JP2017005450A - High frequency transmission equipment and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide high frequency transmission equipment of a simple structure, capable of suppressing a skin effect at a low cost, and a manufacturing method therefor.SOLUTION: High frequency transmission equipment 900 includes an insulating substrate 1 and a high-frequency signal transmission line 2. The transmission line 2 is disposed on one main surface 1a of the insulating substrate 1. The transmission line 2 includes a conductor 3 and low-resistance metal films 4. The low-resistance metal films 4 are disposed on a side face 3b and a top face 3a of the conductor 3. A low-resistance metal film 4 which covers the side face 3b of the conductor 3 is thicker than a low-resistance metal film 4 which covers the top face 3a of the conductor 3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a high-frequency transmission device and a method for manufacturing the same, and more particularly to a high-frequency transmission device having a transmission path with a conductor covered with a metal film and a method for manufacturing the same.

  A microstrip line, which is one of high-frequency signal transmission lines, has a small line loss of a conductor material constituting the microstrip line. Thereby, the transmission efficiency of the high frequency signal in a microstrip line is improved.

  However, when the frequency of a signal transmitted to the microstrip line is high, it is known that a phenomenon in which a signal passes through only a very surface layer of the microstrip line, called a skin effect or a skin effect, occurs. . If the skin effect occurs, the transmission loss of the microstrip line increases. Therefore, it is preferable that the surface of the microstrip line is plated with a conductive material having a small transmission loss. Specifically, a plating film such as gold or silver may be provided on the outermost surface of the microstrip line for the purpose of reducing the transmission loss and the purpose of improving the mountability and taking measures against contamination.

  As microstrip lines for mitigating the skin effect, for example, the following Japanese Patent Laid-Open No. 2002-299918 (Patent Document 1) and Japanese Patent Laid-Open No. 10-13112 (Patent Document 2) have been proposed. .

JP 2002-299918A JP-A-10-13112

  However, the strip conductor having the edge electrode as in Patent Document 1 and the multilayer electrode in which a plurality of dielectric layers and conductor layers are laminated on the side surface portion of the conductor as in Patent Document 2 have a special shape. The process is complicated and the manufacturing cost may increase.

  The present invention has been made in view of the above problems, and an object thereof is to provide a high-frequency transmission device having a simpler structure and capable of suppressing the skin effect at a low cost and a method for manufacturing the same. is there.

  The high-frequency transmission device according to the present embodiment includes an insulating substrate and a high-frequency signal transmission path. The transmission line is disposed on one main surface of the insulating substrate. The transmission line has a conductor and a low resistance metal film. The low resistance metal film is disposed on the side surface and the upper surface of the conductor. The low resistance metal film covering the side surface of the conductor is thicker than the low resistance metal film covering the upper surface of the conductor.

  In the method for manufacturing a high-frequency transmission device according to the present embodiment, an insulating substrate is first prepared, and a transmission path for a high-frequency signal is formed on one main surface of the insulating substrate. In the step of forming the transmission line, a conductor is first formed. A first low resistance metal film is formed on the side surface and the upper surface of the conductor. After the first low resistance metal film is formed, a second low resistance metal film is additionally formed on the first low resistance metal film covering the side surface of the conductor.

  According to the present invention, the propagation of a high-frequency signal that tends to concentrate on the outermost surface portion of the side surface of the conductor can be widely dispersed in the range of the thick low-resistance metal film by the thick low-resistance metal film covering the side surface of the conductor. Such a high-frequency transmission device can be easily formed by simply forming a second low-resistance metal film in addition to the first low-resistance metal film on the side surface of the conductor without requiring a complicated process. .

