Surface-mount package for an optical sensing device and method of manufacture

An infrared sensor package comprising:

• a chip carrier formed of a low-temperature co-fired ceramic material, the chip carrier having a first surface, an oppositely-disposed second surface, conductive vias extending through the chip carrier between the first and second surfaces thereof, and bond pads on the second surface and electrically connected to the conductive vias;
• a device chip flip-chip mounted to the first surface of the chip carrier with first solder connections electrically connected to the conductive vias of the chip carrier, the device chip having an infrared sensing element on a surface thereof;
• and
• a capping chip secured with a solder ring to the chip carrier to hermetically enclose the device chip within a cavity defined between the chip carrier and the capping chip, the capping chip being formed of monocrystallographic silicon so as to enable infrared radiation to pass through a wall portion of the capping chip to the infrared sensing element on the device chip, the solder ring having a lower melting temperature than the first solder connections.

A method of fabricating an optical sensor package, the method comprising the steps of:

• forming a chip carrier to have conductive vias that extend through the chip carrier from a first surface thereof to a second surface thereof;
• securing a device chip to the first surface of the chip carrier with solder connections that electrically connect the device chip to the conductive vias of the chip carrier, the device chip having an optical sensing element on a surface thereof;
• and
• securing a capping chip to the chip carrier to hermetically enclose the device chip, the capping chip having means for enabling radiation to pass through the capping chip to the device chip.

A method of simultaneously fabricating a plurality of infrared sensor packages, the method comprising the steps of:

• forming a chip carrier wafer of a low-temperature co-fired ceramic material, the chip carrier wafer comprising a plurality of chip carriers, each chip carrier having a first surface, an oppositely-disposed second surface, conductive vias extending therethrough between the first and second surfaces, and bond pads on the second surface and electrically connected to the conductive vias, the conductive vias being formed by screen printing during a green tape portion of forming the chip carrier wafer;
• flip-chip mounting a device chip to the first surface of each chip carrier, the device chip being mounted with first solder connections that electrically connect the device chips to the conductive vias of the chip carriers, the device chip having an infrared sensing element on a surface thereof;
• securing a capping chip wafer to the chip carrier wafer with solder rings to form a wafer stack, each of the solder rings hermetically enclosing a corresponding one of the device chips within a cavity defined between their respective carrier and capping chips, the capping chip wafer being formed of monocrystallographic silicon so as to enable infrared radiation to pass through a wall portion of each capping chip to each of the device chips, the solder rings having a lower melting temperature than the first solder connections;
• performing automated simultaneous testing of the device chips;
• and then singulating the wafer stack to separate the plurality of infrared sensor packages.