JP3403315B2 - Signal distribution system and backboard and asynchronous transfer mode switch - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal distribution system, a backboard and an asynchronous transfer mode switch, and more particularly to a signal distribution system, a backboard and an asynchronous transfer mode switch suitable for speeding up signal distribution.

[0002]

2. Description of the Related Art As a large-scale system having a large number of lines, a system having a plurality of boards connected to a common backboard, and a circuit for realizing a function on each board is distributed and mounted Has been done. The signal distribution to each substrate in such a system is performed using, for example, a bus transmission system. For the interface circuit in the bus transmission system, see, for example, "Nikkei Electronics 1993.9.27 (no.591)", Nikkei BP.
See pages 69 to 290.

Bus transmission applied to a backboard having a plurality of substrates mounted thereon will be described with reference to FIGS. 15 and 16.

First, the structure of the backboard will be described with reference to FIG.

In FIG. 15, a plurality of substrates 3 are connected to the backboard 2 via connectors 5, respectively.

Each of the connectors 5 has a plurality of connector pins 6, respectively. These connector pins 6 are connected to each other by the main line 8 formed on the backboard 2.

An interface IC 4 for inputting / outputting signals to / from the board 3 and a circuit for performing signal processing on the board 3 are mounted on each board 3.

A branch circuit 9 for connecting the interface IC 4 to the connector 5 is formed on the substrate 3.

The interface IC 4 inputs / outputs a signal to / from the outside of the substrate 3 via the branch line 9.
The interface IC 4 includes a receiver circuit and a driver circuit, which are not shown here.

Next, with reference to FIG. 16, a signal transmission operation in the backboard configured as described above will be described.

In FIG. 16, the main transmission line 8 formed on the backboard 2 and the branch transmission line 9 formed on each substrate 3 constitute a comb-shaped transmission line.

First, when the signal given to the backboard is distributed to each substrate, as shown in FIG. 16 (a), the driver circuit 14 is used as a signal source for the backboard 2.
When a signal is given to the receiver, the given signal is branched from the main line 8 to each branch line 9 and sent to the receiver circuit 11 of each substrate 3.

Further, the signal generated on each board is
When it is given to the backboard, as shown in FIG.
Is transmitted to the main line 8 via. The signal transmitted through the main line 8 is received by the receiver circuit 16.

Each of the impedance circuits (receiver circuit 11 and driver circuit 15) has a high impedance as viewed from the comb-shaped transmission line side (main line 8 and branch line 9). For example, the characteristic impedance is equivalent to infinity. Thereby, the connection point of the impedance circuit viewed from the transmission line side can be regarded as an open end.

Therefore, the characteristic impedance of the transmission line can be made equal when the substrate 3 is mounted and when the substrate 3 is removed. Further, it is possible to reduce the current flowing through the connector 5, which is the connecting portion between the substrate 3 and the transmission line. Therefore, the substrate 3 can be inserted and removed in a live state.

[0016]

However, the fact that each of the interface circuits has a characteristic impedance corresponding to infinity with respect to the branch line 9 means that the signal transmitted through the transmission line is input to and output from the interface circuit. When reflected, it causes reflection. Therefore, the transmission characteristics of the transmission line including the main line 2 are affected by the distortion of the waveform depending on the line length.

Such an influence cannot be ignored as the delay time in the branch line 9 becomes larger than the rising time of the signal to be transmitted. Therefore, the band in which the signal can be transmitted is limited.

When the delay times of the plurality of branch lines 9 are the same, variations in the influence of these reflections are reduced.
However, even if the variation is reduced, the influence of reflection still exists, so that waveform distortion occurs and the transmittable signal speed is reduced. If there are many branch lines 9,
Since the influences of these reflections are superimposed on each other, a shorter delay time is required for each branch line 9.

For example, in the example shown in FIG. 15, the branch line 1
3 is a portion of each board 3 from the connection portion to the connector 5,
It is wired up to the mounting portion of the interface IC4. The length of this wiring is about 10 cm on an ordinary substrate. When a signal having a waveform with a branch line 13 having a length of 10 cm and a rise time Tr of 2 ns is used, the maximum data rate that can be transmitted is about 20 MHz. Above this, normal transmission due to waveform distortion can be performed. Disappear.

As described above, in the conventional signal distribution method using the backboard 2, when the transmission cycle of the data distributed to each substrate 3 on the backboard 2 is increased, the signal waveform is distorted and the circuit Cause the malfunction. For this reason,
It is difficult to speed up the data transmission cycle.

