Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – Insulating material
Reexamination Certificate
1999-03-31
2002-04-30
Williams, Alexander O. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
Insulating material
C257S700000, C257S758000, C257S528000, C257S532000, C257S693000, C257S692000, C257S772000, C257S779000, C361S306100, C361S306300, C361S311000, C361S313000
Reexamination Certificate
active
06380619
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chip-type electronic component to be surface mounted on a conductive pattern of a circuit board or the like.
2. Discussion of Background
The miniaturization of electronic devices accomplished in recent years has inspired efforts to achieve ever smaller chip-type electronic components. For instance, dimensions have been reduced to attain currently existing chip-type laminated ceramic capacitors having a length of 0.6 mm, a width of 0.3 mm and a thickness of 0.1 to 0.3 mm.
The component of the known art as described above includes a substrate having a roughly rectangular paralellepiped shape and two external electrodes to be soldered onto a conductive pattern of a circuit board or the like. Each external electrode is provided at one of two diametrical ends in the lengthwise direction of the substrate so as to cover one surface in its lengthwise direction, two surfaces in its widthwise direction and two surfaces in its thicknesswise direction.
When mounting the chip-type electronic component of the known art onto a conductive pattern of a circuit board or the like, it is necessary to allow for insulating gaps between the sides in its widthwise direction and sides of adjacent chip-type electronic components, or between sides in its widthwise direction and sides of adjacent circuit elements, since the electrodes that partially cover the sides may cause electrical shorting.
Also, when mounting the chip-type electronic component of the known art onto a conductive pattern of a circuit board or the like by means of soldering, an adverse phenomenon occurs. The weight of the component causes the molten solder to flow from under the external electrodes in a widthwise direction toward adjacent components provided on the circuit board. As a result, it is necessary to allow for insulating gaps between the sides in its widthwise direction and sides of adjacent chip-type electronic components, or between sides in its widthwise direction and sides of adjacent circuit elements, to ensure that the excess molten solder does not cause any electrical shorting.
Thus, while super miniaturization of chip-type electronic components has been successful, the extent to which mounting density can be improved is still limited.
As a means for solving this problem, Japanese Unexamined Patent Publication No. 201634/1995 discloses a component that includes a substrate having a roughly rectangular paralellepiped shape and two external electrodes to be soldered onto a conductive pattern of a circuit board or the like. Each external electrode is provided at one of two diametrical ends in the lengthwise direction of the substrate so as to cover only the two surfaces in its thicknesswise direction.
As another means for improving the mounting density, Japanese Unexamined Patent Publication No. 156514/1990 discloses a component that includes a substrate having a roughly rectangular paralellepiped shape and two external electrodes to be soldered onto a conductive pattern of a circuit board or the like. Each external electrode is provided at one of two diametrical ends in the lengthwise direction of the substrate so as to cover only one of the two surfaces in the thicknesswise direction of the substrate.
However, since the external electrodes in both of these prior art components are formed over their entire width, the phenomenon whereby the molten solder flows from under the external electrodes in a widthwise direction toward adjacent components provided on the circuit board, cannot be prevented.
Still as another means for improving the mounting density, Japanese Unexamined Patent Publication No. 55333/1997 discloses a component that includes a substrate having a roughly rectangular paralellepiped shape and two external electrodes to be soldered onto a conductive pattern of a circuit board or the like. Each external electrode is provided at one of two diametrical ends in the lengthwise direction of the substrate so as to cover two surfaces in its widthwise direction and two surfaces in its thicknesswise direction. Since the external electrodes are provided at diametrical ends in the lengthwise direction of the component, a similar problem to that of the electronic component disclosed in the aforementioned Japanese Unexamined Patent Publications occurs.
Furthermore, chip-type electronic components are usually surface mounted by means of reflow soldering. In this process, before mounting the external electrodes, a solder paste is applied to portions of the conductive pattern of a circuit board or the like where electrodes are to be mounted, after which the chip-type electronic component is set in place by ensuring that the external electrodes are positioned on the solder paste. Next, the solder paste is molten by way of applying heat after which the external electrodes of the chip-type electronic component become soldered to the conductive pattern on the circuit board or the like.
However, when the solder paste becomes molten during the reflow soldering process, its buoyancy and the like cause the chip-type electronic component to float on the circuit board which results in misalignment of the component.
With the appearance of ever smaller chip-type electronic components in recent years, floating and misalignment of minute chip-type electronic components has become common.
In order to prevent such floating and misalignment, the chip-type electronic components of the prior art must be held at a specific position until the molten solder becomes solidified, resulting in poor efficiency in the surface mounting process.
In addition, because the external electrodes of the chip-type electronic component in the prior art are provided at diametrical ends in the lengthwise direction of the substrate, a large solder fillet forms between the external electrodes and the conductive pattern when it is surface mounted on a circuit board or the like. These solder fillets may cause shorting between the chip-type electronic component and adjacent chip-type electronic components or between the chip-type electronic component and the conductive pattern of a circuit board or the like.
In order to prevent this problem from occurring, the mounting density at which chip-type electronic components are mounted must be reduced and, as a result, it presents an obstacle to achieve an improvement in the mounting density.
Yet as another means for improving the mounting density, Japanese Unexamined Patent Publication No. 55084/1993 discloses a laminated ceramic capacitor that includes a substrate having a roughly rectangular paralellepiped shape, internal electrodes and two external electrodes to be soldered onto a conductive pattern of a circuit board or the like. Portions of internal electrode films lead out to one surface in the thicknesswise direction of the substrate and external electrodes are provided where the portions of the internal electrodes are led out, to electrically connect the lead-out portions to the external electrodes. The ceramic substrate is achieved by alternately laminating internal electrode films and dielectric layers.
However, since the external electrodes in this prior art are flat, it is impossible to prevent floating and misalignment during the soldering process, resulting in shorting due to the presence of solder fillets.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a chip-type electronic component that achieves outstanding mass productivity.
It is a further object of the present invention to provide a chip-type electronic component that can be mounted onto a conductive pattern of a circuit board or the like by means of soldering.
It is a still further object of the present invention to provide a chip-type electronic component that can significantly improve the mounting density of a circuit board.
It is a still further object of the present invention to provide a chip-type electronic component that can be soldered with a high degree of reliability while reducing the likelihood of misalignment when it is s
Ahiko Taisuke
Ishigaki Takaya
Sato Hiroki
Takashi Kamiya
Yamamoto Masanori
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
TDK Corporation
Williams Alexander O.
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