JPH0832200A - Electronic circuit board and printed wiring board - Google Patents

Abstract

PURPOSE:To take the shortest course for a high frequency current to flow for the transition period of a digital signal from Low condition to High condition by mounting capacitor parts on both the section between a signal line and a power source and the section between the signal line and GND, in the vicinity of an IC terminal outputting the digital signal. CONSTITUTION:IC1 and IC 10 are mounted by soldering on the land parts having conductive layers provided on a printed wiring board, and the output signal pin 3 of IC 1, to a signal line 7, and a power source pin 2, to a power source pin 5, and a GND pin 4, to a GND line 6, are electrically connected, respectively. A capacitor 9 is inserted between the signal line 7 and the GND line 5, and also a capacitor 8 is inserted between the signal line 7 and the power source line 5. Accordingly, the loop of the flow of the high frequency currents of very high frequency components which are produced when the digital signal changes from Low to High become the shortest, and the radiation in normal mode and also the power stabilize, and the radiation in common mode is suppressed, too.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric circuit board and a printed wiring board, and more particularly to an electric circuit board suitable for digital circuits and a printed wiring board usable for the electric circuit board.

[0002]

2. Description of the Related Art Conventionally, there has been a problem that noise is picked up and malfunction occurs as a result of receiving unnecessary signal radiation from a signal line. Therefore, conventionally, as a measure for reducing unnecessary radiation, a resistor or a ferrite bead is inserted in the signal line, or a capacitor is inserted between the signal line and the ground (GND) line. Signal line and GND
When inserting a capacitor between them, it is general to form a low-pass filter in combination with a resistor and an inductance.

In particular, such an unnecessary radiation countermeasure is 100M.
This is important in circuits that generate high-frequency components of H or higher, and the recent development of digital circuits has made us re-recognize the importance of measures against unnecessary radiation.

An example of conventional measures against unwanted radiation will be described with reference to the drawings.

FIG. 6 is a schematic layout diagram for explaining an example of the layout of each electric component arranged on a conventional electric circuit board.

In FIG. 6, 1 is a quad flat
Package type (Quad Flat Pack
e; QFP type) digital IC (integrated circuit element),
3 is an output signal pin, 4 is a GND pin, 6 is a GND line, 7
Is a signal line, 9 is a capacitor, and 10 is a small outline package type (Small Outline).
Package; SOP type IC, 11 is IC
10 input signal pins.

As shown in FIG. 6, the signal line 7 and the GND
The line 6 is connected to the terminal side of the IC 1 via a capacitor 9.

By inserting the capacitor 9 as described above,
A countermeasure against unwanted radiation is taken by forming a loop through the capacitor 9 in a very high frequency region.

[0009]

However, if the capacitor 9 is inserted only between the signal line 7 and the GND line 6 as shown in FIG. 6, the signal level becomes high (Hi.
When gh) changes to low, there is no problem, but when the signal level changes from low to high, it may not be a sufficient countermeasure.

FIG. 7 is a schematic circuit diagram showing a part of the circuit of the electric circuit board shown in FIG. The above reason will be described with reference to this drawing.

In FIG. 7, 22 is a buffer in IC1, 26 is a buffer in IC10, 27 is a bypass capacitor of IC1, 28, 29, 30 and 31 are inductances of power supply line patterns, and 32 is a bypass capacitor of IC10. is there. In the figure, the same numbers as those in FIG. 6 indicate the same items as those in FIG.

When taking countermeasures against unwanted radiation in a very high frequency region, it is important to shorten the path through which the high-frequency current flows and to reduce the loop area formed by the high-frequency current.

Therefore, as shown in FIG. 6 and FIG. 7, the capacitor 9 is interposed between the signal line 7 and the GND line 6 to reduce the loop area formed by the high frequency.

However, the signal level changes from High to L
In the case of ow, a loop of a short route as shown by the arrow 25 in the drawing is formed, but in the case of Low → High, a loop of a long route as shown by the arrow 34 in the drawing is formed.

That is, in the case of the countermeasure against unnecessary radiation as shown in the figure, when the transition period from High to Low has a sufficient effect, but in the transition period from Low to High, the countermeasure is not sufficient. was there.

As described above, when the path through which the high-frequency current flows becomes long, not only the normal mode radiation becomes large directly, but also the power supply and the ground system of the IC become unstable, and as a result, the common mode radiation also increases. In some cases, the effect of measures against unwanted radiation was diminished.

