JP2006247740A - Copper or copper alloy sheet strip for press forming - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copper or copper alloy sheet strip which can prevent discoloration and corrosion and improve press productivity, by applying an organic compound rust preventive treatment on the copper or copper alloy sheet strip which prevents accumulation of green powder on a wiping pad during the press forming. <P>SOLUTION: The copper or copper alloy sheet strip is coated with the organic compound rust preventive film on its surface, which reacts to the copper and generates carboxylate. The base material, copper or copper alloy sheet strip, is made to have a half-band width of 0.2 μm or more in a histogram obtained by 3-dimensional surface roughness measurement. The variation in size of irregularity on the surface of the copper or copper alloy sheet strip is suppressed and abrasion or wear between the surface of copper or copper alloy sheet strip and the wiping pad is reduced so that the accumulation of the green powder on the wiping pad is prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a copper or copper alloy strip for press working used in the manufacture of pressed products such as semiconductor lead frames, terminals / connectors, relays, and heat sinks. Specifically, it reacts with copper to produce a carboxylate. The present invention relates to the improvement of a copper or copper alloy plate for press working on which an organic compound rust preventive film is formed. In the present invention, a relatively wide plate made of copper or a copper alloy, a relatively narrow strip formed by slitting the plate, and the like are applied, and these are collectively referred to as a strip.

  For the purpose of preventing discoloration and anticorrosion on the surface of copper or a copper alloy sheet, it is widely performed to carry out a rust prevention treatment with a rust preventive mainly composed of benzotriazole (BTA) or a derivative thereof ( Patent References 1 to 5). In addition to this benzotriazole, it is also known to carry out a rust prevention treatment with an amine rust inhibitor, an ester rust inhibitor, or the like (see Patent Document 6).

The benzotriazole or its derivative, or the organic compound rust preventive film such as the amine-based rust preventive agent and ester-based rust preventive agent reacts with copper to form a carboxylate on the surface of the copper alloy. By covering, the anti-rust effect is demonstrated.
JP-A-6-88258 (the whole specification) JP 7-48641 A (the full description) Japanese Patent Laid-Open No. 7-113184 (full description) Japanese Patent Laid-Open No. 9-116066 (full description) JP-A-9-302485 (the whole specification) JP 2003-152155 A (the full description)

  However, the organic compound rust preventive film that reacts with copper on the surface of the copper alloy to produce a carboxylate (hereinafter also simply referred to as organic compound rust preventive film), such as punching of copper or copper alloy strips, etc. Problems are likely to occur during pressing.

  In other words, a phenomenon occurs in which the carboxylate formed by the reaction of the organic compound anticorrosive film with copper adhering to the surface of the copper alloy sheet adheres and accumulates in a powdery manner on the wiping pad on the press entry side. .

  As a result, copper having a carboxylate (attached carboxylate) deposited and deposited in a powdery manner on the wiping pad on the press side peels off from the pad and spills into the press mold. Occurs. The copper having a carboxylate contained in these press dies may cause dents in the press product or, in the worst case, damage the die itself.

  Copper with carboxylate deposited on these pads is green or black, but generally is often green and is commonly referred to as green powder.

  For this reason, in actual operation, the wiping pad is frequently replaced or the mold is cleaned at the time of pressing so that the green powder does not enter the press mold.

  However, these operations are a major factor that reduces the productivity of press working. Note that the wiping pad originally wipes off copper powder, sand or other foreign matter that may have adhered to the surface of the copper or copper alloy sheet to be pressed to prevent foreign matter from entering the press mold. Is to do.

  For this reason, for the problem that green powder accumulates on the wiping pad, on the material side of the copper alloy sheet, conventionally, the focus has been on measures to reduce the amount of green powder mainly composed of copper with carboxylate, Measures have been taken, such as washing away excess rust-proof coatings and controlling the cleanliness of rust-preventive liquids.

  However, although these measures have a slight improvement effect, the green powder has not been greatly reduced until the problem is solved. In addition, since the problem which discolors in the transport period and storage period of a base strip occurs, use of the organic compound rust preventive which reacts with copper on the copper alloy surface and produces | generates a carboxylate cannot be stopped.

