JP2009111461A - Differential signal transmission wiring board - Google Patents

Abstract

A differential signal transmission wiring board is provided which provides a large-sized board with a small change in characteristics of a different width BCS pair wiring including a GND plane at a low cost.
A differential signal transmission wiring board including a differential signal pair wiring composed of a first wiring and a second wiring arranged in a stacked manner, wherein one or more GND plane layers are provided. (20, 21, 22), and the differential signal pair wiring has the wiring width of the first wiring 11 wider than the wiring width 12 of the second wiring and when viewed from above in the stacking direction. The second wiring 12 is accommodated inside the first wiring 11.
[Selection] Figure 1

Description

  The present invention relates to a differential signal transmission wiring board including a differential signal pair wiring used for transmission of a high-speed operation signal.

  FIG. 5 is a cross-sectional view showing a stacking positional relationship when differential signal pair wirings are arranged vertically (stacking direction) in the conventional method. FIG. 5 shows a pair of differential signal pair wirings 11 and 12, a pair of differential signal pair wirings 11 and 12, and a differential signal pair wiring 11, and differential signal pair wirings 11 and 12, respectively. The substrate surface dielectrics 41 and 42 are formed.

  Here, FIG. 5A shows a case where no positional deviation occurs during the manufacture of the substrate, and there is no deviation in the width direction (left and right direction in FIG. 5) of the pair of differential signal pair wirings 11 and 12 configured as a pair. Is shown. On the other hand, FIG. 5B shows a case where a positional shift occurs during the manufacture of the substrate and there is a shift in the width direction of the differential signal pair wirings 11 and 12 configured as a pair. D in the figure indicates a shift amount corresponding to a relative stacking position shift width in the width direction of the differential signal pair wirings 11 and 12.

  Next, the effect when the stacking position shift occurs will be described. Usually, the differential signal pair wirings are generally arranged side by side (in the horizontal direction in FIG. 5). However, as shown in FIG. 5, by arranging the differential signal pair wirings 11 and 12 vertically (that is, in the stacking direction), the difference in the wiring length at the bending of the differential signal pair wirings 11 and 12 can be reduced. In addition, it is possible to make wiring with strong coupling within the pair. As a result, it is possible to obtain differential signal pair wirings 11 and 12 that are resistant to skew (phase shift) in the pair and external noise.

  Such a structure is referred to as a stacked pair wiring or a broad-side coupled pair (BSC) wiring. In the present specification, this structure is hereinafter referred to as “BSC pair”, and those having different pair wiring widths are particularly referred to as “different width BSC pairs”.

  In a multilayer wiring board, the position in the plane direction is shifted during lamination. For this reason, the position of the BSC pair is shifted, and the connectivity within the pair is weakened. As a result, the differential wiring characteristic may deviate from the target value, and a desired signal waveform may not be obtained.

  In order to avoid this, it is conceivable that the wiring widths of the pair of wirings constituting the BSC wiring are made different (for example, see Patent Document 1). FIG. 6 is a cross-sectional view showing the stacking positional relationship when the differential signal pair wirings are arranged in the vertical direction (stacking direction) with different wiring widths in the conventional method.

  Here, FIG. 6A shows a case where there is no displacement in the manufacturing process of the substrate, and there is no displacement in the width direction (the left-right direction in FIG. 6) of the pair of differential signal pair wirings 11 and 12 configured as a pair. Is shown. On the other hand, FIG. 6B shows a case where a positional deviation occurs during the manufacture of the substrate and there is a deviation in the width direction of the differential signal pair wirings 11 and 12 configured as a pair. D in the figure indicates a shift amount corresponding to a relative stacking position shift width in the width direction of the differential signal pair wirings 11 and 12.

  In FIG. 6, the differential impedance of this different width BSC pair wiring is optimized after setting the wiring width to a different value. Here, a case is considered where a positional deviation D (see FIGS. 5B and 6B) occurs in the lateral direction with respect to the wiring direction during the manufacture of the substrate. In this case, in the BSC pair wiring of FIG. 5B, the facing area between the wirings is reduced by the amount of deviation. As a result, the characteristic change of the pair wiring is large with respect to the assumption at the time of design.

  On the other hand, as shown in FIG. 6B, in the case of a BSC pair wiring whose wiring width is changed from the beginning, that is, a different width BSC pair wiring, even if a positional deviation occurs, the opposing area of the BSC pair wiring is reduced. The decrease is small. As a result, it is possible to suppress a change in characteristics from the design time.

