Flexible Wiring Circuit Substrate Terminal Section Design

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Solution Overview

Problem

The existing wiring circuit substrates for hard disk drives face issues with mechanical strength and production costs due to the need for additional copper plating processes, and flexible substrates experience wiring disconnection problems during connection to external circuits due to insufficient mechanical strength and deformation under heat application.

Innovation Solution

A wiring circuit substrate design featuring a metal support layer with a terminal section extending across the opening, connected via a conductor inside a via hole, and a conductive layer with a separating section, which increases mechanical strength and reduces contact resistance, eliminating the need for extra copper plating processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a flying lead with exposed copper conductive layer is used for connection, then the structure is simple and production cost is low, but the mechanical strength is weak and wiring disconnection occurs during ultrasonic bonding

Engineering Contradiction:

Improvemechanical strength of flying leadVSAvoidstructure complexity of terminal section

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent applies composite materials by combining the copper conductive layer with a metal support layer (stainless steel) to form a flying lead terminal section. This composite structure provides both the electrical conductivity of copper and the mechanical strength of stainless steel, resolving the contradiction between simplicity and mechanical strength.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies local quality by making the metal support layer thickness vary in different regions: thicker in the terminal section for mechanical strength and bonding reliability, and thinner in the wiring section for flexibility and cost reduction. This localized thickness variation optimizes both strength and complexity.

Inventive Principle:

Principle #3Local quality

2Strength

If additional copper plating processes are applied to reinforce the flying lead, then the mechanical strength increases, but the production cost increases

Engineering Contradiction:

Improvemechanical strength of conductive layerVSAvoidproduction process complexity

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent applies parameter changes by varying the thickness of the metal support layer across different regions of the substrate. The terminal section has greater thickness for strength, while the wiring section has reduced thickness for cost and flexibility, eliminating the need for additional copper plating processes.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the need for additional copper plating by using a composite structure where the metal support layer provides the necessary mechanical strength. This composite approach (copper conductive layer + metal support layer) achieves strength enhancement without adding complex plating processes.

Inventive Principle:

Principle #40Composite materials

3Strength

If the conductive layer thickness is increased in the exposed portion, then the mechanical strength improves, but the production cost increases due to extra copper plating

Engineering Contradiction:

Improvemechanical strength of exposed conductive layerVSAvoidamount of copper material

Core Design Contradiction:

StrengthVSQuantity of substance

Solution Approach 1:

The patent applies local quality by creating a non-uniform thickness distribution in the metal support layer: the terminal section has increased thickness for mechanical strength, while the wiring section maintains reduced thickness. This localized enhancement provides strength where needed without increasing overall material quantity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials where the metal support layer compensates for the thin copper conductive layer. The composite structure provides the necessary mechanical strength in the exposed terminal section without requiring increased copper thickness, thereby reducing total material quantity and cost.

Inventive Principle:

Principle #40Composite materials

4Strength

If a thin metal support layer is used to reduce weight and cost, then the weight and production cost decrease, but the mechanical strength becomes insufficient for reliable bonding

Engineering Contradiction:

Improvemechanical strength of metal support layerVSAvoidweight of substrate

Core Design Contradiction:

StrengthVSWeight of stationary object

Solution Approach 1:

The patent applies local quality by implementing spatially varying thickness in the metal support layer: thicker regions in the terminal section for bonding strength and thinner regions in the wiring section for weight reduction. This localized optimization resolves the contradiction between strength and weight.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS8995090B2Wiring circuit flexible substrate including a terminal section and a connecting section

Publication Date: 2015.03.31 DAI NIPPON PRINTING CO LTD

AI summary

A wiring circuit substrate, comprising: a metal support layer; an insulating layer formed on the metal support layer; a conductive layer for wiring formed on the insulating layer; and an opening formed so as to open at a same location in the insulating layer and the conductive layer for wiring, wherein the metal support layer includes: a support section that supports the insulating layer and the conductive layer for wiring, and a terminal section that extends from one edge side to the other edge side of the opening, the terminal section being separated from the support section; and the conductive layer for wiring includes a wiring that is connected to the terminal section by a connecting section.