KR100619362B1 - Method for electroless plating on printed circuit board using photocatalyst - Google Patents

Abstract

The present invention relates to an electroless plating method of a printed circuit board using a photocatalyst. After coating a nano TiO ₂ sol solution on the surface of a substrate, ultraviolet rays are irradiated to form an activation layer, and the electroless metal plating solution is contacted thereto. To form a metal plating layer.

According to the method of the present invention, it is possible to replace the activation process of the substrate surface using expensive metal catalysts in electroless metal plating of printed circuit boards by photocatalyst technology using TiO ₂ sol, thereby providing high reliability and Excellent adhesive properties can be obtained.

Photocatalyst, titanium dioxide, sol solution, printed circuit board, metal plating

Description

Electroless plating method of printed circuit board using photocatalyst {Method for electroless plating on printed circuit board using photocatalyst}

1 is a flow chart schematically showing a copper plating process of a printed circuit board according to the prior art.

2 is a flow chart schematically showing a gold plating process of a printed circuit board according to the prior art.

3 is a cross-sectional view showing a state in which a gold plated layer is formed on a printed circuit board according to the related art.

4 is a view showing the anatase and rutile crystal structure of TiO ₂ used as a photocatalyst in the present invention, respectively.

5 is a flowchart schematically illustrating a copper plating process of a printed circuit board according to an exemplary embodiment of the present invention.

6 is a flow chart schematically showing a gold plating process of a printed circuit board according to an embodiment of the present invention.

7 is a cross-sectional view showing a state in which a gold plated layer is formed on a printed circuit board according to the present invention.

The present invention relates to an electroless plating method of a printed circuit board using a photocatalyst. More specifically, after the activation layer is formed on the surface of the substrate by using a nano TiO ₂ sol solution, the electroless metal plating layer is formed to form a printed circuit using a photocatalyst which can give high reliability and excellent adhesion when implementing a micro circuit. It relates to an electroless plating method of a substrate.

Recently, according to the trend of high density, high speed, and miniaturization of electronic components, research on a new packaging substrate that can cope with system in packaging has been actively conducted. In addition, in order to meet these demands, the implementation of microcircuits has also emerged as a major research subject.

Accordingly, various methods have been proposed for the implementation of fine circuits, and many studies have been conducted to cope with high-layer and high speed. In particular, since the verification of the reliability has to be reproduced after the formation of the microcircuit, the importance of the product becomes more important because mass production is possible in the final stable state.

The semi-additive method, which has been widely applied to the implementation of a microcircuit, is implementing a microcircuit by accumulating electrolytic copper on a seed layer formed by electroless plating. In addition, recently, in preparation for mass production of fine circuits in the future, instead of the electroless plating, which is a conventional seed layer, surface modification by plasma and a method of forming a seed layer on the surface by sputtering them have also been studied.

However, this microcircuit implementation suffers significant damage if the final reliability fails. In particular, there is a high possibility of being damaged by conduction in places where conduction is not possible due to ion migration among product reliability. This phenomenon does not occur in a general place, but after mass production, especially when used in a severe environment (considering humidity, temperature, etc.), a phenomenon may occur without the user's knowledge.

In this regard, Japanese Patent Laid-Open No. 8-253869 is a method of forming an electroless plated film having good adhesion while maintaining the surface accuracy of plating and dimensional accuracy of a resin molded article. A method of performing sea plating is disclosed. In addition, Japanese Patent Application Laid-open No. Hei 10-88361 discloses an electroless plating method in which surface treatment is performed using an alkali solution containing a nonionic surfactant after ultraviolet irradiation in order to further improve adhesion during electroless plating.

However, the above-mentioned methods include surface treatment in an alkali solution or a degreasing solution after irradiating ultraviolet rays to the resin surface, surface treatment with an activating solution such as a Pd-Sn colloidal liquid or a complexing liquid, and an acid activation treatment for removing Sn. In the surface treatment process of, the electroless plating tends to be unprecipitated when the resin surface is in contact with the air, and thus there is a disadvantage in that the electroless plating cannot be stably performed.

As described above, attempts have been made to adhere the electroless metal plating layer to the insulating material by using an expensive Pd metal catalyst or the like in the existing process, but this method only forms a satisfactory circuit in terms of reliability. However, there is a problem in that it is difficult to obtain required characteristics when applied to the implementation of microcircuits, which are requirements of the industry in the future.

