JPH05183259A - Manufacture of high density printed wiring board - Google Patents

Abstract

PURPOSE:To obtain a manufacturing method of a high density printed wiring board excellent in reliability wherein plating omission, plating spread, and undercut of solder resist are not generated. CONSTITUTION:In a manufacturing method of a fine printed wiring board of high density wherein resist 1 formed on an insulative board 9 is subjected to chemical plating, the height of a conductor circuit pattern 2 between patterns of the conductor circuit pattern 2 is made a nearly identical surface. After that, the part except the conductor circuit pattern 2 to be subjected to chemical plating is coated with solder resist, and subjected to chemical plating like an Ni-plated film 22 and an Au-plated film 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a high density printed wiring board having a high density and fine conductor circuit pattern.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of electronic equipment, there is an increasing demand for finer and higher density printed wiring boards for mounting the electronic equipment. Conventionally, the above-mentioned printed wiring board is mainly manufactured by the subtractive method because high reliability is required particularly for industrial use. This is because the conductor circuit pattern has high adhesion strength to the insulating substrate. As shown in FIGS. 7 to 11, the subtractive method is a method in which a copper clad laminate 9 having a copper foil 91 is used as a starting material and a copper foil 91 unnecessary as a conductor circuit pattern is partially removed by etching. Is.

That is, as shown in FIG. 7, first, a large number of holes 90 for forming through holes and for positioning are formed in the copper-clad laminate 9 at predetermined locations. Next, as shown in FIG. 8, an etching resist 92 is coated on the surface of the copper-clad laminate 9 other than the portion where the conductor circuit pattern is formed. Next, as shown in FIG. 9, a Cu plating film 93 is formed by electroless plating using a copper chloride solution to form a base of the conductor circuit pattern 900.

As described above, in the subtractive method, the conductor circuit pattern 90 is formed by the steps shown in FIGS.
This is a method of forming 0. Then, as shown in FIG. 10, on the surface of the Cu plating film 93, the photo-developing solder resist 9 is applied to a portion where chemical plating is not applied.
Coat 4. Then, as shown in FIG.
A Ni plating film 95 is applied to the surface of the plating film 93 by chemical plating. Further, an Au plating film 96 is applied to the surface of the Ni plating film 95 by the chemical substitution method and the chemical reduction method.

[0005]

However, the above-mentioned conventional technique has the following problems. That is, the Cu plating film 9
3, the conductor circuit pattern 900 formed of the Ni plating film 95 and the Au plating film 96 has a line spacing of 100.
In the case of high density and fine of less than μm, FIG.
As shown in FIG.

Further, as shown in FIG. 13, a short-circuit portion between adjacent patterns, which is called a plating spread 98, occurs. The plated-off portion 97 and the plated spread 9
No. 8 is considered to be a phenomenon that occurs because it is difficult for the plating solution to flow between the lines because the distance between the lines is 100 μm or less and the pitch is extremely small. On the other hand, in the subtractive method, the solder resist 9
In the upper portion 940, which is the upper portion of the conductor circuit pattern 900, the thickness of the portion 4 is likely to be thin.

However, the developing process for hardening the solder resist 94 is generally performed in conformity with the portion 941 having a large thickness of the solder resist 94, that is, the upper portion other than the conductor circuit pattern. Therefore, in the upper portion 940 on the conductor circuit pattern 900, excessive development may occur and the solder resist 94 may be excessively hardened. As a result, as shown in FIG. 14, an undercut 99 lacking in the lower portion is likely to occur at the boundary end of the solder resist 94.

In addition, under the severe conditions that the liquid temperature for applying the Ni plating film 95 and the Au plating film 96 is relatively high at 80 ° C. to 90 ° C., the undercut 99 of the solder resist 94 is immersed in the plating liquid. There is something that can be seen. As a result, the solder resist 94 may be peeled off one after another as if a wedge was driven in. The present invention has been made in view of the above conventional problems, and provides a method for manufacturing a high-density printed wiring board which is free from plating drop, plating spread, and undercut, and has high density and excellent reliability. Is what you are trying to do.

[0009]

According to the present invention, when a conductor circuit pattern formed on an insulating substrate is chemically plated on the surface of the conductor circuit pattern, a plating resist is coated so as to cover the surface of the conductor circuit pattern. Then, the plating resist in the vicinity of the conductor circuit pattern to be chemically plated is removed to expose the conductor circuit pattern, and the height of the conductor circuit pattern and the plating resist in the exposed portion is made to be substantially on the same plane, and then the chemical plating is performed. The method for manufacturing a high-density printed wiring board is characterized in that

What is most noticeable in the present invention is that the surface of the conductor circuit pattern is covered with a plating resist, and then the plating resist in the portion to be chemically plated is removed to expose the conductor circuit pattern. The heights of the pattern and the plating resist are almost on the same plane, and then chemical plating is performed. As the plating resist, for example, a dry film is used. As a method for removing the plating resist, there is a polishing method using sandpaper, for example.

