Nanoporous Gold-Polymer Adhesion via Silver Leaching
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Solution Overview
Problem
The adhesion of polymer layers on precious metal surfaces, such as gold, is inadequate, leading to separation under mechanical or thermomechanical stress in semiconductor and microelectronic applications, as existing methods like surface roughening and adhesive use yield unsatisfactory results.
Innovation Solution
A nanoporous gold layer is created by depositing a gold-silver alloy and selectively removing silver, allowing the polymer to penetrate and form a three-dimensional interface with mechanical interlocking, enhancing adhesive strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the surface is roughened to improve adhesion, then the adhesive strength is improved, but the manufacturing complexity increases and results are unsatisfactory
Solution Approach 1:
The patent applies a porous anodized aluminum oxide layer as an intermediate layer between the polymer and precious metal. This porous structure allows the polymer to penetrate deeply into the layer, creating extensive mechanical interlocking. The porous material provides high surface area and three-dimensional anchoring points, significantly improving adhesive strength without requiring complex surface roughening processes.
Solution Approach 2:
The patent creates a composite structure consisting of the precious metal layer, the porous anodized aluminum oxide intermediate layer, and the polymer layer. This multi-layer composite material system combines the advantages of each layer: the precious metal provides electrical conductivity and barrier properties, the porous aluminum oxide provides mechanical interlocking and adhesion promotion, and the polymer provides the functional properties. The interface between these different materials creates strong bonding through mechanical interlocking.
2Strength
If adhesives like Titan are used to improve specific adhesion, then the adhesive strength is improved, but the manufacturing complexity and process difficulty increase
Solution Approach 1:
The porous anodized aluminum oxide layer serves multiple functions simultaneously: it acts as an adhesion promoter, a mechanical interlocking structure, and a surface preparation layer. The layer's porous structure automatically provides mechanical anchoring points for the polymer without requiring additional adhesive materials or complex surface treatment processes. The system is self-sufficient in providing adhesion enhancement.
3Strength
If the surface area is increased by roughening, then the adhesion is improved, but the manufacturing precision and result quality become unsatisfactory
Solution Approach 1:
The anodized aluminum oxide layer is formed through a controlled electrochemical process that creates a uniform porous structure with consistent pore size and distribution. This controlled porosity provides predictable and reproducible mechanical interlocking with the polymer, ensuring high manufacturing precision and consistent adhesion results across different production batches.
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 method significantly improves the adhesive strength of polymer layers on gold surfaces, ensuring durability and reliability in microelectronic, micromechanical, and microoptical applications by creating a strong mechanical bond between the polymer and gold layers.
Implementation Method 1
the applied liquid polymer penetrates into the sponge-like structures and forms a three-dimensional interface with mechanical interlocking between the materials
Implementation Method 2
deposition of a layer made of 20% to 40% gold and 60% to 80% silver onto a substrate
Data Source
AI summary
The invention relates to a method for connecting a precious metal surface to a polymer, wherein a layer made of 20% to 40% gold and 60% to 80% silver is deposited on a substrate and the silver is subsequently selectively removed in order to produce a nanoporous gold layer. A fluid polymer is applied to the gold layer and cured.