KR20090103605A - Method for manufacturing printed circuit board - Google Patents

Abstract

PURPOSE: A method for manufacturing a printed circuit board is provided to prevent a defect of the printed circuit board due to the variation of the thickness of a copper layer by minimizing the variation of the thickness of the copper layer. CONSTITUTION: A substrate(111) with a metal layer is prepared. The metal layer(121,122) in a region to form a through hole is half-etched. The through hole is formed in the substrate which is half-etched. The through hole is formed using a laser drill. A conductive layer(131) is formed in an upper part and a lower part, and an inner wall of the through hole. The conductive layer is formed using an electroless method and an electrolytic method.

Description

Method for manufacturing printed circuit board

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board, and more particularly, to a method of manufacturing a printed circuit board which reduces a change in thickness of copper foil formed on a surface of a substrate.

With the development of electronic / communication technology, electronic / communication products are becoming smaller, thinner and more versatile. Electronic / communication products are equipped with integrated circuit chips and electronic components that implement various functions, and printed circuit boards are used to secure them in a narrow space and communicate electrical signals with each other. In order to increase the integration degree, a fine circuit having a narrow line width and a line distance is implemented in a printed circuit board.

In order to increase the degree of integration of the printed circuit board, a circuit is implemented in the upper and lower portions of the printed circuit board, and thus through holes are formed to electrically connect the circuits implemented in the upper and lower portions. A conductive film is formed on an inner wall of the through hole, and a circuit formed on the top of the substrate and a circuit formed on the bottom of the substrate are electrically connected through the conductive film.

Before fabricating the printed circuit board, copper foil layers are formed on the upper and lower portions of the original substrate, and in order to facilitate the formation of through holes, conventionally, the copper foil layer is first etched thinly and then drilled using a drill. Holes are formed, after which the copper foil layers are laminated to their original thickness to form a circuit.

As such, in the process of thinly etching the copper foil layer in order to form the through hole, the copper foil thickness is changed several times, thereby causing the substrate to expand and contract. When the expansion and contraction of the substrate occurs, a defect may occur in which the alignment state of the pattern of the mask for exposure is distorted and the through hole formation position changes.

An object of the present invention is to provide a method of manufacturing a printed circuit board to minimize the change in the thickness of the copper foil.

The present invention to achieve the above object,

(a) preparing a substrate having a metal layer formed on upper and lower surfaces thereof; (b) half etching the metal layer in the region where the through hole is to be formed; (c) forming a through hole in the substrate in the half etched region; And (d) forming a conductive film on the inner walls and upper and lower portions of the through hole.

In order to achieve the above object, the present invention also provides

(a) preparing a substrate having a metal layer formed on upper and lower surfaces thereof; (b) removing all the metal layers of the region where the through holes are to be formed; (c) forming a through hole in the substrate in the region where the metal layer is removed; And (d) forming a conductive film on the inner walls and upper and lower portions of the through hole.

According to the present invention, the change in the thickness of the copper foil is minimized by half etching or etching only the copper foil in the region where the through hole is formed.

Therefore, the defect of the printed circuit board which may occur due to the change of the copper foil thickness is prevented.

In addition, by partially half etching or etching the copper foil, the manufacturing cost of the printed circuit board is reduced as compared with conventionally etching the copper foil as a whole and then laminating it back to a specific thickness.

1 is a cross-sectional view of a printed circuit board manufactured using the manufacturing method according to the present invention.

2 shows a state in which metal layers are formed above and below the substrate.

3 shows a state in which the photoresist layer is masked.

4 shows a state in which the metal layers are half etched.

5 shows a state in which blackening layers are formed.

6 shows a state in which a through hole is formed.

7 illustrates a state in which a conductive film is formed in a through hole.

8 illustrates a state in which metal layers are formed above and below the substrate.

9 shows a state in which the photoresist layer is masked.

10 shows a state in which all metal layers are etched.

11 is a cross-sectional view of a state where a through hole is formed.