This is, as shown in FIG.
In either case where a signal is distributed from one driver circuit 14 to a plurality of receiver 11 circuits, or when signal transmission is performed from a plurality of driver circuits 15 to one receiver 16 as shown in FIG. Also becomes a problem.

On the other hand, as another method of transmitting signals, there is a method of using signal wiring for connecting driver circuits and receiver circuits in a one-to-one relationship. In this system, since there is no branch line, it is possible to transmit a good waveform that is not affected by reflection by the branch line.

However, it is necessary to prepare a large number of wirings on the backboard 2 corresponding to the number of signals. This conflicts with the demand for smaller backboards. That is, when the connectors 5 are mounted at high density with a narrow pitch, the number of wires for connecting the connector pins 6 to each other is limited. Therefore, the usage efficiency of the connector pins 6 on the backboard 2 deteriorates. Area where wiring of backboard 2 can be formed (area where connector 5 is not provided)
Since it is limited, it is difficult to mount a large number of ICs equipped with a circuit for distributing signals according to the number of signals.

By the way, in recent years, in response to the demand for higher speed and higher bandwidth of the IDSN, a higher speed of the ATM switch is being studied. According to the study by the inventors, it is required to improve the transmission speed of the backboard provided in the ATM switch in order to increase the speed of the ATM switch. ATM
The branch board is mounted on the backboard of the exchange at a high density to accommodate a large capacity line.
For this reason, it is considered that the backboard capable of mounting the boards at a high density and capable of transmitting signals at a high speed is provided to contribute to the speeding up and the capacity increasing of the ATM switch.

A first object of the present invention is to provide a signal distribution system and a backboard capable of widening the signal transmission band.

A second object of the present invention is to provide a signal distribution system and a backboard which can broaden the signal transmission band in a state where a large number of signal lines are mounted at high density.

Furthermore, it is possible to mount the signal lines in high density,
A third object is to provide an ATM exchange capable of transmitting signals at a high data rate.

[0028]

To achieve the first object, according to a first aspect of the present invention, a signal distribution in a backboard for distributing signals to a plurality of boards to be connected. In the method, the backboard includes a connector for connecting each of the plurality of boards, a line common to the plurality of connectors, and an impedance converter for performing impedance conversion, and the connector has the impedance A signal distribution system is provided, which is connected to the common line via a converter, and the impedance converter has a high impedance with respect to an input from the common line side.

According to a second aspect of the present invention, in a backboard for distributing signals to a plurality of boards to be connected, the backboard includes connectors for connecting the plurality of boards, respectively. A line common to the plurality of connectors, and an impedance converter for converting impedance are provided, the connector is provided in parallel on one surface of the backboard, and the impedance converter is The connector pins of each connector, which are arranged in a region sandwiched by the side-by-side connectors on the backboard, are connected to the common line via an impedance converter and are high relative to the input from the line side. Provided is a backboard which is connected so as to have an impedance.

According to the third aspect of the present invention, in a backboard for distributing signals to a plurality of substrates to be connected, a distribution line having a main line and a plurality of branch lines branched from the main line is provided. A plurality of connectors that are formed and have board connecting portions for connecting the boards are juxtaposed, the connector pins of each connector are connected to the branch line,
Each of the branch lines has a characteristic impedance larger than the characteristic impedance of the main line in the first section, which is a part of the path on the side connected to the main line,
An impedance converter is provided between the first section and a second section, which is a section on the side to which the connector pin is connected, and the impedance converter has a first section when viewed from the first section side. The section 2 side corresponds to the open end, and
A backboard is provided, characterized in that the first section and the second section are connected so that the characteristic impedance in the second section corresponds to the characteristic impedance of a line formed on the substrate. It

According to a fourth aspect of the present invention to achieve the above second object, in the backboard according to the above second aspect, a plurality of the impedance converters are housed in a package. In the package, leads for connecting the impedance converters to the outside are arranged on one side surface of the package.
Further, there is provided a backboard in which the leads are arranged in the backboard so that the leads are arranged in a row along the longitudinal direction of the connector.

In order to achieve the third object, according to the fifth aspect of the present invention, a plurality of transmission lines for connecting to the lines are connected, and asynchronous for exchanging data communication in the plurality of lines. In the transmission mode (ATM) exchange, there is provided an asynchronous transmission mode exchange characterized in that a line board for connecting a plurality of the transmission lines is provided with the backboard described in the fourth aspect.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment of the present invention will be described with reference to FIGS. 1 to 3 and FIGS.

