Electroless Palladium Plating Solution Stability
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Solution Overview
Problem
Electroless palladium plating solutions face challenges with bath stability and deposition rate reduction due to etching resist elution, particularly with hydrazine and formic acid-based systems, which result in plating defects and inefficiencies.
Innovation Solution
An electroless palladium plating solution using hydrazine or its salt as a reducing agent, combined with a specific compound represented by formula (1) or (2), maintains bath stability and deposition rate over time, even in the presence of etching resist elution, by controlling pH at 8 or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydrazine or its salt is used as a reducing agent, then the deposition rate is maintained, but bath stability deteriorates due to self-decomposition
Solution Approach 1:
The patent combines hydrazine or its salt with formic acid or its salt as reducing agents in the plating solution. This merging of two reducing agents allows the system to maintain the high deposition rate characteristic of hydrazine while the formic acid component suppresses self-decomposition, thereby improving bath stability without sacrificing productivity
Solution Approach 2:
The plating solution uses a composite reducing agent system comprising both hydrazine derivatives and formic acid derivatives. This composite approach leverages the complementary properties of each reducing agent: hydrazine provides high reduction efficiency and deposition rate, while formic acid contributes to bath stability by reducing self-decomposition, achieving both high productivity and reliability
2Reliability
If formic acid is used as a reducing agent, then bath stability is improved, but deposition rate decreases due to etching resist elution
Solution Approach 1:
The patent merges formic acid or its salt with hydrazine or its salt in the plating solution. The hydrazine component compensates for the low deposition rate issue by providing high reduction efficiency, while formic acid maintains bath stability. This combination resolves the contradiction between stability and productivity
Solution Approach 2:
The composite reducing agent system comprising formic acid derivatives and hydrazine derivatives allows the plating solution to exhibit both high bath stability (from formic acid) and high deposition rate (from hydrazine), overcoming the limitations of using either reducing agent alone
3Productivity
If activated carbon treatment is applied to suppress etching resist elution, then deposition rate is maintained, but manufacturing cost increases
Solution Approach 1:
The patent changes the chemical composition parameters of the plating solution by incorporating specific hydrazine derivatives and formic acid derivatives along with complexing agents and stabilizers. This chemical parameter modification allows the solution to resist etching resist elution without requiring physical treatment processes like activated carbon, thereby maintaining deposition rate while avoiding additional manufacturing costs
Solution Approach 2:
The plating solution is designed to self-regulate etching resist elution through its chemical composition. The combination of reducing agents, complexing agents, and stabilizers creates a self-protecting system that automatically prevents resist elution and maintains deposition rate without requiring external treatment processes, eliminating the need for costly activated carbon treatment
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 provides excellent bath stability and long-term deposition rate stability, suppressing the decrease in palladium film deposition rate caused by etching resist elution, while maintaining effective plating performance.
Implementation Method 1
Electroless palladium plating mainly uses formic acid or hydrazine including salts thereof, hypophosphite, or phosphite as a reducing agent
Implementation Method 2
a palladium compound; hydrazine or its salt; at least one selected from a group consisting of a compound represented by following formula (1) or its salt, and a compound represented by following formula (2) or its salt; and a pH of 8 or less
Data Source
AI summary
An electroless palladium plating liquid containing at least hydrazine or a salt thereof as a reducing agent, which has excellent bath stability in the vicinity of acidity to neutrality range, long-term stability, and is capable of suppressing the Pd film deposition rate decrease caused by elution of etching resist. An electroless palladium plating solution of the invention includes a palladium compound, hydrazine or its salt, at least one selected from a group consisting of a compound represented by the following formula (1) or its salt and a compound represented by the following formula (2) or its salt; and a pH of 8 or less, NH2NHCOR1 (1), (NH2NHCO)2(R2)n (2), wherein R1 represents H, NH2, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, NHNH2, or an aromatic group, wherein each of these groups may have a substituent; R2 represents (CH2) or an aromatic group, wherein each of these groups may have a substituent; and n represents an integer of 0 to 10.