KR101418035B1 - Method for manufacturing multi layer pcb - Google Patents

Abstract

The present invention relates to a method for manufacturing a multi-layer PCB with plated through-holes, and, more specifically, to a multi-layer PCB (MLB) in which multiple non-conductive layers and conductive layers are alternately laminated and inner wall of a through-hole is electro-plated to electrically connect an inter-layer conductor. The method for manufacturing a multi-layer PCB with plated through-holes includes a process of putting a board in a solution with nano bubbles before a pre-etching process for the multi-layer PCB or before micro-etching process for removing a carbon coating layer applied to a conductor before plating. Therefore, the etching process can be carried out stably and rapidly even etching can be guaranteed even if the use amount of hydrogen peroxide is reduced.

Description

[0001] METHOD FOR MANUFACTURING MULTILAYER PCB [0002] BACKGROUND OF THE INVENTION [0003]

The present invention relates to a method of manufacturing a multilayer printed circuit board having a plated through-hole,

And more particularly, to a method of manufacturing a multilayer printed circuit board (MLB) in which a plurality of nonconductor layers and conductor layers are cross-laminated and electroplating is performed on inner walls of through holes to electrically connect interlayer conductors, And a step of putting the substrate into a solution containing nano bubbles before the pre-etching process of the multilayer printed circuit board, or before the micro-etching process of removing the carbon coating layer coated on the plating conductor, so that the amount of hydrogen peroxide And more particularly, to a method of manufacturing a multilayer printed circuit board having a plated through hole to ensure a stable and fast etching process and to ensure a uniform etching amount.

A multilayer printed circuit board refers to a printed circuit board in which a plurality of conductors and non-conductors are formed by cross-lamination, and typically has four or more conductor layers. The multilayer printed circuit board can provide a high density and highly integrated printed circuit board, In which many electronic products are used.

As shown in FIG. 1, the multilayer printed circuit board is cut off due to non-conductive material between the interlayer conductors to form a through hole (called a through hole, via-hole) in the printed circuit board, A process of electrically connecting the interlayer conductor by plating with a conductive material such as copper is essential.

As a technique for interlayer electroplating on the inner wall of a conventional through hole, there is a method of electroless plating using a Pd (palladium) catalyst and a method of electroplating directly on the inner wall of the nonconductor exposed in the through hole using a conductive material.

Techniques for electroless plating using a palladium catalyst (hereinafter referred to as prior art 1) include a pretreatment process, a tin palladium catalyst coating process, an accelerator process, a copper coating process through electroless chemical copper, a washing process before electroplating .

However, the electroless chemical copper used in the prior art 1 is not only low in productivity due to long processing time, complicated compounds, and characteristics of sensitive electroless chemical copper medicines, but also has a problem that the post-treatment cost of palladium and copper is very high have.

A technique using a conductive material for solving the problems of the prior art 1 includes a method using a conductive polymer and a method using a carbon black or a graphite dispersion.

A method of imparting conductivity to the inner wall of a through hole using a conductive polymer is disclosed in Japanese Laid-Open Patent Application No. 1995-321461 (hereinafter referred to as prior art 2, 1995)

The above-mentioned prior art 2 relates to a technique of providing conductivity to the inner wall of a through hole by using a conductive polymer, and then electroplating to electrically connect between the interlayer conductors.

However, in the conventional art 2, it is difficult to secure sufficient electrical conductivity through the conductive polymer, uniform coating is not applied to the inner wall of the through hole, and voids are generated on the inner wall of the through hole, causing a short circuit.

And a technique of imparting conductivity to the inner wall of the through hole by using a dispersion liquid such as carbon black or graphite (hereinafter referred to as the prior art 3)

As shown in FIG. 1, the prior art 3 has a structure in which an anion is imparted to the dispersed carbon particles, a cationic property is imparted to the non-conductive layer exposed through holes, and anion carbon particles are coated (see [ Thereby enabling electroplating to be performed.

However, in the prior art 3, the anion carbon particles are coated on the surface of a conductor having a cationic property even when the anion carbon particles are coated, thereby causing a problem that the electroplating is not performed completely because the anion carbon particles act as an obstacle in electroplating.

Accordingly, in order to solve the problem of the prior art 3, as shown in [c] of FIG. 1, a micro-etching process is performed in order to remove the conductive anion carbon particles coated on the conductor surface before the electroplating process of the through hole.

Typically, a mixture of sulfuric acid and hydrogen peroxide is used as the microetching solution. However, instability of hydrogen peroxide is a major disadvantage. Also, when a high concentration of hydrogen peroxide is used, there is a problem that the surface of a conductor such as copper is excessively oxidized to have an uneven etching amount. Accordingly, there is a need for a manufacturing method that has a proper and uniform etching amount in hydrogen peroxide at a low concentration in order to improve the stability of production of a printed circuit board.

Particularly, a flexible printed circuit board (FPCB) having a conductor layer of 10 to 20 mu m has a thickness of 0.5 to 1.5 mu m at the time of etching in order to improve the adhesion and to remove foreign substances on the surface of the conductor, Since the etch rate is very low and requires a uniform etching amount as compared with the etching amount of 20 mu m or more in a conventional etching process, it is necessary to control the concentration of the etching solution so that the amount of hydrogen peroxide Reduction is a very important task.

