Flexible Wiring Substrate with Variable Thickness for Fine Pitch and Strength

Solution Overview

Problem

Conventional flexible wiring substrates face challenges in achieving fine pitch wiring patterns with good shape and reduced thickness variation while maintaining mechanical strength, particularly when folded, due to limitations in etching and bonding between semiconductor elements and wiring patterns.

Innovation Solution

A flexible wiring substrate design with a wiring layer having a thinner thickness in mounting regions than non-mounting regions, allowing for precise etching and improved mechanical strength through the use of an insulating layer and a wiring layer with varying thicknesses in connecting and non-connecting sections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the wiring pattern thickness is reduced to achieve fine pitch (35 μm or less), then the wiring pitch precision is improved, but the mechanical strength deteriorates causing breaks or exfoliation during folding

Engineering Contradiction:

Improvewiring pitch precisionVSAvoidmechanical strength

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The patent applies local quality by making the wiring layer thickness non-uniform: thinner (3-8 μm) in mounting regions where fine pitch bonding is required, and thicker (8-18 μm) in non-mounting regions where mechanical strength is needed. This spatial variation in thickness resolves the contradiction between fine pitch precision and mechanical strength.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The wiring layer is segmented into different thickness zones: mounting regions with reduced thickness for precise fine pitch wiring, and non-mounting regions with greater thickness for structural support. This segmentation allows each region to optimize for its specific function.

Inventive Principle:

Principle #1Segmentation

2Strength

If the wiring pattern thickness is increased to improve mechanical strength, then the strength is improved, but the wiring pitch precision deteriorates as fine pitch design becomes difficult

Engineering Contradiction:

Improvemechanical strengthVSAvoidwiring pitch

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent applies local quality by making the wiring layer thickness non-uniform: thinner (3-8 μm) in mounting regions where fine pitch bonding is required, and thicker (8-18 μm) in non-mounting regions where mechanical strength is needed. This spatial variation in thickness resolves the contradiction between fine pitch precision and mechanical strength.

Inventive Principle:

Principle #3Local quality

3Strength

If the wiring pattern thickness is increased to improve mechanical strength during folding, then the strength is improved, but the bonding precision deteriorates due to thickness variation

Engineering Contradiction:

Improvemechanical strengthVSAvoidbonding precision

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent applies local quality by making the wiring layer thickness non-uniform: thinner (3-8 μm) in mounting regions where fine pitch bonding is required, and thicker (8-18 μm) in non-mounting regions where mechanical strength is needed. This spatial variation in thickness resolves the contradiction between fine pitch precision and mechanical strength.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS7977805B2Flexible wiring substrate, semiconductor device and electronic device using flexible wiring substrate, and fabricating method of flexible wiring substrate

Publication Date: 2011.07.12 SHENZHEN TOREY MICROELECTRONIC TECH CO LTD

AI summary

A flexible wiring substrate is provided which realizes a fine pitch of a wiring pattern and improves mechanical strength of the wiring pattern so as to prevent breaks or exfoliation of the wiring pattern. A flexible wiring substrate 3 of the present invention includes an insulation tape 6, and a wiring pattern 7 formed on the insulation tape 6. A thickness of the wiring pattern 7 is made thinner in a mounting region, where a semiconductor element is connected to, than in a non-mounting region.