Adhesive Layer Bonding for Flexible Circuit Stress Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Flexible circuits used in applications involving repeated flexing are prone to failure due to stress on conductors and bond wires, and existing manufacturing methods are costly and inflexible, leading to reduced durability and increased manufacturing costs.

Innovation Solution

A flexible circuit arrangement with bond pads and conductors on a substrate, where a layer of adhesive is applied directly over the conductors with openings aligned with bond pads, allowing electronic devices to be attached and wire bonded through these openings, with additional adhesive and flexible liner layers to position bond wires and connections near the neutral axis, reducing stress and manufacturing costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conductors are placed near the neutral axis to add durability, then conductor durability is improved, but additional dielectric layers are required which increases manufacturing complexity and cost

Engineering Contradiction:

Improveconductor durabilityVSAvoidadditional dielectric layers

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the bonding function from the conductor layer by introducing a separate adhesive layer. This adhesive layer is positioned between the substrate and the electronic device, allowing the conductors to remain near the neutral axis for durability while the adhesive handles the bonding requirements, eliminating the need for additional dielectric layers.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The adhesive layer serves as an intermediary element between the substrate and the electronic device. It provides the bonding function that would otherwise require complex dielectric structures, while allowing the conductors to be positioned optimally for durability near the neutral axis.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If traditional soldering methods are used to attach electronic devices, then strong bonding is achieved, but manufacturing costs increase and the process becomes less flexible

Engineering Contradiction:

Improvebonding strengthVSAvoidmanufacturing cost and flexibility

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent replaces the traditional soldering process with an adhesive bonding system. The adhesive layer provides sufficient bonding strength to attach electronic devices to the substrate, eliminating the need for expensive and inflexible soldering operations while maintaining adequate bond strength for the application.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If bond wires are positioned away from the neutral axis for ease of connection, then connection ease is improved, but stress during flexing increases leading to reduced durability

Engineering Contradiction:

Improveconnection easeVSAvoiddurability under flexing

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent separates the connection function from the structural layer by using the adhesive layer as a bonding medium. This allows bond wires to be connected to the electronic device through the adhesive layer, positioning them near the neutral axis for durability while maintaining ease of connection through the adhesive's bonding properties.

Inventive Principle:

Principle #2Taking out (Extraction)

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

The solution enhances durability and flexibility while reducing manufacturing costs by locating bond pads and wires near the neutral axis, minimizing stress and improving the service life of flexible circuits, and can also be applied to rigid substrates to address challenges in solder application and component protection.

Implementation Method 1

A first layer of adhesive is directly disposed on the first surface of the substrate and the pattern of conductors

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS9814142B1Electronic devices wire bonded to substrate through an adhesive layer and method of making the same

Publication Date: 2017.11.07 AUTOMATED ASSEMBLY

AI summary

A disclosed circuit arrangement includes a substrate having first bond pads coupled to a pattern of conductors. The first bond pads and the pattern of conductors are disposed on a first surface of the substrate. A first layer of adhesive is directly disposed on the first surface of the substrate and the pattern of conductors and has openings at the first bond pads. An electronic device has opposing first and second surfaces and is attached to the first surface of the substrate by the first surface of the electronic device in contact with the first layer of adhesive. The second surface of the electronic device has second bond pads. Bond wires are connected at the first bond pads through the openings in the first layer of adhesive and connected at the second bond pads.