JP2007123950A - Coaxial line-flat substrate conversion structure and high-frequency signal converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce reflection caused by a conversion section in the conversion of a high-frequency coaxial line and a flat substrate line. <P>SOLUTION: A high-frequency signal converter comprises the high-frequency coaxial line fitted in a metal package 110 into which a coaxial connector 111 is inserted; and a coplanar circuit 100 having a rear surface conductor 103 on which a center conductor 102 and a surface gland 101 are formed, while the lower surface is in contact with the metal package 110. One portion of the conductor in the vicinity of the conversion unit of the surface gland 101 is removed to form a conductor removed section 108, which can reduce the electric field distribution in the conversion unit and can suppress lowering of the characteristic impedance, thereby suppressing reflection. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coaxial line-planar substrate conversion structure that converts a high-frequency electrical signal between a coaxial line and a planar substrate line, and more particularly to a coaxial line-planar substrate conversion structure and a high-frequency signal converter that have low reflection over a wide band. .

  With the explosive demand for broadband multimedia communication services such as the Internet, development of higher capacity and higher performance optical fiber communication systems and microwave communication systems is required. For this reason, improvement of the performance of the high frequency module used for a large-scale communication system is a very important subject.

  Conventionally, coaxial line type connectors have been widely used as input / output modes of such high-frequency modules. This coaxial line is widely used because it has many advantages such as easy interconnection between coaxial line connectors and excellent high frequency characteristics.

  However, since a coaxial line type high frequency line is difficult to handle inside the high frequency module, a planar substrate line suitable for mounting such as a microstrip line or a coplanar circuit with a signal line exposed on the surface is used. In the case of such a high-frequency module, a coaxial line connector is used as an input / output interface of the module, and a planar substrate line is used inside the module. Therefore, high-frequency signal conversion between the coaxial line and the planar substrate line is required in the input / output unit. . In recent years, many high-frequency packages that employ a structure that does not use coaxial connectors, which are excellent in miniaturization, have been put into practical use. However, even in such high-frequency modules, it is better to convert them to coaxial lines when performing operations such as evaluation and selection. For convenience, special tools have been used to convert a planar substrate line of a high frequency package to a coaxial line.

  As a coaxial line-planar substrate line conversion structure of these high-frequency signal converters, there is a coplanar circuit conversion structure with a coaxial line-back conductor shown in FIG. FIG. 5 is a schematic cross-sectional view for explaining the conversion between a high-frequency coaxial connector of a coaxial line-planar substrate line conversion structure and a coplanar circuit with a back conductor in a conventional high-frequency signal converter. A cross-sectional top view and (b) are side cross-sectional views. Except for the structure of the surface ground 501, the configuration is the same as that of the first embodiment, and the description will be made in the first embodiment.

Further, as a coaxial line-planar substrate line for the purpose of improving high-frequency characteristics, the coaxial-strip conductor converter described in Patent Document 1 is fitted into a fitting portion recess formed in a metal case, and an insulating portion And a high-frequency coaxial connector into which the core wire is inserted, and a ceramic substrate having a lower surface in contact with the metal case and a strip conductor disposed on the upper surface, and a spacing portion formed between the insulating portion and the strip conductor And a cylindrical second air gap formed between the core wire and the metal case at the separation portion, and the second air gap is cut off at the upper part of the cylindrical shape by a plane parallel to the central axis of the core wire. The center line of the core wire and the center axis of the second air gap coincide with each other, and the upper surface of the core wire and the upper surface of the strip conductor are on the same plane. With this structure, the characteristic impedance can be matched in the conversion between the high-frequency coaxial line and the strip conductor over a wide band from direct current to 50 GHz.
JP 2002-198129 A (FIG. 1)

  The conversion from the coaxial line to the microstrip line as the conversion structure of the coaxial line to the planar substrate line has the following problems in high frequency characteristics. The microstrip line has a structure in which a dielectric is sandwiched between a strip conductor on the front surface and a ground on the back surface. On the other hand, in general high-frequency ICs, the pads for inputting / outputting signals such as ground and data and power are all on the surface. In such a case, if the back surface ground of the microstrip line and the front surface ground of the IC are directly bonded to the gold wire, the gold wire connecting each of them becomes long, so that the inductance of the gold wire increases, and the characteristics are particularly high in the high frequency region. to degrade. In order to avoid the deterioration of the high frequency characteristics, there is a method of converting from a microstrip line to a coplanar circuit in the middle of a planar waveguide. However, even in this method, since the conversion between the microstrip line and the coplanar circuit is newly introduced, the deterioration of the high frequency characteristics cannot be avoided.