Accordingly, the present invention has been made to solve the above-mentioned problems,

In order to ensure a uniform amount of etching and ensure manufacturing stability while reducing the amount of hydrogen peroxide used in the etching process during the manufacturing process of the multilayer printed circuit board having the through holes, the conductor is put into the solution containing the nano bubbles before the etching process And a method for manufacturing a multilayer printed circuit board comprising the steps of:

The present invention also includes a step of oxidizing a surface of a conductor such as copper to reduce the amount of hydrogen peroxide used for etching, and a step of introducing the substrate into a solution having an ozone concentration of 5 to 10 ppm by using a nano generator It is another object of the present invention to provide a method of manufacturing a multilayer printed circuit board.

The present invention further relates to a solution for use in an etching process comprising 1 to 3% by weight of sulfuric acid, 1 to 3% by weight of hydrogen peroxide, 1 to 3% by weight of stabilizer, 0.1 to 1% by weight of a surfactant, 0.005 To 0.05% by weight of a complexing agent and water in a remaining amount.

Further, the present invention provides a method of etching an etching solution through an etching solution containing 0.1 to 2% by weight of a metal salt and 0.1 to 1% by weight of an organic acid serving as a surface stabilizer so as to increase the activity of the etching agent and the copper surface during the etching treatment. And a method for manufacturing the multilayer printed circuit board.

The present invention also includes a step of cationically ionizing the non-conductive surface using a cationic surfactant while secondarily cleaning the substrate so that the conductive anion carbon can be stably coated on the surface of the nonconductor such as a resin layer in the carbon coating step for electroplating And a method of manufacturing a multilayer printed circuit board.

It is another object of the present invention to provide a method of manufacturing a multilayer printed circuit board including a dry process for removing moisture in a carbon coating step so as to prevent an electroplating failure due to moisture contained in an anion carbon.

The present invention also relates to a multilayer printed circuit board in which a carbon coating process is carried out using a solution consisting of a mixture of at least one conductive carbon and at least one surfactant and a liquid-dispersing intermediate so that the carbon coating is stable and uniform through the liquid- And a method for producing the same.

In order to achieve the above object, a method of manufacturing a multilayer printed circuit board according to the present invention includes:

A) performing a pre-etching process on a multilayer printed circuit board having through-holes formed therein;

B) coating the through hole with conductive anion carbon; And

C) performing a micro-etching process to remove conductive anion carbon coated on the conductor surface of the through-hole; And

D) electrically connecting the interlayer conductor by electroplating the through hole,

Further comprising the step of injecting the multilayer printed circuit board into a solution containing nano bubbles before the pre-etching step of step A) or before the micro-etching step of step C).

In the method of manufacturing a multilayer printed circuit board according to the present invention, the solution containing the nano bubbles is a solution in which dissolved ozone amount is increased by using a nano generator.

In the method of manufacturing a multilayer printed circuit board according to the present invention, the solution in which the amount of dissolved ozone is increased has an ozone concentration of 5 to 10 ppm.

Meanwhile, in the method for manufacturing a multilayer printed circuit board according to the present invention, the etching solution used in the pre-etching step A) or the micro-etching step C) may include 1 to 3% by weight of sulfuric acid and 1 to 3% % Hydrogen peroxide, 1 to 3% by weight of a stabilizer, 0.1 to 1% by weight of a surfactant, 0.005 to 0.05% by weight of a complexing agent and the balance of water.

In the method for manufacturing a multilayer printed circuit board according to the present invention, the stabilizer may be an alkyl amine.

Further, in the method for manufacturing a multilayer printed circuit board according to the present invention, the etching solution is characterized in that 0.1 to 2% by weight of a metal salt and 0.1 to 1% by weight of an organic acid are further added.

In the method for manufacturing a multilayer printed circuit board according to the present invention, the step A) includes a step of cationizing the nonconductive surface of the through hole while washing the substrate secondly before putting the substrate into a solution containing nano bubbles .

Next, in the method for producing a multilayer printed circuit board according to the present invention, the step of cationizing the nonconductor in the step B) is characterized in that a cationic surfactant is used.

In the method for manufacturing a multilayer printed circuit board according to the present invention, the step B) further comprises a dry process for removing moisture from the coated anion carbon.

In the method of manufacturing a multilayer printed recycled substrate according to the present invention, the step B) is performed by a liquid carbon dispersion method, and the diameter of the carbon particles added to the carbon dispersion liquid of the liquid carbon dispersion system is 0.05 탆 to 3.0 탆 .

Furthermore, in the method for producing a multilayer printed recalled substrate according to the present invention, the solution used in the liquid carbon dispersion method in the step B) is composed of water, a mixture of at least one conductive carbon, at least one surfactant and a liquid- do.

The method of manufacturing a multilayer printed circuit board according to the present invention can reduce the amount of hydrogen peroxide used to secure the operation stability of the etching process and ensure a uniform and stable etching amount despite the use of less hydrogen peroxide.

In addition, in the method of manufacturing a multilayer printed circuit board according to the present invention, the oxidation process of the conductor surface can be carried out easily and quickly without using any additional chemicals.

In addition, the method of manufacturing a multilayer printed circuit board according to the present invention can reduce the amount of sulfuric acid and hydrogen peroxide to be used as an etching solution. However, the amount of etching is increased compared to a conventional etching process, , It is possible to easily and quickly perform the through-hole plating operation of the flexible multi-layer printed circuit board having a thin thickness.

In addition, the method for manufacturing a multilayer printed circuit board according to the present invention is suitable for plating a through hole of a minute size, and in particular, it is possible to improve the efficiency of the conductive anion carbon coating process for electroplating and to completely remove the conductive anion carbon residue remaining on the surface of the conductor It is possible to prevent void defects and the like caused by carbon residues.