It is a schematic sectional drawing which shows collectively the structure of the high frequency transmission apparatus of Embodiment 1-6. 5 is a schematic cross-sectional view showing a first step of the method for manufacturing the high-frequency transmission device in Embodiment 1. FIG. 6 is a schematic cross-sectional view showing a second step of the method for manufacturing the high-frequency transmission device in Embodiment 1. FIG. 6 is a schematic cross-sectional view showing a third step of the method for manufacturing the high-frequency transmission device in Embodiment 1. FIG. 6 is a schematic cross-sectional view showing a fourth step of the method for manufacturing the high-frequency transmission device in Embodiment 1. FIG. 6 is a schematic cross-sectional view showing a fifth step of the method for manufacturing the high-frequency transmission device in Embodiment 1. FIG. 7 is a schematic cross-sectional view showing a sixth step of the method for manufacturing the high-frequency transmission device in Embodiment 1. FIG. FIG. 10 is a schematic cross sectional view showing a seventh step of the method for manufacturing the high frequency transmission device in the first embodiment. FIG. 9 is a schematic cross sectional view showing an eighth step of the method for manufacturing the high frequency transmission device in the first embodiment. It is a schematic sectional drawing which shows the 9th process of the manufacturing method of the high frequency transmission apparatus in Embodiment 1, and shows the structure of the high frequency transmission apparatus in Embodiment 1. 12 is a schematic cross-sectional view showing a first step of a method for manufacturing a high-frequency transmission device in Embodiment 2. FIG. 6 is a schematic cross-sectional view showing a second step of the method for manufacturing a high-frequency transmission device according to Embodiment 2 and showing the configuration of the high-frequency transmission device according to Embodiment 2. FIG. 10 is a schematic cross-sectional view showing a first step of a method for manufacturing a high-frequency transmission device in Embodiment 3. FIG. 12 is a schematic cross-sectional view showing a second step of the method for manufacturing the high-frequency transmission device in Embodiment 3. FIG. 12 is a schematic cross-sectional view showing a third step of the method for manufacturing the high-frequency transmission device in Embodiment 3. FIG. 12 is a schematic cross-sectional view showing a fourth step of the method for manufacturing the high-frequency transmission device in Embodiment 3. FIG. 12 is a schematic cross-sectional view showing a fifth step of the method for manufacturing the high-frequency transmission device in Embodiment 3. FIG. It is a schematic sectional drawing which shows the 6th process of the manufacturing method of the high frequency transmission apparatus in Embodiment 3, and shows the structure of the high frequency transmission apparatus in Embodiment 3. 10 is a schematic cross-sectional view showing a first step of a method for manufacturing a high-frequency transmission device in Embodiment 4. FIG. It is a schematic sectional drawing which shows the 2nd process of the manufacturing method of the high frequency transmission apparatus in Embodiment 4, and shows the structure of the high frequency transmission apparatus in Embodiment 4. 10 is a schematic cross-sectional view showing a first step of a method for manufacturing a high-frequency transmission device in Embodiment 5. FIG. 10 is a schematic cross-sectional view showing a second step of the method for manufacturing the high-frequency transmission device in Embodiment 5. FIG. 10 is a schematic cross-sectional view showing a third step of the method for manufacturing the high-frequency transmission device in Embodiment 5. FIG. 10 is a schematic cross-sectional view showing a fourth step of the method for manufacturing the high-frequency transmission device in Embodiment 5. FIG. FIG. 10 is a schematic cross sectional view showing a fifth step of the method for manufacturing the high frequency transmission device in the fifth embodiment. It is a schematic sectional drawing which shows the 6th process of the manufacturing method of the high frequency transmission apparatus in Embodiment 5, and shows the structure of the high frequency transmission apparatus in Embodiment 5. 12 is a schematic cross-sectional view showing a first step of a method for manufacturing a high-frequency transmission device in Embodiment 6. FIG. It is a schematic sectional drawing which shows the 2nd process of the manufacturing method of the high frequency transmission apparatus in Embodiment 6, and shows the structure of the high frequency transmission apparatus in Embodiment 6.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
First, the configuration of the high-frequency transmission device of this embodiment will be described with reference to FIG.

  With reference to FIG. 1, a high-frequency transmission device 900 of the present embodiment includes an insulating substrate 1 and a transmission path 2. The insulating substrate 1 has, for example, a rectangular flat plate shape having one main surface 1a and the other main surface 1b opposite to the main surface 1a. The transmission line 2 is disposed in at least a part of the insulating substrate 1 on, for example, one main surface 1a, and transmits a high-frequency signal. Specifically, the transmission line 2 is a microstrip line or the like having a long shape extending in the depth direction of the paper in FIG.

  The transmission line 2 has a center conductor 3 (conductor) and a low resistance metal film 4. The central conductor 3 is a member made of a conductive material that forms the center of the entire transmission path 2. Here, the uppermost surface of the central conductor 3 is defined as a central conductor upper surface 3a (the upper surface of the conductor), and the uppermost surfaces on the left and right sides of the central conductor 3 in FIG. 1 are defined as the central conductor side surface 3b (conductor side surface). The low-resistance metal film 4 is formed on the central conductor upper surface 3a and the central conductor side surface 3b, and also covers one main surface 1a of the insulating substrate 1 in a region near (around) the central conductor 3. Is formed. A back electrode 5 is formed on, for example, the other main surface 1b of the insulating substrate 1.

  The low resistance metal film 4 on the central conductor side surface 3b (covering the central conductor side surface 3b in FIG. 1) is thicker than the low resistance metal film 4 on the central conductor upper surface 3a (covering the central conductor upper surface 3a in FIG. 1). ing. That is, the low resistance metal film 4 (the thickness in the vertical direction in the figure) on the central conductor side surface 3b is thicker than the low resistance metal film 4 (the thickness in the horizontal direction in the figure) on the central conductor upper surface 3a.

