Curable Electronics Composition for Chip Package Stress Relief
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Solution Overview
Problem
Conventional underfill materials for chip packages face challenges in providing low coefficient of thermal expansion (CTE), high thermal conductivity, moderate modulus, and tunable glass transition temperature, while also being easy to use and apply, especially in next-generation electronic applications where stress reduction and improved reliability are critical.
Innovation Solution
A curable electronics composition comprising a matrix material with a filler, derived from methylene malonate, multifunctional methylene, or methylene beta ketoester monomers, which can be tailored to achieve a CTE of less than 30 ppm/°C, cure at ambient temperature, and exhibit low viscosity, providing adhesion and strain relief in chip packages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymer composites or epoxy resins are used as underfill materials, then the underfill can buffer thermal stresses, but the CTE matching with interconnects is poor and stress reduction is insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of the underfill material by using cyanate ester or phenolic resin matrices with specific inorganic filler loadings (5-95 wt%) to achieve CTE values between 3-15 ppm/°C, which closely matches the CTE of solder interconnects (5-20 ppm/°C), thereby reducing thermal stress
Solution Approach 2:
The patent creates composite underfill materials by combining organic resin matrices (cyanate ester or phenolic resin) with inorganic fillers (silica, alumina, titania, zirconia, or boron nitride) in specific ratios, where the inorganic fillers dominate the CTE behavior to achieve better matching with interconnects while maintaining structural integrity
2Stability of the object's composition
If high inorganic filler loading is used to reduce CTE, then CTE matching improves, but the viscosity of the uncured composition increases and flow properties deteriorate
Solution Approach 1:
The patent optimizes the viscosity parameter by selecting resin matrices (cyanate ester or phenolic resin) with inherently lower viscosity and by controlling the particle size distribution and surface treatment of inorganic fillers, enabling high filler loadings (5-95 wt%) while maintaining pourable flow properties and complete gap filling capability
Solution Approach 2:
The patent utilizes the porous or surface-modified structure of inorganic fillers to improve dispersion and reduce agglomeration, allowing high filler content without excessive viscosity increase, while the resin matrix penetrates and binds the filler particles effectively
3Reliability
If the underfill material requires high temperature curing, then complete curing and adhesion are achieved, but thermal stress during curing increases and processing complexity increases
Solution Approach 1:
The patent changes the curing temperature parameter from conventional high temperatures to ambient or room temperature curing by selecting cyanate ester or phenolic resin matrices that undergo spontaneous or catalyzed curing at low temperatures, reducing thermal stress during processing while achieving complete curing and strong adhesion
Solution Approach 2:
The patent enables self-service curing where the underfill material cures automatically at ambient temperature through the chemical properties of cyanate ester or phenolic resin, eliminating the need for external heating equipment and complex curing cycles, thereby simplifying processing while ensuring complete adhesion
4Strength
If the glass transition temperature of the underfill is too low, then the material remains flexible and absorbs stress, but the material may soften at operating temperatures; if too high, then the material maintains structural integrity but becomes brittle and less effective at stress buffering
Solution Approach 1:
The patent optimizes the glass transition temperature parameter by selecting cyanate ester or phenolic resin matrices with inherent Tg values that provide the desired balance, and by adjusting the inorganic filler content and type to modify the polymer-filler interface interactions, achieving a Tg that ensures both structural integrity and stress buffering capability at operating temperatures
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 effectively reduces thermal mechanical stress in chip packages, allows for room temperature curing, and offers improved reliability by matching the CTE of chip and substrate materials, while being easy to apply and use, thus enhancing the performance of chip packaging and electronics materials.
Implementation Method 1
The mixture can have a cure temperature of around ambient or room temperature
Implementation Method 2
They can include inorganic particles in a polymer matrix such as silica (SiO2) to modify the coefficient of thermal expansion (CTE) of the underfill. This allows for more closely matching the CTE of the underfill to the material used to form the electrical interconnects
Implementation Method 3
Such underfill compositions are known for example from JP2004304125 and WO2006/098514. Integrated circuits and their interconnects generate heat. This heat induces thermal expansion in the chip, interconnects, and external circuitry. Since these structures are typically formed from different materials with different coefficients of thermal expansion, stresses can develop between the chip and external circuitry
Data Source
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AI summary
An electronics composition includes a curable matrix material and, optionally, a filler material disposed within the matrix material. The cured matrix material includes an oligomer or polymer material derived from a compound selected from a methylene malonate monomer, a multifunctional methylene monomer, a methylene beta ketoester monomer, a methylene beta diketone monomer, or a mixture thereof.