  As described above, by changing the width of the BSC pair wiring, there is an effect of mitigating the change in differential impedance due to the positional deviation when the substrates are stacked. Further, by making the coordinates of the center lines of both the wide wiring and the narrow wiring coincide, a relaxation effect can be obtained regardless of the direction of deviation.

JP 2004-207949 A

However, the prior art has the following problems.
The multilayer substrate is generally a laminated structure including one or more GND plane layers. In this case, the characteristic impedance changes depending not only on the stacking deviation but also on the stacking order of the GND plane and the different width BSC pair wiring and the interlayer dielectric thickness. Furthermore, the manufacturing process of a substrate with a small positional deviation is generally high in cost, and it is difficult to manufacture a large substrate.

  The present invention has been made to solve the above-described problems, and provides a differential signal transmission wiring board which provides a large-sized board with a small characteristic change of a different width BCS pair wiring including a GND plane at a low cost. The purpose is to obtain.

  A differential signal transmission wiring board according to the present invention is a differential signal transmission wiring board provided with a differential signal pair wiring composed of a first wiring and a second wiring arranged in a stack, The differential signal pair wiring further includes at least one GND plane layer, and the differential signal pair wiring has a second wiring width wider than that of the second wiring and the second wiring when viewed from above in the stacking direction. This wiring fits inside the first wiring.

  According to the present invention, the wiring width of the first wiring is wider than the wiring width of the second wiring, and the second wiring fits inside the first wiring when viewed from above in the stacking direction. By designing the pattern of the differential signal pair wiring, and further maintaining the relationship between the stacking order with the GND plane layer and the interlayer dielectric thickness, the GND plane layer and the different width BSC pair wiring with little characteristic change due to stacking position shift It is possible to obtain a differential signal transmission wiring board that provides a large-sized board including a low cost.

Hereinafter, preferred embodiments of a differential signal transmission wiring board of the present invention will be described with reference to the drawings.
The differential signal transmission wiring board according to the present invention has a differential signal generated when a stacking position shift occurs by appropriately designing the wiring width and the dielectric thickness of the differential signal pair wiring according to the GND plane. The technical feature is that it is possible to suppress changes in impedance and characteristic impedance, thereby realizing an increase in substrate size and cost. Such differential signal pair wiring can also be applied to a package substrate for mounting a semiconductor integrated circuit or various electronic devices.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view showing the positional relationship between the differential signal transmission wiring boards according to the first embodiment of the present invention. The cross-sectional view shown in FIG. 1 shows a pair of differential signal pair wirings 11 and 12, a GND plane 20, a dielectric 30 between the differential signal pair wirings 11 and 12, and a differential signal pair wiring 11 The substrate surface dielectric 40 is provided on the wiring, and the dielectric 50 is provided between the differential signal pair wiring 12 and the GND plane 20.

  Here, FIG. 1A shows a case where no positional deviation occurs during the manufacture of the substrate, and there is no deviation in the width direction (left-right direction in FIG. 1) of the differential signal pair wirings 11 and 12 configured as a pair. Is shown. On the other hand, FIG. 1B shows a case where a positional shift occurs during the manufacture of the substrate, and there is a shift in the width direction of the differential signal pair wirings 11 and 12 configured as a pair. D in the figure indicates a shift amount corresponding to a relative stacking position shift width in the width direction of the differential signal pair wirings 11 and 12.

  Next, the effect when the stacking position shift occurs will be described. As shown in FIG. 1A, the differential signal pair wirings 11 and 12 are designed with different wiring widths to optimize the differential impedance of the different width BSC pair wirings. Further, by making the width of the wiring 11 in the layer close to the substrate surface (that is, far from the GND plane 20) wider than the width of the other wiring 12, the characteristic impedance of each of the differential signal pair wirings 11 and 12 is increased. Can be designed in the same way.

  Consider a case where a positional deviation D occurs in the lateral direction with respect to the wiring direction during the manufacture of the substrate. In this case, in the BSC pair wiring of FIG. 5B configured with the same wiring width, the facing area between the wirings is reduced by the amount of deviation. As a result, the characteristic change of the pair wiring is large with respect to the assumption at the time of design.

