TWI415742B - A method for manufacturing fine grain copper foil with high peel strength and environmental protection for printed circuit board tool - Google Patents

Abstract

The present invention relates to a surface fine-grained copper foil for all types of printed circuit boards providing features of low roughness, high peeling strength, high chemical resistance, high heat resistance, high moisture resistance and good etching and a manufacturing method thereof. The present invention provides a solution for the problems of the conventional electrolytic process technique, which employs a special electrolyte composition and the steps to make the copper nodules not only electrodeposited at peaks, but also effectively deep plated and uniformly deposited at volleys, and the copper nodules so formed have fine sized and are in large quantity. The present invention may satisfy all kinds of characteristic requests for copper under low roughness condition, and provide the surface fine-grained copper foils suitable for all types of printed circuit board. The technique is characterized in that the adhesion surface of the copper foil is subjected to the electroplating bath composed of copper sulfate, sulfuric acid and tungsten composite, and is treated by an electroplating roughening treatment to become a roughening treatment layer; then, on the roughening treatment layer, employing the conventional rust-proof and heat-resistant cooper electroplating method to form a Zn alloy heat resistant layer. The heat resistant layer is electroplated with a basic chromium rust-proof layer, and the rust-proof layer is formed with the silane coupling agent treatment layer thereon. The surface roughening treatment of the copper foil does not use the toxic arsenic element, and may achieve high electroplating efficiency and short processing time, which exhibits the advantages for both environmental protection and high productivity.

Description

Method for manufacturing high-peeling strength and environmentally friendly surface fine-grained copper foil for printed circuit board tool

The present invention relates to a surface fine-grained copper foil suitable for use in printed circuit boards of various specifications and a method of manufacturing the same.

The copper foil applied to the printed circuit board is generally deposited by electroplating copper on the cathode DRUM surface with a copper sulfate electrolyte electrochemical plating method, and then subjected to a post-processing process to become a final finished product. The surface roughening copper foil is formed by hot pressing or rolling a metal sheet, copper or nickel to form a base material for a motor, an electronics industry as a printed circuit board, and a high glass transition temperature (Tg) epoxy substrate. A phenol resin substrate and a polyimide resin substrate are mat-formed into a copper foil-clad laminate, which is used for the production of a printed circuit board.

The basic characteristics required for the copper foil subjected to the surface roughening treatment of the printed circuit board are mainly excellent peeling strength between the copper foil and the substrate of the resin substrate such as various epoxy, phenolic or polyimine. The peel strength must also be maintained above the standard for hot pressing and subsequent processing. Therefore, such a copper foil must have excellent chemical resistance, heat resistance, acid resistance and the like for acids and alkalis, and in the etching process for forming a copper circuit pattern to form a wiring board, it is also required to have excellent burrs caused by residual substances. Etching characteristics. In order to provide the copper foil with various characteristics described above, a roughening treatment for roughening the surface of the copper foil is generally performed, followed by a conventional post-treatment process such as a heat-resistant layer, a rust-preventing layer, and a decane coupling agent layer.

In recent years, with the popularization of notebook computers and mobile phones, the number of epoxy printed circuit boards using high glass transfer temperature (Tg) substrates has been increasing year by year, compared with the conventional FR-4 substrates. The peel strength of copper foil and high Tg substrates is clearly lower. In order to improve the peel strength of the copper foil and the high Tg substrate, the roughness of the rough surface of the copper foil is generally overcome. However, this method of lifting the rough surface is highly prone to the abnormal phenomenon of copper powder (powder falling) and etching residual copper.

On the other hand, due to the increase in density, performance, and miniaturization of the electronic components, the circuit of the printed circuit board is also increased in density, and the line width is also progressing toward miniaturization. Therefore, the copper foil for a printed circuit board must also have a low-thickness characteristic suitable for a high-density and fine-grained wiring. However, the peel strength of the copper foil having such a low-thickness property and the circuit substrate is deteriorated, and the requirements of the various copper foil characteristics described above cannot be achieved, causing a contradiction.

