KR20100068787A - Printed circuit board and method for fabricating the same - Google Patents

Abstract

PURPOSE: A printed circuit board and manufacturing method thereof does not accompany the deposition process by the sputtering process and photo lithography process. The manufacturing process is simplified and the material cost is reduced. CONSTITUTION: A base film(10) is included of the polyimide. The coating seed layer(30) printed on the base film. The metallic coating(40) is formed on the coating seed layer. In the surface of the base film, the surface reformed layer(20) is formed. The surface reformed layer has the bonding structure of the oxygen and metal.

Description

Printed circuit board and its manufacturing method {PRINTED CIRCUIT BOARD AND METHOD FOR FABRICATING THE SAME}

The present invention relates to a printed circuit board and a method for manufacturing the same, and more particularly, to a printed circuit board using a polyimide as a base film.

Recently, in the field of electronics industry, the amazing integration of semiconductor integrated circuits, the development of surface mount technology for directly mounting small chip components, and the rapid and light reduction of electronic products such as mobile communication devices have been rapidly made. Accordingly, the use of flexible printed circuit boards (PCBs), which are easier to install in spaces in electronic products than conventional rigid printed circuit boards, has become common.

In addition, in order to achieve higher density of circuit patterns, the use of multilayer flexible PCBs or PCBs in which rigid PCBs and flexible PCBs are mixed is rapidly increasing.

Conventionally, a copper clad laminate (hereinafter referred to as CCL) was used as a material, and a PCB was manufactured by a lithography method. However, the prior art has a high material cost of CCL, photoresist, and the like, many processes of generating waste such as heavy metal wastewater, organic solvent, etc., and a large number of processes such as coating, exposure, development, etching, and cleaning, and high equipment and process cost. There is a problem.

Various methods have been introduced to improve the problem of PCB fabrication by lithography. A method of fabricating a PCB by coating a photosensitive plating active material on a polyimide base film, selectively irradiating a laser and then plating copper (Cu) without using a CCL and a photomask is proposed. Also, without using CCL, a method of selectively forming a plating seed layer and a resistive layer on a polyimide base film by a photolithography process and plating copper has been proposed. In addition, a method of coating a conductive polymer on a polyimide base film with a plating seed layer and plating copper has been proposed.

However, the conventional methods have a problem of low adhesion between the plating seed layer and the polyimide base film.

In order to increase the adhesion between the polyimide base film and the plating seed layer, a method of coding an adhesive layer containing a silane additive on the surface of the polyimide base film, plasma treatment on the surface of the polyimide base film, and a surface treatment of the diamine compound The method of modifying the surface of a mid base film, etc. were proposed. In these methods, a circuit pattern is formed by coating a plating seed layer on the entire surface of the polyimide base film by sputtering deposition and then removing the plating seed layer formed in a region other than the predetermined circuit pattern.

However, since the plating seed layer is coated on the entire surface of the polyimide base film by the metal sputtering deposition process, the conventional methods should add a process for removing metal in a region other than a predetermined circuit pattern. Therefore, there is a problem that the cost increases due to the loss of material and the complexity of the process.

Accordingly, the present invention is to provide a printed circuit board and a method of manufacturing the same that can enhance the adhesion between the polyimide base film and the plating seed layer and simplify the circuit pattern forming process.

The printed circuit board of the present invention includes a base film made of polyimide; A plating seed layer printed on the base film according to a predetermined circuit pattern; And a metal plating layer formed on the plating seed layer, wherein a surface modification layer having a bonding structure of metal and oxygen forming the plating seed layer is formed on a surface of the base film.

The bonding structure may further include a bonding structure of palladium (Pd) and a metal forming the metal seed layer.

The metal forming the plating seed layer is silver (Ag), and the bonding structure includes any one of a bonding structure of oxygen and silver, and a bonding structure of oxygen, palladium, and silver.

In addition, the method of manufacturing a printed circuit board of the present invention comprises the steps of (a) immersing a polyimide film in a solution containing potassium hydroxide (KOH) and ethylenediamine (EDA) to modify the surface of the polyimide film; (b) forming a plating seed layer printed on a surface of the modified polyimide film according to a predetermined circuit pattern; And (c) forming a metal plating layer on the plating seed layer.

The process (a) is characterized in that it is carried out for 3 to 10 minutes at a temperature of 50 ~ 80 ℃.

After the step (a) and before the step (b), further comprising the step of activating the polyimide film by immersing the modified polyimide film in an acid solution containing HCl and PdCl ₃ catalyst It is done.

The step (b) is characterized in that the conductive ink containing the metal of the plating seed layer to be formed on the surface of the modified polyimide film is printed and then heated to sinter the metal particles of the conductive ink into a metal layer. .

The conductive ink may be a silver nitrate (AgNO ₃ ) solution or a solution in which silver (Ag) particles are dispersed.

