JP2000353903A - Dielectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve initial decline in performance and the performance degradation after use by forming a connecting conductor with a circuit substrate on a notch surface of a side shared by a non-conductor surface to which a resonator opens and a surface connected and fixed on the circuit substrate. SOLUTION: Plural resonator holes 2a and 2b are provided inside a dielectric block 1, inner conductors 3a and 3b are formed on an inner surface of the resonator holes 2a and 2b and an outer electric conductor 7 is formed on an outer surface of the dielectric block. The bottom side of a front side 1a being a non-conductor surface is obliquely notched and a connecting conductor 15 of a circuit substrate and a substrate is provided on its notch surface. The notch surface of a dielectric filter 21 faces the circuit substrate, a gap between the connecting conductor 15 of the substrate and the circuit substrate ranges along the notch surface and more solders are charged at a lower part of the front side 1a. Thus, sureness of connection increases and, at the same time, a fillet to a conductor pattern of the substrate projects outside the front side 1a and it can visually be confirmed well.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter suitable for a radio communication system that handles signals in a high frequency band, particularly in the gigahertz (GHz) band.

[0002]

2. Description of the Related Art As a filter having deep attenuation poles on both sides of a pass frequency band and capable of adjusting the frequency at which the attenuation pole is generated, the present applicant has proposed a dielectric filter disclosed in Japanese Patent Application No. 8-120252. .

FIG. 5 shows a dielectric filter 20 of the above-mentioned application example.
It is a perspective view which shows the whole of FIG. Reference numeral 1 denotes a rectangular parallelepiped dielectric block, which is formed by sintering a BaO-TiO2-Nd2O3-based ceramic material or a CaO-TiO2-based dielectric material. Block 1
Are provided with two resonator holes 2a and 2b opened in the front surface 1a in parallel with each other, and the inner surfaces thereof are inner conductors 3a and 2b.
3b is formed. An outer conductor 7 is formed on each of the outer surfaces of the block 1 except the front surface 1a, and input / output electrodes 4a, 4a connected to the inner conductors 3a, 3b are provided on both side surfaces.
b is provided, and the connection conductor 6 on the inner surface of the through holes 5a and 5b is provided.
a and 6b connect to the inner conductors 3a and 3b. The input / output electrodes 4a, 4b are formed of surrounding separation bands 8a, 8b having a convex cross section.
Are separated from the outer conductor 7.

[0004] The front surface 1a is a surface on which no conductor is formed. In this surface, short-circuit connection conductors 10a and 10b connecting the outer conductor 7 and the inner conductors 3a and 3b are arranged so as not to be electromagnetically coupled to each other. Has been established. This short-circuit connection conductor 10
To form a and 10b, a conductor is formed on the entire outer periphery of the dielectric block 1 after forming a concave portion on the front surface 1a, and thereafter,
A method of grinding the front surface 1a to leave a conductor on the inner surface of the concave portion or the like is used. The hatched surface in the figure indicates a region where no conductor is formed.

FIG. 6 shows a state in which the dielectric filter 20 is mounted on the circuit board 19 by a cross section taken along line 6-6 in FIG. The filter 20 is soldered to the substrate 19 at a total of four locations, that is, two locations below the electrodes 4a and 4b on the side surfaces and two locations below the front surface 1a and the rear surface 1b. Numerals 30 and 31 in the drawing indicate solders attached to the lower portions of the front surface 1a and the rear surface 1b, respectively. These solders 30 and 31 are the conductor patterns 3 of the ground circuit on the substrate 19.
2 and 33, and has a function of reliably grounding the outer conductor 7.

[0006]

The dielectric filter 20 of the above-mentioned application has a deep attenuation pole for surely blocking the lower and upper frequencies of the fundamental frequency, and by adjusting the shaving depth of the front surface 1a. It has an excellent characteristic that a frequency serving as an attenuation pole can be arbitrarily set. However, since the dielectric material, which is the material of the block, is exposed on the front surface 1a, it is inevitable that the solderability is worse than that of the conductor surface. As a result, as shown in FIG. 6, the solder 31 on the rear surface 1b forms a so-called solder fillet having a fillet shape to ensure good connection and fixation, but the solder 30 on the front surface 1a is filleted with respect to the front surface 1a. Cannot be formed, and there is a problem that the soldering is not stable.
In addition, the solder 30 slightly protrudes outside the front surface 1a and is hardly visible from above, and it is determined by visual inspection of the appearance whether a sufficient amount of solder has entered the gap between the solder pattern 30 and the conductor pattern 32 of the substrate 19. Judgment was difficult.

