JPH03231497A - Multilayer printed wiring board - Google Patents

Abstract

PURPOSE:To reduce a crosstalk caused by crossed interconnections by a method wherein an insulating layer is formed to be thicker than other signal-layer pairs and a signal-layer pair in which a signal line having a comparatively long section length has been wired is installed at a signal-line layer. CONSTITUTION:The distance (a) between a signal layer 2 and a signal layer 3 in a signal-layer pair 8 is set to be longer than the distance (b) between a signal layer 4 and a signal layer 5 in a signal-layer pair 9. A signal line having a comparatively long section length is wired in a signal-line layer of the signal- layer pair 8. By this constitution, the signal line which has been wired in the signal-layer pair 8 is hardly influenced by an interlayer crosstalk as compared with a signal line which has been wired in the signal-layer pair 9. When a wiring operation is executed to the signal-layer pair 8 hardly influenced by a crosstalk by crossed interconnections preferentially from a long interconnection, it is possible to design an interconnection which is hardly influenced by the crosstalk by the crossed interconnections as a whole substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multilayer printed wiring board, and particularly to a structure of a signal layer bare consisting of adjacent signal wiring layers.

[Conventional technology]

Conventionally, as a multilayer printed wiring board, there is a board in which a plurality of signal layer bares made of two signal wiring layers (hereinafter simply referred to as signal layers) that are adjacent to each other with an insulating layer interposed therebetween are stacked. In the signal layer, signal lines with relatively long and short signal lines (section length) in the same signal layer are wired under the same conditions, and these are not mixed regardless of the length of the section. Ta.

In this type of multilayer printed wiring board, the distance between the signal layers (the thickness of the insulating layer) in each signal layer bare is all set to be constant. Documents related to this prior art include "Electronic Materials 1988゜10 P65-71
(Industrial Research Council)”.

[Problem to be solved by the invention]

However, in the multilayer printed wiring board described above, both signal lines with long sections and short signal lines are wired under the same conditions, so in signal lines with long sections, other wiring that intersects across the insulation layer There will be more.

When signal lines cross each other in this way, crosstalk occurs. In the past, this crosstalk amount was often negligible because it was small compared to the crosstalk amount of parallel wiring, but in recent years, as wiring has become denser, signal lines with long sections are As the number of locations where wires intersect with each other has increased, crosstalk caused by these wires crossing each other has become a problem that cannot be ignored.

In order to reduce this crosstalk, it is possible to increase the distance between the signal layers of the signal layer bares, but if the distance between the signal layers of all the signal layer bares is increased, the entire board becomes thicker and it becomes difficult to process holes. , a problem arises in that the yield is reduced.

[Means to solve the problem]

In the printed wiring board according to the present invention, at least one of the plurality of signal layer bears is formed with an insulating layer thicker than other signal layer bears, and the signal line layer of the signal layer bear has a comparatively long section length. This is a long signal wire.

[Function] Signal lines with relatively long section lengths are wired with a large interlayer distance from signal lines of other signal layers.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3.

FIG. 1 is a perspective view showing a schematic configuration of a multilayer printed wiring board according to the present invention, FIG. 2 is a plan view showing an enlarged wiring part, and FIG. 3 is a wiring procedure for a multilayer printed wiring board according to the present invention. It is a flowchart which shows. In these figures, ■ indicates a multilayer printed wiring board according to the present invention, and this multilayer printed wiring board 1 has signal layers 2 to 5 on which signal lines are respectively wired, a ground layer 6, a power supply layer 7, etc. has
Each layer is laminated with an insulating layer (not shown) interposed therebetween. 8 and 9 indicate signal layer bears, and this signal layer bear 8 is formed from the signal layer 2 and the signal layer 3 which are adjacent to each other.
Further, the signal layer bare 9 is composed of the signal layer 4 and the signal layer 5. In the multilayer printed wiring board l shown in this embodiment, these signal layer bears 8.9 are used to perform wiring between the terminals of the mounted components. Then, the signal layer bare 8
The distance a between the signal layer 2 and the signal layer 3 (interlayer distance) a is larger than the interlayer distance of the signal layer bare 9. In other words, the insulating layer is set to be thick, and the signal line wired to the signal layer bare 8 (not shown) is less susceptible to interlayer crosstalk than that wired to the signal layer bare 9. Furthermore, between the signal layer bare 8 and the signal layer bare 9, there is a ground layer 6 and a power layer 7, and since these play the role of electromagnetic shielding, the above-mentioned interlayer crosstalk can be ignored. ing. Next, interlayer crosstalk will be explained using FIG. 2.

