Silver Paste Composition for Low-Temperature Sintered Bonding
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Solution Overview
Problem
Existing pressurized-type sintering materials for bonding wide band gap semiconductor elements require high temperatures, which can cause damage to peripheral members and deteriorate connection reliability due to residual stress and thermal expansion, necessitating a low-temperature bonding solution with high adhesive strength and resistance to cooling and heating cycles.
Innovation Solution
A paste composition comprising silver particles with specific size and crystallite size distribution, along with a binder, allowing for heat-and-pressure bonding at low temperatures (180-300°C and 1-30 MPa) to achieve high adhesive strength and minimize detachment during thermal cycles, using a formulation that enhances sinterability and reduces structural changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high temperature heating (250°C or greater) is performed during bonding, then connection reliability is improved through dense sintered body formation, but damage to peripheral members occurs and residual stress increases
Solution Approach 1:
The patent changes the bonding temperature parameter from conventional high temperatures (250°C or greater) to a lower temperature range (100°C to 200°C). This parameter change enables achieving dense sintered body formation and high connection reliability without causing damage to peripheral members or excessive residual stress, thus resolving the technical contradiction between reliability improvement and harm reduction.
2Reliability
If high temperature heating (250°C or greater) is performed during bonding, then dense sintered body is formed improving connection reliability, but residual stress from thermal expansion deteriorates connection reliability
Solution Approach 1:
The patent reduces the bonding temperature parameter to 100°C to 200°C, which eliminates the thermal expansion differential that causes residual stress while still achieving dense sintered body formation through the specific paste composition and pressurization conditions. This resolves the contradiction between forming dense sintered bodies for reliability and avoiding residual stress that deteriorates reliability.
3Object-affected harmful factors
If low temperature bonding (200°C) is performed, then damage to peripheral members is reduced, but adhesive strength is insufficient
Solution Approach 1:
The patent uses a composite paste composition containing silver particles (5-20 μm), glass particles (3-10 μm), and organic vehicle, which enables low temperature bonding at 200°C while achieving sufficient adhesive strength. The composite material formulation allows dense sintered body formation and strong adhesion without requiring high temperatures, thus resolving the contradiction between reducing damage and maintaining strength.
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 paste composition enables reliable bonding with high thermal conductivity and conductivity, minimizing detachment and structural changes, while maintaining high adhesive strength and reducing thermal stress.
Implementation Method 1
The fine metal particles are sintered at a temperature significantly lower than the melting point of the metal itself, and the sintered fine metal particles can acquire thermal conductivity and heat resistance equivalent to those of bulk metal.
Implementation Method 2
a binder (B)
Implementation Method 3
subjecting the dried product of the paste composition to a heating and pressurizing treatment at 15 MPa and 200°C for 2 minutes under a nitrogen atmosphere
Data Source
AI summary
Disclosed is a paste composition containing silver particles (A) and a binder (B), in which the silver particles (A) contain 5 mass% or less of silver particles (A1) having a particle size greater than 20 µm with respect to 100 mass% of the silver particles (A), the silver particles (A) account for 95 mass% or greater with respect to 100 mass% of a total amount of the silver particles (A) and the binder (B), and a change rate represented by Formula (1) is 250% or greater: changerate=S1−S0/S0×100% where S0 is a crystallite size at a Miller index (111) of silver particles in a dried product of the paste composition, and S1 is a crystallite size at Miller index (111) of silver particles in a treated product obtained by subjecting the dried product of the paste composition to a heating and pressurizing treatment at 15 MPa and 200°C for 2 minutes under a nitrogen atmosphere.