MEMS Device Packaging via Vacuum Overmolding

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Solution Overview

Problem

MEMS devices face challenges in packaging due to susceptibility to damage in high-G environments and contamination, along with difficulties in accurately regulating pressure within the package cavity, which affects their performance in detecting subtle changes in motion.

Innovation Solution

A method for packaging MEMS devices that includes a MEMS die with a seal ring and bond pads aligned with a MEMS package, forming a hermetically sealed chamber using vacuum processing and inert gas backfilling, with options for bonding using soldering, eutectic bonding, or thermo-compression, to achieve robust vacuum performance and protection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional packaging methods with lid sealing are used, then hermetic seal is provided, but vacuum performance and protection in high-G environments are insufficient

Engineering Contradiction:

Improvevacuum performanceVSAvoidpackaging structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The packaging structure is segmented into a substrate containing the MEMS device and a separate overmolded encapsulant layer. This segmentation allows the encapsulant to provide enhanced vacuum sealing and high-G protection without requiring complex lid assemblies, thereby improving vacuum performance while managing structural complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The packaging employs composite materials by overmolding a polymer encapsulant onto the substrate. This composite structure combines the mechanical strength of the substrate with the sealing and protective properties of the encapsulant, achieving superior vacuum performance and high-G environment protection.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If traditional packaging methods are used, then basic protection is provided, but protection against particles, moisture and high-G damage is insufficient

Engineering Contradiction:

Improveprotection against contaminantsVSAvoidfabrication process

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The encapsulant is overmolded onto the substrate in advance, creating a pre-formed protective barrier against particles, moisture, and high-G forces. This preliminary protective action is integrated into the fabrication process, providing robust contamination protection while maintaining ease of manufacture through a single-step overmolding operation.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If robust packaging solutions with superior vacuum performance are implemented, then protection and vacuum sealing are improved, but manufacturing cost and throughput may be affected

Engineering Contradiction:

Improveprotection in high-G environmentsVSAvoidvolume throughput

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The traditional mechanical lid sealing system is replaced with a polymer overmolding process that encapsulates the substrate. This substitution eliminates complex mechanical assembly steps, providing superior high-G protection and vacuum sealing while enabling high-volume throughput through automated overmolding fabrication.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The packaging approach transitions from atmospheric pressure sealing to vacuum-compatible overmolding parameters. By controlling the overmolding process under vacuum or controlled atmosphere conditions, the method achieves superior vacuum performance and high-G protection while maintaining manufacturing efficiency and throughput.

Inventive Principle:

Principle #35Parameter changes

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 method provides superior vacuum performance and protection against high-G environments while maintaining high volume throughput and low cost, enhancing the reliability and sensitivity of MEMS devices.

Implementation Method 1

The MEMS die and MEMS package may be positioned in a vacuum chamber, where gases may be extracted to form a controlled vacuum pressure therein

Methodology Applied

Scientific EffectVacuum: Vacuum

Implementation Method 2

heat and/or pressure may be applied to secure the MEMS die to the MEMS package and to form a hermetically sealed interior chamber surrounding the MEMS device

Methodology Applied

Scientific EffectThermo-compression bonding:

Implementation Method 3

once the gases are extracted from the vacuum chamber, one or more inert gasses may be introduced or otherwise backfilled into the chamber

Methodology Applied

Scientific EffectGas backfilling:

Data Source

PatentUS7491567B2MEMS device packaging methods

Publication Date: 2009.02.17 HONEYWELL INTERNATIONAL INC

AI summary

A method of packaging a MEMS device that includes, for example, the steps of providing a MEMS die that has a MEMS device, a seal ring and bond pads disposed thereon, providing a MEMS package that has a recess, a seal ring and bond pads disposed thereon, positioning the MEMS die over the MEMS package to align the seal rings and bond pads, inserting the MEMS die and MEMS package into a vacuum chamber and evacuating gasses therefrom to form a controlled vacuum pressure therein, sealing the MEMS package and the MEMS die together at the seal rings to form a package having a hermitically sealed interior chamber and simultaneously forming electrical connections between the corresponding bond pads.