Conductive Paste Sinterability Control via Silver Crystal Transformation
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Solution Overview
Problem
Existing conductive pastes for die bonding lack stable control over sinterability of silver particles due to unmanaged crystal transformation characteristics and production challenges such as uniform carbon content and volatile dispersing medium volatilization, leading to inconsistent electrical and thermal conductivity.
Innovation Solution
A conductive paste with silver particles of 0.1 to 30 μm size, adjusted XRD analysis ratios (S2/S1, L2/L1, W2/W1) for controlled sinterability, and a dispersing medium composition including glycol ether-based compounds, with optional organic compounds like epoxy resin for enhanced stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silver particles are sintered by heating to achieve excellent electrical and thermal conductivity, then conductivity is improved, but sinterability control becomes difficult due to unmanaged crystal transformation characteristics
Solution Approach 1:
The patent applies parameter changes by controlling the crystal transformation characteristics of silver particles through specific sintering temperature ranges and holding times. By managing the crystal structure transformation during sintering, the patent achieves reliable electrical and thermal conductivity while maintaining controllable sinterability. The crystal transformation parameters are optimized to ensure consistent bonding quality.
2Ease of manufacture
If carbon content is reduced to improve sinterability, then sinterability is improved, but manufacturing precision deteriorates due to difficulty in achieving uniform carbon content distribution
Solution Approach 1:
The patent applies local quality by allowing non-uniform carbon content distribution within the conductive paste. Rather than requiring uniform carbon content throughout, the patent optimizes local carbon content characteristics to achieve adequate sinterability while maintaining overall bonding quality. This approach resolves the contradiction by accepting localized variations rather than demanding global uniformity.
3Ease of manufacture
If volatile dispersing medium is completely volatilized to improve sintering, then sintering is improved, but manufacturing complexity increases due to difficulty in controlling volatilization process
Solution Approach 1:
The patent applies partial action by not requiring complete volatilization of the volatile dispersing medium. Instead of demanding 100% removal, the patent allows partial retention of the dispersing medium, which simplifies the volatilization control process while still achieving adequate sintering quality. This partial approach reduces process complexity while maintaining acceptable bonding performance.
4Strength
If silver particle size is reduced to improve bonding strength, then bonding strength is improved, but manufacturing difficulty increases due to handling and application challenges
Solution Approach 1:
The patent applies parameter changes by optimizing the particle size distribution of silver particles in the conductive paste. Rather than using exclusively fine particles for maximum strength, the patent employs a controlled particle size distribution that balances bonding strength with handling and application ease. This parameter optimization resolves the contradiction between strength and manufacturability.
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 enables stable electrical and thermal conductivity post-sintering, improving die bonding by controlling sinterability and maintaining paste viscosity, suitable for semiconductor device mounting.
Implementation Method 1
when the paste-like composition is heated to a temperature of from 100° C. to 250° C., the volatile dispersing medium is volatilized
Implementation Method 2
the spherical silver particles are sintered and are converted to solid silver having a volume resistivity of 1×10−4 Ω·cm or less and a thermal conductivity of 5 W/m·K or more
Data Source
AI summary
Provided are: a conductive paste in which sinterability of silver particles the conductive paste can be easily controlled by using silver particles having predetermined crystal transformation characteristics defined by an XRD analysis, and after a sintering treatment, excellent electrical conductivity and thermal conductivity can be stably obtained; and a die bonding method using the conductive paste.Disclosed is a conductive paste which includes silver particles having a volume average particle size of 0.1 to 30 μm as a sinterable conductive material, and a dispersing medium for making a paste-like form, and in which when the integrated intensity of the peak at 2θ=38°±0.2° in the X-ray diffraction chart obtainable by an XRD analysis before a sintering treatment of the silver particles is designated as S1, and the integrated intensity of the peak at 2θ=38°±0.2° in the X-ray diffraction chart obtainable by an XRD analysis after a sintering treatment (250° C., 60 minutes) of the silver particles is designated as S2, the value of S2/S1 is adjusted to a value within the range of 0.2 to 0.8.