  The center conductor 3 of the transmission line 2 is made of, for example, silver. The low-resistance metal film 4 is a metal film that has a smaller electrical resistance than the central conductor 3 and a small transmission loss of high-frequency signals. Specifically, the low resistance metal film 4 is any plating film selected from the group consisting of gold, silver, or copper, for example.

  Although not shown in FIG. 1, as will be described later, in the transmission line 2, a thin plating is formed between the central conductor 3 and the low-resistance metal film 4 (so as to cover the central conductor upper surface 3 a and the central conductor side surface 3 b). A film is preferably formed.

  The high-frequency transmission device 900 of FIG. 1 described above shows the components common to the high-frequency transmission devices in the embodiments described below. Hereinafter, the manufacturing method of the high frequency transmission device of the present embodiment will be described with reference to FIGS.

With reference to FIG. 2, first, an insulating substrate 1C as the insulating substrate 1 of FIG. 1 is prepared. Insulating substrate 1C is a ceramic substrate that contains, for example, 90 mass% or more of alumina (Al ₂ O ₃ ) and is fired at 1400 ° C. or higher and 1600 ° C. or lower. In addition to the above alumina, any one selected from the group consisting of titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), and magnesium oxide (MgO) is used as the ceramic material used for the insulating substrate 1C. Also good.

  Referring to FIG. 3, center conductor 3 is formed in a partial region on one main surface 1a of insulating substrate 1C. The center conductor 3 is a member solidified by baking a silver paste formed by, for example, a generally known screen printing method at, for example, 700 ° C. or more and 800 ° C. or less. For example, the center conductor 3 extends in the depth direction of FIG. ing. The central conductor 3 may be formed of any one selected from the group consisting of tungsten, molybdenum, and nickel, for example, in addition to the above silver.

  Referring to FIG. 4, back electrode 5 is formed on the other main surface 1b of insulating substrate 1C by a generally known suitable material and formation method. In FIG. 4, the back electrode 5 is formed on almost the entire surface of the other main surface 1b, but the back electrode 5 may be formed only on a part of the other main surface 1b. Further, the order in which the central conductor 3 and the back electrode 5 in FIG. 3 are formed is arbitrary.

  Referring to FIG. 5, electroless nickel phosphorous plating film 6 is formed by, for example, electroless plating so as to cover center conductor upper surface 3a and center conductor side surface 3b of center conductor 3. The electroless nickel phosphorus plating film 6 preferably has a thickness of 2 μm or more and 6 μm or less. When the electroless nickel phosphorous plating film 6 contains nickel, for example, nickel for reaction with the solder when soldering a functional component such as a chip component or a wiring to the surface of the completed high-frequency transmission device is provided. Can be supplied.

  Although not shown, an electroless palladium phosphorus plating film or an electroless palladium plating film may be further formed so as to cover the surface of the electroless nickel phosphorus plating film 6. In this case, the electroless palladium phosphorus plating film or the electroless palladium plating film preferably has a thickness of 0.1 μm or more and 0.6 μm or less.

  Next, a low-resistance metal made of gold, for example, by electroless plating so as to cover the electroless nickel phosphorus plating film 6 (or the above-mentioned electroless palladium phosphorus plating film or the like) on the center conductor upper surface 3a and the center conductor side surface 3b. A film 4 is formed. Thereby, the low resistance metal film 4 is formed on both the central conductor upper surface 3a and the central conductor side surface 3b. The low resistance metal film 4 is formed so as to cover almost the entire surface of the electroless nickel phosphorus plating film 6, and preferably has a thickness of about 0.05 μm, for example.

  Referring to FIG. 6, photosensitive material 8 is supplied by coating on one main surface 1a of insulating substrate 1C so as to cover low resistance metal film 4 described above. The photosensitive material 8 here is preferably a dry film resist as a photosensitive agent used in ordinary photolithography (exposure and development). Here, an example in which the negative photosensitive material 8 is used is shown, but the photosensitive material 8 to be used is not limited thereto, and for example, a positive photosensitive material 8 may be used. It is preferable that the photosensitive material 8 is supplied to almost the entire surface on one main surface 1a and the low-resistance metal film 4 by various methods such as a generally known spin coating method, dip coating method, and coating method.

  Referring to FIG. 7, mask 9 made of, for example, glass and having substantially the same (rectangular) planar shape and size as insulating substrate 1C is prepared. The mask 9 has a configuration in which the pattern of the light transmitting portion 9a and the light shielding portion 9b along the main surface is alternately repeated over the entire surface of the mask in plan view. The pattern of the light transmitting portion 9a or the light shielding portion 9b is made of a generally known metal material such as chromium. Here, it is assumed that the translucent part 9a is a part that transmits a light source described later, and the light shielding part 9b is a part that shields the light source.

