CN112111731A

CN112111731A - Chemical copper plating solution and preparation method and application thereof

Info

Publication number: CN112111731A
Application number: CN202011320679.4A
Authority: CN
Inventors: 王亚君; 黄亚运; 李晓红; 章晓冬; 刘江波
Original assignee: Suzhou Skychem Ltd
Current assignee: Shanghai Tiancheng Chemical Co ltd
Priority date: 2020-11-23
Filing date: 2020-11-23
Publication date: 2020-12-22
Anticipated expiration: 2040-11-23
Also published as: CN112111731B

Abstract

The invention discloses a chemical copper plating solution and a preparation method and application thereof. The chemical copper plating solution comprises the following components in percentage by mass: 1-10 g/kg of cupric salt, 20-100 g/kg of complexing agent, 0.001-0.02 g/kg of stabilizer, 2-20 g/kg of reducing agent, 0.001-0.05 g/kg of surfactant and the balance of deionized water; and the pH value of the chemical copper plating solution is adjusted to 11-12.5 by adopting a pH regulator. The chemical copper plating solution has high activity, and the thickness of deposited copper in 90s reaches more than 0.3 mu m; the stability is good, and the service life of the bath solution reaches 30 days; the chemical copper plating solution can form a metal copper grid with the line width of 3-5 mu m by a chemical deposition method, the formed metal copper grid has a compact structure, a smooth copper surface and no problems of cracks and broken lines, no copper powder is arranged between the grid and the line, and the copper film has good binding force with a base material and no falling-off phenomenon.

Description

Chemical copper plating solution and preparation method and application thereof

Technical Field

The invention relates to the technical field of copper plating solutions, in particular to a chemical copper plating solution and a preparation method and application thereof.

Background

The ITO thin film is an n-type semiconductor material having high electrical conductivity, high visible light transmittance, high mechanical hardness, and good chemical stability, and is the most commonly used thin film material for transparent electrodes of Liquid Crystal Displays (LCDs), Plasma Displays (PDPs), electroluminescent displays (EL/OLEDs), Touch panels (Touch panels), solar cells, and other electronic instruments.

In the future, products such as mobile terminals, wearable devices, intelligent home appliances and the like have increasingly strong requirements on touch panels, and with the factors of large size and low price of touch panels, and the fact that the conventional ITO film cannot be used for bendable applications, and the essential problems such as conductivity and light transmittance are not easily overcome, many panel manufacturers begin to change the research direction into ITO substitutes, and these ITO substitutes include materials such as nano silver wires, metal grids, carbon nanotubes and graphene.

The early metal grid process is mainly to coat silver bromide on the film, and then to expose and wash silver by yellow light process to obtain the silver metal grid. The traditional one-piece production process of the metal grid is feasible but not beneficial, and recently, manufacturers invest Roll-to-Roll (Roll) process development, so that the economic benefit is high. However, the metal mesh produced by Roll to Roll process has a challenge, that is, the problem of wire breakage can be encountered in the production process, especially in the silver washing stage, if the silver wire is broken, the broken block can not be used, and if the broken position is very dispersed, the yield of the finished product is very low, sometimes only 3. In recent years, the technology of preparing the metal grid by adopting metal materials such as copper and the like is gradually developed, the production cost can be greatly reduced, the theoretical minimum resistance value can reach 0.1 ohm/square inch, and the electromagnetic interference shielding effect is good.

Electroless copper plating is a technique conventionally used in PCB manufacture, and if it can be used in the manufacture of grid lines of a touch screen, the production cost can be greatly saved. However, the electroless copper plating time for PCB production is usually more than 300s, and the copper deposition thickness is between 0.35 and 0.75 μm, so the activity of the electroless copper plating solution is relatively low; the metal grid chemical copper plating for the touch screen adopts a roll-to-roll process, the copper deposition time is only about 90s, and the deposition thickness is required to reach 0.3 micron. Therefore, the conventional electroless copper plating solution cannot meet the preparation process of the metal grid of the touch screen.

