Electroless Tin Plating Bath With Titanium Reducing Agent

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Solution Overview

Problem

Conventional tin plating baths, particularly electroless tin plating baths, suffer from a rapid decrease in plating rate over time, leading to inconsistent and inhomogeneous deposits, especially when plating on substrates of different sizes, and are prone to plate-out, making it difficult to control the thickness of tin or tin alloy deposits.

Innovation Solution

An electroless tin plating bath comprising tin ions, titanium ions as a reducing agent, sulfites, dithionites, thiosulfates, and complexing agents, with a pH range of 5 to 10.5, which maintains a constant plating rate for an extended period and prevents plate-out, ensuring homogeneous deposits on substrates of varying sizes without the need for organic gloss agents or surfactants.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If conventional electroless tin plating baths are used, then initial plating rate is high, but plating rate decreases significantly over time

Engineering Contradiction:

Improveplating rateVSAvoidplating bath stability over time

Core Design Contradiction:

SpeedVSDuration of action of moving object

Solution Approach 1:

The patent applies parameter changes by carefully controlling the pH value within a specific range (5 to 10.5) and adjusting the concentrations of titanium ions and sulfur compounds to achieve optimal plating performance. This resolves the contradiction by maintaining stable plating conditions over extended periods while preserving high plating rates

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite plating bath composition containing multiple components: titanium ions as reducing agent, sulfur compounds as accelerators, and complexing agents. This composite approach allows the system to maintain both high initial plating rates and long-term stability, resolving the contradiction between speed and duration

Inventive Principle:

Principle #40Composite materials

2Ease of operation

If immersion plating is used for electroless plating of tin, then no electrical connection is needed, but deposit thickness is limited and deposition rate decreases with increasing layer thickness

Engineering Contradiction:

Improveoperation simplicityVSAvoiddeposit thickness control

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent changes the chemical parameters of the plating bath, specifically using titanium ions with appropriate concentration ratios and pH control, to enable consistent deposition of thick tin layers (5-20 μm) without the rate decrease that plagues conventional immersion plating

Inventive Principle:

Principle #35Parameter changes

3Productivity

If conventional tin plating baths are used, then plating process can be performed, but deposit homogeneity is poor especially on substrates of different sizes

Engineering Contradiction:

Improveplating throughputVSAvoiddeposit homogeneity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent employs parameter changes including pH control (5-10.5) and the addition of complexing agents to achieve uniform current distribution and consistent deposition rates across substrates of varying sizes and geometries, resolving the contradiction between productivity and precision

Inventive Principle:

Principle #35Parameter changes

4Ease of manufacture

If conventional electroless tin plating baths are used, then plating can proceed, but plate-out occurs making thickness control difficult

Engineering Contradiction:

Improveprocess feasibilityVSAvoiddeposit thickness control

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies parameter changes by maintaining pH within 5-10.5 and optimizing titanium ion concentrations to prevent spontaneous reduction and plate-out, ensuring reliable thickness control while maintaining process feasibility

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces complexing agents as intermediaries that stabilize the tin ions in solution, preventing premature reduction and plate-out while allowing controlled deposition on the substrate surface

Inventive Principle:

Principle #24Intermediary (Mediator)

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 achieves a stable and high plating rate for several hours, maintaining consistent deposit thickness and homogeneity, overcoming the limitations of conventional baths by minimizing the loss of plating rate over time and preventing plate-out, resulting in glossy, defect-free tin deposits.

Implementation Method 1

titanium ions as reducing agent suitable to reduce tin ions to metallic tin

Methodology Applied

Scientific EffectReduction: Reduction

Implementation Method 2

an electroless plating method needs to be applied

Methodology Applied

Scientific EffectElectroless plating: Deposition (physical)

Data Source

PatentEP3770298A1Tin plating bath and a method for depositing tin or tin alloy onto a surface of a substrate

Publication Date: 2021.01.27 ATOTECH DEUT GMBH & CO KG

AI summary

The present invention concerns a tin plating bath comprising tin ions; titanium ions as reducing agent suitable to reduce tin ions to metallic tin; and at least one compound selected from the group consisting sulfites, dithionites, thiosulfates, tetrathionates, polythionates, disulfites, sulfides, disulfide, polysulfide, elemental sulfur or mixtures thereof. The present invention further discloses a method of depositing tin or a tin alloy onto a surface of a substrate. The tin plating bath is particularly suitable to be used in the electronics and semiconductor industry.