KR20050028377A - Method of fabricating metal bus electrode of plasma display panel - Google Patents

Abstract

A method for manufacturing a metal bus electrode is provided to simplify manufacturing procedures and reduce manufacturing costs by forming a metal seed layer by electrodeless plating a black metal on the surface of the ITO electrode exposed between the patterned photosensitive resin layers. A method for manufacturing a metal bus electrode comprises a step of forming a metal seed layer(42) on a glass/ITO electrode substrate(41); a step of depositing a photosensitive resin layer on the metal seed layer; a step of patterning the photosensitive resin layer through exposure and development processes; a step of electroplating a metal electrode on the metal seed layer which is exposed between the patterned photosensitive resin layers; a step of removing the photosensitive resin layers; and a step of etching the metal seed layer. The metal seed layer is formed by an electrodeless plating process.

Description

Metal bus electrode manufacturing method of plasma display panel {METHOD OF FABRICATING METAL BUS ELECTRODE OF PLASMA DISPLAY PANEL}

The present invention relates to a method for manufacturing a metal bus electrode of a plasma display panel by an electroplating method, and more particularly, to a method capable of reducing manufacturing costs by forming a metal seed layer by an electroless plating method.

Plasma display panel is a device that obtains the desired number, letter or picture by coating a plurality of electrodes on each of two substrates, filling the gas between both substrates, sealing them, and then applying a discharge voltage to excite the phosphor formed in a predetermined pattern. Say. In such a plasma display panel, a bus electrode is formed to have a narrower width than that of the ITO electrode in order to reduce the line resistance of the transparent ITO electrode.

As a conventional bus electrode manufacturing method, a vapor deposition method, a screen printing method and an electroplating method are known.

1 shows a process schematic diagram of a method for manufacturing a bus electrode by a conventional vapor deposition method. As shown in FIG. 1A, the metal seed layer 12 is deposited on the glass / ITO electrode surface 11 by vacuum deposition to improve adhesion between the ITO surface and the metal electrode. In this case, when the metal seed layer 12 is not black, the contrast of the image is reduced by reflecting light, so that the color of the metal seed layer 12 is blacked to enhance the contrast of the image. Then, the metal electrode layer 13 is deposited by evaporation as shown in FIG. 1 (b), and then the photosensitive resin layer 14 is coated on the metal electrode layer 13 as shown in FIG. To form a pattern. Next, as shown in FIG. 1 (d), the metal bus electrode is formed by removing the unnecessary metal electrode layer and the metal seed layer through the etching process and removing the photosensitive resin. While this method has the advantage of producing an electrode having a very small width, the deposition rate of the metal electrode is very slow and the residual stress is high on the formed electrode, which is likely to cause edge curl, and the process cost is high. There are disadvantages. In addition, since the metal electrode layer of several micrometers must be etched, there is a problem that the loss is high and the defect rate is high.

2 shows a process schematic diagram of a method for producing a bus electrode by a conventional screen printing method. After the printing mask 22 is mounted on the glass / ITO electrode surface 21 as shown in FIG. 2 (a), and the metal paste 23 is applied on the top thereof as shown in FIG. 2 (b). Remove the print mask. Thereafter, the metal paste is baked at a specific temperature at 500 to 600 ° C. to form the metal bus electrode 24 (FIG. 2C). The screen printing method currently used in forming bus electrodes at home and abroad is a photo process method. The silver paste containing photosensitive material is printed on a glass / ITO electrode, dried, and exposed using a photo process, followed by exposure to Na _2. Development is performed with an aqueous Co ₃ solution, followed by firing to form a thick film. In addition, before printing silver paste, black pigment whose main ingredient is ruthenium oxide, which also contains photosensitive material, is printed thinly between silver paste and glass / ITO electrode to absorb light from the outside after panel manufacturing to improve color contrast. Let's do it. This method is relatively simpler than the deposition method, while the paste pattern shrinks during the high temperature sintering process, resulting in different print mask pattern and metal bus electrode size, and improved paste formation and adhesion to glass / ITO electrode. There is a problem that the specific resistance is increased by the additives added for the purpose, and the minimum size of the bus electrode that can be formed is limited to about 80 μm, and there is a problem that silver paste sold in commercialization is expensive.

