JP3425139B2 - Selective metal plating method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a selective electrometal plating method, and more particularly, to a selective metal plating method performed by forming a wet film using a screen printing technique.

[0002]

2. Description of the Related Art Today's integrated circuits are in the trend toward ultra large scale integrated circuits (ULSI), and semiconductor devices are constantly shrinking in size, while the integration density of devices on a wafer is becoming higher and higher. . As the size of the electronic device is reduced, many problems occur in the manufacturing process of the integrated circuit, which poses a technical challenge.
Also, with the rapid development of computers and communication technology, more electronic devices of different types and their applications are required. For example, a voice-operated computer interface or other communication interface requires a large number of storage elements and different types of semiconductor elements. As a result, integrated circuits are developing toward ever higher integration densities. In particular, in the last few years, high-density semiconductor devices have advanced to the sub-micron region, and are now approaching the deep sub-micron technical range.

The number of I / Os in semiconductor integrated circuits is increasing due to the rapid development of semiconductor technology and the trend toward lighter, thinner, shorter, smaller, more diversified functions and higher speed of electronic products. As it becomes denser and denser, the number of pins of the device for packaging is also increasing, and the demand for speed is also increasing. To meet this trend, packages are becoming smaller and smaller. Therefore, for example, technologies such as a flip chip, a chip scale package, a large-scale I / O package, or a ball grid array have been developed. Further, with respect to a wiring board on which wiring and an IC chip are mounted, the manufacturing method of the wiring board itself has been improved with the development of the above-mentioned technology. Therefore, a wiring board having a chip having more functions and a stronger calculation function and capable of handling a complicated circuit having more contacts has been developed.

Under the above circumstances, there is a need for a board having a high density and a narrower line width. This is currently a technical goal in making wiring boards. The most difficult point among them is the problem of plating penetration that occurs during metal plating. As shown in the drawings, when metal plating is performed by a known technique, a dry film (1) is formed and covered on a wiring board (200). Then, a pattern is formed on the dry film (1) in the metal plating region by exposure and development. Further, a plated metal (8) is formed on the wiring board (200), and finally the dry film (1) is removed. The area indicated by a dotted line in the drawing is the plated-in portion. There are many causes of such penetration of plating, and include, for example, the degree of adhesion between the dry film (1) and the wiring board (200), the characteristics of the metal material to be plated, and the like. The method currently used to solve such problems is to use a relatively thick dry film. However, such a thick dry film has a very high cost, which greatly affects the cost of the entire product.

As another method for solving the above-mentioned problems, there is a method of forming a wet film on a wiring board by coating using oil-based ink as a raw material. This method is manufactured by applying curtain coating. This can solve the problem of plating penetration. However, the manufacturing process of such a method is complicated, and the cost is not lower than the method using a thick dry film. In addition, the associated equipment used in such a scheme is also very expensive and thus can solve the above mentioned problems, but its products do not offer any competitiveness in the market in terms of cost.

[0006]

SUMMARY OF THE INVENTION Therefore, in view of the above-mentioned drawbacks of the prior art, an object of the present invention is to prevent the penetration of plating that occurs when metal plating is selectively applied to a wiring board. It is to provide a selective metal plating method that can be effectively prevented.

Another object of the present invention is to provide a selective metal plating method which does not complicate the manufacturing process and can be carried out at low cost without using various related equipment.

[0008]

In view of the above circumstances, the present inventor has conducted extensive studies to solve the above problems, and found that the above problems can be achieved by using screen printing technology. The present invention has been made based on these findings.

That is, according to the present invention, in the selective metal plating method, a screen printing method is applied on a base material to form a wet film having photosensitivity, and a step of curing the wet film. A step of exposing the cured wet film, a step of developing the wet film to expose an area for forming a metal layer on a base material, and a step of forming a metal layer on the base material, And a step of removing an excess wet film, the selective metal plating method.

The present invention will be specifically described below. The selective metal plating method according to the present invention comprises applying a screen printing method on a base material to form a wet film having photosensitivity, curing the wet film, and curing the wet film. A step of exposing the film, a step of developing the wet film to expose an area for forming a metal layer on the base material, a step of forming the metal layer on the base material, and removing an excess wet film And the step of performing.