1 is a conceptual diagram schematically illustrating an electroplating process of a conventional multilayer printed circuit board.
2 is a conceptual diagram schematically illustrating an electroplating process of a method of manufacturing a multilayer printed circuit board according to the present invention.
3 to 7 are experimental results for explaining a method of manufacturing a multilayer printed circuit board according to the present invention.

While the present invention has been described in connection with certain embodiments, it is obvious that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

In the drawings, the same reference numerals are used for the same reference numerals, and in particular, the numerals of the tens and the digits of the digits, the digits of the tens, the digits of the digits and the alphabets are the same, Members referred to by reference numerals can be identified as members corresponding to these standards.

In the drawings, the components are expressed by exaggeratingly larger (or thicker) or smaller (or thinner) in size or thickness in consideration of the convenience of understanding, etc. However, It should not be.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise.

 In the present application, the term " comprising " or " consisting of ", or the like, refers to the presence of a feature, a number, a step, an operation, an element, a component, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

It is to be understood that the first to second aspects described in the present specification are merely referred to in order to distinguish between different components and are not limited to the order in which they are manufactured, It may not match.

In describing a method of manufacturing a multilayer printed circuit board having a plated through-hole according to the present invention, when an unambiguous approximate direction reference is specified with reference to FIG. 2 for convenience, , Left and right are set as shown.

In particular, in FIG. 2, the directions in which the uppermost and lowermost conductors are exposed are set outwards and the opposite direction is set inward, and the inner and outer sides and the upper and lower sides are used in combination according to the description. Unless otherwise specified in the scope, directions are specified in accordance with this standard.

As shown in FIG. 2, a multilayer printed circuit board manufactured according to the present invention is a substrate 10 having a plurality of non-conductors 2 and conductors 1 laminated alternately, .

In general, it is effective that the present invention is applied to the production of a multilayer printed circuit board having four or more conductors 1, in particular, a multilayer flexible printed circuit board (FPCB) having a small thickness, The concept of the double-sided printed circuit board 10 consisting of only two layers is also a concept included in the multilayer printed circuit board 10.

The conductor 1 may be made of a metal such as nickel, gold, palladium, or silver having conductivity. Typically, copper is used. Hereinafter, for convenience of explanation, do.

A non-conductive non-conductive material such as glass or synthetic resin may be used as the non-conductive material 2, and a resin is typically used. For convenience of explanation, the non-conductive material 2 will be described as a resin layer .

Since the connection between the conductors 1 is disconnected by the non-conductor 2, the multi-layer printed circuit board 10 is provided with a through hole 3 penetrating the main body to form a high-density integrated circuit.

The through hole 3 is a concept that includes a through hole in which both the upper and lower portions are perforated or a via hole in which only a part of the through hole 3 is perforated. As a method of forming the through hole 3, a drilling method, a laser machining method, or the like can be considered.

First, as shown in FIG. 2, a method of manufacturing a multilayer printed circuit board according to the present invention includes

A) preparing a multilayer printed circuit board (10) having a through hole (3) formed therein;

B) coating with conductive anionic carbon;

C) micro-etching step; And

D) an electroplating step.

The step A) is a concept including all processes performed before electroplating to electroplating the substrate 10, and typically includes a primary cleaning process of the substrate 10, a pre-etching process, and the like.

The first cleaning step is a step of removing impurities from the prepared substrate 10 and is a step of washing with water or a chemical agent and a part of the nonconductor 2 layer being formed on the conductor 1 when forming the through- Removing debris adhered to the layer (de-smear), and the like.

The pre-etching process is a process for improving adhesion of carbon in an anionic carbon coating step described later and removing fine foreign substances through etching. A detailed description of the pre-etching process will be described in detail later with the micro-etching process.

Next, the present invention includes step B) of coating the prepared multilayer printed circuit board 10 with conductive anion carbon to impart conductivity to the inner wall of the through-hole 3.

The carbon coating process in the step B) is preferably a liquid carbon dispersion method. The carbon coating solution of the liquid phase carbon dispersion method uses water as a solvent. As the carbon coating solution, the present invention includes a mixture of carbon black (CB) and carbon nanotube (CNT).

The carbon coating method using the carbon coating solution may be a chemical dispersion method or a spray dispersion method. A spray dispersion method is more preferable because of the characteristics of the printed circuit board 10.

First, the carbon black used as the carbon particles for imparting conductivity to the resin layer of the substrate 10 is amorphous particles, porous and has a surface area of 45 to 1100 g / m 2 and a size of 0.01 to 0.05 탆. Ketjen black and high black are used for the carbon black. Typically, carbon black manufactured and sold by OCI Korea, a peace drug, and Ebonic Carbon Black Korea can be used.

Since the carbon nanotubes have a cylindrical structure, they are directional, have good electric conductivity on the surface, and have a one-directional orientation, which is suitable for connection between two materials.

The carbon coating solution of the present invention is a mixture of carbon black and carbon nanotubes to form a carbon coating layer. Therefore, when the carbon nanotubes are connected to the carbon black as a net, the electric conductivity is greatly improved.

The carbon nanotubes preferably have a length of 15 to 25 탆 and a diameter of 0.2 to 0.5 탆, and a density of 0.01 g / cm 3. The carbon nanotubes are preferably multi-walled carbon nanotubes (MWCNTs), and single-walled carbon nanotubes (SWCNTs) may be used.

