Suspension Board Insulating Layer Thickness Control

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Solution Overview

Problem

Existing suspension boards with circuits face issues with posture angle accuracy and reliability due to potential disconnections or short-circuits caused by inconstant thicknesses in the base insulating layer, which affect the wiring traces during photolithographic processing.

Innovation Solution

A suspension board design featuring a conductive support substrate with an insulating layer having distinct thickness portions, where the wiring trace is formed at an angle relative to the boundary surface between these portions, ensuring that the reflected light does not interfere with the original pattern, thus preventing disconnections or short-circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If the base insulating layer is formed with inconstant thickness to reduce rigidity contribution ratio of wiring, then flexibility is improved, but reliability of wiring trace deteriorates due to disconnection or short-circuit

Engineering Contradiction:

Improverigidity contribution ratioVSAvoidwiring trace reliability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The insulating layer is designed with different thicknesses in different regions: a first thickness in the first region and a second thickness (smaller than the first) in the second region. This local variation in thickness allows the wiring to have reduced rigidity contribution ratio where needed while maintaining structural integrity elsewhere, preventing disconnection or short-circuit of the wiring trace.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If the wiring trace is formed on the insulating layer with inconstant thickness, then flexibility is improved, but manufacturing precision deteriorates due to photolithographic defects

Engineering Contradiction:

Improverigidity contribution ratioVSAvoidwiring trace pattern accuracy

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The boundary surface between the first and second regions, which could cause light reflection and photolithographic defects, is oriented at a specific angle (60-90 degrees) relative to the exposure light direction. This orientation converts the potential harmful reflection into a beneficial arrangement where the reflected light does not affect the wiring trace pattern formation, maintaining manufacturing precision.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Object-affected harmful factors

If the boundary surface is formed between upper surfaces of different thickness portions, then flexibility is improved, but device complexity increases due to photolithographic considerations

Engineering Contradiction:

Improverigidity contribution ratioVSAvoidinsulating layer formation process

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The angle between the boundary surface and the exposure light direction is set to a specific range (60-90 degrees). This parameter change optimizes the photolithographic process by ensuring that light reflected from the boundary surface does not affect the wiring trace pattern, simplifying the manufacturing process while maintaining the flexibility benefits of the inconstant thickness design.

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 configuration allows for precise adjustment of the posture angle with high accuracy while ensuring the reliability of the wiring trace, reducing the complexity of forming the insulating layer portions and minimizing stress concentration.

Implementation Method 1

reflection of the exposure light occurs at the boundary surface, and another region is indirectly irradiated with the reflected light

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS9251818B2Suspension board with circuits for accurate posture angle adjustment, and method for manufacturing the same

Publication Date: 2016.02.02 NITTO DENKO CORP

AI summary

A thick portion having a first thickness and a thin portion having a second thickness on a base insulating layer are formed on a conductive support substrate. The second thickness is smaller than the first thickness. A boundary surface is formed between an upper surface of the thick portion and an upper surface of the thin portion. A boundary line between the upper surface of the thick portion and the boundary surface extends in a first direction. Write wiring traces and read wiring traces are formed to extend on the thick portion and the thin portion of the base insulating layer. The lateral sides of the write wiring traces and the read wiring traces extend in a second direction that intersects with the first direction, and the second direction forms an angle of not less than 60 degrees and not more than 90 degrees with the first direction.