In the screen printing method, a step of stirring an oil-based ink that is a material for forming the wet film, a step of holding the stirred oil-based ink in a stationary state, and an oil-based method using a trowel and a mesh are used. The method includes the steps of applying ink to the base material, and naturally drying the oil-based ink applied to the base material to form the wet film.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention applies a screen printing technique to a selective metal plating method. That is, the selective metal plating method according to the present invention comprises a step of forming a wet film having photosensitivity on a base material,
Curing the wet film, exposing the cured wet film, developing the wet film to expose an area for forming a metal layer on the base material, and exposing the base material on the base material. The method includes a step of forming a metal layer and a step of removing an excess wet film, and in order to describe the features of the selective metal plating method in detail, specific examples are given and refer to the drawings. And will be described below.

[0013]

EXAMPLES Example 1 FIG. 2 is an explanatory diagram in the case of applying a screen printing technique to form a wet film. FIG. 3 is a sectional view of a pattern formed on the wet film in FIG. FIG. 4 is a sectional view of a metal layer formed by applying the present invention. FIG. 5 is a flow chart showing the steps for carrying out the present invention.

The selective metal plating method according to the present invention comprises:
As disclosed in FIG. 2, first, a base material (100) is prepared. The base material (100) may be any material, such as a print boat coated with an anti-fusing liquid,
It may also be any article that is metal plated on a particular area of the surface.

Next, by applying the screen printing method,
A wet film is formed on the base material. The wet film has photosensitivity and, for example, in a manufacturing process of an integrated circuit, different molecular structures are changed due to difference in energy irradiated like a photoresist used. Further, when a developing solution is used, it dissolves in the developing solution, so that it can be easily removed and the surface of the base material to be electroplated can be exposed.

As shown in FIG. 2, coating is carried out by rubbing the mesh (4) with the trowel (2) so that the oil-based ink passes through the mesh and uniformly coats the base material (100). . The oil-based ink is selected to contain a defoaming agent in a ratio of 2% to 3%. This is to add the oil-based ink so as not to generate bubbles when the oil-based ink is stirred in the ink bucket and during printing.

Next, the oil-based ink to be the coating layer is dried to obtain the wet film (6). In this case, the oil-based ink is stirred in advance and then kept stationary. The stirring time is about 5 to 10 minutes, and the stirring time is about 20 to 30 minutes. The oil-based ink is dried at room temperature or at 40 ° C. or lower for 10 to 15 minutes.

The viscosity of the wet film (6) can be enhanced by increasing the content of the solid component of the oil-based ink. Therefore, OPTO-ER N400G (H) may be used as a product of Nippon Paint Co., Ltd. as a preferable example of the oil-based ink.

Next, the wet film (6) is cured. This step is performed by an indirect heating method (Baking), and by applying heat energy, a part of the moisture can be removed, and at the same time, the structure of the wet film (6) can be made closer.

In FIG. 3, the wet film (6) is exposed. In this case, a predetermined pattern is formed on the wet film (6) by using a photomask or exposing with a negative. Then, development is performed by erosion with a developing solution. By this process, the base material (10
0) Exposing the area where the metal layer is to be formed.

Next, as shown in FIG. 4, a metal layer (8) is formed on the base material (100), and finally the wet film (6) is removed (this state is not shown).

The method of forming the metal layer on the base material (100) is selected according to the metal characteristics of the metal layer to be formed.
Therefore, it may be electroplated or electroless plated. Further, when the welding point is formed at a predetermined position, a screen printing mesh is used and the solder cream is applied by screen coating to complete the process.

As a method for removing the wet film (6), an appropriate method is selected depending on the components of the wet film (6). In this example, it is dissolved and removed with sodium hydroxide, for example.

FIG. 5 discloses a flow chart of steps in the case of performing chemical nickel gold plating on a printed board used in a mobile phone. The print board of the mobile phone is arranged at a position where a push button is provided. Therefore, durability against friction is required. For this reason, chemical nickel gold plating is selected. However, according to the conventional method using a dry film, the penetration of plating easily occurs.

First, in step S1, the anti-fusing liquid is applied to the print board, and then in step S2, a wet film is formed on the print board by screen printing. Here, the oil-based ink used is OPTO-ER N-400G (H) manufactured by Nippon Paint Co., Ltd.
The required wet film viscosity is about 80-90 poise, using a mesh of various values T. Then, it is heated and dried in the step S3. The temperature is about 100 ° C and the time is 10 minutes.

Next, in the step S4, exposure and development are performed using a negative to form a pattern. Then, in step S5, chemical nickel gold is plated. The nickel composition has a thickness of about 100-200 μ ″, and the gold composition has a thickness of about 2-5 μ ″.

Next, in step S6, the wet film is eroded and removed with sodium hydroxide (NaOH).

