JP2019096979A - Impedance converter - Google Patents

Abstract

To provide an impedance converter in which improvement of refinement of pad interval and wiring density is compatible with reduction of crosstalk noise between wires.SOLUTION: An impedance converter includes dielectric boards (10, 20), first conductor layers (11, 21) formed on one side of the board and second conductor layers (12, 22) formed on the other side of the board, and multiple strip lines (13, 23) consisting of conductors formed in the board separately from the first and second conductor layers. In at least one of the multiple lines, the distances (h1, h3) to at least any one of the first and second conductor layers are different from each other on the one end side and the other end side, and distance to any one of the first and second conductor layers changes gradually from the one end side across the other end side.SELECTED DRAWING: Figure 1A

Description

  The present invention relates to an impedance converter, and more particularly to an impedance converter composed of a transmission line having a strip line structure used in a semiconductor high frequency module.

  A strip line is used as a transmission line used for a high frequency circuit. A strip line is a kind of transmission line for transmitting an electromagnetic wave, and a conductor formed on the front and back of a plate-like dielectric substrate and a linear strip conductor formed on the inside of the dielectric substrate ( Hereinafter, it may only be called a "line." Conductors respectively formed on the front and back surfaces of the dielectric substrate are at GND (hereinafter, the conductors respectively formed on the front and back surfaces of the dielectric substrate may be referred to as “ground layers”).

  The characteristic impedance of such a strip line is determined by the line width and thickness, the dielectric constant of the dielectric substrate, and the distance between the line and the ground layer.

  When connecting a load circuit or signal source having a certain impedance, for example, to a high frequency circuit, match the characteristic impedances of the high frequency circuit with the load circuit or signal source in order to efficiently transmit power and signals at these connection parts. You need to In order to perform this impedance matching, an impedance converter formed to have different characteristic impedances at both ends of the strip line is used.

  Conventionally, in an impedance converter using a transmission line, in order to prevent deterioration of transmission characteristics in a high frequency band due to a rapid impedance change, as shown in FIGS. 18 and 19A, 19B, the back surface and the front surface of dielectric substrate 30. In the stripline 3 consisting of the ground layers 31 and 32 formed respectively and the line (strip conductor) 33 formed inside the dielectric substrate 30, the line 33 is formed in a tapered shape in plan view, By gradually changing the line width, the impedance is converted to a desired impedance (Non-Patent Document 1).

JP 2013-251863

P. Pramanick, et al., "Tapered Microstrip Transmission Lines," IEEE MTT-S Int. Microw. Symp. Dig., Vol. 1983, pp. 242-244. 1983.

  On the other hand, in recent years, the increase in the number of signals of semiconductor high frequency modules and the miniaturization of substrate connection pads have been advanced. That is, the signals input to and output from the semiconductor high frequency module are increased to improve the functionality of the semiconductor high frequency module, and the external size needs to be reduced for the high performance and cost reduction of the semiconductor high frequency module. In order to achieve this, the miniaturization of substrate connection pads and pad spacing is in progress.

  As a result, in a wiring board connected to a semiconductor high frequency module, realization of a transmission line capable of drawing a large number of signals at high density and an impedance converter performing impedance conversion while maintaining high frequency characteristics by the transmission line are required.

  In the case of performing impedance conversion by a strip line while maintaining high frequency characteristics, in the prior art, as shown in FIGS. 20 and 21, a plurality of tapered lines 33-1, 33-2, 33-3 are provided, The line widths of the lines 33-1, 33-2, and 33-3 are gradually changed.

However, in this case, as the line widths of the lines 33 (33-1, 33-2, 33-3) increase, the pads 35 (35-1, 35-2, 35-3), When the distance between (37-1, 37-2, 37-3) increases (FIG. 20) or when the distance between the lines 33 (33-1, 33-2, 33-3) decreases, There is a problem that crosstalk noise between wires increases (FIG. 21). In particular, crosstalk noise between wires is generated by displacing electrons of the other signal line when a signal pulse is transmitted by one of the signal lines adjacent to each other. For this reason, as the distance between the plurality of lines 33 (33-1, 33-2, 33-3) decreases, the number of electrons generated in the other lines 33 when the signal pulse is transmitted by one line 33. The displacement amount also increases, and the crosstalk noise also increases.
Therefore, it may be difficult to apply an impedance converter using a strip line to high density mounting.