Therefore, there is an urgent need for an improved treatment process considering high reliability and bonding with an insulating material when implementing a fine circuit.

Therefore, in the present invention, as a result of various studies to solve the problems as described above, super hydrophilicity is replaced by replacing the existing activation process of a printed circuit board using an expensive metal catalyst with a treatment method using a TiO ₂ sol photocatalyst. The present invention has been completed by focusing on the high adhesion effect due to the problem of lowering reliability due to defects such as ion migration and delamination when implementing a fine circuit.

Accordingly, an object of the present invention is electroless plating method of a printed circuit board using a photocatalyst which has high reliability when implementing a fine circuit, has excellent adhesion effect with an insulating material, and can be utilized as a low profile material for high speed response. To provide.

Electroless plating method of a printed circuit board using a photocatalyst according to the present invention for achieving the above object:

In the plating method of a printed circuit board,

(a) providing a nano TiO ₂ sol solution having a pH of 2-7;

(b) coating the TiO ₂ sol solution on the surface of the substrate and then irradiating ultraviolet rays to form an activation layer;

(c) providing an electroless metal plating solution comprising at least one metal salt, at least one reducing agent and at least one organic acid; And

(d) contacting the metal plating solution on the activation layer of the substrate to form an electroless metal plating layer;

Characterized in that it comprises a.

Here, the TiO ₂ sol solution further comprises at least one transition metal compound selected from the group consisting of Cr, Fe, Nb and V, the content is 0.05 to 0.5% by weight.

Further, the TiO ₂ and the average particle diameter of the TiO ₂ in the sol solution is 5~60㎚, the concentration of the TiO ₂ is 0.05~0.5 mol%.

On the other hand, the irradiation amount of the ultraviolet ray is 5 to 80mw / cm 2, and the ultraviolet irradiation time is 5 to 30 minutes.

The metal is selected from the group consisting of copper, nickel, cobalt, gold, silver, palladium, platinum, rhodium, iron, aluminum, tantalum, titanium nitride, titanium, tungsten, tantalum nitride, tungsten nitride or combinations thereof The layer has a thickness of 0.05 to 0.8 mu m.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

As described above, according to the present invention, a microcircuit is realized by replacing the activation process of the substrate surface using an expensive metal catalyst performed during electroless metal plating of a printed circuit board (PCB) with a photocatalyst technique using a TiO ₂ sol. There is also provided an electroless plating method of a printed circuit board having high reliability.

In order to contrast with the plating method according to the present invention, Figures 1 and 2 show a schematic process flow diagram of the copper plating and gold plating process of the conventional printed circuit board, respectively. 3 shows a state in which a gold plated layer is formed on a printed circuit board according to the prior art.

1 to 3, the plating method of a printed circuit board according to the prior art will be described.

The ultimate purpose of electroless chemical copper plating is to form a conductive film on the drilled odd resin wall to enable electrocopper plating in the hole. In general, electroless chemical copper plating has a thickness of about 0.2 to 1.2 μm, and then an electrolytic copper plating obtains a thickness capable of securing product reliability.

Copper plating process of the printed circuit board according to the prior art is shown in Figure 1, roughly (1) cleaning (conditioning) → (2) soft etching → (3) free dip → (4) catalyst activation treatment → (5) Reduction → (6) electroless chemical copper plating → (7) acid treatment → (8) electrocopper plating → (9) antirust, water washing, drying.

Here, (1) the cleaner & conditioner process removes organic substances remaining on the substrate to improve wettability, and lowers the surface tension by using a surfactant to help the water-soluble chemicals adhere to the hole surface well. In addition, by removing the (-) polarity of the glass fiber is converted to a (+) pole or a non-polar, in particular when using a catalyst in the colloidal form is given a condition to easily attach the catalyst to the glass fiber.

(2) In the soft-etching process, the surface of the substrate is etched by about 1 μm to remove foreign substances to improve the adhesion between the copper foil surface and the plated copper. Generally, sulfuric acid and hydrogen peroxide or sulfuric acid and persulfuric acid are used.

