KR20050001029A - Method for manufacturing double side a flexible printed circuit board - Google Patents

Abstract

PURPOSE: A method is provided to allow for ease of manufacture of high density circuit by forming a plating layer all over one surface of a printed circuit board and forming a plating layer only on the selected part of the other surface of the printed circuit board, centering from a copper clad lamination. CONSTITUTION: A method comprises a step of forming a through hole(15) or a blind via hole(16) at a surface of a copper clad lamination(10); a step of performing a Desmear process after formation of the hole, through an ultrasonic cleaning and a plasma etching; a step of providing the surface of the copper clad lamination, and the through hole or the blind via hole of the copper clad lamination with a conductivity, by performing an electroless copper plating; a step of adhering an anti-plating dry film onto the other surface of the copper clad lamination; a step of removing a certain part of the dry film by selectively exposing and developing the dry film; a step of forming a copper plating layer on both sides of the copper clad lamination by performing a copper plating after removal of part of the dry film; a step of removing the residual dry film; and a step of forming circuit patterns which require different elasticity on the portion where the copper plating layer is formed and the portion where the copper plating layer is not formed, respectively.

Description

Manufacturing method of double-sided flexible printed circuit board {METHOD FOR MANUFACTURING DOUBLE SIDE A FLEXIBLE PRINTED CIRCUIT BOARD}

The present invention relates to a flexible printed circuit board having a double-sided structure. In particular, in a flexible printed circuit board having a double-sided structure, a double-sided flexible printed circuit is formed on one side of the copper-clad laminate based on the copper foil laminated board and the other side selectively forms a plated layer only on the required portion. It relates to a method for manufacturing a circuit board.

In recent years, due to the development of electronic components and component embedding technology and the light and small size of electronic products, the demand for flexible printed circuit boards is continuously growing, and also due to the rapid development of the integrated density of semiconductor integrated circuits, small chips and their components are mounted. With the development of surface-mount technology, the demand for flexible printed circuit boards that can be easily embedded in more complex and narrow spaces continues to increase.

In particular, in the case of a flexible printed circuit board with a double-sided structure, which is easy to increase the circuit density and has a high level of use, with the development of mobile phones, LCD panels, PDPs, etc., the amount of usage increases rapidly, and the technology development of the manufacturing technology. The demand is increasing.

1 is a cross-sectional view illustrating a copper foil laminated plate of a general flexible printed circuit board, FIG. 2A is a cross-sectional view of forming a through hole in a copper laminate, and FIG. 2B is a cross-sectional view of a blind via hole formed in a copper laminate.

As shown in FIG. 1, the copper-clad laminate 10 includes a base film 11 made of a material such as a polyimide film formed on a central surface thereof, and a thickness of about 12 μm to 18 μm on both surfaces of the base film 11. It consists of the first and second copper foil layers 12, 13 formed of.

The through-hole 15 or the blind via hole 16 is formed on the copper-clad laminate 10 by using a drilling means such as an NC drill or a laser drill. The through-hole 15 is a copper-clad laminate as shown in FIG. 2A. 10 is completely penetrated, and the blind via hole 16 is perforated only from the first copper foil layer 12 to the base film 11 as shown in FIG. 2B.

3 is a cross-sectional view showing the structure of a double-sided flexible printed circuit board according to the prior art, the copper foil laminated plate 10 having the copper foil layers 12 and 13 formed on the upper and lower surfaces of the base film 11, and the copper foil laminated plate ( A copper plated layer 25 newly plated is placed in the outer layer and through hole 15 of 10).

Such a printed circuit board is manufactured through the process as shown in FIG. 4. First, a flexible copper foil laminate 10 having a double-sided structure in which copper foil layers 12 and 13 having a thickness of 12 μm to 18 μm are laminated on both sides of the base film 11. ) Is purchased and put into the process (S1).