  Therefore, the present invention provides an impedance converter in a semiconductor high frequency module applicable to so-called high density mounting, which achieves both miniaturization of pad spacing and improvement of wiring density and reduction of crosstalk noise between wirings. The purpose is

In order to achieve the above object, an impedance converter according to the present invention comprises: a substrate (10, 20) made of a dielectric;
A first conductor layer (11, 21) formed on one surface of the substrate, a second conductor layer (12, 22) formed on the other surface of the substrate, and the first conductor inside the substrate A plurality of strip-like lines (13, 23) made of a conductor and separated from the layer and the second conductor layer, at least one of the plurality of lines having one end and the other end The distance (h1, h3) to at least one of the first conductor layer and the second conductor layer is different from each other, and any one of the first conductor layer and the second conductor layer is different from the one end side to the other end side It is characterized in that the distance of is gradually changing.

  In the impedance converter according to the present invention, the plurality of lines (13) are directed from the one end side to the other end side toward any one of the first conductor layer (11) and the second conductor layer (12). It may be approaching gradually.

  In the above impedance converter, the plurality of lines (13) may be gradually approached to the first conductor layer (11) and the second conductor layer (12) alternately.

  In the impedance converter according to the present invention, the plurality of lines (23) and the first conductor layer (21) formed on one surface of the substrate (20) and the other surface of the substrate The second conductor layer (22) is characterized by gradually approaching the plurality of lines from the one end side to the other end side of the plurality of lines.

  In the impedance converter according to the present invention, a plurality of pads (15, 17) formed on one surface of the substrate and electrically isolated from the first conductor layer and the second conductor layer, A plurality of vias (14, 16) may be provided to electrically connect the ends of the plurality of lines and the plurality of pads, respectively.

  In the impedance converter according to the present invention, the substrate (10, 20) may be made of a dielectric containing benzocyclobutene.

  According to the present invention, the distance between the strip-like line (13, 23) and the conductor layer (11, 12, 21, 22) is gradually changed from one end side to the other end side of the line to both ends of the strip line. Since the characteristic impedances of the two circuits are made different, the characteristic impedances can be converted continuously while maintaining the width of the lines and the gaps between the lines. Therefore, it is possible to provide an impedance converter applicable to so-called high density mounting, which achieves both miniaturization of pad spacing and improvement of wiring density and reduction of crosstalk noise between wirings.

