Dual-Sided Laser Welding for Photovoltaic Cell Interconnection

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Solution Overview

Problem

Existing interconnection methods for photovoltaic cells, particularly in space applications, face challenges due to temperature constraints and thermal expansion issues, leading to material embrittlement and cracking, which are not addressed by conventional brazing or soldering techniques.

Innovation Solution

A laser welding device and method that allows localized fusion of connecting conductors on both sides of photovoltaic cells, enabling interconnection without temperature constraints, using a system with dual laser heads and a conveyor belt for precise alignment and synchronization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If brazing or soldering techniques are used to interconnect photovoltaic cells, then good ohmic contact is achieved, but material embrittlement and cracking occur due to temperature constraints and thermal expansion issues

Engineering Contradiction:

Improveinterconnection reliabilityVSAvoidmaterial strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The interconnection process is segmented into two distinct stages: first, brazing is used to create the initial ohmic contact between conductors and cells; second, ultrasonic welding is applied to reinforce the connection without causing thermal damage. This segmentation allows each process to perform its specialized function optimally.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The interconnection process employs periodic action through sequential application of brazing followed by ultrasonic welding. The ultrasonic welding stage provides periodic mechanical reinforcement to the initially brazed connection, creating a multi-stage bonding process that enhances overall joint strength while maintaining electrical conductivity.

Inventive Principle:

Principle #19Periodic action

2Reliability

If conventional brazing or soldering is used for interconnection, then electrical connection is achieved, but thermal expansion causes embrittlement and cracking

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidthermal expansion damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Ultrasonic welding acts as an intermediary process that reinforces the brazed connection without introducing additional thermal stress. The mechanical energy from ultrasonic vibration creates metallurgical bonding at the interface, providing thermal expansion accommodation while maintaining electrical continuity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The process replaces pure thermal bonding (brazing/soldering) with a mechanical bonding approach using ultrasonic welding. The ultrasonic energy generates localized mechanical deformation and friction at the contact interface, creating a strong mechanical bond that is less sensitive to thermal expansion differences between materials.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Strength

If high temperature welding is used to achieve strong interconnection, then bonding strength is improved, but photovoltaic cells sensitive to high temperatures are damaged

Engineering Contradiction:

Improvebonding strengthVSAvoidprocessing temperature

Core Design Contradiction:

StrengthVSTemperature

Solution Approach 1:

The ultrasonic welding process introduces dynamic mechanical energy through high-frequency vibrations, creating localized bonding at temperatures significantly lower than conventional welding. The dynamic mechanical action generates friction and plastic deformation at the interface, enabling strong bonding without sustained high temperature exposure that would damage temperature-sensitive photovoltaic cells.

Inventive Principle:

Principle #15Dynamics

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

Enables reliable and efficient interconnection of photovoltaic cells with maintained ohmic conductivity, accommodating thermal and mechanical deformations, suitable for various cell types including those sensitive to high temperatures.

Implementation Method 1

a laser welding unit comprising a laser head configured to perform at least one laser shot for the localized fusion of at least one connecting conductor positioned on the front face of said at least one photovoltaic cell

Methodology Applied

Scientific EffectLaser: Laser

Data Source

PatentEP4701374A1Device for interconnecting photovoltaic cells

Publication Date: 2026.02.25 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

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AI summary

The invention relates to a laser welding interconnection device (100) of photovoltaic cells (4) to form at least one string of photovoltaic cells (4) interconnected by connecting conductors (6), characterized in that it comprises: a deposit zone (ZD) of at least one photovoltaic cell (4) including a through opening (O) configured to expose the front and rear faces of said at least one photovoltaic cell (4); a first laser welding unit (20) including a first laser head (20t) configured to perform at least one laser shot on the front face; and a second laser welding unit including a second laser head configured to perform at least one laser shot on the rear face, the first (20) and second laser welding units being located on either side of the through opening (O).