JP2621293B2 - Printed circuit board manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a printed circuit board which is particularly suitable for obtaining a flexible printed circuit board having a laminated structure of a plurality of conductive patterns.

[Summary of the Invention]

The present invention provides a substrate in which a first conductive thin film and a second conductive thin film are formed on both surfaces of an insulating substrate, for example, a flexible insulating film, and a through hole is formed in a predetermined portion of the first conductive thin film. Then, a through-hole for leaving a second conductive thin film in the insulating substrate through the through-hole, that is, a so-called blind through-hole is formed, and then a conductive layer is deposited in the blind through-hole. And a second conductive thin film is patterned to form first and second conductive patterns, and predetermined portions of these patterns are electrically connected to each other by the conductive layer in the blind through hole described above to form a predetermined circuit. The basic procedure is to obtain a flexible printed circuit board having first and second conductive patterns on which are formed, for example, a flexible printed circuit board having a laminated structure of four conductive patterns. To be able to improve the simplification of the process and the yield in the case of obtaining the Le PCB.

[Conventional technology]

As a conventional method of obtaining a flexible printed circuit board having a structure in which a plurality of conductive patterns of, for example, four layers are stacked,
As shown the process diagram in Figure 3, first, for example, FIG. 3 A ₁
As shown in (1), a substrate provided with a first conductive thin film (11) and a second conductive thin film (12) each having copper foil or the like adhered to both sides of a flexible insulating film, for example, 2) is prepared. Then, for example, the second conductive thin film (12) is patterned into a required pattern by photoetching to form a second conductive pattern (22), and a through-hole, that is, a through-hole is formed at a predetermined position on the substrate (2). (3) is drilled.

Then, a conductive layer (4) is formed in the through-hole (3) by, for example, electroless plating and electroplating in the through-hole (3) to form a second conductive pattern (22) in the first hole. Electrically connected to a predetermined portion of the conductive pattern (21). Meanwhile, the substrate in which the third conductive thin film (13) and the fourth conductive thin film on both surfaces (4) is deposited in FIG. 3 A ₂ are shown as similar insulating base (1) i.e. a flexible insulating film (2 ), And the third conductive thin film (13)
Then, for example, photoetching is performed to form a third conductive pattern (23) having a required pattern.
On the other hand, bored the substrate (2) through holes (3) with respect to the predetermined portion, the conductive layer in the through-hole as shown in Fig B ₂ (3) (4) likewise example No A third conductive pattern (2) formed by electrolytic plating and electroplating
3) is electrically connected to a predetermined portion of the fourth conductive thin film (14).

The thus third each substrate shown in FIG. B ₁ and B ₂ (2), as shown in FIG. 3 C, the second conductive patterns respectively patterned with (22) a third conductive The two substrates (2) are press-bonded with a resin adhesive (5) such as a prepreg so that the patterns (23) are opposed to each other with the pattern (23) inside, and the two substrates (2) maintain a predetermined positional relationship with each other.
A united substrate (6) is obtained.

Next, as shown in FIG. 3D, a through hole (7) penetrating through the united substrate (6) is formed at a predetermined portion of the united substrate (6).
In the through hole (7), for example, electroless plating and further electroplating are applied to form a conductive layer (8). On the other hand, the first and fourth conductive thin films (11) and (14) facing both surfaces of the united substrate (6) are subjected to, for example, photoetching to form a predetermined pattern to form first and fourth conductive thin films (11) and (14) each having a required pattern. Fourth conductive patterns (21) and (24)
To form

By doing so, the first to fourth conductive patterns (21)
To (24) are stacked, and the first and second conductive patterns (2
1) and (22), and between the third and fourth conductive patterns (23) and (24) through the through hole (3), respectively, and the conductive layer (4) formed in the through hole (3). ), The predetermined portions are electrically connected to each other, and the first and fourth conductive patterns (21) and (24) are formed in the through-hole (7) through the through-hole (7). According to 8), a flexible printed board (9) having a structure in which four layers of conductive patterns whose predetermined portions are electrically connected to each other is laminated is obtained.

