RU2366764C2 - Method of production of copper low-profile foil and low-profile foil produced with implementation of this method - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to hydro-metallurgy and can be implemented at production of copper foil for foiled dielectric and for printed circuit boards. The method consists in solving copper and in producing electrolyte on base of sulphuric acid with contents of chloride ions, and in settling layer of copper on external surface of a rotating drum under effect of electric current, when negative potential is supplied onto the drum, while positive potential is supplied to bent sheets of anodes located in electrolyte; also additives preliminary dissolved in water in form of gelatine, hydroxyethylcellulose and high molecular additive with molecular weight not less, than 600 000 are introduced into electrolyte; notably, gelatine and hydroxyethylcellulose are dissolved in water together, while high molecular additive is dissolved in water separately. Low profiled foil produced by this method contains dull and glossy finish located on opposite sides and possesses uniform columnar structure at average dimensions of crystals 4-7 mcm in cross section, while its dull surface morphology is characterized with presence of pyramid bumps.

EFFECT: upgraded quality of copper foil and complete exclusion of outgrowth occurring on its surface; also improved structure.

8 cl, 11 dwg, 3 tbl

Description

The present invention relates to the field of hydrometallurgy and can be used in the manufacture of copper foil for foil dielectrics for printed circuit boards.

A known method of producing a thin copper electrolytic foil, comprising dissolving copper in sulfuric acid to obtain a certain concentration and the presence of free copper ions in it. After that, this electrolyte is passed between the anode and cathode, and under the influence of electric current, metal ions are deposited on the cathode, which is made rotating. During electrolysis, gelatin and chloride ions are constantly added to the electrolyte in an amount of 0.001-0.005 g / dm and 0.005-0.1 g / dm. The foil obtained using this method is obtained on the one hand smooth, and on the opposite side matte (see Japanese patent 49-31415, according to CL 25/12 for 1982).

The main disadvantage of this method is the high roughness of the matte side of the resulting tape due to the presence of chloride ions that are specifically introduced into the electrolyte. The high roughness (quantitative characteristic of which is Rz) of the “raw” foil increases the true surface of the matte side. In addition, an increase in the roughness of the matte side of the “wet” foil is accompanied by the formation of a thick adhesive layer due to redistribution of the precipitate (preferential deposition on microprotrusions) at the stage of applying the adhesive layer. Obviously, such a foil has a high adhesive force with a dielectric. However, the adhesive layer with an excessively high microrelief concentrated on the peaks of the "raw" foil is unsuitable for the production of thin foil dielectrics used for the manufacture of printed circuit boards. Microprotrusions with an excessive adhesive layer penetrate deep into polymer substrates. This increases the time required to bleed copper. Copper particles tend to remain deeply pressed into the resin. This adversely affects the dielectric properties of the printed circuit board.

Therefore, the problem of increasing the adhesion force should not be solved by increasing the height of the microprotrusion and increasing the adhesive layer, but by reducing the height of the microprotrusion, increasing the number per unit area and more uniform distribution of the adhesive layer. Undoubtedly, this problem is solved at the stage of production of “raw” foil. And this is achieved mainly by selecting surface-active additives, their type and concentration in the electrolyte.

However, one of the factors that negatively affects the structure, and therefore, the topography of the surface of the matte side and the roughness value, is the presence of impurities in the electrolyte.

The source of impurities in the electrolyte is raw materials. Copper granules used as raw materials in the preparation of the electrolyte contain a number of harmful impurities that pass into the electrolyte or precipitation.

Impurities are traditionally divided into four groups.

The first group is electronegative metals: nickel, zinc, iron. They pass into the electrolyte in the form of ions and do not adversely affect the structure and properties of copper foil.

The second group consists of impurities whose potentials are much more electropositive than the potential of copper. These include gold, silver and platinum group metals. They completely fall into the sludge and are removed from the electrolyte on the filters.

The third group - intermetallic and chemical to obtain roughness on the matte surface of the foil. In this method, the structure of the obtained foil is loose and the coating is poorly applied to its surface, because the latter is single-layered in structure.

The fourth group consists of impurities whose potentials are close to the potential of copper: tin, antimony, arsenic. Passing into the solution in the form of ions, they undergo hydrolysis with the formation of insoluble compounds, such as meta-tin acid H ₂ SnO ₃ , arsenic oxide As ₂ O ₃ , and the basic salt of antimony Sb (OH) SO ₄ . All hydrolysis reactions are equilibrium and do not go to the end, and these impurities are distributed between the sludge and the solution. The sludge is filtered off on filters, and the impurities remaining in the electrolyte in the cathode layer of impurities are hydrolyzed to form sols of basic salts, which leads to a sharp deterioration in the quality of the foil.