CN105296976A discloses an electroless copper plating solution, which comprises a copper pre-plating solution and a thick copper plating solution, wherein the copper pre-plating solution comprises copper salt, formaldehyde, a first complexing agent, a stabilizer, a surfactant, an accelerator and a pH regulator; the thick copper plating solution comprises copper salt, formaldehyde, a second complexing agent, a stabilizing agent, a surfactant, an accelerating agent and a pH regulator; the copper plating solution disclosed by the invention is stable in performance, convenient to maintain, safe and environment-friendly, high in activity of the pre-plating copper solution, good in stability of the thick copper plating solution, high in working efficiency of chemical plating, reliable in combination of the obtained plating layer, high in yield of a copper plated part and beneficial to large-scale industrial production, and the obtained plating layer is reliable.

CN103572268A discloses an electroless copper plating solution, which is an aqueous solution containing copper salt, complexing agent, reducing agent, stabilizer, accelerator and pH regulator; the complexing agent comprises a main complexing agent and an additional complexing agent, wherein the main complexing agent is citrate, and the additional complexing agent is a mixture of triethanolamine and glycerol; the reducing agent is formaldehyde, and the accelerator is benzotriazole. When the chemical copper plating solution provided by the invention is used for chemical copper plating, the copper deposition rate in the chemical copper plating process can be improved, so that a copper plating layer can be obtained quickly and stably, and the quality of the plating layer is good.

Although the complexing agent of the chemical copper plating solution also adopts a combination of a plurality of modes, when the chemical copper plating solution is used for preparing the metal gridding roll-to-roll process of the touch screen, the plating start is slow, the stability is poor, and the prepared metal grid is easy to crack, break, fall off and the like.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide the chemical copper plating solution and the preparation method and the application thereof, the chemical copper plating solution has high activity, and the thickness of deposited copper in 90s reaches more than 0.3 mu m; the stability is good, and the service life of the bath solution reaches 30 days; the chemical copper plating solution can form a metal copper grid with the line width of 3-5 mu m by a chemical deposition method, replaces the traditional ITO, and has the advantages of compact structure of the formed metal copper grid, flat copper surface, no crack and no wire breakage problem, no copper powder between the grid and a circuit, good binding force between a copper film and a base material and no falling-off phenomenon.

One of the purposes of the invention is to provide an electroless copper plating solution, and to achieve the purpose, the invention adopts the following technical scheme:

an electroless copper plating solution comprises the following components in percentage by mass:

1-10 g/kg of cupric salt

20-100 g/kg of complexing agent

0.001-0.02 g/kg stabilizer

2-20 g/kg reducing agent

0.001-0.05 g/kg of surfactant

870-977 g/kg of deionized water;

and the pH value of the chemical copper plating solution is adjusted to 11-12.5 by adopting a pH regulator.

Wherein, the mass concentration g/kg refers to the dosage of each component in 1kg of the chemical copper plating solution, taking the divalent copper salt as an example, the mass concentration of the divalent copper salt is 1-10 g/kg, and the mass of the divalent copper salt in 1kg of the chemical copper plating solution is 1-10 g.

Specifically, the electroless copper plating solution comprises the following components in percentage by mass:

1 to 10g/kg of a divalent copper salt, for example, the mass concentration of the divalent copper salt is 1g/kg, 2g/kg, 3g/kg, 4g/kg, 5g/kg, 6g/kg, 7g/kg, 8g/kg, 9g/kg or 10g/kg, etc., and the divalent copper salt is preferably copper sulfate pentahydrate.

20-100 g/kg of complexing agent, for example, the mass concentration of the complexing agent is 20g/kg, 30g/kg, 40g/kg, 50g/kg, 60g/kg, 70g/kg, 80g/kg, 90g/kg or 100 g/kg.

0.001 to 0.02g/kg of a stabilizer, for example, the mass concentration of the stabilizer is 0.001g/kg, 0.002g/kg, 0.003g/kg, 0.004g/kg, 0.005g/kg, 0.006g/kg, 0.007g/kg, 0.008g/kg, 0.009g/kg, 0.01g/kg, 0.011g/kg, 0.012g/kg, 0.013g/kg, 0.014g/kg, 0.015g/kg, 0.016g/kg, 0.017g/kg, 0.018g/kg, 0.019g/kg or 0.02 g/kg.

