JPH0239594A - Manufacture of flexible rigid wiring board - Google Patents

Abstract

PURPOSE:To reduce the cost of a product by forming a dry film photoresist on a part of a flexible board except a junction with a rigid board before thermally press-bonding, thermally press-bonding the flexible board to the rigid board, forming a through hole thereat, and then removing the photoresist. CONSTITUTION:A dry film photoresist 11 is formed to cover the terminals 10 of rear and front faces of a flexible board 1 exposed from a through hole 6 and the surface of a film coverlay 8. Then, a conductive foil 4, a rigid board 3, an adhesive sheet 5, a film coverlay 8, a wiring pattern 2 are formed and a through hole 13 passing the board 1 are formed by drilling. Further, a plated layer 14 for electrically connecting the foil 4 of the board 3 to the pattern 2 of the board 1 is formed on the inner face of the hole 13, the foil 4 is pattern- etched, and the wiring pattern 4A of the board 3 is formed. When the through hole plating and the circuit pattern etching are completed, the photoresist 11 is isolated with a solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing a rigid-flexible wiring board having a structure in which a rigid substrate and a flexible substrate are connected.

<Prior art> -JIIQ flexible wiring boards have the advantage of being able to be wired in any direction due to their flexibility, but
Because of its thinness, mounting of electronic components is complicated and the types of electronic components that can be mounted are limited, for example, dip-type (insertion-type) electronic components used in rigid wiring boards cannot be used.

For this reason, a rigid-flexible wiring board is used, which has a structure in which a rigid board with an excellent function for mounting electronic components and a flexible board for wiring are connected. FIG. 4 shows the structure of this rigid-flexible wiring board, in which a portion of the flexible substrate 1 is sandwiched between two rigid substrates 3.

FIG. 5 shows the materials constituting this rigid-flexible wiring board and the method of laminating them.

Two adhesive substrates 3 having a conductive foil 4 formed on the entire surface of one side are stacked with the conductive foil 4 on the outside so as to sandwich a flexible substrate 1 via an adhesive sheet 5, and the whole is bonded by thermocompression.

In this case, a film coverlay 8 that covers the wiring pattern 2 is laminated on the flexible substrate 1 in advance, and this film coverlay 8 covers the terminal portion 1 of the flexible substrate 1.
A through hole 9 is formed to expose 0 to the outside. Further, through holes 6 and 7 are formed in the rigid substrate 3 and the adhesive sheet 5 for forming a portion 1a (FIG. 4) of the flexible substrate 1 protruding from the rigid substrate 3 by cutting in a subsequent process.

When the thermocompression bonding between the flexible substrate 1 and the rigid substrate 3 is completed, the terminal portion 10 of the flexible substrate 1 is exposed to the outside through the through holes 6 and 7. During the plating process or the etching process for forming a circuit pattern on the rigid substrate 3, plating solution or etching solution adheres to the terminal part 10, and the terminal part 10 is damaged. In order to prevent this, before plating and etching, as shown in FIG. 6, the terminal portion 10 exposed through the through holes 6, 7. A removable resin 11 is also applied.

Thereafter, as shown in FIG. 7, through-hole holes 13 and through-hole plating layers 14 are formed to penetrate the rigid substrate 3, the adhesive sheet 5, the film coverlay 8, and the flexible substrate 1. A circuit pattern 4A is formed by pattern etching the foil 4. The circuit pattern 4A of the rigid board 3 and the circuit pattern 2 of the flexible board 1 are electrically connected by the through-hole plating layer 14. When through-hole plating and etching are completed, the resin 11 is peeled off and cut along the cutting line indicated by f/Ab in FIGS. 7 and 8 to complete the rigid-flexible wiring board shown in FIG. 4. .

<Problems to be Solved by the Invention> However, in the above manufacturing method, the resin 11 does not adhere to the film coverlay 8 and the terminal portion 10 within the through holes 6, 7.9.
There is no problem if the resin 11 is applied uniformly to the surface of the image shown in Fig. It is difficult to apply the resin 11 in such an ideal state.