  The present invention has been made to solve such a problem, and while performing the organic compound rust prevention treatment for copper or copper alloy sheet, green powder is formed on the wiping pad during press working. The object is to prevent deposition and thereby prevent discoloration and corrosion prevention of copper or copper alloy strips, and at the same time improve press productivity.

  In order to achieve this object, the gist of the copper or copper alloy sheet for press working according to the present invention is the copper or copper alloy on the surface of which an organic compound rust preventive film that reacts with copper to produce a carboxylate is formed. It is a strip, and the half width of the frequency distribution diagram in the three-dimensional surface roughness measurement of the copper or copper alloy strip that is the base material is 0.2 μm or more.

  The reason why the green powder adheres and accumulates on the wiping pad at the time of press working is that the copper having carboxylate attached to the surface of the copper or copper alloy sheet strips. For this reason, in this invention, the unevenness | corrugation of the copper or copper alloy strip which is a base material is controlled. This reduces friction or wear between the wiping pad (wiping cloth) used during the wiping operation of the copper or copper alloy sheet strip and the surface of the copper or copper alloy sheet strip during press working.

  Usually, not only the copper alloy strips but also the surface roughness is often controlled by, for example, increasing the roughness of the metal surface. Also in the conventional copper alloy plate, the surface roughness itself is well defined. For example, in Japanese Patent Application Laid-Open No. 2004-2989, in order to improve press formability, a copper alloy plate for electronic materials is adjusted in the direction perpendicular to the rolling direction by adjusting the roughness of the rolling roll in mechanical polishing or rolling process. It is disclosed that the arithmetic average roughness (Ra) is in the range of 0.07 to 0.13 μm and the maximum height (Ry) is 1.3 μm or less.

  In addition, in JP-A-2004-68067, in order to improve the slidability and durability of the copper-based alloy material, the center line average roughness Ra of the surface of the copper-based alloy material is selected with a selective chemical etching solution. By processing, it is disclosed to make it the range of 0.5-5 micrometers.

  However, conventionally, when the surface roughness of a copper alloy plate is specified, in many cases or commonly known, arithmetic average roughness (Ra) is generally used.

  However, the friction or wear between the surface of the copper or copper alloy strip and the wiping pad, which is a subject of the present invention, and the arithmetic average roughness (Ra) are not so correlated. That is, in the range of the arithmetic average roughness (Ra) of copper or copper alloy strip manufactured by a normal method, the friction or wear between the surface of the copper or copper alloy strip and the wiping pad does not correlate so much. .

  On the other hand, the present inventors have found that the half-value width of the frequency distribution diagram in the three-dimensional surface roughness measurement of copper or a copper alloy sheet is the friction between the surface of the copper or copper alloy sheet and the wiping pad, or It was found to correlate closely with wear.

  Usually, the half width of the frequency distribution diagram in the three-dimensional surface roughness measurement on the surface of a metal material is known as an index of unevenness on the surface. Therefore, the half-value width of the frequency distribution diagram in the three-dimensional surface roughness measurement of copper or copper alloy strip indicates the size of unevenness existing on the surface of copper or copper alloy strip. That is, if the size of the unevenness present on the surface is relatively uniform, the half width is increased. On the other hand, if the variation in the size of the unevenness present on the surface is relatively large, the half width is small.

  If the unevenness of the unevenness present on the surface is relatively large, that is, if the half width is reduced, the friction or wear between the surface of the copper or copper alloy sheet and the wiping pad increases. Then, copper having a carboxylate adhering to the surface of the copper or copper alloy sheet becomes easy to peel off, and the amount of green powder deposited on the wiping pad during press working increases.

  The arithmetic average roughness (Ra) does not correlate so much with the friction or wear between the surface of the copper or copper alloy strip and the wiping pad. The arithmetic average roughness (Ra) It comes from being simply averaged. That is, even if the arithmetic average roughness (Ra) is small or large, it does not correlate with the magnitude of unevenness in the surface of the copper or copper alloy strip.

