DocumentCode :
1561386
Title :
Aluminum pastes (lead-free/low-bow) for thin wafers
Author :
Kim, S. ; Sridharan, S. ; Khadilkar, C. ; Shaikh, A.
Author_Institution :
Ferro Corp. Tech. Center, Vista, CA, USA
fYear :
2005
Firstpage :
1100
Lastpage :
1102
Abstract :
Presently, a typical thickness of the silicon wafer used by the solar cell industries is about 280∼330 μm. The industry trend is to use thinner wafers to reduce the cost of solar cells. The wafer cost is about 60% of the cell fabrication cost. Going-forward industry is targeting thickness of <250 μm. As the wafer thickness decreases, the bowing of the cell due to the sintering stress generated by aluminum increases. Also, the industries are trying to make cells with metal pastes which do not contain lead due to the environment concern. Present aluminum pastes contain lead-based glass and make finished cells bow after firing. This paper deals with a development of lead-free aluminum paste for thin wafers. A typical aluminum paste contain metal powders, glasses, and additives mixed in an organic medium. The effect of paste variables such as metal powder, glass chemistry and additives on electrical performance and bowing was investigated. Also the effect of aluminum paste deposit amount on bending and the effect of aluminum paste deposit amount and firing temperature on BSF layer were studied. Based on this study new lead-free/low-bow aluminum pastes are developed. Newly developed lead-free low-bow aluminum paste (B) and (C) shows only 0.6 and 0.4 mm of bowing respectively on 240 μm thick × 5" × 5" poly crystal wafer when the wet deposition amount is ∼1.14 gram per wafer.
Keywords :
additives; aluminium; bending; firing (materials); glass; powders; solar cells; 240 mum; 5 inch; Al; additives; bending; cell fabrication cost; firing; glass chemistry; lead-based glass; lead-free low-bow aluminum paste; metal powders; silicon wafer; sintering stress; solar cell industries; thin wafers; wet deposition; Additives; Aluminum; Costs; Environmentally friendly manufacturing techniques; Fabrication; Glass; Photovoltaic cells; Powders; Silicon; Stress;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Photovoltaic Specialists Conference, 2005. Conference Record of the Thirty-first IEEE
ISSN :
0160-8371
Print_ISBN :
0-7803-8707-4
Type :
conf
DOI :
10.1109/PVSC.2005.1488327
Filename :
1488327
Link To Document :
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