Stacked die package for MEMS resonator system
A stacked die package for an electromechanical resonator system includes a chip that contains an electromechanical resonator bonded onto the control chip for the electromechanical resonator by a thermally and/or electrically conductive epoxy. In various embodiments, the electromechanical resonator can be a micro-electromechanical system (MEMS) resonator or a nano-electromechanical system (NEMS) resonator. Packaging configurations that may include the chip that contains the electromechanical resonator and the control chip include chip-on-lead (COL), chip-on-paddle (COP), and chip-on-tape (COT) packages. The stacked die package provides small package footprint and/or low package thickness, as well as low thermal resistance and a robust conductive path between the chip that contains the electromechanical resonator and the control chip.
1. A packaging structure for an electromechanical resonator system, the packaging structure comprising:
a control chip for a microelectromechanical resonator;
an electromechanical resonator chip that (i) includes the microelectromechanical resonator and (ii) is mounted on the control chip in a stacked die configuration, wherein the electromechanical resonator chip is physically coupled to the control chip by a thermally conductive epoxy;
a lead frame including at least one electrical lead having a mounting surface and an electrical contact surface, wherein the stacked die configuration is mounted on and physically coupled to the mounting surface of the electrical lead, and wherein the stacked die configuration is electrically coupled to the electrical lead; and
a mold compound, enclosing at least a portion of the lead frame and stacked die configuration of the control chip and the electromechanical resonator chip, wherein (i) the mounting surface of the electrical lead and the portion of the stacked die configuration which is mounted thereon are enclosed in the mold compound and (ii) the electrical contact surface of the electrical lead is externally exposed.
2. The packaging structure of claim 1 , wherein the bulk layer of the electromechanical resonator chip is bonded to a passivation layer of the control chip via the thermally conductive epoxy.
3. The packaging structure of claim 2 , wherein the thermally conductive epoxy has a coefficient of thermal expansion that is substantially equal to a coefficient of thermal expansion of a base material of the control chip and/or a base material of the electromechanical resonator chip.
4. The packaging structure of claim 1 , wherein the at least one electrical lead is wirebonded to the control chip.
5. The packaging structure of claim 1 , wherein the lead frame includes a plurality of electrical leads, wherein each lead has an exposed electrical contact surface positioned on an external surface of the packaging structure.
6. The packaging structure of claim 1 , further including a first electrically conductive bonding wire, disposed within the mold compound, to electrically couple circuitry disposed on or in the control chip to the electromechanical resonator of the electromechanical resonator chip.
7. The packaging structure of claim 6 , further including:
a second electrically conductive bonding wire disposed within the mold compound, and
wherein the second electrically conductive bonding wire electrically couples the control chip and the portion of the at least one electrical lead that is disposed in the mold compound.
8. The packaging structure of claim 1 , wherein a first surface of the control chip resides on the mounting surface of the at least one electrical lead and is bonded thereto via electrically insulating epoxy.
9. The packaging structure of claim 8 , wherein the electromechanical resonator chip is attached to a second surface of the control chip via the thermally conductive epoxy.
10. The packaging structure of claim 9 , wherein the electromechanical resonator chip is electrically coupled to the control chip via a first bonding wire and wherein the first bonding wire is disposed within the mold compound.
11. The packaging structure of claim 10 , wherein the control chip is electrically coupled to the lead frame via a second bond wire.
12. The packaging structure of claim 1 , wherein the control chip includes a temperature sensor.
13. The packaging structure of claim 12 , wherein the control chip compensates for changes in temperature of the microelectromechanical resonator using data from the temperature sensor.
14. The packaging structure of claim 13 , wherein the thermally conductive epoxy thermally couples the electromechanical resonator chip to the control chip such that the temperature sensor generates data which is representative of the temperature of the electromechanical resonator chip.
15. The packaging structure of claim 14 , wherein a first surface of the control chip resides on the mounting surface of the at least one electrical lead and is bonded thereto via electrically insulating epoxy.
16. The packaging structure of claim 15 , wherein the electromechanical resonator chip is attached to a second surface of the control chip via the thermally conductive epoxy.
17. The packaging structure of claim 16 , wherein the electromechanical resonator chip is electrically coupled to the control chip via a first bonding wire and wherein the first bonding wire is disposed within the mold compound.
18. The packaging structure of claim 1 , wherein:
the control chip includes a temperature sensor and circuitry to compensate for changes in temperature of the microelectromechanical resonator using data from the temperature sensor; and
the thermally conductive epoxy thermally couples the microelectromechanical resonator to the temperature sensor such that the temperature sensor generates data which correlates to the temperature of the microelectromechanical resonator.
19. The packaging structure of claim 1 , further including an electrically insulating material disposed between the stacked die configuration and the mounting surface of the electrical lead.
20. The packaging structure of claim 1 , wherein the electrical contact surface of the electrical lead is an externally exposed portion of the packaging structure.