  Further, in the coplanar circuit conversion structure with the coaxial line-back conductor shown in FIG. 5, the electric field distribution in the electric signal conversion unit is shown in FIG. 2 (b) shown for comparison in the first embodiment described later. An electric field distribution 520 that propagates in the air is generated. In a normal high-frequency line, the characteristic impedance is generally made to be 50Ω, but in this conversion section, the air passes between the core line 514 of the coaxial line and the surface ground 501 of the coplanar circuit 500. Since the propagating electric field distribution 520 is large, the characteristic impedance is considerably lower than 50Ω. As a result, reflection due to the discontinuity of the characteristic impedance occurred in the electric signal conversion unit.

  Further, the coaxial-strip conductor converter disclosed in Patent Document 1 as a method for suppressing reflection at these converters and increasing the bandwidth has some practical problems. First, it is necessary to make the high-frequency coaxial line core wire and the strip substrate conductors the same height, and in order to suppress deterioration of the high-frequency characteristics, it is necessary to reduce the distance between the coaxial line core wire and the strip conductor. For this reason, the processing tolerance of the metal case cannot be increased so much. Secondly, in this converter, the core wire of the high-frequency coaxial line and the strip conductor on the ceramic substrate are fixed by ribbon bonding. Usually, such a coaxial-strip conductor conversion part is located near the inner wall of the metal case as shown in FIGS. 1 and 2 of Patent Document 1, so that the workability of a normal ribbon bonding apparatus is poor, and a special bonding apparatus is used. There are problems such as the need to use.

  An object of the present invention is to provide a coaxial line-conversion line substrate conversion structure using a coplanar circuit with a back conductor, which has excellent high frequency characteristics and does not require a special manufacturing process or device, and a high frequency signal conversion having the conversion structure. Is to provide a vessel.

The coaxial line-planar substrate line conversion structure of the present invention is
It is the coaxial line-planar substrate line conversion structure in the signal converter for high frequencies for performing the conversion of a coaxial line and a plane board line comprised on the metal package. The planar substrate line is a coplanar circuit having a center conductor, a front surface ground conductor, and a back surface conductor, and a part close to the center conductor of the front surface ground conductor of the coplanar circuit is in a predetermined part near the conversion portion with the coaxial line. , Being removed in a predetermined shape.

  A part of the surface ground conductor removed in a predetermined portion near the conversion portion with the coaxial line may be located 30 to 200 μm away from the end portion of the surface ground conductor on the center conductor side of the surface ground conductor. The shape of a part of the surface ground conductor removed in a predetermined portion near the conversion portion with the coaxial line is a rectangular shape whose long side is parallel to the central conductor, and the width of the short side of the rectangular shape is 20 μm to 100 μm, the length of the long side may be 200 μm to 600 μm, is a triangular shape that is long in the direction parallel to the central conductor, the length of one side of the triangle is 20 μm to 100 μm, and the length of the other two sides It may be 200 μm to 600 μm.

The high-frequency signal converter of the present invention is
The coaxial line-planar substrate conversion structure described above is provided.

  A feature of the coaxial line / planar line substrate conversion structure in the present invention is that a part of the front surface ground conductor of the coplanar circuit with the back conductor is removed in the conversion unit. Good frequency characteristics with less reflection can be realized in a coplanar circuit with a coaxial line and a back conductor, which was difficult with the structure.

  There is an effect that it is possible to provide a high-frequency module for ultra-high-speed optical communication and microwave radio communication that is excellent in high-frequency characteristics with low reflection over a wide band.

