MEMS Device Isolation via Segmented Base Cavities

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Solution Overview

Problem

Microelectromechanical Systems (MEMS) devices face performance degradation due to strain forces resulting from differences in thermal expansion coefficients between the rigid housing structure and the MEMS device, necessitating effective isolation from packaging forces.

Innovation Solution

A MEMS package design featuring a housing with a cavity and a MEMS device where the MEMS sensor is supported by a base with two isolated support structures, utilizing cavities and posts to decouple the sensor from external forces, with attachment mechanisms like gold stud bumps or epoxy securing the posts to the housing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the MEMS device is attached to a rigid housing structure, then the MEMS device is securely mounted and structurally supported, but strain forces are transmitted to the MEMS sensor due to differences in coefficients of thermal expansion, degrading sensor performance

Engineering Contradiction:

Improvestructural supportVSAvoidsensor performance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The base structure is segmented into multiple regions: a first support device region that directly supports the MEMS sensor, and a second support device region that is physically isolated from the first support device by cavities. This segmentation allows the second support device to be attached to the rigid housing while the first support device remains isolated from transmission forces.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Cavities are introduced as intermediary spaces between the first support device and the second support device. These cavities act as mediators that physically decouple the two support regions, preventing direct transmission of strain forces from the rigid housing to the MEMS sensor while still allowing the structure to be mounted securely.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the MEMS device is directly bonded to the housing, then the device complexity is reduced and manufacturing is simplified, but the MEMS sensor is exposed to external forces and structural deformations

Engineering Contradiction:

Improvepackaging structureVSAvoidexternal forces on sensor

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The base is divided into functionally distinct support devices: a first support device collocated with the sensor for precise positioning, and a second support device for structural attachment to the housing. This segmentation creates a modular structure that balances complexity with protection.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The harmful transmission path is extracted by removing direct physical connection between the sensor support region and the housing attachment region. Cavities are created to take out the direct bonding path, thereby eliminating the transmission of harmful forces while maintaining the necessary support functions.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If isolation structures are added to protect the MEMS sensor from thermal expansion forces, then sensor performance is improved, but the device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improvesensor performanceVSAvoidpackaging fabrication

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The isolation function is merged with the support function by integrating cavities directly into the base structure. The base simultaneously provides mechanical support through its support devices and isolation through its cavities, combining multiple functions into a single component that reduces overall packaging complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The base structure is designed as a multi-functional component that simultaneously serves as: (1) a mounting platform for the MEMS device, (2) a support structure with isolated regions, (3) an isolation mechanism through cavities, and (4) a thermal management element. This multi-functionality reduces the need for separate isolation components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 design effectively isolates the MEMS sensor from structural deformations and forces, enhancing its performance by limiting external influences to external device portions, thereby improving the reliability and accuracy of the MEMS device.

Implementation Method 1

A MEMS device is bonded within the cavity

Methodology Applied

Scientific EffectBonding: Adhesive

Data Source

PatentUS7280262B1Integrated die level isolation for a MEMS device

Publication Date: 2007.10.09 HONEYWELL INTERNATIONAL INC

AI summary

A Microelectromechanical Systems (MEMS) package having a housing and a MEMS device bonded within the cavity of the housing. The MEMS device includes a MEMS sensor and a base connected to the MEMS sensor at a first surface. The base includes a first support device that is collocated with the MEMS sensor and a second support device is partially physically isolated from the first support device. An attachment device attaches the second support device to a base surface of the housing. The second support device is isolated from the first support device by one or more cavities. The second support device includes a plurality of posts located adjacent to edges of the base. The plurality of posts include four corner posts and four side posts, each of the four corner posts are separated from two of the four side posts by two of the cavities.