In order to be able to maintain the various characteristics required for the copper foil on the one hand, and to maintain the copper foil on the one hand, the prior art which has been disclosed is that the binary alloy Cu-Ni is excellent in heat-resistant peel strength and hydrochloric acid resistance. However, Japanese Patent Laid-Open No. Sho 52-145769 and Japanese Patent Laid-Open No. 55-058502, which are etched by an alkaline etching solution, and Japanese Patent Laid-Open No. Sho 58-028893 and No. 2-292895 of the Japanese Patent Laid-Open No. CuCl ₂ can also be etched with an alkaline etching solution, but its heat-resistant peel strength and hydrochloric acid resistance are inferior to that of Cu-Ni-based treatment, and Japanese Patent Laid-Open No. 02-292894, No. 02-292894, Japanese Patent Laid-Open No. Hei-- No. 236930 roughening treatment method of metal ion acid copper plating solution containing metal ions containing chromium and tungsten and one or more selected from vanadium, nickel, iron, cobalt, zinc, molybdenum, and Japanese Patent Application No. 11-256389 A roughening treatment method of a metal ion acid plating solution containing one of molybdenum, iron, nickel, and tungsten, and a copper foil roughening treatment which is effective for overcoming heat-resistant peel strength, and is added with arsenic, antimony, bismuth or Acidic copper electrolytic solution such as selenium (Special Gong Zhao 54-38053, special No. Sho 53-39327), which is arsenic, antimony, bismuth and other elements are on the waste water treatment and environmental issues electrolyte added impact. However, the conventional techniques disclosed above can only solve a part of the characteristics of the copper foil, and cannot completely balance the environmental protection and maintain the peel strength, heat resistance, acid resistance, moisture absorption resistance, powder fall and etching characteristics required for the copper foil. .

In view of the above-described deficiencies, an object of the present invention is to provide a copper foil for a printed circuit board having a sufficient adhesion force (strength) between a bonding surface and a synthetic resin substrate, a powder-free phenomenon in etching treatment, and an electrolytic solution for roughening treatment and The waste water after electrolysis also has no copper foil for printed circuit boards.

The inventor, etc., based on years of work experience and research, experiments, and investigations on the topics to be solved, found that the copper foil was pickled with a copper sulfate acid solution to remove dirt or dirt adhering to the surface. When electroplating a copper sulfate plating bath with a trace amount of a tungsten ion compound is applied to the plating, the electrodeposited copper tumor can be deposited not only on the mountain surface of the copper foil formed by the fine granular protrusion group, but also can be effectively deep-plated. The present invention has been completed based on the knowledge that the copper foil is uniformly deposited in the valley position, which affects the characteristics of the copper foil by the roughening treatment of the copper foil by the bonding surface and the synthetic resin.

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems in the prior art, that is, by special electrolytic solution and electrolytic treatment of steps, the copper foil on the adhesive surface of the copper foil is not only electrodeposited on the mountain surface on the contact surface. It can also be effectively plated and evenly deposited in the valley. The copper tumor formed is small in size and large in number, and in particular, in the case of low-thickness, the surface of the copper foil which satisfies the requirements of various copper foil characteristics is suitable for the copper foil of each type of printed circuit board.

In order to attain the above object, the copper foil for a printed circuit board of the present invention is distinguished from the closest prior art technical feature in the roughening treatment step of the surface of the copper foil; 1) the copper foil of the low-thickness surface is first The sulfuric acid solution with copper sulfate is pickled to remove dirt or smear attached to the surface of the copper foil, and 2) an electroplating bath composed of a compound of copper sulfate, sulfuric acid and sodium phosphotungstate is introduced, and a roughening is formed by electroplating. Treating layer; further heat-treating on the roughened layer by conventional techniques to form a heat-resistant layer of Zn alloy; followed by rust prevention on the heat-resistant layer to form an electrolytic alkali chromium anti-rust layer; finally, the rust-proof layer A layer of a decane coupling agent is formed on the layer.

According to the present invention, the electroplating bath composition of the above special plating solution is composed of copper sulfate pentahydrate: 80-90 g/l, sulfuric acid: 90-100 g/l, and a trace amount of sodium phosphotungstate octahydrate (molecular formula: 2Na) ₂ O.P ₂ O ₅ .12WO ₃ .18H ₂ O, soluble in water granular white powder, as a reagent for separating potassium and uric acid): 15~55ppm, with temperature: 20~75°C, current Density: 30~45A/dm ² , plating time: 3~5 seconds and pre-plating.

It should be particularly emphasized that if the concentration of copper sulfate pentahydrate in the acidic washing solution is lower than 245 g/l, the sulfuric acid concentration is also lower than 90 g/l or less; if the concentration of copper sulfate pentahydrate is higher than 265 g/l, The formation of crystal lumps causes the copper foil to be uneven, and the sulfuric acid concentration is higher than 100 g/l or more. If the copper sulfate pentahydrate of the electroplating bath: 80 g/l or less will produce copper powder (powder); if it is 90 g/l or more, the peeling strength will be insufficient. When the sulfuric acid is 90 g/l or less, the plating quality is poorly deteriorated; if it is 100 g/l or more, the etching is poor. Sodium phosphotungstate octahydrate: 15ppm or less, no deep plating effect; 55ppm or more, copper powder (powder) will be produced. Temperature: Below 20 ° C, the peel strength is insufficient; at 75 ° C or more, copper powder (powder) is generated. When the current density is 30 A/dm ² or less, the peel strength is insufficient; when 45 A/dm ² or more, copper powder (powder) is generated. Plating time: 3 seconds or less, the peeling strength is insufficient; 5 seconds or more, copper powder (powder falling) is generated.