The normal mode radiation is the radiation generated from the current flowing in the loop composed of the signal line and the ground, and the common mode radiation is the radiation radiated by the common mode potential (in many cases, the ground potential) using the cable or the like as the antenna. That is.

The present invention provides an electric circuit board which does not or does not substantially cause the problem of unnecessary radiation which is a problem in an electric circuit, particularly an electric circuit which handles digital signals, and a printed wiring board which can be used for the electric circuit board. The purpose is to do.

Another object of the present invention is to provide an electric circuit board having a high effect of preventing unwanted radiation especially in a high frequency region and a printed wiring board which can be used for the electric circuit board.

A further object of the present invention is to provide an electric circuit board capable of taking high measures against unwanted radiation in a wider frequency band, and a printed wiring board that can be used for the electric circuit board.

In addition, according to the present invention, the signal line is changed from Low to Hi.
An object of the present invention is to provide an electric circuit board and a printed wiring board that can be used for the electric circuit board, which can effectively take measures against unwanted radiation in both the transition period to gh and the transition period from High to Low. And

[0022]

An electric circuit board according to the present invention which achieves the above object comprises an integrated circuit element having a plurality of terminals arranged on a substrate, and the terminal in the vicinity of the terminal of the integrated circuit element. A capacitor is provided between the signal line and the power supply line connected to and the signal line and the ground line.

Further, the printed wiring board of the present invention which achieves the above object is provided at a base and a position on the base where an integrated circuit element is arranged, corresponding to a plurality of terminals of the integrated circuit element. In a printed wiring board having a land portion and a wiring connected to the land portion, a capacitor is provided between one of the wirings and two wirings different from the wiring in the vicinity of the land portion. .

[0024]

With the above-mentioned configuration, the high-frequency current loop that causes unnecessary radiation is reduced by each capacitor when the signal level changes from High to Low and from Low to High. Since the path through which high-frequency current flows can be made shorter,
It is possible to take sufficient measures against unnecessary radiation.

Further, by blocking the signal line with the power supply line and the ground line adjacent to each other, it is possible to further prevent unwanted radiation.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

<Embodiment 1> FIG. 1 is a schematic view (hereinafter, referred to as “schematic layout drawing”) illustrating a schematic layout of each component of an electric circuit board for explaining a first embodiment of the present invention. .

In the present embodiment, not only is the capacitor 9 mounted and inserted as a separate component between the signal line 7 and the GND line 6, but also another component is provided between the signal line 7 and the power supply line 5. A capacitor 8 is mounted and inserted as.

The ICs 1 and 10 are mounted by soldering on lands having a conductive layer formed on the printed wiring board.

Therefore, the output signal pin 3 of the IC 1 is the signal line 7, the power supply pin 2 is the power supply line 5, and the GND pin 4 is GND.
The lines 6 are electrically connected to each other.

In FIG. 1, IC1 is a QFP type digital IC having lead pins extending in four directions as in FIG. 6, and is, for example, a CMOS digital IC. Similarly to FIG. 6, the IC 10 is also shown as an example of a SOP type digital IC having lead pins extending in two directions.

FIG. 2 is a schematic circuit diagram showing a part of the circuit of the electric circuit board shown in FIG.

In this embodiment, the signal line 7 and the power line 5
Since the capacitor 8 is inserted between and, the high frequency current of a very high frequency component generated especially when the digital signal changes from Low to High flows in the route indicated by the arrow 33 in the figure, so that the loop is shortest. Therefore, not only the normal mode radiation but also the common mode radiation can be suppressed because the power supply is stabilized.

Of course, when changing from High to Low, a high frequency current flows through the path 25 in the figure, so that the loop is also shortest and unnecessary radiation can be suppressed.

The capacitors 8 and 9 are connected to the capacitor I as much as possible.
It is desirable to be arranged near the connection portion between each pin of C and the signal line 7, power supply line 5, and GND line 6. This is because the capacitors 8 and 9 are I.sub.2, as can be seen from FIGS.
This is because as the distance from the pin of C1 increases, the path through which the current is formed becomes longer, the area of the loop increases, and it becomes difficult to suppress radiation.

Further, it is not always necessary to make the capacitors 8 and 9 have the same capacitance. It is preferable to change the capacitance of the capacitor according to the characteristics of the integrated circuit device.

For example, the characteristics of rise and fall times of integrated circuit elements that output signals are compared. If the rise time is faster than the fall time, a capacitor (capacitor 8) connected between the signal line and the power supply line. It is desirable to increase the capacitance of the capacitor and increase the capacitance of the capacitor (capacitor 9) connected between the signal line and the ground line when the signal fall time is fast.

