Active solid-state devices (e.g. – transistors – solid-state diode – Gate arrays – With particular power supply distribution means
Reexamination Certificate
1998-12-28
2002-02-05
Potter, Roy (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Gate arrays
With particular power supply distribution means
C257S664000, C257S691000
Reexamination Certificate
active
06344667
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device, a semiconductor package and a semiconductor module wherein radiation of undesired electromagnetic waves is controlled.
With the development of multimedia, there are increasing demands for high-speed data processing and high-speed data transmission. To meet these demands, research and development is actively being carried out into both hardware and software, and there have been noticeable improvements in performance.
In particular, in the field of semiconductor technology, there has been progress in increasing the speed and performance of a microprocessor, the nucleus of a computer, and increasing memory speed and capacity, and high-speed data processing and data transmission is now possible even with an inexpensive personal computer.
However, as a result of increased high-speed and high performance of LSI, undesired electromagnetic waves radiated from electronic equipment have become stronger, increasing together with frequencies, and it is feared that these may have an adverse influence not only on other electronic equipment but also on human beings.
Most radiation of undesired electromagnetic waves is caused by noise occurring between signal wires and the power layer and ground layer due to signal reflection and crosstalk between wires, switching of semiconductor elements and the like, in a circuit board comprising electronic components such as LSI or passive components mounted on a wiring board. This noise causes undesired electromagnetic waves to be radiated from the circuit board, as well as outside the device through heat-dissipation holes or the like in the case.
This radiation of undesired electromagnetic waves divides into waves radiated from the surface of a substrate when a high-speed signal, such as a clock signal, propagates through a circuit pattern formed on the substrate, and waves radiated from the sides of the substrate as a result of resonance between the power layer and the ground layer.
As described in “Methods for Reducing Unwanted Emission Originating in the Power Layer and Ground Layer of a Printed Wiring Board” in the collection of lectures and papers of the 11th Circuit Mounting Technology Lecture Meeting, wave radiation caused by resonance between the power layer and the ground layer can be controlled by providing insulating layers on each side of the power layer to insulate the power layer from the ground layer.
On the other hand, as for instance described in Jpn. Pat. Appln. KOKAI Publication No. 8-228055, wave radiation from the surface of a substrate on which a circuit pattern is formed can be controlled by a shield method wherein a copper paste is applied to the surface of the circuit pattern, with a solder resist in between, and this copper paste is connected to ground.
Furthermore, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-18099, there is another known method wherein, signal wires are provided symmetrically on both sides of a ground wire, so that electromagnetic waves arising from the signal wires cancel each other out, thereby preventing the generation of the undesired electromagnetic waves themselves.
However, with regard to reliability and performance, the above methods have had the following problems. The shield method using copper paste proposed in Jpn. Pat. Appln. KOKAI Publication No. 8-228055 has reliability problems, since weak contact between the copper paste and the solder resist can cause peeling.
On the other hand, the method of symmetrically providing signal wires on both sides of a ground wire so that electromagnetic waves arising from the signal wires cancel each other out, proposed in Jpn. Pat. Appln. KOKAI Publication No. 9-18099, has performance problems since the reduction effect of radiated electromagnetic waves is less than 10%.
In addition, undesired electromagnetic waves are radiated from electronic components, such as a connector, mounted on a printed board. This is mainly a result of the fact that the wires on the printed board and the pin structure inside the connector, provided roughly at a right angle to the printed board, constitute an antenna.
Proposed countermeasures include, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-199235, controlling noise radiation by inserting a ring-shaped core into the connector, or, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-82420, providing a conductive cover over the outer wall of the connector before connecting it to ground, thereby shielding the pin inside the connector and controlling leakage and radiation of electromagnetic waves.
However, these various conventional techniques require a special connector structure and consequently increase the cost of the connector. Since a great number of connectors are used in a semiconductor device, an increase in the cost of connectors leads to a considerable increase in the cost of the semiconductor device.
Furthermore, another cause of radiation of undesired electromagnetic waves from a printed wiring board is a through-hole portion (wherein a signal transmission path is provided within a through-hole). That is, a through-hole portion, and a wiring pattern on the board surface which is connected to the through-hole portion, together produce a structure which has the same configuration as a microstrip antenna, and consequently electromagnetic waves radiate from the through-hole portion.
However, in conventional technology, it has been difficult to control radiation of undesired electromagnetic waves from a through-hole portion.
As regards undesired electromagnetic waves radiating from the mount structure of a semiconductor component, the problem of radiation from the pin portion is revealed in, for instance, B-4-17 in the collection of lectures and papers of the 1997 Lecture Meeting of the Electronic Data Communication Academy Communications Society.
However, as pointed out in edition 114 (pp.72 to 77) of the Environmental Electromagnetic Engineering Special Magazine EMC, a present-day semiconductor package structure does not control radiation of electromagnetic waves, and since there have been no specific suggestions for improvement or patent applications, this problem remains to be solved.
But, undesired electromagnetic waves are radiated from a semiconductor package because wires provided on a wiring board and leads of the semiconductor package together form a structure which acts as an antenna.
Here, it is technically possible to reduce radiation of undesired electromagnetic waves by changing the shape of the leads, but since specifications of semiconductor components, including lead shapes, are defined by world standards, it is extremely difficult and time-consuming to change the shape of leads.
However, due to increasing world-wide restrictions on the environmental problem of unwanted electromagnetic wave radiation, there is a demand in present standard specifications for a method of controlling radiation of electromagnetic waves.
BRIEF SUMMARY OF THE INVENTION
Accordingly, a first object of the present invention is to provide a semiconductor device capable of reducing radiation of undesired electromagnetic waves without loss of reliability.
A second object of the present invention is to provide a semiconductor device wherein radiation of undesired electromagnetic waves from a connector can be controlled without increasing the cost of the connector.
A third object of the present invention is to provide a semiconductor device wherein radiation of electromagnetic waves from a through-hole portion can be controlled.
A fourth object of the present invention is to provide a semiconductor package wherein radiation of undesired electromagnetic waves can be controlled and a semiconductor device using the same.
A fifth object of the present invention is to provide a semiconductor module wherein radiation of undesired electromagnetic waves can be controlled.
In order to achieve the above first object, the semiconductor device of the present invention comprises a first signal wire provided on a substrate; a pair of secon
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Potter Roy
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