JPS6161725B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a microwave transmission line, particularly a microwave transmission line having a triplate structure.

Waveguides, coaxial lines, etc. are usually used as microwave transmission lines, but planar circuits with circuits formed on dielectric substrates are also increasingly being used to make devices smaller and lighter. I'm getting used to it. These planar circuits include coplanar lines, microstrip lines, and triplate lines. Hereinafter, the triplate line to which the present invention is applied will be explained.

FIG. 1 is a perspective view showing the configuration of a general triplate line, where 1 is a center conductor, 2 and 3 are dielectric plates sandwiching the center conductor 1, and 4 and 5 are outer sides of dielectric plates 2 and 3, respectively. A ground conductor glued to the surface. Since the triplate line has a structure in which the center conductor 1 is surrounded by the ground conductors 4 and 5, it has less radiation loss than other planar circuits such as microstrip lines. A microwave transmission line can be constructed.

Figure 2 is a perspective view showing the conventional manufacturing method of this triplate line. First, a plate made of a dielectric plate such as Teflon with low high frequency loss and copper foil pasted on both sides is used. The copper foil is left as it is to serve as the ground conductor 4, and the copper foil on the other side is etched, leaving a required portion, to form a first substrate having the center conductor 1 on the dielectric plate 2.
Alternatively, you can use a dielectric plate with copper foil pasted on only one side, or remove all the copper foil on one side of a dielectric plate with copper foil on both sides as described above, and connect the dielectric plate 3 and the ground conductor. 5 is formed. Thereafter, these first and second substrates were stacked in the direction shown in FIG. 2 in the direction of the arrow to form a triplate line as shown in FIG. 1.
There are two methods for overlapping and fixing the two substrates shown in Fig. 2, one is to stick them together with adhesive, and the other is to sandwich the two ground conductors 4 and 5 between the outer surfaces with metal members, but usually there is a simple method. Therefore, the latter method is used.

In addition to the above-mentioned Teflon, alumina, quartz, saphire, etc. are often used as dielectric materials for microwave transmission lines, but since these materials are hard and brittle, we will focus on these materials here.
It was difficult to use for a tri-plate line and for the above structure in which both substrates are sandwiched between metal members because it is easy to break. In particular, alumina is relatively easy to metallize, has relatively high mechanical strength, and is inexpensive, so it is most widely used for microstrip lines and the like. Transmission lines made of alumina can withstand high temperatures and allow semiconductor devices to be attached directly to the lines, and are often used as substrates for so-called microwave ICs. As described above, alumina has various advantages as a dielectric material for transmission lines and is excellent, so it is desirable to use it for triplate lines as well.

The present invention has been made in view of the above points, and an object of the present invention is to provide a novel method for manufacturing a triplate type microwave transmission line using alumina as a dielectric.

FIG. 3 is a sectional view showing the main stages of an embodiment of the present invention. First, as shown in FIG. 3a, an unfired alumina sheet (green sheet) 3 is prepared, and as shown in FIG. As shown in FIG. 2, a ground conductor 5 is printed on one surface using a metal paste containing tungsten as a main component, for example. Next, as shown in FIG. 3c, the center conductor 1 is printed on the other side of the green sheet 3 using the same metal paste. Then, as shown in FIG. 3d, a separately prepared green sheet 2 is pressed and attached to the center conductor 1 side, and then a third
A ground conductor 4 is printed thereon with a metal paste similar to that described above, as shown in Figure e. Thereafter, by firing in a hydrogen atmosphere, a triplate-shaped microwave transmission line as shown in FIG. 1 is obtained.

In the above embodiment, the grounding conductors 4 and 5 are provided over the entire surface, but it is not necessary to provide them over the entire surface, but a width at least three times the width of the center conductor 1 is provided at the portion facing the center conductor. What is necessary is just to provide it so that it has. Further, the ground conductors 4 and 5 may be plated if necessary. Although the conductor layer has been described as being formed using a metal paste containing tungsten as a main component, it is of course possible to use a paste of another metal.

It is also possible to make a hole in the ground conductor 5 and alumina 3 in a part of the line, expose the center conductor 1, and attach elements such as semiconductor elements, resistors, and capacitors to form a circuit with complex functions as a whole. can.

As described above, in the manufacturing method according to the present invention, a multilayer structure of alumina ceramic is created using a thick film printing technique, and thereby a triplate-shaped microwave transmission line is formed. There are advantages.

(b) Since printing techniques are used, mass production is possible and costs can be reduced.

(b) Since the metallized layer and the alumina layer are fired simultaneously, the bond between them is strong and reliability can be improved.

(c) Since the two green sheet layers are pressed together and fired at the same time, the alumina becomes completely integrated, and there is no need to sandwich the alumina between metal members as in the past, allowing the alumina to be safely used as a dielectric.

(d) Therefore, since the microwave transmission line obtained in this way uses alumina, it can withstand high temperatures, is mechanically strong, and has little thermal expansion, improving the performance of the entire microwave circuit. , can contribute to improving reliability.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the configuration of a general triplate line, Fig. 2 is a perspective view showing a conventional manufacturing method thereof, and Figs. 3 a to e show the state of an embodiment of the present invention at each stage. FIG. In the figure, 1 is the center conductor, 2 is the second alumina sheet, 3 is the first alumina sheet, and 4 is the second alumina sheet.
, and 5 is the first ground conductor. In addition,
The same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A first step of printing and forming a first ground conductor using metal paste on the first surface of the first unfired alumina sheet, and a center conductor using metal paste on the second surface. a second step of press-welding a second unsintered alumina sheet to the second surface of the first unsintered alumina sheet so that the first surface is in contact with the second unsintered alumina sheet; The third step is to print and form a second ground conductor using metal paste on the second surface of the sheet, and the multilayer structure obtained through each of the above steps is heated in a required atmosphere to form each of the above-mentioned unsintered alumina. A method for manufacturing a microwave transmission line having a triplate structure, comprising a fourth step of simultaneously firing the metal paste and each conductor made of the metal paste.