The capacitance of capacitors 8 and 9 is preferably 1
0 pF or more and 100 pF or less, more preferably 15 pF
Or more, 80 pF or less, more preferably 20 pF or more,
It is preferably 60 pF or less.

Of course, it is preferable that these values are appropriately selected according to the target frequency for which unwanted radiation countermeasures are desired.

<Embodiment 2> FIG. 3 shows a schematic layout of each component of an electric circuit board according to a second embodiment of the present invention.

In this embodiment, in addition to the two capacitors 8 and 9 described in the first embodiment, a resistor 12 is inserted between the signal pin 3 of the IC 1 and the capacitors 8 and 9. Note that the resistor 12 may have a component having an inductance component instead.

According to this embodiment, the problem of unwanted radiation can be reduced in the lower frequency band as compared with the case of the first embodiment.

It should be noted that it is preferable to appropriately select the capacitance and resistance of the capacitor. Generally, the smaller the capacitance or resistance, the higher the frequency side, and the larger the capacitance, the lower the frequency side. However, note that if the capacitance or resistance is increased more than necessary, the signal waveform becomes blunt.

<Embodiment 3> FIG. 4 shows a schematic layout of each part of an electric circuit board according to a third embodiment of the present invention.

In this embodiment, in addition to having two capacitors and one resistor as a countermeasure against unnecessary radiation as in the second embodiment, the power supply line 5 is provided on one side of the signal line 7 and the GN is provided on the other side.
The D line 6 is arranged along and close to the signal line 7.

A capacitor 8 is inserted between the power supply line 5 and the signal line 7, a capacitor 9 is inserted between the signal line 7 and the GND line 6, and a resistor 12 is inserted in the middle of the signal line 7.

Of course, also in this embodiment, the resistor 12 may have an inductance component.

The GND line 6 and the power supply line 5 are arranged close to the signal line 7, respectively, and have a guarded structure. The power supply line 5 passes under the IC 10 and is connected to the power supply pin 17 of the IC 10. Also, the GND line 6 passes under the IC 10 and the IC
10 to GND pin 18. Of course, Example 1
Also in 2 and 2, the connection destination of each line is the same.

The power supply line 5 and the GND line 6 are I on the IC 10 side.
An example is shown in which each pin is connected through the lower side of the package of C10, but this is to protect the signal line 7 up to the connection between the signal line 7 and the signal pin 11.

Therefore, the routing of this wiring can be appropriately changed depending on the position of each pin of the IC 10.

According to the present embodiment, compared with the first embodiment, there is an effect against unwanted radiation from a lower frequency to a higher frequency.

In this embodiment, the signal line 7 is connected to the power supply lines 5 and G.
Not only guarding with ND line 6, but also capacitor 8
9 and the resistor 12 are arranged, the effect of unwanted radiation is higher than that of the second embodiment.

That is, in the guard of the signal line 7 by the power source 5 and the GND line 6, a capacitance is formed between the wirings, which is effective against unnecessary radiation.

Since the capacitors 8 and 9 are arranged closer to the IC1 side than in the second embodiment (in the second embodiment, the capacitors 8 and 9 are arranged apart from the resistor 12 by the resistor 12). As a result, the loop becomes smaller, which is more effective against unwanted radiation.

<Embodiment 4> FIG. 5 shows a schematic layout of each part of an electric circuit board according to a fourth embodiment of the present invention.

In the present embodiment, unlike the above-mentioned embodiments, the capacitors 8 and 9 are not mounted as separate parts but are built in the printed wiring board.

That is, the conductive layers are formed in a comb pattern and are combined so as to face each other so that the protruding portions do not come into contact with each other, that is, between the protruding portions of the conductive layer of one wiring and the protruding portions of the other wiring are positioned. To form a capacitor.

Referring to FIG. 5, branch portions (protrusions) 7a are formed on the IC1 side of the signal line 7 so as to intersect with the signal line 7, and a branch portion (projection) extending from the power supply line 5 between the branch portions 7a ( Projection)
The conductive layer is formed so that the branch portion (projection) 6a extending from 5a or the GND line 6 is located.

In this embodiment as well, the signal line 7 is guarded by the power supply line 5 and the GND line 6 as in the third embodiment.

In this embodiment, since the capacitance is formed on the printed wiring board, it is not necessary to mount the capacitor as a mounting component anew, and the mounting cost and soldering failure do not occur, and the reliability is improved.

Since the capacitor can be formed closer to each pin of the IC, it is easy to form a smaller loop.

