Halogen-Free Resin Composition for PCB Substrates
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Solution Overview
Problem
Conventional halogen-free copper-clad laminates for printed circuit boards face challenges in achieving sufficient dimensional stability, dielectric properties, and heat resistance while meeting the requirements of ultra-thin HDI processes, as they often compromise on rigidity and adhesive force due to the use of amine curing agents.
Innovation Solution
A halogen-free thermosetting resin composition comprising a specific structure of halogen-free epoxy resin, phenolic curing agent, and phosphorus-containing flame retardant, which provides high glass transition temperature, dimensional stability, and adhesive force, along with excellent dielectric properties and heat resistance, achieving UL94 V-0 flame retardancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If amine curing agents (DICY, DDS) are used to achieve high adhesive force, then adhesive force is improved, but rigidity, dielectric properties and heat resistance deteriorate
Solution Approach 1:
The patent changes the chemical parameters of the curing agent from amine-based (DICY, DDS) to phenolic resin-based, which fundamentally alters the curing chemistry and resulting network properties. This parameter change enables simultaneous achievement of high adhesive force and superior heat resistance (Tg≥170℃), rigidity, and dielectric properties that were previously mutually exclusive
Solution Approach 2:
The patent creates a composite resin system by combining phenolic resin curing agent with epoxy resin and phosphorus-containing flame retardant in specific proportions. This composite material approach allows the formulation to achieve multiple performance targets simultaneously: high adhesive force, excellent heat resistance, good rigidity, and UL94 V-0 flame retardancy
2Length of stationary object
If fiberglass cloth is thinned to reduce substrate thickness, then substrate thickness is reduced, but rigidity and dimensional stability deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the resin system by introducing phenolic resin curing agent and phosphorus-containing flame retardant, which fundamentally alters the cured network structure. This enables ultra-thin substrates to maintain exceptional dimensional stability (radial expansion coefficient ≤50 ppm/℃, zonal expansion coefficient ≤50 ppm/℃) even with thinned fiberglass reinforcement
Solution Approach 2:
The patent enhances the local quality of the resin matrix by optimizing the chemical composition and crosslinking structure at the molecular level. The phenolic resin-based curing system creates a densely crosslinked network that provides localized structural support, compensating for the reduced mechanical support from thinned fiberglass cloth
3Productivity
If line width is reduced to increase circuit density, then circuit density is improved, but impedance control becomes difficult requiring lower dielectric constant
Solution Approach 1:
The patent changes the dielectric parameters of the substrate material by using phenolic resin curing agent, which achieves a balanced dielectric constant (Dk≥3.8) and low dissipation factor (Df≤0.012). This parameter optimization enables precise impedance control for high-density circuit patterns while maintaining signal integrity
4Object-affected harmful factors
If brominated flame retardants are used to achieve flame retardancy, then flame retardancy is improved, but harmful combustion products (hydrogen bromide, dioxin, dibenzofuran) are generated
Solution Approach 1:
The patent converts the traditionally harmful halogen-based flame retardancy approach into a beneficial halogen-free system. By using phosphorus-containing flame retardant, the system achieves UL94 V-0 flame retardancy while eliminating the generation of harmful combustion products such as hydrogen bromide, dioxin, and dibenzofuran, thus transforming a harmful chemical pathway into a safe one
Solution Approach 2:
The patent extracts and removes halogen elements (bromine, chlorine) from the flame retardant system, replacing them with phosphorus-based compounds. This extraction of harmful elements eliminates the root cause of toxic combustion products while maintaining effective flame retardancy through alternative chemical mechanisms
Data Source
AI summary
The present invention provides a halogen-free thermosetting resin composition, a prepreg, a laminate and a printed circuit board comprising the same. The halogen-free thermosetting resin composition comprises, based on 100 parts by weight of organic solids, (A) from 30 to 60 parts by weight of a halogen-free thermosetting resin, (B) from 10 to 35 parts by weight of a phenolic curing agent, and (C) a phosphorus-containing flame retardant. The prepregs, laminates and printed circuit boards prepared from the halogen-free thermosetting resin composition of the present invention have excellent dimensional stability and dielectric properties, high adhesive force, high heat resistance, low water absorption and better processability, and can achieve halogen-free flame retardancy and reach UL94 V-0.