Metal Substrate with Release Layer for Flexible PCB Stiffness

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Solution Overview

Problem

The production of ultra-thin flexible printed circuit boards faces issues such as fold damage, pad damage, and delamination due to inadequate stiffness of single-layer polyimide substrates, leading to increased defect rates and reduced yield.

Innovation Solution

A metal substrate structure comprising two single-sided substrate structures bonded by a release layer, where one substrate's surface is modified to maintain low surface roughness and high surface energy, allowing for temporary bonding and easy separation without residual adhesive, enhancing structural strength and preventing delamination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a single layer PI substrate is used to manufacture an ultra-thin flexible printed circuit board, then the substrate thickness is reduced, but fold damage, pad damage or delamination occurs due to inadequate stiffness

Engineering Contradiction:

Improvesubstrate thicknessVSAvoidsubstrate stiffness

Core Design Contradiction:

Volume of moving objectVSStrength

Solution Approach 1:

The patent uses a composite structure consisting of a PI substrate, an adhesive layer, and a reinforcing layer (such as glass fiber or metal mesh) to achieve both ultra-thin thickness and adequate stiffness. The reinforcing layer provides structural support while the adhesive layer ensures strong bonding between the substrate and the reinforcing layer, preventing delamination and damage during processing.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The reinforcing layer is strategically positioned at specific locations where additional stiffness is needed, such as around pads or in areas prone to folding. This allows the substrate to remain ultra-thin overall while providing localized reinforcement where required to prevent damage.

Inventive Principle:

Principle #3Local quality

2Strength

If an adhesive layer and reinforcing layer are introduced to reinforce the ultra-thin copper clad substrate, then substrate stiffness is improved, but the adhesive may be fused and bonded to the PI substrate during thermal lamination, increasing product defect rate

Engineering Contradiction:

Improvesubstrate stiffnessVSAvoidproduct defect rate

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent optimizes the adhesive layer's composition and thickness parameters, and controls the thermal lamination parameters (temperature, pressure, time) to prevent the adhesive from fusing to the PI substrate. By carefully selecting the adhesive material with appropriate glass transition temperature and bonding characteristics, and controlling the lamination process within specific parameter ranges, the adhesive provides sufficient bonding strength without causing defects.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The adhesive layer serves as an intermediary between the PI substrate and the reinforcing layer, providing controlled bonding. The adhesive's properties are specifically selected to bond the reinforcing layer to the substrate while remaining distinct from the PI substrate during thermal lamination, preventing the adhesive from fusing to the substrate and causing defects.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Strength

If the reinforcing layer is retained to maintain structural integrity, then substrate stiffness is improved, but the thickness of the flexible printed circuit board is increased

Engineering Contradiction:

Improvesubstrate stiffnessVSAvoidboard thickness

Core Design Contradiction:

StrengthVSVolume of moving object

Solution Approach 1:

The patent employs extremely thin reinforcing layers, such as thin glass fiber films or fine metal meshes, that provide adequate structural support and stiffness while minimizing thickness increase. These thin reinforcing structures maintain the flexible nature of the circuit board while preventing fold damage and delamination during processing.

Inventive Principle:

Principle #30Flexible shells and thin films

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 solution effectively prevents fold damage and delamination, increases the yield and efficiency of printed circuit board production by reinforcing the substrate structure and allowing for easy separation of the metal substrates after processing.

Implementation Method 1

The release layer is bonded on the first modified surface, such that the first insulating substrate is between the release layer and the first metal layer

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS11483934B2Metal substrate and method of manufacturing the same

Publication Date: 2022.10.25 AZOTEK

AI summary

A metal substrate includes a first insulating substrate, a second insulating substrate, a first metal layer, a second metal layer and a release layer. The first insulating substrate has a first modified surface and a second surface opposite to the first modified surface. The first metal layer faces the second surface. The release layer is bonded on the first modified surface. The second insulating substrate is bonded on a side of the release layer, such that the release layer is between the first modified surface and the second insulating substrate. The second metal layer is disposed on a side of the second insulating substrate, such that the second insulating substrate is between the release layer and the second metal layer. An original surface roughness of the first modified surface has a variation substantially less than 10% after the first modified surface is released from the release layer.