JPS5823493A - Method of producing high density printed circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a high-density printed wiring board, and more particularly, to a printed wiring board having a signal line width of 100 μm or less and having through-holes formed on both sides of the board. This invention relates to a method for manufacturing a board.

In recent years, there has been a growing demand for higher circuit density in printed wiring. The increasing density of printed circuits is accompanied by the miniaturization of circuit patterns formed on wiring boards, the multilayering of wiring boards, and the mixing of layers with through holes and layers without through holes at the same lattice point on multilayer wiring boards. Advanced technology such as the use of a wiring board with a multiple through-hole structure that matches the design is essential. In particular, the adoption of this multiple through-hole structure helps to suppress the increase in multilayers compared to the conventional through-hole method, and is an effective means for obtaining a high-density printed circuit board with stable quality. I can say that.

A conventional method for manufacturing a printed wiring board having plated through holes necessary for manufacturing a multilayer wiring board having such a multiple through hole structure will be described with reference to FIG.

FIG. 1 is a schematic diagram showing a conventional manufacturing process of a printed wiring board having plated through holes.

Refer to the same figure. First, as shown in FIG. 1K), a through hole 1 is formed in a copper clad laminate. Note that in the figure, the shaded area represents the steel plate. Next, as shown in FIG. 1←), a film-like photosensitive resin 2 is laminated to close the through hole. Next, as shown in the first wJ (c), the signal line pattern 3 and the land pattern 4 are printed and developed on the film-like photosensitive resin 1 using a photographic method. Thereafter, by using an etching liquid, a printed wiring board 5 having desired printed circuits formed on the front and back surfaces of the copper-clad laminate is obtained as shown in FIG.

In the above-mentioned conventional manufacturing process of 1 m, a film-like material is used as the photosensitive resin 2, but the circumference of the through-hole 1 is l! When forming the land pattern /4, the through hole 1 can be covered by the film, so that in the subsequent etching process, the etching solution will penetrate into the through hole and damage the copper plating in one hole. This is because it can prevent this from happening.

After stacking and laminating multiple double-sided printed wiring boards manufactured in this manner, drilling, copper plating, and photo-etching are performed. A wiring board can be obtained. Although only one intermediate layer with through holes 1 is shown in FIG. 2, there are often multiple intermediate layers alternating with, for example, intermediate layers without through holes. It is called.

Now, the recent demand for higher circuit densities in printed wiring boards has led to demands for further miniaturization of printed circuits even in printed wiring boards having the above-mentioned multiple through-hole structure.

By the way, the photosensitive resin 2 in the form of a film is generally thick, so as explained with reference to Figure 1, if the circuit pattern is printed and developed using the photographic method, the thicker the film. As a result of thicker layers, the state of diffraction and scattering of light spreads between them, resulting in a deterioration in the resolution of the completed circuit pattern, making it difficult to obtain finely detailed printed circuits. Therefore, if we try to improve the resolution of the circuit pattern by using a photosensitive resin with as thin a film as possible, the mechanical strength of the film becomes weak, so during the etching process, the film thickness is broken and the etching solution penetrates into the through-holes. This results in the inconvenience of damaging the copper plating inside the through hole.

For this reason, there are commercially available photosensitive resins with a thickness of 17 μm and 11 degrees, but due to the mechanical strength mentioned above,
A photosensitive resin with a thickness of 300 degrees is used.

On the other hand, a ζ liquid photosensitive resin, which is a film-like photosensitive resin, is known. When using this liquid photosensitive resin, the thickness is 6jm.
@! Since it can be applied as thinly as K, the resolution of the circuit pattern can be increased accordingly and a finer printed circuit can be formed.

However, with the method of applying liquid photosensitive resin, unlike the case of using a film, it is impossible to prevent the etching liquid from penetrating into the through hole when the etching liquid is applied. be. One of the conventional techniques to solve this difficulty is to use copper-clad lamination (a bale with a thin coating of K liquid photosensitive resin to form a circuit pattern with high resolution), and a through-hole that is filled with tines to prevent the etching solution. A construction method has been announced to prevent damage from occurring even if water intrudes. However, when this method is adopted, problems arise in the adhesion between the adhesive and the surface of the circuit pattern in the subsequent lamination adhesion stage, and in turn, in the heat resistance of the printed wiring board. Therefore, it may be possible to chemically remove the tin film after etching, but this would complicate the manufacturing process and result in unstable quality. Although other conventional methods are often adopted to solve the above-mentioned problems, there is a particular difficulty in fitting the shoulders of the through-holes, and it is also difficult to obtain stable quality.