In FIG. 1, the backboard 2 according to the present embodiment has a plurality of connectors 5 arranged in parallel on one surface for connecting the substrates 3. Each connector 5 is provided with a plurality of connector pins 6.

A plurality of main lines 8 (only one corresponding to one pin of the connector is shown in FIG. 1) are formed on the other surface of the backboard 2 and the interface IC 1 is used. The connector pins 6 are connected to each other.

The interface IC 1 is equipped with an interface circuit for realizing the interface function. The interface circuit is configured to have a high impedance with respect to the main line 8 side, and the driver circuit,
And a receiver circuit. As the interface IC1, for example, a digital IC, an analog IC or the like can be used. The signal form that the digital IC supports is, for example, TTL, CMOS, LV.
TTL etc. are mentioned.

The above driver circuit and receiver circuit are
Any circuit may be used as long as it has a large input impedance when viewed from the main line side, and can be configured by using, for example, an operational amplifier, a buffer amplifier, a driver amplifier. The input impedance may be several kΩ or more when the transmission impedance in the main line 8 is 50Ω, for example. For the purpose of converting impedance in this way, not only a circuit using an active element such as the above-mentioned amplifier but also a circuit using a passive element such as a transformer may be used.

Further, the interface IC 1 is arranged in a region of the backboard 2 which is sandwiched between the paralleled connectors 5. This area includes the surface of the backboard 2 (the side to which the substrate 3 is attached) and the surface of the backside (the side opposite to the substrate 3) (the backside). That is,
The interface IC 1 may be mounted only on the front side surface of the backboard 2 or may be mounted only on the back side surface. Of course, it may be mounted on both the front side and the back side. However, when the interface IC 1 is mounted on the front side of the backboard 2, the area on the backboard 2 is occupied by the connector 5, so that the area where the interface IC 1 can be mounted is larger than that on the back side. Becomes smaller.

An interface IC 4 having an interface circuit for transmitting and receiving signals is mounted on each board 3 attached to each of the plurality of connectors 5.
A branch circuit 9 for connecting the interface IC 4 and the connector 5 is formed on the substrate 3. The interface circuit includes, for example, a receiver circuit and a driver circuit.

In FIG. 1, the interface IC1 described above is used.
Are formed in a package shape having a narrow width in a certain direction. As a result, it is possible to deal with the connectors 5 provided on the backboard 2 at narrow intervals. For example, by forming the interface IC1 in a vertical package shape, the size in the width direction can be set to about 2 mm.

Therefore, the interface IC 1 can be mounted even on a backboard which is difficult to mount with a normal flat package shape. For example,
It is possible to support a backboard having a narrow pitch such that the connectors 5 are provided at intervals of about 1.5 cm.

The interface IC 1 may be mounted on the connector 5. For this purpose, for example, each connector 5 can be provided with a hole into which a lead for fixing an IC package is inserted, and an array of conductor surfaces corresponding to solder bumps. With this configuration, the branch line 9 formed on the substrate 3
Through the array of conductor planes to the backboard 2
It is connected to the main line 8 formed above.

Signal transmission in the backboard mounted as shown in FIG. 1 will be described with reference to FIGS. 2 and 3.

First, referring to FIG. 2, the case where a signal given to the main line on the backboard is transmitted to each substrate will be described.

In FIG. 2, the branch circuit 9 of each substrate 3 is connected to the main line 8 on the backboard 2 via the driver circuit 1D mounted on the interface IC 1 (see FIG. 1). In each board 3, the receiver circuit 4R mounted on each interface circuit 4 (see FIG. 1) is connected by the branch line 3 formed on each board 3.

Since each driver circuit 1D has a high impedance on the input side, that is, on the main line 8 side, the branch portion to which each driver circuit 1D is connected is
From the main line 8 it looks open. Therefore, the signal given to the main line 8 from a certain signal source is transmitted like a single line. As a signal source for giving a signal to the main line 8, for example, one of the substrates 3 connected to the backboard 2 or a substrate connected to another backboard connected to the backboard 2 or the like. Is mentioned.
In FIG. 2, the signal source is shown as a driver circuit 14.

On the other hand, there is a one-to-one single line from the output side of the driver 1D to the receiver circuit 4R.

Therefore, in the signal transmission on the main line 8,
The length of the branch line 9 can be ignored, and the influence of reflection at the branch portion is reduced.

Next, the case where a signal is transmitted from each substrate to the main line on the backboard will be described with reference to FIG.