  This is because by removing a part of the surface ground conductor of the coplanar circuit with the back conductor in the signal conversion unit, it is possible to reduce the electric field distribution on the surface ground, suppress the decrease in characteristic impedance in the conversion region, This is because reflection can be reduced. As shown in FIG. 3 to be described later, the specific simulation results are expected to have a reflection reduction effect in a wide range up to about DC to 50 GHz in the present invention compared to the conversion structure in which the surface ground conductor of the conventional example is not removed, In particular, the reflection reduction effect is large at about 30 dB at 30 to 40 GHz.

  In addition, the present invention has an effect that it can be manufactured at a cost that is not different from the conventional example.

  In the case of a planar waveguide using a high-frequency ceramic substrate including a coplanar circuit with a back conductor, the surface conductor is drawn on the upper surface conductor of the ceramic substrate by photolithography or a direct drawing method using a laser or the like and etched. However, in the case of the coplanar substrate with the back conductor according to the present invention, it is possible to manufacture by simply adding a pattern for removing the ground conductor to the lithography mask data in addition to the conventional product.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

(First embodiment)
1A and 1B are schematic views showing a coaxial line-planar substrate line conversion section according to a first embodiment of the present invention, in which FIG. 1A is a partial cross-sectional top view and FIG. 1B is a side cross-sectional view. As shown in FIG. 1A, the coaxial line-planar substrate line conversion structure of the high-frequency signal converter 10 according to the first embodiment of the present invention includes a high-frequency coaxial connector 111 and a coaxial line portion having a core wire 114. And a coplanar circuit 100 with a back conductor, and a metal package 110.

  First, the coplanar circuit 100 with the back conductor will be described. The coplanar circuit 100 with the back conductor includes a front surface ground 101, a center conductor 102, a through via 104 that conducts the back surface conductor 103 and the front surface ground 101, and a front surface ground 101 and a back surface conductor 103 provided on a signal input / output end face. It has a notch portion 105 for conducting. The width of the center conductor 102 and the gap 106 between the center conductor 102 and the surface ground 101 are formed so that the characteristic impedance is 50Ω. In the high frequency region, the width of the center conductor 102 needs to be narrow so as not to generate higher order modes of the coplanar circuit. On the other hand, if the width of the center conductor 102 is too narrow, there are many problems in mounting, and propagation loss increases.

  Further, at the center conductor tip 107 in the conversion region, which is a connection with the coaxial line, the width of the center conductor 102 is increased to about 200 μm to 400 μm in order to facilitate connection. Further, the conductor of the surface ground 101 of the coplanar circuit 100 is provided with a conductor removing portion 108 in which a part thereof is removed in a rectangular shape. The size of the removed surface ground 101 is preferably between 200 and 600 μm in the horizontal direction in the signal propagation direction and between 20 and 100 μm in the vertical direction. The reason is that in the horizontal direction, a length approximately equal to or slightly shorter than the center conductor tip 107, which is the location where the center conductor is expanded in the conversion region, is necessary. Further, regarding the width, 20 μm or more is necessary to obtain the effect of the present invention, and if it is 100 μm or more, the frequency characteristics deteriorate.

  This position is preferably 30 to 100 μm away from the end of the surface ground 101. This is because the width required for the surface ground 101 is 30 μm or more in order to obtain a sufficient ground for a high frequency, and a certain amount of width is required in consideration of manufacturing errors and ease of manufacturing. Also from a viewpoint, 30 micrometers or more are desirable. It is desirable that the conductor removal portion 108 from which the conductor is removed in the rectangular shape be separated from the through via 104 and the cutout portion 105 by 30 μm or more for the same reason.

  The coplanar circuit 100 is fixed to the metal package 110 using a conductive material such as solder. At this time, it is desirable in terms of frequency characteristics to mount the gap in the signal propagation direction between the coplanar substrate 100 and the metal package 110 as small as possible.

  Next, the metal package 110 will be described. A high frequency coaxial connector 111 is fixed in the metal package 110. In this high-frequency coaxial connector 111, a conductive material such as solder is put into a through hole 112 provided from the upper surface of the metal package 110 toward the insertion hole of the high-frequency coaxial connector 111, and the metal package 110 is heated and melted. It is fixed by cooling. The high-frequency coaxial connector 111 is also manufactured so that the characteristic impedance is 50Ω.