FIG. 1A is a side view illustrating the configuration of the impedance converter according to the first embodiment of the present invention. FIG. 1B is a plan view illustrating the configuration of the impedance converter according to the first embodiment. FIG. 2A is a view showing a cross section a-a ′ of the impedance converter shown in FIG. 1B. FIG. 2B is a view showing a cross section along b-b 'of the impedance converter shown in FIG. 1B. FIG. 2C is a view showing a cross section at c-c 'of the impedance converter shown in FIG. 1B. FIG. 3 is a diagram for explaining the conditions of the simulation. FIG. 4 is a diagram showing simulation results of characteristic impedance on the output side of the impedance converter according to the first embodiment and the impedance converter using the conventional tapered line. FIG. 5 is a diagram showing the relationship between the characteristic impedance of the impedance converter according to the first embodiment and the distance between the line and the ground layer closest to the line. FIG. 6A is a diagram showing an electromagnetic field simulator model of a strip line of a conventional configuration. FIG. 6B is a diagram showing a model of a strip line by the electromagnetic field simulator of the conventional configuration. FIG. 7A is a view showing a model of the strip line according to the present embodiment by the electromagnetic field simulator. FIG. 7B is a view showing a model of the strip line according to the present embodiment by the electromagnetic field simulator. FIG. 8 is a diagram showing simulation results on backward crosstalk using a model. FIG. 9 is a diagram showing simulation results on forward crosstalk using a model. FIG. 10A is a side view illustrating the configuration of the impedance converter according to the second embodiment of the present invention. FIG. 10B is a plan view illustrating the configuration of the impedance converter according to the second embodiment. 11A is a view showing a cross section a-a 'of the impedance converter shown in FIG. 10B. FIG. 11B is a diagram showing a cross section along b-b ′ of the impedance converter shown in FIG. 10B. 11C is a view showing a cross section taken along c-c 'of the impedance converter shown in FIG. 10B. FIG. 12 is a diagram for explaining the conditions of the simulation. FIG. 13 is a diagram showing simulation results of the characteristic impedance on the output side of the impedance converter according to the second embodiment and the impedance converter using the conventional tapered line. FIG. 14 is a diagram showing the relationship between the characteristic impedance of the impedance converter according to the second embodiment and the distance between the line and the ground layer. It is a figure which shows the model by the electromagnetic field simulator of the strip line which concerns on this Embodiment. FIG. 15B is a view showing a model of the strip line according to the present embodiment by the electromagnetic field simulator. FIG. 16 is a diagram showing simulation results on backward crosstalk using a model. FIG. 17 is a diagram showing simulation results on forward crosstalk using a model. FIG. 18 is a conceptual diagram for explaining the configuration of a conventional impedance converter using a tapered line. FIG. 19A is a conceptual diagram illustrating the configuration of a conventional impedance converter using a tapered line. FIG. 19B is a conceptual diagram illustrating the configuration of a conventional impedance converter using a tapered line. FIG. 20 is a conceptual diagram for explaining the configuration of a conventional impedance converter using a tapered line. FIG. 21 is a conceptual diagram for explaining the configuration of a conventional impedance converter using a tapered line.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First Embodiment
The configuration of the impedance converter 1 according to the first embodiment of the present invention is shown in FIGS. 1A to 2C. Here, FIGS. 1A and 1B are a side view and a plan view for explaining the configuration of the impedance converter 1, respectively, and FIGS. 2A to 2C are aa 'line, bb' line and c shown in FIG. 1B, respectively. It is sectional drawing of a surface perpendicular | vertical to the board | substrate 10 in the position of-c 'line. Here, FIG. 1B shows a state in which the conductor layer 12 is removed for the sake of clarity.

  As shown in these figures, the impedance converter 1 according to the first embodiment includes a substrate 10 made of a dielectric, a first conductor layer 11 formed on the lower surface of the substrate 10, and the upper surface of the substrate 10. The formed second conductor layer 12 (hereinafter, the first conductor layer 11 and the second conductor layer 12 may be collectively referred to as “ground layers 11 and 12”) and the two ground layers 11 in the substrate 10 , 12 and has a strip line structure provided with three conductor lines 13 (13-1, 13-2, 13-3) formed in the form of a strip, respectively. The substrate 10 is made of a dielectric such as benzocyclobutene.

  Further, a plurality of pads 15 (15-1, 15-2, 15-3), 17 (17-1, 17-2, 17-3)) are formed on the upper surface of the substrate 10. These pads 15, 17 are electrically isolated from the ground layer 12, while the vias 14 (14-1, 14-2, 14-3), 16 (16-1, 16) provided in the substrate 10. It is electrically connected with the end of the line 13 (13-1, 13-2, 13-3) through the points -2, 16-3).

  In the impedance converter 1 according to the present embodiment, the line widths of the lines 13-1, 13-2, and 13-3 are constant at W, but are formed on the lower surface of the substrate 10 from one end side to the other end side. It gradually approaches one of the ground layer 11 and the ground layer 12 formed on the upper surface.

  The lines 13-1 and 13-3 are formed on the upper surface of the substrate 10 from the input side to the output side, for example, if the left side is the input side and the right side is the output side in FIG. 1A and FIG. While the distance from the ground layers 11 and 12 at the input side is h1 (see FIG. 2A), while the distance from the ground layer 12 at the output side is h3. (<H3) (see FIG. 2C). The line 13-2 gradually approaches the ground layer 11 formed on the lower surface of the substrate 10 from the input side to the output side, and the distance from the ground layers 11 and 12 at the input side is the other Similar to the lines 13-1 and 13-3, the distance is h1 (see FIG. 2A), while the distance from the ground layer 11 on the output side is h3 (see FIG. 2C).

  Here, in order to consider the characteristic impedance of the impedance converter 1 according to the present embodiment, a parallel plate capacitor is considered. In a parallel plate capacitor in which the distance between the plates is extremely small compared to the length of one side of the plates, the electric field (electric field) between the plates can be regarded as uniform. The parallel capacitance C of the strip line at this time is proportional to the area S of the plates, inversely proportional to the distance d between the plates, and is expressed by the following equation (where ε is the dielectric constant).