  On the other hand, as shown in FIG. 1B, in the case of a BSC pair wiring in which the width of the wiring 11 in the layer far from the GND plane 20 is widened, that is, in a different width BSC pair wiring, However, the decrease in the facing area of the BSC pair wiring is small. As a result, it is possible to suppress a change in differential impedance from the time of design.

  Furthermore, the change in the area of the respective wirings facing the GND can be reduced with respect to the stacking deviation. As a result, it is possible to suppress a change in characteristic impedance from the time of design.

  As described above, according to the first embodiment, by changing the width of the BSC pair wiring, there is an effect of mitigating a change in differential impedance due to a positional shift at the time of stacking the substrates. Furthermore, by making the coordinates of the center lines of both the wide wiring and the narrow wiring coincide, a relaxation effect can be obtained regardless of the direction of deviation.

  Furthermore, since it is not necessary to use an expensive substrate manufacturing process in order to suppress misalignment, a BSC pair wiring having desired differential characteristics can be manufactured with a low cost substrate. Further, since the positional deviation accuracy may be loose, a large size substrate can be manufactured at low cost.

  In the first embodiment, the case where three layers close to the substrate surface are used is shown, but this need not be the three layers closest to the surface. That is, in the range shown in FIG. 1, all the conductors of unused layers may be removed when the substrate is manufactured, and the remaining three layers may be used. In addition, each of the dielectrics 30 and 40 has a single layer structure, but each may be a laminate of a plurality of dielectrics.

Embodiment 2. FIG.
In the second embodiment, the line width design in a different width BSC pair having one GND plane will be specifically described. FIG. 2 is a cross-sectional view showing the positional relationship between the differential signal transmission wiring boards according to the second embodiment of the present invention. The basic configuration is the same as that in FIG. 1 in the first embodiment, and the width of the wiring 11 is shown as W1 and the width of the wiring 12 is shown as W2. However, in FIG. 2B, the end of the narrow wiring 12 does not protrude from the end of the wide wiring 11 when viewed from above the substrate.

In this case, the line width design for suppressing the characteristic change when the stacking position shift occurs will be described next. The maximum value (tolerance) of misalignment during stacking is defined as Dmax (≧ D). Here, the difference between the wiring width W1 of the wiring 11 and the wiring width W2 of the wiring 12 is designed to satisfy the following expression (1).
W1-W2 ≧ 2 × Dmax (1)

  As a result, even if the stacking misalignment in the lateral direction of the wiring reaches the maximum Dmax, the end of the narrow wiring 12 never goes outside the end of the wide wiring 11 (see FIG. 2B). That is, the wiring 12 is accommodated in the wiring 11 when viewed from the upper part in the stacking direction. As a result, if the positional deviation at the time of stacking is within Dmax, the opposing areas of the two wirings 11 and 12 can always be kept constant, and variations in differential impedance and characteristic impedance during design can be reduced.

From the above equation (1), the relationship of the following equation (2) can be obtained.
(W1-W2) -2 × Dmax ≧ 0 (2)

  Here, the larger the value on the left side of the above equation (2), the smaller the characteristic variation due to the positional deviation.

  As described above, according to the second embodiment, by designing the difference between the two wiring widths of the different width BSC pair to be twice or more the maximum positional deviation amount expected at the time of stacking ( That is, by satisfying the relationship of the above expression (1), it is possible to reduce the change in the differential impedance and the characteristic impedance due to the positional deviation at the time of stacking.

  Furthermore, by designing the left side of the above formula (2) to be as large as possible, it is possible to further suppress the change in wiring characteristics.

  As a result, since it is not necessary to use an expensive substrate manufacturing process in order to suppress stacking deviation, a BSC pair wiring having a desired differential characteristic can be manufactured with a low-cost substrate. Furthermore, since the positional deviation accuracy may be loose, a large size substrate can be manufactured at low cost.

Embodiment 3 FIG.
FIG. 3 is a cross-sectional view showing the positional relationship between the differential signal transmission wiring boards according to the third embodiment of the present invention. The cross-sectional view shown in FIG. 3 shows a pair of differential signal pair wires 11 and 12, a pair of GND planes 21 and 22, a dielectric 30 between the differential signal pair wires 11 and 12, and a differential signal. The dielectric 51 is provided between the pair wiring 11 for use and the GND plane 21, and the dielectric 52 is provided between the pair wiring 12 for differential signal and the GND plane 22.

