Silicon Casting Top Heater for Crack-Free Ingot Solidification
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Solution Overview
Problem
Existing silicon electromagnetic casting methods face challenges in producing large polycrystalline silicon ingots without cracking, particularly during final solidification, which affects yield and quality when using plasma heating and electromagnetic induction.
Innovation Solution
A silicon electromagnetic casting apparatus with a water-cooling copper mold and a top heater that generates heat through electromagnetic induction, positioned to face the molten silicon surface, is used to control solidification and prevent cracking by maintaining a uniform temperature across the surface, even for ingots larger than 300 mm square.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large square mold (side length 300 mm or more) is used to produce large polycrystalline silicon ingots, then productivity and output are improved, but cracking occurs in the final solidification portion due to non-uniform temperature distribution
Solution Approach 1:
The top heater is divided into multiple independent heating zones along the radial direction. Each zone can be independently controlled to provide localized heating, ensuring uniform temperature distribution across the large mold surface area, which prevents cracking in the final solidification portion while maintaining high productivity
Solution Approach 2:
Different regions of the mold receive different heating intensities through the segmented top heater. The heating power is locally adjusted based on the specific thermal requirements of each region, ensuring that the final solidification portion maintains appropriate temperature to prevent cracking while other regions solidify normally
2Device complexity
If electromagnetic induction heating alone is used, then the apparatus structure is simple and operation is easy, but the temperature distribution on the molten silicon surface is non-uniform, causing cracking during final solidification
Solution Approach 1:
The invention combines electromagnetic induction heating with a top heater system to create a composite heating apparatus. The electromagnetic induction provides bulk heating while the top heater supplies supplemental radiant heat from above, working together to achieve uniform temperature distribution across the molten silicon surface without excessive structural complexity
Solution Approach 2:
The top heater serves multiple functions: it provides supplemental heating during the casting process, maintains uniform temperature distribution across the surface, and specifically prevents cracking during final solidification. This multi-functional component addresses multiple problems simultaneously while adding minimal structural complexity
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 stable production of high-quality polycrystalline silicon ingots without cracking, improving yield and maintaining high conversion efficiency for solar cell applications.
Implementation Method 1
when the silicon material is charged into the mold 1 and a high-frequency induction current is applied to the induction heating coil 2, the material is heated and melted
Implementation Method 2
a plasma torch as a heating source installed above the cold mold so as to be raised or lowered, the plasma torch generating a transferable plasma arc
Implementation Method 3
a top heater configured so as to face a top surface of the molten silicon in the cold mold to generate heat through electromagnetic induction by means of the induction coil
Implementation Method 4
copper plate-shape elements elongated in a vertical direction of which interior can be cooled with water are arranged inside an induction heating coil 2
Data Source
AI summary
Provided is a silicon electromagnetic casting apparatus that is capable of stably producing polycrystalline silicon used as a solar cell substrate material, having a bottomless cold mold and an induction heating coil, the apparatus for pulling down the silicon melted through electromagnetic induction heating by means of the induction coil and solidifying the silicon melt; further including a plasma torch for generating a transferable plasma arc and a top heater configured so as to face a top surface of the molten silicon, the top heater for generating heat through electromagnetic induction by means of the induction coil. The apparatus enables, upon production of a high quality polycrystalline silicon ingot as a solar cell substrate material along with plasma heating, stable production thereof without cracking in a final solidification portion.