In FIG. 3, the branch circuit 9 of each substrate 3 is connected to the main line 8 on the backboard 2 via the receiver circuit 1R mounted on the interface IC 1 (see FIG. 1). The driver circuits 4D mounted on the respective interface circuits 4 (see FIG. 1) are connected by the branch lines 3 formed on the respective substrates 3.

In each board 3, there is a one-to-one single line from the output side of the driver 4D to the receiver circuit 1R. The receiver circuit 1R that has received the signal from the driver circuit 4D sends the signal with an output impedance corresponding to the main line 8.

On the other hand, in the receiver circuit 1R which does not send a signal, the output side, that is, the main line 8 side is in a high impedance state. Therefore, the branch portion to which each receiver circuit 1R is connected looks open from the main line 8. Therefore, the signal given to the main line 8 is transmitted similarly to the single line. Then, for example, the receiver circuit 16 connected to the main line 8 can receive the transmitted signal.

Therefore, in the signal transmission on the main line 8,
The length of the branch line 9 can be ignored, and the influence of reflection at the branch portion is reduced.

As described above, by mounting the interface IC 1 having the interface circuit on the backboard 2, a line for branching to each substrate 3 (for example,
The influence of reflection on the branch line 9) can be reduced. Therefore, signals can be transmitted and received at high speed between the backboard 2 and each substrate 3.

Next, with reference to FIG. 8 and FIG. 9, the result of studying the signal transmission in the backboard configured by applying the present embodiment by using the simulation will be described.

In this simulation, the length of the branch line is 10 cm, and the period of the signal transmitted from the driver is 20 cm.
[Ns], the rise time of the signal is 1.3 [ns]
As (10% -90%), the signal waveform on the input side of the receiver is simulated.

First, the signal waveform transmitted by the backboard constructed by applying this embodiment will be described.

The simulation result shown in FIG. 9A shows that the transmission end 8T in the transmission line model shown in FIG.
3 shows a sending end waveform 100 input at 1 and a receiving end waveform 102 transmitted to the receiving end 9T.

In FIG. 9A, the receiving end waveform 102 is
The waveform is equivalent to the sending end waveform 100, and it is shown that the distortion of the waveform is avoided.

Next, for comparison, with reference to FIG. 8, a description will be given of signal transmission in a backboard to which a conventional mounting form is applied.

The simulation result shown in FIG. 8A shows that the transmission end 8T in the transmission line model shown in FIG.
2 shows a sending end waveform 100 input at 1 and a receiving end waveform 101 transmitted to the receiving end 9T.

In FIG. 8A, the receiving end waveform 101 is
The waveform is distorted with respect to the sending end waveform 100. When such a receiving end waveform 101 is sent to the substrate 3, it causes a circuit on the substrate 3 to malfunction. Therefore, the operation of the circuit becomes difficult with such a high-speed waveform.

It is considered that the above-mentioned waveform distortion is caused by the influence of reflection by the branch line. This is the sending end waveform 10
It is considered that, for the high frequency component included in 0, the transmission delay time corresponding to the length of the branch line (transmission line branched from the main line) of the component becomes longer than the rising time of the signal waveform.

In the backboard 2 to which the mounting form according to the present embodiment is applied, when transmitting signals to the plurality of substrates 3, it is possible to transmit high-speed signals with the influence of reflection reduced. Shown from the results.

Therefore, according to the present embodiment, the distributable signal on the backboard 2 can be speeded up. As a result, the data transfer rate can be increased.

As described above, the interface IC
By making 1 the vertical shape, it is possible to correspond to the backboard 2 in which the substrates 3 are provided at narrow intervals. Therefore, for high-density lines, it is possible to increase the speed of signals that can be distributed to each line. Therefore, high-speed data transfer and high-density data transfer are possible.

Next, a second embodiment of the present invention will be described with reference to FIG.

Since the basic structure of the backboard in this embodiment is the same as that of the first embodiment, the differences will be mainly described here.

In FIG. 4A, a plurality of connectors 5 for connecting the substrates 3 are arranged in parallel on the backboard 2 in this embodiment. In FIG. 4A, the connector provided on the left end is 5-1 and the connector on the right is 5-
Set to 2.

With reference to FIG. 4B, the pin arrangement of the connector pins in the connectors 5-1 and 5-2 of the backboard 2 will be described.

Here, the upward direction in the plane of FIG. 4B is the y direction, and the right direction in the plane of the paper is the y direction. In addition, in the pin arrangement of the connector pin 6 of the connector 5-1, 1
The coordinates corresponding to the No. pin are (x, y). The length in the horizontal direction is a, the length in the vertical direction is b, and the distance to the adjacent connector 5-2 is i.

