JP2004207949A - Transmission line - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission line which can be formed, without increasing the number of manufacturing processes, is small in signal deterioration caused by crosstalk and is capable of high-density wiring, and has proper radiofrequency transmission characteristics. <P>SOLUTION: There are provided pairs of wiring conductors composed of signal conductors (2a, 3a, 4a) and pairing wiring conductors (2b, 3b, 4b), which either form closed-loop circuits with the signal conductors, or become pathways for return current, and are larger than the signal conductors in conductor width, opposed to each other with a dielectric (1) in between. The two or more pairs of wiring conductors are arranged side by side so that a plurality of signal conductors, or pairing wiring conductors do not adjoin each other. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transmission line capable of transmitting a high-frequency signal emitted from a semiconductor chip or a semiconductor package having a high driving frequency, or an analog high-frequency element for wireless LAN or Bluetooth without signal deterioration due to crosstalk. is there.
[0002]
[Prior art]
Conventionally, when a high-speed electric signal is transmitted, a microstrip line, a strip line, or the like has been generally used. For example, as shown in FIG. 7, three signal lines S are arranged in parallel in the dielectric 100, and a ground plane G is provided facing the signal lines S. However, as signal speeds have been increased to the gigahertz band and electronic devices have become smaller and smaller, crosstalk due to high-density wiring has inevitably become a problem. In order to reduce crosstalk, a stacked pair line structure as shown in FIG. 8 has been devised. In the dielectric 100, signal lines 102a, 103a, and 104a, and paired wirings 102b, 103b, and 104b that form a closed loop circuit with each of the signal lines facing the signal lines or that form a path through which a return current flows are formed. I have. The pair wires 102b, 103b, 104b play the same role as the ground plane G in FIG. In such a configuration, since the return current for the signal line flows only through the paired wires facing each other, the spread in the horizontal direction is smaller than the return current flowing in the ground plane G, that is, the spread of the electromagnetic field is smaller in the horizontal direction. Therefore, crosstalk is reduced. However, if the signal lines 102a, 103a, 104a and the pair wirings 102b, 103b, 104b are not completely opposed to each other and are displaced left and right, the characteristic impedance becomes unstable, and even if the crosstalk is reduced, The reflection of the signal line itself increases, and high-frequency signals cannot be transmitted. In order to eliminate this problem, when a stacked pair line structure is practically used, a configuration as shown in FIG. 9 is adopted. In the dielectric 105, signal lines 106a, 107a, and 108a, and paired wirings 106b, 107b, and 108b, which are wider than the signal lines, are formed opposite to the signal lines. The pair wirings 106b, 107b, and 108b must have at least a larger tolerance in the manufacturing position of the wiring than the signal lines 106a, 107a, and 108a. Further, the space Sp between the paired wirings cannot be narrowed below the wiring manufacturing limit. With such a configuration, both the reflection of the signal line itself and the crosstalk with the adjacent wiring can be suppressed to a low level. Further, as a method of reducing crosstalk, a method of not only providing a ground plane at a position facing a signal line but also providing a ground wall between adjacent wirings has been devised.
[0003]
[Patent Document 1]
JP 08-125412 A
However, in the configuration as shown in FIG. 9, since the pair wirings 106b, 107b, and 108b need to be thickened, there is a serious problem that the wiring density of the signal lines is reduced. In high-speed signal transmission, the number of wirings increases, so high-density wiring is indispensable, which is a very serious drawback. In addition, the method of providing a ground wall between adjacent wirings is not practical because, although theoretically possible, the manufacturing process is significantly increased as compared with a normal transmission line. That is, a step of forming a groove immediately below a signal line, a step of forming a ground wall along the groove, and a step of embedding a dielectric in the groove are newly required, so that the manufacturing cost is extremely high.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to solve the above problems and to provide a transmission line which can be formed without increasing the number of manufacturing steps, has less signal deterioration due to crosstalk, enables high-density wiring, and has good high-frequency transmission characteristics. Is to do.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is directed to a transmission line according to claim 1, wherein a signal line and a closed loop circuit with the signal line are formed or a return current path is formed. A plurality of wiring pairs provided with a pair of wirings having a larger wiring width than each other with a dielectric material interposed therebetween are arranged side by side so that a plurality of signal lines are not adjacent to each other or a pair of wirings is not adjacent to each other. And
[0007]
Further, in the transmission line according to claim 2, the signal line and a pair of wirings forming a closed loop circuit with the signal line or serving as a return current path and having a wiring width larger than the signal line are provided. A plurality of wiring pairs provided facing each other in the dielectric are arranged side by side such that a plurality of signal lines are not adjacent to each other or a pair of wirings is not adjacent to each other.