  From Equation 1, it is understood that the parallel capacitance (C) increases as the distance (d) between the line and the ground layer decreases.

  Further, the characteristic impedance (Z0) of the line is expressed by the following equation 2. However, in Equation 2, R, L, G and C are respectively series resistance (Ω), series inductance (H), parallel conductance (S) and parallel capacitance (F) per unit length of the line. .

  According to Equations 1 and 2, since the characteristic impedance decreases as the distance between the line and the ground decreases, it has a configuration that approaches any of the line 13, the ground layer 11, and the ground layer 12 from the input side to the output side as described above. The strip line is an impedance converter in which the characteristic impedance is large at the input side and the characteristic impedance is small at the output side.

  The impedance converter according to the present embodiment can be manufactured by the following process.

  First, a dielectric such as benzocyclobutene or polyimide is deposited on a substrate to form a dielectric layer. The thickness (height) is the distance h3 (see FIG. 2C) between the line 13 and the lower ground layer 11. Next, a pattern made of a conductor such as Au is formed to a predetermined thickness on the dielectric layer, and a dielectric layer is deposited around the conductor pattern so as to have the same height as the conductor pattern. This conductor pattern is a part of the line 13.

  Subsequently, on the conductor pattern and the dielectric layer, a new conductor pattern in contact with the previously formed conductor pattern is shifted in the line extending direction from the previously formed conductor pattern in plan view. And deposit a dielectric layer to the same height as the conductor pattern. At this time, a conductor pattern to be a via may be formed together with a conductor pattern to be a line. Thus, the formation of the conductor pattern and the dielectric layer is repeated to obtain a dielectric laminate including a line of a desired shape made of the conductor pattern. Once such a dielectric stack is obtained, the deposit is separated from the substrate to form ground layers and pads on both sides. Thus, the impedance converter according to the present embodiment can be obtained.

  Next, a simulation regarding the relationship between the distance between the line 13 and the ground layers 11 and 12 and the impedance will be described. In this simulation, it is assumed that Au metal is used for the ground layer 11, the ground layer 12, and the line 13, and a benzocyclobutene (BCB) substrate (εr = 2.7) is used for the substrate 10, and the line length is 300 μm. The characteristic impedance on the output side of the impedance converter according to the present embodiment was compared with the characteristic impedance on the output side of the impedance converter using the conventional tapered line.

However, for both impedance converters, the line width on the input side was fixed at 4 μm and the inter-line gap (G) was fixed at 4 μm. Therefore, while the line width of the impedance converter according to the present embodiment is fixed at 4 μm on both the input side and the output side, the impedance converter using the conventional tapered line has the line width W of the output side. As a parameter, it was changed from 4 μm to 8 μm.
In this simulation, as shown in FIG. 3, the distance h between the line of the impedance converter according to the present embodiment and the ground layer closer to this line is used as a parameter. In the conventional impedance converter using a tapered line, the distance between the line and the ground layer is fixed at 7 μm both above and below.

  FIG. 4 shows the line width (W) and the characteristic impedance (A) on the output side of the impedance converter according to the present embodiment, calculated under the above conditions, and the output of the impedance converter using the conventional tapered line. It is a graph which shows the relationship with the characteristic impedance (B) of the side. In FIG. 4, the line width (W) and the substantial inter-line distance W + G are used on the vertical axis as an index of the effect.

  In FIG. 4, the line indicated by “A” represents the change in the characteristic impedance on the output side of the impedance converter according to the present embodiment. From this, it can be seen that, in the case of the impedance converter according to the present embodiment, the characteristic impedance on the output side can be changed without changing the line width or the distance between the lines. In the impedance converter according to the present embodiment, the distance h between the line 13 and the ground layers 11 and 12 closer to the line 13 is h = 7 μm when the value of the characteristic impedance is 60 Ω. When the characteristic impedance value is 35 Ω, h = 1 μm.

