Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1998-12-07
2001-02-06
Gaffin, Jeffrey (Department: 2841)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S255000
Reexamination Certificate
active
06184478
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a printed wiring device, and more specifically, relates to a printed wiring or circuit device with a simple structure, wherein a high-speed digital circuit or a circuit which handles high speed signals can be mounted.
Conventionally, as a printed wiring or circuit device, a multilayer circuit board has been used in the field wherein densification or integration is required. FIG.
2
(
a
) is a sectional view showing a structure of a conventional multilayer circuit board. The circuit board is structured such that five insulation layers
20
through
24
are laminated, and on both surfaces of the circuit board and between the respective insulation layers, a grounding layer
25
, a power supply layer
26
, and four signal line layers
27
through
30
are provided.
It has been employed that the grounding layer
25
and the power supply layer
26
have solid and plane patterns in order to lower impedance as well as to make the signal line function as a microstrip line, and further to achieve a shielding function between the layers. Then, a width of the signal line has been determined so that characteristic impedance as the microstrip line is matching with output impedance of a mounted circuit.
In recent years, it has been requested that the electronic device is miniaturized and has a lighter weight, and in accordance therewith, the circuit board with a large number of layers is necessary. However, in the conventional printed circuit board as described above, in order to increase the number of layers with the same thickness, it is necessary to reduce the thickness of the insulation layers.
The characteristic impedance of the signal line has a function of w/h, wherein the thickness of the insulation layer is h and the width of the signal line is w (referring to Takeshi Yoshida, “Revised High Frequency Design Know-How”, printed by CQ Press on Jul. 1, 1997, pages 67-80). Therefore, in order to obtain the same characteristic impedance by using the same material as the insulation layer and halving the thickness h of the insulation layer, it is necessary to halve the width w of the signal line.
However, there have been the following problems. As the signal line is narrower, the inductance constituent in the signal line is increased, so that the high frequency constituent in the signal is decreased to cause the signal delay or deformation. Also, when the width of the signal line is reduced, the device can not be manufactured by the existing manufacturing equipment, resulting in increasing the manufacturing cost.
An object of the present invention is to solve the aforementioned problems, and to provide a printed wiring or circuit device with a simple structure, wherein a high-speed digital circuit or a circuit which handles high speed signals can be mounted.
Further objects and advantages of the invention will be apparent from the following description of the invention.
SUMMARY OF THE INVENTION
To achieve the aforementioned object, the present invention provides a printed wiring or circuit device, which has at least one of a grounding layer and a power supply layer, wherein the one of the layers is provided with a plurality of holes at least in an area opposed to a part of a signal line.
According to the present invention, a conductor layer constituting a ground side of a microstrip line is provided with a great number of holes in the area opposite to the signal line so as to reduce an average value of the capacitance between the signal line and the ground side. Therefore, there can be achieved the same operation as in a device wherein a thickness of an insulation layer is effectively increased, so that even if the insulation layer is thinned without narrowing the width of the signal line, the characteristic impedance of the signal line can be controlled at the desired value.
REFERENCES:
patent: 5016085 (1991-05-01), Hubbard et al.
patent: 5348792 (1994-09-01), Hattori et al.
patent: 5519176 (1996-05-01), Goodman et al.
patent: 5633479 (1997-05-01), Hirano
Imano Hajime
Kato Yoshikazu
Adtec Corporation
Gaffin Jeffrey
Kanesaka & Takeuchi
Norris Jeremy
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