  Here, FIG. 3A shows a case where no positional deviation occurs during the manufacture of the substrate, and there is no deviation in the width direction (left and right direction in FIG. 3) of the pair of differential signal pair wirings 11 and 12 configured as a pair. Is shown. On the other hand, FIG. 3B shows a case where a positional shift occurs during the manufacture of the substrate, and there is a shift in the width direction of the differential signal pair wirings 11 and 12 configured as a pair. D in the figure indicates a shift amount corresponding to a relative stacking position shift width in the width direction of the differential signal pair wirings 11 and 12.

  Compared with the laminated structure of the differential signal transmission wiring board of FIG. 1 in the first embodiment, the laminated structure of the differential signal transmission wiring board of FIG. 3 in the third embodiment has a pair of GND planes. It is different in the configuration.

  The differential signal pair wirings 11 and 12 are different width BSC pair wirings having different wiring widths, and the differential impedance is optimized.

  Further, the thickness of the dielectric 51 between the wide wiring 11 and the adjacent GND plane 21 (vertical direction in FIG. 3B) is set to the dielectric between the narrow wiring 12 and the adjacent GND plane 22. By making it thicker than the thickness of the body 52, the characteristic impedances of the differential signal pair wirings 11 and 12 can also be designed to be the same. Specifically, by making the thickness of the dielectric 51 thicker than the thickness of the dielectric 52 according to the wiring width of the wide wiring 11 and the narrow wiring 12, the differential signal pair wiring 11, Each of the 12 characteristic impedances can be designed in the same way.

  Consider a case where a positional deviation D occurs in the lateral direction with respect to the wiring direction during the manufacture of the substrate. In this case, in the BSC pair wiring of FIG. 5B configured with the same wiring width, the facing area between the wirings is reduced by the amount of deviation. As a result, the characteristic change of the pair wiring is large with respect to the assumption at the time of design.

  On the other hand, as shown in FIG. 3B, in a substrate having a pair of GND planes 21 and 22, if a different width BSC pair is used from the beginning, even if misalignment occurs, the opposing area of the pair wirings The decrease in is small. As a result, it is possible to suppress a change in differential impedance from the time of design.

  Furthermore, the change in the area of the respective wirings facing the GND can be reduced with respect to the stacking deviation. As a result, it is possible to suppress a change in characteristic impedance from the time of design.

  As described above, according to the third embodiment, even in a substrate having a pair of GND patterns, there is an effect of relieving a change in differential impedance due to a positional shift when the substrates are stacked by changing the width of the BSC pair wiring. . Furthermore, by making the coordinates of the center lines of both the wide wiring and the narrow wiring coincide, a relaxation effect can be obtained regardless of the direction of deviation.

  Furthermore, since it is not necessary to use an expensive substrate manufacturing process in order to suppress misalignment, a BSC pair wiring having desired differential characteristics can be manufactured with a low cost substrate. Further, since the positional deviation accuracy may be loose, a large size substrate can be manufactured at low cost.

  In the third embodiment, the case where four consecutive layers are used is shown. However, all the conductors of unused layers between the pair of GND plane layers are removed during the manufacture of the substrate, and the remaining layers are different. A width BCS pair wiring may be configured. In addition, each of the dielectrics 30 and 40 has a single layer structure, but each may be a laminate of a plurality of dielectrics.

Embodiment 4 FIG.
In the fourth embodiment, the design of the line width in a different width BSC pair having two GND planes will be specifically described. FIG. 4 is a cross-sectional view showing the positional relationship between the differential signal transmission wiring boards according to the fourth embodiment of the present invention. The basic configuration is the same as in FIG. 3 in the third embodiment, and the width of the wiring 11 is shown as W1 and the width of the wiring 12 is shown as W2. However, in FIG. 4B, the end of the narrow wiring 12 does not protrude from the end of the wide wiring 11 when viewed from above the substrate.

