Resin Composition for Low Thermal Expansion PCBs
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Solution Overview
Problem
Conventional methods for reducing thermal expansion in printed circuit boards and semiconductor packages face limitations, particularly in achieving low thermal expansion while maintaining high copper foil peel strength and moldability, and are prone to degradation in heat resistance and reliability.
Innovation Solution
A resin composition incorporating a thermosetting resin, a functional group-modified copolymer, and an inorganic filler, where the functional group-modified copolymer has alkyl (meth)acrylate units modified with epoxy, carboxyl, or amide groups, is used to achieve a low coefficient of thermal expansion and improved copper foil peel strength, along with specific ratios and contents of maleimide, cyanic acid ester, and epoxy resins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high incorporation of filler or inorganic filler with high elastic modulus is used to increase rigidity, then rigidity increases, but moldability degrades and coefficient of thermal expansion increases
Solution Approach 1:
The patent changes the chemical composition parameters of the resin system by introducing a specific copolymer with carboxyl or amide groups that can form hydrogen bonds. This chemical parameter change increases rigidity through molecular interactions rather than physical filler incorporation, thereby maintaining moldability while achieving the desired rigidity increase.
Solution Approach 2:
The patent replaces the mechanical reinforcement approach (adding inorganic fillers like alumina to increase rigidity) with a chemical approach (using hydrogen bonding between copolymer chains). This substitution eliminates the need for heavy filler loading, preserving both moldability and achieving the rigidity increase through molecular-level interactions.
2Strength
If inorganic filler such as alumina is used to increase rigidity, then rigidity increases, but coefficient of thermal expansion increases, preventing sufficient warp suppression
Solution Approach 1:
The patent changes the resin composition to include a copolymer with specific functional groups that form hydrogen bonds, creating a molecular network that provides rigidity without the high thermal expansion associated with inorganic fillers. This chemical composition change achieves both rigidity increase and low thermal expansion simultaneously.
3Strength
If Tg increase method is used to improve elastic modulus in reflow, then warp suppression improves, but heat resistance after moisture absorption degrades due to increased crosslink density or void formation
Solution Approach 1:
The patent changes the crosslinking mechanism by using hydrogen bonding through carboxyl or amide groups instead of dense covalent crosslinking. This parameter change in the bonding mechanism achieves high elastic modulus and Tg while avoiding the formation of voids and excessive crosslink density that would compromise heat resistance after moisture absorption.
Solution Approach 2:
The copolymer with carboxyl or amide groups acts as an intermediary that provides strong intermolecular forces (hydrogen bonds) to increase rigidity and Tg, while the hydrogen bonding nature allows for some flexibility and stress relief, preventing void formation and maintaining reliability after moisture absorption.
4Stability of the object's composition
If conventional methods are used to reduce thermal expansion, then thermal expansion reduces, but it is difficult to further reduce thermal expansion as limits are reached
Solution Approach 1:
The patent changes the fundamental approach to thermal expansion control by using a copolymer with hydrogen-bonding functional groups. This chemical parameter change creates a molecular network that can be tuned to achieve very low thermal expansion coefficients, surpassing the limits of conventional methods and providing room for further optimization.
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 resin composition effectively reduces thermal expansion, enhances copper foil peel strength, and maintains excellent moldability and heat resistance, addressing the limitations of existing technologies.
Implementation Method 1
at least a part of the alkyl ester groups of the alkyl (meth)acrylate units and/or the cyano group of the acrylonitrile unit are modified with at least one selected from the group consisting of an epoxy group, a carboxyl group, and an amide group
Data Source
AI summary
A resin composition comprising a thermosetting resin, a functional group-modified copolymer, and an inorganic filler, wherein the functional group-modified copolymer has two or more alkyl (meth)acrylate units, or one or two or more alkyl (meth)acrylate units and an acrylonitrile unit, and at least a part of alkyl ester groups of the alkyl (meth)acrylate units and/or a cyano group of the acrylonitrile unit are/is modified with at least one selected from the group consisting of an epoxy group, a carboxyl group, and an amide group.