Epoxy Resin Composition for Multi-Layer PCB Insulating Layers
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Solution Overview
Problem
Current epoxy resin compositions for multi-layered printed boards face challenges in achieving high adhesiveness to plated conductors while maintaining low surface roughness, which is essential for forming reliable high-density wiring without damaging fine wires during flash etching.
Innovation Solution
An epoxy resin composition comprising an epoxy resin, a phenol type curing agent with specific hydroxyl group content, phenoxy resin, and rubber particles, which when cured, provides a surface with low roughness and high adhesiveness to plated conductors, enabling efficient flash etching and reliable wiring formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the roughness of the insulating layer surface is increased to improve adhesiveness to plated conductor, then the adhesiveness is improved, but the flash etching time increases and fine wiring may be damaged
Solution Approach 1:
The patent changes the chemical composition parameters of the epoxy resin system, specifically using a phenolic curing agent with controlled hydroxyl group content (0.3-1.5 hydroxyl groups per molecule) combined with phenoxy resin and rubber particles. This chemical parameter modification enables the resin to achieve high adhesiveness through molecular-level bonding rather than relying on physical surface roughness, thereby reducing the required flash etching time while maintaining strong conductor layer adhesion.
Solution Approach 2:
The patent creates a composite epoxy resin system combining multiple components: epoxy resin, phenolic curing agent with specific hydroxyl content, phenoxy resin, and rubber particles. This composite material approach synergistically combines the adhesive properties of the phenolic curing agent, the flexibility and surface properties of phenoxy resin, and the impact resistance of rubber particles, achieving high adhesiveness without requiring increased surface roughness.
2Strength
If the roughness of the insulating layer surface is increased to ensure anchor effect, then the adhesiveness is improved, but the density of wiring cannot be increased further
Solution Approach 1:
The patent replaces the mechanical anchor effect (physical interlocking through surface roughness) with chemical bonding mechanisms. The phenolic curing agent forms strong chemical bonds with the plated copper through its hydroxyl groups, while the phenoxy resin and rubber particles contribute to surface wetting and molecular adhesion. This substitution of mechanical bonding with chemical bonding enables smooth surfaces compatible with high-density fine wiring while maintaining strong adhesiveness.
3Reliability
If the flash etching time is extended to remove plated residue from concave, then the plated residue is removed completely, but the risk of damaging fine wiring increases
Solution Approach 1:
The patent applies preliminary action by modifying the insulating layer surface properties before the plating process. The specific epoxy resin composition with phenolic curing agent and phenoxy resin creates a surface that promotes uniform plating deposition and reduces plated residue formation in the first place. This preliminary surface preparation eliminates the need for extended flash etching to remove residue, thereby protecting fine wiring from damage while ensuring complete residue removal.
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 composition ensures high adhesive force between the insulating layer and the conductor layer, allowing for short flash etching times and the formation of high-density wiring with improved reproducibility and reduced risk of damage.
Implementation Method 1
an epoxy resin composition which comprises: (A) an epoxy resin having two or more epoxy groups in a molecule; (B) a phenol type curing agent where an average hydroxyl group content in a molecule (mean value of (the total number of hydroxyl groups)/(the total number of benzene rings)) P is 0
Implementation Method 2
adhesiveness of the insulating layer to a plated conductor layer (plated copper) is mostly ensured by means of the unevenness of the surface of an insulating layer (resin surface) formed by a roughening treatment (or, in other words, an anchor effect is achieved between the insulating layer and the plated layer because the surface of the insulating layer (resin surface) has unevenness)
Data Source
AI summary
Epoxy resin compositions, which comprise (A) en epoxy resin having two or more epoxy groups in a molecule; (B) a phenol type curing agent where an average hydroxyl group content in a molecule (a mean value of (the total number of hydroxyl groups)/(the total number of benzene rings)), P, satisfies the equation 0<P<1; (C) a phenoxy resin; and (D) rubber particles, are suitable for use as an insulating layer of a multi-layered printed board in which, in spite of the fact that the roughness of a roughened surface after a roughening treatment is relatively small, an insulating layer having a good tight adhesion with a conductor layer formed by plating is able to be easily introduced into a multi-layered printed board.