Acoustic Substrate Integration for MEMS Packaging

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Solution Overview

Problem

Current micromachined microphones and speakers face challenges in compatibility with standard packaging techniques, requiring complex and costly assembly processes due to their fragility and need for separate amplifier chips, which increases manufacturing costs and reduces sensitivity.

Innovation Solution

Micromachined microphones or speakers are fabricated directly on or within laminate substrates or lead frames, allowing for integration with electronic components and packaging using standard microelectronic techniques, such as wire bonding and surface mount soldering, before further assembly, thus simplifying the packaging process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If MEMS microphones are made from silicon substrates using semiconductor microfabrication techniques, then manufacturing precision and sensitivity are improved, but device complexity and assembly difficulty increase due to fragility

Engineering Contradiction:

Improvegap precisionVSAvoidassembly complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent combines the MEMS microphone fabrication with the laminate substrate manufacturing process itself, rather than fabricating separately and assembling. The conductive layers, dielectric layers, and acoustic cavity are all formed as integrated parts of the laminate substrate through standard PCB manufacturing techniques, eliminating the need for separate MEMS device handling and assembly.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The laminate substrate serves multiple functions simultaneously: it provides the structural base, contains the acoustic cavity, forms the conductive plates, provides dielectric support, and enables electrical connections. This multi-functionality eliminates the need for separate components and simplifies the overall device architecture.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If separate amplifier chips are used for MEMS microphones, then device sensitivity is improved, but manufacturing cost and assembly complexity increase

Engineering Contradiction:

Improvemicrophone sensitivityVSAvoidassembly steps

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The amplifier circuit is integrated directly into the laminate substrate alongside the microphone elements. The same conductive traces and circuit board infrastructure that provide electrical connections for the microphone also carry the amplifier circuitry, eliminating the need for separate amplifier chips and reducing assembly steps.

Inventive Principle:

Principle #5Merging (Combining)

3Ease of manufacture

If traditional electret microphones are used, then ease of manufacture is improved, but compatibility with wave soldering manufacturing is lost

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidtemperature tolerance

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent changes the material parameters and structural design of the microphone to withstand high temperatures. By using temperature-stable conductive materials, heat-resistant dielectric layers, and a rigid laminate substrate construction, the microphone can survive wave soldering temperatures that would destroy traditional electret microphones.

Inventive Principle:

Principle #35Parameter changes

4Temperature

If MEMS devices are assembled after wave soldering, then temperature tolerance is improved, but assembly complexity and cost increase

Engineering Contradiction:

Improvewave soldering toleranceVSAvoidassembly sequence

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The microphone fabrication is merged with the laminate substrate manufacturing, allowing both to be completed before wave soldering. The microphone elements are formed as integral parts of the substrate that can withstand the soldering process, eliminating the need for post-soldering assembly.

Inventive Principle:

Principle #5Merging (Combining)

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 approach reduces the complexity and cost of assembly by integrating acoustic elements within the laminate structure or lead frame, enabling compatibility with standard packaging methods and potentially increasing sensitivity by eliminating the need for separate amplifier chips and simplifying the assembly of fragile MEMS devices.

Implementation Method 1

The vibrations of the membrane are monitored by monitoring the capacitance of the gap between the diaphragm and a conducting plate that is close to the diaphragm

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

When oscillating air pressure is present, the free-standing structures can move with the sound waves and their positions electronically detected

Methodology Applied

Scientific EffectAcoustic pressure: Sound

Data Source

PatentUS8824707B2Acoustic substrate

Publication Date: 2014.09.02 RGT UNIV OF CALIFORNIA

AI summary

A micromachined microphone or speaker embedded within, or positioned on top of, a substrate suitable for carrying microelectronic chips and components. The acoustic element converts sound energy into electrical energy which is then amplified by electronic components positioned on the surface of the substrate. Alternatively, the acoustic element may be driven by electronics to produce sound. The substrate can be used in standard microelectronic packaging applications.