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 an electrically 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 (i) mounted on the mounting surface of the electrical lead and (ii) physically coupled thereto by an electrically insulating epoxy, 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 the 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 an externally exposed portion of the packaging structure.
2. The packaging structure of claim 1 , wherein the control chip includes a passivation layer disposed thereon and wherein a portion of a peripheral surface of the control chip not including the passivation layer contains at least a portion of the electrically conductive epoxy which electrically couples the control chip to the electromechanical resonator chip.
3. The packaging structure of claim 1 , wherein the electrically conductive epoxy has an electrical resistivity of less than about ten Megaohms.
4. The packaging structure of claim 1 , wherein the electrically conductive epoxy electrically couples portions of the control chip to the electromechanical resonator chip.
5. The packaging structure of claim 4 , wherein the bulk layer of the electromechanical resonator chip is bonded to a passivation layer of the control chip by the electrically conductive epoxy.
6. The packaging structure of claim 5 , wherein the electrically conductive epoxy electrically couples the electromechanical resonator chip to the control chip via apertures in the passivation layer of the control chip.
7. The packaging structure of claim 1 , wherein the at least one electrical lead is wirebonded to the control chip.
8. The packaging structure of claim 7 , wherein the control chip has a first surface coupled to the electromechanical resonator chip and a second surface that comprises a portion of an external surface of the packaging structure.
9. The packaging structure of claim 1 , wherein the lead frame includes a plurality of electrical leads, wherein each conductive lead has an exposed electrical contact surface positioned on the external surface of the packaging structure.
10. The packaging structure of claim 1 , wherein the packaging structure has a cross-sectional profile having a height of less than 350 μm.
11. The packaging structure of claim 1 , wherein the packaging structure has a footprint that is equal to or less than 3.2 mm 2 .
12. The packaging structure of claim 11 , wherein the footprint has a length that is equal to or less than 2.0 mm and a width that is equal to or less than 1.6 mm.
13. 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.
14. The packaging structure of claim 13 , 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 electrical lead that is disposed in the mold compound.
15. The packaging structure of claim 1 , wherein the control chip includes a temperature sensor.
16. The packaging structure of claim 15 , wherein the control chip compensates for changes in temperature of the microelectromechanical resonator using data from the temperature sensor.