Preparation And Properties Of Copper Paste

The common conductive phases in conductive paste are Pt,Pd,Au and Ag etc. and the silver conductive paste has been widely used. However,in recent years,the inexpensive conductive paste becomes the future development because the cost of conductive paste has been increased due to an increasing cost of expensive metals and the migration of silver ions.In this paper,the modification processing of copper powder surface,the ratio of raw materials and sintering processing have been studied to resolve the easier ox idation and aggregation,low bonding strength,poor electrical conductivity and mec hanic property etc.. A industrial production processing to prepare the good electrical conductivity,environment friendly and long storage copper paste has been optimize d and presented. The copper powder,glass powder and copper paste have been cha racterized by X-ray diffraction(XRD),scanning electron microscopy(SEM), El ectron Energy Disperse Spectroscopy(EDS),and four probe resistance test etc.. Th e main results are followed:1. The Cu has been prepared by the liquid reduction of Cu2+using L-ascorbic acid as the reducing and stable agent and the PVP as the dispersing agent. The o ptimized processing are: 1) m(1μm copper powders):m(L-ascorbic acid):m(PVP)=67~80:15~25:5~11; 2) m(15μm copper powders):m(L-ascorbic acid):m(PVP)=59~71:20~25:5~16.The best resistance of prepared conducting copper film after sintering according to t he previous two ratios are 18.505 mΩ/□ and 15.15mΩ/□,respectively,which prese nted the reducing mechanism of oxidation of copper powder surface.2. The optimized ratios for 1μm and 15μm copper powders,using the glass p owder as the addition,copper powder with small size and irregular shape as the co nducting phase and the ethyl cellulose,Ethyl acetate and linalool etc. as the organi c solvent,are: 1) m(1μm copper powders):m(15μm copper powders)=10~15:85~90; 2) m(copper powders):m(glass powders + organic solvent)=75~85:15~25. The prepared copper film sintere d at 450℃ in N2 atmosphere shows the flat surface,high density,low porosity,a nd excellent electrical conductivity,which is 21.08mΩ/□. The small size and irregul3. irregular shape copper powders can improve the electrical conductivity of c opper paste showing the good silk screen printing.4. The prepared copper film at high temperature sintering using the best optim ized ratio(m(1μm copper powders):m(15μm copper powders):m(glass powders):m(organic solvent)=12~15:52~61:7~13:15~25) shows the good electrical conductivity(12.62mΩ/□)and bonding strength(1 grade).5. The sheet resistance of copper film using the best process parameters is 12.62mΩ/□,the change rate is only 42% after half year at room temperature and the glass powder holding at 500℃ for 1 hour shows no devitrification,which presented the good ageing-resistant performance.