Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2002-04-25
2004-03-16
Vigushin, John B. (Department: 2827)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S763000, C361S780000, C361S793000, C333S012000, C333S175000, C333S176000, C333S185000, C333S247000, C257S691000, C257S700000
Reexamination Certificate
active
06707685
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-layer wiring board used for an electronic circuit board on which a semiconductor device housing package for housing therein a semiconductor device, a semiconductor device, an electronic component, or the like are mounted, and more particularly to a multi-layer wiring board having a wiring structure suitable for housing or mounting a semiconductor device which is operated at high speed.
2. Description of the Related Art
A multi-layer wiring board, on which electronic components including a semiconductor device such as a microprocessor, an ASIC (Application Specific Integrated Circuit), or a semiconductor integrated circuit device are mounted, is commonly used for an electronic circuit board or the like. Hitherto, in constituting a wiring conductor for usage in internal wiring, a multi-layer wiring board is formed by alternately stacking one on top of another insulating layers made of ceramics such as alumina, and wiring conductors made of metal having a high melting point such as tungsten (W).
In keeping with an increasing demand for improvements in data processing capability, a semiconductor device has come to be operated at higher and higher speed. As a result, out of wiring conductors for internal wiring, a signal wiring line is required to offer improved electric properties in terms of characteristic impedance matching, reduction in cross-talk noise between signal wiring lines, or other. In a conventional multi-layer wiring board, out of wiring conductors for internal wiring, a signal wiring commonly takes on a strip wiring structure. That is, a wiring conductor formed as a signal wiring line has, in its upper and lower parts, a wider-area ground layer or power source layer of so-called solid-pattern configuration formed via an insulating layer.
However, such a multi-layer wiring board as stated above has the following disadvantage. Since the insulating layer is made of alumina ceramics or the like having a relative dielectric constant of ca. 10, an electromagnetic coupling between the signal wiring lines becomes unduly great, resulting in an undesirable increase in cross-talk noise. This makes it impossible to handle increasingly higher operational speed of a semiconductor device.
In order to deal with higher-speed electric signals, attempts have been made to obtain a high-density, high-performance multi-layer wiring board capable of operating a semiconductor device at higher speed. For example, such a multi-layer wiring board is constructed as follows. An insulating layer is formed by using polyimide resin or epoxy resin having a relatively low relative dielectric constant in a range from 3.5 to 5, instead of alumina ceramics having a relative dielectric constant of ca. 10. On this insulating layer is formed an internal wiring conductor layer made of copper (Cu) by a thin-film forming technique based on a vapor-deposition method, such as an evaporation method or a sputtering method. Then, by using photolithography, a wiring conductor of fine pattern is formed, and the insulating layer and the wiring conductor are stacked in layers.
In order to reduce ringing noise by achieving wiring impedance matching, to reduce cross talk between signal wiring lines, and to realize high-density wiring, as an internal wiring structure designed for a multi-layer wiring board, such a structure is proposed that groups of parallel wiring lines are formed on the top surface of each insulating layer and they are stacked in layers, and, out of the wiring lines included in the layered wiring groups, specified ones are electrically connected to each other via a through conductor such as a via conductor or a through hole conductor.
In a multi-layer wiring board having such a parallel wiring group, to provide electrical connection between an electronic component, such as a semiconductor device, to be mounted on the multi-layer wiring board and amounting board for mounting thereon the multi-layer wiring board, with in the multi-layer wiring board, out of the wiring lines included in the groups of parallel wiring lines, suitable ones are selected. The selected wiring lines lying in different wiring layers are connected to each other via a through conductor such as a via conductor.
According to the multi-layer wiring board described above, as compared with the case where the signal wiring takes on a strip line structure, the number of the wiring layers can be reduced. Besides, inside the groups of parallel wiring lines, as well as in a region between the groups of parallel wiring lines, cross talk between the signal wiring lines can be reduced.
Moreover, one problem involved in power source supply for a semiconductor device is occurrence of simultaneous switching noise. Specifically, since a power-source voltage required for switching of the semiconductor device is supplied from the outside of the multi-layer wiring board through the power source wiring and ground wiring, when a plurality of signal wiring lines are concurrently subjected to the switching operation of the semiconductor device, noise is produced between the power source wiring and the ground wiring due to the inductance components included in the power source wiring or the ground wiring.
To overcome the above-stated problems, there has been adopted a method of incorporating within the multi-layer wiring board a capacitor composed of a wider-area power source wiring layer and a ground wiring layer, which are arranged so as to oppose each other via an insulating layer provided therebetween. By arranging the wider-area power source wiring layer and/or ground wiring layer in that way, it is possible to incorporate within the multi-layer wiring board a capacitor having a capacitance value as great as several nF. Consequently, the impedance value for the built-in capacitor is reduced, whereby making it possible to reduce the simultaneous switching noise. Note that the impedance value is proportional to the square root of the inductance value but is inversely proportional to the square root of the capacitance value. It has been known that, in general, the smaller the impedance value for the built-in capacitor, the less the simultaneous switching noise. Further, to obtain as large a capacitance value as possible, an attempt has been made to form a plurality of capacitors within the multi-layer wiring board.
However, the above-described multi-layer wiring board, provided with the groups of parallel wiring lines arranged orthogonally with respect to each other, also encounters a problem of EMI (Electro Magnetic Interference) noise, as the result that an electronic component, such as a semiconductor device, to be mounted thereon has come to be operated at higher and higher speed. The EMI noise mentioned just above may be explained as follows. If electronic equipment of various types emit an unnecessary electromagnetic wave, the electromagnetic wave finds its way into the electronic equipment or other peripheral electronic equipment, so that it becomes noise and exerts an adverse effect on the electric circuits. This brings the electronic equipment into malfunction.
Besides, as further improvement has been eagerly sought in data processing capability, the operational speed of a semiconductor device has been rapidly increased and, for example, a semiconductor device has come to be operated at a frequency of greater than 1 GHz. As a natural consequence of this trend, another problem arises that unduly large simultaneous switching noise is caused by a harmonic component included in an electric signal which is transmitted to the interior of the multi-layer wiring board.
The harmonic component refers to a frequency component having a relatively high frequency included in a digital signal. The harmonic component is increased in component proportion at a frequency which is equivalent to an integral multiple of the operating frequency (fundamental wave) of the semiconductor device, but is decreased in component proportion as its frequency becomes higher and high
Kabumoto Masanao
Kawabata Kouki
Hogan & Hartson
Kyocera Corporation
Vigushin John B.
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