  The magnitude of the unevenness variation present on the surface of the copper or copper alloy sheet manufactured by a normal method tends to be relatively large depending on, for example, the wear on the surface of the rolling roll or the rolling lubrication state. Therefore, the half width of the copper or copper alloy sheet manufactured by a normal method is likely to be relatively large.

  Therefore, in the present invention, the variation of the unevenness present on the surface of the copper or copper alloy sheet is positively suppressed, the half width is increased, and the surface of the copper or copper alloy sheet and the wiping pad are increased. Reduce friction or wear between the two.

  Thus, while performing the organic compound rust prevention treatment for copper or copper alloy sheet, it is possible to suppress the peeling of copper having carboxylate adhering to the surface of copper or copper alloy sheet, and press working The amount of green powder deposited on the wiping pad can be reduced. As a result, it is possible to prevent discoloration and prevent corrosion of the copper or copper alloy sheet and simultaneously improve press productivity.

(Half width of frequency distribution chart in 3D surface roughness measurement of copper or copper alloy strip)
1 to 4 show frequency distribution diagrams in the three-dimensional surface roughness measurement of copper or copper alloy strips. 1-4, the vertical axis is the normalized number of points (frequency), and the horizontal axis is the surface unevenness height (μm). In the unevenness height of the surface shown on the horizontal axis, with the center 0 at the center, the left unevenness height is negative, the concave (dent depth), and the right unevenness height is positive, the convexity ( The height of each convex portion is shown.

  The full width at half maximum showing the variation in the size of the unevenness present on the surface of the copper or copper alloy strip is the frequency distribution at 0.5 (half value) which is half of the maximum frequency 1.0 on the vertical axis in FIGS. The horizontal width (μm) is shown. FIGS. 1 to 3 show examples of Invention Examples 1, 2, and 3 in the embodiments described later, each having a half width of 0.2 μm or more, and FIG. 4 illustrates an embodiment described later in which the half width is less than 0.2 μm. The example of the comparative example 10 is shown.

  In this invention, as above-mentioned, the dispersion | variation in the magnitude | size of the unevenness | corrugation which exists in the surface of the copper or copper alloy strip which is a base material is suppressed. This reduces friction or wear between the wiping pad (wiping cloth) used during the wiping operation of the copper or copper alloy sheet strip and the surface of the copper or copper alloy sheet strip during press working. For this reason, in this invention, the said half value width of copper or a copper alloy strip surface is enlarged with 0.2 micrometer or more like the invention example in FIGS.

  On the other hand, if the half width is less than 0.2 μm as in Comparative Example 10 in FIG. 4, the half width is too small. For this reason, as described above, the variation in the size of the unevenness present on the surface of the copper or copper alloy sheet increases, and the friction between the wiping pad (wiping cloth) and the copper or copper alloy sheet surface or Wear becomes too great. For this reason, peeling of copper having a carboxylate adhering to the surface of copper or a copper alloy sheet cannot be suppressed, and the amount of green powder deposited on the wiping pad during press working cannot be reduced.

(Cultosis value of roughness curve of copper or copper alloy sheet)
In the present invention, in order to further reduce the variation in the size of the unevenness present on the surface of the copper or copper alloy sheet, in addition to the half width, in the three-dimensional surface roughness measurement of the copper or copper alloy sheet, The kurtosis value (Rku) of the roughness curve is preferably 4.5 or less. The kurtosis value (Rku) of the roughness curve represents the sharpness (roundness) of the irregularities on the surface of the copper or copper alloy sheet, and the smaller the kurtosis value, the more the irregularities become rounded, and the greater the kurtosis value. The unevenness is a sharp curve.

