is more preferably 0.2% by mass or less.

(Sn: 0.001 to 0.5 mass%)
Sn contributes to the improvement of the strength and shear workability of the copper alloy. In order to exhibit such an effect effectively, it is preferable to contain 0.001% or more. However, if the content exceeds 0.5%, the electrical conductivity is greatly reduced. Therefore, Sn is selectively contained in the range of 0.001 to 0.5 mass%. In order to further increase the electrical conductivity, the Sn content is more preferably 0.2% by mass or less.

  Other elements such as Ni, Co, and Mn are impurity elements, which easily generate coarse crystals / precipitates, and easily cause a decrease in conductivity. Therefore, it is preferable to suppress the content to a minimum amount of 0.5% by mass or less and further 0.1% by mass or less as much as possible. In addition, elements such as B, C, Na, S, Ca, As, Se, Cd, In, Sb, Pb, Bi, and MM (Misch Metal) contained in a small amount in the copper alloy also have conductivity. Since it tends to cause a decrease, it is preferable to suppress the total content to 0.1% by mass or less as much as possible. In particular, As, Cd, and Pb are harmful elements in terms of the environment, and are each independently preferably 0.005% or less, and more preferably 0.001% or less.

(Copper alloy structure condition)
The particles mainly composed of oxides of Mg, Si, Cr, Ti, Zr, and Al in the present invention are easily confirmed when the cross-sectional structure of the copper alloy material is observed by SEM (magnification: about 1000 to 10000 times). Particles of a size as large as possible, and are compounds mainly composed of Mg—O, Si—O, Cr—O, Ti—O, Zr—O, and Al—O. These include P in the alloy components and unavoidable In some cases, S, which is an impurity, is added to form a composite compound. However, in the present invention, particles including these are mainly composed of oxides.
In the production of a copper alloy, such oxide-based particles, for example, react with O (oxygen) in molten copper at the time of melt casting and disperse in the copper alloy structure or during hot rolling. In some cases, it reacts with dissolved oxygen in the material.

In the present invention, among such particles mainly composed of oxide, particles having a particle size (major axis) of 0.1 μm or more have a distribution of 0.1 to 100/100 μm ² in the cross-sectional observation of the copper alloy sheet. Particles dispersed by density and having a particle size exceeding 10 μm are suppressed to a distribution density of 0.001 / 100 μm ² or less. In addition, since the particle | grains which have an oxide as a main body often do not become a perfect circle, the particle size said here is made into the major axis of a particle | grain.

When the particle size (major axis) of such an oxide-based particle is less than 0.1 μm, the effect of generating microcracks due to the stress applied during shearing is small, and the shear workability is effectively improved. I can't let you. Accordingly, in the present invention, the lower limit of the particle size (major axis) of the particles mainly composed of oxide is defined to be 0.1 μm or more.
Moreover, if the distribution density of particles having a particle size of 0.1 μm or more among particles mainly composed of oxide is less than 0.1 particles / 100 μm ² , the number of particles to be effective is insufficient and effective shearing is performed. Can not improve. On the other hand, when the distribution density of particles having a particle size of 0.1 μm or more exceeds 100 particles / 100 μm ² , the effect of improving the shear workability is saturated and the bending workability is hindered. Therefore, in the present invention, the distribution density of particles having a particle size of 0.1 μm or more among particles mainly composed of oxide is defined as 0.1 to 100 particles / 100 μm ² .

On the other hand, when the particle size of the oxide-based particles exceeds 10 μm, it becomes a source of microcracks, but becomes a factor that hinders bending workability as another characteristic. Accordingly, it is desirable that particles having a particle size of more than 10 μm do not exist among particles mainly composed of oxide, and even if they exist, the distribution density is limited to 0.001 particles / 100 μm ² or less.
In the present invention, among the particles mainly composed of oxide, the distribution density of particles having a particle size (major axis) of 0.1 μm or more is specified. It is permissible for particles mainly composed of oxides of less than 0.1 μm to be present in the copper alloy structure as appropriate.

The particle size (major axis) of the oxide-based particles referred to in the present invention is a particle mainly composed of oxides that is recognized when the cross-sectional structure of the copper alloy material is observed with a scanning electron microscope (SEM) or the like. The distribution density is the average of the number measured by observation with SEM (magnification: about 1000 to 10000 times) as the number measured per 100 μm ^2. It is more preferable to observe and average.

(Production method)
Next, preferable manufacturing conditions for setting the copper alloy structure to the structure defined in the present invention will be described below. Here, among the above-described particles mainly composed of oxides of Mg, Si, Cr, Ti, Zr, and Al, particles having a particle size of 0.1 μm or more are 0.1 to 100 particles / 100 μm ² . In order to control particles having a particle size exceeding 10 μm to be dispersed with a distribution density of 0.001 / 100 μm ² or less, it is effective to perform melt casting under the following conditions in production.

