JP5479002B2 - Copper alloy foil - Google Patents

Description

  The present invention relates to a copper alloy foil excellent in mechanical strength, conductivity, and bending workability used for a laminated board for printed wiring boards, a current collector for lithium ion batteries, and the like.

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 electronic components in a simple alloy composition comprising 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 crystal grains are intermittently in contact with each other is disclosed.

  As a copper alloy foil, Patent Document 3 discloses that at least one of the components in which Cr is 0.01 to 2.0% and Zr is 0.01 to 1.0% in terms of weight ratio of the additive element components. The balance is copper and inevitable impurities, and the thickness of the oxide layer on the extreme surface layer and the rust preventive film is 10 nm or less from the surface, the conductivity is 50% IACS or more, and the liquid crystal polymer is thermally fused. A copper alloy foil for a laminate having excellent adhesion to a liquid crystal polymer, characterized in that the 180 ° peel strength is 5.0 N / cm or more.

  As a copper alloy foil, in Patent Document 4, in a copper alloy containing a specific element, the adhesiveness with an adhesive containing an epoxy resin is good by setting the thickness of the anticorrosive film to 3 nm or less from the surface, The surface roughness is 2 μm or less in terms of 10-point average surface roughness (Rz), and the 180 ° peel strength when bonded to a substrate film with an adhesive containing an epoxy resin without being roughened is 8.0 N / cm. The copper alloy foil for laminated boards which is the above and has high electroconductivity and intensity | strength is disclosed.

Japanese Patent No. 4118832 JP 2005-281757 A Japanese Patent Laid-Open No. 2002-60866 JP 2003-13156 A

  The Cu—Zr alloy plate is disclosed in Patent Documents 1 and 2, and the Cu—Zr alloy foil is a copper alloy foil for laminated plates disclosed in Patent Documents 3 and 4. As the circuit pitch becomes finer, the thickness of the copper alloy foil tends to be as thin as 10 μm, and the demand for a copper alloy foil with less bending strength and excellent bending workability is increasing recently.

  The present applicant has previously filed Japanese Patent Application No. 2009-69923, and contains copper containing 0.005% to 0.5% Zr and 0.001% to 0.3% Co in a weight ratio. An alloy having a lamellar structure in which a plurality of flat crystal grains are continuously stacked in a plane direction and stacked in a plate thickness direction, and the thickness of the crystal grain layer is in a range of 5 nm to 550 nm. And the peak value in the histogram of the thickness of the crystal grain layer in the layered structure exists within a range of 50 nm to 300 nm and with a frequency of 28% or more of the total frequency, and its half width is 180 nm or less. An electronic component copper alloy and a manufacturing method thereof are provided. Thereby, the strength and the elongation can be balanced at a high level, and it is possible to suitably cope with the downsizing and thinning of the electronic component, but there is a demand for a thinner copper alloy foil.

  The present invention has been made in view of such circumstances, and can be used for thinning when laminated with a resin or stainless steel for a copper foil circuit board or when used as a current collector for a lithium ion battery. Provided is a copper alloy foil having excellent bending workability without causing a decrease.

  In general, it is considered effective to refine crystal grains to the nanoscale in order to improve the strength of copper alloys, but it is not possible to improve the elongation simply by miniaturization. As disclosed in Japanese Patent Application No. 2009-69923 filed earlier, the present inventors pay attention to the structure of a longitudinal cross-sectional structure along the rolling direction (RD direction), and fine and flat crystal grains are layered. If the crystal grain layer has a layered structure in which the crystal grain layers are stacked, and the thickness (interval) of the crystal grain layer is uniform and stable as a layered structure in each layer, the strength and elongation are high. Found to balance by level.

  As a result of further research, the inventors have stretched the copper alloy foil described in Japanese Patent Application No. 2009-69923, which has been previously filed, to a copper alloy foil of 100 μm or less by cold rolling. The present inventors have found that the uniformization of the layered structure has further progressed, and as a copper alloy foil, strength and bending workability are ensured at a high level.

That is, the copper alloy foil of the present invention contains Zr in the range of 0.005% to 0.5% and Co in the range of 0.001% to 0.3% by weight, with the balance being Cu and inevitable impurities. A copper alloy having a lamellar structure in which a plurality of flat crystal grains are continuously stacked in a plane direction, and the thickness of the crystal grain layer is 5 nm to The peak value in the histogram of the thickness of the crystal grain layer in the lamellar structure is in a range of 50 nm to 250 nm and at a frequency of 30% or more of the total frequency, and the half width is 120 nm or less. It is characterized by being.

  In this copper alloy foil, the individual thickness of each crystal grain layer in the layered structure is in the range of 5 nm to 500 nm, and in the histogram of the thickness, the peak value exists at a high frequency of 30% or more, and half The value width is as narrow as 120 nm or less, and the histogram curve has a shape with a narrow width and a sharp mountain shape. 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 thinner and more uniform, the strength is higher. When the peak value exceeds 250 nm, sufficient strength as a copper alloy foil 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 within the range of 50 nm to 100 nm. Further, when the frequency of the peak value is less than 30%, the histogram curve becomes gentle and the variation in the thickness of the crystal grain layer becomes large, so that the strength improvement cannot be expected. The same applies to the half width, and if it is 120 nm or more, it cannot contribute to the strength improvement.

