JPS5939919B2 - multilayer wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in multilayer wiring boards used in electronic computers and the like.

In electronic devices such as electronic computers, there is a tendency to use multilayer wiring boards for mutual wiring of logic elements such as integrated circuits and mutual wiring of circuit boards.

In particular, there are increasing opportunities to use substrates with four or more signal wiring layers. FIG. 1 is a schematic diagram of a conventional board having four signal wiring layers.

1a, Ic, Ie, and Ig are signal wiring layers, and in order to reduce crosstalk and control characteristic impedance,
Power supply layers lb, ld, and If are interposed between each signal wiring layer.

The running directions of the patterns 2 of the signal wiring layers 1a, lc, le, and lg are alternately changed to the X direction, the Y direction, the X direction, and the Y direction, as shown in the figure. Then, the signal wiring layer 1a (
The patterns of the upper surface layer) and the signal wiring layer lc (the inner layer corresponding to the surface layer 1a) are interconnected by via holes as necessary, and the patterns of the lower surface layer lg and the corresponding inner layer Ie are interconnected as necessary. The necessary wiring is achieved by connecting the patterns through via holes as necessary. Now, the main components mounted on such multilayer wiring boards, such as connectors, integrated circuits, and sockets for integrated circuits, are generally long and thin, and their terminal pins are arranged in one or two rows in the longitudinal direction. Arranged.

In view of mounting space and the like, such mounted components are generally arranged in the same direction and lined up in the width direction. That is, as shown in FIG. 2, a large number of components 4 are arranged in the X direction of the multilayer wiring board 3, and a limited number of components 4 are arranged in the Y direction. By the way, when designing a pattern for a multilayer wiring board, it goes without saying that the signal path should be shortened as much as possible, but the following points must also be kept in mind.
First, at least a portion of the wiring pattern connected to the pin hole into which the terminal pin of the component is inserted needs to be exposed on the surface layer. This is to facilitate wiring changes after pattern design by cutting the surface layer pattern as necessary. In fact, electronic computers, etc.
It is often necessary to partially change the logic after designing, and there are many cases where it is necessary to change the wiring by cutting the pattern. Further, it is desirable that the exposed position of the wiring pattern on the surface layer be selected near the pin hole to which it is connected.

This is to bring the cutting position of the wiring pattern closer to the pin hole and to shorten the length of the pattern (residual pattern) remaining between the cutting position and the pin hole as much as possible. If the wiring pattern is exposed on the surface layer at a position far from the pin hole, a long residual pattern will inevitably be produced when the wiring pattern is cut at that position. This residual pattern is not on the surface layer but on the inner layer and cannot be removed. If a long residual pattern exists, it can have negative effects such as distorting the waveform of the pulse on the wiring pattern connected to it and increasing propagation delay time. Now, the conventional board shown in Figure 1 When components are arranged and mounted as shown in FIG. 2, if a pattern is designed taking the above-mentioned points into consideration, the following problems arise.

In the case of a component arrangement as shown in FIG. 2, the signal flow in the X direction is normally overwhelmingly larger than the signal flow in the Y direction.

Therefore, the upper surface layer 1a and the corresponding inner layer 1
The appearance of the pattern c is, for example, as shown in FIG. Third
In the figure, white circles 5 indicate pin holes, and thick solid lines 6 indicate surface layer 1a.
The upper pattern, broken line 7, is the pattern on the inner layer 1c.

Further, the surface layer pattern and the inner layer pattern are connected by inserting a through hole pin into a via hole (through hole), and the through hole pin is indicated by a black circle 8. As mentioned above, since the signal flow is overwhelmingly greater in the X direction than in the Y direction, most of the wiring patterns for interconnecting pin holes run in the X direction.

Further, the pattern direction of the upper surface layer is the x direction. Therefore, as can be easily understood from the figure, most of the wiring patterns can be formed on the surface layer, and the conditions for pattern design described above can be easily satisfied. However, it is not easy to design a pattern that satisfies the above conditions for the lower surface layer 1g and its inner layer 1e.

