JP4017628B2 - Electrolytic copper foil - Google Patents

Description

  The present invention relates to an electrolytic copper foil that can be finely patterned, that is, an electrolytic copper foil that provides a high etching factor.

  Electrolytic copper foil for printed circuits is industrially made of an aqueous solution of copper sulfate, an insoluble electrode such as a titanium electrode coated with lead or a platinum group, and a stainless steel or titanium cathode rotation provided opposite to it. It is manufactured by an electrolytic foil making apparatus that fills the gaps of the drum and energizes these electrodes, deposits copper on the cathode rotating drum, and continuously winds the copper.

  In general, if an aqueous solution containing only copper ions and sulfate ions is used as the electrolyte, pinholes and microporosity will occur in the copper foil due to dust and oils that cannot be avoided in the equipment, which may cause serious practical defects. The shape of the peaks and valleys of the surface (rough surface) on the side of the copper foil in contact with the electrolyte solution collapses, so that sufficient strength cannot be obtained when the copper foil is joined to the insulating substrate material later. If the surface roughness is large, the interlayer insulation resistance and circuit conductivity of the multilayer printed wiring board will decrease, and the residual copper phenomenon on the substrate or the undercut phenomenon of the circuit part will occur during pattern etching after bonding to the substrate material. This causes a problem that various performances of the circuit board are deteriorated.

  In order to prevent such pinholes, chloride ions are added to the electrolytic solution, or dust and oils are removed by passing the electrolytic solution through a filter containing activated carbon or the like. In addition, in order to prevent microporosity and to improve the rough valley shape, glue has been added to the electrolyte for a long time, and it has been proposed to use various organic and inorganic substances as additives in addition to glue. I came. The production technology of electrolytic copper foil for printed wiring boards is based on plating technology, as seen from the point that an electrode is provided in a solution containing a copper salt, and this is energized to deposit copper on the cathode. As an additive for producing an electrolytic copper foil for copper, an additive for copper plating can often be diverted.

  Glue, thiourea, molasses, etc. have long been known as brighteners for copper plating. From this, when these additives are added to the electrolyte, so-called glossy action, regarding electrolytic copper foil for printed wiring boards The expression of the effect of reducing the roughness of the rough surface can be expected, and Patent Document 1 (US Pat. No. 5,171,417) discloses the production of an electrolytic copper foil using active sulfur such as thiourea as an additive. A method is disclosed. However, electrolytic copper foil for printed wiring boards is produced at a higher current density than ordinary plating for the purpose of improving productivity and the performance required for electrolytic copper foil for printed wiring boards in recent years is remarkable. As the demand for copper foil with a low roughness of the rough surface is increased without sacrificing mechanical performance such as elongation, especially in the case of advanced technology, these plating additives are used as they are. Even if it is used as an additive for an electrolytic copper foil for use, satisfactory characteristics cannot be obtained.

  On the other hand, in recent years, the development of electronic circuit technology including semiconductors and integrated circuits has been remarkable, and it is a matter of course that further technological innovation is required in the printed wiring board which is the component forming part or mounting part. . These are the demands for higher multilayer printed circuit boards and fine patterns.

  In order to satisfy these requirements, the performance required of the electrolytic copper foil for printed wiring boards is as follows: the insulating properties between layers and patterns, and the rough surface (precipitated surface; the same shall apply hereinafter) to prevent undercut during etching. There is a need for high tensile strength for profiling (reducing roughness) and improving high-temperature elongation properties for preventing cracks due to thermal stress, and for dimensional stability of printed wiring boards. In particular, there is a strong demand for further low profile for fine patterning.

  For example, as described above, a low profile of the rough surface can be achieved by adding a large amount of glue or thiourea to the electrolyte solution. However, as the amount of addition increases, both the room temperature elongation rate and the high temperature elongation rate increase rapidly. It will drop to. On the other hand, the copper foil obtained from the electrolyte without additives is very high in both normal temperature elongation and high temperature elongation, but the shape of the rough surface is disturbed, the roughness increases, and the high tensile strength. Can not be maintained, and it is impossible to manufacture products with stable performance. When the electrolytic current density is kept low, the roughness of the rough surface becomes lower and the elongation rate and the tensile strength are improved as compared with the electrolytic foil at a high current density, but a decrease in productivity is not economically preferable.

