JPH07240600A - Method for wiring equal length to electrical length - Google Patents

Abstract

PURPOSE:To provide a method for wiring an equal length to an electrical length which can transmit a simultaneous operation signal by bending a wiring to compensate for a difference between a wiring length and an electrical length. CONSTITUTION:A trace (A) comprises the lead frame 5 of a first IC (A), a wiring (A) wired in a zigzag form and the lead frame 6 of a second IC chip (A). A trace (B) comprises the lead frame 7 of a first IC (B), a wiring (B) including a stretched wiring and the like and the lead frame 8 of a second IC chip (B). An electrical length is shortened by induction or reflection in the corner. For that reason, since the number of corner is larger in the trace (A), it is necessary to make the wiring length longer in the trace (A). The wiring of the trace (A) is made longer by a difference in the number of corner between the trace (A) and the trace (B) by examining by what length the electrical length is shortened for every one corner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for wiring electrical lengths of equal length in a printed wiring board used for communication equipment or the like, in which the propagation delay times of a plurality of wiring lines for transmitting simultaneous operation signals are matched. Is.

[0002]

2. Description of the Related Art In a substrate on which high-speed signals run, problems such as delay, reflection, and crosstalk generated in wiring cannot be ignored. For this reason, the wiring needs to be treated as a transmission line, not just a connection. Multiple simultaneous operation signals, for example
In a high-speed digital circuit pattern that transmits clocks and data via different paths, it is necessary to match the propagation delay time of each signal.

The conventional wiring in such a case is simply made simultaneously in order to equalize the difference in the length of the lead frame in the IC and the difference in the wiring length due to the wiring of the wiring on the printed wiring board. When the wiring for the operation signal was extended, the wiring was made to have the same length. When the wiring length of one wiring is extended by routing the wiring or the like, the other wiring is also arranged in a zigzag manner, so that the wiring is lengthened by the extension.

[0004]

However, when the wirings for the simultaneous operation signals are extended to have the same wiring length, the increase in the wiring length due to bending and the increase in the electrical length are actually equal to each other. However, there was a difference in propagation delay time. Therefore, high-speed digital signals transmitted to a plurality of wirings were not transmitted at the same time. This has been confirmed by experiments and the like.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide an electrical length equal length wiring method capable of correcting the difference between the wiring length and the electrical length due to bending of the wiring. To aim.

[0006]

A method for equal-length wiring of a pattern in which the shape of the wiring of the first path is determined in a digital circuit in which a plurality of simultaneous operation signals are transmitted through the respective paths is described in the first method. According to the wiring shape of the route, the wiring shape of the second route is determined so as to be equal to the electrical length of the wiring of the first route. Further, in this wiring method, the wiring length of the wiring of the second path is appropriately determined according to the shortening of the propagation delay time that occurs when the digital signal passes through the corner of the second wiring. Alternatively, in this wiring method, the corner angle and the wiring length of the wiring of the second path are appropriately determined.

[0007]

[Function] It is assumed that there is a wiring A and a wiring B in a circuit pattern that requires transmission of simultaneous operation signals. First, the shape of the wiring B having a relatively low degree of freedom in wiring and a high packing density of ICs and the like is determined. Since the wiring A has a relatively high degree of freedom in wiring, it is arranged in a zigzag manner in order to equalize the electrical length with the wiring B. The wiring length of the wiring A is the wiring length of the wiring B plus the wiring length corresponding to the difference in electrical length. The wiring length to be extended is calculated from the difference in the number of corners of the wiring A and the wiring B by calculating the wiring length with respect to the reduction of the propagation delay time generated in one corner.

[0008]

[Example] A printed wiring board on which two ICs are mounted is assumed. Between the two ICs, the wiring of the two routes of traces A and B is provided.
Here, the trace represents the physical length of the wiring.

FIG. 1 shows a pattern diagram of the first embodiment.
First, the trace A is connected to the printed wiring board from the first IC chip 3 inside the first IC 1 through the lead frame 5 of A of the first IC. In the printed wiring board, it is connected to the lead frame 6 of A of the second IC, which comes out of the second IC chip 4, through the wiring A arranged in a zigzag pattern. The second IC chip 4 is inside the second IC 2.