The reducing agent is 2-20 g/kg, for example, the mass concentration of the reducing agent is 2g/kg, 3g/kg, 4g/kg, 5g/kg, 6g/kg, 7g/kg, 8g/kg, 9g/kg, 10g/kg, 11g/kg, 12g/kg, 13g/kg, 14g/kg, 15g/kg, 16g/kg, 17g/kg, 18g/kg, 19g/kg or 20 g/kg.

0.001 to 0.05g/kg of a surfactant, for example, the surfactant has a mass concentration of 0.001g/kg, 0.005g/kg, 0.01g/kg, 0.015g/kg, 0.02g/kg, 0.025g/kg, 0.03g/kg, 0.035g/kg, 0.04g/kg, 0.045g/kg or 0.05 g/kg.

The balance of deionized water.

The chemical copper plating solution is adjusted to pH 11-12.5 by using a pH regulator, for example, the pH is adjusted to 11, 11.5, 12 or 12.5.

The complexing agent comprises a first complexing agent and a second complexing agent, wherein the mass ratio of the first complexing agent to the second complexing agent is (2:1) - (15:1), for example, the mass ratio is 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1 or 15:1, and the like.

The first complexing agent is any one or a mixture of at least two of tartaric acid and tartrate;

the second complexing agent is any one or a mixture of at least two of tetrahydroxypropyl ethylenediamine, ethylene diamine tetraacetic acid salt, N-hydroxyethyl ethylene diamine triacetic acid and N-hydroxyethyl ethylene diamine triacetic acid salt.

The stabilizer comprises a first stabilizer and a second stabilizer, wherein the mass ratio of the first stabilizer to the second stabilizer is (1:1) - (20:1), for example, the mass ratio is 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1 or 20: 1.

The first stabilizer is any one or a mixture of at least two of potassium ferrocyanide, potassium nickel cyanide, potassium cyanide and sodium cyanide;

the second stabilizer is any one or a mixture of at least two of thiourea, 2-mercaptobenzothiazole and mercaptosuccinic acid.

The reducing agent is formaldehyde.

The surfactant is any one or a mixture of at least two of polyethylene glycol-600, polyethylene glycol-800, polyethylene glycol-1000, nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether and EO-PO block copolymer.

The pH regulator is sodium hydroxide or potassium hydroxide.

According to the chemical copper plating solution, the complexing agent adopts the synergistic effect of the first complexing agent and the second complexing agent, the stabilizer adopts the synergistic effect of the first stabilizer and the second stabilizer, and the dosage of each component and the pH value of the whole chemical copper plating solution are adjusted, so that the chemical copper plating solution is high in activity, and the thickness of deposited copper in 90s reaches more than 0.3 mu m; the stability is good, and the service life of the bath solution reaches 30 days; the chemical copper plating solution can form a metal copper grid with the line width of 3-5 mu m by a chemical deposition method, replaces the traditional ITO, has compact structure of the formed metal copper grid, smooth copper surface and no problems of cracks and broken lines, does not contain copper powder between the grid and the line, has good binding force between a copper film and a base material and no falling-off phenomenon, and is particularly suitable for metallization of the grid of the touch screen.

The second purpose of the invention is to provide a preparation method of the electroless copper plating solution, which comprises the following steps:

respectively measuring various required raw materials and deionized water, specifically according to the amount of prepared chemical copper plating solution, dissolving 20-100 g of complexing agent by using deionized water according to the total mass of 1kg of the chemical copper plating solution, adding 1-10 g of cupric salt while stirring, adjusting the pH to 11-12.5 by using a pH regulator after dissolving, adding 0.001-0.02 g of stabilizer and 0.001-0.05 g of surfactant, and uniformly stirring; and finally, adding 2-20 g of reducing agent and uniformly stirring to obtain the electroless copper plating solution.

