JP2010215935A - Copper alloy and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow the strength and elongation of a copper alloy as an electronic component to be balanced, and to facilitate production control. <P>SOLUTION: Copper alloy contains, by weight, 0.005 to 0.5% Zr and B in the range of 0.2 to 400 ppm, and has a layered structure composed in such a manner that crystal grain layers made of a plurality of flat crystal grains continuous in a plane direction are laminated in a sheet thickness direction, The thickness of the crystal grain layer lies in the range of 20 to 550 nm, A peak value P in a histogram of the thickness of the crystal grain layers in the layered structure lies in the range of 50 to 300 nm, and is also present at the frequency of ≥22% of the total frequency, and the half-value width L thereof is ≤200 nm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a copper alloy that is used for an electrical connection connector, a terminal, a lead frame, a conductive wire, a foil, and the like and has excellent mechanical strength as well as conductivity, and a method for producing the same.

A Cu—Zr alloy is well known as a copper alloy used for electrical connectors, terminals, lead frames, conducting wires, foils and the like.
For example, in Patent Document 1, when trying to increase the strength of a base material using a rolling method, when the rolling rate is increased, the strength of the base material made of a copper alloy is increased and the elongation is also improved. As a copper alloy with excellent bending workability and excellent heat-resistant creep characteristics, it contains zirconium in the range of 0.005 to 0.5 by weight%, and has fine and large crystal grains. And having a specific crystal grain size distribution in combination. In this copper alloy, the combination of fine crystal grains and large crystal grains works to suppress cross-slip that occurs at the interface between crystal grains, bringing the balance of strength and elongation to the copper alloy, Therefore, it is possible to prevent the deterioration of the thermal creep characteristics that are observed when the material is composed of only crystal grains, and to have a good balance between strength and elongation, as well as good bending workability.

  Patent Document 2 discloses strength and conductivity that can be selected in a wide range according to the use of an electronic component in a simple alloy composition composed of a Cu-Zr binary system or a Cu-Zr-B ternary system. As a copper alloy having both, the Cu matrix phase and the eutectic phase of the Cu matrix phase and either the Cu matrix phase and the Cu-Zr or Cu-Zr-B or both compounds are mutually bonded. A copper alloy having a two-phase structure in which adjacent Cu matrix crystals are intermittently in contact with each other is shown.

Japanese Patent No. 4118832 JP 2005-281757 A

  By the way, although the copper alloy described in Patent Document 1 has good bending workability with a good balance between strength and elongation, with the recent demand for smaller and thinner electronic parts, There has been a demand for further improvement in the balance of elongation, and a copper alloy in which these are balanced at a high level is desired.

  On the other hand, the copper alloy described in Patent Document 2 is manufactured by a refractory melting method such as levitation melting that melts the molten metal so as not to contact the furnace wall as much as possible. Complicated production management is required, for example, heat treatment is required before inter-processing.

The present invention was made in view of such circumstances, and an object thereof is to provide a copper alloy capable of balancing strength and elongation as an electronic component at a high level and facilitating manufacturing management, and a manufacturing method thereof. To do.

  In general, it is considered effective to refine crystal grains to the nanoscale to improve the strength, but it is not possible to improve the elongation simply by miniaturization. The inventor pays attention to the structure of the longitudinal cross-sectional structure along the rolling direction (RD direction), and has a lamellar structure in which fine and flat crystal grains are arranged in layers and the crystal grain layers are stacked. In addition, it has been found that when the thickness (interval) of the crystal grain layer is uniform in each layer and is stable as a layered structure, the strength and the elongation are balanced at a high level.

  That is, the copper alloy of the present invention is a copper alloy containing Zr in a range of 0.005% to 0.5% and B in a range of 0.2 ppm to 400 ppm by weight ratio, and a plurality of flat crystal grains are in a plane. The crystal grain layer in the layered structure has a layered structure in which the crystal grain layers continuous in the direction are stacked in the plate thickness direction, and the thickness of the crystal grain layer is in the range of 20 nm to 550 nm. The peak value in the histogram of the thickness is in the range of 50 nm to 300 nm and at a frequency of 22% or more of the total frequency, and the half value width is 200 nm or less.