The carbon nanotubes may be carbon nanotubes sold by Hanwha Nanochemical Co., Ltd. or Carbon Nanotech Co., Ltd.

In the step B), the temperature of the conductive anionic carbon coating solution is about 15 to 35 ° C, more preferably 20 to 30 ° C. The coating time in the step B) is 15 seconds to 10 minutes, more preferably 30 seconds to 5 minutes.

The carbon coating liquid of the present invention used in the step B) is a water-soluble mixture of carbon particles. The composition ratio of the carbon black and the carbon nanotubes is 1 to 30 parts by weight of carbon natto tube per 100 parts by weight of carbon black And it is preferable that 5 to 20 parts by weight of carbon nanotubes are mixed with 100 parts by weight of carbon black so as to prevent generation of carbon aggregates in the preparation of the coating liquid. At this time, it is preferable that water as a solvent is mixed in 45 to 55 parts by weight with respect to 1 part by weight of the carbon black.

When the carbon nanotubes are used in an amount of less than 5 parts by weight, the carbon nanotubes are not easily bonded to the carbon black, so that carbon precipitates are easily produced. When the carbon nanotubes are used in an amount of more than 20 parts by weight, the electrical conductivity is not improved. Explain.

In addition, the carbon coating solution of the present invention may further comprise a binder, an anion-imparting agent, and a buffer in addition to the mixture of the carbon black and the carbon nanotube, and one or more surfactants may be further added depending on the diameter of the through-hole.

In this case, the mixture of carbon black and the carbon nanotubes may contain 5 to 20 parts by weight of carbon nanotubes, 5 to 15 parts by weight of an anion imparting agent, 5 to 10 parts by weight of a binder, 5 to 10 parts by weight 10 to 20 parts by weight of a surfactant and water. At this time, it is preferable that water as a solvent is mixed in 45 to 55 parts by weight with respect to 1 part by weight of the carbon black.

The binder is a water-soluble binder for bonding the carbon particles of the carbon black and the carbon nanotube to each other, thereby assisting adhesion of the carbon particles dispersed on the surface of the nonconductive nonconductor which becomes conductive in electroplating.

The binder of the present invention may be a natural or synthetic polymer, a polymerizable monomer or other sticky solid material capable of adhering to carbon particles and capable of receiving an anionic dispersing agent, or a precursor thereof.

For example, water-soluble or water-dispersible substances selected from mono-saccharides and polysaccharides and anionic polymers can be used as the binding agent, and polysaccharide carbohydrates can be included. The binder preferably has a degree of adhesion within the range of 25 to 800 cps.

As a binder used in the carbon coating solution of the present invention, DURITE AL-5801a, manufactured and sold by Boden Packaging and Industrial Products, ACRYSOL, manufactured and sold by Rohm and Haas Company, Philadelphia, Pennsylvania, Polyethylene glycol, polyvinyl chloride, polyvinyl ester and polyvinyl acetate are used as the main components of the binder.

Subsequently, the anion-imparting agent added to the carbon coating solution of the present invention is for connecting the carbon particles to the non-conductive surface of the non-conductive material (2). The weak anionic carbon particles are allowed to have strong anionic property through the anion- When the surface of the nonconductor (2) is cationized, the formation of the carbon coating layer can proceed more easily and quickly.

Examples of the anion-imparting agent include CELQUEST-727S, CELANON-A35G, CELTEX-F530, CECLE-MC75, CECLE-MC65KN-HA65C, KD-DF180 and CELQUEST-206.

The buffer added to the carbon coating solution of the present invention acts to suppress or minimize the change in pH that may occur in the step B), thereby maintaining the pH range constant, And the nitrogen concentration of the buffer component can be measured and controlled to uniformly control the carbon coating control in the step B).

The buffer may be a buffer having a pH of 9 to 12, preferably a pH of 9.5 to 11.5, and more preferably a pH of 10.5 to 11.0.

Meanwhile, the carbon coating solution of the present invention may be prepared by further selecting a surfactant.

The surface active agent is free from penetration of the carbon coating liquid into the through holes to facilitate the formation of the carbon coating layer on the surface of the non-conductive material 2, thereby reducing the surface tension so that the conductivity can be easily imparted through the carbon coating. And to wet the surface of the nonconductor.

A through hole of a multilayer printed circuit board typically has a diameter of 0.05 to 5 mm, and a through hole having a diameter of 4 to 5 mm does not require a surfactant. However, in order to perform carbon coating on a through hole having a diameter of 4 mm or less Surfactants are preferably added.

Further, the carbon coating liquid of the present invention can be applied to both of a double-sided printed circuit board having two conductor layers and a multilayer printed circuit board having a plurality of (for example 24) conductor layers, It is more preferable that a predetermined amount of a surfactant is further added so that the carbon coating is performed.

The surfactant may be a non-ionic surfactant, sold by Triton X-100, 850, 960 sold by Rohm and Haas, Philadelphia, Pennsylvania, or at the Minnesota Mining & Manufacturing Company located in Settle, Minnesota, USA FLUORAD ^ㄾ that FC-120, FC-129, FC-135, and the like FC-430, FC-431, or sold in SDS or US Cytec company sold in Japan junseyi Chemical Co., OT-75 can be used.

Meanwhile, the carbon coating solution of the present invention should be mixed with water, which is a solvent, at a suitable composition ratio so that carbon coagulation is not generated, so that the carbon coating smoothly proceeds and electric conductivity can be improved.