As described above, the oxide-based particles in the present invention are mainly composed of a compound phase that reacts with O (oxygen) in molten copper and is dispersed in the copper alloy structure during melt casting. In order to uniformly disperse such a compound phase in an appropriate size, O (O) in molten copper before adding components (Mg, Si, Cr, Ti, Zr, Al) which are base materials of oxides is added. (Oxygen) amount is controlled to about 20 to 100 ppm. Usually, the melting casting of a copper alloy is performed so that the amount of O (oxygen) in the molten copper is kept as low as possible (less than 20 ppm) so that the additive components are not oxidized and consumed. Therefore, it is effective to add components (Mg, Si, Cr, Ti, Zr, Al) which are base materials of oxides while maintaining an appropriate amount of O (oxygen). When the component (Mg, Si, Cr, Ti, Zr, Al) that is the base material of the oxide is less than 20 ppm in the molten copper before adding the component (Mg, Si, Cr, Ti, Zr, Al), the oxide that should exhibit the effect is mainly used. The number of particles is insufficient, and the shear processability cannot be improved effectively. Also, when the amount of O (oxygen) in the molten copper exceeds 100 ppm, particles mainly composed of oxides with a particle size exceeding 10 μm are formed, or oxides having a particle size of 0.1 μm or more are mainly composed. This is because a situation occurs in which the distribution density of the particles exceeds 100 particles / 100 μm ^2, which is an obstacle to bending workability.

  More specifically, after dissolving copper under a charcoal coating, Fe and P are added to control the O (oxygen) concentration in the molten copper to 20 to 100 ppm. The following components (Mg, Si, Cr, Ti, Zr, Al) are added. In addition, in the process up to the addition of the component that becomes the base of the oxide and the casting, when the component is added, it is pushed into the molten copper to react with O in the molten copper (if it floats on the molten copper) It reacts with O in the atmosphere to produce coarse oxide particles), and after adding the component, it is allowed to stand for 5 minutes or longer (slow stirring is possible), and then the surface of the molten copper is oxidized (oxidized). It is important to cast so as not to entrain the material layer. The standing for 5 minutes or more has an effect of allowing coarse oxide particles to float on the surface of the molten copper and dispersing particles mainly composed of an appropriate size of oxide.

  It is not necessary to change the manufacturing process after the melt casting, and the manufacturing process can be performed in the same process as that of a conventional method. That is, the ingot produced by the above method is heated or homogenized and then hot-rolled, and the hot-rolled plate is water-cooled. Thereafter, primary cold rolling, which is said to be intermediate, is performed, and after annealing and washing, finish (final) cold rolling is performed to obtain a copper alloy sheet having a product thickness.

  Examples of the present invention will be described below. A copper alloy plate was produced by casting a copper alloy having each composition shown in Table 1, and each characteristic was evaluated.

As a concrete method for producing a copper alloy plate, molten copper is manufactured under charcoal coating in a kryptor furnace, Fe and P are added, various components are added, and cast into a book mold, and the thickness is 50 mm. An ingot having a width of 70 mm and a length of 200 mm was obtained. In addition, when adding various components, it was made for the O (oxygen) density | concentration in molten copper to be in the range of 20-100 ppm. Moreover, when adding various components, it pushed in the molten copper, and after addition, it left still for 5 minutes or more.
And after chamfering each ingot, it hot-rolled at the temperature of 900 degreeC, and water-cooled by 15 mm in thickness. Then, after chamfering the surface of this rolled plate to remove the oxide scale, cold rolling → annealing → cold rolling was performed to obtain a copper alloy plate having a thickness of 0.15 mm.

With respect to the copper alloy plate thus obtained, in each example, a sample was cut out from the copper alloy plate, and the particle size (major axis) and distribution density (particles / 100 μm) of particles mainly composed of oxide were observed by cross-sectional structure observation. ² ) Measurement, tensile strength, hardness, electrical conductivity measurement, shear workability (shear rate) and bending workability were investigated. These results are shown in Table 2.

In the structure observation, the number of particles having a particle size (major axis) of 0.1 μm or more when the copper alloy structure is observed with a 2000-fold scanning electron microscope is measured with an arbitrary three visual fields by the measurement method described above. The distribution density (pieces / 100 μm ² ) was calculated by averaging the results.
The tensile test was performed by creating a JIS-5 test piece cut out parallel to the rolling direction. The hardness test was performed with a load of 0.5 kg using a micro Vickers hardness tester.
The electrical conductivity was calculated by an average cross-sectional area method by processing a strip-shaped test piece having a width of 10 mm and a length of 300 mm by milling, measuring the electrical resistance with a double bridge resistance measuring device.

  As shown in FIG. 1, the shear rate is punched by a punching press (clearance: 5%) so that a lead having a width of 1 mm × a length of 10 mm is perpendicular to the rolling direction of the copper alloy sheet 1. The center of the punched hole 2 is cut along the length direction (the cut portion is indicated by a broken line 3), the cut surface of the punched hole 2 is observed from the direction of the arrow 4, and the cut surface using an optical microscope is observed. It was determined by image analysis from surface photographs. The shear rate is the area ratio of the shear plane in the cut plane (the area of the shear plane / the area of the cut plane). The area of the cut plane is the thickness of the copper alloy sheet 0.15 mm × measured width 0.5 mm, The area was the area of the shear plane within the measurement width of 0.5 mm. Three holes were punched out for each sample, and three holes were measured for each hole (total of 9 points), and the average value was obtained.

