Electron Attachment Oxide Removal for Solder Joints

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Solution Overview

Problem

Current methods for removing metal oxides from substrates during solder reflow processes are inefficient, often requiring fluxes that can create voids, contaminate the environment, or necessitate expensive vacuum equipment, and fail to operate effectively at low temperatures or ambient pressure.

Innovation Solution

A method and apparatus using negatively charged reducing gas ions generated by electron attachment to reduce metal oxides on substrates without fluxes, employing a system with electrodes and a gas mixture that allows for efficient oxide removal at near-ambient pressure and low temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If fluxes are applied to remove metal oxides during solder reflow, then oxide removal effectiveness is improved, but void formation and flux residue contamination occur

Engineering Contradiction:

Improveoxide removal effectivenessVSAvoidvoid formation and flux residue

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The invention extracts and eliminates the flux component from the oxide removal process. Instead of applying flux to remove oxides, the process uses a controlled atmosphere of reducing gas (such as hydrogen or carbon monoxide) that directly reduces metal oxides to metals through chemical reaction, thereby removing the source of void formation and flux residue contamination while maintaining effective oxide removal

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention introduces a reducing gas as an intermediary substance to facilitate oxide removal. The reducing gas acts as a mediator that chemically reacts with metal oxides to produce metal and gaseous byproducts, enabling oxide removal without direct contact between solder and flux, thus preventing void formation and residue accumulation

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If vacuum equipment is used to remove metal oxides, then oxide removal capability is improved, but processing cost and system complexity increase

Engineering Contradiction:

Improveoxide removal capabilityVSAvoidvacuum equipment requirement

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention replaces the mechanical vacuum system with a chemical reduction process. Instead of using vacuum equipment to physically remove or prevent oxide formation, the process employs reducing gas that chemically converts metal oxides back to metals through reduction reactions, thereby achieving oxide removal capability without complex vacuum equipment

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the chemical parameters of the processing atmosphere by introducing reducing gases (such as hydrogen, carbon monoxide, or their mixtures) at controlled concentrations and temperatures. This parameter change enables oxide removal through chemical reduction rather than mechanical vacuum, simplifying the equipment requirements while maintaining effective oxide removal capability

Inventive Principle:

Principle #35Parameter changes

3Reliability

If high temperatures are used for oxide removal, then reduction effectiveness is improved, but energy consumption and processing cost increase

Engineering Contradiction:

Improvereduction effectivenessVSAvoidprocessing temperature

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The invention optimizes the temperature parameter by utilizing reducing gases that can effectively reduce metal oxides at lower temperatures compared to conventional methods. The presence of reducing gas molecules that readily donate electrons to oxide ions enables the reduction process to proceed at reduced temperatures, thereby maintaining reduction effectiveness while decreasing energy consumption and processing costs

Inventive Principle:

Principle #35Parameter changes

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 enables effective removal of metal oxides at lower temperatures and ambient pressure, reducing processing costs and environmental impact while improving the quality of solder joints and substrate preparation.

Implementation Method 1

A method and apparatus using negatively charged reducing gas ions generated by electron attachment to reduce metal oxides on substrates without fluxes

Methodology Applied

Scientific EffectElectron attachment:

Implementation Method 2

contacting the treating surface with the negatively charged reducing gas to reduce the metal oxides on the treating surface of the substrate

Methodology Applied

Scientific EffectChemical reduction: Reduction

Data Source

PatentUS8454850B2Method for the removal of surface oxides by electron attachment

Publication Date: 2013.06.04 AIR PROD & CHEM INC

AI summary

Described herein are a method and an apparatus for removing metal oxides and/or forming solder joints on at least a portion of a substrate surface within a target area. In one particular embodiment, the method and apparatus form a solder joint within a substrate comprising a layer having a plurality of solder bumps by providing one or more energizing electrodes and exposing at least a portion of the layer and solder bumps to the energizing electrode.