This will be explained with reference to FIG. Note that the symbols are the same as in FIG. 3, 5 is a pin hole, 6 is a surface layer pattern,
7 indicates an inner layer pattern, and 8 indicates a through-hole pin. The pattern direction of the lower surface layer 1g is the Y direction.

Therefore, when attempting to expose the wiring pattern to the surface layer near the pin hole, the wiring pattern for signal flow in the X direction, which has an overwhelmingly large number of wires, is different from the surface layer pattern in the Y direction, as shown in the figure. It must be formed in combination with the inner layer pattern in the X direction, which causes an increase in the wiring pattern length due to the detour, and also causes an increase in signal propagation delay time. Since there are many detours and a large number of via holes are required for pattern connection between the surface layer and the inner layer, the patterning rate is often unavoidable. Furthermore, it is often practically impossible to expose all the wiring patterns to the surface layer in the vicinity of the connection pin holes, making it difficult to change the wiring and easily leaving long residual patterns when cutting the patterns. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a multilayer wiring board that solves the drawbacks of the conventional multilayer wiring board as described above.

In order to achieve this object, the main feature of the present invention is that patterns are run in the direction perpendicular to the pin arrangement direction of the main mounted components on both the upper and lower surface layers of the multilayer wiring board.

FIG. 5 shows an example of a multilayer wiring board according to the present invention.

In the figure, the pin arrangement direction of the main mounted components is the Y direction, and in the signal wiring layer 10a1 which is the upper surface layer and the signal wiring layer 10g which is the lower surface layer, the pattern 2 is
runs in the X direction.

Pattern 2 of signal wiring layers 10c and 10e, which are inner layers for surface layers 10a and 10g, respectively, runs in the Y direction. 10b, 10d, and 10f are all power supply layers.

It goes without saying that the above-mentioned layers are insulated by an insulating layer (not shown). However, when components are mounted on the board of the present invention in the arrangement shown in FIG.
The set of the upper surface layer 10a and its corresponding inner layer 10c and the set of the lower surface layer 10g and its corresponding inner layer 10e are both pattern designs in the set of the upper surface layer and its corresponding inner layer of the conventional substrate in FIG. The above can be considered to be the same condition.

Therefore, it is possible to avoid an unfavorable wiring pattern as shown in FIG. 4 and to design a preferable wiring pattern as shown in FIG. 3. Therefore, various problems with conventional substrates can be easily solved. Although the above embodiment has four signal wiring layers, it goes without saying that the present invention can be similarly applied to a substrate with three or five or more layers and produce the same effect. Further, the configuration other than the feature points of the present invention shown in the above embodiments may be the same as the conventional one. As described above, according to the present invention, it is possible to easily create a multilayer wiring board that has a wiring pattern that satisfies not only the requirements regarding signal propagation characteristics but also the requirements regarding wiring changes and has an improved patterning rate. It can be achieved and the effect is remarkable.

[Brief explanation of drawings]

Figure 1 is a diagram showing a schematic configuration of an example of a conventional multilayer wiring board, Figure 2 is a diagram showing a general arrangement of components on a multilayer wiring board, and Figure 3 is the upper surface of the conventional board in Figure 1. FIG. 4 is a diagram showing an example of the wiring pattern in the lower surface layer and the corresponding inner layer of the conventional board of FIG. 1. FIG. 5 is a diagram showing an example of the wiring pattern in the layer and its corresponding inner layer. FIG. FIG. 1 is a diagram showing a schematic configuration of an example of a wiring board. 2...Pattern, 4...Mounted parts, 5
...Pin hole, 6...Surface layer pattern,
7...Inner layer pattern, 8...Through hole pin, 10a, 10c, 10e, 10g...
- Signal wiring layer, 10b, 10d, 10f... power supply layer.

Claims (1)

[Claims] 1 In a multilayer wiring board in which multiple wiring layers are laminated, the patterns of two wiring layers (external wiring layers) located at the top and bottom layers and exposed to the outside are mounted in the same direction and on the multilayer wiring board. The pattern of the internal wiring layer facing each of the two external wiring layers runs parallel to the pin arrangement direction of the main mounted components. Multilayer wiring board.