Submicron Gold Powder Composition for Low-Temperature Bonding
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Solution Overview
Problem
The challenge is to reduce chloride ion content in submicron gold powders used in electronics to prevent corrosion and agglomeration issues during low-temperature packaging, while maintaining effective bonding and sealing properties.
Innovation Solution
A gold powder with a chloride ion content of 100 ppm or less and a cyanide ion content between 10 ppm and 1000 ppm is developed, using a wet reduction method and treatment with a cyanide solution to inhibit agglomeration and ensure low-temperature packaging compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chloride ion content is reduced in gold powder, then corrosion resistance is improved, but agglomeration tendency increases
Solution Approach 1:
The patent introduces cyanide ions as an intermediary substance that mediates between the conflicting requirements of low chloride content and agglomeration resistance. The cyanide ions adsorb on the gold powder surface, providing steric hindrance and electrostatic repulsion to prevent agglomeration, while allowing chloride ions to be removed through washing processes.
Solution Approach 2:
The patent changes the chemical composition parameters by controlling the cyanide ion content in the range of 10-1000 ppm and chloride ion content at 100 ppm or less. This parameter optimization resolves the contradiction by finding the right balance between corrosion resistance (low chloride) and agglomeration resistance (controlled cyanide content).
2Temperature
If gold powder is used for low-temperature packaging, then heat loss is reduced, but chloride ion removal becomes more critical
Solution Approach 1:
The patent applies preliminary action by removing chloride ions through washing with water or alcohol before the low-temperature packaging process. This pre-treatment ensures that when the gold powder is sintered at low temperatures (where chloride wouldn't evaporate effectively), the corrosion risk is already minimized.
Solution Approach 2:
The patent converts the potential harm of chloride ions (corrosion risk) into a manageable parameter by establishing specific content limits (100 ppm or less). This transforms the harmful impurity into a controlled parameter that can be managed through the cyanide ion addition mechanism.
3Stability of the object's composition
If cyanide ion content is increased to prevent agglomeration, then dispersibility is improved, but toxicness increases
Solution Approach 1:
The patent optimizes the cyanide ion content parameter within a specific range (10-1000 ppm) to achieve the minimum effective concentration for agglomeration prevention while minimizing toxicity. This parameter control allows the system to operate at the threshold where beneficial effects are maximized and harmful effects are minimized.
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 optimized gold powder exhibits improved dispersibility and bonding performance, preventing corrosion and agglomeration, and is suitable for low-temperature packaging applications in electronics.
Implementation Method 1
a content of a chloride ion is 100 ppm or less, and a content of a cyanide ion is 10 ppm or more and 1000 ppm or less
Implementation Method 2
treatment with a cyanide solution to inhibit agglomeration
Implementation Method 3
using a wet reduction method
Implementation Method 4
wet reduction method and treatment with a cyanide solution
Data Source
AI summary
A gold powder comprising gold having a purity of 99.9% by mass or more and having an average particle size of 0.01 μm or more and 1.0 μm or less, a content of a chloride ion is 100 ppm or less, and a content of a cyanide ion is 10 ppm or more and 1000 ppm or less. A total of the content of a chloride ion and the content of a cyanide ion is preferably 110 ppm or more and 1000 ppm or less. The gold powder has improved adaptability to various processes including bonding or the like with a content of a chloride ion, that is, an impurity, optimized. A gold paste using this gold powder is suitably used in various uses for bonding such as die bonding of a semiconductor chip, sealing a semiconductor package, and forming an electrode/wire.