  And by using such a stable copper alloy foil with a layered structure, the balance between strength and bending workability is improved at a high level. In general, when copper alloy foil is produced by rolling, bending workability tends to be reduced. However, the copper alloy foil of the present invention is produced only by cold rolling without annealing due to a unique layered structure. It is possible to maintain a balance with strength at a high level without deteriorating bending workability.

  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 content ratio of Zr is set to 0.005% to 0.5% by weight.

  Addition of a small amount of Co has an effect of stabilizing the layered structure evenly and densely, and provides appropriate elongation (ductility). However, if the amount added is less than 0.001% by weight, the layered structure The effect of reducing the thickness variation of each crystal grain layer is poor, and even if it exceeds 0.3%, no further effect can be expected, and conversely, the ductility is remarkably increased and the tensile strength is reduced. Also, there is a problem that the conductivity is lowered. Therefore, the Co content is set to 0.001% to 0.3% by weight.

Furthermore, the copper alloy foil of the present invention has a thickness of 5 to 100 μm, a 0.2% proof stress of 480 N / mm ² or more, and has a flexibility that exceeds 150 times in the MIT flexibility test. It is characterized by.
In this way, strength and bending workability (flexibility) are balanced, so that strength is improved when laminated with resin or stainless steel for circuit boards or when thinned as a current collector for lithium ion batteries. Thus, a copper alloy foil having excellent bending workability (flexibility) is obtained.

  According to the present invention, it is possible to obtain a copper alloy foil that balances strength and bending workability at a high level by the combined effect of addition of Zr, Co and a uniform layered structure by a flat crystal grain layer, It is possible to provide a copper alloy foil that maintains strength and has excellent bending workability when laminated with a resin or stainless steel as a thin circuit board or when used as a current collector for a lithium ion battery.

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 foil of this embodiment (hereinafter simply referred to as a copper alloy foil) contains Zr in a weight ratio in the range of 0.005% to 0.5% and Co in a weight ratio of 0.001%. 1 to 0.3%, and 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. Yes.

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.
Addition of a small amount of Co has an effect of stabilizing the layered structure evenly and imparts an appropriate elongation. However, if the amount added is less than 0.001% by weight, each grain layer of the layered structure The effect of reducing the thickness variation is poor, and even if it exceeds 0.3%, the effect is saturated, and conversely, the conductivity is lowered.

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

  Furthermore, this copper alloy foil contains carbon, oxygen, and one or more elements of chromium, silicon, magnesium, aluminum, iron, titanium, nickel, phosphorus, tin, zinc, calcium, and boron. Any one or two or more of oxides may be selected and contained in the range of 0.0005 or more and 0.005 or less by weight%. It is preferable to appropriately contain these elements in the copper alloy foil because it effectively acts as a starting point of breakage during the press punching process, 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 stacked in the plate thickness direction (ND direction) are layered. 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 in the range of 5 nm to 500 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 250 nm, and the frequency of the peak value P is 30% or more of the total frequency, Further, the half width L is set to 120 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 100 nm or less because the layered structure 3 becomes more uniform.

In addition, the copper alloy foil of the present invention has a thickness of 5 to 100 μm, a tensile strength of 480 N / mm ² or more, and a flexibility that exceeds 150 times in the MIT flexibility test. To do.
Generally, a thickness of 100 μm or less is said to be a copper alloy foil, and in the production of copper foil by normal rolling, the thickness is limited to 5 μm.
This balance of strength and bending workability (flexibility) reduces strength when laminated with resin or stainless steel for circuit boards or when thinned as a current collector for lithium ion batteries. The copper foil has excellent bending workability (flexibility).

Next, a method for producing such a copper alloy foil will be described.
In this manufacturing method, a copper raw material is melted in a refractory furnace, and at least Zr is added to the molten copper in a range of 0.005% to 0.5% and Co in a range of 0.001% to 0.3%. Then, a copper alloy base material was cast. Then, a first step of performing hot rolling including solution treatment on the cast base material, a second step of performing cold rolling thereafter, and subjecting the base material after cold rolling to heat treatment for aging or annealing. Each process of the 4th process which makes the copper alloy foil by cold rolling the copper alloy thin plate manufactured by the 3rd process and the 3rd process is performed one by one.
However, the third step may be carried out as necessary, and in the first and second steps, it is presumed that a copper alloy thin plate that has already been balanced at a high level of strength and elongation has been produced. The third step may be omitted and the process may proceed directly to the fourth step.
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 16% or more, for example, about 19% before the final pass. By making the rolling rate at this stage 16% 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 the final pass of this hot rolling, it processes with a rolling rate of 20% or more. Increasing the rolling rate of this final pass to 20% or more suppresses the growth of crystal grains by heating under high pressure, and imparts 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, the final pass should have a rolling rate of 24% or more, for example, a rolling rate of 40%.
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, the first 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 92%-99.5%, and the base material is reduced to a plate thickness of 0.12 mm-0.75 mm.
By passing through this cold rolling treatment, the thickness of each crystal grain layer in the layered structure becomes uniform, and the peak value becomes large when the distribution of the thickness is made 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 relatively low temperature of the heat treatment, Zr remaining in the crystal grains without being completely precipitated can be converted into Co. Reacts to form a compound. This compound of Zr and Co is assumed to further improve the elongation of the base material, and the copper alloy that has undergone this third step balances the strength and elongation at a higher level.
When the heat treatment of the third step is performed, the effect of improving the strength is poor when the temperature is less than 300 ° C., whereas when 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.

