Development of a high-throughput fine line metallization process using CFD-simulation

Abstract

In order to enhance dispensing technology towards an industrial application in Silicon Photovoltaics, in particular throughput rate has to be increased. For this reason, a novel parallel high precision fine line dispensing unit is currently being developed at Fraunhofer ISE providing one nozzle per contact finger and a central Paste supply. In order to ensure a homogeneous paste distribution to all nozzles, the influence of paste rheology on the flow profile of the dispensing nozzles was analyzed. An analytical comparison of two different dispensing pastes with water gave a good insight on the influence of paste rheology on flow patterns inside the dispensing nozzles. Furthermore, numerical CFD-simulation (CFD: Computational Fluid Dynamics) was used to investigate different nozzle geometries and finally print head designs. In various iteration steps, the influence of fabrication tolerances especially concerning the nozzle geometry was isolated and print head designs were optimized based on CFD towards maximum process stability. In the meantime, process optimization using a single nozzle approach led to an average finger width below 35 μm, confirmed by several characterization methods

Printing technologies for silicon solar cell metallization: A comprehensive review

“…Figure 15A presents a microscopic image of the nozzle exit during printing, indicating the working principle of the dispensing approach. Since then, Pospischil et al 245,312–315,349–351,353–358 were able to demonstrate in a series of publications that the parallel dispensing approach for a fine‐line metallization has an enormous potential for industrial application. They have been constantly improving the finger geometry while at the same time scaling up the process from a single nozzle continuous basic dispensing approach towards a multi nozzle dispensing print head for an intermittent process at very competitive industrial process speeds (Figure 15B).…”

“…Figure 15A presents a microscopic image of the nozzle exit during printing, indicating the working principle of the dispensing approach. Since then, Pospischil et al 245,[312][313][314][315][349][350][351][353][354][355][356][357][358] were able to demonstrate in a series of publications that the parallel dispensing approach for a fine-line metallization has an enormous potential for industrial application.…”

Towards 3D-lithium ion microbatteries based on silicon/graphite blend anodes using a dispenser printing technique

“…Depending on the rheological parameters of each slurry, it was necessary to evaluate the correct pressure in order to ensure a sufficient volume ow rate for a given speed (v x,y ) of the table robot. 26,27 Here the pressure was set to 1.2, 1.6, 2.0 and 3.2 bar for the sample with 6 wt%, 12 wt%, 18 wt% and 24 wt% binder, respectively. The diameter of the micro nozzle (Vieweg, Germany) was 110 mm.…”

Paste Development for an Optimized Filament Stretching Effect during Parallel Dispensing on Transparent Conductive Oxide Layers for Solar Cell Metallization

“…To ensure high throughput, numerous nozzles are arranged in parallel. [18,19] Different designs of print heads are commercialized by the Fraunhofer spin-off HighLine Technology GmbH, Germany. [20][21][22] Figure 1 illustrates a great number of influencing factors regarding the dispensing process and its printed structures including their functionality for solar cell metallization.…”