As described above, it is not easy to realize further low profile, good room temperature elongation, high temperature elongation and high tensile strength required for the electrolytic copper foil for printed wiring boards in recent years.
The electrolytic copper foil is usually produced by subjecting an untreated copper foil produced by the above-described electrolytic foil making apparatus to a roughening treatment and an antirust treatment for improving adhesion by a surface treatment device.
The mechanical performance of the electrolytic copper foil produced in this way is determined by the performance of the untreated copper foil 4, and the etching characteristics of the copper foil, that is, the etching rate and the uniform solubility are also greatly affected by the performance of the untreated copper foil. Is determined.

  The factor that has a great influence on the etching property in the performance of the copper foil is the roughness of the surface. The influence of the roughness of the surface that is roughened and bonded to the insulating resin substrate is large. There are two main factors that affect the roughness of copper foil. One is the surface roughness of the untreated copper foil, and the other is how to attach the roughened grainy copper. If the surface roughness of the untreated copper foil that is the original foil is rough, the roughness of the copper foil after the roughening treatment also becomes rough. Moreover, generally, when the adhesion amount of granular copper is large, the roughness of the copper foil after the roughening treatment becomes coarse. The amount of granular copper adhering during the roughening treatment can be adjusted by the current flowing during the treatment, but the surface roughness of the untreated copper foil is the electrolysis conditions when copper is deposited on the drum-shaped cathode, In particular, it depends largely on the additive added to the electrolyte.

  In general, the untreated foil has a relatively smooth surface on the side called the glossy surface, which is in contact with the drum, but the opposite surface is a rough surface. Several attempts have been made in the past to smooth the deposition surface. For example, this is a method for producing an electrolytic copper foil disclosed in the above-mentioned Patent Document 1 using active sulfur such as thiourea as an additive. However, in this case, the precipitation surface is smoothed as compared with the case where conventional additives such as glue are used, but compared with the glossy surface, it is still rough and the effect is not perfect.

  In addition, since the glossy surface is relatively smooth, as disclosed in Patent Document 2 (Japanese Patent Application Laid-Open No. Hei 6-270331), an attempt to adhere granular copper to the glossy surface side and adhere to the resin substrate is also attempted. Has been made. However, in this case, when etching a circuit, a dry film or resist is pasted on the normal rough surface side, but due to the unevenness of the surface, the adhesive force between these dry film or resist and copper foil becomes low and it becomes easy to peel off. There is a drawback.

  US Pat. No. 5,171,417   JP-A-6-270331

The present invention has been made to solve such problems of the prior art, has a high etching factor without reducing the peel strength, and does not leave copper particles at the base of the wiring pattern. The present invention provides a copper foil that can achieve a pattern and has a high high-temperature elongation and a high tensile strength.
Here, the scale of fine patterning is generally determined by the etching factor F from the shape when etched F = 2T / (Wb−Wt)
T can be represented by the thickness of the copper foil, Wb can be represented by the width of the adhesive surface with the substrate, and Wt can be represented by the width of the copper foil surface. The larger this value, the sharper the circuit cross section.

The present invention is an electrolytic copper foil, wherein the surface roughness Rz of the deposition surface of the untreated copper foil is 2.1 μm or less, and is equal to or smaller than the surface roughness Rz of the glossy surface. Features.
Here, the surface roughness Rz means Rz defined in the definition of 5.1 ten-point average roughness (Rz) in JIS B0601-1994 “Definition and display of surface roughness”.
The untreated copper foil can be produced by an electrolytic foil making apparatus using an electrolytic solution to which a compound having a mercapto group and at least one other organic compound and chloride ions are added.

  ADVANTAGE OF THE INVENTION According to this invention, the electrolytic copper foil can be easily implement | achieved low profile formation, and also the elongation rate in normal temperature and high temperature is excellent, and the electrolytic copper foil which has high tensile strength can be obtained.