In this copper alloy, the individual thickness of each crystal grain layer in the layered structure is in the range of 20 nm to 550 nm, and in the thickness histogram, the peak value exists at a high frequency of 22% or more, and the half-value width Is as narrow as 200 nm or less, and its histogram curve has a shape that protrudes into a sharp mountain with a narrow width. In other words, the thickness of each crystal grain layer in the layered structure is thin and uniform. When the thickness of the crystal grain layer is thin and uniform, the strength is large. When the peak value exceeds 300 nm, sufficient strength cannot be obtained. On the other hand, it is difficult in terms of manufacturing technology to make the peak value less than 50 nm, which is not practical. More preferably, the peak value is in the range of 50 nm to 250 nm. In addition, when the frequency of the peak value is less than 22%, the histogram curve becomes gentle and the variation in the thickness of the crystal grain layer becomes large, so that improvement in strength cannot be expected.
And by using such a stable copper alloy having a layered structure, the balance between strength and elongation is improved at a high level.

  Here, the addition of Zr is effective in improving the strength, but if the added amount is less than 0.005% by weight, the strength is not sufficiently improved, and even if it exceeds 0.5%, No further improvement in strength can be expected. In addition, when the Zr content is 0.005% or more, the layered structure is developed and stabilized. On the other hand, if it exceeds 0.5%, the elongation decreases, which is not preferable. Therefore, the Zr content is set to 0.005% to 0.5% by weight.

  Adding a small amount of B has an effect of stabilizing the layered structure evenly and densely, and imparts an appropriate elongation (ductility). However, if the amount added is less than 0.2 ppm by weight, the layered structure The effect of reducing the variation in the thickness of each crystal grain layer is poor, and even if it exceeds 400 ppm, no further effect can be expected. Conversely, there is a problem that ductility is remarkably increased and the tensile strength is lowered. Therefore, the content of B is set to 0.2 ppm to 400 ppm by weight.

  The method for producing a copper alloy of the present invention is based on a weight ratio of Zr of 0.005% to 0.5% and B of 0.2 ppm to 400 ppm. A first step of rolling at a temperature of 10 ° C. to 1030 ° C., and performing a solution treatment comprising a hot rolling process in which the rolling rate of the final pass at this temperature is 25% or more and a subsequent rapid cooling process by water cooling; The second step of subjecting the base material that has undergone the first step to a cold rolling treatment with a rolling rate of 90% or more, and the base material that has undergone the second step at 300 ° C. to 380 ° C. for 1 hour to And a third step of performing a heat treatment for 8 hours.

By subjecting a copper alloy containing a predetermined amount of Zr and B to a solution treatment at a high temperature of 930 ° C. to 1030 ° C., Zr can be sufficiently dissolved in the base material, and the precipitation hardening effect in the subsequent third step is effective. To. If the temperature does not reach 930 ° C., Zr cannot be sufficiently dissolved, and precipitation due to later aging becomes insufficient.
In addition, the crystal grains tend to become coarse due to the heat during the hot rolling, and the rolling rate of the final rolling pass during the hot rolling is reduced to a strong pressure of 25% or more, which is larger than usual. While suppressing the growth of the grains, the shape is flattened in the rolling direction while making the grains fine by the large deformation. Then, by rapidly cooling from this hot hot rolling, the dissolved Zr is brought into a supersaturated state.

  Then, it is further thinned and imparted with strain by the subsequent cold rolling process of the second step, and the crystal grains are further refined to increase the strength. Moreover, flat crystal grains develop into a layer by this cold rolling, the thickness of the crystal grain layer is reduced, and a lamellar structure in which the flat crystal grain layers are stacked in the plate thickness direction is formed. In this lamellar structure, the crystal grains are deformed so as to be compressed in the plate thickness direction and spread in the plane direction, and the grain boundaries for dislocations become larger and the strength is improved. When the rolling rate of this cold rolling is less than 90%, the thickness of each crystal grain layer of the layered structure becomes non-uniform.

By the next heat treatment, Zr that has been dissolved in a supersaturated state is precipitated, and a part thereof also reacts with B to obtain a copper alloy that balances strength and elongation at a high level. Zr, which has been dissolved in the base material by solution treatment, is precipitated by the subsequent heat treatment, the precipitate has an effect of improving the strength of the alloy, but on the other hand, the elongation is reduced. In general, the elongation decreases when the strength is increased. In the present invention, Zr that has been dissolved in the supersaturated state gradually precipitates due to aging, but by setting the heat treatment to a relatively low temperature, Zr remaining in the crystal grains without being completely precipitated can be obtained. Since it reacts with B to form a compound and this compound develops a layered structure, it is assumed that strength and elongation are balanced at a high level. If the heat treatment temperature exceeds 380 ° C., the effect of improving the elongation cannot be obtained. Further, if it is too long to exceed 8 hours, recrystallization is caused, which is not preferable.
The copper alloy obtained by this manufacturing method has good elongation characteristics as well as high strength, and is excellent in workability such as bending.

