MEMS Footprint Isolation via PCB Segmentation and Bridges

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Solution Overview

Problem

MEMS devices attached to printed circuit boards (PCBs) are sensitive to mechanical and thermal stresses, leading to erroneous readings and the need for frequent calibration, especially in non-hermetic plastic packages, due to strong mechanical connections that transfer stress from the PCB to the MEMS device.

Innovation Solution

A system comprising two PCB regions with isolation channels and bridges is used to mechanically isolate the MEMS device footprint from potential stress sources, allowing for the removal of PCB material within the isolation channels to reduce stress transfer, while maintaining electrical connectivity through bridges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If solder is used to couple package connectors to PCB conductors, then electrical connection reliability is improved, but mechanical stress transfer to MEMS device increases

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidmechanical stress transfer

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The PCB is divided into two separate regions: a first region containing the MEMS device footprint and a second region containing stress sources. An isolation channel physically separates these regions, preventing mechanical stress transfer while maintaining electrical connectivity through bridges.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Bridges are introduced as intermediary structures that span the isolation channel. These bridges provide electrical connectivity between the two PCB regions while being designed to minimize mechanical stress transfer to the MEMS device footprint.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If strong mechanical connection is provided between package and PCB, then mechanical stability is improved, but stress transfer to MEMS device increases

Engineering Contradiction:

Improvemechanical connection strengthVSAvoidstress transfer

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The PCB structure is segmented into isolated regions using isolation channels, allowing strong mechanical connections within each region while preventing stress transfer between regions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Bridges serve as intermediary elements that maintain mechanical stability of the overall structure while being designed to decouple stress paths from the MEMS device footprint.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If PCB material is removed in isolation channel, then mechanical isolation is improved, but structural integrity may be compromised

Engineering Contradiction:

Improvemechanical isolationVSAvoidPCB structural integrity

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

Bridges are strategically placed to span the isolation channel, providing necessary structural support and maintaining PCB integrity while allowing the isolation channel to prevent stress transfer.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The PCB structure is designed with different local properties: the isolation channel region has removed material for stress isolation, while the bridge regions maintain full structural integrity to support the overall board.

Inventive Principle:

Principle #3Local quality

Data Source

PatentEP2135839B1Method and apparatus for improving measurement accuracy of MEMS devices

Publication Date: 2018.11.21 GARMIN SWITZERLAND GMBH

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AI summary

A system for improving the performance of a microelectromechanical systems (MEMS) device that is housed in a package and implemented on a printed circuit board (PCB) comprises a footprint, an isolation channel, and a bridge. A portion of the isolation channel is removed to mechanically isolate the MEMS device.