Au-Sn Alloy Layer Bonding for Electronic Components

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Solution Overview

Problem

Existing methods for joining electronic components to bonding objects, such as substrate boards, are time-consuming, costly, and require precise positioning due to the use of hard and brittle Au—Sn sheet-preforms, which complicates the bonding process and can lead to weakened adhesion and thermal conductivity.

Innovation Solution

Forming glass-containing Au layers on both surfaces of a ceramic element with an Au—Sn alloy layer, optionally with a pure-Au layer in between, allows for easy joining by heating, simplifying the bonding process and preventing surface unevenness that can reduce adhesion and thermal conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If Au—Sn sheet-preform is used for joining electronic components to bonding objects, then bonding strength can be achieved, but the process becomes complex and time-consuming due to precise positioning requirements

Engineering Contradiction:

Improvebonding strengthVSAvoidbonding process complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The bonding process is segmented into two distinct stages: first forming the Au—Sn alloy layer on the ceramic element surface, then separately positioning the Au—Sn sheet-preform on the bonding object. This segmentation eliminates the need for precise positioning of the preform between the component and bonding object simultaneously, simplifying the overall bonding process while maintaining bonding strength.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The Au—Sn alloy layer is formed in advance on the ceramic element surface through screen-printing and reflow treatment before the actual bonding operation. This preliminary action prepares the bonding surface with proper material properties, allowing subsequent simple placement of the preform without complex positioning requirements.

Inventive Principle:

Principle #10Preliminary action

2Strength

If Au—Sn sheet-preform is used for joining, then bonding can be achieved, but manufacturing cost increases due to time-consuming processes

Engineering Contradiction:

Improvebonding strengthVSAvoidmanufacturing efficiency

Core Design Contradiction:

StrengthVSProductivity

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The complex mechanical positioning system required for aligning thin preforms is replaced by a material-based bonding approach where the preform is simply placed on the pre-prepared alloy layer. The bonding success depends on material properties rather than precise mechanical alignment, significantly improving manufacturing efficiency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Strength

If Au—Sn sheet-preform is used, then bonding can be achieved, but adhesion is weakened due to hard and brittle material properties

Engineering Contradiction:

Improvebonding strengthVSAvoidadhesion reliability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The material state of the Au—Sn bonding layer is changed from solid preform-only to a combination of pre-formed alloy layer and preform. The alloy layer provides a ductile, adhesive base that compensates for the brittleness of the preform material, ensuring reliable adhesion while maintaining bonding strength.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The bonding system uses a composite structure combining the Au—Sn alloy layer (formed by screen-printing and reflow) with the Au—Sn sheet-preform. This composite approach leverages the adhesive properties of the alloy layer and the structural properties of the preform, achieving both strong bonding and reliable adhesion.

Inventive Principle:

Principle #40Composite materials

4Strength

If Au—Sn sheet-preform is used for joining, then bonding can be achieved, but thermal conductivity is reduced due to positioning difficulties and process complexity

Engineering Contradiction:

Improvebonding strengthVSAvoidthermal conductivity

Core Design Contradiction:

StrengthVSTemperature

Solution Approach 1:

The complex mechanical positioning system is replaced by a material-based bonding approach where the preform is simply placed on the pre-prepared alloy layer. This simplification ensures better contact and more consistent thermal pathways, improving thermal conductivity while maintaining bonding strength.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables easy and reliable joining of electronic components to bonding objects with improved bonding strength and thermal conductivity, reducing manufacturing costs and complexity.

Implementation Method 1

heating in a state in which the Au—Sn alloy layer is in contact with the bonding object

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

the Au—Sn alloy layer is heated to melt and then cooled to solidify

Methodology Applied

Scientific EffectSolidification: Freezing

Implementation Method 3

glass-containing Au layers formed on both surfaces of the ceramic element

Methodology Applied

Scientific EffectSintering: Sintering

Data Source

PatentUS11396164B2Electronic component and method of manufacturing electronic component

Publication Date: 2022.07.26 MITSUBISHI MATERIALS CORP

AI summary

An electronic component includes a ceramic element, glass-containing Au layers formed on both surfaces of the ceramic element, and an Au—Sn alloy layer formed on at least one of the glass-containing Au layers; the electronic component further includes a pure-Au layer between the glass-containing Au layer and the Au—Sn alloy layer; furthermore, the Au—Sn alloy layer has an Au—Sn eutectic structure.