(3) In the pre-dip process, the thin oxide film on the Cu surface is removed to prevent the Cu ions from entering the catalyst, thereby protecting the catalyst, and the purpose and chemicals vary depending on the catalyst chemicals. For example, in the case of using a colloidal (Sn-Pd type) catalyst, since it is stable at pH 1 or less, it becomes unstable even by inflow of water. Therefore, the treatment of the pH-adjusted chemicals before the catalyst treatment to control the liquidity of the aqueous solution buried in the substrate, that is, to adjust the liquidity to a strong acid to prevent a sudden pH change of the catalyst. On the other hand, in the case of using a Pd complex, the adsorption is not possible if copper oxide is present, so the pH is maintained at less than 4 with sulfuric acid, and a small amount of surfactant is used to improve the adhesion of the catalyst.

(4) In the activation process using a catalyst, a catalyst is adsorbed on the insulating layer as a catalyst necessary for activating the chemical copper precipitation reaction on the resin. As a catalyst, Pd-Sn colloid (acidic) or Pd ion complex compound (alkali: 9.5≤pH) ≤ 10.5). In this process, Pd ions are attached, which are reduced to metal in the subsequent process of reduction.

(5) In the reduction process, a Pd metal that actually acts as a catalyst is obtained. In the case of using a Pd-Sn colloid, an excess of Sn is dissolved and removed, and Sn ²⁺ is oxidized to reduce Pd ^2+, thereby reducing the metal Pd. Is exposed and when a Pd complex is used, Pd ²⁺ is reduced to precipitate metal.

(6) In the electroless chemical copper plating process, copper ions are precipitated through a chemical reaction according to Scheme 1 below.

^{Cu 2+ + HCHO + OH - -} > Cu metal + HCOO - + H 2

The chemical copper precipitation reaction is started by the reaction promoted by the Pd catalyst, at which time the reaction is further activated by the hydrogen gas produced by the reaction, it is also called autocatalytic reaction.

(7) In the acid treatment, the substrate having passed through the chemical copper is neutralized with acid to have the same liquidity as the electroplating solution.

(8) In the electrocopper plating process, the basic liquid composition is generally Cu ²⁺ ; H ₂ SO ₄ for improving the conductivity of the plating liquid; Cl ^- which acts as an accelerator of plating and assists in forming a black film in the case of a soluble anode; Polishes to promote plating growth; And a smoothing agent for suppressing plating growth, and the like to perform electrolytic copper plating.

(9) A rust preventive process is a process that can be selectively performed as needed, and is a process for preventing oxidation of the plated copper surface. Finally, the drying process is typically carried out for 30 minutes to 1 hour at a temperature of 150 ± 20 ℃.

On the other hand, the gold plating process of the printed circuit board according to the prior art is roughly as shown in Figure 2, (1) cleaner (50 ~ 60 ℃) → (2) hot water (35 ~ 45 ℃) → (3) pickling → (4) Soft-etching → (5) Pre-Dip → (6) Activation Treatment → (7) Ni Plating → (8) Au-strike → (9) Au Plating → (10) Hot Dip (65 ~ 75 ℃) → (11) Two-stage hot water tax (35 to 45 ° C) → (12) Drying (90 to 100 ° C) → (13) Thickness and adhesion test (Au / Ni thickness-XRF measuring instrument) → (14) Appearance inspection (magnifying glass) And the like process.

Here, the main process (1) in the cleaner process is to remove contaminants in the processing of the printed circuit board (SR residue, CuO melting on the Cu surface), and improve the hydrophilicity of the printed circuit board surface.

(3) The pickling process neutralizes the surfactant components remaining in the pretreatment process and adjusts the surface of the printed circuit board so that the subsequent soft-etching process can be quickly processed. Typically performed with H ₂ SO ₄ solution.

(4) In the soft-etching process, the contaminated Cu surface is removed during processing of the printed circuit board, the oxide film on the Cu surface is removed, and the Cu surface of the printed circuit board is uniformly dissolved. In order to make it adhere uniformly and to improve the adhesiveness of electroless Ni plating, it is normally performed with 15-35 mL / L sulfuric acid and 10 g / L Cu or less at the temperature of 20-30 degreeC.