  The bending workability is determined by conducting a W bending test [R (bending radius) / t (plate thickness) = 2, perpendicular to the rolling direction)] stipulated in the Japan Copper and Brass Association Standard JBMA-T307 and observing the surface of the bent portion. Evaluation was made in five stages (A: no wrinkle, B: small wrinkle, C: large wrinkle, D: small crack, E: large crack). A to C are acceptable levels, and D to E are unacceptable levels.

  Of the examples shown in Tables 1 and 2, No. 1 to 20 are examples of the present invention. 21 to 32 are comparative examples. In this example, the basic component Fe was 0.1% by mass and P was 0.03% by mass, and the concentrations of various other components were varied.

No. 1-3, 4-6, 7-9, 16-18 are examples of the present invention when the component concentrations of Mg, Si, Cr, and Al are changed, respectively, but the concentration of each component increases, It can be seen that the distribution density of particles mainly composed of oxides of each component having a particle size of 0.1 μm or more increases, and accordingly, the shear rate by press punching decreases, and the shear processability is improved.
In addition, the conductivity decreases as the concentration of each component increases, but even in the highest concentration examples (No. 3, 6, 9, 18), it is possible to maintain a conductivity of about 80% IACS, The W bending workability was also maintained at an acceptable level in the C evaluation.

No. 10 to 12 and 13 to 15 are examples of the present invention when the component concentrations of Ti and Zr are changed, respectively, and the concentration of each component is increased and the particle size is 0.1 μm or more as described above. It can be seen that the distribution density of particles mainly composed of oxides of each of the above increases, the shear rate by press punching decreases accordingly, and the shear workability improves.
Moreover, also in the example (No.12,15) with the highest density | concentration, the electrical conductivity close | similar to 90% IACS and the W bending workability of the acceptable level were able to be maintained.

  No. 19 and 20 are No. This is an example of the present invention in which Zn and Sn as selective elements are each added in an amount of 0.1% by mass based on 2 (containing 0.01% by mass of Mg). No. No. 19 Zn additive is No. Compared to 2, there is no significant change in properties other than causing a slight increase in strength and a decrease in conductivity, and there is no problem in selectively adding an appropriate amount for the purpose of improving the heat-resistant adhesion of solder and Sn plating. No. No. 20 Sn additive is No. Although it may be selectively added since it is effective in improving the strength and shearing workability compared to 2, it is preferable to make it an appropriate amount because the electrical conductivity and bending workability are liable to decrease.

  No. 21, 23, 25, 27, 29, and 31 have component concentrations of Mg, Si, Cr, Ti, Zr, and Al below the lower limit of the present invention, respectively, and the distribution density of particles mainly composed of oxides of the respective components is It is a comparative example in the case where the lower limit of the present invention is exceeded, and it can be seen that the shear density is large and the shear workability is inferior when the distribution density of the particles mainly composed of oxide is smaller than that of the present invention.

In contrast, no. 22, 24, 26, 28, 30, and 32 have Mg, Si, Cr, Ti, Zr, and Al component concentrations exceeding the upper limit of the present invention, and the distribution density of particles mainly composed of the respective oxides. Although it is a comparative example when exceeding the upper limit of the present invention, both are found to have a low shear rate and excellent shear workability, all of the W bending workability are D evaluations and fail levels. I understand. Moreover, since the component concentration is high, the conductivity is greatly reduced, and some of the components are less than 70% IACS.
In addition, No. which is an example of the present invention. 1-20 and No. 1 as a comparative example. Nos. 21, 23, 25, 27, 29, and 31 have a particle distribution density of 0 particles / 100 μm ² mainly composed of an oxide having a particle diameter exceeding 10 μm. Even 22, 24, 26, 28, 30, and 32 were very low levels of 0.001 piece / 100 μm ² or less.

It is a figure explaining the measuring method of a shear rate.

Explanation of symbols

1 Copper alloy plate 2 Punched hole 3 Cut location

Claims (3)

Fe: 0.01 to 0.5 mass%, P: 0.01 to 0.3 mass%, and at least one element of Mg, Si, Cr, Ti, Zr, and Al is 0.001 to 0 0.1 mass%, Fe / P which is a mass ratio of Fe and P is 0.5 to 6.0, and is composed of the balance Cu and inevitable impurities, and Mg, Si, Cr, Particles mainly containing at least one oxide of Ti, Zr, and Al are included, and the distribution density of particles having a major axis of 0.1 μm or more is 0.1 to 100/100 μm ² , and the major axis A high-strength, high-conductivity copper alloy characterized by having a distribution density of particles exceeding 10 μm of 0.001 particles / 100 μm ² or less. The said copper alloy contains Zn: 0.005-0.5 mass% further, The high intensity | strength highly conductive copper alloy described in Claim 1 characterized by the above-mentioned. The said copper alloy contains Sn: 0.001-0.5 mass% further, The high intensity | strength highly conductive copper alloy described in Claim 1 or 2 characterized by the above-mentioned.

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