Accordingly, the carbon coating solution of the present invention comprises 2 to 3 wt% of carbon black, 0.1 to 0.3 wt% of carbon nanotubes, 0.2 to 0.3 wt% of a surfactant, 0.1 to 0.2 wt% of an anionic dispersant, 0.2% by weight of a binder, 0.1 to 0.2% by weight of a buffer and a residual amount of water.

In order to confirm the electric conductivity according to the content of the compositions as the carbon coating liquid with improved electric conductivity, the applicant of the present invention conducted the following experiment.

FIG. 3 is a graph showing the results of an experiment for confirming the effect of the carbon coating solution according to the present invention. The applicant of the present invention found that when the substrate 10 is carbon-coated using the carbon coating solution having the composition ratio, I could confirm.

Example 1

A surfactant and water were mixed with an aqueous solution prepared by mixing carbon black having a particle size of 0.04 mu m and carbon nanotubes, and the mixture was stirred for the first time. Then, a buffer composed of potassium carbonate and potassium bicarbonate was added to the primary solution, 10 to 11, and then a binder and an anion imparting agent are further added to the secondary agitation liquid and stirred to form a carbon coating liquid.

20 g of carbon black is used for the carbon coating solution according to the first embodiment, and the amount of the carbon nanotubes, the buffer, the surfactant and the anion imparting agent are varied as shown in the following table to form a carbon coating solution.

Each carbon coating solution thus formed was allowed to stand for 3 days to determine the presence of carbon deposits in the solution to measure the degree of dispersion, to forcibly evaporate the carbon coating solution, to measure the resistance of the remaining carbon flocculating agent, The particle size of the agglomerate is measured.

As shown in (1), (2), and (3) of FIG. 3, when the carbon nanotubes are mixed at less than 0.1 wt%, the electrical resistance increases and the electrical conductivity decreases. When the carbon nanotubes are mixed in more than 0.3 wt% And it was confirmed that it was difficult to use it as a carbon coating liquid because dispersion was not properly performed.

As shown in (3), (4) and (5) of FIG. 3, when the binder is added in an amount of less than 0.1% by weight, the electrical resistance is increased to decrease the electrical conductivity. And it was confirmed that it is not effective to improve the electric conductivity.

3, 6, and 7 in FIG. 3, when the anion imparting agent is added in an amount of less than 0.1% by weight, the electrical resistance is increased and the electrical conductivity is lowered. When the anion imparting agent is added in an amount exceeding 0.2% by weight, And it was confirmed that it is not effective to improve the electric conductivity.

In addition, applicants of the present invention have found that when carbon black is mixed in an amount of less than 2% by weight in the preparation of a carbon coating liquid during the development of a carbon coating liquid having improved electrical conductivity, electrical resistance is increased and electrical conductivity is lowered and more than 3% It was confirmed that the carbon particles were not dispersed properly due to the formation of carbon precipitates.

In addition, when the surfactant is added in an amount of less than 0.2% by weight in forming the carbon coating solution for a multilayer printed circuit board, carbon precipitates are generated and the carbon particles are not properly dispersed. When the surfactant is added in an amount exceeding 0.3% by weight, And it was confirmed that it did not affect.

As can be seen from (3) in FIG. 3, when the carbon coating liquid is formed at the composition ratio described above, not only the electric resistance is low but also the carbon particles having the improved electrical conductivity have the smallest carbon particle size, It was confirmed that a coating layer can be formed.

In addition, applicants of the present invention have confirmed through experiments that the electric conductivity of the carbon coating solution formed through the above composition ratio is improved compared to the carbon coating solution used in the related art.

FIG. 4 is a diagram illustrating the results of measurement according to the above experiment. FIG. 4A is a result according to Example 2, and FIG. 4B is a result according to Comparative Example 1.

Example 2

The multilayer printed circuit board is coated using the carbon coating liquid prepared under the conditions (3) of Example 1 above.

Comparative Example 1

Conventionally, a multilayer printed circuit board is coated using a carbon coating solution in which carbon nanotubes are not mixed. The other constituents added at this time are the same as those in the second embodiment.

The through holes of each of the coated multilayer printed circuit boards of Example 2 and Comparative Example 1 were measured for electrical conductivity to confirm the electrical conductivity and then the etching process and the electroplating process described below were carried out under the same conditions, Check the electroplating condition in the hole. In order to confirm the accuracy of the results, three specimens of a double-sided printed circuit board and a four-layer printed circuit board were prepared as the multilayer printed circuit board prepared in Example 2 and Comparative Example 1, and the experiment was conducted.

As shown in the following table, the coating of Example 2 and the coating of Comparative Example 2 are performed twice as in the case of the conventional carbon coating process, and the secondary cleaning process described above is performed under the same conditions before each carbon coating process.

As can be seen from FIG. 4A, when carbon coating is performed using the carbon coating solution according to the present invention, a lower electric resistance value is measured than in the case of using the conventional carbon coating solution as shown in FIG. 4B, .

Further, the applicant of the present invention has found that, in comparison with the case where a large amount of carbon black is used for securing the electric conduction path or the carbon coating process is performed twice or more through the experiment, carbon coating is performed using the carbon coating liquid according to the present invention It was confirmed that a carbon coating layer having improved electrical conductivity was formed even when the carbon coating process was performed only once.

FIG. 5 is a result of an experiment for confirming that the electric conductivity is improved by performing the carbon coating process once using the carbon coating solution according to the present invention.

