Piezoelectric resonant filter, duplexer, and method of manufacturing same

A method of manufacturing a piezoelectric resonant filter including a thin-film piezoelectric resonator, the thin-film piezoelectric resonator having a piezoelectric thin film with a piezoelectric property and two exciting electrodes disposed on both surfaces of the piezoelectric thin film to apply an exciting voltage to the piezoelectric thin film, the piezoelectric resonant filter comprising a chip having the thin-film piezoelectric resonator, and a mounting substrate on which the chip is mounted, wherein the chip has a plurality of chip-side conductors made of a metal, the chip-side conductors being connected to the exciting electrodes or constituting the exciting electrodes, and the mounting substrate has a plurality of substrate-side conductors that are made of a metal and to be electrically connected to the chip-side conductors, the method of manufacturing the piezoelectric resonant filter comprising the steps of:

• fabricating the chip;
• fabricating the mounting substrate;
• forming a plurality of bumps on the chip-side conductors or on the substrate-side conductors;
• and
• mounting the chip on the mounting substrate by flip chip bonding such that the chip-side conductors and the substrate-side conductors are electrically and mechanically connected to each other via the bumps, wherein
• in the step of mounting, the bumps provided on the chip-side conductors are bonded to the substrate-side conductors, or the bumps provided on the substrate-side conductors are bonded to the chip-side conductors, by interdiffusion between atoms of the respective metals of which the bumps and the conductors are made, without involving melting of the respective metals of which the bumps and the conductors are made.

A duplexer comprising a first filter that allows a transmission signal to pass therethrough and interrupts a reception signal, and a second filter that allows the reception signal to pass therethrough and interrupts the transmission signal, the duplexer being connected to an antenna,

• wherein at least one of the first and second filters is a piezoelectric resonant filter including a thin-film piezoelectric resonator, the thin-film piezoelectric resonator having a piezoelectric thin film with a piezoelectric property and two exciting electrodes disposed on both surfaces of the piezoelectric thin film to apply an exciting voltage to the piezoelectric thin film, the piezoelectric resonant filter comprising:
• a chip having the thin film piezoelectric resonator;
• and
• a mounting substrate on which the chip is mounted, wherein:
• the chip has a plurality of chip-side conductors made of a metal, the chip-side conductors being connected to the exciting electrodes or constituting the exciting electrodes;
• the mounting substrate has a plurality of substrate-side conductors that are made of a metal and to be electrically connected to the chip-side conductors;
• the piezoelectric resonant filter further comprises a plurality of bumps provided on the chip-side conductors or on the substrate-side conductors;
• the chip is mounted on the mounting substrate by flip chip bonding such that the chip-side conductors and the substrate-side conductors are electrically and mechanically connected to each other via the bumps;
• and
• the bumps provided on the chip-side conductors are bonded to the substrate-side conductors, or the bumps provided on the substrate-side conductors are bonded to the chip-side conductors, by interdiffusion between atoms of the respective metals of which the bumps and the conductors are made, without involving melting of the respective metals of which the bumps and the conductors are made.

A method of manufacturing a duplexer comprising a first filter that allows a transmission signal to pass therethrough and interrupts a reception signal, and a second filter that allows the reception signal to pass therethrough and interrupts the transmission signal, the duplexer being connected to an antenna, wherein at least one of the first and second filters is a piezoelectric resonant filter including a thin-film piezoelectric resonator, the thin-film piezoelectric resonator having a piezoelectric thin film with a piezoelectric property and two exciting electrodes disposed on both surfaces of the piezoelectric thin film to apply an exciting voltage to the piezoelectric thin film, the piezoelectric resonant filter comprising a chip having the thin-film piezoelectric resonator, and a mounting substrate on which the chip is mounted, wherein:

• the chip has a plurality of chip-side conductors made of a metal, the chip-side conductors being connected to the exciting electrodes or constituting the exciting electrodes;
• and the mounting substrate has a plurality of substrate-side conductors that are made of a metal and to be electrically connected to the chip-side conductors, the method of manufacturing the duplexer comprising:
• the step of manufacturing the first filter and the step of manufacturing the second filter,
• wherein at least one of the steps of manufacturing the first filter and manufacturing the second filter includes the step of manufacturing the piezoelectric resonant filter, the step of manufacturing the piezoelectric resonant filter including the steps of:
• fabricating the chip of the piezoelectric resonant filter;
• fabricating the mounting substrate;
• forming a plurality of bumps on the chip-side conductors or on the substrate-side conductors;
• and
• mounting the chip on the mounting substrate by flip chip bonding such that the chip-side conductors and the substrate-side conductors are electrically and mechanically connected to each other via the bumps, wherein
• in the step of mounting, the bumps provided on the chip-side conductors are bonded to the substrate-side conductors, or the bumps provided on the substrate-side conductors are bonded to the chip-side conductors, by interdiffusion between atoms of the respective metals of which the bumps and the conductors are made, without involving melting of the respective metals of which the bumps and the conductors are made.