  On the other hand, the line indicated by “B” in FIG. 4 represents the change in the characteristic impedance on the output side of the impedance converter using the conventional tapered line. As the line width is increased from 4 μm to 12 μm (in terms of the distance between the lines, W + G is increased from 8 μm to 16 μm), the characteristic impedance on the output side decreases from 60 Ω to 37 Ω.

  FIG. 5 shows the relationship between the characteristic impedance of the impedance converter according to the present embodiment and the distance h between the line 13 and the ground layer 11 or 12 closer to the line 13. It can be seen from FIG. 5 that when the value of the distance h changes from 7 to 1, the characteristic impedance on the output side changes from 61Ω to 35Ω. Here, the reason that the characteristic impedance is not linearly proportional to the value of the distance h is that the characteristic impedance of the line is greater than the influence of the distance h between the line and the ground layer between the adjacent line. It is considered that the influence of the distance (line interval) k is larger (in this example, when the distance h = 4 to 6 μm). If the line spacing k is always set larger than the distance h to the ground layer, the characteristic impedance value is proportional to the value of h.

  Next, the amount of crosstalk is compared between the conventional impedance converter using a tapered line and the impedance converter according to the present embodiment. FIGS. 6A to 7B are models of striplines by the electromagnetic field simulator Sonnet-EM. FIGS. 6A and 6B are models of a conventional impedance converter, and FIGS. 7A and 7B are models of an impedance converter according to the present embodiment.

In this simulation, in order to compare the amount of crosstalk, the inter-line gap G was fixed at 4 μm, the line thickness was also fixed at 2 μm, and the characteristic impedance was made equal to 50 Ω.
FIGS. 6A and 6B show examples of conventional impedance converter models using tapered lines, where the line width W = 6.5 μm and the line-ground distance h = 7 μm.
7A and 7B show examples of the model of the impedance converter according to the present embodiment, where the line width W = 4 μm and the line-ground interlayer distance h = 2.2 μm.
In the simulation, the number of lines in the output side of the impedance converter is two in order to simplify the calculation.

By setting Port numbers as shown in FIG. 6B and FIG. 7B for the input and output ends of the line and examining the results of the S parameters, it is possible to directly evaluate the crosstalk amount.
8 and 9 represent backward (near end) crosstalk and forward (far end) crosstalk, respectively. More specifically, FIG. 8 shows a ratio (S31) to a voltage appearing at Port 3 when a signal is given to Port 1, and FIG. 9 shows a voltage ratio (S41) between Port 1 and Port 4. Both are displayed in decibels in order to clarify the difference. In FIGS. 8 and 9, the line indicated by “A” represents the crosstalk of the conventional impedance converter, and the line indicated by “B” represents the crosstalk of the impedance converter according to the present embodiment.

  It is understood from FIG. 8 that backward crosstalk (“B”) by the impedance converter according to the present embodiment is smaller by about 10 dB in a wide range of 0 GHz to 100 GHz than that of the conventional one (“A”). Further, FIG. 9 also shows that the impedance converter (“B”) according to the present embodiment is smaller by about 0 to 10 dB in a wide range of 25 GHz to 100 GHz as to forward crosstalk.

  As described above, according to the impedance converter according to the present embodiment, the distance between the line 13 and the ground layers 11 and 12 is gradually changed from the input side to the output side, whereby the high frequency due to the rapid change in impedance Characteristic impedance Zi at the input side of the strip line and the characteristic impedance at the output side by making the distance between the line 13 and the ground layers 11 and 12 different between the input side and the output side while preventing deterioration of the transmission characteristics in the band. It is possible to configure an impedance converter different from Z0.

  Therefore, even if the line width of the line 13 and the gap G between the lines are not changed, the distance between the line 13 and the ground layer 11 or the ground layer 12 can be reduced by bringing the line 13 closer to the upper and lower ground layers 11 and 12 By adjusting, it is possible to form an impedance converter in which a desired characteristic impedance value can be set and the characteristic impedances on the input side and the output side of the line are different.

  Further, since it is not necessary to make the line 13 tapered to change the line width, the pads 15 (15-1, 15-2, 15-3) accompanying the increase of the line width of the line as in the prior art, It is possible to avoid an increase in the distance between the two 17 (17-1, 17-2, 17-3) and an increase in crosstalk noise between the lines.