At this time, the mounting area AP of the connector pin 6 in the connector 5-1 is (n =
For each n that is 0, 1, 2, ..., B), (x, y +
n) to (x + a, y + n). Further, for each m in which (m = 0, 1, 2, ..., A) in the y direction,
(X + m, y) to (x + m, y + b). Such a mounting area AP is expressed as (x, y) to (x + a, y + b) corresponding to the two dimensions of xy. The empty space AS sandwiched between the connector 5-1 and the connector 5-2 is (x + a, y) to (x + i + a, y + b) by the same notation. The area where the interface IC1 can be mounted is
This becomes the empty space AS.

From the shape of the connector 5, a << b
Also, i << b from the relationship between the shape of the connector 5 and the direction in which the connectors 5 are arranged in parallel. Therefore, the mountable area AS is an area having a flat shape in the vertical direction in which the vertical direction (x direction) is larger than the horizontal direction (y direction).

Therefore, in this embodiment, a << b, i
Paying attention to <<<< b, the flattening direction of the package shape of the interface IC1 is aligned with the flattening direction of the area AS.

That is, the interface IC1 is formed in such a shape that the relationship between the widths D and W of the package shape is D << W. Then, with respect to the direction of a, which is the direction of the minority arrangement of the connector pins 6, the interface I
The interface IC1 is mounted so that the direction of the width D of C1 is the same direction.

As a result, the connectors 5 (here,
(X + a, y) to (x + i + a, y +), which is an empty space AS between the connector 5-1 and the connector 5-2).
The interface IC1 can be mounted at a high density in the area b). Therefore, it becomes possible to deal with the connection of a large number of data in the connector 5. Therefore, even when there are many lines on each board 3, an interface circuit corresponding to each line can be mounted.

Further, by making the package shape of the interface IC1 the height H larger than the width D, the number of interface circuits mountable on the interface IC1 can be increased. Therefore, the interface circuit can be mounted with higher density.

Next, the above-mentioned mounting form will be described with reference to specific mounting conditions. That is, the mounting conditions are assumed as follows.

With respect to one backboard 2, 20 connectors 5 are arranged side by side at an interval of 1.5 cm. The pin arrangement of each connector 5 is 4 rows horizontally and 372 rows vertically.

The board 3 connected to each connector 5 has about 1000 signal pins per board.

The interface IC1 has 8 stones per stone.
The driver circuit of the circuit is mounted.

After mounting the connector 5 on the backboard 2, the empty space is about 1 cm in width (corresponding to i) and 60 cm in length (corresponding to b).

Under such mounting conditions, the number of interface ICs 1 that can be mounted will be examined.

Under the mounting conditions assumed as described above, since the number of data lines per board is about 1000, 1000 drivers are required to be mounted on the backboard 2. If a 20-pin IC package with eight driver circuits built in is used as the interface IC1 mounted on the backboard 2, 125 interface ICs need to be mounted.

Here, the package shape of the interface IC1 has a width D = 2 mm, a length W = 1.5 cm, and a height H.
When the size is about 5.6 cm, four pieces can be arranged in parallel in the horizontal direction and 32 rows can be mounted in the vertical direction. That is, a maximum of 128 interface ICs 1 can be mounted. Since the interface IC1 is an IC having eight circuits for one stone, it is possible to support up to 1024 data lines in a state where the above 128 devices are mounted.

Therefore, it is possible to deal with the substrate 3 in which the number of data is 1000.

Next, a case where a conventional mounting form is applied will be examined for comparison.

When a normal driver IC is used as the interface IC1, the package shape has a width D = 1c.
m, length W = 1.3 cm, height H = 2 mm.
In this case, 1 to the backboard 2 in the lateral direction (x direction).
Only 46 columns can be mounted in the row and vertical direction. Therefore, the maximum mountable number is 46. Therefore, since the number of driver circuits per IC is 8, the number of signals that can be handled is 368. This is much short of the above-mentioned 1000 lines.

As described above, the backboard 2 in this embodiment can be adapted to connect the substrates 3 having a large number of data lines. Since a large number of these data lines can be branched via the interface circuits (for example, the driver circuits described above), the signals distributed to the respective lines can be speeded up.

Further, even if a large number of interface circuits are mounted in this way, it is not necessary to widen the space between the substrates 3, so that high-density mounting of lines on the backboard 2 is not hindered.