[0008]
Further, in the transmission line according to the third aspect, in the plurality of wiring pairs, a pair wiring between different wiring pairs is electrically connected by a via.
Embodiment of the present invention
The present invention will be described in detail based on the illustrated embodiment.
FIG. 1 shows a cross-sectional structure of a first embodiment of a transmission line according to the present invention, which forms a signal line 2a in a dielectric 1 and a closed loop circuit therewith, or serves as a return current path therefor. The pair wires 2b are formed to face each other to form a wire pair 2. The signal lines 3a and 4a and the pair wires 3b and 4b also form wire pairs 3 and 4 in the same manner. The wiring pairs 2, 3, 4 are alternately arranged so that the signal lines 2a, 3a, 4a do not adjoin each other or the pair wirings 2b, 3b, 4b do not adjoin each other. At this time, the wiring pitch Pt is the sum of the line width of the paired wiring and the inter-line space Sp. However, since the inter-line space Sp is a value in a different wiring layer, it can take a small value irrespective of the wiring manufacturing limit. That is, the wiring pitch Pt can be made smaller than in the conventional stacked pair line structure. FIG. 2 shows the crosstalk characteristics of the first embodiment, in which the signal line width is 50 μm, the pair wiring width is 90 μm, the space between the lines is 20 μm, and the distance between the signal line of the wiring pair and the pair wiring is: The dielectric constant of the dielectric is 3.4 μm, the wiring length is 10 mm, and the characteristic impedance is 50Ω. The S parameters for two ports of two adjacent wiring pairs are shown. In the figure, the horizontal axis represents the frequency, and the vertical axis represents the amplitude of the S parameter. (A) is S31 and (b) is S41. For comparison, the characteristics of a conventional stacked pair line structure with similar wiring specifications are also plotted in an overlapping manner. As is clear from the crosstalk characteristics, the first embodiment reduces the crosstalk by about 15 dB. From this result, it is understood that the present invention has much better crosstalk characteristics at the same wiring density.
[0010]
In the configuration of the present invention, since the inter-line space Sp is defined between different wiring layers, it is possible to set Sp = 0 as shown in FIG. Even in the case of Sp = 0, in the configuration having the signal line width of 50 μm and the pair wiring width of 90 μm, the adjacent signal line and the pair wiring in the same wiring layer are separated by 20 μm. The ease of manufacture is not different from the case where the space is 20 μm. In this case, the wiring pitch is 90 μm, and the wiring density can be improved. FIG. 4 shows the crosstalk characteristics of the second embodiment. The characteristics are almost the same as those of the first embodiment, and it can be seen that the crosstalk characteristics of this line structure are not affected by the wiring pitch Pt. From these results, it is understood that the present invention has both the crosstalk characteristics and the improvement in the wiring density. In the discussion on the crosstalk characteristics so far, it is assumed that the manufacturing position accuracy of wiring between different wiring layers is ± 20 μm. However, the present invention substantially exerts further effects. That is, in the present invention, when the manufacturing position accuracy of the wiring is poor, it is possible to set Sp <0.