  Using the mask 9, the photosensitive material 8 on the insulating substrate 1C is subjected to processing (exposure processing and development processing) using a normal photolithography technique. Specifically, first, the photosensitive material 8 and the photosensitive material 8 are mutually spaced apart from each other at a slight distance from the uppermost surface of the photosensitive material 8 using, for example, a generally known exposure machine capable of contact exposure, proximity exposure, or projection exposure. A mask 9 is set so as to overlap. However, the mask 9 may be superimposed so as to contact the photosensitive material 8. Then, the light source 10 is irradiated from above to below the mask 9. Thereby, in particular, the photosensitive material 8 just below the light transmitting portion 9a is exposed, but the photosensitive material 8 just below the light shielding portion 9b is not exposed.

  Here, a mask 9 is used in which a translucent portion 9a is formed so as to substantially coincide with the central conductor 3 and the low resistance metal film 4 formed above, and a light shielding portion 9b is formed in the other region. . As a result, the photosensitive material 8 is irradiated directly on the central conductor 3 and the low-resistance metal film 4.

  Moreover, as the light source 10, it is preferable to use one selected from the group consisting of an ultraviolet lamp having a broad wavelength, g-line, i-line, and krypton fluoride excimer laser.

  After exposure processing is performed with an appropriate exposure amount, development processing is performed. For the development processing, an alkaline developer such as calcium carbonate or caustic soda is used. As a result, the photosensitive material 8 has a region that is directly under the translucent portion 9a and irradiated with the light source 10 as a remaining portion 11a, and a region that is directly under the light-shielding portion 9b and not irradiated with the light source 10 is a non-remaining portion. 11b is at least partially removed. Thus, the photosensitive material 8 becomes the post-exposure paste 11 having the remaining portion 11a and the non-remaining portion 11b.

  Referring to FIG. 8, after the processing of the photoengraving technique is finished, the insulating substrate 1C including the post-exposure paste 11 is rinsed with pure water. Thereby, the non-remaining portion 11b is completely removed, and the remaining portion 11a is formed as a protective pattern 12 that covers the central conductor 3 and the low-resistance metal film 4 from above. And the drying process is made | formed with respect to the whole containing the protection pattern 12. FIG.

  Referring to FIG. 9, among the low-resistance metal films 4 formed in the process of FIG. 5, the side low-resistance metal film 4b (first low-resistance metal film) that is the portion on the side surface 3b of the central conductor is the most. An additional low-resistance metal film 4c (second low-resistance metal film) made of, for example, gold is additionally formed on the outer surface by electroless plating so as to cover the outer surface. On the other hand, among the low resistance metal film 4 formed in the process of FIG. 5, the upper low resistance metal film 4a, which is a portion on the upper surface 3a of the central conductor, is covered with the protective pattern 12, so that the additional low resistance metal film 4c is not formed.

  Here, for convenience of explanation, the upper low-resistance metal film 4a and the side low-resistance metal film 4b are distinguished from each other, but they are formed integrally as a unit.

  Since the additional low resistance metal film 4c is formed directly on the upper surface of the side low resistance metal film 4b, no other layer is formed between them. Therefore, if the side low resistance metal film 4b and the additional low resistance metal film 4c are both made of the same material (for example, gold) and formed by the same method (for example, electroless plating), the side low resistance metal film 4b is finally formed. And the additional low resistance metal film 4c is an integral thick metal film.

  Thus, the lateral low resistance metal film 4b is covered on the lateral low resistance metal film 4b as the first low resistance metal film previously formed by, for example, electroless plating in the step of FIG. Thus, an additional low resistance metal film 4c as a second low resistance metal film is additionally formed. The upper low-resistance metal film 4a, the side low-resistance metal film 4b, and the additional low-resistance metal film 4c are combined to form the low-resistance metal film 4.

  The sum of the thickness of the additional low-resistance metal film 4c (related to the horizontal direction in FIG. 9) and the thickness of the side low-resistance metal film 4b (related to the horizontal direction of FIG. 9) should be at least 0.2 μm or more. preferable. In this way, the absolute value of the passage loss per 1 mm length in the signal flow direction of the transmission path 2 can be reduced (0.035 dB or less). Further, as shown in Table 1 below, the total thickness of the side low resistance metal film 4b and the additional low resistance metal film 4c is more preferably 0.4 μm or more, and further preferably 5 μm or more. For example, the absolute value of the passage loss per 1 mm length in the signal flow direction of the transmission path 2 can be further reduced.