The capacitor exemplified in the present embodiment is not limited to the position shown in the figure, and a part may be under the package of IC1.

The capacitor can be modified other than the illustrated form, and a capacitor structure may be formed by providing counter electrodes in the vertical direction with the base material of the printed wiring board in between.

[0064]

EFFECT OF THE INVENTION By mounting a capacitor component or forming a capacitive pattern such as a printed pattern on both the signal line-power source and the signal line-GND near the IC terminal for outputting a digital signal. , High to L
Not only the signal change to the ow state, but especially the digital signal is L
Since the path through which the high-frequency current flows can be minimized during the transition period from the ow to the High state, it is highly effective as a countermeasure against unwanted radiation.

Further, by guarding a part or all of the signal line with both the power supply line and the GND line, it is possible to exhibit a characteristic that capacitance is added from the signal line to both the power supply and the GND, which is more effective.

It is needless to say that the present invention is not limited to the above-mentioned embodiments, and can be appropriately modified and combined within the scope of the gist of the present invention.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a schematic arrangement of an electric circuit board of the present invention.

FIG. 2 is a schematic circuit diagram for explaining a circuit configuration of an electric circuit board of the present invention.

FIG. 3 is a schematic diagram illustrating a schematic arrangement of an electric circuit board of the present invention.

FIG. 4 is a schematic diagram illustrating a schematic arrangement of an electric circuit board of the present invention.

FIG. 5 is a schematic diagram illustrating a schematic arrangement of an electric circuit board of the present invention.

FIG. 6 is a schematic diagram illustrating a schematic arrangement of a conventional electric circuit board.

FIG. 7 is a schematic circuit diagram for explaining a circuit configuration of a conventional electric circuit board.

[Explanation of symbols]

 1 IC (Integrated Circuit Element) 2 Power Supply Pin 3 Output Signal Pin 4 GND Pin 5 Power Supply Line 6 GND Line 7 Signal Line 8 Capacitor 9 Capacitor 10 IC 11 Input Signal Pin 12 Resistance

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideho Inagawa, 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor, Toru Osaka, 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Yoshimi Terayama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (19)

[Claims] 1. An integrated circuit element having a plurality of terminals arranged on a substrate, and a signal line and a power supply line connected to the terminal and a signal line and a ground line in the vicinity of the terminal of the integrated circuit element. An electric circuit board having a capacitor between them. 2. The electric circuit board according to claim 1, wherein the integrated circuit device handles a digital signal. 3. The electric circuit board according to claim 1, wherein the capacitor is a mounted component. 4. The electric circuit board according to claim 1, wherein the capacitor has a conductive layer formed on the substrate. 5. The electric circuit board according to claim 4, wherein the conductive layer has a comb pattern. 6. The electric circuit board according to claim 1, wherein the terminal connected to the signal line outputs a digital signal. 7. The capacitance of the capacitor is 10 pF or more 1
The electric circuit board according to claim 1, having a capacitance of 00 pF or less. 8. The capacitance of the capacitor provided between the signal line and the power supply line is equal to the capacitance of the capacitor provided between the signal line and the ground line. Electric circuit board. 9. The capacitance of the capacitor provided between the signal line and the power supply line is different from the capacitance of the capacitor provided between the signal line and the ground line. The electric circuit board according to. 10. The electric circuit board according to claim 1, wherein the capacitance of the capacitor is changed according to the characteristics of the integrated circuit element. 11. A base, a land portion provided at a position on the base where the integrated circuit element is arranged, corresponding to a plurality of terminals of the integrated circuit element, and a wiring connected to the land portion. A printed wiring board having the same, wherein each of the wirings has a capacitor between one of the wirings and two wirings different from the wiring in the vicinity of the land portion. 12. One of the wirings is used as a signal line, and two wirings different from the wirings are used as a power supply line and the remaining one is used as a ground line.
The printed wiring board according to 1. 13. The printed wiring board according to claim 12, wherein the signal line handles a digital signal. 14. The printed wiring board according to claim 11, wherein the capacitor is formed of a conductive layer formed on the substrate. 15. The printed wiring board according to claim 14, wherein the conductive layer has a comb pattern. 16. The printed wiring board according to claim 11, wherein the capacitors have the same capacitance. 17. The printed wiring board according to claim 11, wherein the capacitors have different capacities. 18. The printed wiring board according to claim 17, wherein the capacitance of the capacitor differs depending on the characteristics of the integrated circuit device. 19. The printed wiring board according to claim 11, wherein the capacitor has a capacitance of 10 pF or more and 100 pF or less.