Moreover, in the present embodiment, among the three lines 13, the output side of the lines 13-1 and 13-3 at both ends is closer to the upper surface side than the lower surface of the substrate 10, and the central line 13-2. The output side is closer to the lower surface side than the upper surface of the substrate 10. That is, the three lines 13 alternately approach each other to either the first ground layer 11 or the second conductor layer 12 and move toward the upper or lower surface of the substrate 10 from the input side to the output side. Are alternated.
As a result, as shown in FIGS. 2A to 2C, the distance between the lines (k1 <k2 <k3) increases from the input side to the output side even with the inter-line gap G kept constant. It becomes easy to hold the talk.

  Further, since the lines are alternately brought close to the ground layer, the effect of reducing crosstalk can also be obtained. Furthermore, the line spacing also increases, and a further crosstalk reduction effect can be obtained simultaneously. Therefore, according to the impedance converter according to the present embodiment, the impedance converter applicable to high density mounting, which achieves both the miniaturization of the pad interval, the improvement of the wiring density and the reduction of the crosstalk noise between the wirings It can be formed.

Although the characteristic impedance on the output side of the impedance converter is reduced in the present embodiment, it is also possible to form an impedance converter in which the characteristic impedance on the input side is reduced.
In the above embodiment, although the case of three split conductors (transmission lines) has been described as an example, the present invention is not limited to this, and two or four or more multi-lanes may be used. It goes without saying that it is also possible.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to FIGS. 10A to 17.
The impedance converter 2 according to the second embodiment is an impedance converter based on a strip line, in which the distance between the line and the ground layer is gradually changed by gradually bringing the ground layers of the upper and lower surfaces closer to the strip line. Take
10A to 11C are diagrams showing the configuration of the impedance converter 2 according to the second embodiment, and FIG. 10A is a side view of a plane parallel to the line, and FIG. 10B is a schematic plan view seen from the top FIGS. 11A, 11B, and 11C are cross-sectional views of planes perpendicular to the line at positions aa ′, bb ′, and cc ′ shown in FIG. 10B, respectively. Here, FIG. 10B shows a state in which the ground layer 22 formed on the upper surface of the substrate 20 is removed for the sake of clarity.

  As shown in these figures, the impedance converter 2 according to the second embodiment includes a substrate 10 made of a dielectric such as benzocyclobutene (BCB) and a conductive material such as Au formed on both sides of the substrate. A ground layer 21 formed of a body member, a ground layer 22, and a plurality of lines 23 (23-1, 23-2, 23-3) formed similarly of a conductive member in the substrate 20 are provided. A feature is that the ground layer 22 gradually approaches these lines from one end side to the other end side of the plurality of lines 23 formed inside the substrate 20.

  More specifically, for example, in FIG. 10A and FIG. 10B, if the left side is the input side and the right side is the output side toward the paper surface, the substrate 20 is a line by forming the input side thicker than the output side. The distance between the line 23 on the input side and the distance between the line 23 on the input side and the ground layers 21-1 and 22-1 is h1, and the distance between the line 23 on the output side and the ground layers 21-3 and 22-3 is The distance h3 is h1> h3. The substrate 20 is formed to be gradually thinner toward the output side in the middle portion, and the distance h2 (h1> h2> h3) between the line 23 and the ground layers 21-2 and 22-2 in the middle portion. Is gradually decreasing from the input side to the output side (see FIGS. 10A and 11C).

  The above-described impedance converter 2 can be manufactured, for example, by the following manufacturing process.

First, a dielectric such as benzocyclobutene or polyimide is deposited on a substrate to form a dielectric layer. After that, in the case of dry etching, first the portion to be deepest (the portion on the output side in FIGS. 10A and 10B) is patterned by photolithography, and the patterned photoresist is used as an etching mask to aim the dielectric layer. Etch to a depth of
Subsequently, the second deep etching portion (portion adjacent to the previously etched region) is patterned by photolithography so that the connection portion with the previously etched region has a step shape. Etch to the target depth. This process is repeated until the desired step shape is obtained in the middle part.