However, in such a case, FIG. 3 B ₁ and B ₂
As shown in FIGS. 3D and 3D, three through-hole platings of the conductive layers (4) and (8) for each of the through-holes (3) and (7) are required, which leads to an increase in cost. Also, as shown in FIG. 3C, when the two substrates (2) are overlaid and heated and pressed by an adhesive (5), that is, a prepreg, the substrate (2) is actually extremely thin. This adhesive overflows on both sides of the united substrate (6) through the through hole (3), and requires an operation for removing the overflowed adhesive.
There are problems such as a complicated printed circuit board manufacturing operation and a relatively high incidence of defective products.

As another method, there has been proposed a method whose manufacturing process is shown in FIG. In this case, as shown in FIG. 4A, the second and third conductive thin films (12) and (1) are formed on both surfaces of an insulating base (1) made of a flexible insulating film.
3) For example, a copper foil is deposited, and this is patterned into a required pattern, for example, by photo-etching to form second and third conductive patterns (22) and (23).

Next, as shown in FIG. 4B, the conductive pattern (22)
The first and fourth conductive thin films (11) and (14), also made of copper foil or the like, are applied to both surfaces of the substrate (1) having (23) and (23) via an adhesive (5), for example, a prepreg.

Next, as shown in FIG. 4C, only the first conductive thin film (11) and the adhesive (5) thereunder penetrate from the first conductive thin film (11) side to a predetermined portion thereof. A so-called blind through hole (3b) is formed by machining such as a drill in a state where the third conductive pattern (23) below is left. On the other hand, in the same manner, the third conductive thin film (14)
Similarly, a blind through hole penetrating only a predetermined portion of the conductive pattern (23) through only the fourth conductive thin film (14) and the adhesive (5) interposed between the fourth conductive thin film (14) and the third conductive pattern (23) Drill (3b). On the other hand, a through-hole (7) extending from the first conductive thin film (11) to the fourth conductive thin film (14) is similarly formed in a predetermined portion by machining.

Thereafter, as shown in FIG. 4D, electroless plating and electroplating are performed including the inside of each blind through-hole (3b) and through-hole (7) to form conductive layers (4) and (8), respectively. I do.

Next, as shown in FIG. 4E, the first and fourth conductive thin films (11) and (14) are subjected to, for example, photoetching to form required patterns to form first conductive patterns (11) and (14). 21) and a fourth conductive pattern (24) are formed.

According to such a method, the first to fourth conductive patterns (21) to (24) are stacked, and the first conductive pattern (21) is formed.
And a second conductive pattern (22), and a third conductive pattern (23) and a fourth conductive pattern (24) by a conductive layer (4) formed in a blind through hole (3b). A first conductive pattern (21) and a fourth conductive pattern (24) electrically connected at a predetermined portion;
Through this through hole (7)
First to fourth four-layer conductive patterns (21) to (4) in which predetermined portions are electrically connected by a conductive layer (8) formed therein.
A flexible printed board (9) on which (24) is laminated is configured.

However, in the case of using such a method, it is technically necessary to form a blind through hole (3b) by a drill while leaving the second and third conductive patterns (22) and (23) inside. However, there is a problem that the skill is high and the incidence of defective products increases.

[Problems to be solved by the invention]

The present invention solves the above-mentioned problems of the incidence rate of defective products and the problem of workability, adopts a simple process in mass production, and has a high yield, and a printed circuit board, particularly a multilayer structure in which conductive patterns are formed in two or more layers. And a method of manufacturing a printed circuit board that can obtain a flexible printed circuit board.

[Means for solving the problem]

As shown in the process diagram of FIG. 1, first, as shown in FIG. 1A, first and second conductive thin films (41) are provided on both sides of an insulating substrate (31), for example, a flexible insulating film.
And a substrate (32) on which (42) is attached.

Then, as shown in FIG. 1B, a first conductive thin film (41)
Then, a through hole (41h) is formed in a predetermined portion by photo etching or the like.

Next, as shown in FIG. 1C, a polar solvent of a second iron chloride, such as a polar solvent, is applied to the substrate (31) through the through holes (41h) of the first conductive thin film (41), ie, using the first conductive thin film as a mask (resist). , A methylene chloride, or N-methylpyrrolidone to form a through hole (31h), and a second conductive thin film (4
In the state where 2) is left, that is, one end is closed by the thin film (42) to form a blind through hole (51) by the through holes (31h) and (41h).

Blind through hole (51) as shown in FIG. 1D
In particular, a conductive layer (34) is applied at least in the through hole (31h) of the insulating base (31).