  As a result, the transmission line 2 having the central conductor 3, the electroless nickel phosphorus plating film 6, and the low resistance metal film 4 is formed.

  Referring to FIG. 10, protective pattern 12 is removed using a generally known plasma ashing method or using a generally known NMP thinner, a solvent such as acetone or toluene. Thereby, like the high-frequency transmission device 900 of FIG. 1 (corresponding to the high-frequency transmission device 900), the central conductor 3 and the low-resistance metal film 4 (electroless) are formed on one main surface 1a of the insulating substrate 1C. A high-frequency transmission device 100 is formed in which a high-frequency signal transmission path 2 having a nickel phosphorous plating film 6 is formed.

  The upper low resistance metal film 4a, the side low resistance metal film 4b, and the additional low resistance metal film 4c constituting the low resistance metal film 4 are preferably all formed by electroless plating. However, for example, the upper low resistance metal film 4a and the side low resistance metal film 4b formed in the process of FIG. 5 are formed by electrolytic plating, and only the additional low resistance metal film 4c formed in the process of FIG. It may be formed by electrolytic plating. In any case, in the present embodiment, at least a part of the low resistance metal film 4 is a plating film formed by electroless plating.

  In the above, the upper low resistance metal film 4a, the side low resistance metal film 4b, and the additional low resistance metal film 4c constituting the low resistance metal film 4 are all gold plating films as an example, but instead of gold, for example, A silver or copper plating film may be formed.

Next, the function and effect of the present embodiment will be described while explaining the problems of the comparative example.
Basically, in a high-frequency transmission device, in order to suppress the skin effect, the surface of a transmission line such as a microstrip line is plated with a conductor such as gold or silver with a small transmission loss.

  Here, in the configuration in which the transmission path is formed on the insulating substrate, the current on the lower surface side in contact with the insulating substrate of the transmission path and the region on the left and right side surfaces of the transmission path are larger than those in other areas. It is known that the density increases. For this reason, for example, a gold plating film on the side surface of the center conductor of the transmission line is formed thicker than, for example, a gold plating film on the upper surface of the center conductor of the transmission path, thereby reducing transmission loss and improving transmission characteristics. It is thought that you can. This is because the high-frequency signal current, which tends to concentrate on the outermost edge of the transmission line, is within a wide area corresponding to the thickness of the gold plating film formed thicker (that is, to include the area closer to the center side of the central conductor). This is because the current density at the outermost edge portion of the transmission line can be reduced. If the current density at the outermost edge of the transmission line on the side surface side of the transmission line that tends to increase the current density can be reduced in this way, transmission loss due to current flowing through the outermost edge of the transmission line is reduced. Can be made.

  However, when the plating film is simultaneously formed on both the central conductor upper surface and the central conductor side surface of the central conductor constituting the transmission line such as the microstrip line as in the present embodiment, the upper surface of the central conductor and the side surface of the central conductor are formed. The thickness of the plating film is almost equal. This is because the plating film generally grows in a creeping manner.

  Therefore, if a thick gold plating film is to be formed on the side surface of the central conductor, a thick gold plating film is necessarily formed on the upper surface of the central conductor. However, since noble metals such as gold and silver are expensive, if a thick gold plating film is formed on the upper surface of the center conductor, the manufacturing cost may increase.

  In addition, if a thick gold plating film or the like is formed on the upper surface of the central conductor, for example, when a solder component is mounted on the upper surface of the central conductor, the adhesion of the soldering decreases due to the gold melting into the solder. A malfunction such as doing Further, if the gold plating film on the upper surface of the central conductor becomes excessively thick, there may be a disadvantage that a wiring interval with the central conductor (including a transmission path) when a fine pattern is formed around the gold plating film is limited.

  Therefore, in the present embodiment, the transmission line 2 first includes an upper low resistance metal film 4a and a side low resistance metal film 4b formed so as to simultaneously cover both the central conductor upper surface 3a and the central conductor side surface 3b, and thereafter An additional low resistance metal film 4c formed to cover the side low resistance metal film 4b is additionally provided. As described above, since the upper low-resistance metal film 4a and the side low-resistance metal film 4b are substantially equal in thickness, the low-resistance metal film 4 covering the central conductor side surface 3b by the thickness of the additional low-resistance metal film 4c. Is thicker than the low resistance metal film 4 covering the central conductor upper surface 3a.

