JP5148855B2 - Flat circuit board and Gunn diode oscillator using the same - Google Patents

Description

  The present invention relates to a flat circuit board and a Gunn diode oscillator using the same, and more particularly to a flat circuit board suitable for a high frequency oscillator capable of reducing variation in oscillation frequency and a Gunn diode oscillator using the same.

  In a high-frequency oscillator such as a microwave band or a millimeter wave band, a flat circuit board on which a high-power semiconductor device is mounted is formed on a flat board made of an alumina sintered body, an aluminum nitride sintered body, or the like having excellent thermal conductivity. A signal transmission line, a ground electrode, and the like are formed by the line.

  A Gunn diode oscillator, which is an example of this type of high-frequency oscillator, will be described. FIG. 3 is a partial cross-sectional view of the Gunn diode oscillator. On the surface of the Gunn diode 1, there are formed a cathode electrode 3 and an anode electrode 4 made of conductive protruding electrodes. A flat circuit board 2 on which the Gunn diode 1 is mounted has a signal transmission line 6 for transmitting a high-frequency signal and a surface ground electrode 7 formed on the surface of a flat board 5 made of aluminum nitride or the like having excellent thermal conductivity, and the back surface. A back ground electrode 8 is formed on the surface. As shown in FIG. 3, the cathode electrode 3 is connected to the signal transmission line 6, and the anode electrode 4 is connected to the surface ground electrode 7. Further, the front surface ground electrode 7 and the back surface ground electrode 8 penetrate the flat substrate 5 and are connected via via electrodes 9 filled with a conductive substance.

  In such a Gunn diode oscillator, it is known that the oscillation frequency varies when the interval 10 between the two via electrodes 9 changes. In order to reduce the variation in the oscillation frequency, it is necessary to always form the via electrode 9 at a predetermined position. As the method, the applicant of the present invention forms a via electrode by forming a concave portion on a sintered flat substrate by a microblasting method, filling a conductive material, and then thinning the plate substrate to a desired thickness. Proposed method.

FIG. 4 is an explanatory diagram of a method for manufacturing a flat substrate proposed by the applicant of the present application. First, the green sheet is sintered in an N ₂ atmosphere at 1800 ° C. for 9 hours to form a flat substrate 11 having a thickness of about 300 μm. Next, a photosensitive dry film 12 having a thickness of 100 μm serving as a mask material is laminated on the flat substrate 11 (FIG. 4a). In accordance with a normal photolithography method, the dry film 12 is patterned so as to open a part of the surface of the flat substrate 11 in the via electrode formation scheduled region (FIG. 4b). Subsequently, the fine abrasive grains 13 are sprayed from the nozzles at a high speed by a microblasting method to form the recesses 14 on the surface of the flat substrate 11 (FIG. 4c). Thereafter, by removing the dry film 12, a flat substrate 11 having a recess 14 formed on the surface is obtained (FIG. 4d).

  Next, a metal thin film 15 is formed on the surface of the flat substrate 11 using an electron beam vapor deposition apparatus or the like (FIG. 4e), and a photoresist 16 is formed so as to open a region where the recess 14 is formed by a normal photolithography method. Patterning is performed (FIG. 4f). Subsequently, a plating layer 17 made of a conductive metal such as gold is formed on the metal thin film 15 exposed in the recess 14 by plating, and the interior of the recess 14 is filled with the plating layer 17 (FIG. 4g). After removing the photoresist 16, the surface of the flat substrate 11 is polished, and the plating layer 17 spreading on the photoresist 16 and the metal thin film 15 formed on the flat substrate 11 are removed, so that it is almost the same as the surface of the flat substrate 11. The plating layer 17 (including a part of the metal thin film 15) having a rough surface is exposed. On the other hand, the back surface of the flat substrate 11 is also polished to expose the plating layer 17. By polishing the front surface and the back surface of the flat substrate 11, the flat substrate 5 including the via electrode 9 can be formed (FIG. 4h). According to such a manufacturing method, since the concave portion 14 is formed in the via electrode formation scheduled region after the green sheet is sintered, the positional deviation caused by the sintering can be reduced (patent). Reference 1).

Thereafter, in accordance with a normal method, a flat circuit board can be formed by patterning a signal transmission line, a surface grounding electrode and the like on the surface of the flat substrate 5 and forming a back ground electrode on the back surface. Also, a Gunn diode oscillator can be formed by mounting a Gunn diode on a flat circuit board.
JP 2005-259943 A

  In the method for manufacturing a flat substrate previously proposed by the applicant of the present application, the concave portions are formed in the flat substrate after sintering, so that the variation in the gap between the via electrodes due to the shrinkage of the green sheet due to the sintering is reduced. However, the processing by the microblast method has a variation in the size of the recess of about ± 30 μm due to the size of the abrasive grains and the pressure variation during the grain injection, and the via electrode has a trapezoidal cross-sectional shape or a mortar shape. It will become. As a result, there is still a problem that the gap between the via electrodes still remains and the fluctuation of the oscillation frequency of the Gunn diode oscillator cannot be eliminated.

