Electroless Gold Plating Solution for Microfine Patterns
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Solution Overview
Problem
Conventional methods for forming microfine gold patterns with sizes of 100 μm or less and heights of 3 μm or more are hindered by issues such as non-uniformity, whisker generation, and self-decomposition of electroless gold plating solutions, particularly in fine sections and high-temperature conditions, limiting their practical application in electronic device manufacturing.
Innovation Solution
An electroless gold plating solution comprising an accelerator for deposition in fine areas, such as polymer compounds, nitrogen-containing compounds, and sulfur-containing water-soluble hydrocarbons, which enhances the deposition rate and stability, allowing for uniform filling of microfine patterns with a width of 100 μm or less and a height of 3 μm or more within 120 minutes, without using cyanide compounds and at a pH of 6-8.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional electroless gold plating solutions are used to form microfine patterns with width of 100 μm or less and height of 3 μm or more, then the deposition rate can be increased, but self-decomposition of the plating solution occurs and uniformity is lost
Solution Approach 1:
The patent applies local quality by using a polymer compound that selectively adsorbs to patterned surfaces, creating different deposition characteristics for fine patterns versus planar surfaces. The polymer modifies the local chemical environment at the patterned area, enabling accelerated deposition only where needed while maintaining solution stability overall.
Solution Approach 2:
The patent changes the chemical parameters of the plating solution by introducing a polymer compound and controlling pH within 2-7. This parameter change transforms the deposition behavior to achieve both high deposition rate on fine patterns and prevention of self-decomposition, resolving the contradiction between productivity and reliability.
2Loss of time
If the gold deposition rate is increased on fine sections, then the processing time can be reduced, but the resist material suffers damage from high temperature and high-alkaline conditions
Solution Approach 1:
The patent changes the pH parameter to a lower range (2-7) compared to conventional high-alkaline solutions, which reduces resist damage while maintaining fast deposition through the polymer compound's selective action. This parameter change allows processing time reduction without sacrificing resist integrity.
Solution Approach 2:
The polymer compound acts as an intermediary that enables fast deposition without requiring harsh conditions. It mediates between the gold source and the patterned surface, facilitating rapid deposition at milder temperatures and pH levels that do not damage the resist.
3Productivity
If cyanogen-containing electroless gold plating solutions are used to achieve high deposition rates, then the film-forming rate can reach 5 μm or more per hour, but the solution becomes aggressive to various materials and damages resists
Solution Approach 1:
The patent replaces the aggressive cyanogen-containing solution with a polymer-based system that achieves similar deposition rates without the harmful properties. The polymer compound provides the necessary acceleration function without the long-term stability and material compatibility issues of cyanogen solutions.
Solution Approach 2:
The patent converts the harmful aggression of conventional plating solutions into a beneficial selective deposition mechanism. The polymer compound's interaction with the patterned surface, which could be seen as a form of controlled aggression, is harnessed to achieve selective fast deposition without the unwanted side effects of material damage.
4Ease of manufacture
If electrolytic plating method is used to produce gold bumps, then bumps can be produced by electroless plating, but it cannot form a film on a closed pattern and structures with different heights are generated
Solution Approach 1:
The patent applies self-service by using a polymer compound that automatically recognizes and binds to patterned surfaces through adsorption. This self-recognition mechanism enables the solution to selectively deposit on closed patterns without requiring external circuit control, and the uniform adsorption characteristics ensure uniform deposition height across all patterns.
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 enables the formation of microfine patterns with uniform height and accelerated deposition in fine areas, overcoming the limitations of existing methods by ensuring high deposition rates and stability, even at reduced temperatures, thus improving the efficiency and reliability of microfine pattern fabrication.
Implementation Method 1
an electroless gold plating solution for forming a microfine pattern with a size of micrometer order, in particular that of 100 μm or less using gold alone
Implementation Method 2
an electroless gold plating solution comprising an accelerator for deposition in fine areas
Implementation Method 3
an accelerator for deposition in fine areas that has an action to suppress the reaction on a metal surface
Data Source
AI summary
An electroless gold plating solution with which one or more openings formed in a resist overlying a substrate can be filled in a short time, the openings having a width on the order of micrometer, in particular, 100 μm or smaller, in terms of the width of the exposed substrate area, and having a height of 3 μm or larger. The electroless gold plating solution contains a deposition accelerator for deposition in fine areas, and a microfine pattern of 100 μm or finer is formed therefrom.