Electroplating Apparatus Double-Sided Solar Cell Plating
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Solution Overview
Problem
Conventional solar cell manufacturing methods, such as screen-printing silver paste, result in high series resistance, increased material costs, and limited line width and height for silver electrodes, which are not suitable for high-efficiency solar cells, while electroplating offers lower resistance but with challenges in throughput and uniformity.
Innovation Solution
An electroplating apparatus with double-arm wafer-holding jigs that allow simultaneous plating of both sides of solar cells in a tank filled with an electrolyte solution, featuring spring-loaded pins for electrical coupling and adjustable gaps to enhance uniform metal deposition, and an auxiliary anode for improved field distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If screen-printing Ag paste is used to form the Ag grid, then the manufacturing process is simple and well-established, but the series resistance is high and material cost increases
Solution Approach 1:
The invention changes the fundamental parameter of metal deposition from screen-printing Ag paste to electroplating of Cu or Ag. This parameter change transforms the resistivity from 5×10^-6 to 8×10^-6 ohm-cm (screen-printed) down to 2×10^-6 to 3×10^-6 ohm-cm (electroplated), directly resolving the high series resistance issue while maintaining manufacturing feasibility through the electroplating process
2Ease of manufacture
If screen-printing Ag paste is used, then the process is well-established, but the line width is wide and line height is limited
Solution Approach 1:
The invention changes the deposition method parameter from screen-printing to electroplating, enabling precise control of line width and height. Electroplating allows lines narrower than 100 microns to be achieved, and line height can be precisely controlled by adjusting plating time and current density, overcoming the 25 micron height limitation and 100-120 micron width constraint of screen-printing
3Device complexity
If conventional single-sided electroplating is used, then the equipment is simple, but the throughput is low
Solution Approach 1:
The invention segments the wafer substrate into multiple positions on a single holder, allowing simultaneous electroplating of multiple wafers in series. The holder includes multiple wafer positions with independent electrical connections, enabling parallel processing that dramatically increases throughput while maintaining relatively simple equipment architecture
Solution Approach 2:
The wafer holder serves multiple functions: it holds multiple wafers simultaneously, provides electrical connections to each wafer, and enables both front and back surface plating. This multi-functionality increases productivity without proportionally increasing equipment complexity
4Manufacturing precision
If multiple printing is used to increase line height, then the line height increases, but the line width increases and productivity decreases
Solution Approach 1:
The invention changes from multiple sequential printing operations to a single electroplating operation that can achieve greater line heights. By controlling plating time and current density, the desired line height is achieved in one step rather than multiple prints, maintaining productivity while achieving the required geometric precision
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 apparatus significantly increases throughput by enabling simultaneous double-sided plating of solar cells, reducing material costs and achieving lower resistivity metal grids suitable for high-efficiency solar cells, while maintaining uniformity and efficiency in metal deposition.
Implementation Method 1
Another solution is to electroplate a metal grid, which can include one or more metal layers, directly on the Si emitter or on a TCO layer above the emitter. The electroplated metal grid tend to have lower resistance (the resistivity of plated Cu is typically between 2×10−6 and 3×10−6 ohm-cm) than the printed metal grid.
Implementation Method 2
a respective wafer-holding jig includes a common connector electrically coupled to the cathode and a pair of wafer-mounting frames electrically coupled to the common connector
Data Source
AI summary
One embodiment provides an electroplating apparatus, which includes a tank filled with an electrolyte solution, a number of anodes situated around edges of the tank, a cathode situated above the tank, and a plurality of wafer-holding jigs attached to the cathode. A respective wafer-holding jig includes a common connector electrically coupled to the cathode and a pair of wafer-mounting frames electrically coupled to the common connector. Each wafer-mounting frame includes a plurality of openings, and a respective opening provides a mounting space for a to-be-plated solar cell, thereby facilitating simultaneous plating of front and back surfaces of the plurality of the solar cells.