  An object of the present invention is to solve the above problems and to provide a flat circuit board having no variation in oscillation frequency when a Gunn diode is mounted on a flat circuit board, and a Gunn diode oscillator using the same.

  In order to achieve the above object, a flat circuit board according to claim 1 of the present application includes a first signal transmission line and a surface ground electrode on the front surface, a back surface ground electrode on the back surface, and the surface ground electrode and the back surface ground electrode on the side surface. 1 or 2 or more 2nd which equipped the 1st flat circuit board which mounts a Gunn diode on the surface, the 2nd signal transmission line on the surface, and the back ground electrode on the back surface And a connecting means for connecting the first signal transmission line and the second signal transmission line.

In the Gunn diode oscillator according to the second aspect of the present invention, the first signal transmission line and the surface ground electrode are connected to the front surface, the back surface ground electrode is connected to the back surface, and the surface ground electrode and the back surface ground electrode are connected to the side surface. A cathode of a Gunn diode is connected to the first signal transmission line and an anode electrode of the Gunn diode is connected to the surface ground electrode, or an anode of the Gunn diode is connected to the first signal transmission line. 1 or 2 or more provided with the 1st flat circuit board which connected the electrode and connected the cathode electrode of the said Gunn diode to the said surface ground electrode, the 2nd signal transmission line on the surface, and the back surface ground electrode on the back surface It is characterized by comprising a second flat circuit board and connection means for connecting the first signal transmission line and the second signal transmission line.

  The flat circuit board of the present invention has a structure in which the front surface ground electrode and the back surface ground electrode of the flat circuit board on which the Gunn diode is mounted are made conductive by a conductive film provided on the side surface of the flat circuit board without using via electrodes. . Since the dimension between the opposing side surfaces of the flat circuit board can be accurately processed to a desired dimension by an ordinary cutting method, the variation in the distance corresponding to the distance between the conventional via electrodes is reduced.

  When a Gunn diode is mounted on the flat circuit board of the present invention to form a Gunn diode oscillator, it is possible to form a Gunn diode oscillator with small variations in oscillation frequency.

  In the present invention, the flat circuit board includes a first flat circuit board on which the Gunn diode is mounted and a second flat circuit board on which a bias circuit, a resonance circuit, and the like are formed, and can be formed of different materials. . As a result, it is possible to configure a combination of a first flat circuit board, which desirably uses a flat board with excellent heat dissipation for improving characteristics, and a second flat circuit board, which may be a normal ceramic substrate, The amount of use of the relatively expensive first flat circuit board is reduced, and there is an advantage that the flat circuit board and the Gunn diode oscillator can be formed at low cost.

  In the flat circuit board of the present invention, a conductive film that connects the front surface ground electrode and the back surface ground electrode is formed on the side surface of the flat circuit board on which the Gunn diode is mounted. Equivalent) is reduced. As a result, when a Gunn diode is mounted on the flat circuit board of the present invention to form a Gunn diode oscillator, it is possible to form a Gunn diode oscillator with small variations in oscillation frequency. Examples of the present invention will be described below.

  FIG. 1 is an explanatory diagram of a first embodiment of the present invention. A flat circuit board (corresponding to a first flat circuit board) 2a mounted with a Gunn diode 1 has a signal transmission line (corresponding to a first signal transmission line) 6a on its surface, as shown in FIG. A surface ground electrode 7a is formed, and a back surface ground electrode 8a is formed on the back surface thereof. Unlike the conventional flat circuit board, there is no via electrode, and the surface ground electrode 7a and the back ground electrode 8a are electrically connected by the conductive film 18 made of a metal film or the like formed on the side surface of the flat board 5a. .

  The flat circuit board 2a on which the Gunn diode 1 is mounted is formed as follows. First, a material appropriately selected from diamond having good heat dissipation characteristics, ceramics such as AlN, SiC, or BeO is prepared. For example, the flat substrate 5a having a side of about 1 mm is cut by irradiation with excimer laser light. Form. Here, the processing method of irradiating and cutting with laser light generally has a processing accuracy of about ± 5 μm, and the variation in the distance between the opposing side surfaces of the flat substrate 5a is about ± 5 μm. It can be seen that the variation can be greatly suppressed as compared with the processing accuracy of about ± 30 μm by the conventional microblast method.