The kurtosis value (Rku) of the roughness curve is known as an index of the degree of unevenness in the three-dimensional surface roughness measurement of a metal material. This kurtosis value (Rku) is expressed by the following formula, and is the unevenness (mountain) height in the Z-axis direction of the three-dimensional surface roughness, and is the height of the mountain Z (x) at the reference length l _r . The following mean square is divided by the square of the following root mean square roughness Rq.
The mean square of the mountain height at the reference length l _r :
{(1 / l _r ) × ∫Z ⁴ (x) dx (where integral is the integrated value from 0 to l _r )}
Root mean square roughness: Rq
Rq: √ {(1 / l _r ) × ∫Z ² (x) dx (where integral is an integrated value from 0 to l _r )}
The kurtosis value of the roughness curve: Rku
Rku = (1 / Rq ⁴ ) × {(1 / l _r ) × ∫Z ⁴ (x) dx (where integral is an integrated value from 0 to l _r )}

As described above, the kurtosis value (Rku) of the roughness curve increases as the sharpness or sharpness of the unevenness on the surface of the copper or copper alloy strip increases. And, as the sharpness and sharpness of the unevenness become steep, the unevenness of the unevenness existing on the surface of the copper or copper alloy strip becomes larger, although not as much as the half width.
Therefore, in addition to the control of the half-value width, if the kurtosis value (Rku) of the roughness curve indicating that the shape of the unevenness is controlled, the size of the unevenness existing on the surface of the copper or copper alloy strip more. Variation can be further suppressed.

(Arithmetic mean roughness)
In the present invention, the arithmetic average roughness (Ra) in the three-dimensional surface roughness measurement cannot be an index for reducing the variation in the size of the unevenness existing on the surface of the copper or copper alloy strip as described above. However, in the present invention, as a premise or as a practical problem, it is not necessary to make the arithmetic average roughness (Ra) of the copper or copper alloy sheet ordinarily produced to be much smaller or even larger (rough). . For this reason, the arithmetic average roughness (Ra) in the three-dimensional surface roughness measurement of the copper or copper alloy strip in the present invention is 0, which is the arithmetic average roughness (Ra) level of the copper or copper alloy strip that is normally produced. 0.07 μm or more.

(Rust prevention film)
In the present invention, the anticorrosive treatment (rust preventive film) on the surface of the copper or copper alloy sheet is an existing benzotriazole (BTA) disclosed in Patent Documents 1 to 6 and the like for the purpose of preventing discoloration and preventing corrosion. A known organic compound rust preventive film that reacts with copper to form a carboxylate on the copper alloy surface, such as a rust preventive mainly composed of the derivative, or the amine rust preventive, ester rust preventive, etc. It can be used as appropriate.

The viscosity of these rust preventives is preferably in the range of 1 to 30 cst (at 40 ° C.) from the viewpoints of preventing discoloration and maintaining the effect of anticorrosion, workability, unplated cap in the lead frame manufacturing process, and the like. Also, the coating amount or adhesion amount of the rust preventive film is 0.01 to 10 mg / m ² from the viewpoint of preventing discoloration and maintaining the anticorrosion effect, and workability and a cap without plating in the lead frame manufacturing process. A range is preferred. In addition, the application method of these rust preventives can select suitably well-known methods, such as electrostatic coating and roller coating.

(Copper or copper alloy sheet material)
As the copper or copper alloy sheet according to the present invention, the existing copper or copper alloy sheet used in the manufacture of press products such as semiconductor lead frames, terminals / connectors, relays, and heat sinks can be used as appropriate. In other words, various copper or copper alloy strips, such as existing copper or copper alloys for lead frames that satisfy the various properties required for these applications, such as conductivity, workability, and strength, can be adapted to the application characteristics. It can be used as appropriate.

  The manufacturing process itself of the copper or copper alloy sheet according to the present invention does not require a special process and can be manufactured by the same process as a normal method. Specifically, a copper alloy molten metal whose components are adjusted to each composition range is cast, the ingot is chamfered, heated or homogenized and then hot-rolled, and the hot-rolled plate is water-cooled. Then, cold rolling, which is said to be a total roll, is performed. The copper alloy sheet after the intermediate rolling is subjected to solution treatment after annealing and cleaning, and after final cold rolling, it is subjected to final annealing or aging treatment as necessary to obtain a copper alloy sheet having a product thickness.

