SMOKELESS SOLDER STRUCTURE FOR ELECTRONIC PACKAGE CONNECTION AND FORMING METHOD THEREOF, FOR REDUCING EXPANSION OF SOLDER CONNECTION

摘要

PURPOSE: A smokeless solder structure for electronic package connection and a forming method thereof are provided to secure a smokeless solder-hierarchical structure for electronic packaging. CONSTITUTION: In a smokeless solder structure for electronic package connection, electronic package has a liquidus line temperature layer of solder connection, to restrict a fusion range of C4(Controlled Collapse Chip Connection) solder connection during second level joining/assembling and reprocessing work. The solder layer utilizes Sn/Ag and Sn/Cu non-eutectic solder alloys having high liquidus line temperature, for the solder connection of a first level. The solder layer adopts Sn/Ag and Sn/Cu non-eutectic solder alloys having low liquidus line temperature, for the solder connection of a second level. In joining/assembling a chip carrier(90) of the second level to a PCB(Printed Circuit Board,120), the C4 of an electronic circuit chip(10) to the chip carrier is not completely fused. Non-eutectic smokeless solder compositions(80,140) include intermetallic compounds comprising 52.0¯95.0 weight percent of Sn and 48.0¯5.0 weight percent of Ag. The fusion temperature of the intermetallic compound is higher than 250 degrees Centigrade.