Multilayer printed wiring board and its manufacturing method, and resin composition for filling through-hole

Abstract

A multilayer printed wiring board is composed of a substrate provided with through-holes, and a wiring board formed on the substrate through the interposition of an interlaminar insulating resin layer, the through-holes having a roughened internal surface and being filled with a filler, an exposed part of the filler in the through-holes being covered with a through-hole-covering conductor layer, and a viahole formed just thereabove being connected to the through-hole-covering conductor layer. Without peeling between the through-holes and the filler, this wiring board has a satisfactory connection reliability between the through-holes and the internal layer circuit and provides a high density wiring.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to a multilayer printed wiring board used as a package board for mounting an IC chip or the like and a process of producing the same, and more particularly to a multilayer printed wiring board capable of providing a high density wiring easily and of preventing the formation of cracks or the like in through-holes or in the neighborhood thereof when heat cycle occurs, for example.[0003]This invention also relates to a resist composition for filling through-hole of a multilayer printed wiring board, which composition is used for ensuring satisfactory electric connections between viaholes and through-holes even at high temperature and high humidity conditions or under such conditions as to cause heat cycle.[0004]2. Discussion of Background Information[0005]In general, through-holes are formed for electrically connecting the front surface to the back surface of a core substrate (hereinafter referred to...

AI Technical Summary

Benefits of technology

[0022]The present invention solves the aforementioned problems inherent in the conventional techniques, and the present invention provides a multilayer printed wiring board which can easily ensure high density wiring and a production process therefor.

[0023]The present invention provides a construction of a multilayer printed wiring board which is effective for preventing delamination between a filler for a through-hole and a conductor layer, for inhibiting delamination and formation of cracks between a conductor circuit and an interlaminar insulating resin layer, for preventing metal ions in the filler from diffusing and for protecting the filler from erosion by a laser beam.

[0024]The present invention further provides high density through-hole intervals and wiring in a build-up multilayer printed wiring board without reducing an electric connection reliability between through-holes and viaholes at high temperature and high humidity conditions.

[0025]The present invention also provides a construction of a multilayer printed wiring board for ensuring a reliable electric connection between an internal layer circuit inside a substrate and build-up multilayer circuit layers on both surfaces of the substrate even when the substrate is multi-layered.

Problems solved by technology

These through-holes are, however, considered as dead spaces in designing of a circuit, and hence become one of the factors which prevent wiring from densifying.

In addition, since coefficients of thermal expansion between the resin and a metal are different, the conductor layer on the through-holes may peel or form cracks due to heat cycle.

In a printed wiring board as is described in Japanese Unexamined Patent Publication No. 4-92496, gaps or voids tend to form because of poor adhesion between the conductor layer and the electric conductive material in the through-holes.

The formation of voids between the electric conductive material and a through-hole causes delamination of the conductor layer or generation of cracks on the through-hole in the use at high temperature and high humidity conditions due to air or water accumulated in the voids.

The pad is, however, frequently obstructive because it is formed protruding on the outer periphery of the through-hole and hence causes, for example, an increasing pitch between adjacent through-holes to each other.

This becomes an impediment to achieving a high density wiring or to narrower intervals between through-holes.

In such a wiring board, delamination between the filler and the conductor layer occurs when the wiring board is exposed to high temperature and high humidity conditions such as in Pressure Cooker Test, and a reliable connection between viaholes formed on the conductor layer and through-holes cannot be obtained.

The technique disclosed in Japanese Unexamined Patent Publication No. 5-243728 is not a technique relating to a build-up multilayer printed wiring board and hence does not make the most of the high density wiring function inherent in the build-up method.

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