Optimization of brazing process for ceramic package

When the leadframe made of 4J42 alloy is brazed to the brazing zone of an alumina substrate using an AgCu28 filler in ceramic DIP production, the liquid filler often flows onto the surface of the leadframe after brazing, and the quality of finished products is influenced greatly. These problems are related to improper brazing process for ceramic package. The effects of brazing temperature, hold time and filler quantity on the flow of an AgCu28 filler were studied under factory and laboratory conditions. The results showed that the flow of the AgCu28 filler mostly depends on the hold time at the temperature above the melting point. Three optimum brazing processes in which the flow of the filler could be avoid were found:firstly held at 700℃ for 5 min and then held at 800℃ for 4 min, secondly held at 900℃ for 10 min, and in the last process, the graphite boats passed through the zone of 810℃ at the speed of a boat every 4 min in the manual way or the hold time at the temperature above the melting point is limited in 5 min by adjusting the belt speed of the conveyer-type continuous furnace.