JPH06204664A - Multilayer substrate - Google Patents

Abstract

PURPOSE:To increase the mounting density of a circuit board by filling the inside of prepreg with conductive paste, by forming a conductive circuit within the prepreg, thereby providing high-density wiring and, at the same time, reducing the number of through-holes. CONSTITUTION:Viaholes 2 are formed by a punching machine at a plurality of positions required through a prepreg 1. Then, the viaholes 2 are filled up with a conductive paste 3 by means of screen printing or dispenser coating. This conductive paste is produced by blending metal powder of gold, silver, copper or nickel with a thermosetting resin such as phenol resin or epoxy resin, and solvent can be also mixed together. The prepreg 1 filled up with the conductive paste is placed between printed wiring boards 4a and 4b, both the surfaces of which had wiring circuits L in advance and is pressed to one united body after correcting the positions so as to secure the continuity between each electrode 5 of the printed wiring boards 4a and 4b and the conductive paste.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layered substrate used in electronic equipment and the like, and more particularly to a multi-layered substrate which enables high-density mounting.

[0002]

2. Description of the Related Art Regarding the densification of a printed wiring board, interlayer connection is an important requirement for densification, and therefore various manufacturing methods and techniques have been introduced. For example, in order to establish conduction on both sides of the double-sided wiring board, there are a method of connecting by plating through the through holes, and a method of connecting the through holes by using a conductive paste.

By the way, along with the miniaturization of a series of parts including a semiconductor integrated circuit, it has become possible to increase the function on the printed wiring board and further miniaturize the device. However, a single-sided / double-sided wiring board is insufficient in the number of wires and terminal connection cannot be processed. Therefore, a multilayer board in which a plurality of printed wiring boards are laminated is used. As the multilayer substrate, for example, as shown in FIG. 2, prepregs 12 are provided on both sides of a printed wiring board 11 having wiring circuits L formed on both sides.
After a copper foil is laminated on the outermost layer via a and 12b, a through through hole 13 is provided, conductive plating is applied to the through hole 13, and the outermost copper foil is etched to form the wiring circuit L. What forms is known.

Further, in order to increase the number of interlayer connections and increase the density, as shown in FIG. 3, the printed wiring boards 14a and 14b are preliminarily connected by through holes 13 and wiring circuits L are formed on both surfaces. It is known that a prepreg 15 is interposed between the prepreg 15 and the prepreg 15 and the printed wiring boards 14a and 14b are electrically connected 16 respectively.

[0005]

As described above, in the conventional multi-layer substrate, although the upper and lower surfaces are electrically connected through the through holes, the multi-layer structure is formed by interposing the prepreg. The method of connecting the conductive layers located on both sides of the prepreg relies on the connection by through holes penetrating the entire multilayer substrate. Therefore, the number of through-holes increases, and the number of components that can be mounted on the surface layer is limited, which is a factor that hinders high-density mounting.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a multi-layered substrate capable of high-density mounting.

[0007]

In order to achieve the above object, the gist of the present invention is to form a via hole in the prepreg in a multi-layered substrate in which a printed wiring board is laminated on an inner layer or a surface layer through a prepreg. The multilayer substrate is characterized in that the via hole is filled with a conductive paste.

[0008]

[Function] By connecting the conductive layers located on both sides of the prepreg through the prepreg filled with the conductive paste, high-density wiring becomes possible, and at the same time, the number of through-holes can be reduced, so that the component mounting area can be reduced. Take big,
The mounting density of the printed wiring board can be improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a method for manufacturing a multi-layer substrate of the present invention will be described below with reference to FIG. As shown in the figure, first, via holes 2 having a diameter of 0.2 to 1.0 mm are formed by a punching machine at a plurality of required portions of the prepreg 1. Then, the conductive paste 3 is filled in the via hole 2 by screen printing or a dispenser coating method. The conductive paste 3 has a particle size of 1 to 100 μm.
The metal powder of gold, silver, copper, nickel or the like is blended with a thermosetting resin such as a phenol resin or an epoxy resin, and a solvent may be contained therein.

The prepreg 1 filled with the conductive paste is interposed between the printed wiring boards 4a and 4b having wiring circuits L formed on both sides in advance, and the printed wiring board 4 is provided.
After the position is corrected so as to secure the conduction between the electrodes 5 of a and 4b and the conductive paste 3, they are pressed together.
Although the above example shows a four-layer substrate, it goes without saying that more multilayer substrates can be manufactured by the same method.

[0011]

As described above, according to the present invention, the conductive paste is filled in the prepreg to form the conductive circuit in the prepreg, which enables high-density wiring and at the same time minimizes the number of through-holes. be able to. As a result, the number of components that can be mounted on the surface layer of the wiring board increases, and so-called high-density mounting becomes possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a multilayer substrate according to the present invention.

FIG. 2 is a cross-sectional view of a conventional multilayer substrate.

FIG. 3 is a cross-sectional view of another conventional multilayer substrate.

[Explanation of symbols]

 1, 12a, 12b, 15 ... Prepreg 2 ... Via hole 3 ... Conductive paste 4a, 4b, 11, 14a, 14b ... Printed wiring board 5 ... Electrode 13 ... Through hole L ... Wiring circuit

Claims (1)

[Claims] 1. A multi-layered substrate having a printed wiring board laminated on an inner layer or a surface layer via a prepreg, wherein a via hole is formed in the prepreg and a conductive paste is filled in the via hole. Substrate.