Naphthalene Epoxy Prepreg Warpage Reduction
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Solution Overview
Problem
Conventional printed wiring boards face issues with warpage and heat resistance due to varying substrate material properties, particularly when the thickness of the insulating layer exceeds 0.2 mm, leading to moisture absorption and resin breakdown during soldering.
Innovation Solution
A prepreg composed of a resin composition containing an epoxy resin with a naphthalene skeleton, a phenolic hardener with a naphthalene skeleton, and an inorganic filler, which are phase-separated to maintain high heat resistance and reduce warpage, along with a woven fabric base material, forming a metal-clad laminated plate and printed wiring board with improved moisture resistance and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the insulating layer is increased to improve electrical insulation, then insulation performance is improved, but warpage increases and heat resistance deteriorates due to moisture absorption and resin breakdown
Solution Approach 1:
The patent employs a composite resin composition containing multiple epoxy resins (cyclic ether type and naphthalene type), phenolic hardeners, and inorganic fillers. This composite structure allows the insulating layer to achieve both high thickness for electrical insulation and maintained structural stability with reduced warpage, as the synergistic combination of materials provides both insulation performance and dimensional stability during soldering processes.
Solution Approach 2:
The patent optimizes specific parameters of the resin composition including the molecular weight of epoxy resins (20,000-50,000 for cyclic ether type, 300,000-850,000 for naphthalene type), the ratio of resin components, and inorganic filler content. These parameter adjustments enable the insulating layer to maintain appropriate viscosity for thick layer formation while achieving high heat resistance and reduced warpage through controlled curing characteristics.
2Ease of manufacture
If conventional resin compositions are used to simplify manufacturing, then manufacturing process is simplified, but heat resistance with moisture absorption deteriorates during soldering
Solution Approach 1:
The patent uses a composite resin system combining cyclic ether type epoxy resin (low molecular weight 20,000-50,000) with naphthalene type epoxy resin (high molecular weight 300,000-850,000) and specific phenolic hardeners. This composite provides both ease of manufacture through good processability and high heat resistance with moisture absorption, as the low molecular weight resin ensures proper viscosity and wetting while the high molecular weight naphthalene resin provides thermal stability during soldering.
Solution Approach 2:
The patent specifies precise parameter ranges for the resin composition including epoxy resin molecular weights, hardener-to-resin ratios, and inorganic filler particle sizes and distributions. These parameter optimizations enable conventional manufacturing processes to produce insulating layers with enhanced heat resistance and moisture absorption characteristics, eliminating the need for specialized processing while achieving superior reliability.
3Strength
If the resin composition is optimized for high strength to prevent warpage, then warpage is reduced, but moisture absorption increases leading to resin breakdown
Solution Approach 1:
The patent employs a composite resin system where cyclic ether type epoxy resin provides strong adhesion and high strength to prevent warpage, while naphthalene type epoxy resin with high molecular weight provides hydrophobicity and resistance to moisture absorption. The synergistic combination allows the resin to maintain high strength for warpage control while simultaneously resisting moisture uptake and thermal degradation during soldering processes.
Solution Approach 2:
The patent optimizes the molecular weight parameters of the epoxy resins, with cyclic ether type at 20,000-50,000 for strong bonding and naphthalene type at 300,000-850,000 for moisture resistance. The hardener-to-resin ratio and curing conditions are also precisely controlled to achieve a crosslinked network structure that provides both high strength for dimensional stability and low moisture permeability for heat resistance during soldering.
Data Source
AI summary
A prepreg includes a resin composition including: (A) at least one of an epoxy resin having a naphthalene skeleton and a phenolic hardener having a naphthalene skeleton; (B) a polymer having at least the structures of formulae (2) and (3) among formulae (1), (2) and (3) and having a weight-average molecular weight of from 200,000 to 850,000 inclusive; and (C) an inorganic filler:wherein x:y:z (molar fraction)=0:0.95:0.05 to 0.2:0.6:0.2 (where x+y+z≦1, 0≦x≦0.2, 0.6≦y≦0.95, 0.05≦z≦0.2); R1 represents a hydrogen atom or a methyl group and R2 includes at least one of a glycidyl group and an epoxidized alkyl group among a hydrogen atom, an alkyl group, a glycidyl group and an epoxidized alkyl group in formula (2); and R3 represents a hydrogen atom or a methyl group and R4 represents Ph (phenyl group), —COOCH2Ph or —COO(CH2)2Ph in formula (3).