Next, with reference to FIG. 5, an asynchronous transfer mode (ATM switch) in which the above-mentioned backboard 2 is mounted will be described as a third embodiment of the present invention.

In FIG. 5, the ATM switch 20 has a switch unit 2 for performing self-route selection in the asynchronous transfer mode.
2 and a line support unit 21 for supporting the connected line
And a control unit 24 for monitoring and controlling the connection state of the line.

The line interface 21 is constructed by including the backboard 2 and the substrate 3 in the second embodiment. A plurality of backboards 2 are prepared in the line interface 21 to support a large number of lines. These backboards 2 are connected to the switch unit 22.

The line interface 21 and the switch 22
Are housed in the exchange housing 25.

According to the present embodiment, high-speed signals can be distributed while avoiding the influence of reflection due to the branch of the transmission line on the backboard 2. Further, it is possible to cope with the increase in the number of boards 3 connected to the backboard 2 and the number of lines in each board 3. Therefore, even if the line density in the exchange increases, high-speed signal distribution can be realized.

Therefore, the data transmission capacity of the ATM exchange can be increased.

Next, with reference to FIGS. 6 and 7 and FIGS. 10 to 14, a description will be given of an IC package aspect of the interface IC1 (see FIG. 1) in the first and second embodiments. To do.

First, referring to FIGS. 10 to 14, the IC
The external structure of the package will be described.

In FIG. 10, the IC package 300 is shown.
Is a chip 30 on which a circuit for realizing a function is formed.
And a lead 32 for connecting the IC package 300 to another circuit, and a gold wire 31 for connecting the chip 30 and the lead 32.

The IC package 300 is formed in a vertical shape as a whole with the surface on which the leads 32 are provided facing down. This shape can have a width W narrowed (width D = about 2 mm), a length W = 1.5 cm, and a height H = 5.6 cm, for example.

The lead 32 is formed in a pin shape and can be inserted and attached through a through hole or the like. Then, with the pin-shaped lead 32 inserted in the through hole, connection and mounting are performed by soldering or the like.

Further, as shown in FIG. 11, the IC package 300 can be a surface mounting type in which the leads 32 are formed in a flat plate shape. Upon mounting, the leads 32 on both ends and the inner lead 32 are molded so that the leads 32 are bent in opposite directions. This makes it possible to stabilize the attitude of the IC package in the mounted state.

The lead 32 may be bent alternately between the adjacent leads 32 as shown in FIG.

Further, as shown in FIG. 13, the fixing pin 33 for fixing to the backboard is provided with the IC package 3.
00 can be provided at both ends of the mounting surface. Fixed pin 3
By fixing the IC package 300 to the backboard by means of 3, it is possible to mount without being restricted by the bending direction of the lead 32. For example, even if the IC package 300 is mounted with the leads 32 all bent in the same direction, the posture after mounting can be stabilized. The fixing pins 33 may be pin-inserted by forming through holes in the backboard, or may be surface-mounted.

As shown in FIGS. 11 to 13, the lead 3
In the case where the transmission characteristics of the backboard 2 (see FIG. 1) and the chip 30 are inserted into the through holes by forming the pin-shaped leads 32 in FIG. Can be improved compared to.

This is because, in the pin insertion type, the characteristic impedance may be disturbed at the portion inserted into the through hole, and the portion which penetrates the through hole and projects to the opposite side of the backboard 2 (see FIG. 1). It is considered that the transmission characteristics may be deteriorated due to the occurrence of parasitic capacitance. As the cause of the disturbance of the parasitic capacitance in the through hole, the capacitance parasitic in the through hole, the inductance of the lead pin, and the like are considered.

It is considered that such an influence can be avoided by adopting the surface mounting type, and the transmission characteristics are improved.

Further, in the embodiment shown in FIG.
As shown in FIG. 4, solder bumps 34 can be used instead of the leads 32. This IC package 30
0 indicates that the solder bumps 34 have BGA (Ball Grid)
Array) for surface mounting to achieve electrical connection,
The fixing pin 33 allows mechanical fixing by the IC package 300.

By surface mounting by BGA using the solder bumps 34, the transmission distance from the chip 30 to the backboard can be further shortened.

Next, referring to FIG. 7, the interface I
The internal structure of the C1 (see FIG. 1) IC package will be described.

In FIG. 7, a chip 30 on which an interface circuit for realizing the interface function is formed.
Is formed with a plurality of pads 36 for connecting each interface circuit of the chip 30 to the outside of the chip. Each pad 36 connects the IC package 300 to the outside via the gold wire 31 and the internal wiring 35. It is connected to the lead 32.

