Functionalized Silica Nanoparticles in Epoxy Underfill
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Solution Overview
Problem
Existing epoxy resins used in integrated circuit assemblies fail to provide a cured underfill material with a low coefficient of thermal expansion (CTE) without increasing manufacturing challenges, such as viscosity issues and filler particle trapping, which affects the reliability of solder interconnections, especially in high-temperature applications.
Innovation Solution
A curable composition comprising a thermosettable resin system with functionalized nanoscopic silica particles and a polyepoxide having at least three epoxide groups, along with a cross-linking agent and catalyst, is used to form a thermoset resin with a low CTE and high glass transition temperature, suitable for underfilling electronic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If CTE-reducing fillers are added to epoxy resin to achieve low CTE, then the coefficient of thermal expansion is reduced, but the viscosity increases which impedes flow and distribution
Solution Approach 1:
The patent changes the particle size parameter of the filler from conventional micrometer-scale to nanometer-scale (1-100 nm). This parameter change reduces the specific surface area and total surface area of fillers, thereby reducing the overall viscosity increase while maintaining the CTE-reducing effect. The nanoscale particles provide equivalent CTE reduction with minimal impact on flow properties.
Solution Approach 2:
The patent creates a composite material system combining epoxy resin with functionalized nanoscopic silica particles. The functionalization of silica surface with organosilane compounds creates a composite where the nanofiller integrates seamlessly with the polymer matrix, minimizing interfacial effects that would otherwise increase viscosity. This composite approach achieves low CTE without the severe viscosity penalties of conventional filler systems.
2Stability of the object's composition
If CTE-reducing fillers are added to epoxy resin to achieve low CTE, then the coefficient of thermal expansion is reduced, but manufacturing challenges and problems increase
Solution Approach 1:
The patent changes the particle size parameter to nanometer scale, which fundamentally alters the behavior of the filler system. The ultra-fine particles distribute more uniformly and require less aggressive mixing, reducing manufacturing complexity. The functionalization parameter is also changed to improve compatibility, further simplifying the manufacturing process by eliminating dispersion issues.
Solution Approach 2:
The patent introduces organosilane compounds as intermediary substances that functionalize the silica particle surfaces. This intermediary layer improves the compatibility between the inorganic filler and organic epoxy matrix, preventing aggregation and simplifying the manufacturing process. The functionalization acts as a mediator that enables easy processing while maintaining the desired low CTE property.
3Ease of manufacture
If conventional epoxy resin is used to provide adequate flow, then the viscosity is low, but the CTE is too high to effectively mitigate differences between die and circuit board
Solution Approach 1:
The patent changes the particle size parameter to nanometer scale, which reduces the specific surface area and minimizes the viscosity increase. The functionalization parameter is also changed to improve compatibility with the epoxy matrix. These parameter changes enable the material to achieve low CTE while maintaining adequate flow properties for manufacturing.
Solution Approach 2:
The patent applies functionalization specifically to the surface of nanoscopic silica particles, creating a local quality change at the filler-matrix interface. This localized functional improvement enhances compatibility and reduces interfacial stress, allowing the material to achieve low CTE without sacrificing processability. The local quality enhancement at the nanoscale interface enables both low viscosity and low CTE.
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 a low CTE of less than 60 ppm/°C, high glass transition temperature, and improved mechanical rigidity, enhancing the reliability of solder joints and reducing manufacturing complexities in integrated circuit assemblies.
Implementation Method 1
differences between the coefficients of thermal expansion (CTE) of the circuit board and electric component can contribute to early fatigue failure of solder interconnections
Implementation Method 2
a cured composition comprising functionalized nanoscopic silica particles distributed in a thermoset resin
Implementation Method 3
The thermosettable resin comprises a polyepoxide having at least three epoxide groups per molecule
Implementation Method 4
a curable composition comprising a thermosettable resin system and functionalized nanoscopic silica particles distributed in the thermosettable resin
Implementation Method 5
high glass transition temperature
Data Source
AI summary
A themosettable material having excellent processability, and which cures to form a thermoset composition having a low coefficient of thermal expansion and a high glass transition temperature includes functionalized nanoscopic silica particles dispersed in a curable resin comprising a polyepoxide having at least three epoxide groups per molecule. The composition is useful as an underfill for flip-chip circuit assemblies.