The impact of solvent characteristics on performan

Authors: Bruce Philip Eifion Jewell David Worsley

Publish Date: 2016/07/25

Volume: 13, Issue: 5, Pages: 911-920

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Abstract

Carbon conductive pastes deposited by screen printing are used in many commercial applications including sensors PCB batteries and PV and as such represent an important valueadded coating An experimental investigation was carried out into the role of the solvent on the drying characteristics conductivity and process consistency in screen printed carbon pastes Four materials with solvent boiling points between 166 and 219°C were deposited at film thickness between 6 and 16 μm and the sheet resistance and film thickness were measured after successive passes through an industrial dryer operating with an air temperature of 155°C Sheet resistances of 14 Ω/sq were obtained with the thicker films while thinner films produced a sheet resistance of 46 Ω/sq Thinner films achieved a stable resistivity within a 25min residence time while the thicker films required a residence time in excess of 125 min to achieve a stable resistivity As well as prolonging drying times the higher boiling point increased the resistivity of the cured film It is postulated that the lower resistance of the faster drying materials is a result of film stressing increasing inter particle contact Process models indicate that multiple thin layers are a more efficient means of manufacture for the process parameters examinedCarbon conductive coatings are of high added value and have found widespread use in the electrochemical sensors1 PCB resistors2 printed heating elements3 electromagnetic shielding batteries4 and supercapacitors5 and are increasingly being considered as electrodes for DSSC67 and perovskite PV cells89 They therefore represent a useful material set with application in many growing industries The dominant manufacturing method being used is screen printing where paste materials are formulated such that they can be deposited on a fixed film thickness using a relatively simple patterning processCarbon/graphite materials are considered commercially mature and little scientific research has been carried out regarding their performance in recent times research focus being concentrated on more research attractive materials such as CNTs MWCNTs graphene and their hybridization with conventional graphite materials10 Some development has been carried out on the manipulation through doping of materials predominantly for bio sensing applications11 Where formulation studies have been carried out these focused on the influence of the carbon/graphite relative proportions12 the carbon/graphite physical and electrical characteristics1314 and the proportion of conductive material required for charge percolation through the cured film15

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