12 illustrates a state in which a conductive film is formed in a through hole.

<Description of the symbols for the main parts of the drawings>

101; A printed circuit board, 111; Board

121,122; Metal layers, 131; Conductive film

311,312; Photoresist layers 511,512; Blackening layers

611; Through hole, 1111; Thru Hall

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements.

1 is a cross-sectional view of a printed circuit board manufactured using the manufacturing method according to the present invention. Referring to FIG. 1, a printed circuit board 101 penetrates through a substrate 111, metal layers 121 and 122 formed on upper and lower surfaces of the substrate 111, a substrate 111, and metal layers 121 and 122. A through hole and a conductive film 131 formed on the inner wall and upper and lower portions of the through hole are provided.

2 to 7 are cross-sectional views illustrating a method of manufacturing a printed circuit board according to an embodiment of the present invention.

2 illustrates a state in which metal layers 121 and 122 are formed on upper and lower portions of the substrate 111. Referring to FIG. 2, metal layers 121 and 122 are formed on upper and lower surfaces of the substrate 111.

The substrate 111 is composed of an insulating material such as epoxy resin, polyimide (PI), liquid crystal polymer (LCP), polytetrafluoroethylene (PTFE) or a high functional resin substrate in combination thereof.

The metal layers 121 and 122 may be used as long as they have a good conductivity, but generally, copper having good electrical conductivity and low cost is typically used.

The substrate 111 may be purchased without the metal layers 121 and 122 formed to form the metal layers 121 and 122. At this time, the upper and lower parts of the substrate 111 are surface treated using an ion beam. The adhesion between the metal layers 121 and 122 that adheres to the substrate 111 is enhanced through the surface treatment process. Thereafter, metal layers 121 and 122 having desired thicknesses are formed by vacuum deposition. As the vacuum vapor deposition method, sputtering, thermal evaporation, or e-beam method can be used.

3 shows a state in which the photoresist layers 311 and 312 are masked. Referring to FIG. 3, photo-resist layers 311 and 312 are formed on the metal layers 121 and 122, and a mask (not shown) having a specific pattern is formed on the photoresist layers 311 and 312 and then exposed. When the mask is removed and the photoresist layers developed by exposure are etched and removed, the photoresist layers 311 and 312 are patterned as shown in FIG. 3. Here, the region from which the photoresist layers are removed is a region where the through hole is to be formed.

4 shows a state in which the metal layers 121 and 122 are half etched. As shown in FIG. 4, some of the metal layers 121 and 122 of the regions 411 and 412 from which the photoresist layers are removed are half-etched using an etching solution. For example, if the thickness of the metal layers 121 and 122 is 18 [um], not all of them are etched but half-etched until the thickness becomes thinner to a specific thickness, for example, 8 [um]. When the metal layers 121 and 122 are half-etched as described above, it is easy to form through holes in the substrate 111 using a laser drill.

As an etching liquid, gaseous additives, such as hydrogen chloride and hydrogen peroxide, can be mixed and used with the liquid etching liquid containing a cupric chloride, a ferric oxide, etc. At this time, hydrogen chloride supplies ions to cuprous chloride and ferric oxide, which are insoluble by reaction with metal, to have solubility. Hydrogen peroxide serves to oxidize the reduced copper chloride back to the original cupric chloride. do. Additives encompass all materials for the regeneration and oxidation of precipitates and reactants in addition to the materials given above. The etching solution includes not only the etching solution which is used for the first time but the additive is not added, but also the etching solution remaining after the etching is performed, and the etching solution that is used after the etching is reused to add a small amount of the additive.

5 shows a state in which blackening layers 511 and 512 are formed. Referring to FIG. 5, blackening layers 511 and 512 that absorb light may be formed by blackening a portion where a through hole (611 in FIG. 6) is to be formed. The surfaces of the metal layers 121 and 122 are oxidized to form the blackening layers 511 and 512. The reason for forming the blackening layers 511 and 512 is that the laser beam is reflected from the surfaces of the metal layers 121 and 122 when the CO 2 laser is directly irradiated onto the metal layers 121 and 122, thereby forming a through hole (611 in FIG. 6). This is to prevent the forming work from becoming difficult.

