JP5376168B2 - High purity copper anode for electrolytic copper plating, manufacturing method thereof, and electrolytic copper plating method - Google Patents

Abstract

Provided are a highly pure copper anode for electrolytic copper plating, a method for manufacturing the same, and an electrolytic copper plating method using the highly pure copper anode. The highly pure copper anode obtains a crystal grain boundary structure having a special grain boundary ratio L&sgr;N/LN of 0.35 or more. LN is a unit total special grain boundary length. L&sgr;N is a unit total special boundary length. By having the configuration described above, plating defect can be reduced by suppressing the occurrence of the particles, such as the slime or the like, which are generated on the anode side in the plating bath.

Description

  The present invention provides, for example, a high-purity copper anode for electrolytic copper plating that prevents generation of particles such as slime generated on the anode side in the electrolytic copper plating bath during electrolytic copper plating using a copper pyrophosphate bath and a method for producing the same Furthermore, the present invention relates to an electrolytic copper plating method using a high-purity copper anode that can reduce plating defects caused by generation of particles.

Conventionally, high-purity copper is used as an anode electrode for copper plating in electrolytic copper plating in a pyrophosphoric acid bath used for through-hole plating of printed circuit boards.
However, when the anode is melted, slime containing copper powder or metal salt as the main component is generated on the electrode surface, and when it peels off from the anode electrode and flows into the bath, it adheres to the cathode electrode surface and causes plating defects such as protrusions. There was a problem that it was easy to do.

Therefore, in order to solve such problems, for example, as shown in Patent Document 1, a pure copper anode in which the oxygen content contained in the anode is defined and the crystal grain size of the anode electrode is defined is used. Electro copper plating is known.
Also, for example, as shown in Patent Document 2, electrolytic copper plating using pure copper with refined crystal grains as an anode by hot forging-cold working strain removal annealing of a high purity copper ingot is also used. Are known.

Japanese Patent No. 4011336 JP 2001-240949 A

In conventional copper electroplating in a pyrophosphoric acid bath using a copper plating anode, it cannot be said that the generation of slime mainly composed of copper powder and metal salts is sufficient. When precise plating such as plating is required, it cannot be said that the occurrence of defective plating due to generation of particles such as slime is sufficiently suppressed.
Accordingly, in the present invention, a high-purity copper anode for electrolytic copper plating that prevents the generation of particles such as slime generated on the anode side in the electrolytic copper plating bath and the manufacturing method thereof in electrolytic copper plating using a copper pyrophosphate bath Furthermore, an object of the present invention is to provide an electrolytic copper plating method using a high-purity copper anode that can reduce plating defects caused by generation of particles.

The inventors of the present invention conducted extensive research on the relationship between the form of grain boundaries of high-purity copper anode, the generation of anode slime, and plating defects during electrolytic copper plating using a copper pyrophosphate bath. Obtained knowledge.
In conventional copper electroplating using a high purity copper anode using a copper pyrophosphate bath, copper dissolves with the progress of electrolysis, but the dissolution of copper at the anode proceeds non-uniformly. As a result of selective and preferential dissolution of the boundary, it has been found that partial drop of crystal grains occurs, which is a factor in slime generation.

Therefore, the present inventors, in a high-purity copper anode for electrolytic copper plating, so-called so-called special out of the grain boundaries of the crystal grains on the surface of the high-purity copper anode so that dissolution from the anode surface proceeds uniformly. The grain boundary formation rate is increased so that the unit grain boundary length Lσ _{N of the} special grain boundary is equal to or greater than a specific value with respect to the unit grain boundary length L _{N of} all crystal grains (Lσ _N / L _N ≧ 0). .35) When regulated, copper can be uniformly dissolved from the anode surface. As a result, generation of particles such as anode slime is reduced, and plating defects caused by this are greatly reduced. I found out that I could do it.
Here, the special grain boundary is a corresponding grain boundary belonging to 3 ≦ Σ ≦ 29 with a Σ value defined based on “Trans.Met.Soc.AIME, 185,501 (1949)”, and “ Acta.Metallurica.Vol.14, p.1479, (1966) ”, the corresponding corresponding portion lattice orientation defect Dq in the corresponding grain boundary is a grain boundary satisfying Dq ≦ 15 ° / Σ1 / ^2. Is defined as being.