Also known is a method of producing copper foil by electrolysis of copper from an aqueous solution under the influence of an electric current, by means of which copper is deposited on a rotating drum-cathode, followed by its separation and winding into a roll. After winding the obtained foil into a roll, it is again installed on the coating apparatus and an adhesive coating, for example, galvanizing, is applied to one or both sides (see patent RU No. 2113545, class C25C 1/12 for 1998).

The disadvantage of this method is that at a high current density during electrolysis, controlled by diffusion kinetics, tubercles and cones are formed on the foil surface due to the presence in the cathode layer of sols of the main salts of impurities that adhere to the cathode surface and are embedded in the foil body. In addition, the foil itself does not bond well with the dielectric due to insufficient traction.

A known method for the production of low-profile copper electrolytic foil, including the deposition of a copper layer on the outer surface of a rotating drum under the influence of electric current, the deposition of the foil is from an electrolyte containing copper ions, sulfuric acid and additives in the form of gelatin and hydroxyethyl cellulose and high molecular weight polyacrylamide (cm application US 2003012975, according to CL 25D 1/04 for 2003).

The disadvantage of this method is that on the matte side, despite the low profile obtained by this method, the formation of individual protrusions in the form of cones and growths that cut through the substrate in the manufacture of thin dielectric type laminate.

The technical task of the proposed solution is to eliminate the above disadvantages, improve the quality of the foil, increase the adhesion force of the foil to the dielectric.

This problem is achieved in that in a method for producing a low-profile copper electrolytic foil comprising dissolving copper and producing an electrolyte based on sulfuric acid and depositing a copper layer on the outer surface of a rotating drum under the influence of a negative potential on the drum and curved anode plates that are located inside the electrolyte and have positive potential introduction of additives into the electrolyte in the form of gelatin and chloride ions, gelatin is introduced into the electrolyte in the range of 1-10 mg / dm ³ additional of water soluble polymer is introduced as hydroxyethyl cellulose in the range of 0.1-5 mg / dm ³ and a cationic high-molecular additive activity based on acrylamide and a cationic comonomer with a molecular weight of at least 600,000, as "Praestol 650VS", "Praestol 60VS" within 0 5-5 mg / dm ³ . These additives are introduced into the electrolyte, pre-dissolving them in water, moreover, gelatin and hydroxyethyl cellulose are dissolved in water together, and the high molecular weight additive is dissolved in water separately.

Figure 1 - shows a diagram of an apparatus for implementing the proposed method.

Figure 2 is a cross section of a foil obtained by the proposed method.

Figure 3 is a view A of figure 2.

Figure 4 is an enlarged image of the surface of the foil in a known method.

Figure 5 - adhesive layer on the foil by a known method.

Figure 6 - diagram of the sediment on the foil by a known method.

7 is a view of the formation on the surface of the foil type "cones".

On Fig - the surface of the foil by a known method.

Figure 9 is a diagram of the formation of "cones".

Figure 10 is a view of the surface of the foil obtained by the proposed method.

11 is a view of the surface of the coated foil by the proposed method.

As shown in FIG. 1, the apparatus for producing copper foil is arranged so that the rotating drum 1 and the curved anode plates are located at a certain distance. Drum cathode 1 and anodes 2 are placed in a bath 3 filled with electrolyte 4, which is fed into the space between the anodes and the drum cathode through collector 5. Drum cathode 1 is immersed in electrolyte 4 and rotates about the axis, anodes 2 are immersed in electrolyte 4 so so that the immersed surface of the drum 1 corresponds to the immersed surface of the anode 2. A negative and positive potential are applied to the drum 1 and anodes 2, respectively. Under the influence of electric current, metal ions from the solution are deposited on the surface of the drum-cathode 1 immersed in the electrolyte, forming a precipitate of the required thickness. After separation from the surface of the drum cathode 1, the foil 6 is wound into a roll 7.

The electrolyte 4 filling the bath 3 consists of sulfuric acid 80-150 g / dm ³ , copper ions 80-110 g / dm ³ , chloride ions from 1 to 60 mg / dm ³ . The electrolyte temperature is 50-80 ° C and the current density is 20-100 A / dm ² .

Additives are introduced into the electrolyte to obtain the desired properties of the electrolytic foil 6 in accordance with the method described above. In this invention, an electrolytic foil 6 having excellent electrical characteristics is obtained with the addition of gelatin, hydroxyethyl cellulose and a high molecular weight electrolyte of cationic activity based on acrylamide and a cationic comonomer, for example Praestol 650BC, Praestol 611BC.