In FIG. 2, the same or equivalent members as those explained in FIG. 1 are given the same reference numerals and detailed explanations will be omitted. In FIG. 2, 10 is a signal line wired to the signal layer 2, 11 is a signal wire wired to the signal layer 3, and these are connected to the peer hole 1 which is a relay through hole that penetrates the insulating layer.
Connected via 2. 13 is a component terminal connected to the signal line 10, and 14 is the signal! This is a component terminal connected to 11. That is, the component terminal 13 shown in the figure is connected from the signal line 10 on the signal layer 2 to the component terminal 14 via the peer hole 12 and the signal line 11 on the signal layer 3. Note that 15 indicates another signal line wired on the signal layer 2, and 16 indicates another signal line wired on the signal layer 3.

The signal line 10 intersects with the signal line 16 wired on the signal layer 3, and the signal line 11 intersects with the signal line 15 wired on the signal layer 2, and crosstalk occurs at these intersections. Occur. However, since the distance between the signal layer 2 and the signal layer 3 is set larger than the interlayer distance of the signal layer bear 9, the signal layer bear 8 can be made less susceptible to the effects of glabellar crosstalk. In the present invention, a signal line having a relatively long section length is wired to the signal layer bare 8 described above.

This wiring procedure will be explained using FIG. 3. As for the wiring procedure, first, in the processing box 21 shown in FIG. 3, the wiring section group 22 that requires connection is rearranged in descending order of the length of each wiring section.

Next, in the processing box 23, the wiring sections are taken out one by one from the wiring section group 24 rearranged in descending order of Mannha-notan length, and are placed on the signal layer bare where the interlayer distance is larger than the others (in this embodiment, (on the signal layer bare 8).

Therefore, as mentioned above, by preferentially wiring long wires using bare signal layers that are less susceptible to crosstalk due to wire crossings (large interlayer distance), the effect of crosstalk due to wire crossings can be minimized on the board as a whole. It is possible to design wiring that makes it difficult to receive signals.

〔Effect of the invention〕

As explained above, in the multilayer printed wiring board according to the present invention, at least one of the plurality of signal layer bears is formed with an insulating layer thicker than other signal layer bears, and the signal line layer of this signal layer bear is Because a signal line with a relatively long section length was wired,
Signal lines with relatively long section lengths are wired with a large interlayer distance from signal lines of other signal layers. Therefore, a wiring design that is not easily affected by crosstalk caused by crossing signal lines can be performed, and a highly reliable multilayer printed wiring board with suppressed crosstalk can be formed while suppressing an increase in thickness.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a multilayer printed wiring board according to the present invention, FIG. 2 is a plan view showing an enlarged wiring part, and FIG. 3 is a wiring procedure for a multilayer printed wiring board according to the present invention. It is a flowchart which shows. ■・・・Multilayer printed wiring board, 2.3, 4.5...
Signal layer, 6... Ground layer, 7... Power layer, 8
9.9. , signal layer bare. 10.11...Signal line.

Claims (1)

[Claims] In a multilayer printed wiring board in which a plurality of signal layer bears each consisting of a pair of signal line layers adjacent to each other via an insulating layer are provided with an electromagnetic shielding layer interposed therebetween, at least one of the signal layer bears is connected to another signal line layer. A multilayer printed wiring board characterized in that an insulating layer is formed thicker than that of a layer bare, and a signal line having a relatively long section length is wired to the signal line layer of the signal layer bare.