Silicon package for piezoelectric device
A hermetic package for electronic components which is made of metallic silicon is disclosed. The package creates a cavity for receiving the electronic component, preferably a piezoelectric device, which provides a evacuated environment in the range of 1×10 −5 to 1×10 −11 torr. In a first embodiment, the single crystal metallic silicon is p-doped to make it electrically conductive, obviating the need for lead wires which could compromise the hermeticity of the package. Silicon-to-silicon bonding is preferably accomplished using brazing of the cover to the base member using gold indium eutectic alloy at 495° C. A method of making a surface mountable electronic component having an internal hermetic environment is also described.
1. A hermetic package for enclosing a high precision piezoelectric device comprising
a) a base member made entirely of a single crystal of metallic silicon;
b) a cover made entirely of a single crystal of metallic silicon;
c) a cavity formed between said base member and said cover for receiving the piezoelectric device, said cavity providing a high vacuum environment for the piezoelectric device, said vacuum falling in the range between 1×10 −5 and 1×10 −11 torr;
d) thermo-compression bonding means performed at high temperature for securing said cover directly to said base member.
2. The package of claim 1 wherein said thermo-compression bonding means is performed in a temperature range of between 300° C. and 800° C.
3. The package of claim 1 wherein said piezoelectric device is an ultra-stable oscillator.
4. The package of claim 3 wherein said ultra-stable oscillator comprises a quartz crystal.
5. The package of claim 4 wherein said ultra-stable oscillator further comprises first and second gold plated electrodes spaced from opposing surfaces of said quartz crystal.
6. The package of claim 1 wherein said cavity is formed as a recess in at least one of said base member and said cover.
7. The package of claim 6 wherein said cavity comprises a recess formed in each of said base member and said cover.
8. The package of claim 1 wherein said thermo-compression bonding means comprises brazing of said cover to said base member using gold indium eutectic alloy at 495° C.
9. The package of claim 8 wherein said same bonding means is used to secure the piezoelectric device to at least a portion of said cavity.
10. The package of claim 1 wherein electrical contact is provided to said piezoelectric device directly through said base member or said cover member obviating need for lead wires or other electrical connectors through a wall portion of said package.
11. A hermetic package for a high performance piezoelectric device, said package comprising
a) a base member made entirely of a material selected from the group consisting of metallic silicon, titanium, zirconia, silicon carbide, sapphire, and tantalum;
b) a cover made entirely of said same material as said base member;
c) a cavity formed between said base member and said cover for receiving the electronic component, said cavity providing a high vacuum environment for the electronic component, said vacuum falling in the range between 1×10 −5 and 1×10 −11 torr;
d) thermo-compression bonding means performed at temperatures exceeding 300° C. for securing said cover directly to said base member.
12. The package of claim 11 wherein said thermo-compression bonding means is performed in a temperature range of 300° C. and 800° C.
13. The package of claim 11 wherein said piezoelectric device is an ultra-stable oscillator.
14. The package of claim 13 wherein said ultra-stable oscillator is selected from a group consisting of a quartz crystal, a gallium orthophosphate crystal, and a lithium niobate crystal.
15. The package of claim 14 wherein said ultra-stable oscillator further comprises first and second gold plated electrodes spaced from opposing surfaces of said ultra-stable oscillator.
16. The package of claim 11 wherein said cavity is formed as a recess in at least one of said base member and said cover.