Example 3

The multilayer printed circuit board is coated using the carbon coating liquid prepared under the conditions (3) of Example 1 above. In Example 3, the carbon coating process is performed only once, and each of the secondary cleaning processes described above is performed under the same conditions before each carbon coating process, as shown in the following table.

The electrical resistance was measured for the through holes of the multilayer printed circuit board through Example 3 to confirm the electric conductivity and the electroplating state was confirmed in the through holes by performing the etching process and electroplating process described below under the same conditions . In order to confirm the accuracy of the results, three specimens of the double-sided printed circuit board and the four-layer printed circuit board were prepared as the multilayer printed circuit board prepared in Example 3, and the experiment was conducted.

5, when the carbon coating liquid according to the present invention is used, even when the carbon coating process is performed only once, the carbon coating process is more improved than the conventional carbon coating process (see FIG. 4B) It can be confirmed that it has electrical conductivity.

Accordingly, the present invention can achieve a low electric resistance of 180 k OMEGA or less even when the carbon coating process is performed only once, thereby improving electric conductivity, improving the productivity of a multilayer printed circuit board, reducing unnecessary use of chemicals The cost can be reduced.

The present invention further includes a dry process for removing water from the coated conductive anion carbon by the above step B).

The drying process may be a method of drying at room temperature, a drying method using vacuum, or a drying method using high temperature air. More preferably, a high-temperature air drying method is used.

The high-temperature air drying method is performed for 5 to 45 minutes, and the temperature of the air is 75 to 120 ° C, more preferably 80 to 98 ° C.

The conductive anion carbon is completely coated on the surface of the inner wall 3A of the through hole 3 through the above dry process and more specifically the surface of the nonconductor 2 exposed to the inner wall 3A of the through hole 3.

Next, the present invention carries out a micro-etching process for removing the conductive anion carbon particles (carbon layer 5) remaining on the surface of the conductor 1, as shown in [d] .

The micro etching process is preferably a selective etching method using a gas plasma or an ion beam for the carbon layer 5 on the surface of the conductor 1.

This is because the carbon layer 5 is formed on the inner wall 3A of the through hole 3 due to the conductive anion carbon particles during electroplating in step D) to ensure the electroconductivity so that the surface of the nonconductor 2 can be electroplated On the other hand, when a small amount of the conductive anionic carbon particles remain on the surface of the conductor 1, the adhesion between the surface of the conductor 1 and the electroplating layer is weakened to prevent the voids in the multilayer printed circuit board 10, .

In order to completely remove the carbon layer 5 from the surface of the conductor 1, a micro etching solution is used. The microetching process in the step C) may be a spraying method of spraying the micro etching solution onto the substrate 10 or a locking method of immersing the substrate 10 in the micro etching solution.

At this time, a mixture of sulfuric acid, hydrogen peroxide, water and the like is used as the solution used in the pre-etching step of the step A) and the micro-etching step of the step C).

Sulfuric acid acts as an initiator in the copper conductor layer etching reaction, and hydrogen peroxide acts as an etching promoter. The copper conductor etching process using only sulfuric acid has a reaction formula of Cu + H ₂ SO ₄ -> CuSO ₄ + H ₂ , which is dangerous in the etching process and has a disadvantage in that the process time is slow due to the production of hydrogen gas.

In this process, when hydrogen peroxide is mixed, it has a reaction formula of Cu + H ₂ O ₂ + H ₂ SO ₄ -> CuSO ₄ + 2H ₂ O, where copper is Cu + H ₂ O ₂ -> CuO + H ₂ O reaction scheme. The generated hydrogen peroxide reacts with copper to form copper oxide, and copper oxide reacts with sulfuric acid to produce copper sulfate. Therefore, when the etching process is performed by mixing sulfuric acid and hydrogen peroxide, generation of hydrogen gas with high risk can be prevented, and the processing time is very fast, thereby shortening the entire etching process time.

However, if the amount of hydrogen peroxide is increased, a post-treatment process is required to prevent environmental pollution after the treatment, and stable and uniform etching can not be guaranteed due to instability of hydrogen peroxide during the treatment.

Accordingly, the present invention includes a step of injecting the coated substrate into a solution containing nano bubbles before the pre-etching step of step A) or before the micro-etching step of step C), thereby reducing the amount of hydrogen peroxide The working stability due to the instability of hydrogen peroxide is improved and a uniform etching amount can be ensured even when the amount of hydrogen peroxide is increased.

The solution containing the nano bubbles is manufactured using a nano bubble generator. The nano bubble generator is a device that generates nano bubbles with a particle size of 10 nm to 50 nm in a specific solution to increase the amount of dissolved gas to 5 to 80 times and increases the holding time of the gas. The gas acts on the copper surface to oxidize, Even if the amount of hydrogen peroxide to be used is reduced, a stable and uniform etching amount can be ensured by the above reaction formula.

Various methods may be considered to form the anionic oxide film layer 4 on the surface of the conductor 1 of the substrate 10. In the embodiment of the present invention, the surface of the conductor 1 is oxidized using ozone, To form the oxide film layer 4.

More specifically, the surface of the conductor 1 is oxidized by using a solution in which dissolved ozone amount of water is increased as a solution for forming the oxide film layer 4. The water used herein is preferably deionized water.

Ozone oxidizes and oxidizes metallic materials. For example, when copper is used as conductor (1), ozone oxidizes on the surface of copper (1) copper to form thin copper oxide, which is anionic Therefore, if the conductive anion carbon particles are coated with the conductive anion carbon particles in the step B), the surface of the conductor 1 and the carbon particles become the same anion, so that the coating amount of the carbon particles can be reduced.

