Ultrasonic Bonding System for Dual-Sided Solar Substrate Interconnection
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Solution Overview
Problem
Current methods for electrical interconnection in solar substrates, such as soldering, face limitations in cost, reliability, yield, and compliance with lead-free requirements, particularly in forming connections on both sides of crystalline silicon solar cells.
Innovation Solution
An ultrasonic bonding system with dual bonding tools, one positioned above and one below the workpiece, allows for simultaneous or sequential bonding of conductive materials to both sides of a solar substrate, reducing handling and potential damage, and enabling efficient electrical interconnection without the need to flip the workpiece.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soldering is used for electrical interconnection in solar substrates, then electrical connections can be formed, but cost increases, reliability decreases, and lead-free compliance becomes difficult
Solution Approach 1:
The patent replaces the thermal-mechanical soldering process with an ultrasonic bonding process that uses mechanical vibration at high frequency. The ultrasonic bonding tool applies vibrational energy to directly bond conductive materials to solar cell contacts without melting solder, thereby eliminating the harmful effects of soldering while achieving reliable electrical interconnection.
Solution Approach 2:
The patent changes the bonding parameters from high-temperature soldering to low-temperature ultrasonic vibration. By using ultrasonic frequencies (typically 20-100 kHz) and controlled bonding forces, the process achieves reliable bonds without the thermal damage and material consumption associated with soldering, reducing cost and improving compliance with lead-free requirements.
2Productivity
If conventional single-sided bonding is used, then bonding can be performed, but the workpiece must be flipped increasing handling complexity and potential damage
Solution Approach 1:
The patent combines two bonding operations (front-side and back-side bonding) into a single integrated process. By positioning bonding tools on both sides of the solar substrate simultaneously, the system performs dual-sided bonding without requiring the workpiece to be flipped, thereby increasing productivity and reducing handling complexity in one unified operation.
Solution Approach 2:
The patent transitions from sequential single-sided bonding to simultaneous dual-sided bonding by utilizing the third dimension (through the substrate). The bonding tools are positioned on opposite sides of the solar cell, allowing parallel operation that eliminates the need for flipping and reduces overall process time.
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 enhances the efficiency and reliability of electrical interconnections on solar substrates by minimizing handling and equipment costs, while ensuring compliance with lead-free requirements and improving yield.
Implementation Method 1
an upper terminal end of a bonding tool is typically engaged in an ultrasonic transducer which causes the bonding tool to vibrate during bonding
Implementation Method 2
Ultrasonic bonding typically uses relative motion between (1) the bonding material and (2) a bonding location to form a bond therebetween
Data Source
AI summary
An ultrasonic bonding machine is provided. The ultrasonic bonding machine includes a support structure configured to support a workpiece during a bonding operation. The ultrasonic bonding machine further includes an upper bonding tool positioned above the support structure and configured for bonding an upper bonding material to an upper side of the workpiece, and a lower bonding tool positioned below the support structure and configured for bonding a lower bonding material to a lower side of the workpiece. The ultrasonic bonding machine may also be an ultrasonic ribbon bonding machine configured to bond an upper and lower conductive ribbon to a solar substrate.