JPH04170202A - Planer dielectric filter - Google Patents

Abstract

PURPOSE:To improve the mass-productivity by using an exposed ground terminal for both ends of a resonator terminal so as to attain miniaturization and reduce trimming amount. CONSTITUTION:Full face metallize conductors 16, 17 are formed to a couple of side end faces and one major face of dielectric bases 11, 12. Resonance electrodes 13a-13e and input output electrodes 15a, 15b and input/output electrodes 15a, 15b required for forming the filter are formed by sheet metal pressing or photo etching to a metallic plate 20 together with parts to support them. Other major sides of the bases 11, 12 are opposed to each other, the metallic plate 20 is inserted between them and they are stacked and the electric connection and mechanical fixing are implemented by brazing side end faces of the metallic plate 20. Then the undesired metallic plate is cut off by pressing as shown in broken lines with respect to a press guide hole 14 as a reference to obtain the filter product. Captions 18a-18d are electric ground terminals and the electrodes 15a, 15b are input/output hot terminals. Thus, the trimming amount is reduced, the mass-productivity is improved and the miniaturization is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION - (Technical Field to which the Invention Pertains) The present invention relates to a planar dielectric filter that is small and can be mass-produced for use in microwave band communication equipment.

(Prior Art) As one type of microwave band filter, there is a small and lightweight planar dielectric filter using a slip conductor. FIG. 6 is a partially cutaway perspective view of a conventional planar dielectric filter, and FIG. 7 is a perspective view of a filter with external connection terminals.

As shown in FIG. 6, in a conventional planar dielectric filter, wavelength strip conductors 3 and 4 with one end shorted and the other end open are arranged in parallel on one main surface of one dielectric substrate l by metallization or etching. Input/output terminals 5 and 6
is provided. A ground conductor 7 is provided on the other main surface of this dielectric substrate 1, and another dielectric substrate 2
The ground conductor 8 is provided on one main surface and the other surface is superimposed as shown in the figure and fused and fixed with glass or the like, or mechanically fixed.

Such conventional planar dielectric filters have the following drawbacks.

(1) When the strip conductors 3 and 4 are formed by a metallization method in which silver paste or copper paste is printed and fired,
The thickness of the cross section of the conductor is not constant as shown in FIG. 5, and as a result, a gap is created between the dielectric substrate 2 and the strip conductors 3 and 4, which face each other, and the resonance frequency varies considerably. For this reason, extensive trimming is required in order to obtain the required characteristics as a filter, making it difficult to effectively mass-produce the filter.

(2) If the strip conductors 3 and 4 are formed by plating the entire surface of the dielectric substrate 1゜2 and then forming the required conductor pattern by etching, the thickness of the conductor should be uniform as in the metallization method. It will never go away. However, the dielectric substrate 1. When plating metal on 2, in order to increase the adhesion strength, electroless plating is first performed on a metal with relatively high electrical resistance, such as nickel or chromium, as a base.
After that, metals with low electrical resistance such as copper, gold, and silver are applied by electrolytic plating.

Therefore, the conductor resistance on the side of the substrate where the high frequency current density is high increases, and the loss increases compared to the metallization method. In our trial production results, it was confirmed that the plating/etching method lowers the Q by 10 to 20% at I GHz compared to the metallization method. For this reason, it has been difficult to use it as a filter with low loss.

(3) When used as a filter in wireless equipment, input/output leader lines are required. Conventionally, as shown in FIG. 7(A), a thin plate was inserted between dielectric substrates 1 and 2 to serve as a leader line 9. However, in this method, the thickness of the dielectric substrate l of the leader wire 9 is
and 2 (because a gap is created, the effective permittivity decreases and becomes an obstacle to miniaturization.As a countermeasure to this problem, as shown in the same figure (B), a combination of dielectric substrates with different dimensions is used. There are two methods: exposing the leader wire 10, or using a cutting die when manufacturing the dielectric substrate, and the initial investment is large;
Since a space is required to electrically and mechanically connect the lead wire 10 to the dielectric substrate 1, there is a problem in that it becomes an obstacle to miniaturization.

The above can be summarized as follows.

(1) Formation of conductor by metallization method - Regardless of conductor thickness -
Large amount of trimming = Problems with mass production (2) Conductor formation by plating and etching - Increase in conductor loss = Deterioration of characteristics (3) External lead wire = Decrease in effective dielectric constant = Connection space required = Large shape (invention (Problems to be Solved) The purpose of the present invention is to solve the problems of the conductor forming method and external leader wires in the conventional examples mentioned above, and to create a compact, economical flat surface with less trimming and excellent mass productivity. An object of the present invention is to provide a shaped dielectric filter.

(Means to try to solve the problem) FIG. 1 is an exploded perspective view showing the configuration of an embodiment of the present invention.

A full-surface metallized conductor 16.17 is formed on one main surface and a pair of side end surfaces of the dielectric substrate 11.12. Resonant electrodes 13a to 13 necessary to form a filter
e and the input/output electrodes 15a, 15b, together with the parts that hold them, are made on a single metal plate 20 by sheet metal pressing or photo etching.