The pads 36 are formed on the peripheral edge along one side of the chip 30. And the tip 30
The side where the pad 36 is formed is the lead 32.
It is arranged so as to face the side where is formed. As a result, the length of the internal wiring 35 can be shortened. Therefore, the wiring length between the lead 32 and the chip 30 is shortened as a whole of the IC package 300.

Therefore, the line length from the interface circuit formed on the chip 30 to the main line 8 (see FIG. 1) formed on the backboard 2 (see FIG. 1) can be shortened. Therefore, the line length of the line branched from the main wiring is shortened, and higher-speed signal distribution becomes possible.

For comparison, an IC chip which follows the conventional chip layout will be described with reference to FIG. In the conventional chip layout, the pads 36 are formed along the four sides of the chip 30 at the periphery thereof. Therefore, for the pads formed along the three sides that do not face the side where the leads 32 are formed, the wiring length of the internal wiring 35 is long. This internal wiring 35
Is the IC package 30 on the backboard 2 (see FIG. 1).
When 0 is implemented, it acts as a branch line to the main line. For this reason, the branch line becomes longer according to the length of the internal wiring 35, so that the speed of a signal that can be transmitted is limited.

By constructing the IC package 300 of the interface IC1 (see FIG. 1) as described above, the length of the branch line with respect to the main line 8 in the backboard 2 (see FIG. 1) can be further shortened. be able to. As a result, the speed of signals that can be transmitted on the backboard 2 (see FIG. 1) can be further increased.

Further, by making the IC package 300 a surface mount type, it is possible to improve the transmission characteristics at the connecting portion of the leads 32. Therefore, backboard 2
(See FIG. 1), the speed of a signal that can be transmitted can be further increased.

[0118]

According to the present invention, it is possible to avoid the influence of reflection by the branch line and reduce the distortion of the receiving end waveform.
Therefore, the device can operate at high speed while the circuit operates normally.

Therefore, according to the present invention, in a backboard for transmitting signals to a plurality of substrates, by mounting interface ICs that can be mounted at narrow intervals on the backboard, high-speed signals can be transmitted without being affected by reflection, so that the device It is possible to speed up.

Further, by using the vertically long IC package, it is possible to deal with a backboard in which a large number of substrates are connected. Furthermore, by mounting the IC packages in an array, the number of interface ICs that can be mounted can be increased. This makes it possible to cope with the large number of lines connected to each board.

Further, by applying the above-mentioned backboard to an ATM switch, it is possible to handle signals of multiple lines and wide band.

Further, an IC package in which the internal wiring length from the interface surface to the chip is shortened is provided.
By using this, the branch line length can be further shortened. Therefore, a higher speed signal can be transmitted.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a backboard to which a first embodiment of the present invention has been applied.

FIG. 2 is a block diagram showing distributed signal transmission in the backboard to which the first embodiment of the present invention is applied.

FIG. 3 is a block diagram showing aggregated signal transmission on the backboard to which the first embodiment of the present invention is applied.

4A and 4B are explanatory views showing a configuration of a backboard to which the second embodiment of the present invention is applied, including (a) a perspective view showing an outline of the backboard, and (b) a connector pin arrangement and an interface IC. 3 is a top view showing the relationship with the arrangement of FIG.

FIG. 5 is an ATM to which a third embodiment of the present invention is applied.
It is a perspective view showing an exchange.

FIG. 6 is an explanatory diagram showing a chip layout inside a conventional IC package.

FIG. 7 is an explanatory diagram showing a chip layout inside an IC package to which the present invention is applied.

8A and 8B are simulation results obtained by analyzing a transmission waveform on a conventional backboard, and FIG. 8A is a graph showing a relationship between a transmission end waveform and a reception end waveform, and FIG. 8B is an explanatory diagram showing a transmission path model.

9A and 9B are simulation results of analysis of transmission waveforms in the backboard according to the first embodiment of the present invention, in which (a) a graph showing a relationship between a transmission end waveform and a reception end waveform, and (b) a transmission path model. It is an explanatory view shown.

FIG. 10 is a perspective view showing an outer structure of an IC package to which the present invention is applied.

FIG. 11 is a perspective view showing another external structure of an IC package to which the present invention is applied.

FIG. 12 is a perspective view showing another external structure of an IC package to which the present invention is applied.

FIG. 13 is a perspective view showing another external structure of an IC package to which the present invention has been applied.

FIG. 14 is a perspective view showing another external structure of an IC package to which the present invention has been applied.

