Stacked MEMS Resonator Packaging for Thermal and Electrical Coupling
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Solution Overview
Problem
Conventional quartz resonators face increased unit costs and decreased reliability as they shrink in size, making them impractical for certain applications, while MEMS resonators offer cost and performance benefits but require effective packaging solutions to replace traditional timing references.
Innovation Solution
A stacked die packaging configuration for MEMS and NEMS resonators, utilizing a control chip and a thermally coupled resonator chip in a small package with low thermal resistance and robust electrical conductivity, allowing for a compact footprint and drop-in replacement in electronic devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If quartz resonators are reduced in size to meet size constraints, then the device size decreases, but the unit cost increases and reliability decreases
Solution Approach 1:
The patent replaces traditional quartz resonators with MEMS resonators that replicate the timing reference function. MEMS resonators are fabricated using semiconductor manufacturing processes that allow for miniaturization without the reliability issues plaguing scaled-down quartz devices. The MEMS structure copies the resonant function while using different materials and fabrication methods that enable smaller sizes with maintained or improved reliability.
Solution Approach 2:
The patent transitions from quartz crystal mechanics to MEMS mechanical structures. Instead of relying on quartz crystal oscillation that becomes unreliable at small sizes, the invention uses microfabricated mechanical resonators with proof masses and suspension structures that maintain reliability at reduced dimensions. The mechanical resonance principle is preserved but implemented through a different physical system that scales better.
2Ease of manufacture
If traditional packaging is used for MEMS resonators, then manufacturing is simpler, but thermal coupling and electrical conductivity are insufficient
Solution Approach 1:
The patent combines the MEMS resonator chip with the control logic chip into a single stacked die package. The resonator chip is directly bonded to the control chip through a support structure that integrates mechanical support, thermal conduction, and electrical connection functions. This merging eliminates the need for separate packaging components and achieves superior thermal and electrical coupling while remaining manufacturable.
Solution Approach 2:
The support structure in the package serves multiple functions simultaneously: it provides mechanical support for the resonator chip, conducts heat away from the resonator to maintain frequency stability, and provides electrical conductivity for signal transmission. This multi-functional design achieves excellent thermal and electrical coupling without adding manufacturing complexity.
3Productivity
If MEMS resonators are used instead of quartz, then unit cost decreases and scalability improves, but packaging complexity increases
Solution Approach 1:
The patent employs a nested packaging structure where the MEMS resonator is fabricated within a first chip, which is then bonded to a control logic chip (second chip). The support structure nestles the first chip against the second chip, creating a compact stacked configuration. This nesting approach integrates multiple components in a space-efficient manner that manages complexity while maintaining high manufacturing scalability through standard semiconductor bonding processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This packaging solution provides a cost-effective, reliable, and compact alternative to traditional timing references, enabling the use of MEMS resonators in applications previously impractical for quartz or other packaged timing references, with improved thermal and electrical coupling and reduced size constraints.
Implementation Method 1
the second chip is thermally coupled to the control chip by a thermally conductive epoxy
Data Source
AI summary
A low-profile packaging structure for a microelectromechanical-system (MEMS) resonator system includes an electrical lead having internal and external electrical contact surfaces at respective first and second heights within a cross-sectional profile of the packaging structure and a die-mounting surface at an intermediate height between the first and second heights. A resonator-control chip is mounted to the die-mounting surface of the electrical lead such that at least a portion of the resonator-control chip is disposed between the first and second heights and wire-bonded to the internal electrical contact surface of the electrical lead. A MEMS resonator chip is mounted to the resonator-control chip in a stacked die configuration and the MEMS resonator chip, resonator-control chip and internal electrical contact and die-mounting surfaces of the electrical lead are enclosed within a package enclosure that exposes the external electrical contact surface of the electrical lead at an external surface of the packaging structure.