The present invention is an electrolytic copper foil characterized in that the surface roughness Rz of the deposition surface of the untreated copper foil is 2.1 μm or less and is equal to or smaller than the surface roughness Rz of the glossy surface. is there. The production of such an electrolytic copper foil will be first described.
The base of the additive added to the electrolytic bath for producing the electrolytic copper foil of the present invention is 3-mercapto 1-propanesulfonate. 3-mercapto 1-propanesulfonate is a compound represented by HS (CH ₂ ) ₃ SO ₃ Na or the like. This compound alone is not very effective in refining copper crystals, but by using it in combination with other organic compounds, it is possible to refine copper crystals and obtain a plated surface with less unevenness. Although its detailed mechanism of action is unknown, the molecule reacts with the copper ions in the copper sulfate electrolyte to form a complex, or acts on the plating interface to increase the overvoltage, thereby finening the copper crystals. It is estimated that it is possible to form a plated surface with less unevenness.

The first organic compound to be combined with the 3-mercapto 1-propanesulfonate is a polymeric polysaccharide. High-molecular polysaccharides are carbohydrates such as starch, cellulose, and vegetable gum, and are generally colloidal in water. Industrially inexpensively produced as starch, edible starch, industrial starch, dextrin, and cellulose as water-soluble cellulose ether as disclosed in JP-A-2-182890, that is, sodium carboxymethylcellulose And carboxymethyl hydroxyethyl cellulose ether. Examples of plant rubber include gum arabic and trakand gum.
By combining these organic compounds with 3-mercapto 1-propanesulfonate, it is possible to refine copper crystals and obtain a plated surface without unevenness. In addition to the refinement of crystals, these organic compounds The compound has a function of preventing embrittlement of the produced copper foil. These organic compounds relieve internal stress accumulated in the copper foil, thus preventing not only the phenomenon of tearing and curling of the copper foil when it is wound from the cathode drum, but also improving the room temperature and high temperature elongation. To do.

  Another organic compound according to the combination of electrolytic solutions for producing the untreated copper foil of the present invention is a low molecular weight glue having a molecular weight of 10,000 or less. The low molecular weight glue is obtained by decomposing glue or gelatin that is generally produced by enzyme, acid or alkali to reduce its molecular weight. For example, “PBF” manufactured by Nippi Gelatin Co., Ltd. and “PCRA” manufactured by Peter-Cooper US are commercially available. Their molecular weight is 10,000 or less, and the jelly strength is extremely low due to the low molecular weight.

  Ordinary glue or gelatin has the effect of preventing microporosity, suppressing the roughness of the rough surface, and adjusting the shape, but has the detrimental effect of reducing elongation characteristics. However, using glue that has a lower molecular weight than those marketed as ordinary glue or gelatin has the effect of preventing microporosity and reducing the roughness of the rough surface without sacrificing elongation properties. is there. In addition, when a high molecular weight polysaccharide and a low molecular weight glue are added to 3-mercapto 1-propanesulfonate at the same time, the elongation rate at high temperature is improved and the prevention of microporosity is finer than when each is added alone. It is possible to obtain a uniform uneven surface.

  In addition to the above organic additives, chloride ions are added to the electrolyte. This is because if no chloride ion is present in the electrolytic solution, a copper foil in which the desired rough surface is low profiled cannot be obtained. The effect is obtained at several ppm as the addition amount, but in order to stably produce a low profile copper foil in a wide current density range, it is preferable to keep it in a range of 10 to 60 ppm. Even if the addition amount exceeds 60 ppm, the profile is lowered, but as the addition amount is increased, the effect is not significantly increased. Conversely, if the addition amount is excessive, dendritic electrodeposition occurs or the limit current is increased. This is not preferable because the density decreases.

  As described above, 3-mercapto 1-propanesulfonate and high molecular weight polysaccharides and / or low molecular weight glue and a small amount of chloride ions are added to the electrolytic solution to form low profile copper for fine patterning. It has become possible to realize various characteristics required for foil at a high level. Furthermore, the surface roughness Rz of the deposition surface of the untreated copper foil according to the present invention is the same as or smaller than the surface roughness Rz of the glossy surface of the untreated copper foil. The surface-treated copper foil after the crystallization treatment has a lower profile as compared with the conventional one, and becomes a copper foil having a large etching factor.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

[Examples 1 to 4]
(1) Foil making Copper sulfate-sulfuric acid solution Cu 90g / l of the following composition before adding an additive
H ₂ SO ₄ 110 g / l
Was cleaned through an activated carbon filter. Next, sodium 3-mercapto-1-propanesulfonate, hydroxyethyl cellulose and low molecular weight glue (molecular weight 3,000), and chloride ions were added to the electrolytic solution in the blending ratios shown in Table 1, respectively. A foil-forming electrolyte was prepared. Using the electrolytic solution thus prepared, an untreated copper foil having a thickness of 18 μm was electrolyzed under the electrolysis conditions shown in Table 1 using a noble metal oxide-coated titanium electrode for the anode and a titanium rotating drum for the cathode. Manufactured by foil making.

