JP6270762B2 - IC circuit - Google Patents

Description

The present invention relates to I C circuit, an IC circuit having a transmission line path to improve the group delay characteristics, particularly in grounded coplanar line.

  In recent years, communication systems have been steadily increasing in speed, and discussions for practical application of communication systems of 50 Gbit / s and 100 Gbit / s have been actively conducted. In a communication apparatus compatible with such a high-speed communication system or a measurement apparatus that evaluates the quality of a communication apparatus, it is necessary to transmit a high bit rate digital signal while suppressing waveform deterioration.

  For example, an apparatus for measuring an error rate of a digital signal transmits and receives a pulse pattern signal such as a pseudo random bit sequence to / from a test object via a transmission line. Since such a pulse pattern signal includes a fundamental wave component and a harmonic component, the transmission line is required to have good frequency characteristics over a wide band from direct current to high frequency.

  Conventionally, as a transmission line for inputting and outputting a high-speed electric signal, a thin-film signal wiring is formed on one surface, a conductive thin-film electric reference surface is formed on the other surface, and the other surface is One in which an electrical reference surface is formed by digging into one surface is known (see, for example, Patent Document 1).

  FIG. 11 shows the configuration of the transmission line disclosed in Patent Document 1. As shown in the perspective view of FIG. 11A, a high-speed signal amplifier IC 202 having a high frequency band of 10 GHz or more is mounted on a plastic substrate 201. Microstrip lines are formed on a plastic substrate 201 as high-speed signal lines 203a and 203b for signal input / output with respect to the high-speed signal amplifier IC202. The high-speed signal amplifier IC 202 is bare-chip mounted on the electrode pad 205 formed on the plastic substrate 201 with the surface on which the electrode pattern is formed, using solder bumps. SMA type high frequency connectors 204a and 204b are attached to both ends of the high-speed signal lines 203a and 203b, and a gain characteristic which is a ratio of the input signal intensity and the output signal intensity of the high-speed signal amplifier IC 202 can be measured. Yes.

  A dig 206 is formed on the bottom surface of the plastic substrate 201 and below the high-speed signal lines 203a and 203b. A ground surface 207 is formed on the wall surface of the digging 206 so that the impedance of the high-speed signal lines 203a and 203b is 50Ω by conductive metal plating. Further, the entire high-speed signal amplifier IC 202 is sealed with a sealing resin 208 in order to protect the element from moisture and the like.

  As shown in the cross-sectional view of FIG. 11B, the high-speed signal lines 203 a and 203 b are divided into an air portion and a portion covered with the sealing resin 208. Therefore, the ground surface 207 is formed by changing the depth of the dug 206 so that the characteristic impedance in the portion covered with the sealing resin 208 is equal to the characteristic impedance in the air portion.

  The graph of FIG. 12 shows the frequency characteristics of the high-speed signal amplifier IC202. The 3 dB frequency response band is 12 GHz, and stable frequency characteristics are obtained in the frequency range of 0.1 GHz to 10 GHz.

  In addition, although the transmission line which comprises a grounded coplanar line is disclosed by patent document 1, it does not disclose about the frequency characteristic of the transmission line of a grounded coplanar line structure.

JP 2004-40257 A

  However, in the configuration disclosed in Patent Document 1, the frequency characteristic of the group delay cannot be extended to, for example, a 100 GHz millimeter wave band, as can be seen from the fact that the 3 dB frequency response band of the gain frequency characteristic is 12 GHz. Further, Patent Document 1 does not disclose the improvement of the frequency characteristics of a single grounded coplanar line.

The present invention was made to solve such conventional problems, provides an IC circuit having a millimeter wave band to the group delay characteristics of 100GHz has a transmission line path good grounded coplanar line structure The purpose is to do.

In order to solve the above problems, an IC circuit according to claim 1 of the present invention includes an insulating substrate, a central conductor formed on the surface of the substrate, and predetermined surfaces on both sides of the central conductor on the surface of the substrate. A surface ground conductor formed at a distance; a back surface ground conductor formed on the back surface of the substrate; and a plurality of through holes that electrically connect the surface ground conductor and the back surface ground conductor; / Ms including a transmission line having a grounded coplanar line structure for transmitting a digital signal having a bit rate of at least / s, a signal electrode, and a ground electrode formed on both sides of the signal electrode. there, at both sides of the substrate, side ground conductor which is electrically connected is formed in the rear surface ground conductor and the surface ground conductor, adjacent to the transmission direction of the digital signal Cormorant Ri der spacing 0.5mm below the through hole, at least one end face of the substrate, an end surface ground conductor electrically connected to the surface ground conductor and the backside ground conductor and the side ground conductor Each of the surface ground conductors is electrically connected to each ground electrode by a bonding wire at a position closer to the MMIC than a through hole closest to the MMIC among the plurality of through holes. The back surface grounding conductor is grounded from the end surface side of the substrate through the bonding wire and the end surface grounding conductor .

