Stress Buffer Layer for MEMS Packaging

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Solution Overview

Problem

The increasing demand for compact, high-performance semiconductor packages with enhanced circuit density and precision in microelectromechanical systems (MEMS) devices poses challenges due to mechanical interactions and sensitivity to mechanical and thermo-mechanical stresses, which affect the accuracy and sensitivity of MEMS components.

Innovation Solution

The introduction of a stress buffer layer with a Young's modulus lower than the mold compound, typically made of materials like polyimide, epoxy, or silicone, is used between MEMS components to prevent mechanical interactions and reduce stress, allowing for compatibility and improved packaging efficiency in embedded wafer level ball grid array (eWLB) technology.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If MEMS components are placed side-by-side or stacked in compact packaging, then packaging density is improved, but mechanical interactions and stresses increase, reducing MEMS accuracy and sensitivity

Engineering Contradiction:

Improvepackaging densityVSAvoidMEMS accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

A buffer layer is introduced as an intermediary element between the MEMS component and the mold compound. This buffer layer has a lower Young's modulus than the mold compound, creating a mechanical decoupling that isolates the MEMS component from stress transmitted by the mold compound, thereby maintaining MEMS accuracy while enabling compact packaging

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the mechanical parameter (Young's modulus) of the buffer layer to be lower than that of the mold compound. This parameter change creates a compliant interface that absorbs and distributes mechanical stresses, preventing stress concentration at the MEMS-mold interface and maintaining device performance in compact packages

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If additional functionality is added to semiconductor packages, then device capability is improved, but space availability decreases, creating structural issues

Engineering Contradiction:

Improvedevice capabilityVSAvoidspace availability

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

The patent enables three-dimensional stacking of MEMS components vertically rather than only lateral placement. By utilizing the vertical dimension and introducing buffer layers between stacked components, the design achieves additional functionality without proportionally increasing the package footprint, thus maintaining space efficiency

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Volume of moving object

If compact packaging is implemented, then package size is reduced, but mechanical stresses increase, affecting MEMS performance

Engineering Contradiction:

Improvepackage sizeVSAvoidmechanical stress

Core Design Contradiction:

Volume of moving objectVSStress or pressure

Solution Approach 1:

The buffer layer serves as a mechanical intermediary that absorbs and distributes stresses generated by compact packaging. Its lower Young's modulus compared to the mold compound allows it to deform elastically under stress, preventing stress transmission to the MEMS component and maintaining device performance in reduced-size packages

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The stress buffer layer effectively reduces mechanical interactions between MEMS components, enhancing the accuracy and sensitivity of MEMS devices by providing a compatible and stress-reducing interface, facilitating high-density packaging and improved assembly processes.

Implementation Method 1

a buffer layer having a first Young's modulus, a mold compound having a second Young's modulus higher than the first Young's modulus

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS9056763B2Stress buffer layer for integrated microelectromechanical systems (MEMS)

Publication Date: 2015.06.16 GOOGLE LLC

AI summary

Stress buffer layers for integrated microelectromechanical systems (MEMS) are described. For example, a semiconductor package includes a substrate having first and second surfaces, the second surface having an array of external conductive contacts. A microelectromechanical system (MEMS) component is disposed above the first surface of the substrate. A buffer layer is disposed above the MEMS component, the buffer layer having a first Young's modulus. A mold compound is disposed above the buffer layer, the mold compound having a second Young's modulus higher than the first Young's modulus.