  Next, a conductive film 18 made of titanium, platinum, gold, or the like is deposited on a pair of opposite side surfaces of the flat substrate 5a by, for example, vapor deposition.

  Next, a conductive thin film such as titanium, platinum, or gold is formed on the surface of the flat substrate 5a, and a pair of surface ground electrodes 7a are formed on the surface on the side surface on which the conductive film 18 is deposited by a normal photolithography method. The signal transmission line 6a is formed between them. A back surface ground electrode 8a is formed on the back surface of the flat substrate 5a. By forming in this way, the flat circuit substrate 2a having a structure in which the front surface ground electrode 7a and the back surface ground electrode 8a are electrically connected by the conductive film 18 attached to the side surface of the flat substrate 5a is formed. The method of cutting the flat substrate 5a is not limited to the method of cutting by irradiating the laser beam described above, and a method with high processing accuracy can be adopted. By forming the dimension and thickness of one side of the flat circuit board 2a to the desired dimensions, the variation in dimension corresponding to the distance 10 between the conventional via electrodes can be extremely reduced. Thereafter, the Gunn diode 1 is mounted on the flat circuit board 2a using a normal flip chip bonding apparatus (FIG. 1a). The Gunn diode 1 has the structure described with reference to FIG. 4, and a cathode electrode (not shown) is connected to the signal transmission line 6a and an anode electrode is connected to the surface ground electrode 7a.

  On the other hand, as shown in FIG. 1 (b), a flat substrate 5b made of ceramic used for a normal flat substrate is prepared, and the portion where the flat circuit substrate 2a is inserted is cut and removed by irradiating an excimer laser, A through hole 19 is formed. The processing accuracy at this time is about 5 μm. Subsequently, the signal transmission line 6b (corresponding to the second signal transmission line) and the bias terminal 20 are patterned on the flat substrate 5b, and the flat circuit substrate 2b having the through holes 19 is formed. A circuit structure necessary as an oscillation circuit such as a bias circuit, a resonance circuit, and a matching circuit is formed on the surface of the flat circuit board 2b. A back surface ground electrode 8 is formed on the back surface of the flat circuit board 2b.

  Further, as shown in FIG. 1 (c), a transmission in which a flat substrate 5c made of ceramics used for a normal flat substrate is prepared, a metal thin film is formed on the surface of the flat substrate 5c, and bumps 21 are arranged on both ends of the metal thin film. The line connection element 22 is formed.

  Next, the flat circuit board 2a on which the Gunn diode 1 shown in FIG. 1A is mounted is disposed in the through hole 19 of the flat circuit board 2b, and the signal transmission lines 6a and 6b are connected by the transmission line connecting element 22. Thus, a Gunn diode oscillator can be formed (FIG. 1d). FIG. 1 (d) shows a structure in which the flat circuit boards 2a and 2b are placed on the ground casing 23. By applying a bias potential to the bias terminal 20 as shown, the Gunn diode oscillator It becomes.

  With such a structure, the interval 24 is determined by the dimensions of the opposing side surfaces of the flat substrate 5a. Here, since the dimension of the side surface is determined by the processing accuracy of the flat substrate 5a, in the method of cutting by irradiating the laser beam, the variation is about ± 5 μm.

  FIG. 2 is an explanatory diagram of the second embodiment of the present invention. In this embodiment, the flat circuit board (corresponding to the first flat circuit board) 2c on which the Gunn diode 1 is mounted is provided with a signal transmission line (first signal transmission line) on its surface as shown in FIG. 6c and the front surface ground electrode 7c are formed, and the back surface ground electrode 8c is formed on the back surface thereof. Unlike a conventional flat circuit board, the structure has no via electrode. Unlike the flat circuit board 2a described in the first embodiment, the conductive film 18 for conducting the front surface ground electrode 7c and the back surface ground electrode 8c is not provided.

  The flat circuit board 2c on which the Gunn diode 1 is mounted is formed as follows. First, a material appropriately selected from diamond having good heat dissipation characteristics, ceramics such as AlN, SiC, or BeO is prepared. For example, the flat substrate 5a having a side of about 1 mm is cut by irradiation with excimer laser light. Form. Here, the processing method of irradiating and cutting with a laser beam generally has a processing accuracy of about ± 5 μm, and the variation in the distance between the opposing side surfaces of the flat substrate 5c is about ± 5 μm. It can be seen that the variation can be greatly suppressed as compared with the processing accuracy of about ± 30 μm by the conventional microblast method.

