Tin Plating Bath Cooling and Filtration for Circuit Boards
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Solution Overview
Problem
The existing methods for depositing tin coatings onto copper surfaces in circuit board manufacturing face challenges such as precipitation of Cu(I) thiourea complex blocking nozzles and difficulties in replenishing bath components like thiourea, leading to inefficient process material turnover and increased costs due to the need for continuous addition and removal of bath liquid.
Innovation Solution
A method involving a bath liquid with Sn(II) ions, complexing agents, and acids, where the bath liquid is cooled and filtered to separate the precipitate, using pressure filtration to recover valuable components and reduce contamination, allowing for simplified replenishment of bath components and improved process efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the bath liquid is continuously circulated and components are continuously added and removed, then the deposition process can be maintained, but the process complexity and costs increase significantly
Solution Approach 1:
The bath liquid is cooled in advance in a cooling tank before filtration, causing the precipitate to form ahead of time. This preliminary action allows the filtration system to handle pre-formed precipitate rather than forming it during filtration, simplifying the overall process and reducing operational complexity while maintaining continuous deposition capability
Solution Approach 2:
The bath circulation system is divided into separate functional segments: a cooling tank for temperature reduction and precipitate formation, and a filtration apparatus for solid-liquid separation. This segmentation allows each component to perform its specific function efficiently without interfering with others, reducing overall system complexity
2Loss of substance
If pressure filtration is used to separate precipitate from filtrate, then the recovery of bath components is improved, but the device complexity increases
Solution Approach 1:
The bath liquid undergoes a temperature phase transition by being cooled in the cooling tank, which causes the dissolved components to precipitate out as solids. This phase transition simplifies the subsequent filtration process by creating a distinct solid-liquid separation that is easier to handle with standard filtration equipment
Solution Approach 2:
The temperature parameter of the bath liquid is changed by cooling it down, which fundamentally alters the solubility characteristics of the bath components. This parameter change causes the precipitate to form, enabling efficient separation through filtration and improving bath component recovery without requiring complex filtration systems
3Duration of action of stationary object
If the precipitate is not separated efficiently, then the bath liquid can be continuously used, but nozzle blocking and contamination increase
Solution Approach 1:
The precipitate is extracted from the bath liquid through the filtration apparatus, removing the harmful blocking substance before it can accumulate and clog the nozzles. This extraction process allows the clarified filtrate to be returned to the bath, extending its usable life while preventing nozzle contamination
Solution Approach 2:
The bath liquid is rapidly cooled in the cooling tank, causing quick precipitate formation that can be immediately filtered out. This rapid processing prevents the precipitate from having time to settle and block nozzles, allowing continuous operation without interruption for maintenance
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 enhances the recovery of bath components, reduces contamination, and simplifies the addition of less soluble components, leading to cost savings and improved deposition efficiency by minimizing the fluctuation of bath concentrations and reducing the need for continuous analytical monitoring.
Implementation Method 1
cooling and stirring the bath liquid in the settling tank in order to generate a precipitate
Implementation Method 2
generate a precipitate and a filtrate, the precipitate comprising the second metal (in the form of its ions) and at least one complexing agent
Implementation Method 3
separating the precipitate from the filtrate using a filtration apparatus
Implementation Method 4
a pressure difference is generated via the filter
Implementation Method 5
returning the filtrate to the bath liquid
Data Source
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AI summary
For the purpose of simplifying the processing of a bath a method for depositing a coating of a first metal onto a workpiece 12 which exposes a second metal is proposed which method comprises the following method steps: a) providing a bath liquid 16 containing bath components containing ions of the first metal to be deposited, at least one complexing agent for the second metal and at least one acid, b) depositing the coating of the first metal from the bath liquid 16 onto the workpiece 12, c) feeding the bath liquid 16 into a settling tank 18, d) cooling the bath liquid 16 in the settling tank 18 for the generation of a precipitate and of a filtrate, the precipitate being comprised of the second metal and the at least one complexing agent, f) returning the filtrate to the bath liquid 16 and g) replenishing bath components to the bath liquid 16. The method in accordance with the invention is characterised in that with respect to the separation of the precipitate from the filtrate a pressure difference is generated by the filter.