Embossed Copper Bonding Ribbons for Cleaner Laser Bonding

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Solution Overview

Problem

Current methods for producing bonding wires for laser bonding, such as mechanical and chemical roughening, often result in residues and imperfections that lead to unreliable connections and material spattering, while also being complex and costly.

Innovation Solution

A method involving pressing depressions onto a copper wire precursor using rollers with a relief pattern, followed by annealing, to create a wire with defined roughness that enhances laser radiation absorption and reduces impurities, using embossing or other techniques like punch marking, notching, or stamping.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If mechanical roughening methods (brushing) are used to increase surface area for laser absorption, then laser radiation absorption is improved, but residues and abrasion products are generated that lead to unreliable bonds and spattering

Engineering Contradiction:

Improvelaser radiation absorptionVSAvoidbond connection reliability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

Instead of removing material to create surface roughness (brushing), the invention applies material deformation through embossing to create depressions. This inverts the approach from subtractive to additive/deformative processing, achieving surface area increase without generating harmful residues that cause spattering and bond failures.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention changes the physical state and morphology of the wire surface by applying controlled plastic deformation through embossing rollers. This transforms the surface geometry to create depressions with specific depth and distribution parameters, optimizing laser absorption while maintaining material integrity and avoiding residue generation.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If chemical etching methods are used to create surface depressions, then laser radiation absorption is improved, but the process complexity and cost increase due to masking steps

Engineering Contradiction:

Improvelaser radiation absorptionVSAvoidprocess complexity

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The invention replaces complex chemical etching processes with a mechanical embossing system. Instead of using chemicals and masking steps to create surface depressions, mechanical rollers with embossing patterns directly deform the wire surface, dramatically simplifying the process while achieving the same functional result of increased laser absorption.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention extracts and eliminates the complex masking steps and chemical processing stages from the traditional etching process. By using direct mechanical embossing, the essential function of creating surface depressions is achieved without the unnecessary complexity of chemical containment, masking application, and chemical waste management.

Inventive Principle:

Principle #2Taking out (Extraction)

3Use of energy by moving object

If material removal methods are used to create roughness, then laser absorption is improved, but material loss and spattering increase

Engineering Contradiction:

Improvelaser radiation absorptionVSAvoidmaterial loss

Core Design Contradiction:

Use of energy by moving objectVSLoss of substance

Solution Approach 1:

Instead of removing material to create surface roughness, the invention deforms and redistributes existing material through embossing to form depressions. This inverts the subtractive approach to a deformative approach, maintaining 100% material utilization while achieving the desired surface morphology for enhanced laser absorption.

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

The method produces wires with improved absorption of laser radiation, reduced impurities, and enhanced bonding reliability, while simplifying the production process and reducing costs by avoiding material removal and complex masking steps.

Implementation Method 1

roughened surfaces demonstrate greater absorption of electromagnetic radiation due to their increased surface area

Methodology Applied

Scientific EffectAbsorption of electromagnetic radiation: Absorption (EM radiation)

Implementation Method 2

the energy required for bonding is transferred to the bonding wire by means of laser beams

Methodology Applied

Scientific EffectLaser heating: Laser

Data Source

PatentUS20230386706A1Production of surface-modified cu ribbons for laser bonding

Publication Date: 2023.11.30 HERAEUS ELECTRONICS GMBH & CO KG

AI summary

The invention relates to a method for producing a wire, having at least the following steps: (i) providing a wire precursor; (ii) pressing depressions on the wire precursor and optionally reshaping the wire precursor in the process, and (iii) annealing the wire precursor provided with depressions in order to form the wire; wherein the wire has a content of at least 95 wt. % of copper based on the total weight of the wire. The invention additionally relates to a wire which can be obtained according to the aforementioned method and to the use of a roller in order to produce the wire and/or in order to set the roughness at at least one location of the wire.