Investigation and multi-objective optimization of monocrystalline silicon wafering using wire electro-discharge machining

Abstract

Monocrystalline silicon wafers are widely used as the primary material for solar cell production in the photovoltaic industry, owing to their high efficiency and sleeker aesthetic. Wafering is the primary process towards wafer production. The existing wafering processes have limitations of cracking, chipping, and high kerf loss, arising the need for cost-efficient and precise methods to produce wafers. In the present experimental work, an attempt has been made to explore the potential of Wire Electro-discharge Machining (WEDM) for wafer production and to gain an understanding of the effects caused by pulse on time (Ton), pulse off time (Toff), peak current (Ip), wire tension (WT), and wire feed rate (WFR) during the wafering process to achieve the optimal parametric setting for attaining maximum wafering speed and minimum surface roughness. The work material used was P-type monocrystalline silicon. Wafers thickness of 250 μm was produced, avoiding edge chipping. The experimentation was planned according to the face-centered central composite design. The obtained results were statistically analyzed, and response surface methodology (RSM) was used to model the wafering speed and surface roughness. From the analysis of experimental results, it was noticed that at the higher level of Ton and Ip, a maximum wafering speed of 2.574 mm/min was attained. In contrast, the minimum surface roughness of 1.57 μm was achieved at the lower level of Ton and Ip. The most significant process variables that influence the wafering speed and surface roughness are the Ton, Toff, and Ip. Micrographs of the wafer surface reveal the presence of micro craters, but there was no evidence of micro-cracks. The multi-objective optimization of the responses was done using the desirability approach, and the optimized values of wafering speed and surface roughness attained were 0.989 mm/min and 1.57 μm, respectively.