Moreover, when using a photosensitive material for a collector layer, level | step difference shape creation is possible by the simple method only by photolithography. For example, it is possible to manufacture different photomasks for different depths, change exposure conditions such as the exposure amount and depth of focus at the time of photolithography for each mask, and obtain a step shape corresponding to the exposure conditions during development. Become. For example, the photolithography may be performed so that the exposure amount is large at the output side of FIG. 10B and the exposure amount is small at the input side.
Furthermore, after forming the step shape, if the entire surface is processed by reactive ion etching or the like, a smoother shape can be created from the input side to the output side.

  Furthermore, when the dielectric layer can be processed by a nanoimprinting method or the like, the dielectric layer having a desired surface shape can be easily formed by the special imprint pattern having this shape. This method is applicable to any of the first and second embodiments. Thereby, the characteristic impedance can be gradually converted while maintaining the line width.

  Next, a simulation regarding the relationship between the distance between the line 23 and the ground layers 21 and 22 and the impedance will be described. Also in this simulation, similarly to the description in the first embodiment, Au metal is used for the ground layer 21, the ground layer 22 and the line 23, and a benzocyclobutene (BCB) substrate (εr = 2.7) for the substrate 20. Assuming that the line length is 300 μm, the characteristic impedance on the output side of the impedance converter according to the present embodiment is compared with the characteristic impedance on the output side of the impedance converter using a conventional tapered line.

Also in this simulation, for both impedance converters, the line width on the input side was fixed at 4 μm and the inter-line gap (G) was fixed at 4 μm. Therefore, while the line width of the impedance converter according to the present embodiment is fixed at 4 μm on both the input side and the output side, the impedance converter using the conventional tapered line has the line width W of the output side. As a parameter, it was changed from 4 μm to 8 μm.
In this simulation, as shown in FIG. 12, the distance h between the line 23 of the impedance converter according to the present embodiment and the ground layers 21 and 22 is used as a parameter. In the conventional impedance converter using a tapered line, the distance between the line and the ground layer is fixed at 7 μm both above and below.

  FIG. 13 shows the line width (W) and the characteristic impedance (A) on the output side of the impedance converter according to the present embodiment, calculated under the above conditions, and the output of the impedance converter using the conventional tapered line. It is a graph which shows the relationship with the characteristic impedance (B) of the side. Also in FIG. 13, the distance h between the line 23 and the ground layers 21 and 22 is used as a parameter, and the line width (W) and the substantial interline distance (W + G) are used as the index of the effect on the vertical axis.

  In FIG. 13, the line indicated by “A” represents the change of the characteristic impedance on the output side of the impedance converter according to the present embodiment, and the line indicated by “C” represents the output of the impedance converter using the conventional tapered line. Represents the change in the characteristic impedance on the side. From this, it can be seen that, in the case of the impedance converter according to the present embodiment, the characteristic impedance on the output side can be changed without changing the line width or the distance between the lines.

  FIG. 14 shows the relationship between the characteristic impedance of the impedance converter according to the present embodiment and the distance h between the line 23 and the ground layers 21 and 22. From FIG. 14, in the impedance converter according to the present embodiment, the distance h between the line 23 and the ground layers 21 and 22 is h = 7 μm when the value of the characteristic impedance is 60 Ω, and the value of the characteristic impedance is At 35Ω, h = 2 μm, and it can be seen that when the value of the distance h changes from 7 to 2, the characteristic impedance at the output side changes from 60Ω to 35Ω.

  On the other hand, the characteristic impedance of the output side of the impedance converter using the conventional tapered line has a line width from 4 μm to 12 μm (when converted to interline distance, W + G from 8 μm to 16 μm, as shown in FIG. ) As it gets larger, it decreases from 60Ω to 37Ω.

  Next, the amount of crosstalk will be compared between the impedance converter using the conventional tapered line and the impedance converter according to the present embodiment. FIGS. 15A and 15B are models of the impedance converter according to the present embodiment using an electromagnetic field simulator Sonnet-EM. The model of the conventional impedance converter is identical to that shown in FIGS. 6A and 6B.

  In order to compare the amount of crosstalk, the gap G between lines was fixed at 4 μm, the thickness of the line was also fixed at 2 μm, and the characteristic impedance was adjusted to 50 Ω. In the model of the impedance converter using the conventional tapered line shown in FIGS. 6A and 6B, the line width W = 6.5 μm, and the distance between the line and the ground h = 7 μm. Further, in the model of the impedance converter according to the present embodiment shown in FIGS. 15A and 15B, the line width W = 4 μm and the line-ground interlayer distance h = 2.2 μm. In the simulation, the number of lines in the output side of the impedance converter is two in order to simplify the calculation.