  The electric field distribution in the conversion part between the high-frequency coaxial connector 111 and the center conductor 102 in the first embodiment and the conventional example is as shown in FIG. 2A and 2B are schematic cross-sectional views showing the electric field distribution in the high-frequency coaxial connector and the conversion portion of the central conductor, FIG. 2A is the electric field distribution of the first embodiment, and FIG. Distribution. In the conventional example, since the electric field distribution 520 is observed in the air on the surface ground 501 in the conversion unit, the characteristic impedance of the conversion unit is considerably smaller than 50Ω, and high-frequency signal reflection occurs. On the other hand, in the structure shown in this embodiment mode, since the electric field distribution 120 in the air on the surface ground 101 can be reduced, a reduction in characteristic impedance can be suppressed and reflection can be suppressed.

  FIG. 3 is a frequency characteristic of reflection of the coaxial line-planar substrate line conversion structure of the high-frequency signal converter in the first embodiment of the present invention and the conventional example. As shown in FIG. 3, the specific simulation results are expected to have a reflection reduction effect in a wide range from DC to 50 GHz in the present invention, compared with the conversion structure in which the surface ground conductor of the conventional example is not removed, At 30 to 40 GHz, the reflection reduction effect is large at about 5 dB.

  Next, a manufacturing method of the high-frequency signal converter 10 having the coaxial line-planar substrate conversion structure shown in the first embodiment will be described. The coplanar circuit 100 with the back conductor is made using a dielectric substrate with a small loss of high-frequency signals, such as alumina ceramics (relative permittivity is 9 to 10). The dielectric substrate is formed with a through via 104 penetrating the front and back surfaces using a high-power laser or the like, and a notch 105 in the input / output portion of the electric signal. Next, using a vapor deposition apparatus such as sputtering, gold is deposited on both sides of the substrate with a thickness of about 1 μm. At this time, when the through via 104 or the cutout portion 105 is formed, the inner surface of the through via 104 or the cutout portion 105 is gold so that the front surface ground 101 and the back conductor 103 of the substrate are electrically connected. To do.

  Next, a photoresist is applied to the surface, and the central conductor 102 and the surface ground 101 are formed by photolithography. At this time, a part of the surface ground 101 is removed at the same time, and the conductor removal portion 108 of the rectangular surface ground conductor, which is a feature of the present invention, is produced.

  Next, a method for manufacturing the metal package 110 will be described. For the metal package 110, stainless steel having excellent workability, Kovar having a linear expansion coefficient close to that of alumina ceramics, or the like is used. Since the metal package 110 takes various shapes depending on the application, the focus is not on the entire configuration of the metal package 110 but on the portion shown in FIG. 1A which is a conversion portion necessary for the description of the present invention. A manufacturing method will be described. A hole of the coaxial connector fitting portion 113 for fitting the coaxial connector 111 is formed at a position where the high frequency coaxial connector 111 of the metal package 110 is inserted using a dedicated tool (not shown). A through hole 112 reaching the hole is also provided on the upper surface of the hole of the coaxial connector fitting portion 113. Further, gold plating is applied to the surface of the metal package 110 in order to improve electrical characteristics and to obtain reliability. Next, after inserting the high-frequency coaxial connector 111 into the metal package 110 and fixing it with a fixing jig (not shown), solder is inserted into the through hole 112 provided on the upper surface and the metal package 110 is heated to about 180 ° C. where the solder melts. Then, the metal package 110 is cooled to fix the high frequency coaxial connector 111.

  Next, the coplanar circuit 100 with the back conductor is attached to the metal package 110 using a metal having a low melting point such as solder. Finally, the core wire 114 of the coaxial line and the tip 107 of the central conductor 102 of the coplanar circuit 100 are soldered or the like. The conductive line 109 is connected to complete the coaxial line-planar substrate conversion structure.

(Second Embodiment)
4A and 4B are schematic views showing a coaxial line-planar substrate line conversion portion according to the second embodiment of the present invention, in which FIG. 4A is a partial cross-sectional top view and FIG. 4B is a side cross-sectional view. As shown in FIG. 4A, in the coaxial line-planar substrate line conversion structure according to the second embodiment of the present invention, the high-frequency signal converter 20 includes a high-frequency coaxial connector 211 and a coaxial line portion having a core wire 214. It is composed of a coplanar circuit 200 with a back conductor and a metal package 210.