Next, the through-hole 15 is processed using an NC drill or a laser drill on the copper-clad laminate 10 (S2), and the variance of the periphery of the through-hole 15 and the inside of the hole is removed (S3). The electroless copper plating process of imparting conductivity to the inside of the processed hole 15 is performed (S4).

This is again subjected to electrolytic copper plating to form a plating layer 25 on top of the copper foil layers 12 and 13 (S5), which is then polished or washed again (S6).

Then, a dry film, which is a photosensitive etching resist, is applied to the upper surface of the plating layer 25 (S7), and the copper foil laminated plate 10 on which the dry film is laminated is exposed using an exposure machine, and the exposed copper foil laminated plate ( 10) is developed using a developer, and is etched using an etching machine to form a required pattern (not shown), and then a double-sided flexible printed circuit board is manufactured through a subsequent process (S8. S9).

However, as in the above-described processes and structures, the copper plating layer for electrically and mechanically connecting the upper and lower copper foil layers 12 and 13 through the through holes 15 formed on the copper foil layer 12 and 13 surfaces. In this process, the copper plating layer 25 is applied to the inner wall of the through hole 15, and at the same time, the plating layer 25 is formed on the upper and lower copper foil layers 12 and 13, respectively. As a result, the copper foil layers 12 and 13 become thicker, which makes it difficult to form a high-density circuit and inhibits the bending resistance of the entire circuit, making it impossible to form a circuit having both sides and bending resistance. It was.

Accordingly, an object of the present invention is to form a through hole or a blind via hole in the copper-clad laminate, then shield one side of the copper-clad laminate with a dry film, and then expose and develop the dry film of the portion to be copper plated, and then perform copper plating on both sides. The present invention provides a method for manufacturing a double-sided flexible printed circuit board that can form a high-density circuit by maintaining the inherent thickness of the copper-clad laminate by not forming a plating layer on a part of one side of the copper-clad laminate.

In addition, another object of the present invention is to shield the dry film on the opposite side where the blind via hole is processed in the copper-clad laminate, and then exposed and developed only the portion to be copper plated to perform copper plating, and then remove the dry film, copper foil laminated plate The present invention provides a method of manufacturing a double-sided flexible printed circuit board capable of selectively forming a circuit requiring a high flex resistance because a plating layer is not formed on a portion of one side thereof.

1 is a cross-sectional view showing a general double-sided flexible copper clad laminate,

FIG. 2A is a cross-sectional view in which through holes are formed in a general double-sided flexible copper clad laminate, and FIG. 2B is a cross-sectional view in which blind via holes are formed in a general double-sided flexible copper clad laminate.

3 is a cross-sectional view showing a double-sided printed circuit board according to the prior art,

4 is a flowchart showing the entire manufacturing process of FIG. 3 according to the prior art,

5A to 5E are cross-sectional views illustrating a manufacturing process of a double-sided flexible printed circuit board according to an embodiment of the present invention.

6 is a flowchart illustrating a manufacturing process of a double-sided flexible printed circuit board according to an embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

10: copper clad laminate 11: base film

12: 1st copper foil layer 13: 2nd copper foil layer

15: through hole 16: blind via hole

21: electroless plating layer 25: electrolytic copper plating layer

30: dry film

In accordance with an aspect of the present invention, a method of manufacturing a double-sided printed circuit board using a flexible copper clad laminate includes: forming a through hole or a blind via hole in the copper clad laminate; Performing a desmear process through ultrasonic cleaning and plasma etcher after forming the hole; Conducting electroless copper plating on the surface, through-holes or blind via holes of the copper-clad laminate after the desmearing treatment to impart conductivity; Bonding a plating preventing dry film to the other copper foil surface on which the blind via hole is formed; Selecting a portion of the dry film to be plated with copper and exposing and developing to remove a portion of the dry film; Removing a part of the dry film and performing copper plating to form copper plating layers having a required thickness on the upper and lower surfaces of the copper foil laminated plate, respectively; Removing the residual dry film after forming the copper plating layer; And forming an appropriate circuit pattern requiring different bend resistances in a portion where the copper plating layer is formed and a portion where the copper plating layer is not formed.