This is particularly difficult when the through holes 6, 7.9 are small and the rigid substrate 3 is thin, and in reality, as shown in FIG. 9, pinholes IIA may occur in the coated resin 11. Protruding portion 11B on the conductive foil 4 of the rigid board 3
It is normal for this to occur.

However, if a pinhole IIA occurs in the resin 11,
If pattern etching is performed on the conductive foil 4 in this state, the etching solution will come into contact with the conductor of the terminal portion 10 of the flexible substrate 1, and a pinhole will be created in this portion. Further, the protruding portion 11B of the resin 11 acts as an etching resist, and a desired wiring pattern is not formed on the rigid substrate 3.

Further, in the above method, since the coating of the resin 11 is carried out manually by a skilled person over a long period of time, there is a problem that the work efficiency is poor and that it is not suitable for mass production.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention aims to provide a method for manufacturing a rigid-flexible wiring board that can be carried out easily and with high efficiency without applying resin. .

<Means for Solving the Problems> In order to achieve the above object, in the present invention, a method for manufacturing a rigid-flexible wiring board is configured as follows.

That is, instead of applying a resin, a dry film photoresist is formed on the portion of the flexible substrate exposed through the through hole of the rigid substrate through a process of lamination, exposure and development, before thermocompression bonding between the rigid substrate and the flexible substrate. The portion that will become the flexible substrate upon completion is covered with this dry film photoresist.

After thermocompression bonding, drilling, through-hole plating, and pattern etching of the circuit on the rigid board are performed, and then the dry film photoresist is peeled off.

<Function> In the method for manufacturing a rigid-flexible wiring board according to the present invention, since a solvent-releasable dry film photoresist is created through the steps of lamination and exposure and development,
A protective film with a uniform thickness and no pinholes can be formed on the terminal portion of a flexible substrate with high positional accuracy. As a result, adhesion of plating solution or etching solution to the terminal portion during through-hole plating or pattern etching in subsequent steps is prevented. Furthermore, the protective film can be easily peeled off after treatment using a solvent.

<Example> FIG. 1 shows materials constituting a rigid-flexible wiring board manufactured by the method of the present invention and a method of laminating them. In the figure, 1 is a flexible board, 2 is a wiring pattern, 3 is a rigid board, 4 is a conductive foil, 5 is an adhesive sheet, 6, 7.9 are i! 8 is a film coverlay, 10 is a terminal portion, 11 is a dry film photoresist, and 12 is a notch.

Two rigid substrates 3 having a conductive foil 4 formed on the entire surface of one side are stacked with the conductive foil 4 on the outside with the film substrate 1 interposed therebetween, and the rigid substrate 3 and the adhesive sheet 5 The point that through holes 6 and 7 are formed respectively,
Furthermore, it is similar to the conventional structure (FIG. 5) in that the flexible substrate 1 is previously covered with a film coverlay 8 except for the terminal portions 10. What is different from the conventional method is that when the rigid substrate 3 is superimposed on the flexible substrate 1 via the adhesive sheet 5, a dry film photoresist 11 is placed on the film coverlay 8 and the terminal portion 10 that are exposed through the light transmitters 6 and 7. The two points are that it is formed through the steps of lamination and exposure and development, and that the notch 12 is formed in the portion that will become the outer contour of the flexible substrate upon completion.

FIG. 2 (al shows the cross-sectional structure after the rigid substrate 3, adhesive sheet 5, film coverlay 8, and flexible substrate 1 are stacked and thermocompression bonded as described above. A dry film photoresist 11 is formed to cover the terminal portions 10 on the back and front surfaces of the flexible substrate 1 and the surface of the film coverlay 8.