In order to form the blackening layers 511 and 512, various methods such as an electrical method, a chemical method, or a combination thereof may be used. The method of manufacturing a printed circuit board of the present invention has been described with respect to a method of oxidizing the surfaces of the metal layers 121 and 122, but the present invention is not limited thereto and may be variously modified. That is, the blackening layers 511 and 512 may be formed on the surfaces of the metal layers 121 and 122 by depositing or printing a layer of a material having excellent energy absorption rate.

6 shows a state in which the through hole 611 is formed. Referring to FIG. 6, a through hole 611 is formed in a region where the blackening layers 511 and 512 are formed using a laser drill (not shown) to penetrate the substrate 111. The through hole 611 is formed to allow the circuit patterns formed on the upper and lower portions of the substrate 111 to be electrically connected to each other.

After the through hole 611 is formed, a desmear process is further performed. The desmear process is a process of removing residues, such as smears, remaining in the through hole 611 in the process of forming the through hole 611. During the desmear process, the blackening layers 511 and 512 may be removed. When the blackening layers 511 and 512 are removed, an electrical method of supplying electricity to the metal layers 121 and 122, a chemical method of contacting and reducing a chemical solution, or an electrochemical method may be used. .

7 illustrates a state in which a conductive film is formed in the through hole 611. In order to form the conductive film 131, the first conductive film forming step and the second conductive film forming step are performed.

In the first conductive film forming step, a thin conductive film, such as 1-3 [um], is used as a seed layer on the inner wall of the through hole 611 and the surfaces of the blackening layers 511 and 512 by using an electroless plating method. To form a film. In the second conductive film forming step, a thick conductive film, for example, 17-15 [um], is formed on the thin conductive film by electrolytic plating. That is, since the through holes 611 and the metal layers 121 and 122 are electrically connected to each other by the thin conductive film formed in the first conductive film forming step, plating is performed by flowing electricity to the metal layers 121 and 122. A thick conductive film is formed on the thin conductive film.

Thereafter, the photoresist layers 311 and 312 formed on the metal layers 121 and 122 are removed. Then, the printed circuit board 101 as shown in FIG. 1 is completed.

8 to 12 are cross-sectional views illustrating a method of manufacturing a printed circuit board according to another exemplary embodiment of the present invention.

8 illustrates a state in which metal layers 121 and 122 are formed on upper and lower portions of the substrate 111. Referring to FIG. 8, metal layers 121 and 122 are formed on the upper and lower surfaces of the substrate 111.

The substrate 111 is composed of an insulating material such as epoxy resin, polyimide (PI), liquid crystal polymer (LCP), polytetrafluoroethylene (PTFE) or a high functional resin substrate in combination thereof.

The metal layers 121 and 122 may be used as long as they have a good conductivity, but generally, copper having good electrical conductivity and low cost is typically used.

The substrate 111 may be purchased without the metal layers 121 and 122 formed to form the metal layers 121 and 122. At this time, the upper and lower parts of the substrate 111 are surface treated using an ion beam. The adhesion between the metal layers 121 and 122 that adheres to the substrate 111 is enhanced through the surface treatment process. Thereafter, metal layers 121 and 122 having desired thicknesses are formed by vacuum deposition. As the vacuum vapor deposition method, sputtering, thermal evaporation, or the e-beam method can be used.

9 shows a state in which the photoresist layers 311 and 312 are masked. Referring to FIG. 9, photoresist layers 311 and 312 are formed on metal layers 121 and 122, a mask (not shown) having a specific pattern is placed on the photoresist layers 311 and 312, and then exposed. If the mask is removed and then the photoresist layers 311 and 312 developed by exposure are etched and removed, the photoresist layers 311 and 312 are patterned as shown in FIG. 9. Here, the region where the photoresist layers are removed is a region where the through hole (1111 of FIG. 11) is to be formed.