(5) The pre-dip process maintains the stability of the activation bath in the subsequent activation process, and prevents the incorporation of impurities (Cu, sulfuric acid, etc.) and moisture in the entire process, which is usually performed at pH 4.5 to 5.5. .

(6) The activation process is a process for selectively giving a Pd catalyst to the Cu surface of a printed circuit board, and when it is attached to the PSR portion, defects occur due to smearing of the EL-Ni bridge. Usually, it is performed under the conditions of 25-35 degreeC, Pd concentration 70-90 mg / L, Cu concentration 50 ppm or less, and pH 3.2-3.5.

(7) Ni plating process is normally performed under the conditions of 77-83 degreeC, nickel ion concentration 4.3-5.0 g / L, pH 4.5-4.7.

(8) Au-strike process is normally performed under the conditions of 82-88 degreeC, Au ion concentration 0.8-1.4g / L, pH 4.8-6.0.

(9) Au plating process is performed under the conditions of 82-88 degreeC, the density | concentration of 3.6-4.4 g / L, and pH 4.5-4.7.

On the other hand, electroless plating has a uniform electrodeposition property and allows simultaneous plating in large quantities, and has good adhesion to non-conductive materials. In addition, it is excellent in heat resistance and solderability (solderability), can be plated on both metal and non-metal, high precision and there is an advantage that can solve the waste water treatment problem.

In general, the plating liquid having a large surface tension of the amphoteric group does not enter the groove well so that it is not easily degreased or plated, and the plating liquid is easy to bury. Therefore, degreasing and plating are good, and the amount of plating liquid is little. Therefore, it is preferable to use a surfactant (surfactant) during the plating process in order to lower the surface tension of the plating liquid.

The plating principle of the above-described Ni / Au plating is shown in the following scheme 2 and scheme 3.

Cu ⁰ + Pd ²⁺ -> Cu ²⁺ + Pd ⁰

Ni- (P) + Au ⁺ -> Ni ²⁺ + Au ⁰ : Substitution reaction

Here, Ni plating is performed to prevent mutual diffusion between the copper plating layer and the gold plating layer as shown in FIG.

Under this background of the prior art, the present invention provides an expensive metal catalyst (e.g., Pd) added to an insulating material during electroless metal plating (e.g., electroless copper plating and / or electroless gold plating) during a printed circuit board process. Instead, the photocatalytic technique using TiO ₂ sol is used instead. Pd metal catalysts are not only expensive, but many problems (ion migration, delamination) are expected in terms of product reliability when implementing microcircuits, and this problem is solved by introducing a photocatalyst.

Photocatalyst is a compound word of light [photo = light] + catalyst [catalyst] that uses light as an energy source to promote the catalytic reaction (chemical reaction; oxidation or reduction) to decompose various bacteria and pollutants It is a substance.

Photocatalysts have been actively researched in various fields since Fujishima and Honda announced in the early 1970s that when water was irradiated to TiO ₂ single crystal electrodes, water was separated into hydrogen and oxygen by photooxidation and photoreduction reactions.

In particular, as the photocatalyst, anatase or rutile crystalline TiO ₂ , in particular, anatase crystalline TiO _2, is used. The energy required to cause the photoexcitation reaction is about 387.5 nm (theoretical value) from sunlight. This is because they can receive sufficient energy, are chemically stable, have excellent photoactivity, and are excellent in physical properties such as being harmless to the human body. The TiO ₂ is a substance having a semiconductor characteristic in which electrons in the valence band are excited as conduction bands when energy corresponding to a short wavelength of 400 nm or less corresponding to an energy of 3.0 to 3.2 eV is irradiated. In particular, electrons and holes generated by irradiation of light move to the surface of TiO ₂ to cause redox reaction with the recombined or adsorbed material.

It is known that TiO ₂ having such characteristics can be applied to air purification, atmospheric purification, wastewater treatment, hydrophilic antifouling products, antibacterial products, durable UV protection products, and the like to obtain excellent performance. Further, when the coating of water on a surface treated substrate by using a TiO ₂ sol, the TiO ₂ due to the unique ultra-hydrophilic surface treatment effect due to the TiO ₂ sol becomes a contact angle of water molecules smaller eliminated condensation condensation It looks transparent, which is also a property that greatly improves wettability. In addition, since dirt or other contaminants, debris, etc. do not adhere to the substrate and are washed away with water droplets, dirty marks or contaminants do not remain on the surface even after drying.