[0011]
FIG. 5 shows a third embodiment, in which a signal line 6a and a pair wiring 6b which forms a closed loop circuit with the signal line 6a or a return current path thereof are formed in the dielectric 5 so as to face each other. The wiring pair 6 is formed. The signal lines 7a, 8a, 9a and the paired wirings 7b, 8b, 9b also form wiring pairs 7, 8, 9 in the same manner. In addition to the fact that the wiring pairs 6, 7, 8, 9 are alternately arranged so that the signal lines 6a, 7a, 8a, 9a are not adjacent to each other or the pair wirings 6b, 7b, 8b, 9b are not adjacent to each other. The pair wirings 6b, 7b, 8b, 9b are electrically connected by vias 10. The via pitch at which the pair wirings 6b, 7b, 8b, 9b are connected by the via 10 is changed according to the wavelength of an electric signal passing through the signal line. When the wavelength is long, the via pitch may be coarse, and when the wavelength is short, the via pitch needs to be fine. FIG. 6 shows the crosstalk characteristic of the third embodiment, in which the signal line width is 20 μm, the pair wiring width is 60 μm, the space between the lines is 20 μm, and the distance between the signal line of the wiring pair and the pair wiring is: The dielectric constant of the dielectric is 3.4 μm, the wiring length is 10 mm, and the characteristic impedance is 50Ω. In this configuration, as compared with the first and second embodiments, the wiring width of the signal line can be made smaller with the same characteristic impedance, so that the wiring density can be further improved. The crosstalk characteristic is superior to that of the first embodiment, and the effect of confining the electromagnetic field from the signal line due to via formation is clearly exhibited.
[0012]
In the above embodiment, the wiring pairs of the signal line and the pair wiring are all formed in the dielectric. However, if there is a dielectric only between the opposing signal line and the pair wiring, it functions as a transmission line. Therefore, the line need not necessarily be embedded in the dielectric.
[0013]
【The invention's effect】
As described above, in the transmission line according to the present invention, a plurality of wire pairs formed by signal lines and pair wires are arranged so that the signal lines or the pair wires are not adjacent to each other. Since it can be formed without increasing the number of steps, the wiring density can be increased as compared with the conventional stacked pair line structure, and the effect of reducing crosstalk is large. Further, by electrically connecting a plurality of pairs of wirings with vias, it is possible to further improve wiring density and reduce crosstalk.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a cross section of a first embodiment of a transmission line according to the present invention.
FIG. 2 is a graph showing crosstalk characteristics according to the first embodiment of the present invention.
FIG. 3 is an explanatory view showing a second embodiment of the present invention in cross section.
FIG. 4 is a graph showing crosstalk characteristics according to the second embodiment of the present invention.
FIG. 5 is an explanatory diagram showing a cross section of a third embodiment of the present invention. FIG. 6 is a graph showing a crosstalk characteristic of the third embodiment of the present invention.
FIG. 7 is an explanatory diagram showing an example of a conventional stripline transmission line in cross section.
FIG. 8 is an explanatory diagram showing an example of a conventional stacked pair line transmission line in cross section.
FIG. 9 is an explanatory diagram showing a cross section of another example of a conventional transmission line of a stacked pair line.
[Explanation of symbols]
1, 5,... Dielectrics 2, 3, 4, 6, 7, 8, 9,... Wiring pairs 2a, 3a, 4a, 6a, 7a, 8a, 9a. .., 4b, 6b, 7b, 8b, 9b... Pair wiring 10... Via Sp...

Claims (3)

A pair of signal lines and a pair of lines that form a closed loop circuit with the signal line or serve as a return current path and have a wider line width than the signal line is provided opposite to each other with a dielectric interposed therebetween. A transmission line, wherein a plurality of signal lines or a pair of wirings are arranged side by side so as not to be adjacent to each other. A signal line and a pair of wires forming a closed loop circuit with the signal line or a path of a return current and having a wire width wider than the signal line, and a wire pair provided facing in the dielectric, A transmission line, wherein a plurality of signal lines or a pair of wirings are arranged side by side so as not to be adjacent to each other. 3. The transmission line according to claim 1, wherein in the plurality of wiring pairs, pair wirings between different wiring pairs are electrically connected by vias. 4.

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