Leadless MLCC Microphonic Noise Reduction via TLPS Bonding

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Solution Overview

Problem

Current technologies face challenges in forming reliable, high-temperature bonds for leadless multi-layered ceramic capacitors (MLCCs) that minimize microphonic noise and are compatible with lead-free and cost-effective materials, while maintaining mechanical and electrical integrity during solder reflow processes.

Innovation Solution

The use of transient liquid phase sintering (TLPS) adhesives and materials, which form conductive bonds at low initial temperatures with high secondary melting points, allowing for the creation of leadless MLCC stacks that can withstand solder reflow without compromising the attachment, and incorporating a compliant non-metallic layer for microphonic noise reduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional lead-based solders are replaced with lead-free solders, then environmental compliance is improved, but bonding temperature requirements increase and reliability deteriorates

Engineering Contradiction:

Improvebonding reliabilityVSAvoidbonding temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent changes the chemical composition parameters of the solder alloy, specifically using Sn-3.0Ag-0.5Cu-0.5Bi with controlled element ratios to achieve optimal bonding performance at reduced temperatures while maintaining lead-free compliance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite solder material combining multiple elements (Sn, Ag, Cu, Bi) where each component contributes specific properties: Sn provides base conductivity, Ag strengthens the alloy, Cu improves wetting, and Bi reduces melting point, creating a synergistic composite that resolves the temperature-reliability contradiction

Inventive Principle:

Principle #40Composite materials

2Strength

If solder fillet size is increased to improve mechanical strength, then attachment reliability is improved, but microphonic noise increases

Engineering Contradiction:

Improveattachment strengthVSAvoidmicrophonic noise

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality control by specifying precise solder fillet geometry parameters (width, height, curvature radius) that optimize the distribution of mechanical strength while minimizing the volume of solder that can vibrate and generate microphonic noise, particularly at the critical interface regions

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent incorporates dynamic characteristics by controlling the curvature and gradual transition of the solder fillet shape, which distributes stress more evenly under vibration conditions and reduces the generation of microphonic noise while maintaining attachment strength

Inventive Principle:

Principle #15Dynamics

3Reliability

If solder reflow temperature is increased to ensure complete bonding, then bonding completeness is improved, but component damage risk increases

Engineering Contradiction:

Improvebonding completenessVSAvoidcomponent damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent utilizes phase transition characteristics of the Sn-3.0Ag-0.5Cu-0.5Bi solder alloy, which exhibits a eutectic-like behavior with a relatively sharp melting range, allowing complete bonding to be achieved at a lower, more controlled reflow temperature that reduces the risk of component damage while ensuring thorough intermetallic formation

Inventive Principle:

Principle #36Phase transitions

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

TLPS technology enables the formation of robust, high-temperature bonds with improved mechanical and electrical properties, reducing microphonic noise and enabling the use of lead-free materials, thus addressing the limitations of existing bonding methods for MLCCs.

Implementation Method 1

The use of transient liquid phase sintering (TLPS) adhesives and materials, which form conductive bonds at low initial temperatures with high secondary melting points

Methodology Applied

Scientific EffectTransient liquid phase sintering: Sintering

Implementation Method 2

incorporating a compliant non-metallic layer for microphonic noise reduction

Methodology Applied

Scientific EffectVibration absorption: Damping

Data Source

PatentUS10984955B2Electronic component structures with reduced microphonic noise

Publication Date: 2021.04.20 KEMET ELECTRONICS CORP

AI summary

An electronic device is described wherein the electronic device comprises a substrate with a first conductive metal layer and a second conductive metal layer. A first microphonic noise reduction structure is in electrical contact with the first conductive metal layer wherein the first microphonic noise reduction layer comprises at least one of the group consisting of a compliant non-metallic layer and a shock absorbing conductor comprising offset mounting tabs with a space there between coupled with at least one stress relieving portion. An electronic component comprising a first external termination of a first polarity and a second external termination of a second polarity is integral to the electronic device and the first microphonic noise reduction structure and the first external termination are adhesively bonded by a transient liquid phase sintering adhesive.