Micro-extrusion Printhead with Offset Orifices for Octagonal Solar Substrates
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Solution Overview
Problem
Conventional micro-extrusion systems are inefficient in producing H-pattern solar cells on octagonal mono-crystalline silicon substrates due to the inability to individually control extrusion material, leading to short-circuits and increased manufacturing costs, and require significant modifications to existing equipment.
Innovation Solution
A micro-extrusion printhead and system optimized for octagonal substrates that extrude longer central and shorter side gridlines in a step pattern, with a printhead design featuring offset nozzle channels and separate valves for each set of nozzle orifices, allowing for simultaneous extrusion and precise control of gridline endpoints to avoid short-circuits and minimize waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional micro-extrusion systems are used on octagonal substrates, then existing equipment can be utilized, but gridline material cannot be individually controlled leading to short-circuits and increased manufacturing costs
Solution Approach 1:
The printhead is divided into multiple independently controllable nozzle groups, each with its own valve. This segmentation allows individual control of gridline material extrusion at different locations, preventing short-circuits while maintaining compatibility with existing micro-extrusion equipment architecture.
Solution Approach 2:
The system implements dynamic control of nozzle valves based on real-time substrate position and gridline requirements. Valves are opened and closed sequentially as the printhead moves across the octagonal substrate, enabling precise control of gridline material deposition patterns to avoid short-circuits.
2Ease of manufacture
If conventional printhead design is used, then manufacturing is simpler, but significant modifications are required to produce gridlines on octagonal substrates
Solution Approach 1:
The printhead design maintains universal compatibility with existing micro-extrusion systems while adding multi-functionality to handle both square and octagonal substrates. The same printhead can be used for different substrate types by adjusting valve control sequences, avoiding the need for completely different equipment.
Solution Approach 2:
The system achieves adaptability through parameter changes in valve control timing and duration rather than physical modifications to the printhead structure. By changing control parameters, the same hardware can produce different gridline patterns for different substrate geometries.
3Ease of operation
If gridline material is extruded without individual control, then the process is simpler, but ink waste increases and cell efficiency is compromised
Solution Approach 1:
The valve control system employs periodic opening and closing actions synchronized with printhead movement. Each valve is activated only during the specific time window when its corresponding nozzles need to deposit gridline material, minimizing ink waste while maintaining simple extrusion operation.
Solution Approach 2:
The system uses feedback from substrate position sensing to control valve activation. This feedback mechanism ensures valves are opened and closed at the correct moments, preventing both short-circuits and unnecessary ink deposition, thereby reducing waste while keeping the process straightforward.
4Ease of manufacture
If uniform gridlines are printed across the entire substrate, then the process is more straightforward, but gridlines may extend beyond wafer edges causing short-circuits
Solution Approach 1:
The gridline printing process is segmented into multiple zones corresponding to different nozzle groups. Each zone is controlled by its own valve, allowing the endpoint of gridlines to be precisely controlled by closing the appropriate valve when the printhead reaches the wafer edge, preventing extensions beyond the substrate.
Solution Approach 2:
Different nozzle groups are activated based on local requirements of the substrate geometry. Near the wafer edges, valves are closed earlier to prevent gridline extensions, while in central regions, valves remain open longer. This local quality approach maintains simple printing processes while achieving precise endpoint control.
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 the production of H-pattern solar cells with minimal ink waste, no corner masking required, and no risk of printing beyond the wafer edge, while maintaining cell efficiency and allowing for substitution on existing machines with minimal effort, thus reducing manufacturing complexity and cost.
Implementation Method 1
a first plurality of nozzle channels (162-1) disposed in a central cross-process region (X1) of the printhead and configured to receive a first portion of the conductive material from a material feed system (60) by way of a first flow channel (115-1) and extrude the first portion of the conductive material through a first set of outlet orifices (169-1)
Data Source
AI summary
A solar cell extrusion printing system that uses a micro-extrusion printhead to print longer central gridlines and one or more pairs of shorter “side” gridlines such that end points of the gridline sets form step patterns on an octagonal (pseudo-square) substrate. The printhead includes a set of central nozzles that receive ink from a first valve by way of a first flow channel to print the longer central gridlines, and additional sets of side nozzles that receive ink from additional valves by way of additional flow channels to print the shorter “side” gridlines. The central nozzles have outlet orifices that offset in the process direction from side outlet orifices of the side nozzles. A start signal is simultaneously sent to the valves such that ink is substantially simultaneously extruded through both the central and side orifices, whereby the extruded ink produces gridline endpoints having the desired step pattern.