SUMMARY OF THE INVENTION An object of the present invention is to stabilize soldering at a lower portion of a non-conductive surface to secure connection and fixation to a circuit board, and to solve various problems caused by poor soldering, that is, initial performance deterioration and after use. It is an object of the present invention to provide a dielectric filter in which the performance degradation of the dielectric filter is eliminated.

[0008]

According to a first aspect of the present invention, there is provided a dielectric filter, wherein a plurality of resonator holes are provided inside a dielectric block, an inner conductor is provided on an inner surface of the resonator hole, and an outer surface of the dielectric block is provided. In a dielectric filter having an outer conductor formed on it,
The open surface of the resonator is a non-conductive surface, and a common side of the non-conductive surface and a surface connected and fixed to the circuit board is cut out, and a connection conductor to the circuit board is formed in the cut-out surface. It is characterized by.

As a result, at the bottom of the non-conductive surface, the contact area with the solder is increased and the filling amount is increased, so that the connection with the circuit board is made more reliable. In addition, the solder protrudes appropriately outside the non-conductive surface, so that it is easy to determine whether the soldering is good or not, and the work of sorting out defective products is speeded up.

In the dielectric filter according to a second aspect of the present invention, the shape of the notch is rectangular when viewed from the side. The soldering at the bottom of the non-conductive surface has the same effect as that of the dielectric filter according to the first aspect. In addition, there is an advantage that the shape of the solder fillet is constant even if the cutting depth of the non-conductive surface changes. .

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the dielectric filter according to the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a dielectric filter 21 according to the first embodiment of the present invention. In the figure, the same parts and portions as those in the conventional example are denoted by the same reference numerals, and description thereof will be omitted. In the present embodiment, the bottom side of the front surface 1a, which is a non-conductive surface, is notched obliquely, and a connection conductor 15 for connecting to a substrate is provided on the cutout surface.

FIG. 2 shows that the dielectric filter 21 is mounted on the circuit board 1.
9 is shown by a cross section taken along line 2-2 in FIG. The cutout surface of the dielectric filter 21 faces the circuit board 19, the distance between the connection conductor 15 and the circuit board 19 increases along the cutout surface, and the lower part of the front surface 1a is filled with more solder 30. . As a result, the reliability of the connection is increased, and the fillet to the conductor pattern 32 of the substrate protrudes out of the front surface 1a, so that it can be sufficiently confirmed visually.

Next, a method for manufacturing such a dielectric filter will be described. First, dielectric materials such as BaO-TiO2-Nd2O3 (relative permittivity εr = 90) and CaO-TiO2 (relative permittivity ＝ r = 46) are selected from target filter characteristics, and injection molding is used. Mold into a predetermined shape. The molded block is further fired in a furnace to form a sintered body, and a final dielectric block 1 is formed.

Subsequently, conductors are formed on the entire outer surface of the dielectric block 1 and on the inner surfaces of the resonator holes 2a and 2b. For forming the conductor, a method of applying Cu by electroless plating, a method of applying a conductive paste made of Ag as a material by baking, or the like is used.

Thereafter, the unnecessary conductor portions, that is, the conductors on the convex surrounding separating bands 8a and 8b and the front surface 1a shown in FIG. 1 are removed by grinding with a grindstone. First, separation zones 8a and 8b
The input / output electrodes 4a and 4b separated from the outer conductor 7 are formed by grinding the upper surface of the substrate. Further, the front surface 1a is similarly ground with a grindstone, and the filter characteristics are adjusted so as to be within a deviation of a predetermined design value by the shaving depth. The size of the dielectric filter 21 manufactured in this manner is
The dimensions of the length (the depth direction in FIG. 1) x the width, and the height of the bottom surface are, for example, about 3.0 × 4.0 × 2.0 mm.