(2) Evaluation of Roughness and Mechanical Properties Surface roughness Rz and Ra of the untreated copper foils of Examples 1 to 4 obtained in (1) above were measured with a surface roughness meter (SE- manufactured by Kosaka Laboratory). (The surface roughness Rz, Ra is Rz, Ra defined in JIS B 0601-1994 “Definition and display of surface roughness”.) Reference length: 1 Is 2.5 mm when measuring the rough surface and 0.8 m when measuring the glossy surface). Then, the elongation after holding for 5 minutes at a normal temperature in the width direction and at a temperature of 180 ° C., and the tensile strength at each temperature were measured using a tensile tester (Instron type 1122). . The results are shown in Table 2.

[Comparative Examples 1-2]
The surface roughness and mechanical properties of the untreated copper foil obtained by making the foil in the same manner as in the example were evaluated except that the electrolysis was performed under the conditions of the electrolytic solutions and electrolysis conditions of Comparative Examples 1 and 2 shown in Table 1. did. The results are shown together in Table 2.

  In Example 1 to which sodium 3-mercapto-1-propanesulfonate and hydroxyethyl cellulose were added, and Example 2 to which sodium 3-mercapto1-propanesulfonate and low molecular weight glue were added, the roughness of the precipitation surface was sufficiently high. Small and excellent in high temperature elongation characteristics. In Example 3 and Example 4 in which hydroxyethyl cellulose and low molecular weight glue were added to sodium 3-mercapto-1-propanesulfonate, the roughness of the precipitation surface was further reduced as compared with Examples 2 and 3.

  On the other hand, in Comparative Example 1 in which thiourea and normal glue were added, the roughness of the precipitation surface was small compared to the conventional untreated copper foil, but compared to the untreated copper foil of the present invention, Only an untreated copper foil having a rough surface with a larger roughness than a glossy surface can be obtained. Moreover, in the case of this untreated copper foil, the high temperature elongation is small. In Comparative Example 2, as an example of a conventional copper foil, the performance of untreated copper made using normal glue was shown for reference.

  Subsequently, the roughening process was performed to the precipitation surface of the untreated copper foil shown in Examples 1-4 and Comparative Examples 1-2. Further, the untreated foil shown in Comparative Example 2 was further subjected to the same roughening treatment on the glossy surface. The bath composition and conditions for roughening are as follows. After the roughening treatment, a rust-proofing treatment was further performed to produce a surface-treated copper foil. The surface roughness of this copper foil was measured with a surface roughness meter (SE-3C type manufactured by Kosaka Laboratory). The results are shown in Table 3. In Table 3, Examples 1 to 4 and Comparative Examples 1 to 2 were obtained by subjecting the rough surfaces of the untreated copper foils of Examples 1 to 4 and Comparative Examples 1 to 2 in Table 2 to a roughening treatment, respectively. In Comparative Example 3, the glossy surface of the untreated copper foil of Comparative Example 2 in Table 2 was subjected to a roughening treatment.

1. Copper plating conditions for the first layer Bath composition Metallic copper 20 g / l
Sulfuric acid 100g / l
Bath temperature 25 ° C
Current density 30A / dm ²
Processing time 10 seconds

2. Copper plating conditions for the second layer Bath composition Metallic copper 60g / l
Sulfuric acid 100g / l
Bath temperature 60 ° C
Current density 15A / dm ²
Processing time 10 seconds

  The obtained copper foil was heat-sealed to one side of a glass epoxy resin FR-4 substrate to prepare a copper-clad laminate. Furthermore, the etching property was evaluated by the following “evaluation method”.

Evaluation Method The etching characteristics were evaluated by the following method.
After cleaning the surface of each copper clad laminate, a liquid resist was uniformly applied to the surface with a thickness of 5 μm and dried. Next, the test circuit pattern was overlaid on the resist and irradiated with ultraviolet rays at 200 mJ / cm ² using an exposure machine. The test pattern is composed of 10 parallel straight lines with a line width of 100 μm, a line spacing of 100 μm, and a length of 5 cm. Developed immediately after irradiation, washed with water and dried.

