JPH06132711A - Manufacture of dielectric filter - Google Patents

Abstract

PURPOSE:To permit an outer conductor to suppress the leakage of an electromagnetic field so as to prevent the deterioration of a resonator Qu by printing a plating resist on a part forming a window part for inter-stage connection and executing electroless plating. CONSTITUTION:Resinous plating resist 12 is screen-printed on a surface 11 where the window for inter-stage connection, which is adjacent to the bottom 10 of a dielectric block 8 having a through hole 9, is provided so as to no plating film is formed. The resist 12 is printed and applied in the form of the window for inter-stage connection to be formed, and it is set to be that which is vertical to the through hole 9 and which does not reach the bottom 10. Then, electroless copper plating is executed on the dielectric block 8, and the outer conductor layer and an inner conductor layer are provided. The conductor layer is not formed by the resist 12 which is printed or applied in the inter-stage connection window part. Then, peeling processing of the resist 12 is executed in the dielectric block 8 where the conductor layer is formed in a solution, and an open surface or the bottom 10 are grinding-worked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a dielectric filter used in a microwave band used for mobile communication equipment and the like.

[0002]

2. Description of the Related Art Conventionally, as a dielectric filter using a coaxial resonator, for example, Japanese Utility Model Publication No. 62-44566 (H).
01P1 / 205) is known.
This conventional dielectric filter is provided with a through hole in a dielectric member, and a plurality of single-sided short-circuit type formed by coating a conductive member on the outer peripheral surface of the dielectric member and the inner peripheral surface of the through hole. The coaxial resonator is connected to a dielectric substrate, and the coaxial resonators are capacitively coupled by electrodes formed on the dielectric substrate.

[0003]

In recent years, mobile communication equipment is required to be smaller and lighter, and accordingly, the dielectric filter, which is one of the components, is also required to be smaller. ing.

By the way, in order to obtain a high Qu (Q value when no load is applied) when miniaturizing the dielectric filter, if the inner coaxial diameter is a and the outer conducting shaft diameter is b, then b / a = It is desirable to set it to 3.6, but if the outer coaxial diameter is 4 mm or less,
The inner coaxial diameter is 1.2 mm or less, and it is extremely difficult to insert the external connection member into the through hole of the coaxial resonator and connect it to the external circuit as in the above-mentioned conventional technique, and there is a limit to miniaturization thereof. There is a drawback that there is. In order to improve this, the present applicant has already filed Japanese Patent Application No. 4-82106. In this prior art, the open faces of the coaxial resonator including the input / output stages are staggered on a dielectric substrate having input / output coupling striplines and a coplanar ground conductor provided so as to surround these striplines. The size of the dielectric substrate is reduced by making the area of the dielectric substrate equal to the cross-sectional area of the coaxial resonator array direction.
In this prior art, as shown in FIG.
The outer conductor 27 and the inner conductor 28 are formed by covering the outer peripheral surface and the inner peripheral surface of the dielectric block 25 having the outer peripheral surface 4 with a conductive member, and the outer surface of the surface 29 facing the dielectric substrate is outside. The conductor is removed, and a part of the outer conductor of the surface 30 adjacent to the dielectric substrate facing surface 29 is removed by a dicing saw or the like to form a window 31 for interstage coupling to complete the coaxial resonator 32. There is.

However, in this prior art, since the inter-stage coupling window 31 is formed by a dicing saw, the outer conductor of the surface 30 is removed until it reaches the dielectric substrate facing surface 29. As a result, the Qu of the coaxial resonator 32 is lowered and the characteristics of the dielectric filter are deteriorated.

[0006]

In view of the above-mentioned drawbacks of the prior art, the present invention provides a method of manufacturing a dielectric filter comprising a dielectric substrate having an input / output coupling stripline and a plurality of dielectric coaxial resonators. In, a step of forming a dielectric ceramic into a prismatic block having a through hole, a step of sintering the block, and a step of printing a resist for plating on a portion forming a window portion for interstage coupling of the block A step of performing electroless plating on the block, a step of removing the resist, a step of polishing the open end face and the bottom surface to complete a coaxial resonator, and a dielectric having a strip line for the coaxial resonator. And a step of fixing on a substrate.

[0007]

According to the present invention, the plating resist is printed only on the portion where the inter-stage coupling window portion is formed and electroless plating is performed. Therefore, the inter-stage coupling window is formed by peeling off the resist. Therefore, unlike the prior art, the removal of the outer conductor does not reach the first surface, and the outer conductor remaining between the first surface and the second surface suppresses the leakage of the electromagnetic field and thus the resonator Qu.
Prevent the decline.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a manufacturing method according to the present invention. First, the dielectric ceramic was formed into a prismatic shape having a through hole by a mold (step 1) and sintered (step 2).
After that, the surface is etched with a mixed acid such as hydrofluoric acid and nitric acid in order to improve the adhesion of the plating (step 3).