Next, in step S7, an organic protective layer is formed on the surface of the metal layer not subjected to the nickel-gold chemical plating. This is to prevent the metal layer from contacting air and oxidizing. Ertek disclosed in the drawings refers to an organic film. The main component is BTA, and the main reason for selecting it is that sedimentation to the metal layer does not occur, and finally the product is packaged and shipped in the step S8.

Another application example is Chip scale packa
For ge products, the technical point is the process of electroplating soft gold on the printed board. Various processes using well-known techniques, or even with a dry film,
It is difficult to prevent the penetration of plating. When soft gold is electroplated by the method according to the present invention, the nickel component has a thickness of 200 μ ″ or more and the gold component has a thickness of between 20-40 μ ″. Therefore, the thickness is increased compared to nickel gold chemical plating,
The penetration of plating can be effectively improved.

The above are the embodiments of the present invention, and the present invention is not limited to these embodiments.
Therefore, any changes or modifications that can be made by those skilled in the art that have an equivalent effect on the present invention are included in the technical scope of the present invention.

[0031]

INDUSTRIAL APPLICABILITY The present invention is one in which a wet film is formed by applying a screen printing technique to a selective metal plating technique performed on a printed wiring board or the like, and is found in the conventional technique. It is possible to effectively improve the plating soaking phenomenon that occurs when performing selective metal plating, significantly increase the product yield, and not to complicate the manufacturing process, and use various related equipment. Therefore, the cost of the product can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a plating seeping phenomenon that occurs in a known technique.

FIG. 2 is an explanatory diagram in the case of forming a wet film by applying a screen printing technique in the method according to the present invention.

3 is a cross-sectional view of a pattern formed on the wet film in FIG.

FIG. 4 is a cross-sectional view of a metal layer formed by applying the present invention.

FIG. 5 is a flow chart showing steps of implementing the present invention.

[Explanation of symbols]

1 dry film 100 base materials 2 trowels 200 wiring board 4 mesh 6 Wet film 8 plated metal

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 2000-330276 (JP, A) JP 2000-122281 (JP, A) JP 2000-75484 (JP, A) JP 11-327136 (JP , A) JP 11-172179 (JP, A) JP 11-52571 (JP, A) JP 10-282662 (JP, A) JP 8-20742 (JP, A) JP 6-202314 (JP, A) JP-A-6-102662 (JP, A) JP-A-5-333545 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C25D 7/12 C25D 5/02 G03F 7/027 H01L 21/288

Claims (11)

(57) [Claims] 1. In a selective metal plating method, an oil-based ink which is a material for forming a wet film is agitated on a base material; the agitated oil-based ink is held stationary; and a trowel and a mesh are used. Applying the oil-based ink to the base material; applying the oil-based ink applied to the base material from room temperature to 40
Forming a wet film having photosensitivity by drying for 10 to 15 minutes at a temperature of ℃; curing the wet film; exposing the cured wet film to light; A step of developing to expose an area where a metal layer is formed on the base material; and a nickel component layer and a gold layer formed by plating on the base material.
A selective metal plating method comprising: a step of forming a metal layer containing a split layer ; and a step of removing an excess wet film. 2. The composition of the oil-based ink is 2 %.
Selective metal plating method according to claim 1, characterized in that it comprises et 3% antifoam. 3. The selective metal plating method according to claim 1, wherein the stirring of the oil-based ink is continued for 5 to 10 minutes. 4. The selective metal plating method according to claim 1, wherein the time during which the agitated oily ink is held stationary is 20 minutes to 30 minutes. 5. After the step of removing the excess wet film, an organic protective layer is further formed on the surface of the metal layer to prevent the metal from contacting with air and oxidizing. The selective metal plating method according to claim 1. 6. The selective metal plating method according to claim 1, wherein the base material is a printed wiring board. 7. The selective metal plating method according to claim 1, wherein the base material is a wiring board used in a mobile phone. 8. The metal layer has a thickness of 100 μm to 2 μm.
2. The selective metal plating method according to claim 1, wherein a nickel component layer having a thickness of 00 μm is plated with a gold component layer having a thickness of 2 μm to 5 μm . Wherein said metal layer is gold component in the thickness of 40 [mu] m from 20 [mu] m nickel component layer of 200 [mu] m or more thick
The selective metal plating method according to claim 1 , wherein the layer is plated. 10. The selective metal plating method according to claim 1, wherein, in the step of removing the excess wet film, the wet film is removed by eroding with a sodium hydroxide (NaOH) solution. 11. The selective metal plating method according to claim 1, wherein in the step of curing the wet film, the wet film is indirectly heated (Baking) to be cured.