  The structure of the high-frequency signal converter 20 and the coaxial line-planar substrate line conversion unit of the second embodiment is such that the conductor removal unit 108 of the surface ground 101 that is rectangular in the first embodiment has a triangular shape. Since the second embodiment is the same as the first embodiment except that the conductor removing portion 208 is used, the description of the same portion is omitted, and the conductor removing portion 208 will be mainly described.

  In the coplanar circuit 200 with the back conductor, the conductor of the front surface ground 201 of the coplanar circuit 200 is provided with a conductor removal portion 208 in which a part thereof is removed in the shape of a right triangle as shown in FIG. ing.

  The size of the conductor removal portion 208 removed from the surface ground 201 has a triangular shape that is between 200 and 600 μm in the horizontal direction in the signal propagation direction and between 20 and 100 μm in the vertical direction. The reason for this is that in the horizontal direction, a length approximately equal to or slightly shorter than the center conductor tip 207 in which the center conductor 202 is expanded in the conversion region is required. In addition, regarding the width, the effect of the present invention can be obtained at 20 μm or more, and the frequency characteristics deteriorate at 100 μm or more.

  Further, this position is desirably 30 to 100 μm away from the edge of the surface ground. The reason for this is that a surface ground width of 30 μm or more is required to obtain a sufficient ground for a high frequency, and that a certain amount of width is required in consideration of manufacturing errors and ease of manufacturing. Is desirable. For this reason, it is desirable that the through via 204 and the cutout portion 205 be separated by 30 μm or more for the same reason.

  Since the metal package 210 has the same configuration as the metal package 110 of the first embodiment, the description thereof is omitted.

  The electric field distribution in the conversion portion between the high-frequency coaxial connector 211 and the center conductor 202 in the second embodiment is the same as that shown in the first embodiment with reference to FIG. Since the electric field in the air on the surface ground 201 can be reduced as compared with the electric field distribution in the conversion part of 511 and the central conductor 502, a reduction in characteristic impedance in the conversion part can be suppressed and occurs in the conversion part. Reflection can be suppressed.

  The manufacturing method of the high-frequency signal converter 20 having the coaxial line-planar substrate conversion structure of the second embodiment also applies a photoresist on the surface and forms the central conductor 202 and the surface ground 201 by photolithography. Since the manufacturing method of the first embodiment is the same as that of the first embodiment except that a part of the surface ground 201 is removed and a triangular conductor removing portion 208 is provided at the same time, the description thereof is omitted.

  The manufacturing method of the conversion part necessary for the description of the present invention of the metal package 110 is also the same as the manufacturing method described in the first embodiment, and the description thereof is omitted.

  The coaxial line-planar substrate conversion structure of the present invention is not limited to the above-described embodiment described with reference to the drawings, and is applied and implemented so as to obtain the same effect for the same purpose. Can do. For example, the present invention can be applied not only to the rectangular shape or the triangular shape but also to other shapes such as a trapezoid as the shape of the conductor removal portion provided on the surface ground. It is also possible to make the center conductors all the same width by eliminating the center conductor tip widened to facilitate the connection of the center conductors in the conversion part. Further, the surface ground conductor can be a part of the substrate surface, and two or more coaxial line-planar substrate line conversion structures can be provided in the same metal package.

It is a schematic diagram which shows the coaxial line-planar board | substrate line | wire conversion part which is the 1st Embodiment of this invention. (A) is a partial cross-sectional top view. (B) is side sectional drawing. It is typical sectional drawing which shows the electric field distribution in the conversion part of a high frequency coaxial connector and a center conductor. (A) is an electric field distribution of the first embodiment. (B) is an electric field distribution in the case of the conventional example. It is the frequency characteristic of reflection of the coaxial line-planar substrate line conversion structure of the signal converter for high frequency in the 1st Embodiment of this invention and a prior art example. It is a schematic diagram which shows the coaxial line-planar board | substrate line | wire conversion part which is the 2nd Embodiment of this invention. (A) is a partial cross-sectional top view. (B) is side sectional drawing. It is typical sectional drawing for demonstrating conversion with the high frequency coaxial connector of the coaxial line-planar board | substrate line conversion structure and the coplanar circuit with a back surface conductor in the conventional signal converter for high frequency. (A) is a partial cross-sectional top view. (B) is side sectional drawing.

