Stacked-Die MEMS Resonator Packaging for Thermal Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge lies in developing a chip package for MEMS and NEMS resonator systems that can replace conventional packaged timing references, addressing size, cost, and reliability issues, particularly for applications where quartz and other types of packaged timing references are impractical.
Innovation Solution
A packaging structure for electromechanical resonator systems, featuring a control chip and a second chip mounted in a stacked die configuration, thermally coupled by a conductive epoxy, providing a small package footprint, low thermal resistance, and a robust electrically conductive path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If quartz resonators decrease in size to meet size constraints, then the size is reduced, but the unit cost increases and reliability decreases
Solution Approach 1:
The patent uses MEMS resonators as a copy/alternative to traditional quartz resonators. MEMS devices are fabricated using semiconductor manufacturing processes on silicon substrates, creating a comparable resonating structure that can be miniaturized without the same reliability penalties as quartz. This copying approach allows size reduction while maintaining or improving reliability through robust semiconductor fabrication.
Solution Approach 2:
The patent replaces the mechanical cutting and sealing processes used for quartz resonators with semiconductor fabrication processes. Instead of mechanically cutting quartz crystals and forming hermetic seals, the invention uses photolithography, deposition, and other semiconductor manufacturing techniques to create MEMS resonators, eliminating the reliability issues associated with mechanical processing at small scales.
2Volume of moving object
If quartz resonators decrease in size, then the size is reduced, but the unit cost increases
Solution Approach 1:
The patent copies the resonator function from quartz to MEMS technology, which benefits from established semiconductor manufacturing economies of scale. By fabricating multiple MEMS resonators on a single silicon wafer using standard semiconductor processes, the unit cost decreases as production volume increases, unlike quartz resonators where smaller sizes require more complex and expensive manufacturing steps.
Solution Approach 2:
The patent changes the material parameter from quartz to silicon and the fabrication methodology from mechanical processing to semiconductor processing. This parameter change enables the use of high-volume, low-cost semiconductor manufacturing techniques, including batch processing of multiple devices on a wafer, which significantly reduces unit cost compared to individual quartz resonator fabrication.
3Reliability
If MEMS resonators are used to replace quartz, then cost and reliability improve, but thermal management becomes critical
Solution Approach 1:
The patent introduces a thermally conductive epoxy as an intermediary material between the MEMS resonator chip and the substrate. This epoxy serves as a thermal pathway, efficiently conducting heat away from the resonator to prevent temperature-induced frequency drift and maintain stable operation. The intermediary thermal interface material solves the thermal management challenge while preserving the reliability advantages of MEMS technology.
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
Enables the use of MEMS packaged timing references in various electronic devices, offering cost-effective, reliable, and compact alternatives to quartz and other types of packaged timing references.
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.