Thus, etching property was evaluated with the etching evaluation apparatus with respect to each of the copper clad laminates on which the circuit by the resist was formed. The etching evaluation apparatus is a single nozzle that injects an etching solution from a direction perpendicular to a copper-clad laminate of a sample standing vertically. The etching solution is a mixture of ferric chloride and hydrochloric acid (FeCl ₃ : 2 mol / l, HCl: 0.5 mol / l), liquid temperature 50 ° C., injection pressure 0.16 Mpa, liquid flow rate 1 l / min. The distance between the sample and the nozzle was 15 cm. The injection time was 55 seconds. Immediately after spraying, the substrate was washed with water, and the resist was peeled off with acetone to obtain a printed circuit pattern.

  For each of the obtained printed circuit patterns, the etching factor F when the bottom width was 70 μm was measured. At the same time, the peel strength was also measured. The results are shown in Table 3. It can be judged that the larger the etching factor F value, the better the etching characteristics. Examples 1 to 4 have a much larger etching factor than Comparative Examples 1 to 3.

  In Comparative Examples 1 and 2, since the roughness of the rough surface of the untreated copper foil is larger than that in Examples 1 to 4, the roughness after the roughening treatment is large and the etching factor F is not good. On the other hand, the roughness of the rough surface of the untreated copper foil of Example 2 and the glossy surface of the untreated copper foil of Comparative Example 3 are substantially equal. However, despite the treatment under the same conditions, the surface roughness after the roughening treatment is smaller in Example 2 and larger in Conventional Example 2. In the case of a glossy surface, this is the surface that was in contact with the titanium drum, so the scratches on the drum were transferred as it was, and if roughening treatment was performed on it, the roughened copper particles were likely to become coarser and finally The surface roughness after the roughening treatment is increased. On the other hand, the rough surface of the copper foil according to the present invention is very dense by mirror electrodeposition, so that when roughening treatment is performed on it, the roughened copper grains become finer and finally after roughening treatment It is considered that the surface roughness of the sheet becomes small. This becomes more remarkable in the case of Example 1, Example 3 and Example 4 where the surface roughness of the rough surface of the untreated copper foil is still smaller, the roughness of the roughened surface becomes very small, and the etching factor F Is also getting bigger. Although the roughness of the roughened surface is very small, the peel strength is comparable to that of Comparative Example 3, as a result of the roughening of the roughened copper grains in the roughening treatment, the surface area is increased, Although the roughness is small, it is considered that the peel strength increases. In Comparative Example 3, the roughness of the roughened surface is larger than that of Examples 1 to 4, and therefore, the etching factor F is higher than that of Comparative Examples 1 and 2 to that of Examples 1 to 4. Although it shows a close value, it is inferior to Examples 1 to 4 in terms of the remaining foot during etching.

As described above, according to the present invention, it is possible to easily achieve low profile of the electrolytic copper foil, and it is possible to obtain an electrolytic copper foil having excellent elongation at normal temperature and high temperature and high tensile strength. The electrolytic copper foil thus obtained can be applied to inner and outer layer copper foils for high-density printed wiring boards, and further to electrolytic copper foils for flexible substrates because of improved folding resistance.
In addition, since both sides are flat compared to conventional untreated copper foil, the untreated copper foil obtained by the present invention can be used for secondary battery electrodes, flat cables, electric wire covering shield materials, etc. is there.

The present invention is applicable to a copper-clad laminate using an electrolytic copper foil and a printed wiring board.
In addition, since the untreated copper foil of the present invention is flat on both sides as compared with the prior art, it can be applied to secondary battery electrodes, flat cables, electric wire covering shield materials, and the like.
However, the electrolytic copper foil according to the present invention is not limited to these applications.

Claims (1)

Compounds having a mercapto group, an electrodeposited copper foil electrolytically manufactured foil by the chloride ion, and molecular weight of 10,000 or lower molecular weight glue and electrolytic liquid containing polymeric polysaccharide, the electrolytic copper foil, analysis An electrolytic copper foil, wherein the surface roughness Rz of the exit surface is 2.1 μm or less and is equal to or smaller than the surface roughness Rz of the glossy surface.