Next, as shown in FIG. 1E, the first and second conductive thin films (41) and (42) are patterned at the same time by, for example, photoetching or by another process, respectively, to thereby form the first and second conductive thin films. Patterns (61) and (62)
To form According to such a configuration, the first conductive pattern (61) and the second conductive pattern (62) are formed in the blind through hole (51), that is, in the through hole (31h) of the insulating base (31). A flexible printed board (73) having a two-layer structure in which predetermined portions are electrically connected by the conductive layer (34) thus obtained is obtained.

[Action]

According to the above-described method of the present invention, one of the first conductive thin film (41) and the second conductive thin film (42) formed on each surface of the insulating base (31) is applied to the first conductive thin film (41). A hole (41h) is formed in the base (31) using the mask as a mask.
In this method, the blind through-holes can be easily formed, and in particular, the method of the present invention, as will be apparent from the description below, is to print a conductive pattern exceeding two layers, for example, a four-layer conductive pattern. When applied to obtain a substrate, it is possible to particularly simplify the work process and reduce the incidence of defective products.

〔Example〕

First, an example of obtaining a flexible printed circuit board with a two-layered conductive pattern according to the present invention will be described in detail with reference to FIG. 1 again. In this case, as shown in FIG. 1A, for example, a heat-fusible resin having a thickness of 25 μm or more but having high flexibility, for example, a 25 μm-thick film of polyether sulfone (PES) or a polyimide, polyetherimide, Insulating substrate made of similar insulating film made of polyethylene ether imide etc. (31)
A copper foil specified by the standard of, for example, 35 μm or 18 μm on each surface by thermocompression bonding, or a first and second conductive layer made of a copper thin film by electroless plating and electroplating. The thin films (41) and (42) are applied to obtain a substrate (32).

Next, as shown in FIG.
A 0 μm through hole (41h) is formed by photoetching the first conductive thin film (41).

As shown in FIG. 1C, using the first conductive thin film (41) as a mask, the insulating substrate (31) exposed through the through hole (41h) is chemically etched, for example, by ferric chloride, methylene chloride, N- Spray a polar solvent such as methylpyrrolidone to form a perforated hole (31h) that matches the perforated hole (41h).
The conductive thin film (42) is left, thereby forming a blind through hole (51) whose one end is closed.

Next, as shown in FIG. 1D, for example, copper is used to cover the inner peripheral surface of the through hole (31h) exposed in the blind through hole (51) or to bury the inner surface. Conductive layer by electrolytic plating and electroplating (34)
To adhere.

As shown in FIG. 1E, the first and second conductive thin films (41) and (42) formed on both surfaces of the substrate (32) are each subjected to a predetermined patterning by photoetching, and the first and second conductive thin films (41) and (42) are respectively subjected to the first pattern. And a second wiring pattern, that is, conductive patterns (61) and (62) are formed. In this case, when the conductive layer (34) has the same etching property with respect to the same material or the same etching liquid as the first conductive thin film (41), photo-etching is performed on the conductive layer (34) and the first conductive thin film (41). Although it can be performed at the same time, when the conductive layer (34) is a conductive film different from the first conductive thin film (41), unnecessary portions are removed by etching in a separate step. Further, the patterning, that is, the photoetching for the first and second conductive thin films (41) and (42) can be performed simultaneously as described above, but can also be performed in separate steps.

In the example described above, the printed circuit board (7) having the two-layer structure of the first and second conductive patterns (61) and (62) is used.
Although the case of obtaining 3) has been described, the present invention can be applied to the case of obtaining a printed board having a four-layer structure using the first to fourth conductive patterns. An example of this case will be described with reference to FIG. In this case, to prepare two substrates according to Figure 2 A ₁ and A ₂ (32 ₁₎ and (32 _2). These substrate (32 ₁₎ and (32 _2), which can take the same structure as the substrate described in Figure 1 A, respectively (32), Figure 2 A ₁
1 and ₂ corresponding to FIG. 1A are denoted by the same reference numerals, and redundant description is omitted.

