Sinterable Silver Flake Adhesive for Electronics
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Solution Overview
Problem
Conductive adhesive compositions with silver flake and resin limit thermal and electrical conductivity, while nano-silver requires high heat and pressure to eliminate pores and achieve densification, posing challenges in semiconductor device assembly.
Innovation Solution
A conductive composition using micro- or submicro-sized silver flake with a solvent to dissolve surface lubricants and surfactants, combined with a liquid peroxide, sintering without an organic resin, allowing for adhesion and conductivity enhancement at lower temperatures without pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive resin is added to silver flake conductive composition, then adhesion between integrated circuit device and substrate is improved, but thermal and electrical conductance of silver is reduced
Solution Approach 1:
The invention extracts and removes the adhesive resin component from the conductive composition, using only silver flake particles. This eliminates the resin's negative impact on thermal and electrical conductance while maintaining adhesion through the silver flake's inherent adhesive properties and sintering capability.
Solution Approach 2:
The invention uses a specific solvent system (combining a carboxylic acid ester solvent and a cyclic carbonate solvent) as an intermediary to enable the silver flake to adhere properly during the sintering process without requiring organic resin, thus achieving both adhesion and high conductivity.
2Strength
If nano-silver is used as conductive agent and adhering agent, then adhesion capability is improved, but pores remain in the sintered composition requiring high heat and pressure for densification
Solution Approach 1:
The invention changes the particle size parameter from nano-scale to micro- or submicro-scale (0.5-10 μm), which reduces the surface area and allows for complete densification at lower sintering temperatures without requiring high pressure, while still achieving sufficient adhesion and eliminating pores.
Solution Approach 2:
The invention uses silver flake with specific morphology (flake shape with defined thickness and lateral dimensions) and surface characteristics (coated with lubricant or surfactant) to achieve local quality that enables both adhesion and pore-free densification at moderate sintering conditions.
3Manufacturing precision
If silver flake is sintered at high heat and pressure to eliminate pores, then densification is achieved, but manufacturing complexity and processing difficulty increase
Solution Approach 1:
The invention changes the sintering temperature parameter to a lower range (100-250°C) and eliminates the need for high pressure by using micro- or submicro-sized silver flake with specific surface properties, thereby simplifying the sintering process and reducing manufacturing complexity while achieving complete densification.
4Strength
If lubricant or surfactant is present on silver flake surface, then adhesion is improved, but sintering is hindered requiring higher temperatures
Solution Approach 1:
The invention uses a dual-solvent system (carboxylic acid ester and cyclic carbonate) as an intermediary that selectively removes lubricant or surfactant from the silver flake surface, enabling sintering at lower temperatures while preserving the adhesion benefits of the lubricant/surfactant treatment.
Solution Approach 2:
The invention performs preliminary removal of excess lubricant or surfactant from the silver flake surface before sintering using the solvent system, preparing the surface for low-temperature sintering while maintaining sufficient adhesion capability.
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 solution achieves high thermal conductivity and die shear strength in semiconductor devices, surpassing industry standards with silver flake tap densities of 4.6g/cc or higher, sintering at temperatures under 250°C, and eliminating the need for pressure.
Implementation Method 1
a solvent that dissolves any fatty acid lubricant or surfactant present on the surface of the silver
Implementation Method 2
sintering without an organic resin, allowing for adhesion and conductivity enhancement at lower temperatures without pressure
Data Source
AI summary
A conductive composition comprises (i) micro- or submicro-sized silver flake having a tap density of 4.6g/cc or higher and (ii) a solvent that dissolves any fatty acid lubricant or surfactant present on the surface of the silver. In one embodiment, (iii) a small amount of peroxide is present. No organic resin is present in the composition.