In addition, the present inventors applied a predetermined cold working and hot working to produce a processing strain in producing a high purity copper anode for electrolytic copper plating, and then given a predetermined temperature range (250 to 900 ° C.). By performing the recrystallization heat treatment at, a so-called special grain boundary formation ratio (Lσ _N / L _N ≧ 0.35) among the grain boundaries existing on the surface of the copper anode is high. It has been found that high purity copper anodes can be produced.

  Furthermore, the present inventors use a high-purity copper anode with a high special grain boundary formation ratio (Lσ / L ≧ 0.35). For example, when through-hole plating is performed on a printed circuit board, It has been found that a precise plating layer free from contamination and protrusion defects such as protrusions can be formed on the inner surface.

This invention has been made based on the above findings,
“(1) In high purity copper anode for electroplating,
(A) Using a scanning electron microscope, each crystal grain on the anode surface is irradiated with an electron beam, and the interface between crystal grains having an orientation difference between adjacent crystal grains of 15- or more is used as a grain boundary. The total grain boundary length L of the crystal grain boundary in the range was measured, and the unit total grain boundary length L _N was calculated by converting this per unit area 1 mm ² (b). Similarly, using a scanning electron microscope, The individual crystal grains on the anode surface are irradiated with an electron beam to determine the position of the crystal grain boundary where the interface between adjacent crystal grains constitutes the special grain boundary, and the total special grain boundary length Lσ of the special grain boundary. When this is converted per unit area 1 mm ² and the unit total special grain boundary length Lσ _N is obtained,
(C) The special grain boundary length ratio Lσ _N / L _N between the measured unit grain boundary length L _{N of} the crystal grain boundary and the unit total special grain boundary length Lσ _N of the measured special grain boundary is ,
Lσ _N / L _N ≧ 0.35
A high purity copper anode for electroplating, characterized by having a grain boundary structure satisfying the relationship:
(2) The high purity copper anode for electroplating according to the above (1), wherein the average crystal grain size is 3 to 1000 μm.
(3) After processing high-purity copper for electroplating to give processing strain, a recrystallization heat treatment is performed at 250 to 900 ° C., so that the special grain boundary length ratio Lσ _N / L _N is 0.35 or more. The method for producing a high purity copper anode for electroplating according to the above (1) or (2).
(4) The method for producing a high-purity copper anode for electroplating according to (3), wherein the processing is performed by at least one of cold processing and hot processing.
(5) Repeat cold working and recrystallization heat treatment, or hot working and recrystallization heat treatment, or a combination of these until the special grain boundary length ratio Lσ _N / L _N is 0.35 or more. The manufacturing method of the high purity copper anode for electroplating as described in said (3) or (4) performed.
(6) Hot working is performed at a reduction rate of 5 to 80% in a temperature range of 350 to 900 ° C., and then statically held for 3 to 300 seconds without applying the above-described distortion, and a recrystallization heat treatment is performed. The manufacturing method of the high purity copper anode for electroplating as described in said (3).
(7) Apply cold working at a rolling reduction of 5 to 80%, then heat to a temperature range of 250 to 900 ° C., hold statically for 5 minutes to 5 hours without applying the above processing strain, and recrystallize The manufacturing method of the high-purity copper anode for electroplating as described in said (3) which performs a heat treatment.
(8) An electrolytic copper plating method using the high-purity copper anode for electroplating according to (1) or (2). "
It is characterized by.

  Next, the present invention will be described in detail.