<4th process>
Next, the copper alloy thin plate having undergone the second or third step is subjected to cold rolling a plurality of times to finish a copper foil having a thickness of 100 μm or less. The total rolling rate is preferably 91% to 99%. Since the copper alloy thin plate of the present invention has a uniform and dense layered structure, it is not work hardened by rolling, so that it is not necessary to perform annealing during each cold rolling. By going through this cold rolling process a plurality of times, the thickness of each crystal grain layer in the layered structure becomes small and uniform, and the peak value when the thickness distribution is made a histogram becomes sharp.

Next, examples of the present invention will be described.
A copper alloy to which Zr and Co were added at a ratio shown in Table 1 was cast and manufactured through the processes from the first step to the fourth step. The hot rolling conditions in the first step, the rolling rate during the cold rolling in the second step, the heat treatment conditions in the third step, and the rolling rate during the cold rolling in the fourth step were combined as shown in Table 1.
Samples 1 to 14 were produced in this example, and samples 15 to 28 were produced as comparative examples, in which the addition amount of Zr and Co, hot rolling, cold rolling, and heat treatment were not within the scope of the present invention. The final copper alloy foil has a thickness of 10 μm.

  The obtained copper alloy foil was cut in the rolling direction, and the cross-sectional structure was observed with a TEM. As described above, the thickness direction (ND direction) perpendicular to the rolling direction (RD direction). The distance (interval) between the interfaces of each crystal grain layer was measured along the line, and the distance was defined as the thickness of the crystal grain layer, and 200 pieces were measured. Among the measured values of the thickness of the crystal grain layer, a minimum value, a maximum value, a peak value in the case of a histogram, a frequency thereof, and a half width 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

Next, 0.2% yield strength (YS), bending workability (flexibility), and electrical conductivity were measured for the copper alloy foils of these examples and comparative examples. The results are shown in Table 3.
As for 0.2% proof stress (N / mm ² ), a tensile test was performed in the rolling parallel direction of the sample in accordance with JIS Z2241, and the stress when the strain was 0.2% was measured. The sample was produced according to the above JIS.
For electrical conductivity, the electrical resistance at 20 ° C. was determined by a direct current four-terminal method using a double bridge. The measurement sample was a copper foil having a thickness of 10 μm cut to a width of 12.7 mm. The electrical resistance was determined by measuring the electrical resistance of 50 mm in length between measurements.
Bending workability, that is, bendability, was evaluated by a MIT bendability test. The test conditions were evaluated according to the following criteria by counting the number of reciprocating bending until the fracture.
○: The number of times of bending exceeds 150 times ×: The number of times of bending does not exceed 150 times

From Table 3, it can be seen that the samples of the examples have a 0.2% proof stress and good bending workability, and are well balanced.
Thus, according to the present invention, it is possible to obtain a copper alloy foil that balances strength and bending workability at a high level by the combined effect of addition of Zr and Co and a uniform layered structure by a flat crystal grain layer. It is possible to provide a copper alloy foil that is excellent in bending workability without reducing strength when laminated with resin or stainless steel for thin circuit boards or when used as a current collector for lithium ion batteries. I can do it.

1 Crystal grain 2 Crystal grain layer 3 Layered structure

Claims (2)

0.005% to 0.5% of Zr in weight ratio, of Co contained in the range of 0.001% to 0.3%, the balance being a copper alloy ing of Cu and unavoidable impurities, a plurality of flat A crystal grain layer composed of continuous crystal grains in the plane direction has a layered structure formed by stacking in the plate thickness direction, and the thickness of the crystal grain layer is in the range of 5 nm to 500 nm. The copper alloy foil characterized in that the peak value in the histogram of the thickness of the crystal grain layer is present in a frequency range of 50 nm to 250 nm and at a frequency of 30% or more of the total frequency, and the half width is 120 nm or less. . 2. The thickness according to claim 1, wherein the thickness is 5 to 100 μm, the 0.2% proof stress is 480 N / mm ² or more, and the MIT bendability test has bendability exceeding 150 times. Copper alloy foil.

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