TW548342B - Method for selective plating of metal - Google Patents

Abstract

A method for selective plating of metal on the surface of an article by forming a wet film on the region where a metal layer is undesirable, comprises: providing a substrate which can be an article such as a PCB which is desired to receive a partial plating of a metal; providing an ink; using a scraper and a screen to coat by screen printing the ink on a region of the substrate where a metal is to be plated thereon in order to form a photosensitive wet film on the substrate; using a negative exposure technique to transfer a pattern on the wet film; developing the wet film to expose the region on the substrate where a metal is to be plated thereon; forming a metal on the substrate; and removing the wet film to obtain a selectively plated metal.

Description

548342 V. Description of the invention (1) Field of the invention: The present invention relates to a process of electro-mineral metal, and particularly relates to a method for forming a wet film by applying screen printing technology, and thereby improving the penetration condition during metal plating. Background of the Invention: In the ultra-large-scale integrated circuit (ULSI) trend, the size of semiconductor components is continuously shrinking to continuously increase the accumulation of components on wafers. With the reduction in the size of electronic components, many new challenges have arisen in the manufacturing process of integrated circuits. In addition, due to the rapid development of computer and communication technology, there is a need for more and more electronic components of different types and applications. For example, computer interfaces operated by voice or other communication interfaces require many memory components and different types of semiconductor components. Therefore, the trend of integrated circuits will still develop toward a high integration degree. In recent years, the development stage of high-density semiconductor elements has already entered the technical range of sub-micron (s u b m i c r ο η) and even deep sub-micron. In addition, with the rapid evolution of semiconductor technology, driven by the trend of light, thin, short, and multi-functional speeds, the number of I / 0 of IC semiconductors is not only increasing, but also increasing in density. The number of feet is increasing, and the speed requirements are getting faster and faster. In response to this trend, packages have also become smaller and smaller to meet requirements, and flip-chip packages have been developed.

Page 4 548342 V. Description of the invention (2)-(F 1 i P c h i p), wafer-level package and high-quantity I / 〇 package, ball matrix array packaging technology (bal 1 grid array; bgA package for short). As for the circuit board that communicates with and carries the chip, it is bound to improve its own manufacturing method with the development of these technologies. For example, a chip with more functions and more powerful computing power requires more contacts and more complicated circuit layout. On the front panel. One is plated in the shadow-dried circuit. Focus on the use In the case of the country, it is necessary to make a circuit with a higher density and a narrower line width. This is a challenge of current circuit board manufacturing technology, and the difficulty that will be encountered is the problem of penetration during metal plating. As shown, in the conventional technique, when metal is used, "a dry film is first coated on the circuit board 100, and the exposure is shown as a film to form a pattern of the area to be plated." Remove the dry film. The metal part 120 in Figure 1 is the cause of infiltration. There are many reasons, including the attachment between the dry film and the circuit board, and the metal material to be plated. At present, the most commonly used solution is a thicker dry film, and such dry films generally rely on imports. As a result, the cost for domestic manufacturers has increased significantly. In addition, the solution to the above-mentioned problem has also been proposed, which uses ink as the basis and uses coating to form a wet film on a circuit board. , The method is produced by curtain coater, which can solve the problem of plating. However, this method is more complicated and complicated in terms of manufacturing process, and its cost is not lower than that of the dry film with a thickness of f, and the relevant equipment used is also relatively low. Therefore, although the problem of infiltration is solved, it is not available in the market.

548342 V. Description of invention (3) Competitive. The present invention provides another method with industrial competitive advantages to replace the traditional method. Objects and Summary of the Invention: In view of the lack of the prior art, the main object of the present invention is to provide a method that can improve the occurrence of infiltration during selective metal plating, and save manufacturing costs. The invention utilizes screen printing method, and uses screen printing ink to form a wet film on the surface of the article by using a doctor blade and a screen plate. There is no technical difficulty in the manufacturing process, and the cost of the equipment used is also low. The present invention provides a method for selective metal plating, by forming a wet film on an area where a metal layer is not to be formed, so that the surface of an article can be selectively plated with metal. The aforementioned method includes at least the following steps: providing a substrate, which can be an article such as a printed circuit board to be partially plated with metal, providing an ink, and forming a wet film on the substrate by screen printing. The film is light sensitive, and the pattern can be transferred to a wet film by negative film exposure technology, and then the wet film is hardened. Then, the wet film is exposed, and then the wet film is developed. After the wet film is developed, the areas on the substrate to be plated with metal are exposed. After that, a metal is formed on the substrate to be plated with metal. Finally, the wet film is removed to obtain selective metal plating.

