JPS6317589A - Double-layer 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 [Technical Field] The present invention relates to a two-layer printed circuit board in which circuit conductors have a two-layer structure.

[Prior art and its problems]

In conventional two-layer printed circuit boards, circuit conductors in the required pattern are formed on both sides of a base film that serves as an insulating base material, and through holes are formed in the locations where the circuit conductors on both sides should be connected to connect the conductors. was.

However, to form through holes, it is necessary to drill holes in the printed circuit board and plate the inner surfaces of the holes. Conventional two-layer printed circuit boards have the disadvantage of high costs because they require a complicated process for through-hole processing, especially for plating the inner surfaces of the holes. In addition, since the linear expansion coefficient and rigidity of the base film and the plated metal are significantly different, if the printed circuit board is subjected to temperature changes, tension, or bending, there is a risk of cracks occurring in the through holes, which may reduce reliability. There was also a problem with that.

[Means for solving problems and their effects]

In view of the problems of the prior art as described above, the present invention provides a two-layer printed circuit board that does not require through-hole processing.The present invention consists of forming a circuit conductor in a desired pattern on one side of a base film. The base film of at least one of the two printed circuit boards made of a photosensitive resist film is made of a photosensitive resist film, and the two printed circuit boards are placed facing each other with the circuit conductor side inside, and there is a The circuit conductors of both printed circuit boards are bonded to each other using a conductive material at the locations where the circuit conductors are to be connected, and an adhesive insulating material is interposed at other locations, and at least the component mounting portion of the photosensitive resist film is exposed to light. , which is characterized by being removed by development.

That is, in this two-layer printed circuit board, the circuit conductors of the two printed circuit boards are connected through a conductive material such as a conductive paste at connection points, and are insulated through an adhesive insulating material at non-connection points. The situation is as follows.

By the way, in the case of a two-layer printed circuit board laminated with the circuit conductors inside as described above, both outer surfaces are base films, so how to mount components becomes a problem.In the present invention, however, the base film is By using a resist film and removing the component mounting area by exposure and development, the circuit conductor in that area is exposed, making it possible to mount the component.

〔Example〕

Hereinafter, a two-layer printed circuit board according to an embodiment of the present invention will be described in detail with reference to the drawings. For convenience, the manufacturing steps will be explained in order.

First, as shown in FIG. 1, a 17747911 layer 2 is formed on a photosensitive resist film 1 serving as a base film by means such as sputtering. As the photosensitive resist film 1, a photosensitive solder resist film such as Laminar RM dry film solder mask manufactured by Dynachem may be used.

Next, a solvent-type photosensitive resist is applied to the surface of the #R'FII layer 2, exposed to light, developed, etched, and then the resist is peeled off, as shown in FIG.
Two printed circuit boards 3A and 3B each having a desired pattern of circuit conductors 2A and 2B on one side of photosensitive resist films IA and IB are manufactured.

Next, a conductive paste 4 is printed on the connection points of the circuit conductor 2A of one printed circuit board 3A with the other circuit conductor, and an adhesive insulating material 5 is printed on the other places. The other printed circuit board 3B is laminated with the circuit conductor 2B facing inside. When the two printed circuit boards 3A and 3B are bonded together by heating and pressing in that state, the fourth
It will look like the figure. That is, the upper and lower circuit conductors 2A and 2B are electrically connected by the conductive paste 4 at the connection point with the other party, and are insulated by the insulating material 5 at other points.

This will basically form a two-layer printed circuit board, but as it is, both sides will be coated with photosensitive resist film IA.
Since it is IB, it is not possible to mount components.Therefore, when the component mounting portion of the photosensitive resist film LA-IB is removed by exposure and development, the circuit conductor 2B is exposed on the component mounting portion 6 as shown in Fig. 5. A two-layer printed circuit board 7 is obtained. This is the two-layer printed circuit board of this example.

Since the two-layer printed circuit board of this embodiment has the above structure, when mounting components, apply solder 8 to the component mounting area and solder the terminals of component 9 as shown in FIG. Bye. In order to prevent the photosensitive resist film LA-IB from being damaged by the heat during this soldering, it is preferable to use a photosensitive solder resist film as the photosensitive resist film. Therefore, when parts are fixed by means other than soldering, for example, by conductive paste, it is not necessary to use a solder resist film.

In the above embodiment, the conductive paste 4 for connecting the upper and lower circuit conductors 2A and 2B and the adhesive insulating material 5 for insulating them were formed by printing, but between the two printed circuit boards, It is also possible to have a structure in which the side substrates are bonded by interposing an adhesive insulating film that is locally made conductive only at the connection points.

Furthermore, in the above embodiment, a photosensitive resist film was used for each of the two printed circuit boards, but if components are to be mounted on only one side, the photosensitive resist film is used only on the side where the components are mounted, and the photosensitive resist film is used on the other side. Ordinary plastic film may be used.

Next, a method for manufacturing a multilayer printed circuit board by laminating the two-layer printed circuit boards of the present invention will be described.

After manufacturing a printed circuit board with a two-layer structure as shown in FIG. 4, the photosensitive resist films IA and IB on both sides are completely removed to form, for example, two two-layer printed circuit boards 7A and 7B as shown in FIG. Then, as shown in FIG. 8, conductive paste 4 and adhesive insulating material 5 are printed on one two-layer printed circuit board 7A in the same manner as in FIG. Two-layer printed circuit boards 7B are laminated. In this state, heat and pressurize to form two double-layer printed circuit boards 7A.
- By gluing 7B, a printed circuit board with a four-layer structure as shown in FIG. 8 can be obtained.

In this way, even a printed circuit board having a multi-layer structure can be easily manufactured.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to obtain a two-layer printed circuit board in which two-layer circuit conductors are connected at required locations without forming through holes, thereby reducing the cost of the two-layer printed circuit board. and is extremely effective in improving credibility. Furthermore, since the two-layer printed circuit board of the present invention has circuit conductors exposed in the component mounting area, component mounting can be carried out extremely easily.

[Brief explanation of drawings]

1 to 5 are cross-sectional views showing the manufacturing process of a two-layer printed circuit board according to an embodiment of the present invention, and FIG. 6 is a cross-sectional view showing a state in which components are mounted on the same two-layer printed circuit board.
7 to 9 are cross-sectional views showing the process of manufacturing a multilayer printed circuit board using the two-layer printed circuit board of the present invention. IA-IB~photosensitive resist film, 2A2B~circuit conductor, 3A/3B~single-sided printed circuit board, 4~conductive paste, 5~adhesive insulating material, 6~component mounting part, 7~
Double layer printed circuit board. Figure 1 2 5 Tomoe 11

Claims (2)

[Claims] (1) Among two printed circuit boards each having a circuit conductor in a desired pattern formed on one side of a base film, the base film of at least one of the printed circuit boards is made of a photosensitive resist film, and the two printed circuit boards are made of a photosensitive resist film. The circuit boards are placed facing each other with the circuit conductor sides facing each other, and a conductive material is interposed between the boards at the locations where the circuit conductors of both printed circuit boards should be connected, and an adhesive insulating material is interposed at other locations. A two-layer printed circuit board, characterized in that the two-layer printed circuit board is bonded and removed by exposing and developing at least the component-mounting portion of the photosensitive resist film. (2) A two-layer printed circuit board according to claim 1, wherein the photosensitive resist film is a photosensitive solder resist film.