1. Field of the Invention
The present invention relates generally to a coaxial microstrip line transducer for use as, for example, a coaxial connector, and more particularly, to a coaxial microstrip line transducer comprising an inner conductor having a center conductor portion arranged in a recess portion opened upward and an outer conductor arranged apart from the center conductor portion.
2. Description of the Prior Art
A coaxial microstrip line transducer shown in FIGS. 12 to 15 has been conventionally known. FIG. 12 is a plan view illustrating a coaxial microstrip line transducer, FIGS. 13 and 14 are respectively a cross sectional view taken along a line V--V shown in FIG. 12 and a cross sectional view taken along a line VI--VI shown in FIG. 12, and FIG. 15 is a bottom view illustrating the coaxial microstrip line transducer.
In this coaxial microstrip line transducer, a cylindrical recess portion 71a opened upward is formed in a resin case 71 made of insulating resin. In the recess portion 71a are a center conductor portion 72 in a cylindrical shape made of a metal material and a first conductor portion 73 in the shape of a part of a cylindrical curved surface. A lower end of the center conductor portion 72 is integrated into a terminal portion 74 made of a metal material. The terminal portion 74 is so formed as to lead to a lower surface through a side surface of the resin case 71 in order to connect the microstrip line transducer to a connecting land (not shown) on a substrate. That is, the center conductor portion 72 and the terminal portion 74 constitute an inner conductor of the microstrip line transducer.
On the other hand, the first conductor portion 73 is connected to a second conductor portion 75. The second conductor portion 75 is so formed as to lead to the lower surface through the side surface of the resin case 71 in order to connect the microstrip line transducer to the connecting land (not shown) on the substrate. The first conductor portion 73 and the second conductor portion 75 constitute an outer conductor of the microstrip line transducer. In addition, embedded metal parts 76 are formed on the lower surface of the resin case 71 in order to increase stability and bond strength in a case where the microstrip line transducer is mounted on the substrate or the like.
The above described inner conductor and the above described outer conductor are respectively formed by working a metal plate or a metal wire in accordance with a working method such as press working. The above described coaxial microstrip line transducer is constructed by mounting the metal members on the resin case 71 which is a resin molded product.
In the above described microstrip line transducer, the outer conductor comprising the first conductor portion 73 and the second conductor portion 75 is incorporated into the resin case 71 and the second conductor portion 75 is folded along the lower surface of the resin case 71. However, such an assembly operation is very difficult because the resin case 71 is small. That is, the plane dimensions of the resin case 71 are small, for example, approximately 4 mm.times.4.5 mm, so that the operation which includes passing the outer conductor having a complicated shape from the inside of the recess portion 71a to the outer side surface of the resin case 71 and further pulling the same out to the lower surface of the resin case 71 is very difficult. Particularly, there is a strong demand for miniaturization of the microstrip line transducer, as with other electronic components. However, the smaller the dimensions of the microstrip line transducer are, the more difficult the above described assembly operation is. Consequently, the manufacturing processes are complicated, and the manufacturing cost is increased.
Furthermore, in the above described coaxial microstrip line transducer, the terminal portion 74 of the inner conductor, the second conductor portion 75 of the outer conductor, and the embedded metal parts 76 are arranged on the lower surface of the resin case 71, as shown in FIG. 15. The terminal portion 74, the second conductor portion 75, and the embedded metal parts 76 are soldered to a wiring pattern or the connecting land on the substrate, thereby to mount the microstrip line transducer on the substrate. However, the base areas of the terminal portion 74, the second conductor portion 75, and the embedded metal parts 76 are relatively small, so that sufficient soldering strength (mounting strength) cannot be obtained.
It has also been considered to increase the areas of parts, which are located on the lower surface of the resin case 71, of the terminal portion 74, the second conductor portion 75, and the embedded metal parts 76, thereby to increase the soldering strength. However, an attempt to increase the soldering areas causes a heavy load to be applied to the resin case 71 in folding the terminal portion 74 and the second conductor portion 75 along the resin case 71, resulting in the possibility of damaging the resin case 71. Consequently, the soldering areas of the terminal portion 74, the second conductor portion 75, and the embedded metal parts 76 cannot be made so large.
Additionally, as shown in FIG. 13, the inner conductor comprising the center conductor portion 72 and the terminal portion 74 is mounted on the resin case 71 by insert molding. However, the terminal portion 74 is folded along the side surface and the lower surface of the resin case 71 after the insert molding. Consequently, there is a limit on the amount in the thicknesses T.sub.1 and T.sub.2 (see FIG. 13) of bottom parts of the resin case 71 can be decreased, so that products are prevented from being reduced in height.