Multilayer printed wiring board

Abstract

In a multilayer printed wiring board, insulating layers and conductor layers are alternately stacked, and the conductor layers are electrically connected through via holes arranged on the insulating layers. The via hole is formed to have a swell at least on a part of it, in a substantially vertical direction to a thickness direction of the insulating layer. External stresses, such as a force of impact when dropped, are suppressed to have an insulating substrate not to easily warp, and cracks, disconnection, and the like of the conductor circuit are prevented. Thus, deterioration of reliability and drop impact resistance of a mounting substrate can be reduced.

Description

technical field [0001] The present invention relates to a multilayer printed circuit board for mounting electronic components such as capacitors and ICs on the surface. Specifically, it relates to a multilayer printed circuit that does not cause the electronic components to fall off or reduce electrical connectivity and reliability due to dropping. plate. Background technique [0002] In portable electronic devices such as mobile phones and digital cameras in recent years, miniaturization of mounting components has been sought in response to their high-function and high-density requirements. line width / wiring space gap), or measures to reduce the size of the pad, etc., can also correspond to the high density of the mounted parts. [0003] As components mounted on such substrates, specifically, passive components such as IC chips, capacitors, resistors, and inductor coils, liquid crystal devices, display devices for digital display, operating devices such as keyboards, and s...

AI Technical Summary

Problems solved by technology

[0011] In addition, although it is required to further reduce the thickness of the substrate itself used in portable electronic devices, since the thickness of the insulating layer of each layer constituting the mounting substrate is required to be 100 μm or less, even if it is multi-layered, the thickness of the entire mounting substrate itself will be reduced. It is thinner than the conventional mounting board itself, so it is easy to reduce the rigidity of the mounting board itself

[0012] In addition, since the rigidity of the substrate itself is lowered, the resistance to warping etc. is also likely to be lowered. As a result, the flatness of the substrate is easily impaired, and problems are likely to occur in subsequent processes (such as component mounting processes).

[0013] In addition, since the thickness of the insulating layer is thin, the mounting substrate itself is also soft and easily warped, so it is easily affected by stress due to external impacts, etc.

For example, although a method of improving rigidity by using insulating substrates with a thickness of 600 μm or more as the center of the insulating substrate during lamination has been studied, it may not be accommodated in a case of a portable electronic device, etc., so it becomes impossible to use it. The technical dilemma of the thickness of the insulating substrate in the center

[0014] Therefore, in the conventional multilayer circuit board for mounting as described above, since the rigidity cannot be increased by thickening the insulating substrate which is the center of lamination, it is difficult to improve the function or startability of the substrate in the drop test in the reliability test.

In particular, as described above, it is difficult to improve the reliability or the drop resistance to the drop test of the mounting substrate with increased mounting density of parts and the like.

That is, since sufficient reliability cannot be obtained in the reliability test, the electrical connectivity and reliability cannot be further improved.

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