Multilayer printed wiring board

Abstract

A package substrate free of malfunction or error even with an IC chip in a high frequency range, particularly an IC chip with a frequency exceeding 3 GHz, is provided. A conductor layer 34P on a core substrate 30 is formed to have a thickness of 30 μm and a conductor circuit 58 on an inter layer resin insulating layer 50 is formed to have a thickness of 15 μm. By making the conductor layer 34P thick, it is possible to increase a volume of the conductor itself and decrease resistance. Further, by employing the conductor layer 34 as a power supply layer, it is possible to improve a capability of supplying power to the IC chip.

Description

TECHNICAL FIELD[0001]This invention relates to a multilayer printed wiring board and provides a technique related to a multilayer printed wiring board capable of having improved electric characteristics and reliability without causing malfunction, error or the like even if a high frequency IC chip, particularly an IC chip in a high frequency range of 3 GHz or higher is mounted thereon.BACKGROUND ART[0002]In forming a buildup type multilayer printed wiring board constituting an IC chip package, inter layer insulating resin is formed on one of or each of the surfaces of a core substrate having through holes formed therein and via holes for inter layer conduction are opened by a laser or photo etching, whereby an inter layer resin insulating layer is thereby formed. A conductor layer is formed on the via holes by plating or the like and etching and the like are performed to form a pattern, thus creating a conductor circuit. Further, by repeatedly forming the inter layer insulating laye...

AI Technical Summary

Benefits of technology

[0010]The first advantage of the invention is that by making the conductor layer as the power supply layer of the core substrate thick, it is possible to intensify the strength of the core substrate and that even if the core substrate itself is made thin, it is possible for the substrate itself to relax warps and generated stresses.

[0011]The second advantage of the invention is that by making the conductor layers thick, it is possible to increase the volumes of the conductors themselves. By increasing the volumes, it is possible to decrease the resistances of the conductors. Due to this, the electrical transmission of the signal line or the like is not hampered. Accordingly, the loss of the signal transmitted or the like does not occur. This advantage is exhibited by making only the substrate which becomes the core thick.

[0012]The third advantage of the invention is that by employing the conductor layer as the power supply layer, it is possible to improve the capability of supplying power to the IC chip. In addition, by employing the conductor layer as the earth layer, it is possible to decrease the noise superposed on the signal and power to the IC chip. This is because the decreased resistances of the conductors as described as the second advantage can prevent the supply of power from being hampered. Due to this, if the IC chip is mounted on the multilayer printed wiring board, it is possible to decrease a loop inductance from the IC chip—the substrate—the power supply. Accordingly, power shortage in an initial operation is decreased to make it difficult to cause power shortage. Even if the IC chip in a higher frequency range is mounted on the multilayer printed wiring board, malfunction, error or the like does not occur in the initial operation.

[0013]Further, even if the power is supplied to the IC chip via the IC chip—the substrate—capacitors or the power supply layer—power, the same advantage can be exhibited. The loop inductance can be decreased. For this reason, no loss occurs to the supply of power to the capacitors or dielectric layers. In the first place, the IC chip performs complex arithmetic processings and operations while instantaneously consuming power. By supplying power from the power supply layer to the IC chip, it is possible to supply the power without the need to mount many capacitors even if the IC chip in a high frequency range is mounted and power shortage (a state of the occurrence of voltage drop) occurs in the initial operation. Power shortage (voltage drop) in the initial operation occurs so as to employ the IC chip in the high frequency range. If the conventional IC chip is used, the necessary power is sufficiently supplied by the capacity of the capacitors or dielectric layers.

[0014]Particularly if the thickness of the conductor layer serving as the power supply layer of the core substrate is larger than the thickness of the conductor layer on the inter layer insulating layer on each surface or both surfaces of the core substrate, the three advantages stated above can be maximized. The conductor layer on the inter layer insulating layer mainly means herein a conductor layer formed by forming via holes which are non-through holes for inter layer connection in an inter layer resin insulating layer made of resin the core material of which is not impregnated and conducting plating and sputtering. As long as the conductor layer has via holes formed therein, but not limited thereto, the conductor layer can be used as the conductor layer on the inter layer insulating layer.

[0015]The power supply layer of the core substrate may be arranged on the surface layer or inner layer of the substrate or on each of the surface layer and the inner layer. If the power supply layer is formed on the inner layer, a plurality of layers of two or more may be arranged. Basically, as long as the power supply layer of the core substrate is thicker than the conductor layer of the inter layer insulating layer, the advantage of the power supply layer can be exhibited.

Problems solved by technology

However, as the frequency of an IC chip is higher, the frequency of occurrence of malfunction or error becomes higher.

Particularly if the frequency of the IC chip exceeds 3 GHz, the frequency of occurrence of malfunction or error considerably increases.

If the frequency exceeds 5 GHz, the IC chip often turns inoperative.

Due to this, a computer including the IC chip as a CPU cannot perform operations that the computer should do, i.e., cannot perform desired functions and operations such as the recognition of an image, the changeover of a switch and the transmission of data to the outside of the computer.

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