JPS5936020Y2 - Composite ceramic filter - Google Patents

Description

[Detailed description of the invention] This invention proposes a composite ceramic filter in which two 3-terminal dual mode filters are connected in series on the same substrate via a coupling capacitor, and the unnecessary noise that occurs between adjacent dual mode filters. The present invention relates to a filter structure that is compact and easily mass-produced, which suppresses transmission of vibration waves and spurious responses due to interference as much as possible.

Conventionally, this type of filter has either a dual mode filter section and a coupling capacitor section formed on separate substrates, electrically connected and then packaged, or a group of elements formed on a single substrate. However, there is a type in which a slit, hole, etc. is provided between two dual mode filters to prevent transmission of unnecessary vibration waves.

However, the former method has drawbacks such as deterioration of filter characteristics due to variations in characteristics between the two dual mode filters, increased size of the filter, and complexity of the process.

Moreover, the latter has drawbacks such as deterioration in mechanical strength and difficulty in machining slits, holes, etc. with restrictions on position and size.

The present invention eliminates these drawbacks and provides a filter that is compact and easy to mass produce.

Embodiments of the present invention, together with preferred manufacturing methods, will be described below with reference to the drawings.

Referring to FIG. 1, first, divided electrodes 2a, 2b and 2a', 2b' are provided on the surface of a ceramic substrate 1.
On the back side, common ground electrodes 3 and 3' are provided opposite the divided electrodes.

One double mode filter is constituted by the divided electrodes 2a, 2b and the common ground electrode 3, and yet another filter is constituted by the divided electrodes 2a', 2b' and the common ground electrode 3'.

Further, external connection electrodes 4a and 4a' are drawn out from the electrodes 2a and 2a' on the surface of the substrate 1, and the electrodes 2b and 2b' are electrically connected to each other by the connection electrode 10 through the capacitance forming electrodes 7a and 7a'. connected to.

On the other hand, on the back surface of the substrate 1, capacitance forming electrodes 7b and 7b' are provided opposite to the capacitance forming electrodes 7a and 7a', and a conductor 8 passes through the center of the substrate together with the common ground electrodes 3 and 3'. It is connected to the external connection ground electrode 6 at the lower end of the center of the board.

Further, on the back surface of the substrate 1, a groove 5 having a width narrower than the width of the conductor 8 and dividing the conductor 8 and the ground electrode 6 for external connection into two is formed extending from the upper end of the substrate 1 to the lower end.

Therefore, the ground electrode 6 for external connection is connected to the ground electrode 6a by the groove.
, 6b, and similarly, the conductor 8 is also divided into two conductors 8a and 8b by the groove.

Note that the grooves may be processed either before or after the vacuum deposition of the electrodes and conductors.

FIG. 2 shows the structure of a composite ceramic filter according to the present invention.

Referring to FIG. 2, first, the substrate 1 shown in FIG. 1 is sandwiched between the comb tooth-shaped lead wires 9a, 9b, and 9C as shown in FIG. ' are respectively connected to lead wires 9a and 9b by soldering.

Next, the substrate 1 is inserted into two substrates 1a and 1b along the groove 5.
Divide into.

After that, the external connection ground electrodes 6a and 6b are commonly connected to the lead wire 9C by soldering, and the connection conductor 10 of the electrodes 2b and 2b', which are electrically separated by dividing the board 1, is connected to the solder bridge 10'. Connect by etc.

At this time, since the substrates 1a and 1b are connected to the lead wires 9a and 9b, respectively, there is no positional shift due to the division of the substrate 1, and the same state as the substrate 1 before division is maintained, and the lead wires 9C and Ground electrode 6a for external connection,
6b and the separate connection conductor 10 can be easily made.

In this way, the composite ceramic filter according to the present invention is completed.

Figure 3 shows the frequency vs. attenuation characteristics of a resin-coated filter, where the solid line 11 is the characteristic according to the present invention, and the broken line 12 is the characteristic when the same electrode pattern and connection as the present invention are configured on the same board. .

As shown above, in the present invention, since a composite filter is composed of two substrates separated from a single ceramic substrate, there is no need to avoid the unnecessary noise that occurs when two dual-mode filters are formed on the same substrate. It can very well block the transmission of vibration waves.

In addition, compared to the case of randomly selecting and assembling two ceramic substrates that are naturally fired and prone to variations,
In the case of a pair of two substrates obtained by dividing one substrate according to the present invention, there will be extremely little deviation in material and dimension, so there will be little variation in the characteristics of the two dual mode filters, and the filter characteristics will be reduced. There is little deterioration.

In addition, the shape and dimensions can be the same as those formed on the same substrate, which is advantageous in terms of miniaturization.

Note that the groove processing for the purpose of dividing the substrate in the above embodiment can be easily realized with a laser scriber or the like, and is excellent in mass production.

In this embodiment, the coupling capacitance section is formed by two substrates 1a.

1b, but it is also possible to concentrate on one of them.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an intermediate product in an example of the method for manufacturing a composite ceramic filter according to the present invention, FIG. 2 is a perspective view showing the structure of a composite ceramic filter according to the present invention, and FIG. 3 is a perspective view of an intermediate product according to the present invention. FIG. 2 is a frequency versus attenuation characteristic curve diagram showing the filter characteristics of a composite ceramic filter according to the present invention in comparison with that of a conventional filter. 1...Piezoelectric ceramic substrate, la, lb...
...Divided piezoelectric ceramic substrates, 2a, 2b
, 2a'. 2b'...Divided electrode, 3,3'...Common ground electrode, 4a. 4a'... Input/output electrode for external connection, 5...
...Concave groove, 6...Grounding electrode for external connection, 7a,
7a', 7b, 7b'...Capacitance forming electrode, 8
...Conductor, 9a, 9b. 9C...Lead wire, 10...Connection conductor.

Claims (1)

[Scope of utility model registration request] In a composite ceramic filter comprising two energy trapping type dual mode filters formed by forming required electrodes on a piezoelectric ceramic substrate, and a coupling capacitor disposed on the substrate and coupling the filters, the piezoelectric ceramic The substrate is divided at the center of each region constituting the two filters, both divided pieces are joined at the dividing plane, and comb teeth are connected to input/output electrodes for external connection of the two filters. The lead wires formed in a shape are connected to each other, and the conductors on both divided pieces to be connected to each other extend to the joint of the divided pieces, and a solder bridge provided to span both conductors connects each other with electricity. The grounding electrodes for surface external connection on both divided pieces are electrically connected in common to the grounding terminal of the comb tooth-shaped lead wire, and both are electrically connected by the solder bridge and the grounding terminal. A composite ceramic filter characterized in that the joined state of the divided pieces is maintained.