Electroplating Rack Coating Prevents Metallization
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Solution Overview
Problem
Current chrome-free etching technologies for electroplating non-conductive substrates often result in 'rack plate up,' where the plastisol coating on electroplating racks becomes metallized, and components like PVC plastisols leach into treatment tanks, causing deleterious effects.
Innovation Solution
A modified plastisol coating for electroplating racks incorporating specific organosulfur compounds such as tetrabenzyl thiuram disulfide and zinc dimethyl-dithiocarbamate, which prevent nucleation of electroless nickel deposits and have low solubility in processing solutions, is applied and cured to form a solid insulating coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If chrome-free etching technologies (permanganate or manganese III) are used to etch ABS plastics, then the toxicity and carcinogenicity issues are resolved, but the plastisol coating on electroplating racks becomes coated with activator and subsequently metallized in the electroless plating stage
Solution Approach 1:
The patent applies a preliminary protective action by incorporating organosulfur compounds (such as thiuram disulfide or dithiocarbamate) into the plastisol coating before the etching process. This preliminary modification of the plastisol composition prevents subsequent metallization by blocking the nucleation sites on the rack surface, thereby resolving the contradiction between using toxic chromic acid and avoiding rack plate-up with chrome-free etchants.
2Productivity
If conventional plastisol coating is used on electroplating racks with chrome-free etching processes, then the etching effectiveness is maintained, but the rack coating becomes metallized causing rack plate up
Solution Approach 1:
The organosulfur compounds act as an intermediary substance within the plastisol coating that mediates between the etching process and the subsequent plating stages. These compounds are released in controlled amounts during the etching and activation processes to prevent metallization of the rack, while allowing the etching to proceed effectively. This resolves the contradiction by introducing a mediating agent that protects the rack without interfering with the etching effectiveness.
3Reliability
If plastisol coating is applied to prevent rack metallization, then the rack is protected from metal deposition, but components like PVC plastisols leach into treatment tanks causing deleterious effects
Solution Approach 1:
The patent changes the chemical composition parameters of the plastisol by incorporating organosulfur compounds that have low solubility in the processing solutions. This parameter change allows the coating to maintain its protective function while significantly reducing the leaching of harmful components into the treatment tanks, thereby resolving the contradiction between protection effectiveness and solution contamination.
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 modified plastisol coating effectively prevents metallization of the racks and reduces contamination of processing solutions, ensuring consistent and efficient electroplating of non-conductive substrates without 'rack plate up' issues across multiple cycles.
Implementation Method 1
incorporating specific organosulfur compounds such as tetrabenzyl thiuram disulfide and zinc dimethyl-dithiocarbamate, which prevent nucleation of electroless nickel deposits
Implementation Method 2
A modified plastisol coating for electroplating racks incorporating specific organosulfur compounds... is applied and cured to form a solid insulating coating
Implementation Method 3
The chromic acid is capable of dissolving the polybutadiene phase of the ABS by oxidation of the double bonds in the backbone of the polybutadiene polymer
Data Source
AI summary
a method of coating an electroplating rack used for supporting non-conductive substrates during a plating process. The method comprises the steps of contacting at least a portion of the electroplating rack with a plastisol composition, the plastisol composition having dispersed therein an effective amount of an additive having the structure: Formula (I) wherein R, R', R" and R'" are either the same or are independently selected from the group consisting of benzyl, substituted benzyl, phenyl or substituted phenyl; or :Formula (II) wherein R, R', R" and R'" are either the same or are independently selected from C I - CI O alkyl (either straight or branched chain), benzyl, substituted benzyl, phenyl, or substituted phenyl and M is a divalent metal cation, preferably selected from the group consisting of nickel, copper and zinc; and heating the electroplating rack with the plastisol composition thereon to a suitable temperature and for a sufficient time to cure the plastisol and form a solid insulating coating on the electroplating rack. The coated electroplating rack may then be used for mounting non- conductive substrates for subsequent metallization steps.