In the alkaline environment, copper ions may initially form precipitates, but later dissolve and exist in a complex ion state for completing the subsequent copper plating process. During production, the required raw materials can be concentrated and prefabricated according to a certain proportion according to actual requirements, and generally 4 concentrated products are prepared firstly: copper salt, complexing agent containing certain pH regulator, reducing agent and stabilizer containing surfactant.

The invention also aims to provide application of the electroless copper plating solution, which is used for metallization of the grids of the touch screen.

Generally, the conventional electroless copper plating solution has poor stability when the activity is high, and the film forming quality with high activity is poor, compared with the conventional electroless copper plating solution, when the electroless copper plating solution is used for touch screen grid metallization, the dual requirements of the activity and the stability can be considered, and meanwhile, the film forming quality is good, and the structure is compact.

Compared with the prior art, the invention has the beneficial effects that:

the chemical copper plating solution has high activity, and the thickness of deposited copper in 90s reaches more than 0.3 mu m; good stability, and the service life of the bath solution reaches 30 days.

The chemical copper plating solution can form a metal copper grid with the line width of 3-5 mu m by a chemical deposition method, and replaces the traditional ITO; the formed metal copper grid structure is compact, the copper surface is smooth, and the problems of cracks and broken lines are avoided; copper powder is not arranged between the grids and the lines; the copper film has good binding force with the base material and has no shedding phenomenon.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments.

Unless otherwise specified, various starting materials of the present invention are commercially available or prepared according to conventional methods in the art.

Example 1

The electroless copper plating solution of the embodiment comprises the following components in percentage by mass:

copper sulfate pentahydrate 2g/kg

20g/kg of potassium sodium tartrate

Tetrahydroxypropyl ethylenediamine 5g/kg

Sodium cyanide 0.01g/kg

0.001g/kg of thiourea

Formaldehyde 10g/kg

Polyethylene glycol-8000.005 g/kg

962.894g/kg of deionized water;

and the pH value of the chemical copper plating solution is adjusted to 11 by adopting sodium hydroxide.

The preparation method of the electroless copper plating solution of the embodiment comprises the following steps: dissolving a complexing agent in deionized water according to the proportion, adding a cupric salt while stirring, adjusting the pH to 11 by using a pH regulator after dissolving, adding a stabilizer and a surfactant, and uniformly stirring; finally, adding a reducing agent and stirring uniformly to obtain the chemical copper plating solution.

Example 2

copper sulfate pentahydrate 5g/kg

50g/kg of potassium sodium tartrate

Tetrahydroxypropyl ethylenediamine 15g/kg

Potassium ferrocyanide 0.005g/kg

2-mercaptobenzothiazole 0.001g/kg

Formaldehyde 20g/kg

Nonylphenol polyoxyethylene ether 0.005g/kg

909.989g/kg of deionized water;

and the pH value of the chemical copper plating solution is adjusted to 11.5 by adopting sodium hydroxide.

The electroless copper plating solution of this example was prepared in the same manner as in example 1.

Example 3

copper sulfate pentahydrate 10g/kg

80g/kg of potassium sodium tartrate

Tetrahydroxypropyl ethylenediamine 8g/kg

Potassium nickel cyanide 0.015g/kg

Thiourea 0.0002g/kg

Mercaptosuccinic acid 0.01g/kg

Formaldehyde 2g/kg

EO-PO block copolymer Pluronic F680.02g/kg

899.95g/kg of deionized water;

and the pH value of the chemical copper plating solution is adjusted to 12 by adopting sodium hydroxide.

Example 4

This example differs from example 1 in that the complexing agent was potassium sodium tartrate in an amount of 25g/kg, and is otherwise the same as example 1.

Example 5

This example differs from example 1 in that the mass ratio of potassium sodium tartrate to tetrahydroxypropylethylenediamine was too high, specifically 20:1, and the rest was the same as example 1.

Example 6

This example differs from example 1 in that the mass ratio of potassium sodium tartrate to tetrahydroxypropylethylenediamine was too low, specifically 1:1, and the rest was the same as in example 1.

Example 7

This example differs from example 1 in that the stabilizer is NaCN, used in an amount of 0.011g/kg, which is the same as that used in example 1, and the other is the same as that used in example 1.

