Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1997-07-10
2002-03-05
Gandhi, Jayprakash N. (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S780000, C361S792000, C361S793000, C361S795000, C174S255000, C174S256000, C333S012000, C029S846000
Reexamination Certificate
active
06353540
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an electronic apparatus which copes with an EMC which is becoming more and more important in increasing speed and packaging density of IC and LSI devices, and to a device, a circuit board and an electronic apparatus which require suppression means for spurious radiation noise and a method of making the same.
BACKGROUND ART
An EMC intends to the compatibility of an electromagnetic environment of an EMI (noise source) and an immunity (noise receiver). Recently, the rise of an operating frequency due to high performance of a product raises a radiation intensity of spurious radiation, which leads the EMI to a severe situation. Further, with the population of the electronic products, the countermeasure for the EMI of the electronic products is becoming severer.
It is reported that the increase of the anticipated spurious radiation amounts to 4 dB/year. If the spurious radiation increases in this manner, the electromagnetic environment becomes more and more worse and it is no doubt that a television video screen is disturbed or a manipulation system of an aircraft becomes uncontrollable and social problems are raised.
For this reason, a noise regulation in terms of a radiation intensity and a scope of applicable products is more and more enhanced and manufacturers are endeavoring to enhance the EMC performance of the products by design and simulation prediction technique to clear the regulation.
As a technical reference relating thereto, JP-A-3-14284 is cited. The JP-A-3-14284 discloses a built-in structure to a printed circuit board in place of discrete parts of a ferrite core and a ferrite beads which are existing countermeasure parts.
In order to enhance the EMC performance of the product, various countermeasure parts such as a common mode choke, a filter and a bypass capacitor for an I/O unit and a power supply have been used from the past but these parts present demerits of {circle around (1+L )} increase of a cost, {circle around (2+L )} problem to so-called high packaging density such as minituarization, thinning and weight reduction of a product due to the increase of volume, {circle around (3+L )} complexity of the countermeasure part, and {circle around (4+L )} restriction to external view design.
Further, in such a prior art product, the conformity to the future increase of the spurious radiation due to the rise of the operation frequency of the product is restricted.
The restriction to the suppression of the spurious radiation from the electronic apparatus by using the countermeasure parts is explained for a case of a bypass capacitor.
As examples of means for suppressing the spurious radiation form the electronic apparatus, the suppression of a potential fluctuation of a ground system which serves as a drive source for an antenna and the insertion of a common mode core to a cable are cited. Of those, the means for suppressing the potential fluctuation includes a method for using a bypass capacitor.
FIG. 13
shows a sectional structure model of a four-layer circuit board using a bypass capacitor. The four-layer circuit board comprises a signal layer (S
1
), a power layer (V), a ground layer (G) and a signal layer (S
2
). In
FIG. 13
, a dielectric material layer is omitted. As externally connected circuit components, a device equivalent circuit comprising a series connection of an inductance Ld, a load resistor Rd and a switch SW and a power equivalent circuit comprising a series connection of a bypass capacitor having a capacitance of C
0
, a DC power supply E
0
and an inductance Lg are included. In the circuit board, a stray capacity C
1
by the power layer (V) and the ground layer (G) and inductances L
0
and L
1
by a wiring pattern and through-holes are formed.
The bypass capacitor is provided in order to absorb the potential fluctuation as described before.
FIG. 14
shows an equivalent circuit of the sectional structure model shown in FIG.
13
.
Since the potential fluctuation V
0
occurs in a power lead of an IC device at the switching of the IC device (modeled by ON/OFF of SW in FIG.
14
), the bypass capacitor is provided to absorb the potential fluctuation V
0
.
However, since the inductances L
0
and L
1
due to the wiring pattern and the through-holes for connecting the bypass capacitor C
0
are included by the nature of the circuit board structure, a resonance loop is created with the stray capacity C
1
and the effective suppression of the potential fluctuation may be difficult.
Namely, as the operation frequency rises and harmonics frequencies rise, the bypass capacitor does not exhibit the inherent capacitance characteristic because of its inductive component and it cannot absorb the potential fluctuation of the ground system.
Namely, as the operating frequency of the electronic product rises, the prior art technique cannot cope with the future increase of the spurious radiation.
As other countermeasure means, plating may be applied to a plastic housing to form a shield structure to suppress the spurious radiation as seen in a modern notebook type personal computer, but the shield structure has demerits of {circle around (1+L )} increase of cost and {circle around (2+L )} the reduction of added value of the product by a problem to recycling the plastic housing.
Thus, new countermeasure means for suppressing the spurious radiation without lowering the added value of the electronic apparatus has been demanded, and on the other hand, a mechanism of the spurious radiation has not been fully investigated. As described in the Technical Journal of the Association of Electronics and Electronic Communications of Japan, EMCJ 94-88 (1995-3), the investigation of a radiation source model for a common mode radiation is behind and it is a future problem to be solved.
It is an object of the present invention to provide an electronic apparatus which suppresses spurious radiation at a level of a circuit board mounted on the apparatus.
It is a second object of the present invention to provide a structure of a circuit board to be applied to an electronic apparatus.
It is a third object of the present invention to provides a circuit board and a method of manufacturing the same when the structure of the present invention is applied to various manufacturing methods.
DISCLOSURE OF INVENTION
In order to achieve the first object of the present invention, an electronic apparatus is provided with a circuit board suppressing spurious radiation is formed by providing first and second ground layers having at least one thereof electrically connected to electrical parts, a power layer provided between said first ground layer and said second ground layer and electrically connected to said electronic parts, a dielectric material layer for joining said second ground layer and said power layer and a resistor layer having said first ground layer and said second ground layer electrically connected, and said circuit board is housed in a housing.
Alternatively, an electronic apparatus is provided with a circuit board suppressing spurious radiation is formed by providing a ground layer and a power layer electrically connected to electronic parts, a dielectric material layer for connecting said second ground layer and said power layer, and a first dielectric material layer and a second dielectric material layer sandwiching said ground layer and said power layer therebetween, and said circuit board is housed in a housing.
In order to achieve the second object of the present invention, a structure is characterized by the provision of a first conductor layer and a second conductor layer; a third conductor layer provided between said first conductor layer and said second conductor layer; a first dielectric material layer for joining said first conductor layer and said third conductor layer; a second dielectric material layer for joining said second conductor layer and said third conductor layer; and a resistor for joining said first conductor layer and said second conductor layer.
Alternatively, a structure is provided with a first conductor layer, a
Akiba Yutaka
Kitamura Naoya
Narizuka Yasunori
Tanei Hirayoshi
Antonelli Terry Stout & Kraus LLP
Gandhi Jayprakash N.
Hitachi , Ltd.
Vigushin John B.
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