Page 6 548342 V. Description of the invention (4) Detailed description of the invention: The present invention discloses a problem related to improving the penetration of the conventional technology in selective metal plating. Different from the conventional method of forming a dry film on the surface of the article, the present invention utilizes screen printing technology used in other processes to make the screen printing ink form a wet film on the surface of the article through the screen. By adjusting the composition of the ink, the formed wet film has an excellent performance in preventing the occurrence of penetration. The transfer of screen printing technology to the process of the present invention can not only overcome the difficulties encountered by the previous technology, but also reduce the cost. The detailed description of the present invention is as follows. The preferred embodiment is described only for the purpose of not limiting the present invention. As shown in FIG. 2, a substrate 200 is provided. The substrate 2000 is not limited in material. It can be a printed circuit board that has been coated with solder resist, such as a circuit board used in a mobile phone. It may be other articles to be plated with metal in a specific area of the surface part. Next, a wet film 2 2 0 is formed on the substrate 2 0 by screen printing. The wet film 2 2 0 is light sensitive. The above-mentioned screen printing method is, for example, scraping through a mesh with a doctor blade, so that the ink passes through the opening of the screen and covers the substrate 200, and finally forms a wet film 220. In addition, the arrangement and size of the screen openings described above correspond to the arrangement and size of the area where the metal is to be formed. Before using the ink, you need to stir the ink, and then let the ink stand. Of course

Page 7 548342 V. Description of the invention (5) After coating the ink on a substrate 200 with a doctor blade and a screen, the ink is dried in the shade to form a wet film 2 2 0. The above-mentioned ink contains a defoamer with a composition of 2% to 3%. This is added to avoid the occurrence of air bubbles when the ink is stirred in the ink tank and when it is printed. The above stirring time of the ink lasts about 5 ~ j0 minutes. The ink is left to stand for about 20 to 30 minutes. The temperature of this ink can be kept at room temperature or below 4 ° C, and the time is about 丨 0 to 15 minutes. For a preferred embodiment, the OPTO-ER N company from Nipp On can be used. For -40 0G (H) type inks, the required wet film viscosity is about 80 ~ 90 poise, and various stencils can be used. On the other hand, in order to increase the viscosity of the wet film 2 2 0, it can be improved by The solid content in the ink is achieved. After this' harden this wet film 2 2 0, this step can be heated and baked in a way that the temperature of baking and hardening is about i 0 (rc for 丨 0 minutes, provided by thermal energy , Can remove part of the solvent, while making the structure of the wet film 22 ° more dense. Please refer to Figure 3, “Resin similar to the integrated volume defiance ~ Photoresistance used in the wide μ process, 3 = 2 = jHtolithography) film formation The molecular structure of 220 is changed. However, according to the difference between the light and the light, the wet developing solution is caused, so that part of the liquid is dissolved on the surface of the substrate 2 with the wet film 22, and the process is 2 2 0. It can be used to expose the metal to be bonded, which can use a photomask or a negative film field as follows: f First, expose this wet film 22〇 , Move to the wet film 22 0. Then /, the first way ..., the pattern to be formed is transferred to a developing solution to etch the wet film 2 2 0 ^ = the exposed wet film 2 2 0, which uses a substrate After the formation of metal on 2 0 0, the residual wet film 2 3 0 is left uncovered and exposed to prevent the generation of the prior art product or 2 1 0 2 full residual film 2 3 0 can be used to show the phenomenon of penetration plating .

548342 V. Description of the invention (6) Please refer to FIG. 4 to form metal 24o on top of metal 21o to be plated. The fI mentioned above are: chemical tin, chemical silver, chemical nickel gold, hard gold plating, soft gold plating. The thickness of the nickel composition of chemical nickel-gold is about 100 ~ 200 microns and ^ β), and the thickness of the gold composition is about 2 ~ 5 microns (//). Finally, the wet film 23 (not shown) is removed. As mentioned above, the wet film is removed, and it is stripped away by etching with sodium hydroxide (NaOH) solution. The method of forming the metal 24 onto the gold to be plated ^ 0 can be electroplating, or electroless plating can be used, depending on the metal formed by the 4 people. For example, if soldering contact 2 is to be formed, it can be completed by screen printing and applying solder paste; while removing the wet film 2320, the composition of the film 230 is different. In the present invention, a sodium hydroxide solution is used. Finally, an organic protective layer is formed on the metal surface of the unplated metal 240 to prevent the metal layer from oxidizing due to contact with air. Entek is a thin film with a main component of BTA. The main point of selection is that it does not deposit metal layers. η The most commonly used circuit boards used are chemically nickel-gold-plated gold to nickel-gold nickel. The thickness of the nickel composition is about 100 to 200 microns. The thickness of the gold composition of the telephone is about 2 to 5 microns (" ). Action Where the buttons on the surface of the abrasion-resistant and rugged board belong to the keys, for better t-scratching properties, electroless nickel gold plating will be selected, which is prone to infiltration. Avoid the use of dry film in the past. Another example is Muli, which is a high-end product that responds to chip size packaging (Chip scale 548342 V. Invention description (7) p a c k a g e). Soft gold keying on printed circuit boards has become a key process. It is difficult to avoid penetration through the use of various processes and dry films. The thickness of the nickel component when the soft gold is plated in the present invention is 200 // π or more, and the thickness of the gold component is between 20 and 40%. Nickel gold is much thicker and performs well in the case of avoiding ore infiltration. The invention forms a wet film by screen printing, which reduces the cost a lot and is very competitive in the market. At the same time, it also solves the problem of penetration plating, and because of the process familiarity of screen printing technology, it has good applicability in the process. For those skilled in the art, although the present invention is explained above with a preferred example, it is not intended to limit the spirit of the present invention. Modifications and similar arrangements made without departing from the spirit and scope of the present invention should be included in the scope of the patent application described below, and such scope should be consistent with the broadest evidence covering all modifications and similar structures. Therefore, a preferred embodiment of the present invention as explained above can be used to identify various changes made without departing from the spirit and scope of the present invention.

