Wiring Substrate Two-Layer Insulating Structure Thermal Stress

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Wiring substrates face issues with via conductors peeling off due to thermal expansion mismatch between insulating resin layers and conductor layers, leading to reliability concerns and difficulties in forming dense wiring patterns.

Innovation Solution

A wiring substrate with a two-layer insulating structure, where the coating insulating layer has a higher inorganic filler content and a smaller thermal expansion coefficient than the support insulating layer, allowing for a thermal expansion difference of 30 ppm/°C or less, and featuring a thicker coating insulating layer to reduce thermal stress and improve plating resist adhesion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single-layer insulating resin structure is used, then the manufacturing process is simple, but thermal expansion mismatch causes via conductors to peel off and reliability deteriorates

Engineering Contradiction:

Improveinsulating resin layer structureVSAvoidvia conductor connection reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The insulating resin layer is divided into two distinct layers: a coating insulating layer with high inorganic filler content (65-85% by mass) for thermal expansion matching, and a support insulating layer with lower inorganic filler content for mechanical support. This segmentation allows each layer to perform its specific function optimally, preventing via conductor peeling while maintaining manufacturing feasibility.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs composite insulating resin structures where inorganic fillers are combined with resin matrices in specific proportions. The coating insulating layer uses high inorganic filler content (65-85% by mass) to achieve low thermal expansion coefficient matching conductors, while the support insulating layer uses lower filler content for better processability and mechanical properties, creating a composite system that balances multiple requirements.

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If inorganic filler content is increased to reduce thermal expansion coefficient, then thermal expansion mismatch is reduced, but manufacturing precision and plating resist adhesion deteriorate

Engineering Contradiction:

Improvethermal expansion coefficient matchingVSAvoidplating resist adhesion and feature size control

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

Different regions of the insulating resin structure have different inorganic filler contents tailored to their specific functions. The coating insulating layer has high inorganic filler content (65-85% by mass) to minimize thermal expansion and prevent via conductor peeling, while the support insulating layer has lower inorganic filler content to maintain good plating resist adhesion and manufacturing precision. This local differentiation resolves the contradiction between thermal stability and manufacturability.

Inventive Principle:

Principle #3Local quality

3Reliability

If via conductors are formed to connect conductor layers, then electrical connectivity is achieved, but thermal stress from expansion mismatch causes peeling and reliability decreases

Engineering Contradiction:

Improvevia conductor connection reliabilityVSAvoidthermal expansion stress

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The coating insulating layer acts as an intermediary between the conductor layers and the support insulating layer. With its high inorganic filler content (65-85% by mass), it provides thermal expansion matching to reduce stress on via conductors, while still allowing the via conductors to connect conductor layers effectively. This intermediary layer protects via conductors from thermal stress without compromising electrical connectivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 configuration enhances the reliability of via conductors' connection to conductor layers, enables dense wiring patterns with reduced feature sizes, and minimizes warpage and electrical energy loss.

Implementation Method 1

a thermal expansion coefficient of the coating insulating layer is smaller than a thermal expansion coefficient of the support insulating layer and that the thermal expansion coefficients of the coating and support insulating layers have a difference of 30 ppm/° C. or less

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS9775237B2Wiring substrate and method for manufacturing the same

Publication Date: 2017.09.26 IBIDEN CO LTD

AI summary

A wiring substrate includes a core substrate, and a build-up layer including conductor layers and insulating layers alternately laminated on the substrate and via conductors formed in the insulating layers, each insulating layer having a coating layer and a support layer stacked on the coating layer such that the support layer has surface on which a conductor layer is laminated and the coating layer is covering a conductor layer, each via conductor connecting two conductor layers through an insulating layer. The coating layer has a thickness greater than that of the support layer and includes inorganic filler at content rate of 65 to 85% by mass, and the support layer includes inorganic filler at different content rate such that thermal expansion coefficient of the coating layer is smaller than that of the support layer and the coefficients of the coating and support layers have difference of 30 ppm/° C. or less.