After that, resist printing (step 4) is performed. That is, for example, M85-N (World Metal Co., Ltd.) is used so that a plating film is not formed on the surface 11 adjacent to the bottom surface 10 of the dielectric block 8 having the through hole 9 in FIG. Resin-based plating resist 12 such as a product) is screen-printed. Note that FIG.
As described above, a rubber-based resist 13 such as seal peel 8008 (manufactured by World Metal Co., Ltd.) may be applied as a plating resist by a dispenser. The resist is printed and applied in the shape of a window for interstage coupling to be formed, which is perpendicular to the through hole and does not reach the bottom surface 10.

Next, this dielectric block 8 is subjected to electroless copper plating (step 5) to provide an outer conductor layer and an inner conductor layer having a thickness of 4 μm or more. At this time, the conductor layer is not formed in the inter-stage coupling window portion by the printed or applied resist.
Further, if electroless plating is carried out for a long time, resist peeling or the like occurs, so electroless plating may be carried out in a short time, and then the conductor layer may be formed by electrolytic plating.

After that, the dielectric block having the conductor layer formed thereon is subjected to a resist stripping treatment in a solution of 1.1.1-trichloroethane (step 6), and the open surface and the bottom surface are further polished (step 7). , Complete the resonator. Figure 4,
FIG. 5 shows the completed coaxial dielectric resonator,
In the figure, 14 is a coaxial dielectric resonator, 15 is an outer conductor,
16 is an inner conductor, 17 is an open surface, 18 is a bottom surface, and 19 is a window for interstage coupling. This inter-stage coupling window 19 has a bottom surface 18
It is formed without reaching.

FIG. 6 shows a dielectric filter formed by using two coaxial resonators 14 manufactured as described above. The coaxial resonators 14 and 14 are provided on the dielectric substrate 20 with the open ends 17. The two windows are arranged so that they are staggered and the inter-stage coupling windows 19 are opposed to each other, and the bottom surface 18 faces downward, and they are attached with an adhesive such as an epoxy resin. Dielectric substrate 2
0 is formed of a dielectric material and has the same area as two coaxial resonators 14 arranged alternately and in parallel.

FIG. 7 shows this dielectric substrate 20, FIG. 7 (A) shows the surface on which the coaxial resonator 14 is mounted, and FIG. 7 (B) shows the back surface. . 21, 2
Reference numeral 2 is an input / output coupling strip line, which is a coaxial resonator 1.
By arranging 4 so that the open surface 17 side thereof faces each other, input / output coupling between the coaxial resonator 14 and an external circuit is performed. Reference numeral 23 denotes a ground electrode, which is electrically connected on the front and back surfaces and prevents electrical interference between the input coupling strip line 21 and the output coupling strip line 22.

The dielectric filter according to the present invention thus formed has less deterioration of the resonator Qu as compared with the conventional one. That is, in the dielectric filter using two coaxial resonators as in this embodiment, when the conventional resonator shown in FIG. 7 is used, there is a deterioration of 15 to 18% in Qu. When the coaxial resonator is used, it can be suppressed to around 10%. In addition, the insertion loss, which is one of the filter characteristics, is significantly smaller than that of the conventional filter.

Although a two-stage dielectric filter using two dielectric resonators 6 has been described in this embodiment, FIG.
The intermediate stage resonator is interposed between the two coaxial resonators 6 shown in Fig. 6, and the interstage coupling windows are formed on both side surfaces thereof in the same manner as described above, and the dielectric substrate is expanded to provide multistage resonance. It goes without saying that you can get a vessel.

[0016]

In the method of manufacturing a dielectric filter according to the present invention, electroless plating is performed after printing or applying a plating resist on the portion where the window for interstage coupling is formed. Does not reach the surface facing the substrate, and leakage of electromagnetic fields can be suppressed by the remaining outer conductor,
It is possible to prevent the resonator Qu from being lowered and obtain excellent filter characteristics.

[Brief description of drawings]

FIG. 1 is a diagram showing a method for manufacturing a dielectric filter according to the present invention.

FIG. 2 is a diagram showing a dielectric block used in the present invention.

FIG. 3 is a diagram showing a dielectric block used in the present invention.

FIG. 4 is a diagram showing a coaxial resonator used in the present invention.

FIG. 5 is a diagram showing a coaxial resonator used in the present invention.

FIG. 6 is a diagram showing a dielectric filter according to the present invention.

FIG. 7 is a diagram showing a dielectric substrate.

FIG. 8 is a diagram showing a coaxial resonator according to the related art.

[Explanation of symbols]

 8 Dielectric Block 9 Through Hole 12 Plating Resist 13 Plating Resist 14 Coaxial Resonator 17 Opening Surface 18 Bottom 19 Interstage Coupling Window 20 Dielectric Substrate 21 Input Stripline 22 Output Stripline

Claims (1)

[Claims] 1. A method of manufacturing a dielectric filter comprising a dielectric substrate having an input / output coupling stripline and a plurality of dielectric coaxial resonators, wherein a dielectric ceramic is molded into a prismatic block having a through hole. The step of sintering, the step of sintering the block, the step of printing a resist for plating on a portion of the block where the window portion for interstage coupling is formed, the step of performing electroless plating on the block, and the resist And a step of polishing the open surface and the bottom surface to complete a coaxial resonator, and a step of fixing the coaxial resonator on a dielectric substrate having a stripline. Filter manufacturing method.