3 shows a process schematic diagram of a method for producing a bus electrode by a conventional electroplating method. As shown in FIG. 3A, a first metal seed layer 32 and a second metal seed layer 33 are deposited on the glass / ITO electrode 310 by sputtering. At this time, the first metal seed layer 32 is formed of Cr or Ti or their alloys and oxides to improve adhesion to the glass / ITO electrode 31, and the second metal seed layer 33 is formed of the first metal seed layer. It is formed of Cu or the like to lower the high resistance value of (32). Thereafter, as shown in FIG. 3B, the photosensitive resin 34 is applied to the upper portion of the metal seed layer, and exposed and developed to pattern the metal electrode. Thereafter, after forming the metal bus electrode 35 by electroplating (FIG. 3C), the patterned photosensitive resin 34 is removed as shown in FIG. 3D, and the metal is etched through the etching process. The seed layers 32 and 33 are removed leaving only pure metal bus electrodes 34. Compared with the sputtering method, the residual stress of the formed electrode is relatively small, which can reduce the occurrence of edge curl, and unlike the screen printing method, since the bus electrode is generated and grown inside the photosensitive resin pattern, which is almost unlimited in the size of the line width, the undercut Since no under cut occurs and no paste is used as in the screen printing method, the firing process at 500 to 600 ° C. is unnecessary. However, the deposition apparatus cost increases by using sputtering, ion plating or electron beam deposition in the manufacture of the metal seed layers 32 and 33.

The technical problem to be achieved by the present invention is to simplify the etching process by directly electroless plating a black metal on the surface of the ITO electrode exposed between the patterned photosensitive resin to produce a single metal seed layer having a thickness of 1 μm or less. The present invention provides a bus electrode manufacturing method of a plasma display panel which can reduce cost and processing time.

In order to achieve the above object, the present invention comprises the steps of forming a black metal seed layer on the glass / ITO electrode substrate; Applying a photosensitive resin layer on the metal seed layer; Exposing and developing the photosensitive resin layer to pattern it; Electroplating a metal electrode over the metal seed layer exposed between the patterned photosensitive resin layer; Removing the photosensitive resin layer; And etching the metal seed layer, wherein the metal seed layer is formed by an electroless plating method. The process schematic of this manufacturing method according to the present invention is shown in FIG. 4.

According to a feature of the present invention, as shown in FIG. 4A, a black metal seed layer 42 is formed on the entire surface of the glass / ITO electrode substrate 41 through an electroless plating process. The reason for forming the metal seed layer is that the ITO electrode (transparent electrode) is generally 800-1000 mW when used for a plasma display panel, the electrical conductivity of which is less than that of pure metal, and a large surface resistance of 20-30 Ω / m ² . This is because electroplating is not easy.

In this case, unlike the manufacturing method of the bus electrode by the conventional electroplating method shown in Fig. 3, it is advantageous in terms of cost because no expensive deposition apparatus is required to form the metal seed layer. In addition, in the case of forming the metal seed layer by the electroless plating method, the metal seed layer having a thickness of 1 μm or less can be precisely formed directly on the glass / ITO electrode surface, so that the metal seed layer is easily removed at the final stage of the process. Can be performed.

The metal seed layer 42 advantageously has a black color to enhance the contrast of the plasma display, and the sheet resistance will be sufficiently smaller than glass / ITO so that the bus electrode can be electroplated thereon in a subsequent process step. Required. According to a feature of the present invention for achieving this, the plating liquid used in the electroless plating of the metal seed layer is 0.05 ~ 0.5 mol / l sodium hypophosphite as a reducing agent and as a black electroless metal material 0.05 to 0.5 mol / l nickel sulfate, at least one of 0.01 to 0.5 mol / l malic acid and citric acid as a complexing agent, and 0.00005 to 0.0005 mol / l as a stabilizer It is preferred to consist of lead acetate, zinc sulfate of 0.05 to 0.5 mol / l as a source of zinc, and ammonium sulfate of 0.0001 to 0.0005 mol / l as a source of sulfur. In addition, according to another feature of the invention, the plating solution is preferably pH 6-12, temperature 70 ~ 90 ℃.