Example 8

This example differs from example 1 in that the stabilizers were bipyridine 0.001g/kg and thiourea 0.01g/kg, and the others were the same as in example 1.

Example 9

This example differs from example 1 in that the mass ratio of NaCN to thiourea was too high, specifically 40:1, and the rest was the same as example 1.

Example 10

This example differs from example 1 in that the mass ratio of NaCN to thiourea was too low, specifically 0.5:1, and is otherwise the same as example 1.

Example 11

This example differs from example 1 in that the surfactant was replaced with sodium dodecylbenzenesulfonate, and the rest was the same as example 1.

Example 12

This example differs from example 1 in that the reducing agent was replaced with sodium hypophosphite, all other things being equal to example 1.

Comparative example 1

The comparative example is different from example 1 in that the electroless copper plating solution was adjusted to pH 10 with sodium hydroxide, and the rest was the same as example 1.

Comparative example 2

This comparative example is different from example 1 in that the electroless copper plating solution was adjusted to pH 13 with sodium hydroxide, and the rest was the same as example 1.

Comparative example 3

This comparative example differs from example 1 in that it does not contain a surfactant, and is otherwise the same as example 1.

Comparative example 4

This comparative example differs from example 1 in that the complexing agent is used in too large an amount, specifically 100g/kg of sodium potassium tartrate and 20g/kg of tetrahydroxypropylethylenediamine, and the rest is the same as in example 1.

Comparative example 5

This comparative example differs from example 1 in that the amount of complexing agent used was too small, specifically 10g/kg of sodium potassium tartrate and 1g/kg of tetrahydroxypropylethylenediamine, and the rest was the same as in example 1.

Comparative example 6

This comparative example differs from example 1 in that the amount of stabilizer used was too large, specifically 0.05g/kg NaCN and 0.002g/kg thiourea, and the other examples were the same as example 1.

Comparative example 7

This comparative example differs from example 1 in that the amount of stabilizer used was too small, specifically 0.002g/kg NaCN and 0.001g/kg thiourea, and the other examples were the same as example 1.

Comparative example 8

This comparative example differs from example 1 in that the amount of surfactant used was too much, specifically polyethylene glycol-8000.1 g/kg, and the rest was the same as in example 1.

Comparative example 9

This comparative example differs from example 1 in that the amount of surfactant used is too small, specifically polyethylene glycol-8000.0005 g/kg, and is otherwise the same as example 1.

The electroless copper plating solutions prepared in examples 1 to 12 and comparative examples 1 to 9 were subjected to performance tests, and the results of the tests are shown in Table 1. Wherein the relevant performance test comprises:

(1) whether the appearance of the copper grid line (observed by a metallographic microscope) has the problems of cracks, falling off and broken lines or not;

(2) the bonding force of the metallic copper film to the substrate (3M 610 tape test);

(3) stability of electroless copper plating solution: the beaker is placed for 48h to observe the copper bonding condition.

As can be seen from Table 1, the electroless copper plating solutions of examples 1 to 3 of the present invention have high activity and good stability; the formed metal copper grid line has no crack, complete copper feeding and no broken line; the copper film has good bonding force with the base material, and does not fall off in 610 adhesive tape test. Example 4 the complexing agent was only one potassium sodium tartrate and resulted in cracking of the grid lines, poor adhesion of the copper film to the substrate and delamination as measured by 610 tape test.

Example 5 a too high mass ratio of the two complexing agents resulted in cracking of the grid lines, poor bonding of the copper film to the substrate, and delamination as measured by 610 tape test.

Example 6 too low a mass ratio of the two complexing agents resulted in a less active electroless copper plating solution, slow start-up and localized absence of copper in the grid lines reacting for 90 s.

Example 7 the stabilizer used only one kind of sodium cyanide, which resulted in poor stability of the electroless copper plating solution, and copper deposition was observed after 24 hours of storage.

Example 8 replacement of the stabilizer with another type resulted in cracking of the grid lines, poor adhesion, and easy detachment of the copper film.

Example 9 too high a mass ratio of the two stabilizers resulted in poor stability of the electroless copper plating solution, and copper precipitates were observed after standing for 24 hours.