In particular, TiO ₂ is chemically stable, has excellent photoactivity, and is inexpensive. Generally used TiO ₂ properties can be roughly divided into two as shown in Table 1 below. Among them, TiO ₂ sol has superior deodorization and antimicrobial properties compared to photocatalyst powders, which are widely used, and transparency is not only maintained but also easy to maintain even when coated on the surface of the air pollution prevention system and the insulating material of the printed circuit board. There is one advantage.

TiO ₂ Powder TiO ₂ Sol How to use Disperse in liquid and use as slurry Coated to substrate or used as sol itself Usage Antibacterial, Wastewater Treatment, Atmospheric Purification Fine coating, air pollution prevention system, deodorization, anti-fog, antibacterial system, sunscreen Advantages Easy to supply Maintain transparency after coating, easy to use and maintain, easy to supply, wide application range Disadvantages Reduced transparency (white coloration), binder required for coating on substrate, separation process required for use as slurry, corrosion of substrate when mixed with various materials -

Typical TiO ₂ photocatalysts include a hydrothermal method and a sol-gel method. Particularly, in the sol form, when the semiconductor particle size is very small below 10 nm due to the quantum size effect, the band gap is wider than the bulk state and the surface area / volume ratio is enlarged to increase the adsorption point. The diffusion distance between the electrons and holes is reduced to increase the efficiency of the photocatalytic reaction.

Therefore, the present inventors believe that the application of the above-described TiO ₂ sol to the plating process of the printed circuit board not only significantly improves the quality of the printed circuit board, but also that such a technology can be prepared for the global market as a next-generation core element technology. It was.

Advantages of using the TiO ₂ sol described above in the present invention is that a large specific surface area can be obtained to perform a sufficient photoreaction, in the case of using a conventional powder requires a secondary process to make a solution By using it as a sol itself, it can be applied as it is without the secondary process, and it can be distributed evenly when applied to the insulation of printed circuit board by evenly distributing it evenly in the solution without precipitation of particles by controlling the use condition appropriately. There is a characteristic.

In addition, in the present invention, in addition to the conventional anatase, rutile crystallization type may be used. Oxidation reaction of TiO ₂ and H ₂ O generates hydroxide radicals, and reduction reaction with O ₂ generates superoxide, and these products are photocatalysts. Plays an important role in the reaction. In addition, there is an advantage that less energy is used because the reaction occurs at room temperature in addition to the advantage that it can be utilized at atmospheric pressure without the generation of secondary by-products.

By utilizing the characteristics of the TiO ₂ sol as described above, in the present invention, the electroless metal plating of the printed circuit board is performed under specific conditions according to the following process.

First, a nano TiO ₂ sol solution having a pH of about 2 to 7 is coated on the surface of the substrate, and then ultraviolet rays are irradiated to form an activation layer.

The TiO ₂ coating film may be prepared by any method known in the art, such as a dip coating method using a sol gel method, a spin coating method, a CVD method using a vacuum apparatus, a sputtering method, and the like, but may be used. The sol-gel method is good.

The average particle diameter of TiO ₂ in the TiO ₂ sol solution used in the present invention is 5 to 60 nm, preferably 10 to 50 nm. When the average particle diameter of the TiO ₂ is less than 5 nm, it is difficult to manufacture economically disadvantageous, when it exceeds 60 nm there is a disadvantage that the transparency and light activity after coating is poor.

The concentration of TiO ₂ in the TiO ₂ sol solution is 0.05 to 0.5 mol%, preferably 0.1 to 0.4 mol%. When the concentration of TiO ₂ is less than 0.05 mol%, the transparency is excellent, but the thickness of the thin film is not only partially, the coating effect is inferior, resulting in a problem in reliability. When the concentration is more than 0.5 mol%, an opaque coating is also deteriorated. have.

The pH of the TiO ₂ sol solution is about 2-7, preferably about 3-6. If the pH of the TiO ₂ is less than 2, there is a disadvantage in that precipitation occurs due to a strong coagulation phenomenon, and when it exceeds 7, there is a disadvantage in that the dispersibility is excellent but the optical properties are relatively low.

