Band-pass filter module and module substrate
View Patent ↗A bandpass filter module includes a mounting board and a BPF chip mounted on a surface thereof. The BPF chip includes three or more resonators; a first-stage resonator located closest to an input terminal, a final-stage resonator located closest to an output terminal, and a middle-stage resonator connected between the first-stage and the final-stage resonators and located in a chip middle zone. The mounting board includes an area overlapping with the chip middle zone, viewed in plan, defining a ground-free space in which no ground electrode is disposed. The ground-free space is formed at least from the surface of the mounting board to a depth position at which a topmost internal wiring layer is located. The middle-stage resonator is prevented from being coupled to ground electrodes on the mounting board and from a lower Q-value and increased insertion loss.
1. A bandpass filter module comprising:
a mounting board capable of mounting a filter chip on a surface thereof; and
a filter chip mounted on the surface of said mounting board, wherein
said mounting board comprises one or more internal wiring layers;
said filter chip includes three or more resonators connected between an input terminal and an output terminal for forming a predetermined pass band;
said filter chip includes a chip middle zone defined by an area contained between one longitudinal side and another longitudinal side of said filter chip, said chip middle zone including a chip center zone defined by an area contained between one lateral side and another lateral side of said filter chip, wherein said three or more resonators include a first-stage resonator connected closest to the input terminal, a final-stage resonator connected closest to the output terminal, and a middle-stage resonator connected between said first-stage resonator and said final-stage resonator, said middle-stage resonator being disposed in said chip middle zone;
said mounting board includes an area overlapping with said chip center zone, when viewed from above, said area defining a ground-free space in which no ground electrode is disposed, said ground-free space being formed at least from the surface of said mounting board to a depth position at which a topmost internal wiring layer is located among said one or more internal wiring layers;
said ground-free space comprises a hole formed through the surface of said mounting board; and
the hole is free from conductors.
2. A bandpass filter module according to claim 1 , wherein:
said ground-free space is filled with an insulating material.
3. A bandpass filter module according to claim 1 , wherein:
each of said resonators is formed of an inductor electrode and capacitor electrodes disposed on some of a plurality of wiring layers included in a laminated board, and
said middle-stage resonator comprises an inductor electrode and capacitor electrodes disposed on internal wiring layers of said laminated board.
4. A bandpass filter module according to claim 1 , wherein:
said resonators are formed in a laminated board, and
said laminated board is an LTCC board.
5. A bandpass filter module according to claim 1 , wherein:
said filter chip comprises a thin-film chip having wiring layers and insulating layers laminated on a surface of a base board by a vapor deposition method, and
said resonators are located on wiring layers formed on the surface of said base board.
6. An electronic module comprising:
a bandpass filter module according to claim 1 ; and
one or more electrical function elements mounted on said mounting board and electrically connected to said filter chip.
7. A bandpass filter module according to claim 1 , wherein:
said filter chip is equally divided by two in a thickness direction, wherein said middle-stage resonator is disposed in a lower half close to said mounting board.
8. A bandpass filter module according to claim 2 , wherein:
said filter chip is equally divided by two in a thickness direction, wherein said middle-stage resonator is disposed in a lower half close to said mounting board.
9. A bandpass filter module according to claim 3 , wherein:
said filter chip is equally divided by two in a thickness direction, wherein said middle-stage resonator is disposed in a lower half close to said mounting board.
10. A bandpass filter module according to claim 4 , wherein:
said filter chip is equally divided by two in a thickness direction, wherein said middle-stage resonator is disposed in a lower half close to said mounting board.
11. A module board having one or more internal wiring layers and a filter mounting area capable of mounting a filter chip on a surface thereof, comprising:
an input terminal electrode disposed on one longitudinal side of said filter mounting area and capable of receiving an input terminal of a filter chip;
an output terminal electrode disposed on another longitudinal side of said filter mounting area and capable of receiving an output terminal of the filter chip; and
a ground terminal electrode disposed on one lateral side of said filter mounting area and capable of receiving a ground terminal of the filter chip, wherein
said filter mounting area includes a central area which occupies a center zone thereof, when viewed from above, said central area defining a ground-free space in which no ground electrode is disposed, said ground-free space being formed at least from the surface of said mounting board to a depth position at which a topmost internal wiring layer is located among said one or more internal wiring layers;
said ground-free space comprises a hole formed through the surface of said mounting board; and
the hole is free from conductors.
12. A module board according to claim 11 , wherein:
said ground-free space is filled with an insulating material.