The conductor circuit pattern is formed of, for example, a Cu plating film by chemical plating or a pattern plating film using solder by a solder peeling method. Further, as the insulating substrate, for example, a glass epoxy substrate reinforced with glass fiber or a copper foil laminated substrate is used. Further, in forming the Cu plating film by chemical plating on the surface of the glass epoxy substrate for forming the conductor circuit pattern, for example, an additive method is used. This additive method is performed by applying an epoxy resin adhesive having excellent heat resistance and electrical insulation to the surface of an insulating substrate such as a glass epoxy substrate. After that, the epoxy resin adhesive is roughened to form an anchor. After roughening, the catalyst is applied to the surface. After that, the plating resist is applied as described above, and the Cu plating film, Ni plating film,
Chemical plating such as Au plating film is formed.

[0012]

In the present invention, between the adjacent conductor circuit patterns, a plating resist having the same height as that of the conductor circuit patterns is coated (see FIG. 3). Therefore, when chemical plating is performed on the conductor circuit, neither plating drop nor plating spread occurs between adjacent conductor circuit patterns, and no undercut occurs (see FIG. 6). The reason why the plating drop and the plating spread do not occur is that the chemical plating does not spread in the lateral direction because the plating resist is formed between the conductor circuit patterns to almost the same surface as the conductor circuit patterns.

The reason why the undercut does not occur is as follows.
Since the plating resist is formed between the conductor circuit patterns on the same surface as the conductor circuit patterns, it is possible to make the thickness of the solder resist covering the portions not subjected to chemical plating uniform (see FIGS. 4 and 5). Also, with these,
It is possible to form a conductor circuit pattern having high density and excellent reliability. As described above, according to the present invention, it is possible to provide a method for manufacturing a high-density printed wiring board that is free from plating drop, plating spread, and undercut, and has high density and excellent reliability.

[0014]

EXAMPLE A method for manufacturing a high-density printed wiring board according to an example of the present invention will be described with reference to FIGS. In this example, first, as shown in FIG. 1, a conductor circuit pattern 2 formed on an insulating substrate 9 is subjected to chemical plating on the surface of the conductor circuit pattern 2 to obtain a high density and fine printed wiring board. Is manufactured. First, the outline thereof will be described. As shown in FIG. 2, the insulating substrate 9 is coated with the plating resist 1. A Cu plating film 21 is formed on this, and as shown in FIG. 4, a printed wiring board in which the height of the conductor circuit pattern 2 and the plating resist 1 are substantially on the same plane is formed by the additive method as in the conventional case.

Then, as shown in FIGS. 4 and 5, a portion other than the conductor circuit pattern 2 to be chemically plated is covered with the solder resist 3, and then the Ni plating film 22,
The Au plating film 23 is chemically plated. In this way, the high-density printed wiring board shown in FIG. 1 is obtained. Here, it should be noted that the distance between lines of the conductor circuit pattern 2 is about 50 to 60 μm, which is dense and fine.

The conductor circuit pattern 2 has a Cu plating film 21 formed by chemical plating as shown in FIG.
It is composed of a Ni plating film 22 and an Au plating film 23. The Cu plating film 21 has a film thickness of about 30 μm. The Ni plating film 22 has a film thickness of about 5 μm. The Au plating film 23 has a film thickness of about 0.5.
μm.

Next, a method for manufacturing the above-mentioned high-density printed wiring board will be specifically described with reference to FIGS. First, the Cu plating film 21 is formed on the insulating substrate 9 by an additive method as shown in FIG. That is, the additive method uses the insulating substrate 9 made of a glass epoxy substrate having no copper foil on the surface. Then, an epoxy resin adhesive (not shown) having excellent heat resistance and electrical insulation is first applied to the surface of the insulating substrate 9. Then, this is heated and cured.

Next, the epoxy resin adhesive is roughened to form an anchor. Next, an activation treatment (not shown) is performed on the surface of the roughened epoxy resin adhesive using a hydrochloric acid palladium solution. After that, as shown in Figure 2,
Conductor circuit pattern 2 is formed on the insulating substrate 9 by chemical plating.
The Cu plating film 21 serving as the basis of is formed. next,
The plating resist 1 is coated so as to cover the surface of the circuit pattern 2 including the Cu plating film 21.

As the plating resist 1, a permanent resist type dry film is used. The plating resist 1 has a thickness of about 40 μm and is flexible. Next, as shown in FIG. 4, the plating resist 1 near the conductor circuit pattern 2 to be chemically plated is removed to remove the conductor circuit pattern 2
Expose the surface of. The heights of the conductor circuit pattern 2 and the plating resist 1 in the exposed portion are substantially flush with each other.

As a means for exposing the conductor circuit pattern 1, first, a polishing process using sandpaper is used. Next, as a means for making the heights of the conductor circuit pattern 2 and the plating resist 1 substantially flush with each other, polisher processing is used. Next, as shown in FIG. 4, portions other than the conductor circuit pattern 2 to be subjected to chemical plating are covered with a solder resist 3. The solder resist 3 is made of a photo-developing photocurable resin. Therefore, the solder resist 3 is exposed and developed and cured.