As shown the second in FIGS. B ₁ and B _2, performs bored through holes (41h) by photo-etching respective predetermined positions with respect to the first conductive thin film (41). Then, in this case, the second conductive thin film (42) is subjected to a predetermined patterning by photo-etching into a predetermined pattern, respectively, and the second conductive thin film (42) is formed on the substrate (32 ₁ ) by the second conductive thin film (42). A second conductive pattern (62) is formed, and a second conductive thin film (4) is formed on the second substrate (32 ₂ ).
2) to form a third conductive pattern (63).

Next, as shown in FIG. 2C, both substrates (32 ₁ ) and (3
2 ₂ ) to the second and third conductive patterns (62), respectively.
The substrates (32 ₁ ) and (32 ₂ ) are overlapped with a predetermined positional relationship so that they face each other with (63) inside, and an adhesive (35), for example, glass fiber impregnated with an epoxy adhesive between the two. Thermocompression bonding is performed with the epoxy prepreg interposed therebetween, and this is cured to obtain a united substrate (36).

As shown in FIG. 2D, each of the substrates (32 ₁ ) and (32 ₂ ) arranged on both sides of the united substrate (36) passes through the through hole (41h) of each first conductive thin film (41). Insulating base (3
For 1), a solvent capable of dissolving this is sprayed in the same manner as described with reference to FIG.
1h) is formed to form a blind through hole (51) closed by the second and third conductive patterns (62) and (63), respectively. Next or before that, a through hole (52) is drilled through a united substrate (36) at a predetermined portion by machining such as a drill.

Next, as shown in FIG. 2E, a conductive layer (34) is formed in the blind through hole (51) and the through hole (52) by, for example, electroless plating and electroplating of copper.

As shown in FIG. 2F, both substrates (32) of the united substrate (36)
_{The first} conductive thin film (41) on both outer surfaces of ₁ ) and (32 ₂ ) is patterned by photo-etching or the like in the same step or a different step as the conductive layer (34), respectively.
The first and fourth conductive thin films (41) on the substrates (32 ₁ ) and (32 ₂ ) form patterned first and fourth conductive patterns (61) and (64), respectively. In this way, the first to first
A printed board (73) having a structure in which the fourth conductive patterns (61) to (64) are stacked is obtained. The printed circuit board (73) formed in this way is a first conductive pattern (61).
And a second conductive pattern (62), and a third conductive pattern (63) and a fourth conductive pattern (64) formed in a blind through hole (51).
4), the first conductive pattern (61) and the fourth conductive pattern (64) are connected to the predetermined pattern by the conductive layer (34) in the through hole (52). A required circuit pattern is formed.

〔The invention's effect〕

As described above, according to the present invention, in the case of obtaining a printed circuit board having a laminated structure of a multilayer conductive pattern such as a four-layer structure, the through-hole in which the adhesive (35) overflows outside the united substrate (36). Since the drilling of the holes is avoided, it is possible to avoid the operation of removing the overflowed adhesive or the occurrence of defective products due to this.

The blind through-hole is formed by forming a through hole (41h) in one conductive thin film (41) of the insulating base (31), and using the thin film (41) as a mask to form the base (31) with the solvent. The hole (31h) is formed by removing the hole (31h) with a solvent that does not etch the thin film (41), in other words, does not etch the second conductive thin film (42). Since the second thin film (42) is used, the blind through-hole (51), one end of which is closed, can be easily mass-produced. And a method for manufacturing a printed circuit board.

[Brief description of the drawings]

FIG. 1 is a process chart of an example of the method of the present invention, FIG. 2 is a process chart of another example of the method of the present invention, and FIGS. 3 and 4 are process diagrams of the conventional method. (31) is an insulating base, (41) and (42) are first and second conductive thin films, and (61) to (64) are first to fourth conductive patterns.

Claims (1)

(57) [Claims] A first conductive thin film and a second conductive thin film are provided on both main surfaces of an insulating base.
Forming a through hole in a predetermined portion of the first conductive thin film of the substrate having the conductive thin film; and using the first conductive thin film as a mask to expose the insulating substrate exposed through the through hole to a second layer of a polar solvent. Forming a through hole using any one of iron dichloride, methylene chloride, and N-methylpyrrolidone; and electrically connecting the first and second conductive thin films in the through hole of the insulating base. A method for manufacturing a printed circuit board, comprising: a step of applying a conductive layer to be connected; and a patterning step of selectively removing the first and second conductive thin films to form a required pattern.