Stress Isolated MEMS Package with Trench and Ring Structure
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Solution Overview
Problem
Current MEMS pressure sensor packaging faces challenges due to the need for smaller size, low cost, and fragility, with existing methods using costly materials and susceptible to parasitic capacitance in bond wires, and requiring significant gel usage for environmental protection.
Innovation Solution
A stress-isolated MEMS package design featuring a trench surrounding the sensor region and a shallow backside cavity, combined with a ring structure for lateral and vertical stress isolation, and an overmolded package that encapsulates bond wires, allowing for reduced gel usage and improved reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional packaging methods are used for MEMS pressure sensors, then environmental protection is achieved, but package size increases and cost increases
Solution Approach 1:
The package structure is segmented into distinct functional regions: a first cavity for the sensor, a second cavity for bonding wires, and a third cavity for gel material. This segmentation allows each component to be optimized independently, reducing overall package size while maintaining environmental protection functionality.
Solution Approach 2:
The patent implements nested cavities where the first cavity (sensor region) is surrounded by the second cavity (bonding wire region), which is in turn surrounded by the third cavity (gel material region). This nested structure maximizes space utilization and reduces package size while providing multiple layers of environmental protection.
2Reliability
If traditional packaging methods are used for MEMS pressure sensors, then environmental protection is achieved, but manufacturing cost increases
Solution Approach 1:
The package is divided into three distinct cavities with specific functions, allowing for optimized material usage and simplified manufacturing processes. The segmentation enables standard packaging methodologies to be used while reducing material costs.
Solution Approach 2:
The patent eliminates the need for costly stress isolation materials by using the molded compound body itself to provide mechanical support and stress isolation. This discards traditional expensive materials while maintaining the same protective function.
3Ease of operation
If bond wires are exposed in traditional packages, then electrical connection is achieved, but parasitic capacitance increases
Solution Approach 1:
The bonding wires are placed within the second cavity that is nested between the first and third cavities. This nested positioning allows the bonding wires to be electrically connected while surrounded by gel material that reduces parasitic capacitance effects.
Solution Approach 2:
The gel material in the third cavity acts as an intermediary between the bonding wires and the external environment, reducing parasitic capacitance while maintaining electrical connection functionality. The molded compound body also serves as an intermediary providing mechanical support.
4Reliability
If significant gel usage is employed in traditional packages, then environmental protection is improved, but package complexity increases
Solution Approach 1:
The gel material is confined to a specific third cavity region, separating its environmental protection function from other package functions. This segmentation simplifies the overall package design by giving each material a dedicated functional zone.
Solution Approach 2:
The molded compound body serves multiple functions: it provides mechanical support, acts as a mold for creating cavities, provides stress isolation, and encapsulates bonding wires. This multi-functionality reduces package complexity by eliminating the need for separate components.
Data Source
AI summary
A device package includes a die that includes a substrate having first and second surfaces. A sensor is formed at a sensor region of the first surface. A trench extends entirely through the substrate between the first and second surfaces, in which the trench at least partially surrounds the sensor region. An isolation material, formed at the first surface, may extend across the trench A ring structure is coupled to the first surface of the substrate to create a first cavity in which the sensor is contained, the ring structure being laterally displaced away from and surrounding the sensor region and the trench. A molded compound body may abut an outer wall of the ring structure. The molded compound body has a second cavity that is concentric with the first cavity to enable fluid communication between the sensor and an environment external to the device package.