The present invention was made in consideration of the above-mentioned conventional technical circumstances, and therefore, an object of the present invention is to improve the resolution of circuit patterns by using a liquid photosensitive resin, thereby making it possible to form more detailed printed circuits. In addition, a new high-density printed layout is used to prevent the etching solution from entering the through-holes during the etching process.
The purpose of this invention is to provide a method for manufacturing the same.

The main points of the present invention are as follows.

After applying a thin layer of liquid photosensitive resin to the surface of the wrinkled laminate in a steel-clad laminate having through-holes, a desired signal line pattern is formed on the resin using a high-density Kfi method using a photographic method.
The pattern is developed, and then a relatively thick film-like photosensitive resin is laminated on top of the developed signal line pattern to close the through hole, and the desired through hole is formed in the tree 11 by the same method. Print and develop the land pattern, and make sure that the through holes are closed.
Etching is performed in a state where the etching solution does not enter inside the hole, and then the liquid and the developed pattern of the film-like photosensitive resin are removed. pudding) 1
The point is that it made it possible to form circuits.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1113 is a schematic diagram showing a manufacturing process as an example of the present invention. Now, after drilling a small hole of 0.4 mmφ at a predetermined position in a copper-clad laminate 6 made by laminating 18 μm copper foil on both sides of a glass epoxy base material of thickness Q and 1 mm, pot plating is applied to the substrate. A through hole 7 is formed in a thickness of 20 to 25 μm on the entire surface of the substrate, and then a commercially available liquid photosensitive resin 8 is applied to a thickness of 1 to 3 μm on both sides of the substrate.
A structure as shown in Figure (a) is obtained.

Next, a signal line pattern 9 with a width of 100 μm constituting the printed circuit is formed by printing and developing on the photosensitive resin out of the desired printed circuit pattern using a commonly used photographic method. A structure as shown in b) is obtained. Next, the base 11 having the signal line pattern 9 has a thickness of 18 to 50 μm, which is generally commercially available.
A film-like photosensitive resin 111O is laminated and the through holes are closed to obtain a structure as shown in FIG. A square land pattern 11 is formed above and below the through hole 7 by baking a film of photosensitive resin to obtain a structure as shown in FIG. Thereafter, the copper in the areas other than the photoresist patterns 9 and 11 is dissolved by a commonly used etching method, and the photoresist is removed by a well-known method such as methylene chloride to form a desired high-density printed circuit. A printed wiring board with through holes is obtained as shown in FIG. 3(E).

The circuit density of the printed wiring board manufactured by Honyo Jl1 Example was as follows: the spacing between the through holes arranged in a lattice pattern was 1.27 mm, the land diameter was 0.7 mm2, and the signal line width was 0.7 mm. l mm, the circuit conductor spacing is 0.1 mmn1 between land and signal line, and 0.1 between signal line and signal line.
7 mm, through-hole k % 0.35 mm (after copper plating →) Compared to conventional printed circuits, the manufacturing method of the present invention is sufficient for future circuit miniaturization. It has the ability to obtain stable quality.

As described above, the present invention takes advantage of the fact that one step of the conventional method of forming a printed circuit with through-holes using only a photographic method using a commonly used film-like photosensitive resin is not complicated. The present invention solves the difficulty of achieving stable quality of printed circuits using a film-like photosensitive resin due to its resolution by employing a liquid photosensitive resin with excellent resolution. Line width 100μm or less, conductor spacing 100μm
It has the advantage of being able to provide the following printed circuits with high-density through holes with stable quality.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a conventional manufacturing method of a printed wiring board having through-holes, FIG. 112 is a cross-sectional view of a multi-through-hole printed wiring board, and FIG. FIG. Symbol explanation 1...Through hole, 2...Film-like photosensitive resin,
3... Signal line pattern, 4... Land pattern J-7
,)-v,,, ::, 5 °2"')ffil
・6-111151111M-11jL・°°°“-Hole, 8...Liquid photosensitive resin, 9...Signal line pad $
-7,10...Film-like 11s'Jt@M, 1
1...2nd pattern agent Patent attorney Akio Namiki #11 Figure 112

Claims (1)

[Claims] 1) A method for manufacturing a high-density printed wiring board, in which a liquid photosensitive resin is applied thinly to both surfaces of a steel-clad laminate having plated through holes, and then a desired signal is applied to the resin using a photographic method. The first step is to develop the line pattern with high density, and then to line the developed signal line pattern with a relatively thick film-like photosensitive resin to close the through holes. [In order to close the holes and print the desired land pattern, there is a second step of development, and etching is carried out in a state where the etching solution does not enter into the through holes because they are blocked. A method for manufacturing a high-density printed wiring board, comprising the steps of step 3 and then a fourth step of removing the liquid and the draft pattern of the film-like photosensitive resin.