In order to avoid thermal discoloration, a conventional method is to perform a Zn alloy heat-resistant layer treatment on a roughened layer as a Zn alloy plating layer such as Zn-Ni, Zn-Co, Zn-Mo or Zn-Ni-Co. The composition of the anti-thermal layer electrolyte is: Zn compound: 1~10g/l, other metal compounds: 0.5~15g/l, pH: 4~10, temperature: 35~60°C, current density: 0.1~4A/ Dm ² , plating time: 3~5 seconds electrolysis.

After the formation of the Zn alloy heat-resistant layer, the alkali chromium is electroplated on the heat-resistant layer to form a rust-preventing layer and a decane coupling agent treatment layer. The anti-rust layer electrolyte is chromic acid concentration: 1~12g/l, liquid alkali concentration: 20~45g/l, temperature: 35~75°C, current density: 0.1~3A/dm ² , electroplating time: 3~ The 5 second condition is carried out to obtain a better effect, and the decane coupling agent treatment layer is prepared by diluting 0.1 to 1.0% by weight of the decane coupling agent with pure water and spraying it on the rustproof layer.

Hereinafter, the present invention will be specifically described by way of preferred embodiments and comparative examples, but the scope of the invention is not limited by the examples.

<Example 1>

Taking a copper foil for electrolysis having a thickness of 30 to 40 μm and a surface roughness Ra of 0.80 μm or less;

(1) 255 g/l of copper sulfate pentahydrate and 95 g/l of sulfuric acid were first subjected to pickling treatment for 5 seconds and then washed with water;

(2) An electroplating bath consisting of 86 g/l of copper sulfate pentahydrate, 95 g/l of sulfuric acid and 26 ppm of sodium phosphotungstate octahydrate, at 25 ° C, was electrolyzed at a current density of 42 A/dm ^{2 for} 3 seconds. The copper foil is bonded to the surface;

(3) After washing with water, electrolyze for 3 seconds at a current density of 32.5 A/dm ^{2 with} an electroplating bath of 300 g/l of copper sulfate pentahydrate, 100 g/l of sulfuric acid and a bath temperature of 60 ° C to form a thick copper composition. Layer,

(4) After washing the copper foil, the same plating solution is used on the roughened layer composed of copper, and electroplating is performed for 3 seconds at a current density of 40 A/dm ^{2 to} form a composite metal layer;

(5) Washing the copper foil on the composite metal layer, and applying the same plating solution as (3), applying a current density of 36 A/dm ^{2 for} 3 seconds to form a complete rough layer (refer to the first figure; The copper tumor shown in the figure is not only electrodeposited on the mountain peak but also effectively plated and uniformly deposited in the valley.)

(6) After washing the copper foil with water, on the roughened layer, a plating bath of zinc sulfate heptahydrate 9 g/l, nickel sulfate hexahydrate 3.5 g/l, pH 9.5 was used, and the current density was 0.5 A/ Dm ^{2 is} subjected to a plating treatment for 5 seconds to form a heat resistant layer;

(7) further washing the copper foil with the heat-resistant layer on the heat-resistant layer, using an electroplating bath of 1.6 g/l of chromic acid and 25 g/l of liquid alkali, and applying electrolysis for 3 seconds at a current density of 1 A/dm ² Forming a rustproof layer;

(8) Finally, the copper foil with the anti-rust layer was washed with water and sprayed on the anti-rust layer with an aqueous solution of 3-glycidoxytrimethylnonane 0.5% by weight, and dried in an oven at 150 ° C for 5 seconds. . The characteristics of the copper foil obtained in the above steps are shown in Table 2.

<Example 2>

Example 1 was repeated, but (2) of Example 1 consisted of copper sulfate pentahydrate 86 g/l, sulfuric acid 95 g/l and sodium phosphotungstate octahydrate 26 ppm in an electroplating bath at a temperature of 25 ° C at a current density of 42 A. The /dm ² electrolysis was performed for 3 seconds, and the copper foil was changed to 26 ppm from the surface of the sodium phosphotungstate octahydrate hydrate to 26 ppm, and the rest was the same as in Example 1. The characteristics of the copper foil obtained in the above steps are shown in Table 2.