Next, the trace B is connected to the printed wiring board from the first IC chip 3 inside the first IC 1 through the lead frame 7 of B of the first IC. In the printed wiring board, the second I
It is connected to the B lead frame 8 of the second IC that comes out of the C chip 4.

It is assumed that the trace A is the sum of the length of the A lead frame 5 of the first IC, the length of the wiring A, and the length of the A lead frame 6 of the second IC. Trace B is
The length of the lead frame 7 of B of the first IC, the length of the wiring B,
And the sum of the lengths of the lead frame 8 of B of the second IC, trace A> trace B.

Generally, when a high speed digital signal passes through a corner, the electrical length is shortened. It is thought that this is because a phenomenon called induction or reflection occurs. As described above, it has been confirmed by experiments that the electric length is shortened by the presence of the corner.

Using a zigzag pattern as shown in FIG. 2, the shortening of the electrical length at the corner was examined. High-speed digital signals are transmitted in a linear pattern, a zigzag pattern with 12 corners, and a zigzag pattern with 20 corners. The transmission time at this time is measured and compared for each pattern type, which is shown in FIG. The total length of these patterns was 228.6 mm.

As shown in FIG. 3, the larger the number of corners, the shorter the propagation delay time. From this, in the circuit pattern that requires the transmission of simultaneous operation signals, the cause of the difference in propagation delay time that occurs when the actual wiring length is made equal when the wiring is extended is that the high-speed digital signal passes through the corner. It is thought to have occurred in.

First, it was examined how much difference in electrical length there was in one corner as compared with the case where the pattern was straight.
Of the experimental values in FIG. 3, the embodiment will be described here by taking the case of a pitch of 5.08 mm as an example. A glass cloth-based epoxy resin printed wiring board was used in the experiment, and the frequency of the set input signal was 622 Mb / s. When the pitch is 5.08 mm,
The propagation delay time at 12 corners is 1481.3 ps, and the propagation delay time at 20 corners is 1469.9 ps. This difference in propagation delay time is 11.4 ps. The difference in the number of corners at this time is 8 corners. In other words, when the pitch is 5.08 mm, the propagation delay time per corner is reduced by about 1.4 ps.

Next, the propagation delay time when a high-speed digital signal is transmitted in a linear pattern is 1497.3 ps. This is the propagation delay time when a high-speed digital signal is transmitted in a 228.6 mm linear pattern. From this, the wiring length corresponding to a reduction of 1.4 ps in propagation delay time per corner is about 0.214 mm. That is, in a wiring pattern having corners such as a zigzag pattern, the wiring length may be extended by 0.214 mm per corner in order to make the propagation delay time equal to that of the linear pattern.

In the case of the first embodiment, the corner of the wiring A is 2
Since there are 0 times and the wiring B has two corners, the difference in the number of corners is 18. In other words, 0.214 (mm) x 18 = 3.85 (m
m) may be extended at a straight line portion of the connection of the wiring A to the lead frame of the IC chip, a zigzag wiring portion, or the like, which is easy to adjust. Since this zigzag pattern has a total length of 228.6 mm, the total length of 3.285 mm is 232.45 mm,
It is the full length of the zigzag pattern of A.

This value is a calculated value at a frequency of 622 Mb / s. Generally speaking, since the propagation delay time is a function of frequency, it is necessary to calculate a specific value of the wiring length for each frequency.

As described above, the difference in propagation delay time can be easily adjusted by extending the wiring in accordance with the number of corners of the zigzag pattern.

A pattern diagram of the second embodiment is shown in FIG. As shown in FIG. 4, the corner portion of the wiring 11 of the trace A ′ of this wiring is formed at α = 45 degrees instead of bending the linear pattern at 90 degrees.