  And these copper alloy plates are subjected to a pretreatment such as degreasing, pickling, water washing, etc., and are rust-prevented with an organic compound rust inhibitor that reacts with copper on the surface of the copper alloy to form a carboxylate, A copper alloy plate (including a coiled coil state) or a slit is formed into a narrow product copper or copper alloy strip (including a coiled coil state).

(Control of the half-value width and kurtosis value of the frequency distribution diagram in the three-dimensional surface roughness measurement of copper or copper alloy sheet)
In addition, the control of the half width and kurtosis value of the copper or copper alloy strip is performed on the rolling conditions including lubrication or the copper or copper alloy strip surface in the rolling step in the manufacturing process of the copper or copper alloy strip. The transfer is performed by precisely (finely) controlling the rolls to be transferred.

  However, as described above, the half width and the kurtosis value of the surface of the copper or copper alloy sheet manufactured by a normal method are likely to be relatively large due to, for example, wear on the surface of the rolling roll or rolling lubrication. For this reason, before the rust prevention treatment step of the copper or copper alloy sheet surface, the half width or kurtosis value of the copper or copper alloy sheet may be controlled by a method such as chemical polishing or mechanical polishing. In some cases, it is necessary to guarantee the half-value width and kurtosis value.

  Examples of the present invention will be described below. By controlling various rolling conditions such as cold rolling rate per one pass at the time of final cold rolling, lubrication conditions, and roll roughness, the above half-value width and kurtosis value of copper or copper alloy strip are controlled. Copper alloy strips having various half widths and kurtosis values were produced. And the effect was evaluated by the amount of green powder deposited on the wiping pad at the time of the above-described press working. These results are shown in Table 1.

  Specifically, CDA19400 alloy used for semiconductor lead frames, copper alloy strips of thickness 0.25 mm × width 30 mm × length 2000 m are washed with an alkaline degreasing solution after the above-described cold-rolling, and then washed with water. Then, it was immersed in an aqueous solution having a BTA concentration of 0.5% at 80 ° C. for about 5 seconds, treated with BTA, and then dried to obtain a test material.

(Surface roughness)
The above half-value width, kurtosis value (Rku), and arithmetic average roughness (Ra) of the surface of these copper alloy strips (test materials) were measured. For these measurements, a Veeco 3D surface shape measuring device WYKO-NT3300 is used, the measurement magnification is set to 50 times, and an area of 120 μm × 91 μm of the test material is measured with a resolution of 163.1 nm. After collecting data at 736 × 480 locations, in order to eliminate sample anisotropy, data was extracted only within an 80 μm × 80 μm square area, and each value was analyzed and determined.

(Evaluation by friction coefficient)
The friction coefficient (μ) on the surface of each copper alloy strip (test material) was measured. The coefficient of friction increases as the half-value width on the surface of the copper alloy strip (test material) decreases and as the kurtosis value (Rku) increases. And this dynamic friction coefficient μ is less than 0.4, suppressing the peeling of copper having carboxylate adhering to the surface of the copper or copper alloy strip, the amount of green powder deposited on the wiping pad during press working It was evaluated that it could be reduced. On the other hand, when the dynamic friction coefficient μ is 0.4 or more, peeling of copper having carboxylate adhering to the surface of the copper or copper alloy strip cannot be suppressed, and the amount of green powder deposited on the wiping pad during pressing is reduced. Evaluated that it was not possible.

For measurement of the coefficient of friction (μ), a surface property measuring instrument HEIDON TYPE: 14DR manufactured by Shinto Kagaku Co., Ltd. was used. A copper indenter (10 × 10 × 50 mm) wrapped with a wiping cloth is placed on the surface of the copper alloy strip so that its longitudinal direction is in the rolling direction of the strip, and a vertical load of 200 g / cm ² is applied to 6000 mm / Pull autograph horizontally in min. The dynamic friction coefficient (μ) was calculated by the following formula A by measuring the tensile force (F) at that time using a load cell.
μ = F / N ------------ Formula A (where N is a vertical load of 200 g / cm ² )

(Evaluation based on the amount of accumulated green powder)
The amount of green powder deposited on the wiping pad was measured by wiping the entire length of the copper alloy strip (test material) while unrolling the obtained copper alloy strip with a surface pressure of 10 g / cm2, and adhering to the wiping cloth. The amount of was observed visually.