In this case, the line width design for suppressing the characteristic change when the stacking position shift occurs will be described next. The maximum value (tolerance) of misalignment during stacking is defined as Dmax (≧ D). Here, the difference between the wiring width W1 of the wiring 11 and the wiring width W2 of the wiring 12 is designed so as to satisfy the same expression (1) as that shown in the second embodiment.
W1-W2 ≧ 2 × Dmax (1)

  As a result, even if the stacking misalignment in the lateral direction of the wiring reaches the maximum Dmax, the end of the narrow wiring 12 never goes outside the end of the wide wiring 11 (see FIG. 4B). That is, the wiring 12 is accommodated in the wiring 11 when viewed from the upper part in the stacking direction. As a result, if the positional deviation at the time of stacking is within Dmax, the opposing areas of the two wirings 11 and 12 can always be kept constant, and variations in differential impedance and characteristic impedance during design can be reduced.

From the above equation (1), the same relationship of the following equation (2) as that shown in the second embodiment can be obtained.
(W1-W2) -2 × Dmax ≧ 0 (2)

  Here, the larger the value on the left side of the above equation (2), the smaller the characteristic variation due to the positional deviation.

  As described above, according to the fourth embodiment, by designing the difference between the two wiring widths of the different width BSC pair to be twice or more the maximum positional deviation amount expected at the time of stacking ( That is, by satisfying the relationship of the above expression (1), it is possible to reduce the change in the differential impedance and the characteristic impedance due to the positional deviation at the time of stacking.

  Furthermore, by designing the left side of the above equation (2) to be as large as possible, the change in the wiring characteristics can be further reduced.

  As a result, since it is not necessary to use an expensive substrate manufacturing process to suppress the stacking deviation, a BSC pair wiring having a desired differential characteristic can be manufactured with a low cost substrate. Furthermore, since the positional deviation accuracy may be loose, a large size substrate can be manufactured at low cost.

It is sectional drawing which showed the lamination | stacking positional relationship of the wiring board for differential signal transmission in Embodiment 1 of this invention. It is sectional drawing which showed the lamination | stacking positional relationship of the wiring board for differential signal transmission in Embodiment 2 of this invention. It is sectional drawing which showed the lamination | stacking positional relationship of the wiring board for differential signal transmission in Embodiment 3 of this invention. It is sectional drawing which showed the lamination | stacking positional relationship of the wiring board for differential signal transmission in Embodiment 4 of this invention. It is sectional drawing which showed the lamination | stacking positional relationship at the time of arranging the differential signal pair wiring vertically in the conventional system. It is sectional drawing which showed the lamination | stacking positional relationship at the time of arranging each wiring width of the differential signal pair wiring differently in the conventional system.

Explanation of symbols

  11 differential signal pair wiring (first wiring), 12 differential signal pair wiring (second wiring), 20 GND plane, 21 GND plane (first GND plane), 22 GND plane (second wiring) GND plane), 30 dielectric, 40, 41, 42 Substrate surface dielectric, 50 dielectric, 51 dielectric (first dielectric), 52 dielectric (second dielectric).

Claims (4)

A differential signal transmission wiring board including a differential signal pair wiring composed of a first wiring and a second wiring arranged in a stack,
Further comprising a GND plane,
In the differential signal pair wiring, the wiring width of the first wiring is wider than the wiring width of the second wiring, and the second wiring is the first wiring when viewed from above in the stacking direction. Fits inside the wiring,
The second wiring is between the first wiring and the GND plane;
A differential signal transmission wiring board, wherein no other conductor plane is sandwiched between the first wiring and the substrate surface. The differential signal transmission wiring board according to claim 1,
The differential signal pair wiring is designed such that the wiring width of the first wiring is wider than the wiring width of the second wiring by at least twice as much as the maximum amount of misalignment at the time of substrate manufacture. A differential signal transmission wiring board. A differential signal transmission wiring board including a differential signal pair wiring composed of a first wiring and a second wiring arranged in a stack,
Further comprising a first GND plane and a second GND plane;
In the differential signal pair wiring, the wiring width of the first wiring is wider than the wiring width of the second wiring, and the second wiring is the first wiring when viewed from above in the stacking direction. Fits inside the wiring,
The first GND plane, the first wiring, the second wiring, and the second GND plane are stacked in this order.
The differential signal transmission wiring board, wherein a thickness between the first GND plane and the first wiring is thicker than a thickness between the second wiring and the second GND plane. . The differential signal transmission wiring board according to claim 3,
The differential signal pair wiring is designed such that the wiring width of the first wiring is wider than the wiring width of the second wiring by at least twice as much as the maximum amount of misalignment at the time of substrate manufacture. A differential signal transmission wiring board.

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