Preparation And Properties Of Spherical Silver Powder, Organic Carrier And Positive Silver Slurry

The silver paste is widely used in the preparation of solar cells.In this paper the preparation of positive conductive silver paste for solar cells was studied; And the preparation of micro level spherical silver powders was studied in this paper; And in addition, the preparation of organic carrier with levels volatile was explored in this paper; Finally,the effect of the component content and the sintering process on the performance of silver paste was discussed in this paper.Emulsion dispersion mechanism was firstly adopted to manufacture spherical silver powders by chemical reduction method.In this experiment,Span85 and Tuwen80 were chosen to be compound emulsifier, and W/O emulsion was made by adjusting the HLB value, emulsification speed and other system parameters, and then the mono-disperse and uniform particle size distribution of the micron grade spherical silver powders were prepared by chemical reduction method. It was found that the best preparation conditions for the spherical silver powders: reaction temperature under 35℃, emulsifying for 10 min,emulsifying speed of 14000 r/min, reaction liquid concentration is 0.5 mol/L, emulsifier content is 9%, HLB value of 3.5.The organic carrier with level volatile and good thixotropy was studied in this Experiment.The turpentine,1,4-butyl ester, glycerin, phthalic acid dibutyl were added into the terpineol and ethyl cellulose-butyl carbitol system to regulating organic carrier’s volatility.Furthermore,the hydrogenated castor oil and polyamide wax were added into the organic carrier respectively to explore their effect on thixotropy of organic carrier.It was found that when the turpentine was 10%,1,4-butyrolactone was 15%, terpineol was 35%, butyl carbitol was 10%, glycerin was 10%, phthalic acid dibutyl was 10% the solvent had good volatile that the organic carrier can volatile evenly, then it could avoid pores caused by the concentrated volatile.In addition, when the mass fraction of polyamide wax was 0.4%,the thixotropic index was 1.9, the organic carrier had good thixotropy which can effectively improve the silver conductive paste printing.Positive conductive silver paste for solar cells was made by silver powder in this subject.The silver paste contents were as follows:glass frit content was 4.5%,silver powders content was 84%,organic carrier was 9.6%,and turpentine content was 1.9%.The experimental results show that:The silver paste made by spherical silver powders with the average particle size 0.91 μm had highest conductivity;In addition,comprehensive consideration of silver paste electrical resistivity and adhesion the silver paste had better performance when the sintering temperature was 850℃ and holding time was 40s,and the silver film resistivity was 33.3μΩ. cm, and the silver film adhesion was 3.193 N.In addition, added nano scale spherical silver powders or flake silver powder into the spherical silver powders was helpful to improve the electrical conductivity of the paste, when adding 4wt% nano spherical silver powders of the total silver powders, its conductivity is 30.9μΩ. cm, and the adhesion was 3.253 N.When the flake silver powders was added into the paste with 8wt% ratio of the total silver powders, the conductivity of the paste film was 27.7μΩ. cm,and the adhesion was 3.478 N.