Low-Temperature Silver Paste Composition for Strong Sintered Joints
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Solution Overview
Problem
The wider use of sintered silver joints is hindered by the risk of damage to integrated circuits and relatively low shear stress compared to soldered joints, along with the high cost of nano-silver particles.
Innovation Solution
A method involving ultrasonic mixing of a mixture of succinic acid, 1-butoxy-2-propanol, terpineol, ethanol, and ethylene glycol, followed by mechanical stirring, to create a silver paste with specific particle size ratios and ratios, which is then applied and pressure sintered at controlled temperatures and pressures to form high-strength sintered joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional sintering process is used, then high temperature bonding is achieved, but integrated circuits are damaged
Solution Approach 1:
The patent changes the sintering temperature parameter from traditional high temperature (961°C for bulk silver) to low temperature (200-400°C) range. This is achieved by using nano-silver particles with specific size distribution (50-150 nm and 300-600 nm) and optimizing the organic vehicle composition, allowing sintering to occur at temperatures that do not damage integrated circuits while still achieving strong bonds
2Temperature
If nano-silver particles are used, then sintering temperature is reduced, but material cost increases
Solution Approach 1:
The patent segments the silver particle population into two distinct size ranges: fine particles (50-150 nm) that facilitate low-temperature sintering and coarser particles (300-600 nm) that provide structural strength and reduce cost. This segmentation allows the use of expensive nano-particles only where needed for enabling low-temperature processing, while bulkier, cheaper particles provide the bulk of the joint material
Solution Approach 2:
The patent creates a composite silver particle system combining two different particle size ranges in a controlled mass ratio (5:1 to 1:3). This composite approach leverages the advantages of both fine particles (low-temperature sinterability) and coarse particles (cost-effectiveness and mechanical strength), achieving a balance between performance and cost
3Use of energy by moving object
If sintered silver joints are used, then thermal conductivity is improved, but shear stress decreases
Solution Approach 1:
The patent applies local quality by creating different particle density regions within the joint. The fine nano-silver particles (50-150 nm) concentrate at the bonding interfaces where they provide excellent thermal conductivity and strong adhesion, while the coarser particles (300-600 nm) form the bulk structure providing mechanical strength and shear resistance. This spatial differentiation of particle sizes optimizes both thermal performance and mechanical properties
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 method reduces preparation time, eliminates ethanol use, and enhances the reliability and strength of sintered joints, making them suitable for die attachment and increasing power density in electric vehicles cost-effectively.
Implementation Method 1
ultrasonically mixing the mixture for a first predetermined period
Implementation Method 2
pressure sintering the first component, the second component, and the silver paste
Data Source
AI summary
A method for preparing a silver paste includes creating a mixture of succinic acid, 1-butoxy-2-propanol, terpineol, ethanol, and ethylene glycol; ultrasonically mixing the mixture for a first predetermined period; adding silver particles; and mechanically stirring the mixture for a second predetermined period to create a silver paste.