The present invention, the group delay characteristics to microwave band of 100GHz is to provide an IC circuit having a transmission line path good grounded coplanar line structure.

It is a perspective view which shows the structure by the side of the surface of the transmission line as the 1st Embodiment of this invention. It is a perspective view which shows the structure by the side of the back surface of the transmission line as the 1st Embodiment of this invention. It is the sectional view on the AA line of FIG. It is a perspective view which shows a simulation model with a side ground pattern and a TH pitch of 0.5 mm. It is a perspective view which shows a simulation model without a side ground pattern and having a TH pitch of 0.5 mm. 6 is a graph showing simulation results of group delay characteristics of the models shown in FIGS. It is a graph which shows the simulation result of the group delay characteristic of the model shown in FIGS. It is a graph which shows the simulation result of the group delay characteristic in case TH pitch is 0.5 mm and (phi) 0.15. It is a perspective view which shows the structure of the transmission line as the 2nd Embodiment of this invention. It is a top view which shows the structure in case the transmission line as the 2nd Embodiment of this invention is connected to the transmission line of MMIC. It is the perspective view and sectional drawing which show the structure of the conventional transmission line. It is a graph which shows the frequency characteristic of the conventional transmission line.

Hereinafter, an embodiment of an IC circuit having a transmission line circuit according to the present invention will be described with reference to the drawings. The transmission line of the present invention is a transmission line for transmitting a digital signal having a high bit rate exceeding, for example, 50 Gbit / s, and includes, for example, an MMIC (Semiconductor component such as a field effect transistor (FET)). In a measuring apparatus or the like on which a microwave monolithic integrated circuit) is mounted, the MMIC transmission line can be used for connection to a transmission line of another component, an input / output connector, or the like.

(First embodiment)
First, the structure of the transmission line 1 as the 1st Embodiment of this invention is demonstrated. 1 and 2 are perspective views showing the configuration of the transmission line 1 of the present embodiment. 3 is a cross-sectional view taken along line AA of FIG.

  As shown in FIGS. 1 to 3, the transmission line 1 of the present embodiment has a so-called grounded coplanar line structure, and includes an insulating substrate 11 and a signal line pattern 12 formed on the surface of the substrate 11. The ground patterns 13a and 13b formed on both sides of the signal line pattern 12 at a predetermined distance on the surface of the substrate 11, the ground pattern 14 formed on the entire back surface of the substrate 11, and the ground patterns 13a and 13b. And a through hole 15 for electrically connecting the ground pattern 14.

  Further, the transmission line 1 of the present embodiment is formed on both side surfaces of the substrate 11 in addition to the above-described grounded coplanar line structure, and is electrically connected to the ground patterns 13a and 13b and the ground pattern 14. 16.

  For the substrate 11, quartz glass, ceramic, or the like can be used. The through hole 15 is formed by drilling the substrate 11 with a laser or the like so as to penetrate the substrate 11. The through hole 15 is electrically connected to the ground patterns 13a and 13b and the ground pattern 14 by depositing a conductive material such as gold on the inner wall surface or by embedding a conductive material.

  The signal line pattern 12, the ground patterns 13a, 13b, and 14 and the side ground pattern 16 are formed by forming a mask pattern on the substrate 11 on which the through holes 15 are formed, and depositing a gold thin film by sputtering. At this time, a gold thin film is preferably deposited on the side wall of the through hole 15 at the same time.

  The gap width between the signal line pattern 12 and the ground patterns 13a and 13b is set to a value at which the characteristic impedance of the transmission line 1 becomes 50Ω.

  In a normal grounded coplanar line having no side ground pattern 16 on both side surfaces of the substrate 11, the potentials of the ground patterns 13 a and 13 b and the ground pattern 14 are equalized by conducting through the through holes 15.

  However, a digital signal is composed of a superposition of a fundamental wave, which is a repetition frequency, and harmonics having a frequency that is an integer multiple of the repetition frequency. If the bit rate of the transmitted digital signal increases, the fundamental wave and harmonics The wavelength of each becomes shorter. For this reason, in order to make the ground patterns 13a and 13b and the ground pattern 14 always have the same potential at each position in the transmission direction (Y direction) of the digital signal, the wavelength of the fundamental wave and the harmonic wave is shortened. It is necessary to increase the number of holes 15 to narrow the interval between the through holes 15 in the Y direction. However, the interval between the adjacent through holes 15 is limited to at least twice the diameter of the through holes 15, more preferably at least three times, due to manufacturing limitations due to hole processing accuracy and substrate strength.