Page 10 548342 Brief description of the drawings Brief description of the drawings: Figure 1 shows a cross-sectional view showing conventional techniques on electroplated metal on a circuit board. Fig. 2 is a schematic diagram showing the formation of a wet film on an article using screen printing technology according to the present invention. Fig. 3 is a sectional view showing a pattern formed by exposure and development on a wet film according to the present invention. FIG. 4 is a cross-sectional view showing a metal formed on an article according to the present invention. Symbol comparison table:. Substrate 1 0 0 Metal 110 Metal plated 1 2 0 Substrate 200 Area to be plated 2 1 0 Wet film 2 2 0, 2 3 0 Metal 240

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Claims (1)

548342 I VI. Scope of patent application I j 4. A method for selective metal plating as described in item 1 of the scope of patent application, wherein the ink contains a defoamer with a composition of 2% to 3%. 5. A method for selective metal plating as described in item 1 of the scope of patent application, wherein the ink is agitated for 5 to 10 minutes. 6. A method for selective metal plating according to item 1 of the scope of patent application, wherein said ink is left to stand for 20 to 30 minutes. 7. A method for selective metal plating according to item 1 of the scope of patent application, wherein the ink is dried at room temperature for 10 to 15 minutes. j 8. A method for selective metal plating as described in item 1 of the scope of patent application, wherein the ink is dried at a temperature of 40 ° C or lower for a period of 10 to 15 minutes. 9. A method for selective metal plating according to item 1 of the scope of patent application, wherein the method further comprises forming an organic solder protection layer on the surface of the metal layer after removing the wet film, in order to prevent the metal layer from being exposed to air. Oxidation upon contact. 10. The method for selective metal plating according to item 1 of the scope of patent application, wherein the substrate described in i 丨 includes a printed circuit board. Page 13 548342 VI. Scope of patent application 1 1. A method for selective metal plating as described in item 1 of the scope of patent application, wherein the substrate includes a circuit board used in a mobile phone. Fan Li specially asked Zhongruo to belong to Jin Chengxing. Above and below, the material method should be based on the gold-nickel-nickel bond properties of selective plating. Select the metal that contains the upper layer of the item 1 and the bottom thickness of the material. Gold = Gold # plating 00 2 'ο ο 1% Ni Fan Fan Li asked Zhongru Gold and Nickel to learn about the chemical ~ ~ 2 in its degree ^ Fan Fan Li Zhu Zhong should be described in the gold forming statement. The upper part of the French material belongs to the gold and tin plating, and the selective plating option contains the first package. The upper part of the upper part of the material, Fan Li, please apply for it to belong to the gold formation institute. The upper part of the French material belongs to the gold and silver mineralization selective plating and selective seed package 1? The upper part of the item 1 and the lower part of the range. Fan Li, please refer to it as described in Jin Chengxing. The material of the above method belongs to the gold-gold-plated soft plating selective plating method, including the above-mentioned items, the first item, the bottom item, and the bottom item. As a selective metal plating method in item 16 of the scope of patent application, In the electroplating soft gold, the thickness of the nickel component is more than 200 / ζ π, and the thickness of the gold component is between 20 and 40 μ π. Page 14 548342 VI. Scope of Patent Application 18. A method for selective metal plating as described in item 1 of the scope of patent application, wherein the metal is formed on the substrate, including hard gold plating on the substrate. 19. A method for selective metal plating as described in item 1 of the scope of patent application, wherein said removing the wet film can be stripped away by etching with a sodium hydroxide (NaOΗ) solution. 20 A selective metal plating method, wherein the wet film can be hardened by heating and baking. Page 15