  According to the present invention, the combined effect of the addition of Zr and B and the uniform layered structure of the flat crystal grain layer can provide a copper alloy that balances strength and elongation at a high level, thereby reducing the size of electronic components. Therefore, it is possible to suitably cope with the thinning. Moreover, the manufacturing method does not require special complicated management, and can be manufactured easily.

It is the schematic diagram of the layered structure which observed the copper alloy which concerns on this invention by TEM. It is a histogram curve which shows distribution of the thickness of each crystal grain layer in the layered structure of FIG.

Embodiments of the present invention will be described below.
The copper alloy of this embodiment contains Zr in the range of 0.005% to 0.5% by weight and B in the range of 0.2 ppm to 400 ppm by weight. As shown in FIG. 1, a crystal grain layer 2 composed of a plurality of flat crystal grains 1 has a layered structure 3 formed by stacking in the plate thickness direction.

Zr has the effect of precipitating on the crystal grain surface and improving the strength by an aging treatment after the solution treatment described later. If the content is less than 0.005% by weight, the strength is not sufficiently improved, and if it exceeds 0.5%, the effect of improving the strength is saturated and cannot be expected any more. Rather, if it exceeds 0.5%, the elongation is reduced.
In addition, when the Zr content is 0.005% or more, the layered structure is developed and stabilized.
Adding a small amount of B has the effect of stabilizing the layered structure evenly and imparts appropriate elongation. However, if the amount added is less than 0.2 ppm by weight, each crystal grain layer of the layered structure The effect of reducing variation in thickness is poor, and even if it exceeds 400 ppm, the effect is saturated, and conversely, the strength is lowered.

  In addition, for this copper alloy, one or more elements of chromium, silicon, magnesium, aluminum, iron, titanium, nickel, phosphorus, tin, zinc, calcium and cobalt are selected and expressed in weight%. , 0.001 or more and 3.0 or less. It is preferable to add these elements to the copper alloy as appropriate, since the strength can be further improved.

  Further, this copper alloy includes carbon, oxygen, and oxidation of one or more elements of chromium, silicon, magnesium, aluminum, iron, titanium, nickel, phosphorus, tin, zinc, calcium, and cobalt. Any one or two or more of the products may be selected and contained in the range of 0.0005 to 0.005 by weight%. It is preferable to appropriately contain these elements in the copper alloy because it effectively acts as a starting point for fracture during press punching, improves the press punchability, and consequently reduces mold wear.

  As shown in FIG. 1, the layered structure 3 is formed by stacking crystal grain layers 2 in which flat crystal grains 1 are continuous in a plane direction. 1 schematically shows the structure of a longitudinal section (the surface viewed in the TD direction) along the rolling direction (RD direction). The horizontal direction is the rolling direction (RD direction), and the vertical direction (vertical direction) is the plate thickness direction (ND direction). Then, as shown by hatching one crystal grain 1, each crystal grain 1 is flat and elongated in the rolling direction (RD direction), and the adjacent crystal grain 1 is The layers are constituted by the plurality of crystal grains 1 in a continuous state, arranged so as to be continuous in the rolling direction (RD direction). In the present invention, a crystal grain layer 1 in which crystal grains 1 are continuously formed is referred to as a crystal grain layer 2, and a plurality of crystal grain layers 2 are stacked in the plate thickness direction (ND direction). It is called organization 3. Such a layered structure 3 is confirmed by observing a longitudinal section (surface viewed in the TD direction) in the rolling direction (RD direction) with a transmission electron microscope (TEM). be able to.

