Thick Copper Conductor Paste Prepared With Organic Carrier

The high conductivity of the ceramic heat sink with small size, high density and high thermal conductivity of complex circuits were be prepared by using thick film technology. Copper conductor paste to meet the technical requirements of the ceramic heat sink. Therefore, research on the heat sink with copper paste has a great practical value and better economic efficiency.The carrier of copper based electrical conductive paste was reviewed. The slurry preparation process of the copper powder conductive filler, glass and a mixed solvent of an organic carrier electronic were studied respectively in this paper. The conductive copper film was prepared by multiple screen printing process with sintering in a nitrogen atmosphere. Using copper powder as the conductive phase, comparative studies are carried out, with respect to viscosity, thixotropy, adhesion, square resistance, on the paste with different mixed solvent organic carriers volatilizing, leveling and formulas. The performance of copper paste and copper conductor film were tested, the ceramic heat sink of thicher copper conductor paste was preparaed. The following results are obtained:(1) Using ethyl cellulose-terpineol-castor oil, ethyl cellulose-terpineol-castor oil as the organic carrier, the preparation of the leveling of the copper paste and solvent evaporation characteristics closely related. With ethyl cellulose-terpineol-castor oil mixed solvents for organic carrier, this organic carrier has a hierarchy of evaporation characteristics. Due to the flow of the slurry level is excellent and the surface of the fired film is smooth, flat.(2) Organic carrier which was suitable for screen printing was prepared and its optimal formula and Process conditions were as follows:ethyl cellulose:8wt.%; terpineol:57%; butyl alcohol acetic acid ester:23%; dibutyl phthalate:10%; oleum ricini:0.5%; polyamide wax:0.5%; other additives:1%; levelingtime:8min; dryingtime:5min; Sinteringtem peratuxe:820～850℃; Sinieringtime:30min. The preparation techniques of organic carrier implied that the volatilization of organic solvents determined the performance of organic carrier and the leveling times, drying time as well as sintering time were important factors for affecting the printing performance.(3) Copper powder conductive paste is prepared by multiple screen printing process, copper slurry film thickness is only about10-15μm after one time printing of drying, sintering; Copper slurry film thickness is more than25μm after two time printing of drying, sintering; Copper slurry film thickness is more than45μm after more than three time printing of drying, sintering. The film thickness to meet the requirements of the heat sink copper conductive film.(4) The best formula of preparation of copper paste was as follows:Ultrafine copper:76wt.%; glass powder:4wt.%; organiecarrier:20wt.%. The performance of copper conductive film was as follows:adhesion was15N/mm2, sheet resistance was3.1mΩ/□and film thickness was about45-50μm.