The irradiation amount of the said ultraviolet-ray is 5-80mw / cm <2>, Preferably it is 10-70mw / cm <2>. If the irradiation amount of the ultraviolet rays is less than 5mw / ㎠ it has a disadvantage that the degree of activation falls and the catalyst phenomenon is sharply lowered. On the other hand, if it exceeds 80mw / cm 2, the polymer chain of the insulating material is broken, so that not only the deterioration of the material property but also brittle phenomenon occurs.

The ultraviolet irradiation time is preferably 5 to 30 minutes, the coating properties of the film is poor when out of the range there is a disadvantage that the optical properties are lowered.

On the other hand, the TiO ₂ sol solution to maintain a relatively small particle size to increase the light efficiency, in particular in order to increase the light efficiency of TiO ₂ in the visible light region at least selected from the group consisting of Cr, Fe, Ni, Nb and V One transition metal compound may be further added in ionic form.

According to one embodiment of the present invention, when V ⁵⁺ is added to the sol solution, fine particles having a size of several nm are present in a monodisperse form, indicating relatively low crystallinity. In addition, when transition metal ions such as Fe ³⁺ , Ni ²⁺ , and Nb ⁵⁺ are added, the zeta potential value is increased compared to the pure TiO ₂ sol solution, from which the sol solution is more stabilized as the metal ions are added. It can be seen that.

In addition, the change in the light absorption of TiO ₂ sol with the transition metal ion addition shows that the shift of light absorption into the visible wavelength region of longer wavelength than the light absorption region of pure TiO ₂ sol due to the addition of the transition metal compound The band gap energy corresponding to the longer wavelength is formed.

Here, the content of the transition metal compound is 0.05 to 0.5% by weight, preferably 0.1 to 0.3% by weight. When the content is less than 0.05% by weight, physical properties due to the addition of the transition metal may not be sufficiently expressed, and an optical characteristic improvement effect may not be obtained. On the other hand, when the content exceeds 0.5% by weight, the transition metal forms a complex, some of which exist in the form of ions, but some remain as a complex, causing precipitation and deteriorating optical properties.

The thickness of the activation layer formed as described above is preferably 0.05 to 0.8 mu m. If the thickness of the activation layer is less than 0.05㎛ has excellent disadvantages in transparency but coating properties and in part does not have optical properties. On the other hand, if it exceeds 0.8㎛ has a disadvantage in that the opacity is clear and the optical properties are relatively low.

Next, a conventional electroless metal plating solution comprising at least one metal salt, at least one reducing agent, and at least one organic acid is contacted on the active layer of the substrate to form an electroless metal plating layer. To form.

As the metal applied to the metal plating of the printed circuit board of the present invention, any metal capable of electroless plating may be used. Examples of metals that can be electroless plated include copper, nickel, cobalt, gold, silver, palladium, platinum, rhodium, iron, aluminum, tantalum, titanium nitride, titanium, tungsten, tantalum nitride, tungsten nitride, or combinations thereof. . Most preferred examples are copper or nickel / gold plated electrolessly.

According to the present invention, any printed circuit board capable of electroless metal plating or having at least a part of an electroless plated surface can be plated with metal according to the plating method of the present invention. Examples of surface materials suitable for electroless metal plating include aluminum, titanium nitride, tantalum nitride, tungsten, copper, silicon, cobalt, nickel, rhodium, palladium, or combinations thereof, as well as conventional insulating resins.

The plating method of the present invention is also particularly useful for plating metal onto the surface of electronic components, such as applying to fill interconnects (such as plugs and vias) and to form contacts between layers. Preferred applications include preplating copper to enable subsequent electroplating of copper.

As a preferred embodiment to which the plating method of the present invention as described above is applied, schematic process flows when applied to electroless copper plating and electroless Ni / Au plating are shown in FIGS. 5 and 6, respectively.

Here, it should be noted that in the case of the copper plating process, the photocatalytic technique in which the TiO ₂ sol is introduced instead of the activation process using the metal catalyst in the metal plating process of the prior art is enclosed by arrow marks in the copper plating process of the prior art shown in FIG. The process of the step (pre-dip / activation treatment / stage washing / reduction) can be replaced by one process of the TiO ₂ sol coating step. Similarly, in the case of the gold plating process, the three-step (soft-etching / pre-dip / activation treatment) enclosed by the arrow mark in the copper plating process of the prior art shown in FIG. 2 is replaced with one TiO ₂ sol coating step. By building a simpler process line there is an advantage that can maximize the production speed and efficiency.

