KR20040061046A - Method for building layer of printed circuit board - Google Patents

Abstract

PURPOSE: A method is provided to reduce manufacturing costs and defects by eliminating the necessity of using a drill or laser and a desmearing process. CONSTITUTION: A method comprises a first step of attaching a first photo-sensitive polyimide film on a lower copper foil; a second step of forming a photo mask on the first photo-sensitive polyimide film, radiating ultraviolet rays to the resultant structure, developing the resultant structure, and selectively forming a via hole for electrically connecting upper and lower copper foils on the first photo-sensitive polyimide film; a third step of performing a cleaning process; a fourth step of filling the via hole with an anisotropic conductor; a fifth step of pressing the upper copper foil in such a manner that the upper copper foil is attached to the first photo-sensitive polyimide film and the anisotropic conductor and the upper and lower copper foils are electrically connected with each other; a sixth step of forming a dry film on the upper copper foil; a seventh step of performing a photographic and developing process by using the photo mask corresponding to the pattern constituted by the upper copper foil; an eighth step of forming a pattern constituted by the upper copper foil by selectively removing the upper copper foil; a ninth step of performing a cleaning process; and a tenth step of attaching a second photo-sensitive polyimide film(2-1) to the surface of the resultant structure.

Description

Printed Circuit Board Lamination Method {METHOD FOR BUILDING LAYER OF PRINTED CIRCUIT BOARD}

The present invention relates to a printed circuit board (PCB) lamination method, and more particularly, to a method for manufacturing a printed circuit board using a new material.

Conventionally, in manufacturing a printed circuit board, after processing a via hole using a drill or a laser, a desmear for cleaning the processed via hole, and the upper and lower copper foils through copper plating The lower copper foil and the upper copper foil were electrically contacted through a combination of several processes such as connection.

In such a conventional printed circuit board manufacturing, via holes are processed using a drill or a laser, which increases the manufacturing time of the product and increases the manufacturing cost. Accordingly, when processing via holes using a drill or a laser, more effective means such as cleaning using plasma for desmear have been sought. But its effectiveness and cost are also not negligible, so its practicality is questioned. In addition, when the desmear is not properly performed, there are many problems such as the electrical contact is not completed or the via hole bursts when a high voltage is applied.

The present invention has been made to solve the above-described drawbacks, and an object thereof is to provide a printed circuit board lamination method for realizing electrical contact between the lower copper foil and the upper copper foil.

1 is a cross-sectional view of the photo-sensitive polyimide film bonded on the lower copper foil after the development after irradiating ultraviolet rays using a photo mask,

Figure 2 is a view showing after bonding the upper copper foil by coating an anisotropic conductor,

3 is a cross-sectional view showing a process of forming a pattern on the upper copper foil,

4 shows the adhesion of photo-sensitive polyimide films.

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

1: lower copper foil

2, 2-1: First and second photo-sensitive polyimide films

3: photo mask 4: ultraviolet

5: polyimide part 6: anisotropic conductor

7: upper copper foil 8: dry film

9: pattern

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

FIG. 1 shows an ultraviolet (4) using a photo mask (3) to a first photo-sensitive polyimide film (2) adhered on a lower copper foil (1). It is a figure which shows the cross section after completion of image development after irradiation. The photo-sensitized polyimide film is classified into positive or negative depending on whether the portion subjected to ultraviolet irradiation is developed or remains. The first photo-sensitive polyimide film 2 is a negative polyimide film. The polyimide portion 5 thus developed serves as a via hole to electrically connect the upper and lower copper foils. When developing, it is common to use a solution containing water, an alkali chemical, an organic solvent, and the like.