  In other words, on the upper surface of the central conductor 3, only the upper low-resistance metal film 4a that is initially formed is formed, and after it is formed, an additional plating film is formed by being covered with the protective pattern 12. Never happen. On the upper surface of the central conductor 3, only an upper low resistance metal film 4a of about 0.05 μm, which is much thinner than that formed by flash plating, for example, is formed. Therefore, the occurrence of the above-mentioned problems and the like assumed when the low-resistance metal film 4 on the upper surface of the center conductor 3 is formed excessively thick is suppressed, and the thick low-resistance metal film 4 on the side surface of the center conductor 3 is used. Transmission loss can be reduced.

  In the present embodiment, after the step of forming the first low-resistance metal film on the normal center conductor upper surface 3a and the center conductor side surface 3b, an additional second low-resistance metal film is simply formed. A low resistance metal film 4 on the side surface of the central conductor 3 can be formed. That is, it is not necessary to form a transmission line having a complicated shape that protrudes in the thickness (height) direction from the other region on the side surface side of the central conductor, which can be considered as a first comparative example. Further, for example, the second embodiment of the present embodiment can be compared with the case where a configuration in which both a dielectric layer and a conductor layer are laminated on the side surface of the central conductor 3 considered as a second comparative example is formed. The manufacturing method in which only the low resistance metal film is additionally formed is simple. Therefore, it is possible to provide the high-frequency transmission device 100 that can easily reduce the transmission loss without increasing the number of processes excessively.

  In addition, in this embodiment, the low-resistance metal film 4 is formed by electroless plating, so that the low-resistance metal film 4 has low resistance even in a portion other than a portion that is electrically connected to a terminal electrode (not shown) formed on the insulating substrate 1C. A metal film 4 can be formed. For this reason, the low-resistance metal film 4 can be formed in any location by electroless plating.

  Further, by using the insulating substrate 1C which is a ceramic substrate, the insulating substrate 1C having high strength and low dielectric loss can be used.

  As described above, the central conductor 3 is made of, for example, silver, whereas the low-resistance metal film 4 formed on the side surface of the central conductor 3 may be formed of a silver plating film. However, the silver paste constituting the central conductor 3 contains not only pure silver but also a mixture of dielectric materials constituting the insulating substrate 1 and a lot of porous materials. For this reason, the electrical properties of the central conductor 3 are different from those of pure silver crystals. On the other hand, the low-resistance metal film 4 formed of a silver plating film exhibits electrical characteristics similar to those of pure silver crystals. That is, even if both the central conductor 3 and the low-resistance metal film 4 are made of silver, there is a large difference in electrical characteristics between them, and the low-resistance metal film 4 has a lower electrical resistance than the central conductor 3. Therefore, the transmission loss of the high frequency signal is reduced. Therefore, it can be said that there is an actual benefit in forming the silver low-resistance metal film 4 on the side surface of the silver central conductor 3 or the like.

(Embodiment 2)
This embodiment is slightly different from the first embodiment in the method of forming the additional low resistance metal film, but the other points are basically the same as in the first embodiment. For this reason, the same code | symbol is attached | subjected about the element same as Embodiment 1, and the description is not repeated. Hereinafter, the manufacturing method of the high frequency transmission apparatus of this Embodiment is demonstrated using FIGS. 11-12.

  Referring to FIG. 11, after the same processing as the steps of FIGS. 2 to 8 of the first embodiment is performed, the center conductor side surface 3 b is covered in the low resistance metal film 4 formed in the step of FIG. 5. An additional low resistance metal film 4d (first film) made of, for example, gold is formed on the outermost surface of the side low resistance metal film 4b (first low resistance metal film), which is a portion, by electrolytic plating so as to cover the surface. 2 low-resistance metal film) is additionally formed. The additional low resistance metal film 4d is basically the same as the additional low resistance metal film 4c of the first embodiment except that the additional low resistance metal film 4d is formed by electrolytic plating instead of electroless plating. That is, the upper low-resistance metal film 4a, the side low-resistance metal film 4b, and the additional low-resistance metal film 4d are combined to form the low-resistance metal film 4.

  Referring to FIG. 12, the protective pattern 12 is removed as in the step of FIG. Thereby, like the high-frequency transmission device 900 of FIG. 1 (corresponding to the high-frequency transmission device 900), the central conductor 3 and the low-resistance metal film 4 (electroless) are formed on one main surface 1a of the insulating substrate 1C. A high-frequency transmission device 200 is formed, in which the transmission path 2 having the nickel phosphorous plating film 6 is formed.

  The upper low resistance metal film 4a and the side low resistance metal film 4b may be formed by electroless plating or may be formed by electrolytic plating. In any case, since at least the additional low resistance metal film 4d is formed by electrolytic plating in the present embodiment, at least a part of the low resistance metal film 4 is a plating film formed by electrolytic plating.

  Next, the effect of this Embodiment is demonstrated. However, since the operational effects of the present embodiment are basically the same as the operational effects of the first embodiment, the description of the same operational effects is omitted.

