Epoxy Underfill Composition for Fast Filling and Crack Resistance
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Solution Overview
Problem
The post-application method for underfill materials in semiconductor chip packages faces challenges with long filling times and potential failure due to thermal stress, especially for large or multiple die packages, requiring materials with improved flowability and crack resistance.
Innovation Solution
An underfill material comprising an epoxy resin with multiple epoxy groups, a compound with functional groups capable of reacting with the epoxy resin, and an inorganic filler, which reduces viscosity and enhances crack resistance, allowing for faster filling and superior cured product properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the post-application method is used to fill the gap with underfill material, then the bonding portion is protected from external environment, but the filling time becomes excessively long for large or multiple die packages
Solution Approach 1:
The patent modifies the chemical composition parameters of the underfill material by incorporating a silane-modified epoxy resin with specific molecular structure and crosslinking density. This parameter change reduces the viscosity and increases the flow rate of the material, enabling it to fill large gaps quickly through capillary action while maintaining protective functions
Solution Approach 2:
The invention uses a composite underfill material system combining silane-modified epoxy resin, inorganic fillers, and curing agents. This composite formulation achieves optimal balance between flowability (for fast filling) and mechanical properties (for crack resistance and protection), resolving the time-protection contradiction
2Area of stationary object
If the package size is increased to 900 mm² or more, then the semiconductor chip package can accommodate larger dies, but the underfill material is subjected to increased thermal stress causing failure cracks
Solution Approach 1:
The patent changes the molecular structure parameters of the epoxy resin to include silane modification with specific crosslinking groups. This structural parameter change enhances the elastic modulus and tensile strength of the cured underfill material, enabling it to withstand the increased thermal stress in large area packages without developing failure cracks
Solution Approach 2:
The invention formulates the underfill material with specific thermal expansion characteristics that match the semiconductor chip and substrate. This thermal expansion matching reduces thermal stress differential during temperature cycling, preventing crack formation in large area packages while maintaining structural integrity
3Productivity
If the underfill material has high flowability to shorten filling time, then the filling speed increases, but the cured product may exhibit excessive fillet area formation
Solution Approach 1:
The patent optimizes the viscosity parameters of the underfill material through controlled silane modification and filler content. This parameter optimization creates a viscosity profile that provides sufficient flowability for rapid capillary filling while limiting excessive material displacement that causes large fillet formation, achieving balance between filling speed and shape control
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 underfill material achieves a short filling time and provides a cured product with enhanced crack resistance and thermal stability, suitable for large die and multiple die packages, reducing the risk of thermal stress-induced failures.
Implementation Method 1
a compound having a functional group that is capable of reacting with the epoxy group of the component (A)
Implementation Method 2
a post-application method (capillary underfill method), in which the gap is filled with the underfill material
Data Source
AI summary
Underfill materials including (A) an epoxy resin having two or more epoxy groups per one molecule thereof, (B) a compound having a functional group capable of reacting with the epoxy group of the component (A) and an ethylenic unsaturated group, and (C) an inorganic filler, are afford a cured product having a short filling time and a superior crack resistance.