Aqueous Indium Plating Bath for Smooth Submicron Layer Deposition
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Solution Overview
Problem
Current indium plating technologies face challenges in producing smooth, submicron indium or indium alloy layers due to island-like structures, high toxicity of additives, and inefficiencies such as hydrogen evolution, which are not suitable for modern electronic industry demands.
Innovation Solution
An aqueous indium or indium alloy plating bath comprising a source of indium ions, an acid, a source of halide ions, and a surfactant, along with a dihydroxybenzene derivative, which stabilizes the bath and allows for controlled current flow and deposition, enabling the production of smooth layers on metal or metal alloy substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional electrolytic deposition methods are used, then indium layers can be deposited, but island-like structures form and smoothness is poor
Solution Approach 1:
The patent changes the chemical parameters of the plating bath by introducing specific organic additives (carboxylic acids, alcohols, sugars) and controlling pH within a narrow range (2-4). These parameter changes modify the deposition mechanism to prevent island formation and achieve smooth, uniform submicron layers.
Solution Approach 2:
The patent uses organic additives as intermediary substances that mediate between the indium ions and the substrate. These additives adsorb on the substrate surface and modify the deposition behavior, preventing direct island-like precipitation and enabling smooth layer formation.
2Reliability
If strong chelating agents or strongly alkaline/acidic plating baths are used, then indium precipitation is prevented, but toxicity increases and compatibility with later manufacturing stages decreases
Solution Approach 1:
The patent changes the pH parameter to a mild range (2-4) and uses weak chelating agents instead of strong ones. This parameter change maintains precipitation control while eliminating the need for toxic cyanide or strongly alkaline media, making the process compatible with subsequent manufacturing steps.
Solution Approach 2:
The patent employs readily available, non-toxic organic compounds (common carboxylic acids, alcohols, sugars) as bath additives. These inexpensive, benign substances replace toxic chelating agents and can be easily managed in the plating process.
3Manufacturing precision
If multi-step processes with intermediate layers are used, then island-like structures are prevented, but process complexity and production time increase
Solution Approach 1:
The patent combines multiple functions into a single plating bath formulation. The bath simultaneously provides pH control, chelation, surface modification, and deposition control through a combination of organic additives, eliminating the need for separate intermediate layer formation steps.
Solution Approach 2:
The plating bath is designed with multi-functional additives that perform multiple roles: pH buffering, indium complexation, surface activation, and deposition control. This universal formulation achieves smooth uniform layers in a single step without requiring specialized intermediate treatments.
4Productivity
If conventional plating baths are used, then deposition can occur, but hydrogen evolution reduces efficiency
Solution Approach 1:
The patent changes the electrochemical parameters of the plating bath through organic additives that modify the hydrogen evolution overpotential. These parameter changes suppress competing hydrogen evolution reactions and enhance indium deposition efficiency.
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 deposition of smooth, controlled thickness indium or indium alloy layers, reducing island-like structures and hydrogen evolution, and is applicable for various electronic applications including flip chips and solder bumps.
Implementation Method 1
a dihydroxybenzene derivative according to formula (II)... which stabilizes the bath and allows for controlled current flow and deposition
Implementation Method 2
The electrolytic deposition of indium has been established long ago in the art
Data Source
AI summary
An aqueous indium or indium alloy plating bath comprisinga source of indium ions,an acid,a source of halide ions,a surfactant according to formula (I)wherein A is selected from branched or unbranched C10-C15-alkyl;B is selected from the group consisting of hydrogen and alkyl;m is an integer ranging from 5 to 25;each R is independently from each other selected from hydrogen and methyl; anda dihydroxybenzene derivative according to formula (II)wherein each X is independently selected from fluorine, chlorine, bromine, iodine, alkoxy, and nitro;n is an integer ranging from 1 to 4,and a process for deposition of indium or an indium alloy wherein the disclosed bath is used.