Palladium Conductor Layer Formation on Polyimide
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Solution Overview
Problem
Conventional electroless copper plating processes face challenges with flexible and rigid flex substrates, particularly with polyimide materials, due to high alkalinity leading to adhesion failures and reduced deposition rates, and require costly reducing agents and complex solution stability maintenance.
Innovation Solution
A direct plating process using a palladium conductor layer forming solution with a palladium compound, amine compound, and azole compound at near-neutral pH, applied as an acidic palladium colloid catalyst to form a palladium conductor layer on insulating parts without forming it on copper parts, enabling reliable electrolytic copper plating without electroless copper plating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electroless copper plating with high alkaline solution is used, then copper plating can be applied to insulating parts, but polyimide substrate generates hydrophilic functional groups causing solution penetration and adhesion failure
Solution Approach 1:
The patent changes the pH parameter from high alkaline (conventional electroless plating) to near-neutral (direct plating with palladium catalyst). This parameter change prevents the generation of hydrophilic functional groups on polyimide, eliminating solution penetration while maintaining copper plating capability on insulating parts.
Solution Approach 2:
The patent introduces a palladium catalyst layer as an intermediary between the insulating polyimide substrate and the copper plating solution. This mediator enables electroplating to proceed on the insulating surface without requiring high alkaline conditions, thus preventing polyimide degradation while achieving reliable copper adhesion.
2Productivity
If electroless copper plating with high alkaline solution is used, then copper plating can be deposited, but adhesive layer dissolves causing reduced deposition rate and shortened solution life
Solution Approach 1:
The patent changes the pH from high alkaline to near-neutral, creating conditions that are gentle to adhesive layers. This prevents adhesive dissolution, maintains stable deposition rates, and extends solution life by eliminating the harmful interaction between alkaline solution and adhesive materials.
3Reliability
If conventional direct plating without electroless copper plating is used, then adhesion failure can be prevented, but copper etching step is required which is technically more difficult
Solution Approach 1:
The patent uses a palladium catalyst layer as an intermediary that enables direct electroplating on insulating surfaces without requiring subsequent copper etching steps. The palladium layer facilitates copper deposition while being compatible with copper surfaces, eliminating the need for separate etching operations and simplifying the manufacturing process.
4Reliability
If conventional direct plating is used, then adhesion failure can be prevented, but conductive layers may be dissolved or fall off by copper etching and acid cleaning
Solution Approach 1:
The patent changes the plating conditions to near-neutral pH, which is chemically compatible with both the conductive layer materials and the copper substrate. This parameter change prevents dissolution or degradation of conductive layers during the plating process, maintaining their stability and adhesion without requiring protective etching steps.
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 process prevents solution penetration into polyimide substrates, ensures excellent adhesion and corrosion resistance of the palladium conductor layer, eliminates the need for copper etching, and maintains high reliability of copper-copper connections, allowing for efficient and stable conductivity impartation.
Implementation Method 1
a palladium conductor layer is formed in a palladium conductor layer forming solution containing a palladium compound, an amine compound, an azole compound and a reducing agent
Implementation Method 2
forming a palladium conductor layer on the insulating part
Implementation Method 3
subjecting a surface of a workpiece, which includes an insulating part, to palladium catalyst treatment to apply a palladium catalyst onto the surface at the insulating part
Implementation Method 4
electrolytic copper plating is conducted to form an electrolytic copper plating film on the palladium conductor layer
Data Source
AI summary
A surface of an object to be plated is subjected to a treatment for palladium catalyst impartation to impart a palladium catalyst to the surface of an insulating part thereof. A palladium conductor layer is formed on the insulating part from a solution for palladium conductor layer formation which contains a palladium compound, an amine compound, and a reducing agent. On the palladium conductor layer is then directly formed a copper deposit by electroplating. Thus, the work is converted to a conductor with the solution for palladium conductor layer formation, which is neutral, without using an electroless copper plating solution which is highly alkaline. Consequently, the polyimide is prevented from being attacked and no adverse influence is exerted on adhesion. By adding an azole compound to the solution for palladium conductor layer formation, a palladium conductor layer is prevented from depositing on copper. Thus, the reliability of connection between the copper part present on a substrate and the copper deposit formed by electroplating is significantly high.