  Then, the case where no green powder adheres to the wiping pad was recognized as having no green powder adhering to the wiping pad even during actual pressing, and was evaluated as ◎. In addition, if some green powder adheres to the wiping pad, it can be used to the extent that there is no green powder adhering to the wiping pad, even during actual press processing, by improving the BTA rust prevention film. And evaluated as ○. Furthermore, although the adhesion of green powder was observed on the wiping pad, the case where the amount of adhesion was significantly reduced compared to the conventional case was evaluated as Δ. And the adhesion | attachment of green powder was recognized on the wiping pad whole surface, and the case where the adhesion amount was not reducing compared with the past was evaluated as x which cannot be used for actual press work.

  As is apparent from Table 1, Invention Examples 1 to 9 are comparative examples 10 to 15 in which the half value width of the frequency distribution diagram in the three-dimensional surface roughness measurement is 0.2 μm or more, and the half value width is less than 0.2 μm. Compared to the above, the coefficient of dynamic friction μ is as low as less than 0.4.

  Among the inventive examples, the inventive example in which the kurtosis value (Rku) in the three-dimensional surface roughness measurement satisfies 4.5 or less is higher than the inventive example having a relatively high kurtosis value (Rku). Is low.

  Moreover, arithmetic mean roughness (Ra) has a clear difference and a thing without a clear difference in the comparison with an invention example and a comparative example. For this reason, the critical boundary (boundary) is unclear. Therefore, it turns out that arithmetic average roughness (Ra) cannot be used for evaluation of green powder generation | occurrence | production suppression.

  Therefore, these results support the preferable significance of the half-value width and kurtosis value of the frequency distribution diagram in the three-dimensional surface roughness measurement in the present invention.

  As described above, according to the present invention, a copper or copper alloy strip is subjected to a rust prevention treatment to impart a rust prevention effect (discoloration prevention and corrosion prevention) to the copper or copper alloy strip, and at the same time, punching, etc. The generation of green powder can be suppressed during the pressing process, and the accumulation of green powder on the wiping pad can be prevented. This prevents the green powder from entering the press mold, prevents the formation of dents and damage to the press product, and reduces the need for wiping pad replacement and mold maintenance. Productivity and quality of press products such as lead frames, terminals / connectors, relays, and heat sinks can be improved. Therefore, the copper or copper alloy sheet according to the present invention is optimally applied to these uses.

It is a frequency distribution diagram which shows the half value width by the three-dimensional surface roughness measurement of Example Invention Example 1. It is a frequency distribution diagram which shows the half value width by the three-dimensional surface roughness measurement of Example Invention Example 2. It is a frequency distribution diagram which shows the half value width by the three-dimensional surface roughness measurement of Example Invention Example 7. It is a frequency distribution figure which shows the half value width by the three-dimensional surface roughness measurement of the Example comparative example 10.

Claims (3)

  An organic compound rust preventive film that reacts with copper to form a carboxylate salt is formed on a surface of a copper or copper alloy sheet, in the three-dimensional surface roughness measurement of a copper or copper alloy sheet that is a base material A copper or copper alloy strip for press working, wherein a half width of a frequency distribution diagram is 0.2 μm or more.   The copper or copper alloy sheet for press working according to claim 1, wherein the kurtosis value (Rku) of the roughness curve in the three-dimensional surface roughness measurement of the copper or copper alloy sheet is 4.5 or less. The copper or copper alloy sheet for press working according to claim 1 or 2, wherein an arithmetic average roughness (Ra) in the three-dimensional surface roughness measurement of the copper or copper alloy sheet is 0.07 µm or more.

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