And (e) further immersing the activated polyimide film in H ₂ SO ₄ solution after the step (d).

After the step (b) is characterized in that it further comprises the step of (f) activating the plating seed layer surface with H ₂ SO ₄ solution.

According to the present invention, by forming a functional group capable of binding a metal ion to the surface of the polyimide base film and the metal ion to form a plating seed layer to the functional group is bonded to enhance the adhesion between the polyimide film and the plating seed layer. Can be.

In addition, according to the present invention, since it does not involve the deposition process and the photolithography process by the sputtering method, the manufacturing process can be simplified, the material cost can be reduced, and mass production is easy.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a cross-sectional view schematically showing the structure of a printed circuit board according to the present invention.

Referring to FIG. 1, a printed circuit board according to the present invention includes a base film 10; A surface modification layer 20 formed on the surface of the base film; A plating seed layer 30 printed on the surface modification layer 20 according to a predetermined circuit pattern; And a metal plating layer 40 formed on the plating seed layer 30.

Since the base film 10 is a polyimide film, the polyimide film is characterized by excellent heat resistance, electrical properties, chemical resistance, and flex resistance compared to other polymer materials, such as a flexible PCB, a tape for automatic bonding (TAB), Various applications have been made as insulating substrate materials for electronic components such as chip on film (COF).

The surface modification layer 20 has a bonding structure of a metal and oxygen forming a plating seed layer, this bonding structure is the adhesion between the polyimide film 10 and the plating seed layer 20 formed thereon It serves to strengthen. For example, when the plating seed layer is formed of silver (Ag), the surface modification layer 20 includes a bonding structure of silver and oxygen. The bonding structure in the surface modification layer 20 is a functional group capable of bonding a metal ion to the surface of the polyimide film by immersing the polyimide film 10 in a solution containing potassium hydroxide (KOH) and ethylenediamine (EDA) compound. After the formation of the plating seed layer formed thereon, the metal ions in the plating seed layer is formed by binding to the functional group, a specific process will be described in detail in the description of the manufacturing method to be described later.

The plating seed layer 30 is printed on the surface modification layer 20 according to a predetermined circuit pattern. For example, the plating seed layer 30 may be formed by a printing method such as direct patterning technology through inkjet. Direct patterning technology is a technique for forming a circuit pattern by directly discharging a predetermined amount of conductive ink, for example, silver (Ag) ink through an inkjet head in the correct position. As such, when the metal seed layer is selectively formed as the circuit pattern on the surface modification layer 20 by the printing method, masking and etching processes for removing the metal seed layer formed in addition to the circuit pattern region are omitted. Rather, the manufacturing process and time can be shortened.

The metal plating layer 40 is grown thereon based on the plating seed layer 30, and forms, for example, a copper plating layer formed according to a circuit pattern determined by electroless or electrolytic plating containing copper.

2A to 2E are cross-sectional views illustrating a manufacturing process of a printed circuit board according to an exemplary embodiment of the present invention. The manufacturing method of the printed circuit board according to the present invention will be described as follows.

First, as shown in Figure 2a to remove the organic material on the surface of the polyimide film 10 with acetone, the molecular structure of the polyimide film at this time is as follows.

In FIG. 2B, the polyimide film is immersed in a solution containing potassium hydroxide (KOH) and ethylenediamine (EDA) to modify the polyimide film surface. The surface modification process is a process for converting imide bonds in a polyimide film into carboxyl groups (-COOH-) and amide bonds (-CONH-) to form functional groups to which metal ions can bind. As such, when a functional group capable of binding metal ions is formed on the surface of the polyimide film, the metal ions in the plating seed layer combine with the functional group to form a bonding structure when the plating seed layer is formed, thereby forming the polyimide film and the plating seed layer. Can enhance the adhesion of the.

After surface modification, the molecular structure of the surface modification layer 20 'formed on the surface of the polyimide film is as follows.

Preferred immersion conditions for modifying the polyimide film is to perform for 3 to 10 minutes at a temperature of about 50 ~ 80 ℃. In addition, although potassium hydroxide (KOH) treatment and ethylenediamine (EDA) treatment may be performed sequentially, it is advantageous to treat with a complex solution of potassium hydroxide and ethylenediamine in terms of reducing the number of processes.

In FIG. 2C, hydrogen ions are removed by immersing the modified polyimide film in an acidic solution containing HCl and PdCl ₃ catalyst and activating the surface modification layer (surface of the surface modified polyimide film) (20 ″). Activation of the layer may later cause a large amount of metal to precipitate in a short time in the plating seed layer formation process, but this may not be done as an option, and may also be further immersed in H ₂ SO ₄ solution to accelerate the dehydrogenation reaction. Preferred conditions for activating the surface modification layer are 1-6 minutes in an acidic solution containing HCl and PdCl ₃ catalyst at a temperature of 35-45 ° C. and in a H ₂ SO ₄ solution at a temperature of 35-45 ° C. Soak for an additional 1 to 4 minutes.