  By setting the port numbers for the input and output ends of the line as shown in FIG. 6B and FIG. 15B, and examining the results of the S parameters, it is possible to directly evaluate the crosstalk amount.

  16 and 17 represent backward (near end) crosstalk and forward (far end) crosstalk, respectively. More specifically, FIG. 16 shows the ratio (S31) to the voltage appearing at Port 3 when a signal is given to Port 1, and FIG. 17 shows the voltage ratio (S41) between Port 1 and Port 4. Both are displayed in decibels in order to clarify the difference. In FIGS. 16 and 17, the line indicated by “A” represents the crosstalk of the conventional impedance converter, and the line indicated by “C” represents the crosstalk of the impedance converter according to the present embodiment.

  From FIG. 16 and FIG. 17, it is understood that the backward crosstalk by the impedance converter according to the present embodiment is smaller by about 5 dB in a wide range of 0 GHz to 100 GHz than the conventional one. Further, it is also understood that forward crosstalk is small by about 0 to 5 dB in a wide range of 35 GHz to 100 GHz.

As described above, according to the impedance converter 2 according to the present embodiment, the upper and lower ground layers 21 and 22 are gradually brought closer to the strip line without changing the width of the line 23 or the gap between the lines. Also, by adjusting the distance between the line 23 and the ground layer 21 and the distance between the strip line and the ground layer 22, a desired characteristic impedance value can be set, and the input side and output of the line It is possible to form impedance transformers with different characteristic impedances on the side. In addition, since the line is brought closer to the ground layer, the effect of reducing crosstalk can also be obtained.
Therefore, according to the present embodiment, it is possible to form an impedance converter applicable to high density mounting, which achieves both miniaturization of pad spacing, improvement of wiring density and reduction of crosstalk noise between wirings. .

  In the present embodiment, both the upper and lower ground layers 21 and 22 are gradually brought close to the line 23 from the input side to the output side, but even if only one of the ground layers is brought close to the line 23 Good.

Further, although the characteristic impedance on the output side of the impedance converter is reduced, it is also possible to form an impedance converter in which the characteristic impedance on the input side is reduced.
In the above embodiment, although an example in which three signal lines (transmission lines) are provided has been described, the number of lines is not limited to this, and two or four or more multi-lanes may be used. It goes without saying that there may be.

  1, 2 ... impedance converter (strip line), 10, 20 ... substrate, 11, 12, 21, 22 ... ground layer, 13, 23 ... line (strip conductor), 14, 16 ... via, 15, 17 ... pad .

Claims (6)

A substrate made of dielectric,
A first conductor layer formed on one surface of the substrate and a second conductor layer formed on the other surface of the substrate;
And a plurality of strip-like lines of conductors formed inside the substrate and spaced from the first conductor layer and the second conductor layer,
At least one of the plurality of tracks is:
The distance between at least one of the first conductor layer and the second conductor layer is different between one end side and the other end side, and the first conductor layer and the second conductor layer extend from the one end side to the other end side An impedance converter characterized in that the distance to one of them gradually changes. In the impedance converter according to claim 1,
The plurality of tracks are
An impedance converter characterized in that it gradually approaches one of the first conductor layer and the second conductor layer from one end side to the other end side. In the impedance converter according to claim 2,
The plurality of tracks are
An impedance converter characterized by alternately approaching gradually to said 1st conductor layer and said 2nd conductor layer. In the impedance converter according to claim 1,
An impedance converter, wherein the first conductor layer and the second conductor layer gradually approach the plurality of lines from the one end side to the other end side of the plurality of lines. The impedance converter according to any one of claims 1 to 4, further comprising
A plurality of pads formed on one surface of the substrate and electrically isolated from the first conductor layer and the second conductor layer;
An impedance converter comprising: a plurality of vias electrically connecting an end of the plurality of lines and the plurality of pads. The impedance converter according to any one of claims 1 to 5, wherein
The said board | substrate consists of a dielectric containing benzocyclobutene. The impedance converter characterized by the above-mentioned.