When the composition, pH and temperature of each component of the plating liquid are outside the above ranges, the plating liquid is unstable or electroless plating itself is not performed properly, and even if the plating layer is formed, it does not have a black color necessary for image contrast.

The plating layer formed by the electroless plating method from the plating liquid having the above composition is a black nickel plating layer containing several percent zinc. Plated layer of a nickel alloy containing such zinc is direct electroplating over the metal seed layer of the single layer, without the presence of a second metal oxide layer to a sheet resistance of only several tens of Ω / m ² of glass / ITO electrode can Ω / m ² compared to It is possible to form a bus electrode by carrying out.

According to another feature of the invention, the electroless plating method is preferably performed for 4 to 8 minutes. In general, the metal seed layer has a thickness of about 1 μm as a seed layer for electroplating. The reason for limiting the plating time to 4 minutes is to ensure the thickness of the required seed layer. On the other hand, the reason why the upper limit of the plating time is limited to 8 minutes is to prevent the thickness of the seed layer from becoming excessively thick.

In the next step, as shown in FIG. 4B, the photosensitive resin layer 43 is applied on the metal seed layer 42 and only the position where the metal bus electrode is to be formed on the ITO electrode through exposure and development. Pattern to remove.

Subsequently, as shown in FIG. 4C, a metal bus electrode 43 having a predetermined thickness is formed into the portion from which the photosensitive resin is removed by electroplating. Next, the patterned photosensitive resin is removed, and only the final metal bus electrode 43 is left by removing the metal seed layer 42 at the portion where the metal bus electrode 43 is not formed (FIG. 4D). ).

According to another feature of the invention, the step of etching the metal seed layer, an etching solution consisting of 5 to 10% sulfuric acid, 3 to 5% hydrogen peroxide, 0.4% ferrous sulfate and 0.2% ferric sulfate It is preferably carried out using. If the component of the reagent is smaller than the above composition, the etching rate is too slow and, conversely, if the component is large, the metal bus electrode is etched together with the metal seed layer.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention.

(Example 1)

Degreasing ITO-coated glass for commercial plasma displays (sodium hydroxide 0.5 mol / l, 70 ° C, 10 minutes)-> washing with water-> etching (200 ml / l nitric acid, 100 ml / l hydrofluoric acid, room temperature, 20 seconds)-> washing water- > Neutralization (sodium hydroxide, 50 ° C, 30 seconds)-> Catalysis (Palladium chloride 0.002 mol / l, Tin chloride 0.111 mol / l, Hydrochloric acid 200ml / l, Room temperature, 3 minutes)-> Wash and pre-dry Was performed.

Nickel sulfate 0.1 mo./l, sodium hypophosphite 0.2 mol / l, malic acid 0.5 mol / l, citric acid 0.05 mol / l, zinc sulfate 0.05 mol / l, ammonium sulfate 0.0005 mol / l and lead acetate 0.0005 mol / l A metal seed layer was formed using an electroless plating solution consisting of At this time, the pH of the plating liquid was maintained at 10, the temperature was 80 ℃, the plating time was 4 minutes and 8 minutes.

In this way, a black metal seed layer was obtained. The cross section was confirmed by SEM, and the thickness was 0.7 µm and 1 µm, respectively, and the adhesion to the surface of the ITO electrode was good. The metal seed layer was removed by etching within 20 seconds using an etching solution consisting of 5-10% sulfuric acid, 3-5% hydrogen peroxide solution, 0.4% ferrous sulfate and 0.2% ferric sulfate.