  In the present embodiment, the additional low resistance metal film 4d is formed by electrolytic plating. For this reason, it can form into a film at high speed compared with electroless plating.

  The additional low resistance metal film 4c formed by electroless plating as in the first embodiment and the additional low resistance metal film 4d formed by electrolytic plating as in the present embodiment are analyzed as follows. Etc. can be determined. First, electrolytic plating is characterized by a large crystal grain size compared to electroless plating. In addition, when forming a plating film by electrolytic plating, it is necessary to contact the electrode terminal with the area where the plating film is to be formed. can do.

(Embodiment 3)
In the present embodiment, the material of the insulating substrate is slightly different from that in the first embodiment, but the other points are basically the same as those in the first embodiment. For this reason, the same code | symbol is attached | subjected about the element same as Embodiment 1, and the description is not repeated. Hereinafter, a method for manufacturing the high-frequency transmission device of the present embodiment will be described with reference to FIGS.

  Referring to FIGS. 13 to 18, these are basically the same processes as those in FIGS. 5 to 10 of the first embodiment, and therefore detailed description will not be repeated. However, here, as the insulating substrate 1, an insulating substrate 1L is used instead of the insulating substrate 1C of the first embodiment.

  The insulating substrate 1L has one main surface 1a and the other main surface 1b, similarly to the insulating substrate 1C. The insulating substrate 1L contains alumina and glass of about 50% by mass or more. The glass here is, for example, borate glass or silicate glass. An insulating substrate 1L as a so-called low-temperature fired ceramic substrate is formed by firing those containing these materials at a temperature of 700 ° C. or higher and 900 ° C. or lower, which is lower than that of the insulating substrate 1C.

  Since the present embodiment has basically the same configuration as that of the first embodiment, the low-resistance metal film 4 is formed by the upper low-resistance metal film 4a, the side low-resistance metal film 4b, and electroless plating. The additional low resistance metal film 4c is formed.

  As described above, as with the high-frequency transmission device 900 of FIG. 1 (corresponding to the high-frequency transmission device 900), the central conductor 3 and the low-resistance metal film 4 (electroless) are formed on one main surface 1a of the insulating substrate 1L. A high-frequency transmission device 300 is formed in which the transmission path 2 having the nickel phosphorous plating film 6) is formed.

  Next, the function and effect of this embodiment will be described. However, since the operational effects of the present embodiment are basically the same as the operational effects of the first embodiment, the description of the same operational effects is omitted.

  In the present embodiment, an insulating substrate 1L as a low-temperature fired ceramic substrate is used as the insulating substrate 1. Thus, when a conductive via hole or the like is formed inside the insulating substrate 1L, for example, the conductive layer in the via hole is formed of a conductor such as gold, silver, or copper having a small electrical resistance and a small conductor loss. Can do. That is, in the above case, the insulating substrate 1C according to Embodiment 1 in which the conductive layer in the via hole needs to be formed using a conductor having a relatively high electrical resistance and a relatively large conductor loss, such as tungsten, molybdenum, or nickel. Compared with the case where it is, the selection width of the conductive layer in the via hole can be expanded, and the conductor loss there can be reduced.

(Embodiment 4)
Referring to the manufacturing method of the present embodiment in FIGS. 19 to 20, in this embodiment, instead of forming additional low-resistance metal film 4c by electroless plating, electrolysis is performed in the same manner as in the second embodiment. It differs from the third embodiment only in that the additional low resistance metal film 4d is formed by plating. However, the other points are basically the same as those in the third embodiment. For this reason, the same code | symbol is attached | subjected about the element same as Embodiment 3, and the description is not repeated.

  Referring to FIG. 20, also in the present embodiment, a central conductor is formed on one main surface 1a of insulating substrate 1L in the same manner as high frequency transmission device 900 in FIG. 1 (corresponding to high frequency transmission device 900). 3 and a low-resistance metal film 4 (with an electroless nickel phosphorous plating film 6), a high-frequency transmission device 400 is formed.

  As in the present embodiment, a high-frequency transmission device 400 having a combination of the insulating substrate 1L and the additional low-resistance metal film 4d may be used, and the same operational effects as in the first to third embodiments can be achieved. .

(Embodiment 5)
In the present embodiment, the material of the insulating substrate is slightly different from that in the first embodiment, but the other points are basically the same as those in the first embodiment. For this reason, the same code | symbol is attached | subjected about the element same as Embodiment 1, and the description is not repeated. Hereinafter, a method for manufacturing the high-frequency transmission device of the present embodiment will be described with reference to FIGS.