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

5A to 5E illustrate a process of forming copper plating on a copper clad laminate according to an embodiment of the present invention, and FIG. 6 illustrates a method of manufacturing a double-sided flexible printed circuit board according to an embodiment of the present invention. It is a flowchart.

First, as shown in FIG. 1, a base film 11 made of a material such as a polyimide film formed on a central surface thereof, and a first film having a thickness of about 12 μm to 18 μm on both surfaces of the base film 11. And a copper foil laminated plate 10 formed of the second copper foil layers 12 and 13.

Then, the present invention will be described with reference to FIGS. 5A to 6.

First, as shown in FIG. 1, the copper foil laminated plate 10 having the first and second copper foil layers 12 and 13 formed on both surfaces of the base film 11 is introduced (S21).

Next, the copper foil laminated plate 10 is formed by selectively forming through-holes 15 and blind via holes 16 as shown in FIGS. 2A and 2B by using a drilling means such as an NC drill or a laser drill (S22). At this time, when the blind via hole 16 is processed, only the base film 11 is processed so that the second copper foil layer 13 of the lower surface is exposed without being drilled.

In order to remove the variance of the copper-clad laminate 10 thus processed, it was ultrasonically cleaned for about 6 minutes in an IPA solvent (IPA: CH ₃ CHOHCH ₃ ), and then washed approximately 20 in a plasma etcher (O ₂ , under N ₂ gas). Plasma treatment is performed for a minute (S23, S24). As described above, the desmear treatment is performed through the IPA solvent and the plasma etcher, so that the through hole, the blind via hole, and the surface of the copper foil can be treated more smoothly and cleanly.

After the desmearing treatment as described above, electroconductivity is imparted to the surface of the copper-clad laminate 10 and the inner wall of the processed through hole 15 or the blind via hole 16 through the electroless plating process. The plating layer 21 is formed (S25).

In this state, as shown in FIG. 5B, the dry film 30 is laminated on the side of the second copper foil layer 13, which is one side of the copper foil laminated plate 10 (S26). At this time, when the blind via hole 16 is formed in the copper-clad laminate 10, the dry film 30 must be adhered to the second copper foil layer 13 side where the blind via hole 16 is not processed.

As described above, in the state where the dry film 30 is installed, the dry film 30 is selectively exposed and developed according to a design pattern to remove only a part of the dry film 30 to form as shown in FIG. 5C (S27). That is, the dry film 30 is adhered to the opposite side on which the blind via hole 16 is formed, and then the dry film 30 of the portion where the copper plating layer is to be formed (except for the portion not to form the copper plating layer) is selectively removed according to the design pattern. do.

In this state, when the copper-clad laminate 10 is put into the plating process, as shown in FIG. 5D, the surface of the through hole 15, the blind via hole 16, the first copper foil layer 12, and the unshielded second copper foil layer ( The copper plating layer 25 having a thickness of about 10 μm or more is coated on a part of the surface 13), and at this time, copper plating is performed due to the dry film 30 only on a part of the second copper foil layer 13 on which the dry film 30 is covered. The thickness of the original second copper foil layer 13 is maintained as it is, and the first and second copper foil layers 12 and 12 of the upper and lower surfaces are formed through the through hole 15 or the blind via hole 16. 13) is to be completely electrically coupled (S28).

Subsequently, when the residual dry film 30 adhered to the second copper foil layer 13 side of the copper foil laminated plate 10 is removed (S29), the structure is as shown in FIG. 5E. The portion of the second copper foil layer 13 side covered with the dry film 30 is not plated and has a thin thickness, and the other portion of the second copper foil layer 13 is the copper plating layer 25. Due to the thickness, the upper and lower first and second copper foil layers 12 and 13 are completely bonded through the copper plating layer 25 plated inside the through hole 15 or the blind via hole 16.