Explanation of symbols

10, 20, 50 High-frequency signal converter 100, 200, 500 Coplanar circuit 101, 201, 501 Front ground 102, 202, 502 Central conductor 103, 203, 503 Back conductor 104, 204, 504 Through-via 105, 205, 505 Notch 106, 206, 506 Gap 107, 207, 507 Center conductor tip 108, 208 Conductor removal 109, 209, 509 Conductive material 110, 210, 510 Metal package 111, 211, 511 High-frequency coaxial connector 112, 212, 512 Through-hole 113, 213, 513 Coaxial connector fitting portion 114, 214, 514 Core wire 120, 520 Electric field distribution

Claims (14)

In the coaxial line-planar substrate line conversion structure in the high-frequency signal converter for performing conversion between the coaxial line and the planar substrate line, which is configured on the metal package,
The planar substrate line is a coplanar circuit having a center conductor, a surface ground conductor, and a back conductor,
A portion of the coplanar circuit adjacent to the center conductor of the surface ground conductor is removed in a predetermined shape in a predetermined portion in the vicinity of the conversion portion with the coaxial line. Substrate line conversion structure.   A part of the surface ground conductor removed at a predetermined portion near the conversion portion with the coaxial line is located at a position 30 to 200 μm away from an end portion of the surface ground conductor on the center conductor side of the surface ground conductor. The coaxial line-planar substrate conversion structure according to claim 1, wherein   The shape of a part of the surface ground conductor removed in a predetermined portion near the conversion portion with the coaxial line is a rectangular shape whose long side is parallel to the central conductor. The coaxial line-planar substrate conversion structure according to any one of the above.   The coaxial line-planar substrate conversion structure according to claim 3, wherein a length of the rectangular short side is 20 μm to 100 μm and a length of the long side is 200 μm to 600 μm.   The shape of a part of the surface ground conductor of the coplanar circuit with the back conductor removed in a predetermined portion near the conversion portion with the coaxial line is a triangular shape that is long in a direction parallel to the center conductor. The coaxial line-planar substrate conversion structure according to claim 2.   The coaxial line-planar substrate conversion structure according to claim 5, wherein a length of one side of the triangle is 20 μm to 100 μm and a length of the other two sides is 200 μm to 600 μm.   The coaxial line-planar substrate conversion according to any one of claims 1 to 6, wherein a width of the central conductor is locally expanded in the conversion portion with the coaxial line. Construction.   The coaxial line-planar substrate conversion structure according to any one of claims 1 to 7, wherein the coplanar circuit has at least one or more through vias for conducting the front surface ground conductor and the back surface conductor. .   9. The coplanar circuit according to claim 1, wherein the coplanar circuit includes a cutout portion provided with a conduction portion between at least one of the front surface ground conductor and the rear surface conductor on an outer peripheral portion of the coplanar circuit. The coaxial line-planar substrate conversion structure according to the item.   In the conversion part between the coaxial line and the coplanar circuit, any one of a low melting point metal that melts at 400 ° C. or less and a conductive adhesive that solidifies at a temperature of 400 ° C. or less in the conversion part of the coaxial line and the coplanar circuit. The coaxial line-planar substrate conversion structure according to any one of claims 1 to 9, wherein the coaxial line-planar substrate conversion structure is connected to each other.   The width of the central conductor of the coplanar circuit is 50 to 300 micrometers, and the distance between the central conductor and the surface ground conductor is 20 to 150 micrometers. The coaxial line-planar substrate conversion structure according to any one of 10.   The coaxial line-planar substrate conversion structure according to any one of claims 1 to 11, wherein a relative dielectric constant of a substrate of the coplanar circuit is 15 or less.   The coaxial line-planar substrate conversion structure according to any one of claims 1 to 12, wherein a thickness of the substrate of the coplanar circuit is 200 micrometers or more and 600 micrometers or less.   A high-frequency signal converter comprising the coaxial line-planar substrate conversion structure according to any one of claims 1 to 13.

Images