2 is a view showing after the anisotropic conductor (ACF) (6) is coated to adhere the upper copper foil (7). Before coating the anisotropic conductor 6, residues remaining on the sidewalls during polyimide film development by cleaning in a mixed gas composed of a gas such as Ar, H2, O2, He, N2, or a single gas can be cleaned. (residue) and organic contaminants are removed and the surface energy of the copper foil is increased to improve the adhesion of the anisotropic conductor 6. The increase in adhesion contributes to improved reliability by increasing the resistance or moisture resistance to the physical stress of the printed circuit board. The anisotropic conductor 6 refers to a mixture of conductive particles, an adhesive polymer, and a diluent. Examples of the anisotropic conductor 6 include silver paste, gold paste, kappa paste, and nickel paste depending on the conductive particles. When the upper copper foil 7 is covered on the surface and pressed using heat and pressure, the upper copper foil 7 adheres to the first photo-sensitive polyimide film 2 and the anisotropic conductor 6. In this case, the pressure and heat applied make physical contact between the conductive particles in the anisotropic conductor 6 and electrically connect the lower copper foil 1 and the upper copper foil 7. When coating the anisotropic conductor 6, a screen printing technique is used to have a convex shape upward to facilitate connection with the upper copper foil 7. The screen printing method includes a silk screen, a metal screen, a metal mask printing method, and the like. The above technique saves cost and time because the via hole processing step, the desmear step using chemicals and the copper plating step can be omitted to electrically connect the upper and lower copper foils 7 and 1 to each other. Makes a great contribution. The use of the polyimide film is suitable for buildup substrates due to its chemical resistance, thermal stability at 300 ° C. or lower, and low dielectric constant (3.2).

3 is a cross-sectional view illustrating a process of forming the pattern 9 on the upper copper foil 7. After coating the dry film 8 on the upper copper foil 7 and performing a photographic process and a developing process using a photo mask corresponding to the pattern 9 formed of the upper copper foil 7, the upper copper foil 7 is selectively It etches to form the pattern 9 which consists of an unremoved part of the upper copper foil 7. Such a process belongs to a widely used printed circuit board manufacturing process, and its technology is widely used. Also in developing the dry film 8, the above-mentioned solution which mixed water, alkali chemicals, an organic solvent, etc. is used.

4 is a view showing adhesion of the second photo-sensitive polyimide film 2-1. Before bonding the second photo-sensitive polyimide film 2-1, cleaning is performed in a mixed gas composed of a gas such as Ar, H 2, O 2, He, N 2, or a plasma composed of a single gas. The organic contaminants remaining on the pattern 9 are removed and the surface energy on the pattern 9 is raised to improve the adhesion of the second photo-sensitive polyimide film 2-1. Therefore, the lifting phenomenon of the second photo-sensitive polyimide film 2-1 in the subsequent developing step is prevented. In addition, the characteristics of the copper foil used in the manufacture of printed circuit boards are one side uneven (roughness) is advantageous for adhesion, while the other side is disadvantageous because there is no such. When the above-mentioned plasma is treated, the other side also has roughness, thereby improving the adhesion of the second photo-sensitive polyimide film 2-1, thereby increasing the reliability of the printed circuit board. After repeating the above-described process it is possible to stack the build-up printed circuit board in a multi-layer.

As described above, the present invention not only does not use a drill or a laser to process the vial hole, but also does not require a wet desmear, thereby reducing manufacturing costs and defects by saving manufacturing cost and time. Plasma is used to bond the anisotropic conductor to the polyimide film, thereby improving the adhesion of the printed circuit board. By using a polyimide film having chemical resistance, thermal stability, and low insulation as the insulating film between the copper foils, the electrical characteristics of the build-up printed circuit board are improved.

Claims (5)

A first step of adhering the first photo-sensitive polyimide film onto the predetermined lower copper foil; A second step of forming a photo mask on the first photo-sensitive polyimide film, and developing after irradiating UV light to selectively form via holes for electrically connecting upper and lower copper foils to the first photo-sensitive polyimide film. ; A third step of performing cleaning; Filling an anisotropic conductor into the via hole; A fifth step of covering and compressing the upper copper foil on the surface such that the upper copper foil adheres to the first photo-sensitive polyimide film and the anisotropic conductor so that the lower copper foil and the upper copper foil are electrically connected; A sixth step of forming a dry film on the upper copper foil; A seventh step of performing a photo process and a developing process by using a photo mask corresponding to the pattern to be formed of the upper copper foil; An eighth step of selectively removing the upper copper foil to form a pattern made of the upper copper foil; A tenth step of performing cleaning; And And an eleventh step of adhering a second photo-sensitive polyimide film to the surface. The method of claim 1, wherein the first photo-sensitive polyimide film is a negative polyimide film. The method of claim 1, wherein the cleaning is performed in a plasma composed of at least one of Ar, H 2, O 2, He, and N 2 gases. The method of claim 1, wherein a screen printing technique is used to form a convex upward shape to facilitate connection with the upper copper foil when forming the anisotropic conductor. The method of claim 1, wherein the pressing is performed by heat and pressure.