In the conventional dielectric filter 20 shown in FIG. 5, the short-circuit portion connection conductors 10a, 1a are ground by grinding the front surface 1a.
Although the entire surface except for Ob is a non-conductive surface, in the dielectric filter 21 of the present invention, after grinding the front surface 1a, the connection conductor 15 with the substrate formed on the cutout surface at the bottom remains, and the above-described soldering is not performed. It is effective.

The height of the notch in the dielectric filter 21 of the present invention from the bottom surface, and the dimension A in FIG. 2 is large enough to allow the solder to flow in, and the open resonator holes 2a and 2b
The operation as a filter is possible within a range not in contact with the inner conductors 3a and 3b. However, if it is set too large, the performance changes when the front surface 1a is cut off are large, and adjustment is difficult. Taking the above into consideration, 0.05-0.
A range of 4 mm is preferred. Depth from front 1a, FIG.
B may be larger than 0.05 mm and within a range up to the conductor pattern 32 formed on the substrate 19. Also, the width may extend over the entire width of the front surface 1a as shown in FIG.
Alternatively, the solder 30 may be provided only at the center, for example, within a sufficient amount of solder.

FIG. 3 is a perspective view of a dielectric filter 22 according to a second embodiment of the present invention. In the present embodiment, as an example included in claim 2, a step having a rectangular cross section is cut out only at the center of the bottom of the front surface 1a, and the connection conductor 15 is formed on the concave surface of the groove-shaped notch 40. Has formed. FIG.
3 shows a state in which the dielectric filter 22 is attached to the circuit board 19 by a cross section taken along line 4-4 in FIG.

As can be seen from FIG. 4, the solder portion 30 is filled more deeply into the interior than in the first embodiment, and it is expected that the reliability of connection with the substrate 19 will be further improved. In addition, the shape of the solder fillet between the connection conductor 15 and the conductor pattern 32 is kept substantially the same regardless of the cut-out depth of the front surface 1a.

The method of manufacturing the dielectric filter of the second embodiment is basically the same as that of the first embodiment,
An appropriate size range of the notch 40 is substantially the same. The height from the bottom surface and the C dimension in the figure are preferably in the range of 0.05 to 0.4 mm, and the depth dimension and the D dimension in the figure are within 0.05 mm or more and up to the conductor pattern 32 of the substrate 19. Good. The width direction may be only the central portion as shown in FIG. 3 or may extend over the entire width of the front surface 1a.

[0021]

As described above, in the dielectric filter of the present invention, since the soldering at the lower portion of the non-conductive surface is stabilized, the performance of the dielectric filter is deteriorated at the initial stage due to the poor soldering and the condition under the use condition. It is possible to reduce the deterioration of the performance and to easily determine whether the solder is sufficient by visual observation.

[Brief description of the drawings]

FIG. 1 is a perspective view of a dielectric filter according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is a perspective view of a dielectric filter according to a second embodiment of the present invention.

FIG. 4 is a sectional view taken along line 4-4 of FIG. 3;

FIG. 5 is a perspective view of a conventional dielectric filter.

FIG. 6 is a sectional view taken along line 6-6 in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dielectric block 2a, 2b Resonator hole 3a, 3b Inner conductor 4a, 4b Input / output electrode 6a, 6b Connection conductor between electrode and inner conductor 7 Outer conductor 8 Surrounding separation band 10a, 10b Short circuit connection conductor 15 Connection conductor

Claims (2)

[Claims] 1. A dielectric filter in which a plurality of resonator holes are provided inside a dielectric block, an inner conductor is formed on an inner surface of the resonator hole, and an outer conductor is formed on an outer surface of the dielectric block. The surface is a non-conductive surface, a side shared by the non-conductive surface and a surface connected and fixed to the circuit board is cut out, and a connection conductor to the circuit board is formed in the cut-out surface. Body filter. 2. The dielectric filter according to claim 1, wherein the shape of the notch is rectangular when viewed from the side.