| With the rapid development of microelectronic technology, the trend of mi-cro-electronic components to micromation, integration and high frequency were increased by the need of electronic machine in miniaturization, portable-style, multifunction, digital-way and high reliability as well as high-performance. It c-ould not meet the requirements of small, thin and light performance by DBC method. Copper laminates were changed with screen printing paste. The small, thin and high density ceramic heat sink would be produced by screen printing paste, which improving the wiring density of surface mount technology.Copper paste were prepared with copper metal powders, glass powders an-d organic carriers by three-rolling mill. According to the adhesion mechanism of glass binder and conductive mechanism of copper paste, the preparation tech-nics and conductive mechanism of copper paste as well as the relationship bet-ween composition and performance of copper paste were studied respectively i-n this paper. Then conclusions were got as following:(1) Non-agglomerated monodispersed spheric ultra-fine copper metallic po-wders, which were fine and confined in particle size and distribution, were syn-thesized with multi-reducers by two-step reduction of chemical reduction meth-od. They were suitable for the conductive phase of copper paste. The optimal formula and process conditions were as follows:the optimal formula and proce-ss conditions were as follows:concentration of bluestone:1mol/L; concentratio-n of sodium hydroxide:2.5mol/L; concentration of prereduction glucose:3mol/ L; temperature of pre-reduction was 60℃; time of pre-reduction: 30min, disper-sant a little; multi-reduction of hydrazine hydrate and formaldehyde(ratio of ma-ss was 1:1.6); temperature of the second stage of reduction:60℃; time of the second stage of reduction: 20min; protective agent of Antioxidant:1.0～1.5g/L. The preparation technics of ultra-copper powders showed that reaction temperat-ure, reducers, concentration of reducers, dispersant and protective agent were i-mportant factors for the influence to performance of ultra-copper powders. (2) Organic carrier which was suitable for screen printing were prepared a-nd its optimal formula and process conditions were as follows:ethyl cellulose: 8wt.%; Tributyl Citrate:12wt.%; butyl alcohol topiramate carbazole:21wt.%; t-erpineol:57wt.%; other additives: 2wt.%; leveling time:10min; drying time:5 min; Sintering temperature:830～870℃; Sintering time:20min. The preparation technics of organic carrier implied that the volatilization of organic solvents det-ermined the performance of organic carrier and the leveling time, drying time as well as sintering time were important factors for affecting the printing perfo-rmance.(3) Glass powders which were useful as the glass binder for copper paste were obtained by melting with the determination of their viscosity, softening t-emperatures and micro-structures. The glass prescription was (wt%)40SiO2-31 Bi2O3-5B2O3-3Al2O3-5TiO2-3CaO-4SrO-5Na2O-5K2O.(4) The best formula of preparation of copper paste was as follows:ultra-fine copper:70wt.%; Bi2O3: 3wt.%; B6 glass powder: 5wt.%; organic carrier: 2 2wt.%. The performance of copper conductive film was as follows:adhesion w-as 20N/mm2 and sheet resistance was 3.2Ω/□.The immersion experiments of glass glaze film showed that the glass gla-ze film made by B6 glass in the electroless nickel plating solution could be r-esistant to corrosion for 16h. The immersion experiments of copper thick film made by B6 showed that the gap appeared between the film and substrate, an-d their mutual adhesion were decreased evidently. |
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