<Example 3>

Example 1 was repeated, but (2) of Example 1 consisted of copper sulfate pentahydrate 86 g/l, sulfuric acid 95 g/l and sodium phosphotungstate octahydrate 26 ppm in an electroplating bath at a temperature of 25 ° C at a current density of 42 A. The /dm ² electrolysis was performed for 3 seconds, and the copper foil was changed to 26 ppm by the surface of the sodium phosphotungstate octahydrate hydrate of 26 ppm, and the rest was the same as in Example 1. The characteristics of the copper foil obtained in the above steps are shown in Table 2.

<Example 4>

Example 1 was repeated, but (2) of Example 1 consisted of copper sulfate pentahydrate 86 g/l, sulfuric acid 95 g/l and sodium phosphotungstate octahydrate 26 ppm in an electroplating bath at a temperature of 25 ° C at a current density of 42 A. The /dm ² electrolysis was performed for 3 seconds, and the copper foil was changed to 95 g/l of the sulfuric acid of the surface to 100 g/l, and the rest was the same as in Example 1. The characteristics of the copper foil obtained in the above steps are shown in Table 2.

<Example 5>

Example 1 was repeated, but (2) of Example 1 consisted of copper sulfate pentahydrate 86 g/l, sulfuric acid 95 g/l and sodium phosphotungstate octahydrate 26 ppm in an electroplating bath at a temperature of 25 ° C at a current density of 42 A. The /dm ² electrolysis was performed for 3 seconds, and the copper foil was changed to 95 g/l of the sulfuric acid of the surface and changed to 90 g/l, and the 26 ppm of the sodium phosphotungstate octahydrate was changed to 17 ppm, and the rest was the same as in Example 1. The characteristics of the copper foil obtained in the above steps are shown in Table 2.

<Comparative Example 1>

1) Example 1 was repeated, but (2) of Example 1 consisted of copper sulfate pentahydrate 86 g/l, sulfuric acid 95 g/l and sodium phosphotungstate octahydrate 26 ppm in an electroplating bath at a temperature of 25 ° C. Density 42A/dm ² Electrolytic treatment for 3 seconds The copper foil was changed to 95 g/l of sulfuric acid 95 g/l, and 26 ppm of sodium phosphotungstate octahydrate was changed to 528 ppm of arsenic trioxide. The rest was the same as in Example 1; 2) The copper foil of the above 1) was subjected to electrolytic treatment at a current density of 39.5 A/dm ² for 3 seconds using a plating bath of copper sulfate pentahydrate 255 g/l, sulfuric acid 95 g/l, electroplating bath temperature 55 ° C on the adhesion surface. It forms a roughened layer composed of copper; 3) after washing with water, the same plating solution as 1) is used on the roughened layer composed of copper, and electrolysis is performed for 3 seconds at a current density of 31.5 A/dm ² to form a composite metal. 4) Finally, the copper foil is washed with water and then on the composite metal layer described above, using the same plating solution as 2), and subjected to electrolytic treatment for 3 seconds at a current density of 40.6 A/dm ² to form a complete rough layer ( Please refer to the second figure; the copper tumor shown in the figure is only deposited on the mountain peak without deep plating effect. The characteristics of the copper foil obtained in the above step are shown in Table 2.

<Comparative Example 2>

Comparative Example 1 was repeated, except that in Comparative Example 1, except that 528 ppm of arsenic trioxide was changed to 396 ppm, the same as in Comparative Example 1. The characteristics of the copper foil obtained in the above steps are shown in Table 2.

<Comparative Example 3>

Comparative Example 1 was repeated, except that in Comparative Example 1, except that 528 ppm of arsenic trioxide was changed to 132 ppm, the same as in Comparative Example 1. The characteristics of the copper foil obtained in the above steps are shown in Table 2.

<Comparative Example 4>

Comparative Example 1 was repeated, except that in Comparative Example 1, except that 528 ppm of arsenic trioxide was changed to 66 ppm, the same as in Comparative Example 1. The characteristics of the copper foil obtained in the above steps Shown in Table 2.

The physical property test items used in the embodiments and comparative examples of the present invention are:

1) Peel strength:

A substrate of NP-180 (a halogen resin manufactured by Nanya Corporation) and a non-smooth surface of a copper foil were pressed to form a laminate test piece having a width of 32 mil, and the measurement was performed by a peel strength tensile machine.

2) Heat-resistant peel strength:

After the test piece was baked in an oven at 177 ° C for 240 hours, the peel strength was measured.

3) HCl resistance:

After the test piece was immersed in an 18% HCl solution for 1 hour, the peel strength deterioration rate was measured.