By this double-sided plating technique, as shown in the cross-sectional view of FIG. 5E, all of the copper plating layers 25 are raised on the first copper foil layer 12 of the copper-clad laminate 10, but on the other side, that is, the second copper foil layer The copper plating layer 25 is formed in one part of (13), and the copper plating layer 25 is not formed in the other part, and the copper foil layer of the upper / lower surface based on the copper foil laminated board 10 is referred to. It has a one-side plating portion (㉮) is formed asymmetrically, the copper plating layer (25) does not rise on the one-side plating portion to maintain the original thickness and at the same time have the bending resistance characteristics of the original material You can keep it as it is.

Next, a conventional printed circuit manufacturing process is performed, and the polishing and washing process is performed on the material as shown in FIG. 5E (S30), followed by a dry film lamination process, double-sided exposure, development, and etching process. A predetermined circuit pattern (not shown) is formed (S31, S32).

Thereafter, the final product is completed through various processes such as coverlay adhesion, printing, plating, and outer processing required for manufacturing a flexible printed circuit board (S33).

Although specific embodiments of the present invention have been described and illustrated above, rather than simultaneously forming through-holes and blind via-holes in a single copper-clad laminate, they can be formed separately as needed, thereby printing one-side plating processes and circuit patterns. It is obvious that various modifications can be made. Such modified embodiments should not be individually understood from the technical spirit or the prospect of the present invention, but should fall within the claims appended to the present invention.

Therefore, in the present invention, after forming through-holes or blind via holes in the copper-clad laminate, one side of the copper-clad laminate is covered with a dry film, and the dry film of the portion to be plated is exposed and developed, and copper plating is performed on both sides. The plated layer is not formed on a part of one side of the laminated plate so that the original thickness (intrinsic thickness of the copper-clad laminate) is maintained as it is, so that a high density circuit can be easily formed, and a blind via hole is formed in the copper-clad laminate. After shielding with a dry film on the opposite side, the copper plating is performed by exposing and developing only the part to be copper plated, and then removing the dry film, so that a part of one side of the copper foil laminated plate is not formed so that high bending resistance and high density are achieved. The circuit can be selectively formed to require the It can easily adapt it to a variety of benefits, such as to expand the width of the product design.

Claims (3)

In a method for manufacturing a double-sided printed circuit board using a flexible copper clad laminate: Forming a through hole or a blind via hole in the copper-clad laminate; Performing a desmear process through ultrasonic cleaning and plasma etcher after forming the hole; Conducting electroless copper plating on the surface, through-holes or blind via holes of the copper-clad laminate after the desmearing treatment to impart conductivity; Bonding a plating preventing dry film to the other copper foil surface on which the blind via hole is formed; Selecting a portion of the dry film to be plated with copper and exposing and developing to remove a portion of the dry film; Removing a part of the dry film and performing copper plating to form copper plating layers having a required thickness on the upper and lower surfaces of the copper foil laminated plate, respectively; Removing the residual dry film after forming the copper plating layer; And And forming an appropriate circuit pattern requiring different bend resistances in a portion where the copper plating layer is formed and a portion where the copper plating layer is not formed. 2. The method according to claim 1, The process of performing the desmear process is a method of manufacturing a double-sided flexible printed circuit board, characterized in that the ultrasonic treatment in the IPA solvent for about 6 minutes to wash and then plasma treatment for about 20 minutes in the plasma etcher. The method according to claim 1, In the step of forming a circuit pattern on the copper-clad laminate, a circuit having a low density is disposed in a portion where the copper plating layer is formed, and a circuit requiring flex resistance and high density is disposed and formed in a portion where the copper plating layer is not formed. Method of manufacturing double-sided flexible printed circuit board.