A high-speed digital signal was transmitted to the 90-degree crank pattern shown in FIG. 5 (a) and the 45-degree crank pattern shown in FIG. 5 (b), and the propagation delay time was examined. FIG. 6 shows the relationship between the pattern type of the crank pattern and the propagation delay time. The propagation delay time in FIG. 6 is converted into the transmission time per 1 m. As is apparent from this, the propagation delay time when the pattern is a straight line approaches 45 degrees when the pattern is 45 degrees, as compared with when it is 90 degrees. That is, the propagation delay time changes depending on the crank angle, and the smaller the crank angle, the larger the propagation delay time.

Calculation will be made at a pitch of 2.54 mm in FIG. Since this is a measured value when the crank pattern is bent once, that is, twice, it is assumed that it is applied as it is as two corners of the zigzag pattern. Comparing the difference between the propagation delay time of the straight line pattern and the propagation delay time at 45 degrees with the difference between the propagation delay time of the straight line pattern and the propagation delay time at 90 degrees, the difference at the time of 45 degrees Is 1/2 of the difference at 90 degrees. In the first embodiment, it is calculated that 0.214 mm of wiring should be extended for each 90-degree corner, so when the corner portion is 45 degrees as shown in FIG. 1/2 of
Just extend the 0.107mm wiring. Also, since the wiring B has two corners of 90 degrees, the wiring A has a width of 0.107 × 20−0.214 × 2.
= 1.71mm extension is enough.

If the trace A'is the sum of the length of the A lead frame 5 of the first IC, the length of the wiring A ', and the length of the A lead frame 6 of the second IC, trace
A '<Trace A. This is effective when the wiring length and the mountable space are limited.

FIG. 7 shows a pattern diagram of the third embodiment.
It has been found that when a high-speed digital signal passes through a corner, signal reflection and induction occur and the propagation delay time is shortened. Therefore, if the number of corners is reduced, the reduction of the propagation delay time of the entire pattern becomes small. Also in this case, it is sufficient to extend 0.214 mm per corner as in the first embodiment. However, since the total number of corners of wiring A '' is 12 and the number of corners of wiring B is 2, the total wiring length is
You can extend it by 2.14mm. Trace A '' is the A of the first IC
If the length of the lead frame 5 and the length of the wiring A ″ and the length of the lead frame 6 of the second IC are trace A ″ <trace A, the total length of the wiring is limited. It is effective when. Further, when the number of corners is small, the error becomes small, and there is an effect that a plurality of simultaneous operation signals can be easily transmitted.

[0025]

As described above in detail, since the wiring method of the wiring board of the high speed digital circuit pattern having the simultaneous operation signal is as described above, the wiring length is changed according to the number of corners of the zigzag pattern. Therefore, it is possible to easily correct the difference in propagation delay time generated in the corner section.

[Brief description of drawings]

FIG. 1 is a pattern diagram of a first embodiment of the present invention.

[Figure 2] Zigzag pattern

FIG. 3 Relationship between zigzag pattern type and propagation delay time

FIG. 4 is a wiring of a second embodiment of the present invention.

[Fig. 5] Crank pattern

FIG. 6 Relationship between crank pattern type and propagation delay time

FIG. 7: Wiring of the third embodiment

[Explanation of symbols]

 1 1st IC 2 2nd IC 3 1st IC chip 4 2nd IC chip 5 A leadframe of 1st IC 6 A leadframe of 2nd IC 7 B of 1st IC Lead frame 8 B lead frame of the second IC

Claims (3)

[Claims] 1. A wiring pattern of a wiring pattern in a digital circuit in which a plurality of simultaneous operation signals are transmitted through respective paths, in a method of equal length wiring, the shape of the wiring of the first path is determined and the wiring of the first path is determined. An electrical length equal-length wiring method, which is a wiring method for determining the shape of the wiring of the second path according to the shape of the wiring. 2. The wiring length of the wiring of the second route is set to that of the wiring of the first route in accordance with the reduction of the propagation delay time which occurs when a digital signal passes through a corner of the second wiring. The electrical length equal length wiring according to claim 1, wherein the wiring length is appropriately determined based on a difference in the number of corners of the wiring of the second path. 3. The electrical length equal length wiring according to claim 1, wherein the corner angle and the wiring length of the wiring of the second path are appropriately determined.