  Next, a conductive thin film is deposited on the surface of the flat substrate 5c, and a pair of surface ground electrodes 7c and a signal transmission line 6c are formed between them by an ordinary photolithographic method. Further, a back surface ground electrode 8c is formed on the back surface of the flat substrate 5c. At this stage, the front surface ground electrode 7c and the back surface ground electrode 8c are electrically separated. The method of cutting the flat substrate 5c is not limited to the method of cutting by irradiating the laser beam described above, and a method with high processing accuracy can be adopted. By forming the dimension and thickness of one side of the flat circuit board 2c to a desired dimension, the variation in dimension corresponding to the distance 10 between the conventional via electrodes can be extremely reduced. Thereafter, the Gunn diode 1 is mounted on the flat circuit board 2c using a normal flip chip bonding apparatus (FIG. 2a). The Gunn diode 1 has the structure described in FIG. 4, and a cathode electrode (not shown) is connected to the signal transmission line 6c and an anode electrode is connected to the surface ground electrode 7c.

  Next, flat plate substrates 5d and 5e made of ceramics used for a normal flat plate substrate are prepared, and the signal transmission line 6d and the signal transmission line 6e are pattern-formed on the flat plate substrates 5d and 5e. A bias terminal 20 is also formed on the flat substrate 5d. A circuit structure necessary as an oscillation circuit, such as a bias circuit, a resonance circuit, and a matching circuit, is formed on the surfaces of the flat circuit boards 2d and 2e thus formed. Further, back ground electrodes 8d and 8e are formed on the back surfaces of the flat circuit boards 2d and 2e, respectively.

  The flat circuit boards 2c, 2d and 2e are placed on the ground housing 23 as shown in FIG. Thereafter, a conductive material such as silver paste is applied to the side surface of the flat circuit board 2c, and is cured by heating, thereby forming a conductive film 18a that electrically connects the front surface ground electrode 7c and the back surface ground electrode 8c.

  By connecting the signal transmission lines 6c and 6d and 6c and 6e with the gold wire 25, a Gunn diode oscillator as shown in FIG. 2B can be formed.

  By adopting such a structure, the interval 24 is determined by the dimensions of the opposing side surfaces of the flat substrate 5c. Here, since the dimension of the side surface is determined by the processing accuracy of the flat substrate 5c, in the method of cutting by irradiating the laser beam, the variation is about ± 5 μm.

  As mentioned above, although the Example of this invention was described, it cannot be overemphasized that this invention is not limited to these Examples. For example, the flat circuit board (2a, 2c) has been described as being disposed in combination with another flat circuit board (2b, 2d, and 2e) in a state where the Gunn diode 1 is mounted. It is also possible to mount a Gunn diode after placement. In the first embodiment, it is possible to connect with a gold wire or a gold ribbon instead of the transmission line connecting element 22, and also in the second embodiment, a connection with a gold ribbon or a transmission line connecting element instead of the gold wire. can do. Furthermore, in the second embodiment, the case where there are two flat circuit boards corresponding to the second flat circuit board has been described, but the number of flat circuit boards is not limited to this.

It is explanatory drawing of the 1st Example of this invention. It is explanatory drawing of the 2nd Example of this invention. It is a partial sectional view of a conventional Gunn diode oscillator. It is explanatory drawing of the manufacturing method of the conventional flat substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Gunn diode, 2; Flat circuit board, 3; Cathode electrode, 4; Anode electrode, 5; Flat board, 6: Signal transmission line, 7: Surface ground electrode, 8; ; Spacing, 11; flat substrate, 12; dry film, 13; fine abrasive, 14; recess, 15; metal thin film, 16; photoresist, 17; plating layer, 18; ; Bias terminal, 21; bump electrode, 22; transmission line connection element, 23; ground housing, 24; interval, 25: gold wire

Claims (2)

A first signal transmission line and a surface ground electrode on the surface, a back surface ground electrode on the back surface, a conductive film connecting the surface ground electrode and the back surface ground electrode on the side surface, and a Gunn diode mounted on the surface. 1 flat circuit board;
One or more second flat circuit boards having a second signal transmission line on the front surface and a back ground electrode on the back surface;
A flat circuit board comprising a connection means for connecting the first signal transmission line and the second signal transmission line. A first signal transmission line and a front surface ground electrode on the front surface, a back surface ground electrode on the back surface, a conductive film connecting the front surface ground electrode and the back surface ground electrode on the side surface, and a gun on the first signal transmission line A cathode electrode of a diode is connected and an anode electrode of the Gunn diode is connected to the surface ground electrode, or an anode electrode of the Gunn diode is connected to the first signal transmission line and the Gunn diode is connected to the surface ground electrode. A first flat circuit board to which a cathode electrode of
One or more second flat circuit boards having a second signal transmission line on the front surface and a back ground electrode on the back surface;
A Gunn diode oscillator comprising connection means for connecting the first signal transmission line and the second signal transmission line.

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