  When the bit rate of the digital signal to be transmitted is increased and the interval between the through holes 15 is relatively wide with respect to the fundamental wave and the harmonic wave, other than the TEM mode which is the original transmission mode of the grounded coplanar line. A transmission mode occurs. As a result, resonance occurs, and the group delay characteristics of frequencies before and after the resonance frequency are greatly deteriorated. This causes the waveform to collapse in the transmission of a digital signal having a high bit rate.

  Therefore, in the present embodiment, the conduction between the front and back ground patterns 13a, 13b, and 14 is established not only from the through hole 15 but also from the side ground pattern 16 located on both sides of the substrate 11. Thereby, even with respect to a high bit rate digital signal, the ground patterns 13a and 13b and the ground pattern 14 can be equipotential at each position in the transmission direction (Y direction).

  As described above, by providing the side ground pattern 16 on both side surfaces of the substrate 11 in addition to the through hole 15, the frequency characteristic is improved, and a digital signal transmission line having a good group delay characteristic up to 100 GHz can be realized. In particular, in transmission of a digital signal having a bit rate exceeding 50 Gbit / s, high-quality transmission with little waveform deterioration is possible.

  FIGS. 6 and 7 show the results of electromagnetic field simulations on the group delay characteristics from 50 GHz to 99 GHz for the model of the transmission line 1 of the present embodiment shown in FIGS. In this simulation, changes in the group delay characteristics were examined according to the presence or absence of the side ground pattern and the distance between the through holes in the substrate length direction (hereinafter also referred to as “TH pitch”).

  FIG. 1 shows a model having a side ground pattern and a TH pitch of 1 mm. FIG. 4 shows a model having a side ground pattern and a TH pitch of 0.5 mm. FIG. 5 shows a model with no side ground pattern and a TH pitch of 0.5 mm.

Other simulation conditions are as follows.
Substrate: relative dielectric constant 3.58, dielectric loss tangent 1 × 10 ⁻⁴ , width 1.6 mm, length 3.0 mm, thickness 0.2 mm
・ Signal line pattern width: 0.35mm
・ Gap width between signal line pattern and ground pattern: 0.08mm
・ Signal line pattern, ground pattern, and side ground pattern: 1 μm thick gold ・ Through hole distance from the center of the signal line pattern: 0.5 mm
・ Diameter of through hole: φ0.2

The following can be understood from the simulation result shown in FIG.
When the TH pitch is 0.5 mm and there is a side ground pattern (FIG. 4) and when there is no side ground pattern (FIG. 5), an inflection point is seen in the vicinity of 82 GHz of the group delay characteristic when there is no side ground pattern. In the group delay characteristic when there is a side ground pattern, no inflection point is found near 82 GHz. It can be said that the group delay characteristic when the TH pitch is 0.5 mm and the side ground pattern is present exhibits very good characteristics at a frequency of 50 GHz to 99 GHz.

Moreover, the following can be understood from the simulation result shown in FIG.
When there is a side ground pattern and the TH pitch is 0.5 mm (FIG. 4) or 1 mm (FIG. 1), the group delay characteristic when the TH pitch is 1 mm is 85 GHz or more, and a plurality of inflection points can be seen. It can be said that the group delay characteristic when the TH pitch is narrow 0.5 mm shows a very good frequency characteristic at a frequency of 50 GHz to 99 GHz.

  In the above analysis, the TH pitch is set to 0.5 mm. However, the TH pitch produced by a general thin film substrate is 0.6 mm (three times as large as φ0.2) when the diameter of the through hole is φ0.2. Is the limit. In order to make the TH pitch narrower than 0.5 mm, it is conceivable to reduce the diameter of the through hole. For example, if φ0.15, the TH pitch can be reduced to 0.45 mm.

  FIG. 8 shows a simulation result of the group delay characteristic when the TH pitch is 0.5 mm, φ0.15, and there is a side ground pattern. In this case, the group delay characteristics similar to those obtained when the TH pitch shown in FIGS. 6 and 7 is 0.5 mm and φ0.2 and the side ground pattern is provided are obtained.

  As described above, the transmission line 1 of the present embodiment has the grounded coplanar line structure, and the side ground patterns 16 are formed on both side surfaces of the insulating substrate 11. The side ground pattern 16 includes ground patterns 13 a and 13 b formed at a predetermined distance on both sides of the signal line pattern 12 formed on the surface of the substrate 11, and a ground pattern 14 formed on the back surface of the substrate 11. , Is electrically connected to.

  Thus, by providing a side ground pattern in addition to a through hole for a transmission line having a grounded coplanar line structure, a group delay characteristic up to a millimeter wave band of 100 GHz as compared with a case where only a through hole is provided. In the transmission of a digital signal such that the bit rate exceeds 50 Gbit / s, high-quality transmission with little waveform deterioration becomes possible.

