High productivity in-line screen printing system for crystalline solar cell manufacturing
To develop a high performance in-line screen-printing system, the NPC Group defined an appropriate benchmark for characterizing the industrial efficiency of the operation and carried out a full analysis of the factors affecting this benchmark. A screen-printing system design based on careful cost analysis can produce a machine with a high effective throughput and low cell breakage. As a result, NPC is now offering advanced in-line, high precision systems to the photovoltaic industry. Future design changes results in machine speeds of 1,600 wafers per hour at a breakage below 0.5% for the three prints typical of the current cell manufacturing process.
Processing of crystalline silicon solar cells in high throughput production tools
The contribution of breakage-induced yield losses in solar cell and module manufacturing costs is well understood. Breakage data and information about the solutions implemented by cell manufacturers have a proprietary nature and are much less well known. The emergence of equipment manufacturers serving many customers is enabling solutions that are of common interest to the industry to become better known. In this paper we discuss the cell handling requirements of crystalline silicon solar cell manufacturers and present data obtained with two machines designed and manufactured by the NPC Group and used in cell testing and module assembly operations. On this basis, we propose topics where industry collaboration with the research community could result in advantages for all cell manufacturers.
Submicron polymer structures with X-ray lithography and hot embossing
This article describes the process chain for replication of submicron structures with varying aspect ratios (AR) up to 6 in polymethylmethacrylate (PMMA) by hot embossing to show the capability of the entire LIGA process to fabricate structures with these dimensions. Therefore a 4.7 μm thick layer of MicroChem 950k PMMA A11 resist was spin-coated on a 2.3 μm Ti/TiOx membrane. It was patterned with X-ray lithography at the electron storage ring ANKA (2.5 GeV and λc ≈ 0.4 nm) at a dose of 4 kJ/cm3 using a Si3N4 membrane mask with 2 μm thick gold-absorbers. The samples were developed in GG/BDG and resulted in AR of 6–14. Subsequent nickel plating at 52°C resulted in a 200 μm thick nickel tool of 100 mm diameter, which was used to replicate slit-nozzles and columns in PMMA. Closely packed submicron cavities with AR 6 in the nickel shim were filled to 60% during hot embossing.