These additives are introduced into the electrolyte, previously dissolving them in water. The concentration of gelatin in the solution is from 3 to 10 g / dm ³ , the concentration of hydroxyethyl cellulose is from 1 to 3 g / dm ³ . The solution of Praestol is prepared separately from other additives with a concentration of from 0.5 to 2 g / dm ³ . The amount of an aqueous solution of additives introduced into the electrolyte is dissolved on the basis that the concentration of gelatin in the electrolyte is from 1 to 10 mg / dm ³ , the concentration of hydroxyethyl cellulose in the electrolyte is from 0.1 to 5 mg / dm ³ , and the concentration of Praestol in the electrolyte is from 0.5 to 5 mg / dm ³ .

The electrolytic foil obtained in accordance with this invention and undergoing further traditional processing on the coating apparatus can be used to produce thin foil dielectrics that are used for printed circuit boards.

The low-profile copper electrolytic foil obtained by the claimed method contains a matte and glossy surface located on opposite sides of the foil. A distinctive feature of raw foil is a uniform columnar structure with average crystallite sizes 4–7 μm across, ensuring uniform foil etching in the manufacture of printed outlines, uniform predetermined roughness (Rz from 2.0 to 3.2 μm) and a certain surface morphology characterized by the presence of pyramidal microprotrusions, which guarantees high mechanical strength of the contact at the metal-polymer interface in the manufacture of foil dielectrics and the complete elimination of the build-up Comrade and cones on the matte side.

The presence of traditional processing on the coating apparatus. Traditional processing refers to applying an adhesive layer to one or both sides of a copper foil to increase adhesion of the foil to the dielectric substrate, applying a barrier layer to prevent diffusion of copper into the polymer compound, applying an anti-corrosion coating to prevent oxidation of copper foil and silane to enhance chemical adhesion. A distinctive feature of the foil processed on the apparatus obtained in accordance with this invention is the spherical shape of the adhesive microprotrusions, preventing the deep penetration of the adhesive coating into the dielectric body, providing a high adhesion force of the foil to the dielectric, low roughness (Rz from 4 to 6 μm), which allows the use of foil for the production of thin foil dielectrics.

Variants of foil production in such a way that gelatin, hydroxyethyl cellulose and praestol are added to the electrolyte as an additive at different concentrations are presented below. In accordance with this invention, the composition of the electrolyte:

sulfuric acid 98 g / l, copper 112 g / l, chlorides 40 mg / l;

temperature is about 62 C and current density is about 67 A / dm.

The amount of additives introduced into the electrolyte is shown in Table 1.

Table 1 Gelatin mg / dm ³ Hydroxyethyl cellulose mg / dm ³ Praestol mg / dm ³ Option 1 4.0 2 one Option 2 2.0 one 2 Option 3 6.0 0.2 3

Below are compared samples of foil 1 without the addition of praestol. Samples are compared by properties with foil samples produced in accordance with this invention.

The electrolysis conditions of the foil samples for comparison are the same as for the samples obtained in accordance with this invention. The amount of added additives is shown in table 2.

table 2 Gelatin, mg / dm ³ Hydroxyethyl cellulose, mg / dm ³ Praestol, mg / dm ³ Sample Comparison 1 4.0 2 - Sample Comparison 2 2.0 one - Sample Comparison 3 6.0 0.2 -

FIG. 9, 10 - photo of the samples of "raw" and processed on the apparatus of the coating of the foil obtained in accordance with this invention according to option 1-3, performed on an electron microscope.

Figure 2, 3 and 5, 6 is a photo of the comparison samples 1-2. These photos illustrate the surface appearance of the rough side of the foil, obtained for comparison.

As shown in FIGS. 9 and 10, the surface of the electrolytic copper foil obtained according to embodiments 1-3 in accordance with this invention, in comparison with the reference samples, has a uniform columnar structure with average crystallite sizes across 4-7 μm and a predetermined roughness Rz from 2.0 to 3.2 microns, surface morphology, characterized by the presence of pyramidal microprotrusions.

The foil processed by the coating apparatus obtained in accordance with this invention has a spherical shape of adhesive microprotrusions, and a low roughness Rz of 4 to 6 μm.

Table 3 shows the properties of the foil obtained according to options 1-3 in accordance with this invention and reference samples.