4) Hygroscopicity:

The test piece was placed in a pressure cooker set to a pressure of 1 atm and a temperature of 121 ° C for 2 hours, and the peel strength deterioration rate was measured.

5) Powder:

Press the thick side of the filter paper with the fingertip on the left side of the full width of the non-smooth surface of the copper foil, and slide it from left to right by about 30 cm. The tested filter paper is then compared with the sample card to determine the grade.

<Evaluation criteria for powder level>

○: 0-1 level

△: ≦ 1-2

×: ≦2 level

6) Etchability:

The test piece was made into a line width/line spacing: 75/75 (μm), and placed in an acidic etching solution containing copper chloride 265.9 g/l, hydrogen peroxide 150 ml/l, and HCl 224 ml/l at a temperature of 55 ° C. After immersion for 5 minutes, the film was allowed to stand at 3% NaOH solution at a temperature of 48 °C. After washing with water, a nickel layer was electroplated, and then sliced, and the burr was observed by OM (optical microscope) and SEM (scanning electron microscope).

<Evaluation criteria for etching grade>

○: There was no residual burr phenomenon on the substrate after etching.

△: After etching, there are some residual burrs on the substrate.

×: After etching, there are many residual burrs on the substrate.

[Effects of the Invention]

From Table 2, the peeling strength, heat-resistant peel strength, HCl resistance, moisture absorption resistance and the like of the inventive examples 1 to 5 are all excellent, although the non-smooth surface roughness of the examples 1 to 5 of the present invention is comparatively comparative. 1~4 is low, and the quality characteristics such as powder drop and etching property are also excellent. In contrast, the characteristics of the comparative examples are also inferior to the embodiments of the present invention. For example, the quality characteristics such as peel strength, heat-resistant peel strength, HCl resistance, and moisture absorption resistance of the examples of the present invention are approximately 11.7%, 52.4%, 26.3%, and 11.6% higher than those of the comparative examples.

As described above, the fine-grain surface copper foil produced by the manufacturing method of the embodiment of the present invention has a low roughness of the non-smooth surface, but has high peel strength, high heat-resistant peel strength, and high HCl resistance. High resistance to moisture absorption, powder falling, etching, etc. The quality characteristics are applicable to printed circuit boards of various specifications. The surface roughening treatment also does not use elements such as arsenic, etc.; at the same time, the plating time is short, the efficiency is high, and the advantages of environmental protection and high production speed are combined.

First Fig.: SEM (Scanning Electron Microscope) chart of Example 1 of the present invention.

Second Fig.: SEM (Scanning Electron Microscope) chart of Comparative Example 1 of the present invention.

Claims (5)

A method for producing a high-peel-strength and environmentally-friendly surface fine-grained copper foil of a printed circuit board tool, characterized in that: (1) pickling the surface of the original copper foil with an acid washing liquid consisting of copper sulfate and sulfuric acid To remove dirt or dirt attached to the surface; (2) Inject copper sulfate-containing pentahydrate: 80~90g/l, sulfuric acid: 90~100g/l and trace sodium phosphotungstate octahydrate: 15~55ppm The plating solution is electroplated and roughened; (3) after washing the copper foil, a copper roughening layer is formed on the rough layer by using a plating solution composed of copper sulfate pentahydrate 300 g/l and sulfuric acid 100 g/l; 4) After washing the copper foil, the composite metal layer is electroplated on the copper roughening layer by using the same plating solution as (2); (5) the copper foil is washed with water and reused on the composite metal layer (3) The same plating solution is electroplated to treat the surface fine-grained copper foil. The method for producing a high-peel-strength and environmentally-friendly surface fine-grained copper foil according to the first aspect of the invention, wherein the thickness of the original copper foil is between 30 and 40 μm. The method for producing a high-peel-strength and environmentally-friendly surface fine-grained copper foil according to the first aspect of the invention, wherein the acid washing liquid has a copper sulfate pentahydrate concentration of 245 to 265 g/l, and sulfuric acid. The concentration is 90~100g/l. The method for producing a high-peel-strength and environmentally-friendly surface fine-grained copper foil according to the first aspect of the invention, wherein the roughening treatment is at a plating solution temperature: 20 to 75 ° C, and a current density of 30 ~45A/dm ² , plating time: 3~5 seconds to perform electroplating. The method for producing a high-peel-strength and environmentally-friendly surface fine-grained copper foil according to the first aspect of the invention, wherein the copper roughening layer is at a bath temperature of 60 ° C and a current density of 30 to 45 A/dm. ² is formed by electroplating in 3 to 5 seconds.