Example 10 too low mass ratio of the two stabilizers results in poor activity of electroless copper plating solution, low copper deposition rate and local cracks in grid lines.

Example 11 replacement of the surfactant with sodium dodecylbenzenesulfonate causes problems of cracking and breaking of the grid lines, and the copper film has poor binding force with the substrate and is easy to fall off.

Example 12 replacement of the reducing agent with sodium hypophosphite resulted in poor electroless copper plating bath activity and large areas of 90s grid lines without copper.

Comparative example 1 too low pH of the electroless copper plating solution causes poor activity of the electroless copper plating solution, partial grid lines are not coated with copper within 90s, and the copper film has poor binding force with the substrate and is easy to fall off.

Comparative example 2 too high pH of the electroless copper plating solution resulted in poor stability of the electroless copper plating solution and cracks and breaks in the grid lines.

Comparative example 3, which contains no surfactant, causes cracks and breaks in the grid lines.

Comparative example 4 too much complexing agent was used, which resulted in poor stability of electroless copper plating solutions and no copper on the grid lines in 90 s.

Comparative example 5 too little complexing agent will cause grid lines to crack and break, and the copper film will have poor binding force with the substrate and will easily fall off.

Comparative example 6 too much stabilizer was used, which resulted in poor stability of electroless copper plating solution and no copper on the part of grid lines within 90 s.

Comparative example 7 too little stabilizer will cause the grid line to crack, break, and the copper film will have poor bonding force with the substrate and will easily fall off.

Comparative example 8 too much surfactant was used, resulting in poor stability of electroless copper plating solution and no copper on the part of grid lines within 90 s.

Comparative example 9 the amount of the surfactant was too small, the grid line had cracks and broken lines, the bonding force between the copper film and the substrate was poor, and the film was liable to fall off.

The present invention is illustrated by the above-mentioned examples, but the present invention is not limited to the above-mentioned detailed process equipment and process flow, i.e. it is not meant to imply that the present invention must rely on the above-mentioned detailed process equipment and process flow to be practiced. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. The electroless copper plating solution is characterized by comprising the following components in percentage by mass:

1-10 g/kg of cupric salt

20-100 g/kg of complexing agent

0.001-0.02 g/kg stabilizer

2-20 g/kg reducing agent

0.001-0.05 g/kg of surfactant

The balance of deionized water;

adjusting the pH value of the chemical copper plating solution to 11-11.5 by using a pH regulator;

the complexing agent comprises a first complexing agent and a second complexing agent, and the mass ratio of the first complexing agent to the second complexing agent is (2:1) - (15: 1);

the second complexing agent is any one or a mixture of at least two of tetrahydroxypropyl ethylenediamine, ethylenediamine tetraacetic acid, ethylenediamine tetraacetate, N-hydroxyethyl ethylenediamine triacetic acid and N-hydroxyethyl ethylenediamine triacetic acid;

the stabilizer comprises a first stabilizer and a second stabilizer, and the mass ratio of the first stabilizer to the second stabilizer is (1:1) - (20: 1);

the second stabilizer is any one or a mixture of at least two of thiourea, 2-mercaptobenzothiazole and mercaptosuccinic acid;

2. The electroless copper plating solution according to claim 1, wherein the reducing agent is formaldehyde.

3. The electroless copper plating solution according to claim 1, wherein the pH adjuster is sodium hydroxide or potassium hydroxide.

4. A method for preparing an electroless copper plating solution according to any one of claims 1 to 3, comprising the steps of:

dissolving 20-100 g of complexing agent by using deionized water according to the total mass of 1kg of chemical copper plating solution, adding 1-10 g of cupric salt while stirring, adjusting the pH to 11-11.5 by using a pH regulator after dissolving, adding 0.001-0.02 g of stabilizer and 0.001-0.05 g of surfactant, and uniformly stirring; and finally, adding 2-20 g of reducing agent and uniformly stirring to obtain the electroless copper plating solution.

5. Use of an electroless copper plating solution according to any of claims 1 to 3 for metallization of grid lines of a touch screen.