Thereafter, as shown in FIG. 2(b), a through hole 13 penetrating the conductive foil 4, rigid substrate 3, adhesive sheet 5, film coverlay 8, wiring pattern 2, and flexible substrate 1 is formed by drilling. . Furthermore, as shown in FIG. 2(C), after the plating layer 14 that electrically connects the conductive foil 4 of the rigid board 3 and the wiring pattern 2 of the flexible board 1 is formed on the inner surface of the through hole 13, The conductive 7F34 is pattern etched,
A wiring pattern 4A of the rigid substrate 3 is formed. In addition, in through-hole plating, since an alkaline plating solution is used, dry film photoresist 11
However, if an alkali peeling type is used, the dry film photoresist 11 will peel off during the plating process, so it is necessary to use a solvent peeling type.

When the through-hole plating and circuit pattern etching processes described above are completed, the dry film photoresist 11 is peeled off using a solvent (FIG. 2(C)).

In forming the circuit pattern on the rigid substrate 3, the conductive foil 4 is usually etched into a desired pattern using an alkaline peelable dry film photoresist. On the other hand, if a solvent-removable dry film photoresist is used to form this circuit pattern, when this resist is removed, the protective dry film photoresist 11 can also be removed at the same time. In addition, when an alkaline peelable photoresist is used for circuit pattern formation, the dry film photoresist 1
1 can be left without being peeled off, so the type of resist can be appropriately selected depending on the subsequent process.

FIG. 3 shows the state at the time when through-hole plating, circuit pattern etching, and dry film photoresist 11 peeling are completed, and after this, solder resist 15 is applied to the surface of rigid substrate 3 as necessary. By cutting along the broken NIAb as shown in FIG. 2(d), a rigid-flexible wiring board having a cross-sectional structure as shown in FIG. 2(dl) is completed.

Note that the notch 12 is formed in the outer part of the flexible substrate before thermocompression bonding, but this is because in the present invention, it is possible to process the external shape of the flexible substrate before thermocompression bonding. The reason for this is that conventionally, when a cut is made before thermocompression bonding, the resin flows down from the cut, resulting in extremely poor workability. On the other hand, in the present invention, dry film photoresist does not have such a problem, and therefore, even shapes that are difficult to process after thermocompression bonding can be processed in the same way as the external shape of a general flexible substrate.

In addition, polyimide, which is the material of the flexible substrate 1, is
Because the surface is smooth, it may be difficult for copper through-hole plating to adhere, but if dry film photoresist is formed on both the front and back sides of the flexible substrate, the plating will definitely adhere to this resist. Problems like this will be resolved.

<Effects of the Invention> According to the present invention, since the flexible substrate is coated with a dry film photoresist, there is no need to apply resin to protect the flexible substrate from damage during through-hole plating and circuit pattern etching processes. Problems such as resin pinholes and protrusion caused by resin application can be solved. Furthermore, since the complicated work of applying resin, which requires skill, is not required, the process time is shortened, and furthermore, since it is suitable for mass production, the cost of the product can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the composition of materials and the lamination method of the embodiment of the present invention, Fig. 2 is a diagram showing the cross-sectional structure of the embodiment of the invention, and Fig. 3 is a diagram showing the perspective structure of the embodiment of the invention. Figure 4 is a diagram showing the structure of a rigid-flexible wiring board, Figure 5 is a diagram showing the material composition and lamination method of the conventional example, and Figures 6, 7, and 9 are the cross-sectional structures of the conventional example. FIG. 8 is a diagram showing a perspective structure of a conventional example. 1...Flexible board 2.4A...Wiring pattern 3...Rigid board 4...Conductive foil 5...Adhesive sheet 6.7.9...Through hole 8...Film cover lay 0 ...Terminal part 1...Dry film photoresist 2...Notch 3...Through hole 4...Through hole plating layer Fig. 1

Claims (1)

[Claims] In a method for manufacturing a rigid-flexible wiring board, in which a rigid board and a flexible board are bonded together by thermocompression with an adhesive sheet interposed in between, and the circuits of the rigid board and the flexible board are electrically connected by through holes, the flexible board is A dry film photoresist is formed on a portion of the substrate other than the joint portion with the rigid substrate, and the dry film photoresist is removed after the flexible substrate and the rigid substrate are bonded by thermocompression and the through holes are formed. A method for manufacturing a rigid-flexible wiring board.