Table 3 Rz crude foil, microns Rz foil processed on the apparatus, microns Temporary tear resistance at 20 ° С, N / mm ² Temporary tear resistance at 180 ° С, N / mm ² Elongation at 20 ° С,% Relative elongation at 180 ° С,% The adhesion force of 18 μm foil with a dielectric, N / 3mm Option 1 2.6 5.5 371 231 13.3 8.9 4,5 Option 2 2,4 5.3 379 225 14.7 9.1 4.6 Option 3 2.7 5,4 378 226 14.1 9.1 4.4 Sample Comparison 1 4.6 7.7 372 229 14.3 9.2 4.3 Sample Comparison 2 4.4 7.8 369 227 13.9 8.8 4.2 Sample Comparison 3 4,5 7.6 377 231 14.5 9.1 4.4

As shown in table 3, the roughness of the electrolytic crude copper foil obtained according to options 1-3 (Rz) is from 2.4 to 2.7 microns, and the roughness of the comparison samples 1 to 3 is from 4.4 to 4.6 microns. The roughness of the electrolytic copper foil processed on the coating apparatus obtained according to options 1-3 (Rz) is from 5.3 to 5.5, and the roughness of the reference samples 1-3 is from 7.6 to 7.8. Conclusion - the electrolytic foil obtained in accordance with options 1-3 in accordance with the conditions of this invention has a roughness lower than the reference samples.

As shown in table 3, the physical properties, temporary tensile strength and relative elongation, both at room temperature and at 180 ° C, are the same for the foil obtained under the conditions of this invention, and for reference samples.

As shown in table 3, the adhesion force of the foil with the dielectric of the foil obtained under the conditions corresponding to this invention is from 4.4 to 4.6 N / 3 mm, while the comparison samples from 4.2 to 4.4 N / 3 mm .

In the production method of low-profile copper foil and copper electrolytic foil produced in this way, the number of additives referenced for each option is not limited to the above. In the present invention can be applied various options for the ratio of additives.

Using the proposed method for the production of copper foil made it possible to obtain a low-profile foil with enhanced properties compared to the known methods for the production of copper foil by electrolysis.

When applying the adhesive layer to one or both sides of the copper foil obtained by the proposed method, the adhesion of the foil to the dielectric substrate increases, the barrier layer prevents the diffusion of copper into the polymer compound, the application of an anti-corrosion coating to prevent oxidation of the copper foil and silane to enhance chemical adhesion. A distinctive feature of the foil coated on the apparatus obtained in accordance with this invention is the spherical shape of the adhesive microprotrusions, which prevents the deep penetration of the adhesive coating into the dielectric body, which provides high foil adhesion to the dielectric, low roughness (Rz from 4 to 6 μm), which allows the use of foil for the production of thin foil dielectrics.

The foil obtained by this method has a homogeneous structure, does not have significant sizes on the surface of tubercles and cones, and a multilayer adhesive coating applied to one or both sides of the foil provides reliable adhesion to both the dielectric and the foil body, which allows its use in all types of electronic boards, including for precision instruments.

Claims (8)

1. A method of manufacturing a low-profile copper electrolytic foil, including dissolving copper and producing an electrolyte based on sulfuric acid and containing chloride ions, depositing a copper layer on the outer surface of the rotating drum under the influence of electric current when a negative potential is applied to the drum, and a positive potential on curved plate anodes located in the electrolyte, while additives in the form of gelatin, hydroxyethyl cellulose and a high molecular weight additive with molecular m assoy at least 600,000, which are previously dissolved in water, moreover, gelatin and hydroxyethyl cellulose are dissolved in water together, and a high molecular weight additive is dissolved in water separately. 2. The method according to claim 1, characterized in that the hydroxyethyl cellulose is introduced into the electrolyte in an amount of 0.1-5 mg / DM ³ . 3. The method according to claim 1, characterized in that Praestol 650BC is used as a high molecular weight additive. 4. Low-profile copper electrolytic foil containing a matte and glossy surface located on its opposite sides, characterized in that it is obtained by the method according to any one of claims 1 to 3 and has a uniform columnar structure with an average crystal size of 4-7 μm across, and the morphology of its matte surface is characterized by the presence of pyramidal protrusions. 5. The low-profile foil according to claim 4, characterized in that the roughness of its matte surface is in the range of 2-3.2 microns. 6. The low-profile foil according to claim 4, characterized in that on its matte surface or matte and glossy surface, a multilayer coating is applied, the layers of which are arranged in the following sequence: adhesive, barrier, anti-corrosion and silane. 7. The low-profile foil according to claim 6, characterized in that there are spherical microprotrusions on the pyramidal protrusions of its matte surface. 8. The low-profile foil according to claim 6, characterized in that the roughness of its matte surface after coating is 4-6 microns.

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