FIG. 15 is a perspective view showing a configuration of a conventional backboard.

16A and 16B are block diagrams showing signal transmission in a conventional backboard, wherein FIG. 16A is a block diagram in the case of distribution, and FIG. 16B is a block diagram in the case of aggregation.

[Explanation of symbols]

1 ... Interface IC, 1D ... Driver circuit, 1R ...
Receiver circuit, 2 ... Backboard, 3 ... Substrate, 4 ... Interface IC, 4D ... Driver circuit, 4R ... Receiver circuit, 5-1, 5-2 ... Connector, 6 ... Connector pin, 7 ... Driver circuit, 8 … Main line, 8T… Sending end, 9…
Branch line, 9T ... Receiving end, 14 ... Driver circuit, 16 ... Receiver circuit, 20 ... ATM switch, 21 ... Line corresponding part,
22 ... switch part, 24 ... control part, 25 ... switch housing,
30 ... Chip, 31 ... Gold wire, 32 ... Lead, 33 ... Package fixing pin, 34 ... Solder bump, 35 ... Internal wiring, 36 ... Pad, 100 ... Send waveform, 101, 102
... Receiving end waveform, 300 ... IC package.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04L 12/28 H04L 25/02 H04Q 1/02 H04Q 3/00 H04L 12/40

Claims (10)

(57) [Claims] 1. Distributing signals to multiple boards to be connected
A backboard for connecting the plurality of boards, respectively.
Connector and a wire common to the above connectors
Path and impedance for converting impedance
A converter is provided, and the connector is parallel to one surface of the backboard.
Multiple impedance converters are installed on the backboard.
Are installed in the area sandwiched between the side-by-side connectors.
It is, the connector pins of each connector, the impedance transformation
To the common line from the line side via
Be connected to have a high impedance to the force.
A backboard featuring. 2. The backboard according to claim 1 , wherein a plurality of the impedance converters are packaged.
Is housed, said package it the impedance converter
The lead for connecting to the outside is 1 of the package.
One side is lined up and the lead is lined up in the longitudinal direction of the connector.
It is arranged on the backboard in a posture that follows the direction.
Backboard to collect. 3. The backboard according to claim 2, wherein the package is connected to a common impedance converter.
Characterized by the following leads arranged next to each other
And backboard. 4. The bar according to claim 2,
Package containing a plurality of the above impedance converters
A plurality of packages , the plurality of packages being provided in the longitudinal direction of the connector
A backboard characterized by being lined up alongside. 5. The bag according to claim 2, wherein
Package containing a plurality of the above impedance converters
Multiple packages are provided on the matrix.
A backboard characterized by being installed. 6. The bar according to claim 4,
In the above-mentioned package , in the above package, the lead has a flat conductor, and
Characterized by being formed by either of solder bumps
Backboard to do. 7. The bag according to any one of claims 2 to 6.
Board, multiple impedance converters housed in the above package
Are formed on a common chip, and the impedance converter on the chip is connected to the outside of the chip.
The pad for connection is the circumference along one side of the chip.
The chip is formed on an edge portion, and the chip has a side on which the pad is formed on a peripheral portion,
Face the side of the package where the leads are lined up.
It is stored in the above package in a different posture
And backboard. 8. A plurality of transmission lines for connecting to a line are connected.
To exchange data communication on multiple lines
Claims: In an asynchronous transfer mode (ATM) switch of the above, a line interface for connecting a plurality of the transmission lines is provided.
A backboard according to any one of 1 to 7 is provided.
An asynchronous transmission mode switch characterized by and. 9. A signal is distributed to a plurality of substrates to be connected.
In the backboard for the main line, the main line and multiple branch lines that branch from the main line
A distribution line having a board is formed, and a connector having a board connecting portion for connecting the boards is provided.
Several of them are arranged side by side, and the connector pins of each connector are connected to the above branch line.
Each of the above branch lines is a part of the path that is connected to the main line.
In the first section, which is
Has a larger characteristic impedance than the impedance,
Also, the first section and the side where the connector pin is connected
Impedance converter between the second section which is the section
And the impedance converter is viewed from the side of the first section.
The second section side corresponds to the open end, and the second section
The characteristic impedance between the
The equivalent of the characteristic impedance of the line
Characterized by connecting the first section and the second section
Backboard. 10. The backboard according to claim 9, wherein the impedance converter is provided in the connector.
The connector pin side wiring in the connector internal wiring
And a board connecting portion side wiring are connected.
Backboard.