In this layered structure 3, the thickness of each crystal grain layer 2 is set in the range of 20 nm to 550 nm. The thickness distribution of the crystal grain layer is represented by a histogram curve as shown in FIG. This histogram shows an arbitrary straight line X in the plate thickness direction (ND direction) perpendicular to the rolling direction (RD direction) in the layered structure observed by TEM, as shown by the one-dot chain line in FIG. , And measure the distance (interval) T between the intersections of the straight line X and the interface between the crystal grain layers 2, and measure the distance T as the thickness of the crystal grain layer 2 to measure 200 pieces. It is a distribution. The class interval when the measurement value is used as a histogram is, for example, 50 nm. In the histogram curve of FIG. 2, when the peak value is P and the half width is L, the peak value P is in the range of 50 nm to 300 nm, and the frequency of the peak value P is 22% or more of the total frequency, Further, the half width L is set to 200 nm or less. In other words, the histogram curve has a narrow width and a sharp mountain shape protruding upward.
In other words, it means that the thickness of each crystal grain layer 2 in the layered structure 3 is uniform and uniform. The thin and uniform crystal grain layer 2 is advantageous in improving the strength, and it is more preferable that the peak value P exists in the range of 50 nm to 200 nm. It is more preferable that the half width is 170 nm or less because the layered structure 3 becomes more uniform.

Next, a method for producing such a copper alloy will be described.
In this manufacturing method, a copper raw material is melted in a refractory furnace, and copper is added to the molten copper at a weight ratio of 0.005% to 0.5% and B in a range of 0.2 ppm to 400 ppm. The base material was cast. Then, a first step of performing a solution treatment while hot rolling the cast base material, a second step of performing cold rolling thereafter, and performing a heat treatment for aging or annealing the base material after cold rolling Each process in the third step is sequentially performed. Hereinafter, it demonstrates in order of this process.

<First step>
The first step is a process in which the base material is hot-rolled at a high temperature and then rapidly cooled.
In hot rolling, the base material is heated to a temperature of 930 ° C. to 1030 ° C. to a red hot state, and the gap between the rolling rolls is gradually reduced while passing between the rolling rolls a plurality of times (5 to 10 times). Then, the base material is rolled to a predetermined thickness. The rolling rate at this time is 22% or more, for example, about 24% before the final pass. By making the rolling rate at this stage 22% or more, the crystal grains can be made uniform. This rolling rate is the reduction rate of the thickness of the base material after passing the rolling roll relative to the thickness of the base material before passing the rolling roll (or the gap between the rolling rolls of the current pass with respect to the gap between the rolling rolls in the previous pass) The reduction rate at this stage is an average of the rolling rates at each time.

And in this final pass of hot rolling, it is processed at a rolling rate of 25% or more. Increasing the rolling rate of this final pass to 25% or more is to suppress the growth of crystal grains by heating under high pressure and to impart strain due to the large deformation force in the rolling direction while refining the crystal grains. This is to make the shape flat, and the crystal grain layer in the layered structure after the subsequent cold rolling can be made uniform. More preferably, this final pass should have a rolling rate of 34% or more, for example, a rolling rate of 46%.
Further, Zr is sufficiently dissolved in the base material by this hot rolling. The base material after the hot rolling is finished is a plate having a thickness of about 10 mm to 20 mm.

And it cools rapidly by water-cooling the base material after this hot rolling. The rapid cooling rate is 10 ° C./second or more, preferably 30 ° C./second to 50 ° C./second. By this rapid cooling, a base material in which Zr is dissolved in a supersaturated state is obtained.
Further, the base material is subjected to processing such as chamfering, rough rolling, and polishing, and finally the plate thickness becomes about 1.2 mm to 6.0 mm.

<Second step>
Next, cold rolling is performed at a rolling rate of 90% or more. Even in this cold rolling, the base material is passed between the rolling rolls a plurality of times (5 to 20 times), and the rolling rate at each time is set to 15% to 30%. And the rolling rate becomes 90% or more, for example, a rolling rate of 98%-99% by the rolling of the plurality of times, and the base material is reduced to a plate thickness of 0.12 mm-0.75 mm.
By passing through this cold rolling process, the thickness of each crystal grain layer in the layered structure described later becomes uniform, and the peak value becomes large when the thickness distribution is made into a histogram.

<Third step>
Next, the base material that has undergone the second step is subjected to heat treatment at 300 ° C. to 380 ° C. for 1 hour to 8 hours. This heat treatment is a treatment for aging treatment or strain relief annealing. By this heat treatment, Zr that has been dissolved in the supersaturated state gradually precipitates due to aging, but due to the heat treatment being relatively low temperature, Zr remaining in the crystal grains without being completely precipitated can be expressed as B. Reacts to form a compound. It is assumed that the compound of Zr and B improves the elongation of the base material, and the copper alloy that has undergone the third step balances strength and elongation at a high level.
In this heat treatment, if the temperature is less than 300 ° C., the effect of improving the strength is poor. On the other hand, if the temperature exceeds 380 ° C., the strength increases but the elongation is not sufficient. Further, if the heat treatment time is too long to exceed 8 hours, recrystallization occurs, which is not preferable.