(Second Embodiment)
Subsequently, a transmission line 2 as a second embodiment of the present invention will be described with reference to the drawings. Note that the description of the same configuration and operation as in the first embodiment will be omitted as appropriate.

  As shown in FIG. 9, in addition to the configuration of the first embodiment, the transmission line 2 of the present embodiment includes at least one of the front end surface and the rear end surface of the substrate 11 perpendicular to the digital signal transmission direction (Y direction). , Ground conductive patterns 21a, 21b, 22a, 22b electrically connected to the ground patterns 13a, 13b, 14 and the side ground pattern 16 are formed.

  FIG. 10 shows a configuration when the transmission lines of the two MMICs 30 and 40 are connected by the transmission line 2. The ground electrodes 31a and 31b of the MMIC 30 are electrically connected to the ground patterns 13a and 13b of the transmission line 2 by bonding wires 32a and 32b, respectively. The signal electrode 31c of the MMIC 30 is electrically connected to the signal line pattern 12 of the transmission line 2 by a bonding wire 32c.

  Similarly, the ground electrodes 41a and 41b of the MMIC 40 are electrically connected to the ground patterns 13a and 13b of the transmission line 2 by bonding wires 42a and 42b, respectively. Further, the signal electrode 41c of the MMIC 40 is electrically connected to the signal line pattern 12 of the transmission line 2 by a bonding wire 42c.

  For example, if attention is paid to the MMIC 30 side, the ground patterns 13a and 13b on the surface are grounded at positions closer to the MMIC 30 than through holes closest to the MMIC 30 via the bonding wires 32a and 32b. On the other hand, in the conventional transmission line that does not include the side ground pattern 16 or the ground conductive patterns 21a and 21b, the grounding position closest to the MMIC 30 for the ground pattern on the back surface is the position of the through hole closest to the MMIC 30. .

  On the other hand, in the transmission line 2 of the present embodiment, the ground pattern 14 on the back surface is also grounded from the end closest to the MMIC 30 or MMIC 40 via the ground conductive patterns 21a, 21b, 22a, 22b. Become.

  As a result, the ground patterns 13a and 13b and the ground pattern 14 are always likely to be equipotential at each position in the digital signal transmission direction (Y direction), and as a result, the performance of the entire IC circuit can be stabilized.

  As described above, the transmission line 2 of the present embodiment has the ground conductive patterns 21a, 21b, 22a, and 22b electrically connected to the ground patterns 13a and 13b and the ground pattern 14 on at least one end surface of the substrate 11. Is formed.

  Thereby, in addition to the effect of the first embodiment, the ground patterns 13a and 13b and the ground pattern 14 are more likely to be equipotential than the first embodiment, and the IC connected by the transmission line 2 of the present embodiment. The performance of the parts is improved.

1, 2 Transmission line 11 Substrate 12 Signal line pattern (center conductor)
13a, 13b Ground pattern (surface ground conductor)
14 Ground pattern (Back grounding conductor)
15 through hole 16 side ground pattern (side ground conductor)
21a, 21b, 22a, 22b Ground conduction pattern (end surface grounding conductor)
30, 40 MMIC
31a, 31b, 41a, 41b Ground electrode 31c, 41c Signal electrode 32a, 32b, 32c, 42a, 42b, 42c Bonding wire

Claims (1)

Insulating substrate (11), center conductor (12) formed on the surface of the substrate, and surface ground conductors (13a, 13a, 13b) formed on the surface of the substrate at a predetermined distance on both sides of the center conductor 13b), a back-surface ground conductor (14) formed on the back surface of the substrate, and a plurality of through holes (15) for electrically connecting the front-surface ground conductor and the back-surface ground conductor, and 50 Gbit / s A transmission line (1) having a grounded coplanar line structure for transmitting a digital signal having the above bit rate;
And an MMIC (30, 40) including signal electrodes (31c, 41c) and ground electrodes (31a, 31b, 41a, 41b) formed on both sides of the signal electrodes,
Side ground conductors (16) electrically connected to the surface ground conductor and the back ground conductor are formed on both side surfaces of the substrate,
Ri der spacing 0.5mm below the through hole adjacent to the transmission direction of said digital signal,
End surface ground conductors (21a, 21b, 22a, 22b) electrically connected to the front surface ground conductor, the back surface ground conductor, and the side surface ground conductor are formed on at least one end surface of the substrate,
Each surface ground conductor is electrically connected to each ground electrode by a bonding wire (32a, 32b, 42a, 42b) at a position closer to the MMIC than a through hole closest to the MMIC among the plurality of through holes. Connected,
The IC circuit , wherein the back ground conductor is grounded from the end face side of the substrate via the bonding wire and the end face ground conductor .

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