In addition, the state in which the gold plated layer is formed on the printed circuit board according to the gold plating method according to an embodiment of the present invention is shown in FIG.

According to the present invention, the insulating material before the electroless plating (applied to the photocatalyst principle on the insulating material before the electroless plating or inside the via after laser processing (including the desmear)) and the gold plating treatment (applied to the photocatalyst principle to the gold-plated electric circuit) On top of the photocatalyst principle of the TiO ₂ sol can be applied to the Cu circuit after laser processing (including desmear) or before the gold plating treatment and subsequent processing can be developed. Through this, it is possible to implement a fine circuit having high adhesion and high reliability at low cost compared to the case of using a conventional Pd catalyst.

As described above, according to the present invention, the principle of TiO ₂ sol photocatalyst is applied to a printed circuit board metal plating process, and replaces the expensive Pd catalyst applied to the insulating material, especially during the electroless copper plating process, and also in the case of gold plating By replacing the catalyst has the advantage that can improve the production efficiency and quality at a low cost through a simple process line compared to the existing process.

In addition, due to the unique superhydrophilic effect of TiO ₂ photocatalyst, the adhesion of electroless metal plating can be improved, and the problem of reliability deterioration due to defects such as ion migration and delamination when solving micro circuits is solved. There is an advantage that it is possible to use a low profile insulating material.

In addition, it is expected that the problem of generating a large amount of waste water by using the existing process can be improved.

It is apparent that modifications and improvements of the present invention are possible by those skilled in the art within the technical spirit or protection scope of the present invention. Accordingly, the simple modifications and variations of the present invention are all within the scope of the present invention, and the specific scope of protection of the present invention will be clarified by the appended claims and their equivalents.

Claims (11)

In the plating method of a printed circuit board, (a) providing a TiO ₂ sol solution having a pH of 2 to 7 and having an average particle diameter of 5 to 60 nm; (b) coating the TiO ₂ sol solution on the surface of the substrate and then irradiating ultraviolet rays to form an activation layer; (c) providing an electroless metal plating solution comprising at least one metal salt, at least one reducing agent and at least one organic acid; And (d) contacting the metal plating solution on the activation layer of the substrate to form an electroless metal plating layer; Electroless plating method of a printed circuit board using a photocatalyst comprising a. The electroless plating of a printed circuit board using a photocatalyst according to claim 1, wherein the TiO ₂ sol solution further comprises at least one transition metal compound selected from the group consisting of Cr, Fe, Ni, Nb and V. Way. The electroless plating method of a printed circuit board using a photocatalyst according to claim 1 or 2, wherein the content of the transition metal compound in the TiO ₂ sol solution is 0.05 to 0.5% by weight. delete The electroless plating method of a printed circuit board using a photocatalyst according to claim 1, wherein the average particle diameter of TiO ₂ in the TiO ₂ sol solution is 10 to 50 nm. According to claim 1, wherein said TiO ₂ sol concentration of TiO ₂ in the solution are 0.05 to 0.5 The electroless plating method of a printed circuit board using a photocatalyst characterized in that the mol%. The method of claim 1, wherein the pH of the TiO ₂ sol solution is 3 to 6 electroless plating method of a printed circuit board using a photocatalyst. The electroless plating method of a printed circuit board using a photocatalyst according to claim 1, wherein the irradiation amount of ultraviolet rays is 5 to 80mw / cm 2. The electroless plating method of a printed circuit board using a photocatalyst according to claim 1, wherein the ultraviolet irradiation time is 5 to 30 minutes. The group of claim 1, wherein the metal is copper, nickel, cobalt, gold, silver, palladium, platinum, rhodium, iron, aluminum, tantalum, titanium nitride, titanium, tungsten, tantalum nitride, tungsten nitride, or a combination thereof. Electroless plating method of a printed circuit board using a photocatalyst, characterized in that selected from. The method of claim 1, wherein the thickness of the activation layer is 0.05 ~ 0.8㎛ electroless plating method of a printed circuit board using a photocatalyst.

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