Halogen-Free Circuitized Substrate with Composite Dielectric Layer

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Solution Overview

Problem

Current methods for manufacturing circuitized substrates, such as PCBs, face challenges in achieving high circuit density due to the presence of continuous or semi-continuous glass fibers, which lead to issues like fiber intrusion during hole formation, electrical shorting, and dimensional instability, making it difficult to produce small, high-aspect-ratio thru-holes and dense circuitry.

Innovation Solution

A composite dielectric layer is introduced, comprising a first sub-layer with low coefficient of thermal expansion fibers and a second sub-layer of low moisture absorptivity resin with inorganic particulates, eliminating continuous or semi-continuous fibers to enable high-density thru-hole formation and improved reliability without electrical shorting.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If continuous or semi-continuous glass fibers are used in dielectric layers, then structural strength and rigidity are improved, but fiber intrusion during hole formation causes electrical shorting and manufacturing defects

Engineering Contradiction:

Improvestructural strengthVSAvoidelectrical reliability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent divides the dielectric layer into two distinct sub-layers: a first sub-layer containing continuous or semi-continuous glass fibers for structural strength, and a second sub-layer free of fibers for reliable hole formation. This segmentation allows each layer to fulfill its specific function without compromise.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent extracts the fibrous reinforcement function from the hole-forming region by placing it exclusively in the first sub-layer, while the second sub-layer is deliberately kept free of fibers to prevent intrusion during thru-hole and microvia formation, ensuring electrical reliability.

Inventive Principle:

Principle #2Taking out (Extraction)

2Stability of the object's composition

If continuous or semi-continuous glass fibers are present in dielectric layers, then dimensional stability is improved, but production of small, high-aspect-ratio thru-holes becomes difficult

Engineering Contradiction:

Improvedimensional stabilityVSAvoidthru-hole formation precision

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The dielectric layer is segmented into a first sub-layer with fibers for dimensional stability and a second fiber-free sub-layer for precise hole formation. This allows small, high-aspect-ratio thru-holes and microvias to be produced without fiber interference while maintaining overall dimensional stability.

Inventive Principle:

Principle #1Segmentation

3Object-affected harmful factors

If halogen-containing resins are used, then flame retardancy is improved, but environmental compliance and reliability are worsened due to toxic emissions

Engineering Contradiction:

Improveflame retardancyVSAvoidtoxic emissions

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent changes the chemical composition parameters of the resin from halogen-containing to halogen-free formulations, achieving flame retardancy through alternative mechanisms (such as phosphorus-based or nitrogen-based flame retardants) that do not produce toxic emissions, thereby improving environmental compliance and reliability.

Inventive Principle:

Principle #35Parameter changes

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

This solution allows for the creation of high-density arrays of thru-holes and improved dielectric reliability, enabling the production of substrates with small, high-aspect-ratio features and enhanced processing stability, while maintaining cost-effectiveness through standard manufacturing processes.

Implementation Method 1

a first dielectric sub-layer including a plurality of fibers having a low coefficient of thermal expansion

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

a second dielectric sub-layer of a low moisture absorptivity resin

Methodology Applied

Scientific EffectMoisture absorption: Absorption (physical)

Data Source

PatentUS7687722B2Halogen-free circuitized substrate with reduced thermal expansion, method of making same, multilayered substrate structure utilizing same, and information handling system utilizing same

Publication Date: 2010.03.30 TTM TECHNOLOGIES NORTH AMERICA LLC

AI summary

A circuitized substrate including a composite layer comprising a first dielectric sub-layer comprised of a halogen-free resin and fibers dispersed therein and a second dielectric sub-layer without fibers but also including a halogen-free resin with inorganic particulates therein. A method of making such a substrate is also provided, as is a multilayered assembly including one or more such circuitized substrates, possibly in combination with other substrates. An information handling system designed for having one or more such circuitized substrates is also provided.