Bottom-Mounted Eductor Hydrodynamics for Uniform Copper Plating

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Solution Overview

Problem

The challenge in achieving uniform copper deposition on printed circuit boards and other workpieces is exacerbated by variations in solution flow velocity across the surface, leading to non-uniform thickness distribution and performance issues, particularly with the use of eductors which create glancing effects and complexity in plating cell design.

Innovation Solution

The method involves controlling hydrodynamics in a plating cell by using variable high-velocity eductor-induced agitation, lateral oscillation of the workpiece, an anode chamber, adjustable anode-to-workpiece distance, and non-conducting shielding to achieve uniform solution flow velocity, reducing the coefficient of variability (CoV) to less than 10%.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If eductors are used to provide solution flow velocity, then solution movement is enhanced, but non-uniform deposition and glancing effects occur

Engineering Contradiction:

Improvesolution flow velocityVSAvoiddeposition uniformity

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

The patent inverts the conventional eductor configuration by positioning the eductor at the bottom of the cell rather than at the top, and directs the fluid jet vertically upward through the electrolyte to the workpiece. This inversion eliminates the glancing effect that occurs with conventional top-mounted eductors, as the fluid flow impinges perpendicularly on the workpiece surface, resulting in uniform solution flow velocity and uniform copper deposition across the entire workpiece surface.

Inventive Principle:

Principle #13The other way round (Inversion)

2Speed

If air sparging is used to create solution movement, then electrolyte flow is generated, but oxidation of electrolyte and workpiece features occurs

Engineering Contradiction:

Improvesolution movement rateVSAvoidoxidation

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The patent replaces the chemical oxidation mechanism of air sparging with a mechanical fluid circulation system. Instead of introducing air bubbles that cause oxidation, the system uses an eductor to create a controlled liquid jet that circulates electrolyte through the cell. This mechanical substitution eliminates oxidation of the electrolyte and workpiece features while maintaining effective solution movement and hydrodynamics.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Speed

If eductors are positioned horizontally opposite the workpiece surface, then solution flow is directed onto the workpiece, but variations in solution flow velocity occur across the surface

Engineering Contradiction:

Improvesolution flow velocityVSAvoidflow velocity uniformity

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

The patent inverts the eductor positioning from horizontal/opposite configuration to vertical/bottom-mounted configuration. The eductor jet is directed upward perpendicular to the workpiece surface, creating uniform flow velocity distribution across the entire workpiece area. This vertical orientation eliminates the velocity variations that occur with horizontal eductor positioning.

Inventive Principle:

Principle #13The other way round (Inversion)

4Manufacturing precision

If workpiece movement is implemented to achieve uniform deposition, then deposition uniformity improves, but device complexity increases

Engineering Contradiction:

Improvedeposition uniformityVSAvoidplating cell design complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Instead of moving the workpiece to achieve uniform deposition, the patent inverts the approach by creating uniform solution flow velocity through proper eductor positioning and orientation. The eductor is positioned at the bottom and directed vertically upward, generating uniform hydrodynamics across the workpiece surface without requiring any workpiece movement mechanisms, thereby simplifying the overall system design.

Inventive Principle:

Principle #13The other way round (Inversion)

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 approach results in a more uniform metal deposit distribution across the workpiece, minimizing variations in copper thickness and enhancing the plating process's reliability and efficiency, especially for complex features like through holes and vias.

Implementation Method 1

Eductors are nozzles which utilize venturi effects to provide up to five times the solution flow velocity output of the pump which feeds the eductors.

Methodology Applied

Scientific EffectVenturi effect: Venturi Effect

Implementation Method 2

The movement of air bubbles (106) from the bottom to the top of the plating cell (100) creates solution movement

Methodology Applied

Scientific EffectBuoyancy: Archimedes' Principle (Buoyancy)

Implementation Method 3

the challenge of leveling or throwing power in the metal electrodeposition process

Methodology Applied

Scientific EffectElectrodeposition: Electrodeposition

Data Source

PatentUS7947161B2Method of operating an electroplating cell with hydrodynamics facilitating more uniform deposition on a workpiece with through holes

Publication Date: 2011.05.24 FARADAY TECHNOLOGY INC

AI summary

A method and apparatus for establishing more uniform deposition across one or more faces of a workpiece in an electroplating process. The apparatus employs eductors in conjunction with a flow dampener member and other measures to provide a more uniform current distribution and a more uniform metal deposit distribution as reflected in a coefficient of variability that is lower than conventional processes.