JPH0779089A - Shielded flex-rigid multilayer wiring board - Google Patents

Abstract

PURPOSE:To make a rigid board section more thinner and a flexible section more flexible by applying conductive dyestuff to only the necessary sections (keeping away from a plating through-hole section). CONSTITUTION:A shield flex rigid four-layer wiring board is constituted of a rigid board section 1, an FFC (flexible printed wiring) section 2, through-hole (connection) sections 3, a conductive dyestuff-made shield layer 4, an inner-layer circuit 5, an outer-layer circuit 6, and a cover lay layer 7. As for the conductive dyestuff, dyestuff or paste having a proper degree of viscosity is used. The dyestuff or paste is made by a method wherein metal powder such as copper or metal-powder-coated inorganic powder or conductive powder which is carbon black or a combination of one or more kinds of that sort of materials is dispersed in the base resin which is light or electron beam hardening resin or a combination of one or more kinds of those and if necessary, a mucilage is added for a proper viscosity. As for the shape of the conductive powder, any shape is available.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a shield layer for a rigid / flexible printed wiring board which is a combination of a flexible printed wiring board and a rigid printed wiring board.
The present invention relates to a printed circuit wiring board formed using a conductive paint.

[0002]

2. Description of the Related Art Electromagnetic shielding of conventional rigid / flexible printed wiring boards has been performed by leaving a copper foil on the entire surface, which results in an increase in the thickness of the hard board, which is an FPC (flexible printed circuit). The part becomes stiff and the bending process becomes difficult.

[0003]

Therefore, as a result of various studies on the above problems, the present inventor used a conductive paint instead of forming a copper foil portion on the entire surface of a rigid / flexible printed wiring board as a shield layer. The present invention has been completed by finding that the hard plate portion can be made thin and the flexible portion can be made flexible by forming it only in a necessary portion (avoid the plating through-hole portion).

That is, the present invention is: In a rigid / flexible printed wiring board comprising a combination of a flexible printed wiring board and a rigid printed wiring board, a shield formed by a conductive coating material avoiding the plating through-hole portion. A flex-rigid multilayer wiring board is provided.

The present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic view showing a cross section of, for example, a shield flex rigid 4-layer wiring board according to the present invention. FIG. 2 is a perspective plan view showing the relationship between the shield layer of the conductive paint and the through hole (connection) portion in FIG. 1 excluding the outer layer circuit and the coverlay layer.

In FIGS. 1 and 2, 1 is a hard plate portion,
2 is an FFC (flexible printed circuit) part, and 3
Is a through hole (connection) part, 4 is a shield layer of conductive paint applied so as to avoid the through hole (connection) part, 5 and 6 are inner layer circuits and outer layer circuits, respectively.
7 is a coverlay layer.

The conductive paint used in the present invention includes epoxy resin, polyester resin, amino resin, phenol resin, polyurethane resin, polyisocyanate resin, vinyl resin, and light or electronic materials such as urethane acrylate, epoxy acrylate and ester acrylate. Metal powder of nickel, copper, silver, chromium, palladium, aluminum, gold, platinum or the like, or an inorganic powder obtained by coating these metal powders on one or more combinations of base resins selected from linear curable resins. Or a paint or paste in which a conductive powder composed of one kind or a combination of two or more kinds of carbon black, graphite, etc. is dispersed, and if necessary, a thickening agent or a thinning agent is added to obtain an appropriate viscosity. The thing of can be used.

The conductive powder may have any shape such as granular, spherical, flake, flake, plate, dendritic or dice. In the present invention, the shield layer of the conductive paint can be made thinner than that of the conventional copper foil, and especially the bending workability of the FFC portion can be facilitated.

Further, in the present invention, since the shield layer of the conductive paint is applied so as to avoid the through hole (connection) portion, the through hole plating test (-65 ° C.) is performed as shown in the graph of FIG. It can be seen that the environmental resistance test indicated by the number of cycles in air (30 minutes at + 125 ° C. for 30 minutes) significantly improves. For example, copper foil thickness 35 μm
When a shield layer of conductive paint is used instead of the above, the thickness of the shield layer can be reduced to 5 to 30 μm, and the thickness of Δ5 to 30% per layer can be reduced.

[0010]

According to the present invention, instead of forming a shield layer by covering the entire surface of a conventional copper foil, a shield layer of a conductive paint is applied. Therefore, the thickness of the shield layer can be reduced. In addition, the hard plate portion can be made thin and the flexible portion can be made flexible, and especially since the shield layer is applied so as to avoid the through hole portion, the environment resistance is also improved. As shown in FIG. 3, there is a clear difference in environmental resistance between the case where the shield layer of the conductive paint is provided avoiding the through-hole portion and the case where the shield layer is provided without avoiding it. Therefore, the shielded flex-rigid multilayer wiring board according to the present invention is effectively used as an internal wiring material in the field of using high frequency signals for the purpose of saving space and improving environmental resistance.

[Brief description of drawings]

FIG. 1 is a schematic view showing a cross section of a four-layer flex-rigid printed wiring board according to the present invention.

FIG. 2 is a perspective plan view of a four-layer flex rigid printed wiring board according to FIG.

FIG. 3 is a graph showing the results of environmental resistance comparing the case where the shield layer of the conductive coating material of the present invention is provided avoiding the through-hole portion and the case where it is provided without avoiding it.

[Explanation of symbols]

 1 Hard Plate Part 2 FPC Part 3 Through Hole (Connection) Part 4 Shield Layer of Conductive Paint 5 Inner Layer Circuit 6 Outer Layer Circuit 7 Coverlay 8 Insulating Layer

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[Procedure amendment]

[Submission date] October 19, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (1)

[Claims] 1. A rigid / flexible printed wiring board comprising a combination of a flexible printed wiring board and a rigid printed wiring board, wherein a shield layer made of conductive paint is formed avoiding the plating through-hole portion. Shield flex rigid multilayer wiring board.