The other main surfaces of the substrates 11 and 12 are made to face each other, the metal plate 20 is sandwiched between them, and the side end surface electrodes 16, 17 and the metal plate 2 are stacked.
Electrical connection and mechanical fixation are performed by brazing the side end surfaces of 0. Next, using the press guide hole 14 as a reference, the unnecessary metal/plate portion is press-worked to cut the portion indicated by the broken line to obtain a finished filter product as shown in FIG. 18
A to 18d are electrically ground terminals, and 15a and 15
b becomes a hot terminal for input/output. Ground terminals 18a and 2
The metal plates between 8a maintain a stable clamping and fixing state and also play the role of an electromagnetic shield.

If a terminal shape as a surface mount component is required, the terminal may be further formed into the shape shown in the side view of FIG. 3 after this.

Since a single metal plate 20 is used as the conductor, the thickness is uniform, and the surface roughness of the metal plate is 0°3μm, compared to the 3μm surface roughness of the conventional metallization method by printing and baking. Or you can get it as a general item. As a result, it is possible to obtain 10 times more uniformity than in metallized products, suppressing variations in electrical characteristics caused by non-uniform thickness of conventional metallized electrodes, and significantly reducing the amount of trimming required in mass production. , it is possible to improve yield.

Furthermore, iron-based materials with high mechanical strength can be used as the metal plate material, and this can be achieved by plating with copper, silver, or gold, which has low mechanical strength or high conductivity, as a surface treatment. By passing high frequency current only through the plated portion, a high Q resonant circuit can be obtained. Furthermore, since the input/output extraction electrodes serve as input/output terminals as they are, the problems described in FIGS. 7(A) and 7(B) of the conventional example are completely eliminated, and a small and economical filter can be realized.

By the way, alumina (1
20,) or low loss high dielectric constant ceramics are used.

When joining these materials to metal plates, there is a problem of deterioration of electrical characteristics due to mechanical strain due to differences in linear expansion coefficients. The coefficient of linear expansion of these ceramics is approximately 5 to 1.
1 pHm/°C, or by using an iron-nickel alloy as the metal plate, the linear expansion coefficients of both can be matched.

Iron-nickel alloys have a range of 0.9 to 2 depending on the nickel content.
Since the coefficient of linear expansion can be controlled within the range of 0 pI) m/'C, the optimum material can be selected depending on the ceramic used. In this way, a major feature of the present invention is that the electrical properties are determined by the surface treatment and that mechanically and thermally optimal materials can be selected.

FIG. 4 is a partial plan view and its X-Y sectional view showing an example of a metal plate 2o applied when the working frequency is low and a plurality of resonator electrodes 13 cannot be mechanically supported by only the commonly connected short-circuited ends. It is. A holding portion 21 is provided at a part of the open end of the resonator electrode 13, and this portion is thinned by half-etching. If you tap this part lightly just before assembly, it will come off. When forming these electrodes on a metal plate by four-etching, the four-etching process is performed from both sides of the metal plate, so
It is just a change of the resist version, and there is no increase in cost due to half-etching.

Although the present invention has been described above using a band pass filter as an example, it is obvious that the present invention can be applied to low pass filters, band elimination filters, and the like.

(Effects of the Invention) As described above in detail, the following effects can be obtained by implementing the present invention.

(1) The amount of trimming can be reduced, mass productivity is improved, and as a result, the filter can be constructed economically.

(2) It is compact because there is no need to add special terminals for external connections.

(3) Since a metal with good conductivity can be selected as the plating electrode metal on the side of the dielectric plate where high frequency current density is high, the Q of the resonant circuit is improved and loss can be reduced.

(4) Environmental resistance is achieved because it is possible to select materials that match the linear expansion coefficients of the dielectric plate and the metal plate.

It is possible to construct a highly reliable filter.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing a configuration example of the present invention, FIG. 2 is a perspective view showing an embodiment of the present invention, FIG. 3 is a side view of a filter with shaped input/output terminals of the present invention, and FIG. 5 is a sectional view showing the thickness of the metallized conductor, FIG. 6 is a partially cutaway perspective view showing a conventional example, and FIG.
XB) is a perspective view of a conventional filter with input/output terminals. 1.2... Dielectric substrate, 3.4... Slip I/Lip conductor, 5, 6... Input/output terminal, 7.8...
Grounding conductor, 9.10... Leading wire, 11.12.
...Dielectric substrate, 13a to 13e...Resonance electrode,
14...Guide hole, 15a, 15b...I/O extraction electrode, 16.17...Full surface metallized conductor, 1
8a to 18d...ground terminal, 20...metal plate, 2
1...Holding part.

Claims (1)

[Scope of Claims] A first dielectric substrate that is a rectangular flat plate and has electrodes provided on the entire surface of one main surface and a pair of opposing side end surfaces; A second electrode is provided on the entire main surface of the main surface and a pair of opposing side end surfaces.
a dielectric substrate, and the pair of side end surfaces of the first and second dielectric substrates are sandwiched between the other main surfaces in correspondence with each other, and the electrodes and end surfaces of the pair of side end surfaces are respectively fixed. a plurality of resonant electrodes arranged in parallel; one end of each of the plurality of resonant electrodes is commonly connected, and both end portions are exposed along one of the side end surfaces to form a ground terminal. a first metal plate integrally formed with a common connection portion and an external lead-out terminal portion whose ends are exposed by being drawn out from the first-stage and last-stage resonance electrodes of the plurality of resonance electrodes; and the side end surface. and a second metal plate formed to serve as a ground terminal with both end portions exposed along the other side of the planar dielectric filter.