First, the present inventors investigated the progress of dissolution on the surface of a high purity copper anode in electrolytic copper plating, and obtained the following knowledge.
As shown in the schematic diagrams of FIGS. 1A to 1D, in the initial state (a) in which electrolysis is started, a large change does not occur on the anode surface, but a certain period of time has elapsed after the start of electrolysis (b ), Selective dissolution of the crystal grains on the anode surface starts from the grain boundaries that are chemically unstable compared to the inside of the grains, and at the time point (c) when electrolysis proceeds, the grain boundaries are selectively dissolved. As a result, the current density becomes non-uniform due to the shape factor. Therefore, the grain boundary is selectively dissolved at an accelerated rate, and the dissolution of the grain boundary proceeds at the point (d) when the electrolysis proceeds. The undissolved crystal grains are peeled off and peeled off, which causes generation of anode slime, which also causes defective plating. In addition, a new surface is generated in the anode portion where undissolved crystal grains are peeled off and peeled off, voltage fluctuations are generated, and it becomes increasingly difficult to perform stable electrolytic operation.

Based on the above knowledge, the present inventors have further developed a high-purity copper anode for electrolytic copper plating that does not cause selective dissolution (non-uniform dissolution) from grain boundaries with the passage of electrolysis time. As a result of the research, the special grain boundary as defined above in the high-purity copper anode (corresponding grain boundary belonging to 3 ≦ Σ ≦ 29 in Σ value, and the inherent corresponding site lattice orientation defect Dq in the corresponding grain boundary is , Dq ≦ 15 ° / Σ1 / ² ), the total special grain boundary length Lσ _N in the unit area, and the total grain boundary length L _N of the crystal grain boundary in the high purity copper anode. The special grain boundary length ratio Lσ _N / L _N has a grain boundary structure satisfying the relationship of Lσ _N / L _N ≧ 0.35, the crystal structure is stable and chemically Since the proportion of special grain boundaries that are stable increases, As a result, selective dissolution is less likely to occur, and as a result, peeling and exfoliation of undissolved crystal grains are suppressed, generation of anode slime is reduced, and at the same time, generation of plating defects due to slime is also reduced. As a result, the present invention was found.
Here, the unit total crystal grain boundary length L _N is the crystal orientation data obtained from the backscattered electron diffraction pattern obtained by irradiating each crystal grain on the anode surface with an electron beam using a scanning electron microscope. Measure the total grain boundary length L of the grain boundary in the measurement range by dividing the boundary between adjacent crystal grains with an orientation difference of 15 ° or more based on the crystal grain boundary, and divide this by the measurement area and it can be obtained by converting the unit grain boundary length per unit area 1 mm ^2.
When the special grain boundary length ratio Lσ _N / L _N is Lσ _N / L _N <0.35, the selective dissolution of the crystal grain boundary during electrolysis cannot be suppressed, the generation of anode slime is reduced, and the plating defects caused by slime Therefore, the special grain boundary length ratio Lσ _N / L _N was determined to be Lσ _N / L _N ≧ 0.35.

The high purity copper anode of the present invention is Cu having a Cu content of 99.96% by mass or more as defined in Table 2 of JIS / H2123, and in one type of high purity copper, Cu is 99.99% by mass or more. The allowable upper limit of P is 0.0003 mass%, the allowable upper limit of O is 0.001 mass%, and the content of Pb, Zn, Bi, Cd, Hg, S, Se, Te is also a predetermined allowable upper limit. Must be less than or equal to the value. In two types of high-purity copper, Cu is 99.96% by mass or more, and the content of O is suppressed to 0.001% by mass or less.
In addition, the average crystal grain size of the high-purity copper anode of the present invention (twins are also counted as crystal grains) is desirably 3 to 1000 μm, and when the average crystal grain size is out of this range, more anode slime is generated. To do.

