Halogen-Free Resin Composition for Printed Wiring Boards
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Solution Overview
Problem
Existing resin compositions for printed wiring boards face challenges with high viscosity, moldability issues, inadequate solder heat resistance, and environmental concerns due to halogen content, while requiring high glass-transition temperatures and excellent dielectric properties.
Innovation Solution
A halogen-free resin composition comprising a polyarylene ether copolymer with specific intrinsic viscosity and phenolic hydroxyl groups, a triphenylmethane-type epoxy resin with a softening point of 50 to 70°C, and a cure accelerator, along with optional difunctional epoxy resin and phosphorus-containing compounds, to achieve low viscosity, high heat resistance, and excellent dielectric properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high molecular weight PPE is used to achieve excellent dielectric properties, then dielectric constant and dissipation factor are improved, but viscosity increases and fluidity decreases causing moldability problems
Solution Approach 1:
The invention changes the molecular weight parameter of PPE by using low molecular weight PPE (intrinsic viscosity 0.03 to 0.12 dL/g) instead of high molecular weight PPE. This parameter change resolves the contradiction by providing low viscosity and good fluidity for moldability while maintaining dielectric properties through the specific copolymer structure and curing system
Solution Approach 2:
The invention creates a composite resin composition by combining low molecular weight PPE with epoxy resin (60-85 mass parts PPE to 100 mass parts epoxy resin). This composite approach allows the system to achieve both low viscosity from the low molecular weight PPE and excellent dielectric properties through the synergistic combination with epoxy resin
2Ease of manufacture
If molecular weight of PPE is reduced by redistribution reaction to improve fluidity, then viscosity decreases and moldability improves, but cure becomes inadequate and heat resistance is reduced
Solution Approach 1:
The invention uses low molecular weight PPE with low intrinsic viscosity (0.03 to 0.12 dL/g) as a starting material that inherently provides good fluidity without requiring molecular weight reduction reactions. This eliminates the need for redistribution reactions that would compromise heat resistance, while the low molecular weight PPE still achieves excellent cured product properties through the epoxy resin curing system
Solution Approach 2:
The invention changes the approach from modifying PPE molecular weight through chemical reactions to selecting PPE with inherently low molecular weight (low intrinsic viscosity). This parameter selection approach maintains heat resistance by avoiding reaction-induced molecular weight changes while achieving the desired fluidity for moldability
3Reliability
If PPE proportion is raised to improve dielectric properties and heat resistance, then dielectric constant and Tg are improved, but viscosity increases causing moldability problems
Solution Approach 1:
The invention changes the key parameter from PPE molecular weight to PPE intrinsic viscosity, selecting low intrinsic viscosity PPE (0.03 to 0.12 dL/g). This allows raising the PPE proportion (60-85 mass parts) to achieve excellent dielectric properties and heat resistance while maintaining low viscosity and good moldability that would not be possible with conventional high molecular weight PPE
4Reliability
If halogen-containing flame retardant is used to achieve flame retardancy, then flame resistance is improved, but environmental friendliness deteriorates
Solution Approach 1:
The invention extracts and eliminates halogen-containing flame retardants from the resin composition. Instead, it uses a halogen-free system relying on the inherent flame resistance of the cured epoxy-PPE composite, achieving both flame retardancy and environmental friendliness by removing the harmful halogen component while maintaining the required fire safety properties
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 provides a resin composition with improved heat resistance, dielectric properties, and flame retardancy without halogens, ensuring reliable printed wiring boards with enhanced solder heat resistance and external appearance.
Implementation Method 1
a resin composition that comprises (A) a polyarylene ether copolymer that has an intrinsic viscosity, measured in methylene chloride at 25° C., of 0.03 to 0.12 dL/g and that has an average of 1.5 to 3 phenolic hydroxyl groups in molecular terminal position per molecule, (B) a triphenylmethane-type epoxy resin that has a softening point of 50 to 70° C., and (C) a cure accelerator
Data Source
AI summary
An object is to provide a resin composition that has excellent dielectric properties, that yields a highly heat-resistant cured product, that provides a low viscosity when made into a varnish, and that has a high Tg and a high flame retardancy without containing halogen. The resin composition contains a polyarylene ether copolymer (A) that has an intrinsic viscosity, measured in methylene chloride at 25° C., of 0.03 to 0.12 dL/g and that has an average of 1.5 to 3 phenolic hydroxyl groups in molecular terminal position per molecule, a triphenylmethane-type epoxy resin (B) that has a softening point of 50 to 70° C., and a cure accelerator (C), wherein the content of the polyarylene ether copolymer (A) is 60 to 85 mass parts where the total of the polyarylene ether copolymer (A) and the epoxy resin (B) is 100 mass parts.