Next, the test results conducted to confirm the performance of the copper alloy thus manufactured will be described.
A copper alloy to which Zr and B were added in the ratios shown in Table 1 was cast and manufactured through the processes from the first step to the third step. The hot rolling conditions in the first step, the rolling rate during the cold rolling in the second step, and the heat treatment conditions in the third step were combined as shown in Table 1. Samples 1 to 14 were prepared in this example, and Samples 15 to 29 were prepared as comparative examples in which the amount of Zr and B added, hot rolling, cold rolling, and heat treatment were not within the scope of the present invention. The final plate thickness was 0.64 mm in all cases.

  The obtained copper alloy sheet was cut in the rolling direction, and its cross-sectional structure was observed with TEM. As described above, the sheet thickness direction (ND direction) perpendicular to the rolling direction (RD direction) was obtained. ), The distance (interval) between the interfaces of each crystal grain layer was measured, and the distance was defined as the thickness of the crystal grain layer. Among the measured values of the thickness of the crystal grain layer, the minimum value, the maximum value, the peak value in the case of the histogram, the frequency, and the half value were obtained. In the histogram, the class was determined with a width of 50 nm, and the frequency (frequency) of the measured value of the thickness of each crystal grain layer was determined for each class. The results are shown in Table 2.

From the results shown in Table 2, in this example, the thickness of the crystal grain layer of the layered structure is uniform, the peak value of the histogram is small, the half value width is small frequently, and the histogram curve is formed in a sharp mountain shape. I understand that
Although specific numerical values are omitted, the peak value slightly changes before and after the heat treatment in the third step, and the peak value of the base material after the third step is about 10% of the base material before the third step. Get smaller.

Next, the tensile strength, 0.2% proof stress, elongation, Vickers strength, and conductivity were measured for the copper alloy plate materials of these examples and comparative examples.
Here, the tensile strength (N / mm ² ), elongation (%), and 0.2% proof stress (N / mm ² ) are determined by the method prescribed in JIS (Z2241) using an Instron universal testing machine. It was measured. The test piece is a JIS No. 5 test piece, and the longitudinal direction of the test piece is L.P. parallel to the rolling direction (RD direction). D. A test piece was obtained. The gauge distance in the elongation test was 50 mm. Vickers hardness (HV) was measured by a method defined in JIS (Z2244). The conductivity (% IACS) was measured by the method defined in JIS (H0505).
The results are shown in Table 3.

As can be seen from Table 3, the samples of the examples have a high tensile strength and a high level of balance with the elongation. Moreover, also in the 0.2% yield strength, Vickers hardness, and electrical conductivity which were measured simultaneously, the copper alloy of a present Example has the characteristic which can be fully satisfied practically.
Thus, since the copper alloy of a present Example is excellent in a mechanical characteristic, it can respond suitably to size reduction and thickness reduction of an electronic component.
In addition, if it is after the heat processing of a 3rd process, you may perform the annealing process for distortion removal as needed, for example at about 400 to 450 degreeC.

1 Crystal grain 2 Crystal grain layer 3 Layered structure

Claims (2)

  A copper alloy containing Zr in a weight ratio of 0.005% to 0.5% and B in a range of 0.2 ppm to 400 ppm, wherein a plurality of flat crystal grains are continuous in a plane direction. Have a layered structure formed by stacking in the plate thickness direction, the thickness of the crystal grain layer is in the range of 20 nm to 550 nm, and the peak value in the histogram of the thickness of the crystal grain layer in the layered structure is A copper alloy characterized by being present in a range of 50 nm to 300 nm and at a frequency of 22% or more of the total frequency, and having a half width of 200 nm or less. While rolling at a temperature of 930 ° C. to 1030 ° C. with respect to a base material made of a copper alloy containing 0.005% to 0.5% Zr and B in a range of 0.2 ppm to 400 ppm by weight ratio, A first step of performing a solution treatment comprising a hot rolling treatment in which the rolling rate of the final pass under temperature is 25% or more and a subsequent rapid cooling treatment by water cooling, and a base material that has undergone the first step A second step of performing a cold rolling treatment with a rolling rate of 90% or more; and a third step of subjecting the base material that has undergone the second step to a heat treatment at 300 ° C. to 380 ° C. for 1 hour to 8 hours. A method for producing a copper alloy, comprising:

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