The special grain boundary length ratio Lσ _N / L _N between the unit total special grain boundary length Lσ of the special grain boundary and the total grain boundary length L _N of the crystal grain boundary is Lσ _N / L _N ≧ 0.35 A high-purity copper anode having a grain boundary structure satisfying the relationship is subjected to processing (cold processing and / or hot processing) during the production of high-purity copper for electroplating, and after processing strain is applied, 350 to It can be manufactured by performing recrystallization heat treatment at 900 ° C.
As a specific manufacturing example, for example,
(A) After high-temperature processing of high-purity copper for electroplating in a temperature range of 400 to 900 ° C. with a reduction rate of 5 to 80%, it is held statically for 3 to 300 seconds without giving the above processing strain. And a method for producing a high purity copper anode for electroplating having a grain boundary structure satisfying the relationship of Lσ _N / L _N ≧ 0.35 by performing recrystallization heat treatment,
As other production examples,
(B) After cold working at a rolling reduction of 5 to 80%, the steel is heated to a temperature range of 350 to 900 ° C. and statically held for 5 minutes to 5 hours without applying the above-described distortion, and recrystallized. A method for producing a high-purity copper anode for electroplating having a grain boundary structure satisfying a relationship of Lσ _N / L _N ≧ 0.35 by performing a chemical heat treatment,
Can be mentioned.
After straining by hot working or cold working at a specific reduction ratio of (A) and (B) above, recrystallization is performed in a predetermined temperature range without static strain being held statically. Thus, the formation of the special grain boundary is promoted, the ratio of the unit total special grain boundary length Lσ _N can be increased, and the value of the special grain boundary length ratio Lσ _N / L _N can be set to 0.35 or more.
In addition, it is possible to obtain a grain boundary structure satisfying Lσ _N / L _N ≧ 0.35 by repeatedly performing the above hot working, cold working and heat treatment.

The special grain boundary length ratio Lσ _N / L _N between the unit total special grain boundary length Lσ _{N of the} special grain boundary and the total grain boundary length L _N of the crystal grain boundary is Lσ _N / L _N ≧ 0.35 By performing electrolytic copper plating using a high-purity copper anode having a grain boundary structure that satisfies the above relationship as an anode for electroplating, generation of anode slime can be reduced. When copper is plated on the inner surface of the through hole, it is possible to form a precise plating layer free from contamination and plating defects such as protrusions in the through hole.

The grain boundary of high purity copper anode is specified and the total grain boundary length L _N is measured by irradiating each crystal grain on the anode surface with an electron beam using a scanning electron microscope, and the backscattered electrons obtained. Based on the crystal orientation data obtained from the diffraction pattern, the interface between adjacent crystal grains having an orientation difference between adjacent crystal grains of 15 ° or more is defined as the crystal grain boundary, and the total grain boundary length L of the grain boundary in the measurement range Measurement, this is divided by the measurement area and converted to the unit grain boundary length per 1 mm ^{2 of} unit area. The specification of the special grain boundary and the measurement of the unit total special grain boundary length Lσ _N are the same. Using a field emission scanning electron microscope, the individual crystal grains on the anode surface are irradiated with an electron beam to determine the position of the grain boundary where the interface between adjacent crystal grains constitutes the special grain boundary. Measure the total special grain boundary length Lσ of the boundary, and measure this with the measurement area Dividing and converting to a unit grain boundary length per 1 mm ² unit area.
Specifically, an EBSD measuring apparatus using a field emission scanning electron microscope (S4300-SE manufactured by HITACHI, OIM Data Collection manufactured by EDAX / TSL) and analysis software (OIM Data Analysis ver. 5 manufactured by EDAX / TSL). .2), the crystal grain boundary and the special grain boundary are specified, and the length can be calculated.
In addition, the average crystal grain size of the high purity copper anode (twins are also counted as crystal grains) is determined by determining the grain boundaries from the results obtained by the above EBSD measuring device and analysis software. The average crystal grain size (diameter) can be obtained by calculating the number of particles, dividing the area by the number of crystal grains, calculating the crystal grain area, and converting it into a circle.

  According to the high-purity copper anode for electrolytic copper plating of the present invention, its manufacturing method and electrolytic copper plating method, for example, even when a precise plating layer is formed on the inner surface of the through hole of a printed circuit board by electrolytic copper plating, While suppressing the generation of anode slime, it is possible to prevent the occurrence of plating defects such as contamination and protrusions due to slime on the inner surface of the through hole.