Further, the present invention increases the dissolved ozone amount of the solution by using the gas introduced into the nano bubble generator as ozone. The concentration of ozone in the solution of step B) is preferably 5 to 10 ppm, and the amount of ozone to be supplied is preferably 20 g / m 3 to 30 g / m 3.

The treatment temperature of the oxide film layer 4 forming step is preferably 20 to 30 DEG C, and the substrate 10 is immersed in the solution in a vertical manner, and the treatment time is 10 to 30 seconds.

6 is a graph showing the results of an experiment for confirming formation of the oxide layer 4 through the step B according to the present invention. FIG. 6A is a measurement result of Example 4, and FIG. 6B is a measurement result of Comparative Example 4 . The applicant of the present invention confirmed that the anionic oxide film layer 4 was formed on the surface of the conductor 1 through the step B).

Example 4

After the copper specimen is washed with water for 30 seconds, the nanobubble generator in the step B) is operated to treat 600 ml of the solution having an ozone concentration of 7 ppm by the vertical immersion method and then washed with water.

Comparative Example 4

The gypsum piece is simply washed with water only by omitting the step (B).

The surface of each of the copper specimens according to Example 4 and Comparative Example 4 was subjected to EDX measurement (S-4300 model of HITACHI Corporation, Japan). Here, EDX (Energy Dispersive X-ray Spectroscopy) measurement is a method in which electrons generated by the application of an electric current are accelerated and collided with a specimen. At this time, internal electrons in the specimen are discharged to the outside by incident electrons, This is a method of analyzing a sample using X-ray energy having a unique value for each atom by measuring and radiating X-ray while stabilizing the atom and qualitatively and quantitatively analyzing it.

As a result of the EDX measurement, the anisotropic oxide layer containing ozone (oxygen) was not formed in the specimen of Comparative Example 4 in FIG. 6B. On the other hand, as shown in FIG. 6A, 4) was oxidized to form an anionic oxide film layer 4 (copper oxide film) containing ozone (oxygen) on the copper surface.

7 is a graph showing the results of an experiment for confirming the etching effect of the anionic oxide layer described above. FIG. 7A is a measurement result of Experimental Example 5, and FIG. 7B is a measurement result of Comparative Example 5. The applicant of the present invention has confirmed that the etching effect is higher than that in the case where the amount of hydrogen peroxide is used through the anionic oxide layer forming step but the amount of hydrogen peroxide is increased.

Example 5

A solution having an ozone concentration of 5 ppm or more was prepared using a nano bubble generator connected to an ozone generator, and then the solution of copper sulfate was treated to form an anionic oxide film layer. Then, 1 wt% of hydrogen peroxide and 1 wt% of hydrogen peroxide By weight, and then immersed in an etching solution containing 1% by weight of a stabilizer, etched for 30 seconds, and then the amount of etching is measured.

Comparative Example 5

The copper foil not subjected to the anionic oxide layer forming step of Example 5 was immersed in the same etching solution as in Example 5 for the same time to measure the etching amount.

As shown in FIG. 7B, in the case of using 1 wt% of hydrogen peroxide in Comparative Example 5, the amount of etching was so small as compared with the case of using 3 wt% of hydrogen peroxide and the amount of hydrogen peroxide was increased in order to secure a stable etching amount can confirm.

On the contrary, as shown in FIG. 7A, it can be seen that Example 5 had a higher etching amount when the same hydrogen peroxide was used as compared with Comparative Example 5, and furthermore, when 1 wt% of hydrogen peroxide was used in Example 5, 5 showed no significant difference in the case of using 3 wt% of hydrogen peroxide and the etching amount, and it can be confirmed that a stable etching amount can be secured even if the amount of hydrogen peroxide used is reduced.

1 to 3% by weight of sulfuric acid, 1 to 3% by weight of hydrogen peroxide, 1 to 3% by weight of a stabilizer and 0.1% by weight of a stabilizer. To 1% by weight of a surfactant, 0.005 to 0.05% by weight of a complexing agent, and a balance of water.

Alkyl amines are used as the stabilizer, and alkyl amines contribute to enhancement of the roughness of the etched surface and inhibit generation of irritating harmful gas. The alkylamine may be monoethylamine (MEA), monobuthylamine (MBA), ethylene diamine (EDA), triethylamine (TEA), triethylenetetramine (TETA) or diethylenetriamine (TETA).

The complexing agent prevents the re-precipitation of copper ions by lowering the stability of the drug due to the high concentration of copper ions in the solution due to the continuous etching of the copper surface and securing a certain level of chemical stability to copper ions at a high concentration. can do. Examples of the complexing agent include ethylenediaminetetraacetic acid (EDTA), diethylene triamine pentaacetic acid (DTPA), and nitrilotriacetic acid (NTA).

The solution to be used in the etching process in the step A) and the step C) is further added with 0.1 to 2% by weight of a metal salt and 0.1 to 1% by weight of an organic acid.

The metal salt plays an ongoing role in starting and maintaining the etching while increasing the activity of the etching solution and the copper surface. As the metal salt, a trivalent iron compound, a Halogen Complexer and the like are preferably used.

The organic acid may be glycolic acid, picolinic acid, acetic acid, citric acid, lactic acid, etc., and serves as a surface stabilizer in the etching treatment and at the same time, serves to improve the surface.