The second specimen of Figure 5 is a photograph of the metal seed layer obtained by electroless plating according to the present embodiment, it was confirmed that the metal seed layer is black. The third specimen from the top of Figure 5 was obtained by obtaining a black metal seed layer and then electroplated on it to confirm that a uniform plating layer was obtained. In contrast, the first specimen of FIG. 5 was electroplated directly onto ITO / glass and was not uniformly plated.

(Example 2)

Under the same conditions as in Example 1, only the plating time was changed to 2 minutes to form a metal seed layer. A black metal seed layer was obtained, but the cross section was confirmed by SEM, and the thickness was not uniform with 0 to 0.6 mu m.

(Example 3)

Under the same conditions as in Example 1, only the plating time was changed to 12 minutes to form a metal seed layer. The black metal seed layer having a thickness of 1.3 μm was obtained, but adhesion with the ITO electrode was poor due to the increase in residual stress caused by the increase in thickness.

(Example 4)

Under the same conditions as in Example 1, when zinc sulfate and ammonium sulfate were not present in the components of the plating solution, that is, nickel sulfate 0.1 mo./l, sodium hypophosphite 0.2 mol / l, malic acid 0.5 mol / l, citric acid 0.05 mol / l And in the case of a plating solution composed of lead acetate 0.0005 mol / l, a black metal seed layer could not be obtained.

According to the method of manufacturing a bus electrode of a plasma display panel according to the present invention, a black metal is formed on an ITO electrode surface exposed between patterned photosensitive resins without using a deposition method used for forming a metal seed layer in a conventional electroplating method. By directly electroless plating to produce a single metal seed layer having a thickness of 1㎛ or less, there is no need to use a deposition apparatus, and the etching process is very simple, which is advantageous in terms of cost and shortens the processing time.

BRIEF DESCRIPTION OF THE DRAWINGS The process schematic of the manufacturing method of the bus electrode by the conventional vapor deposition method.

2 is a process schematic diagram of a method for producing a bus electrode by a conventional screen printing method.

3 is a process schematic diagram of a method for manufacturing a bus electrode by a conventional electroplating method.

4 is a process schematic diagram of a method for producing a bus electrode by the electroplating method according to the present invention.

5 shows a specimen (first specimen) electroplated directly onto ITO / glass, a specimen (second specimen) having a black metal seed layer obtained by electroless plating according to this embodiment, and the black metal seed layer. Photographs of each of the specimens (third specimen) electroplated thereon after obtaining.

Claims (5)

Forming a metal seed layer over the glass / ITO electrode substrate; Applying a photosensitive resin layer on the metal seed layer; Exposing and developing the photosensitive resin layer to pattern it; Electroplating a metal electrode on the metal seed layer exposed between the patterned photosensitive resin layer; Removing the photosensitive resin layer; In the manufacturing method of the bus electrode of the plasma display panel by the electroplating method comprising etching the metal seed layer, And the metal seed layer is formed by an electroless plating method. The method of claim 1, Forming a metal seed layer by the electroless plating method, 0.05 to 0.5 mol / l sodium hypophosphite as reducing agent, 0.05 to 0.5 mol / l nickel sulfate as black electroless metal material, and 0.01 to 0.5 mol / l malic acid as complexing agent at least one of malic acid and citric acid, 0.00005 to 0.0005 mol / l lead acetate as a stabilizer, and 0.05 to 0.5 mol / l zinc sulfate as a source of zinc. And a plating solution composed of 0.0001 to 0.0005 mol / l ammonium sulfate as a source of sulfur. The method of claim 2, The plating solution is a pH 6 ~ 12, the temperature 70 ~ 90 ℃ the manufacturing method of the metal bus electrode of the plasma display panel. The method according to any one of claims 1 to 3, The electroless plating method is a method for manufacturing a metal bus electrode of the plasma display panel, characterized in that performed for 4 to 8 minutes. The method of claim 1, The etching of the metal seed layer may be performed using an etching solution including 5 to 10% sulfuric acid, 3 to 5% hydrogen peroxide, 0.4% ferrous sulfate, and 0.2% ferric sulfate. Method for manufacturing a metal bus electrode of a display panel.