Double-Layer Metal Substrate for Flexible PCB Manufacturing
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Solution Overview
Problem
The production of ultra-thin flexible printed circuit boards is hindered by issues such as fold injury, pad injury, or delamination due to the inadequate stiffness of single-layer polyimide substrates, leading to increased defect rates and reduced yield, especially during thermal lamination processes.
Innovation Solution
A double-layer metal substrate structure is created by bonding two single-sided substrate structures with modified insulating substrates and metal layers, where the insulating substrates have undergone surface modification processes to enhance bonding strength and prevent residual adhesive issues, allowing for temporary lamination and efficient separation without defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a single layer PI substrate is used for ultra-thin flexible printed circuit board, then the substrate thickness is reduced, but fold injury, pad injury or delamination occur due to inadequate stiffness
Solution Approach 1:
The substrate is divided into multiple layers: a PI substrate layer and a reinforcing layer separated by a release paper. This segmentation allows the PI substrate to remain thin while the reinforcing layer provides the necessary stiffness, preventing fold injury and delamination during processing.
Solution Approach 2:
A release paper is introduced as an intermediary layer between the PI substrate and the reinforcing layer. This release paper enables temporary bonding during processing to maintain stiffness, then allows easy separation to prevent adhesive residue and maintain substrate flexibility.
2Strength
If an adhesive layer and reinforcing layer are added to reinforce the ultra-thin substrate, then the substrate stiffness is improved, but the thickness of the flexible printed circuit board is increased
Solution Approach 1:
The reinforcing structure is segmented into distinct layers: PI substrate, release paper, and reinforcing layer. This allows the reinforcing layer to provide stiffness without being permanently bonded to the substrate, enabling easy removal after processing to maintain thin profile.
Solution Approach 2:
The surface properties of the PI substrate are modified to create temporary adhesion to the release paper during processing, then the adhesion is reversed or eliminated to allow easy separation. This parameter change enables dynamic control of bonding strength.
3Strength
If thermal lamination with high temperature and high pressure is used to bond the reinforcing layer, then the bonding strength is improved, but the adhesive is fused and bonded to the PI substrate causing product defects
Solution Approach 1:
The release paper acts as a mediator that receives the adhesive bonding during thermal lamination, protecting the PI substrate from direct adhesive contact. The release paper's surface properties prevent permanent adhesive bonding, allowing clean separation without residue.
Solution Approach 2:
The release paper serves as a temporary copy or substitute for the final bonding interface. It provides the necessary bonding during processing, then is removed to leave the PI substrate clean and free of adhesive residue.
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 approach strengthens the substrate structure, prevents delamination, and significantly increases the yield and productivity of printed circuit board manufacturing by ensuring the insulating substrates can be easily bonded and separated without residual adhesive, thus enhancing the mechanical properties and process efficiency.
Implementation Method 1
The second insulating substrate is bonded on the first modified surface
Data Source
AI summary
A metal substrate includes a first insulating substrate, a second insulating substrate, a first metal layer and a second metal 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 second insulating substrate is bonded on the first modified surface, such that the first insulating substrate is between the second insulating substrate and the first metal layer. The second metal layer is disposed on a side of the second insulating substrate, such that the second insulating substrate is between the first modified surface 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 second insulating substrate.