  Referring to FIGS. 21 to 26, these are basically the same processes as the steps of FIGS. 5 to 10 of the first embodiment, and therefore detailed description will not be repeated. However, here, the insulating substrate 1F is used as the insulating substrate 1 instead of the insulating substrate 1C of the first embodiment.

  The insulating substrate 1F has one main surface 1a and the other main surface 1b, similarly to the insulating substrate 1C. Insulating substrate 1F is a substrate made of ferrite, for example, fired at 1300 ° C. or higher and 1800 ° C. or lower.

  Since the present embodiment has basically the same configuration as that of the first embodiment, the low-resistance metal film 4 is formed by the upper low-resistance metal film 4a, the side low-resistance metal film 4b, and electroless plating. The additional low resistance metal film 4c is formed.

  As described above, similarly to the high-frequency transmission device 900 of FIG. 1 (corresponding to the high-frequency transmission device 900), the central conductor 3 and the low-resistance metal film 4 (electroless) are formed on one main surface 1a of the insulating substrate 1F. A high-frequency transmission device 500 is formed in which the transmission path 2 having the nickel phosphorus plating film 6) is formed.

  Next, the function and effect of this embodiment will be described. However, since the operational effects of the present embodiment are basically the same as the operational effects of the first embodiment, the description of the same operational effects is omitted.

  In the present embodiment, an insulating substrate 1F made of ferrite is used as the insulating substrate 1. Since ferrite is a magnetic substance, the propagation direction of the high-frequency signal flowing through the transmission path 2 can be changed by using this ferrite while extremely reducing transmission loss.

(Embodiment 6)
Referring to the manufacturing method of the present embodiment shown in FIGS. 27 to 28, in this embodiment, instead of forming additional low-resistance metal film 4c by electroless plating, electrolysis is performed in the same manner as in the second embodiment. It differs from the fifth embodiment only in that the additional low resistance metal film 4d is formed by plating. However, the other points are basically the same as in the fifth embodiment. For this reason, the same elements as those of the fifth embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

  Referring to FIG. 28, also in the present embodiment, the central conductor is formed on one main surface 1a of insulating substrate 1F in the same manner as high frequency transmission apparatus 900 in FIG. 1 (corresponding to high frequency transmission apparatus 900). 3 and the low-resistance metal film 4 (with the electroless nickel phosphorous plating film 6) are formed, the high-frequency transmission device 600 is formed.

  As in the present embodiment, a high-frequency transmission device 600 having a combination of the insulating substrate 1F and the additional low-resistance metal film 4d may be used, and the same operational effects as in the first to fifth embodiments can be achieved. .

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1, 1C, 1F, 1L Insulating substrate, 1a One main surface, 1b The other main surface, 2 Transmission path, 3 Center conductor, 3a Center conductor top surface, 3b Center conductor side surface, 4 Low resistance metal film, 4a Upper low resistance Metal film, 4b Side low resistance metal film, 4c, 4d Additional low resistance metal film, 5 Back electrode, 6 Electroless nickel phosphorus plating film, 8 Photosensitive material, 9 Mask, 9a Translucent part, 9b Light shielding part, 10 Light source, 11 Post-exposure paste, 11a Remaining part, 11b Non-remaining part, 12 Protection pattern, 100, 200, 300, 400, 500, 600, 900 High-frequency transmission device.

Claims (7)

An insulating substrate;
A high-frequency signal transmission path disposed on one main surface of the insulating substrate;
The transmission path is
Conductors,
A low-resistance metal film disposed on the side surface and the upper surface of the conductor,
The low-resistance metal film on the side surface of the conductor is thicker than the low-resistance metal film on the upper surface of the conductor.   The high-frequency transmission device according to claim 1, wherein at least a part of the low-resistance metal film on a side surface of the conductor is a plating film formed by electroless plating.   The high-frequency transmission device according to claim 1, wherein at least a part of the low-resistance metal film on the side surface of the conductor is a plating film formed by electrolytic plating.   The high-frequency transmission device according to claim 1, wherein the insulating substrate is a ceramic substrate. Preparing an insulating substrate; and
Forming a high-frequency signal transmission path on one main surface of the insulating substrate,
The step of forming the transmission path includes:
Forming a conductor;
Forming a first low resistance metal film on a side surface and an upper surface of the conductor;
And a step of additionally forming a second low-resistance metal film on the first low-resistance metal film on the side surface of the conductor after the step of forming the first low-resistance metal film. A method for manufacturing a transmission device.   The method for manufacturing a high-frequency transmission device according to claim 5, wherein the second low-resistance metal film formed in the additional forming step is a plating film formed by electroless plating.   The method for manufacturing a high-frequency transmission device according to claim 5, wherein the second low-resistance metal film formed in the additional forming step is a plating film formed by electrolytic plating.

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