Epoxy Resin Insulating Layer for Uniform PCB Rewiring Surfaces
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Solution Overview
Problem
Conventional insulating layers used in wiring boards with embedded-type wiring layers have poor uniformity on their ground surfaces, making it difficult to form fine rewiring layers, resulting in low yield.
Innovation Solution
A cured product is developed using a resin composition comprising an epoxy resin, a curing agent, and an inorganic filler, with a ground surface having a maximum depressed portion depth of less than 10 μm, enhancing uniform applicability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional insulating layer is used, then the wiring board can be manufactured, but the ground surface uniformity is poor making it difficult to form fine rewiring layers
Solution Approach 1:
The patent modifies the resin composition parameters by incorporating specific inorganic fillers (silica, alumina, titania) with controlled particle sizes (0.1-10 μm) and surface treatments, along with specific resin components (polyester resin, epoxy resin) in defined ratios. These parameter changes result in a cured insulating layer with superior ground surface uniformity (surface roughness Ra ≤ 1.0 μm) that enables fine rewiring layer formation while maintaining high production yield.
2Stability of the object's composition
If a material with large amount of inorganic filler is used to lower the average coefficient of linear thermal expansion, then the thermal expansion matching improves, but the ground surface uniformity deteriorates
Solution Approach 1:
The patent applies local quality by using inorganic fillers with specific surface treatments (silane coupling agents, titanate coupling agents) that create different local properties on the filler surfaces. This localized surface modification improves the interface between filler and resin, preventing filler aggregation and maintaining uniform distribution even at high filler contents (60-80 wt%). The result is both good thermal expansion matching (CTE: 50-150 ppm/K) and acceptable ground surface uniformity.
Solution Approach 2:
The patent creates a composite material system combining multiple resin components (polyester resin with specific glass transition temperature range, epoxy resin) with treated inorganic fillers. This composite structure allows the material to achieve both thermal stability (through high filler content for CTE matching) and surface uniformity (through the synergistic effect of multiple resins and surface-treated fillers), resolving the contradiction between thermal expansion matching and ground surface quality.
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 improved uniformity of the ground surface allows for the formation of a fine rewiring layer with increased yield, while the resin composition's properties provide superior thermal expansion matching and mechanical strength.
Implementation Method 1
a cured material obtained by curing a resin composition
Implementation Method 2
mismatch of an average coefficient of linear thermal expansion (CTE: this is sometimes called thermal expansion rate) between a wiring layer and an insulating layer
Data Source
AI summary
Cured products that are formed of a cured material obtained by curing a resin composition including (A) at least one epoxy resin, (B) at least one curing agent, and (C) at least one inorganic filler, and have a ground surface, in which the maximum depth of a depressed portion present on the ground surface is less than 10 μm are useful for making printed wiring boards.