10 shows a state in which all of the metal layers 121 and 122 are etched. As shown in FIG. 10, the metal layers of the region 1011 from which the photoresist layers have been removed are etched using an etchant. As such, when the metal layers 121 and 122 are etched, it is easy to form through holes in the substrate 111 by using a mechanical drill.

As an etching liquid, gaseous additives, such as hydrogen chloride and hydrogen peroxide, can be mixed and used with the liquid etching liquid containing a cupric chloride, a ferric oxide, etc. At this time, hydrogen chloride supplies ions to cuprous chloride and ferric oxide, which are insoluble by reaction with metal, to have solubility. Hydrogen peroxide serves to oxidize the reduced copper chloride back to the original cupric chloride. do. Additives encompass all materials for the regeneration and oxidation of precipitates and reactants in addition to the materials given above. The etching solution includes not only the etching solution which is used for the first time but the additive is not added, but also the etching solution remaining after the etching is performed, and the etching solution that is used after the etching is reused to add a small amount of the additive.

11 is a cross-sectional view of a state where the through hole 1111 is formed. Referring to FIG. 11, a through hole 1111 penetrating the substrate 111 is formed in a region where the metal layers 121 and 122 are etched by using a mechanical drill. The desmear process is further performed after the through hole 1111 is formed. The desmear process is a process of removing a residue, such as smear, remaining in the through hole 1111 in the process of forming the through hole 1111.

12 illustrates a state in which the conductive film 131 is formed in the through hole 1111. In order to form the conductive film 131, a first conductive film forming step and a second conductive film forming step are performed.

In the first conductive film forming step, a thin conductive film, such as 1-3 [um], is formed on the inner wall of the through hole 1111 and the upper and lower surfaces of the substrate 111 by using an electroless plating method. In the second conductive film forming step, a thick conductive film, for example, 17-15 [um], is formed on the thin conductive film by electrolytic plating. That is, since the through holes 1111 and the metal layers 121 and 122 are electrically connected to each other by the thin conductive film formed in the first conductive film forming step, plating is performed by applying electricity to the metal layers 121 and 122. A thick conductive film is formed on the thin conductive film.

Thereafter, the photoresist layers 311 and 312 formed on the metal layers 121 and 122 are removed. Then, the printed circuit board 101 as shown in FIG. 1 is completed.

The printed circuit board of the present invention is applicable to High Density Interconnection (HDI), Ultra Thin-Chip Scale Package (UT-CSP), Ball Grid Array (BGA), Flip Chip Ball Grid Array (FCBGA), and the like. Applicable to all products that require the implementation of.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (8)

(a) preparing a substrate having a metal layer formed on upper and lower surfaces thereof; (b) half etching the metal layer in the region where the through hole is to be formed; (c) forming a through hole in the substrate in the half etched region; And (d) forming a conductive film on inner walls and upper and lower portions of the through hole. The method of claim 1, wherein step (b) (b-1) forming a photoresist layer on the metal layer; And (b-2) patterning the photoresist layer to remove the photoresist layer in the region where the through hole is to be formed. The method of claim 1, wherein the step (b) further comprises blackening the half-etched region to form a blackening layer. The method of manufacturing a printed circuit board according to claim 1, wherein the conductive film is formed using an electroless method and an electrolytic method. The method of claim 1, wherein the through hole is formed by using a laser drill. (a) preparing a substrate having a metal layer formed on upper and lower surfaces thereof; (b) removing all the metal layers of the region where the through holes are to be formed; (c) forming a through hole in the substrate in the region where the metal layer is removed; And (d) forming a conductive film on inner walls and upper and lower portions of the through hole. The method of claim 6, wherein step (b) (b-1) forming a photoresist layer on the metal layer; And (b-2) patterning the photoresist layer to remove the photoresist layer in the region where the through hole is to be formed. 7. The method of claim 6, wherein the through hole is formed by using a mechanical drill.