At this time, the present invention includes a step of cationizing the surface of the nonconductor 2 while the substrate 10 on which the anionic oxide layer 4 is formed is cleaned in the step A).

The secondary washing and cationization process in the step A) may be carried out using water or a drug or both, as in the primary washing process in the step A), more preferably, % Is used as the cleaning solution. The cleaner solution is preferably a cationic surfactant as the drug.

The cleaning process with the cleaner solution removes impurities that may adhere to the surfaces of the conductors 1 and 2 of the substrate 10 so that the conductive anion carbon coating process of step B) At the same time, the nonconductive non-conductive layer 2, that is, the resin layer surface exposed to the inner wall of the through hole 3 has a positive charge, that is, cationic, so that the conductive anion carbon Allowing the particles to function more fully as a catalyst.

The cationic surfactant reacts only with non-metallic non-conductive material 2 and does not react with the anionic oxide film layer 4 coated on the surface of the conductor 1.

The cleaning step through the cleaner solution will be described in more detail as follows. First, the substrate 10 on which the oxide film layer 4 is formed is subjected to secondary cleaning through a mixed solution of water and a cleaning agent (surfactant).

As an example of the cleaner (surfactant), BH @ cleaner commercially available from Olin Hunt Specialty Products Inc., located in West Jefferson, New Jersey, USA, can be used. The solution is cationic, The cationization is as described above.

Next, the substrate 10 is cleaned, the remaining cleaner solution is removed (washed with water), and the surface of the nonconductor 2 exposed to the inner wall of the through hole 3 is further made cationic so that conductive anionic carbon particles are dispersed on the surface of the nonconductor 2 An additional cationization process is carried out to allow more complete coating.

The additional cationization process may be a mixed solution of various chemicals and water. Typically, a mixed solution of BH @ stater and water commercially available from the same company as BH @ cleaner and a mixed solution of BH @ conditioner and water may be used .

After the substrate 10 is first treated with a mixed solution of BH @ stater and water, the substrate 10 is second treated using a mixed solution of BH @ conditioner and water, The surface of the nonconductor 2 is completely cations so that the conductive anion carbon particles are more completely coated on the surface of the nonconductor 2 to be fixed, It is possible to prevent defects such as voids or plated folding defects.

Next, the present invention includes a step of electrically connecting the interlayer conductor 1 by electroplating the substrate 10 having been subjected to the step C), as shown in [e] of FIG.

The conductive anion carbon layer is formed on the surface of the nonconductor 2 through the above steps so that the conductivity is secured over the entire inner wall 3A of the through hole 3 so that the interlayer conductor 1 between the non- When the electroplating layer 6 is formed on both the surfaces of the conductor 1 and the nonconductor 2 which are exposed to the through hole 3 by applying a current in the step D) And there is a great advantage in terms of thickness control of the plating.

The detailed process and effect of the electroplating step in the step D) are not related to the essential features of the present invention, and a detailed description thereof will be omitted.

While the present invention has been described with reference to the accompanying drawings, it is to be understood that the present invention is not limited to the details of various modifications, permutations, and permutations And such modifications, alterations, and substitutions are to be construed as being within the scope of protection of the present invention.

10: multilayer printed circuit board 1: conductor
2: Non-conductor 3: Through hole
4: anionic oxide layer 5: conductive anion carbon layer
6: Electroplating layer

Claims (10)

A) performing a pre-etching process on a multi-layer printed circuit board on which a plurality of conductors and non-conductors are stacked and through holes are formed;
B) coating the through hole with conductive anion carbon; And
C) performing a micro-etching process to remove the conductive anion carbon coated on the surface of the conductor exposed through the through-hole; And
D) electroplating the through holes to electrically connect the plurality of conductors,
Further comprising the step of injecting the multilayer printed circuit board into a solution containing nano bubbles prior to the pre-etching step of step A) or before the micro-etching step of step C) ≪ / RTI > The method according to claim 1,
Wherein the solution containing the nano bubbles is a solution in which the amount of dissolved ozone is increased by using a nano generator. 3. The method of claim 2,
Wherein the solution in which the amount of dissolved ozone is increased has an ozone concentration of 5 to 10 ppm. 4. The method according to any one of claims 1 to 3,
The etching solution used in the pre-etching step of step A) or the micro-etching step of step C) may contain 1 to 3% by weight of sulfuric acid, 1 to 3% by weight of hydrogen peroxide, 1 to 3% , 0.1 to 1% by weight of a surfactant, 0.005 to 0.05% by weight of a complexing agent and water in a remaining amount. 5. The method of claim 4,
Wherein the stabilizer is an alkyl amine (Alkyl Amine). 5. The method of claim 4,
Wherein the etching solution comprises 0.1 to 2% by weight of a metal salt and 0.1 to 1% by weight of an organic acid. 4. The method according to any one of claims 1 to 3,
Wherein the step A) includes a step of cationizing the surface of the non-conductive material exposed through the through hole while washing the substrate secondly before the substrate is charged into the solution containing the nano bubbles. / RTI > 8. The method of claim 7,
Wherein the step of cationizing the nonconductor of step (B) comprises using a cationic surfactant. 4. The method according to any one of claims 1 to 3,
Wherein the step B) further comprises a drying step for removing moisture from the coated anion carbon. 4. The method according to any one of claims 1 to 3,
The step B) is performed by a liquid carbon dispersion method,
Wherein the diameter of the carbon particles added to the carbon-dispersed solution of the liquid carbon dispersion method has a size of 0.05 mu m to 3.0 mu m.

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