After step 2c, the molecular structure of the activated surface modification layer 20 "is as follows.

In FIG. 2D, the conductive ink is printed on the surface of the activated surface modification layer according to a predetermined circuit pattern and then sintered to form a plating seed layer 30. The circuit pattern can be formed by, for example, directly discharging a certain amount of conductive ink to a corresponding position by direct patterning technology through inkjet. The component of the conductive ink is, for example, a silver nitrate (AgNO ₃ ) solution or a solution in which silver (Ag) particles having a diameter of 1 to 200 nm are dispersed. In the conductive ink of the silver nitrate solution component, a predetermined dispersant may be added to the solution in advance so that silver particles having a diameter of 1 to 200 nm are precipitated during the drying process. The polyimide film printed with the conductive ink is heated at a temperature in the range of 100 to 300 ° C. to sinter the nano metal particles of the conductive ink into the metal layer. The sintered metal layer acts as a plating seed layer and its thickness generally ranges from 0.1 to 3 μm. The thickness of the plating seed layer is not limited to the above range. However, if the thickness of the plating seed layer is too thin, the plating seed layer may be peeled off in the plating furnace. In addition, in order to improve the efficiency of the plating process, the surface of the plating seed layer may be further activated with a catalyst solution containing PdCl ₃ .

After step 2d, the molecular structure of the surface modification layer 20 is as follows.

That is, a bonding structure of metal, for example, silver (Ag), which forms a palladium (Pd) used as a catalyst and a plating seed layer in the surface modification layer 20 is formed to form a polyimide film 10 and a silver plating seed. Adhesion with layer 30 is enhanced.

If the step 2c is omitted after the step disclosed in FIG. 2b and the step 2d is directly performed, that is, if the step of activating the surface modification layer by immersion in an acid solution including HCl and PdCl ₃ catalyst is omitted, The molecular structure of the surface modification layer 20 is as follows.

That is, in the surface modification layer, a bonding structure of oxygen in the polyimide film and silver in the plating seed layer 30 is formed to enhance adhesion between the polyimide film 10 and the silver plating seed layer 30.

In FIG. 2E, a copper plating layer formed according to a circuit pattern is formed by immersing the polyimide film 10 having the plating seed layer 30 formed therein into, for example, an electrolytic or non-electrolytic plating. Accordingly, the copper plating layer may be formed in a predetermined circuit pattern without chemically or physically etching the plating seed layer and the metal plating layer.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various changes or modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

1 is a cross-sectional view schematically showing the structure of a printed circuit board according to the present invention;

2A through 2E are cross-sectional views illustrating a manufacturing process of a printed circuit board according to an exemplary embodiment of the present invention.

Claims (10)

A base film made of polyimide; A plating seed layer printed on the base film according to a predetermined circuit pattern; And A metal plating layer formed on the plating seed layer; The surface of the base film, the printed circuit board, characterized in that the surface modification layer having a bonding structure of the metal and oxygen forming the plating seed layer is formed. The printed circuit board of claim 1, wherein the bonding structure further comprises a bonding structure of palladium (Pd) and a metal forming the metal seed layer. The metal forming the plating seed layer is silver (Ag), and the bonding structure includes any one of oxygen and silver bonding structures and oxygen and palladium and silver bonding structures. Printed circuit board. (a) immersing the polyimide film in a solution containing potassium hydroxide (KOH) and ethylenediamine (EDA) to modify the surface of the polyimide film; (b) forming a plating seed layer printed according to a predetermined circuit pattern on the surface of the modified polyimide film; And (c) forming the metal plating layer on the plating seed layer. The method of claim 4, wherein the step (a) Method of manufacturing a printed circuit board, characterized in that performed for 3 to 10 minutes at a temperature of 50 ~ 80 ℃. After the step (a) and before the step (b), further comprising the step of activating the polyimide film by immersing the modified polyimide film in an acid solution containing HCl and PdCl ₃ catalyst A method of manufacturing a printed circuit board. The method of claim 4, wherein the step (b) A method of manufacturing a printed circuit board, comprising: printing a conductive ink containing a metal of a plating seed layer to be formed on a surface of the modified polyimide film, and then heating and sintering metal particles of the conductive ink into a metal layer. . The method of claim 7, wherein the conductive ink A method of manufacturing a printed circuit board characterized in that the silver nitrate (AgNO ₃ ) solution or a solution in which silver (Ag) particles are dispersed.  The method of claim 6, wherein after the step (d) And (e) immersing the activated polyimide film in a H ₂ SO ₄ solution. The method of claim 4, wherein after the step (b) The method of manufacturing a printed circuit board further comprising the step of (f) activating the plating seed layer surface with H ₂ SO ₄ solution.

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