(A)-(d) is a schematic diagram which shows the dissolution progress state of the anode surface by electrolysis, (a) is the initial state when electrolysis was started, (b) is the time when electrolysis was started and a fixed time elapsed. In the state where the selective dissolution of the grain boundary has started, (c) shows the result of the selective dissolution of the grain boundary, resulting in non-uniform current density due to the shape factor. (D) shows a state where undissolved crystal grains are peeled off and peeled off due to the dissolution of the grain boundaries. The EBSD analysis result of this invention 3 is shown, a thick line shows a special grain boundary, and a thin line shows a general grain boundary (the same also about FIGS. 3-9). The EBSD analysis result of this invention 5 is shown. The EBSD analysis result of this invention 8 is shown. The EBSD analysis result of this invention 10 is shown. The EBSD analysis result of this invention 13 is shown. The EBSD analysis result of this invention 20 is shown. The EBSD analysis result of the comparative example 1 is shown. The EBSD analysis result of the comparative example 4 is shown.

  Next, the present invention will be specifically described with reference to examples.

Tough pitch pure copper (TPC) having a purity of 99.9% by mass or more, high purity copper (4N OFC) having a purity of 99.99% by mass or more, high purity copper (5N OFC) having a purity of 99.999% by mass or more, purity 99.9999 Hot processing (temperature, processing method, processing rate) and / or cold processing (processing method, processing) on recrystallized or cast material of ultra high purity copper (6N OFC) of mass% or more under the conditions shown in Table 1 Rate), heat treatment (temperature, time), or these were repeated, and after the heat treatment, water-cooled to produce high-purity copper anodes (referred to as the present invention anodes) 1-20 of the present invention having predetermined sizes shown in Table 3. .
The cold wire drawing in Table 1 is the process of drawing a wire sample with a cross-sectional diameter of φ60 mm into a cross-sectional shape of φ30 mm, and the ball molding is a cylindrical sample with a cross-sectional area of φ30 mm cut to a length of 47 mm This is a process of forming a sphere with a diameter of about 40 mm by die forging.
In addition, as an Example in Table 1, when performing hot processing-heat treatment, cold processing-heat treatment, or repeating these as many times as necessary, only repetition under the same conditions is given, but it is not always necessary to repeat under the same conditions. Of course, it is possible to repeat the process under different conditions (processing temperature, processing method, processing rate, holding temperature, holding time) as long as they are within the conditions specified in each claim. It is.

About the anode of the present invention manufactured above, the EBSD measuring device (HITACHI S4300-SE, EDAX / TSL OIM Data Collection) and analysis software (EDAX / TSL OIM Data Analysis ver. 5.2) are used. The crystal grain boundaries and special grain boundaries were specified, and the unit total grain boundary length L _N and the unit total special grain boundary length Lσ _N were determined.
Table 3 shows L _N , Lσ _N and special grain boundary length ratio Lσ _N / L _N.
Table 3 also shows the average crystal grain size values obtained from the results obtained by the EBSD measuring apparatus and analysis software.
2 to 7 show the EBSD analysis results of the anodes 3, 5, 8, 10, 13, and 20 of the present invention, respectively.

For comparison, hot processing (temperature, processing method, processing rate) was performed on the high-purity copper anode material produced above under the conditions shown in Table 2 (at least one condition is outside the scope of the present invention). ), Cold working (working method, working rate), and recrystallization heat treatment (temperature, time) were carried out to produce high purity copper anodes (referred to as comparative example anodes) 1-5 of comparative examples shown in Table 4.
For the comparative anode produced above, the unit total grain boundary length L _N , the unit total special grain boundary length Lσ _N , the special grain boundary length ratio Lσ _N / L _N and the average were also obtained in the same manner as in the present invention. The crystal grain size was determined.
This value is shown in Table 4.
8 and 9 show the EBSD analysis results of Comparative Example Anodes 1 and 4, respectively.