Thereafter, as shown in FIG. 5, a Ni plating film 22 is first applied by chemical plating on the surface of the Cu plating film 21 in the portion to be chemically plated. Ni plating film 22
In applying, the temperature of the plating solution is adjusted to 80 ° C. and the pH is adjusted to 4. Then, an Au plating film 23 is chemically plated on the Ni plating film 22. The Au plating film 23 is formed by a chemical substitution method and a chemical reduction method. The chemical replacement method is performed by adjusting the temperature of the plating solution to 90
The temperature is adjusted to ℃ and the pH is adjusted to 4. The chemical reduction method is performed by adjusting the liquid temperature to 75 ° C and the pH to 13.

Next, the function and effect will be described. In this example, as shown in FIG. 4, a space between the adjacent conductor circuit patterns 2 is covered with a plating resist 1 whose height is substantially the same as that of the conductor circuit patterns 2. Therefore, as in the conventional case, plating is dropped between the adjacent conductor circuit patterns 2,
There is no plating spread and undercut (Fig. 6). Here, in FIG. 6, in the conductor circuit pattern 2,
It shows a state in which the surface of the portion not subjected to chemical plating is covered with the solder resist 3.
Undercut does not occur in the solder resist 3.
The reason why the above-mentioned plating drop and plating spread does not occur is that the plating resist 1 is formed between the conductor circuit patterns 2 made of the Cu-plated film 21 formed by the additive method up to almost the same surface as the conductor circuit patterns 2 (FIG. 3) Therefore, even if chemical plating is formed, these do not spread in the lateral direction.

The reason why the undercut does not occur is that the plating resist 1 is formed between the conductor circuit patterns 2 on the same surface as the conductor circuit patterns 2 as shown in FIG. Therefore, the thickness of the solder resist 3 covering the portion of the conductor circuit pattern 2 that is not subjected to chemical plating can be made uniform. Further, by these, it is possible to form a high-density and highly reliable conductor circuit pattern. In forming the Cu plating film 21, an epoxy resin adhesive having excellent heat resistance and electrical insulation is used. Therefore, the electrical insulation between the conductor circuit patterns 2 is excellent, and high reliability is obtained. Further, the adhesion strength of the Cu plating film 21 is stable even at high temperature, and the heat resistance is excellent.

Further, as shown in FIG. 3, since the plating resist 1 and the conductor circuit pattern 2 have substantially the same height, the conductor circuit pattern 2 has excellent flatness and is most suitable for high-density surface mounting. .. As described above, according to this example, as shown in FIG. 1, high density and fine reliability are excellent.
A high-density printed wiring board can be obtained. The Cu plating film 21 formed by the additive method may be replaced by a pattern plating film using solder by a solder peeling method.

[Brief description of drawings]

FIG. 1 is a cross-sectional view taken along the line AA of FIG. 5, showing a cross section of a high density printed wiring board according to an example.

FIG. 2 is a perspective view showing a conductor circuit pattern formed on an insulating substrate in the example.

FIG. 3 is a perspective view showing a state in which the plating resist and the conductor circuit pattern have substantially the same height in the embodiment.

FIG. 4 is a perspective view showing a state in which a solder resist is coated on the surface of a conductor circuit pattern that is not subjected to chemical plating in the example.

FIG. 5 is a perspective view showing a state in which a chemical plating film is applied to the surface of the conductor circuit pattern in the example.

FIG. 6 is a perspective view showing a state in which the surface of the conductor circuit pattern is covered with a solder resist in the example.

FIG. 7 is a perspective view showing a state in which a hole is formed in an insulating substrate in a conventional example.

FIG. 8 is a perspective view showing a state in which an insulating substrate is covered with an etching resist in a conventional example.

FIG. 9 is a perspective view showing a state in which a conductor circuit pattern is formed on an insulating substrate in a conventional example.

FIG. 10 is a perspective view showing a state in which a conductor resist pattern is coated on a conductor circuit pattern in a conventional example.

FIG. 11 is a perspective view showing a state in which a chemical plating film is formed on the surface of a conductor circuit pattern in a conventional example.

12 is a cross-sectional view taken along the line BB of FIG.

13 is a cross-sectional view taken along the line CC of FIG.

14 is a cross-sectional view taken along the line DD of FIG.

[Explanation of symbols]

 1. ． ． Plating resist, 2. ． ． Conductor circuit pattern, 20. ． ． Exposed part, 21. ． ． Cu plating film, 22. ． ． Ni plating film, 23. ． ． Au plating film, 3. ． ． Solder resist, 9. ． ． Insulating substrate,

Claims (1)

[Claims] 1. When a conductor circuit pattern formed on an insulating substrate is chemically plated on the surface of the conductor circuit pattern, a plating resist is coated so as to cover the surface of the conductor circuit pattern, and then chemical plating is performed. Characterized by removing the plating resist in the vicinity of the conductor circuit pattern to be exposed to expose the conductor circuit pattern, and making the height of the conductor circuit pattern and the plating resist in the exposed portion almost the same surface, and then performing chemical plating And a method for manufacturing a high-density printed wiring board.