The present invention anodes 1 to 20 and comparative anodes 1 to 5 (both anode surface areas are 400 cm ² ), using a printed circuit board as a cathode, a copper pyrophosphate bath for the through holes of 5 printed circuit boards The copper electroplating using was performed.
Plating solution: Copper pyrophosphate 80 g / L, potassium pyrophosphate 400 g / L, pH 8.5 (pH adjusted with ammonia)
Plating conditions: liquid temperature 50 ° C,
Cathode current density 3 A / dm ² ,
Plating time 20 minutes / sheet,

With respect to the present invention anodes 1 to 20 and comparative example anodes 1 to 5, the amount of anode slime generated from the start of electrolytic copper plating to the completion of electrolytic copper plating on the fifth printed circuit board was measured.
Further, the inner surface of the through-hole of the printed board after plating was observed with an optical microscope, and a protrusion having a height of 3 μm or more formed on the inner surface of the through-hole was regarded as a defect, and the number of protrusion defects was counted.
The measurement results are shown in Tables 5 and 6.

From the results shown in Tables 5 and 6, according to the high purity copper anode for electrolytic copper plating, the method for producing a high purity copper anode for electrolytic copper plating, and the electrolytic copper plating method of the present invention, Even when a copper plating layer is formed on the inner surface of the through hole, generation of anode slime can be suppressed, and the occurrence of plating defects such as contamination and protrusions on the inner surface of the through hole can be prevented.
However, it can be seen that in the comparative example anode in which the special grain boundary length ratio Lσ _N / L _N is less than 0.35, not only the amount of anode slime generated is large, but also plating defects due to slime frequently occur.

  As described above, the present invention has an excellent effect of suppressing the generation of anode slime during electrolytic copper plating and preventing the occurrence of plating defects on the surface of the material to be plated. When applied to the formation of a copper plating layer on the surface, since it is possible to prevent the occurrence of defects such as contamination and protrusions on the inner surface of the through hole of the printed circuit board, the industrial utility is extremely high.

Claims (8)

In high purity copper anode for electroplating,
(A) Using a scanning electron microscope, each crystal grain on the anode surface is irradiated with an electron beam, and the interface between crystal grains having an orientation difference between adjacent crystal grains of 15 ° or more is used as a grain boundary. The total grain boundary length L of the crystal grain boundary in the range was measured, and the unit total grain boundary length L _N was calculated by converting this per unit area 1 mm ² (b). Similarly, using a scanning electron microscope, The individual crystal grains on the anode surface are irradiated with an electron beam to determine the position of the crystal grain boundary where the interface between adjacent crystal grains constitutes the special grain boundary, and the total special grain boundary length Lσ of the special grain boundary. When this is converted per unit area of 1 mm ² and the unit total special grain boundary length Lσ _N is obtained,
(C) The special grain boundary length ratio Lσ _N / L _N between the unit grain boundary length L _{N of} the crystal grain boundary measured and the unit total special grain boundary length Lσ _N of the special grain boundary similarly measured is ,
Lσ _N / L _N ≧ 0.35
A high purity copper anode for electroplating, characterized by having a grain boundary structure satisfying the relationship:   The high-purity copper anode for electroplating according to claim 1, wherein the average crystal grain size is 3 to 1000 µm. After processing high-purity copper for electroplating to give processing strain, a special grain boundary length ratio Lσ _N / L _{N is set} to 0.35 or more by performing recrystallization heat treatment at 250 to 900 ° C. The method for producing a high purity copper anode for electroplating according to claim 1 or 2.   The method for producing a high purity copper anode for electroplating according to claim 3, wherein the processing is performed by at least one of cold processing and hot processing. Claims wherein cold working and recrystallization heat treatment, or hot working and recrystallization heat treatment, or a combination thereof are repeated until the special grain boundary length ratio Lσ _N / L _N is 0.35 or more. 5. A method for producing a high purity copper anode for electroplating according to 3 or 4.   4. A hot working at a rolling reduction of 5 to 80% in a temperature range of 350 to 900 [deg.] C., and then statically holding without applying the processing strain for 3 to 300 seconds, followed by a recrystallization heat treatment. A method for producing a high-purity copper anode for electroplating as described in 1.   Cold-working at a rolling reduction of 5 to 80%, then heating to a temperature range of 250 to 900 ° C., holding statically without giving the above processing strain for 5 minutes to 5 hours, and performing recrystallization heat treatment The manufacturing method of the high purity copper anode for electroplating of Claim 3 to perform.   An electrolytic copper plating method using the high purity copper anode for electroplating according to claim 1 or 2.

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