Reliability of Microsoldered Thin Copper-lead by Low Melting Point Au/Sn Microsoldering: A Study on Microjoining of Leadframe for LSI Package (No.5)

This report considers the low melting point Au-Sn microsoldering (utilizing the Au 10 mass %-Sn eutectic ; melting point/ 490 K, bonding heat tool temperature/523 K and bonding time/5 s) which is applied to the 400-600 pin count and 0.10-0.15 mm lead pitch connection with 0.018 mmt thin copper lead. This method is performed by heat and press tool gang bonding of tin electroplated (3.5, μ mthick) copper pattern on substrate and gold electroplated (0.5, μm thick) thin copper lead with non flux in air. Au-Sn microsoldered layer has the high peel strength and has the high reliability in 218 K×30 min-423 K×30 min temperature cycle test and 423 K storage test in air that is higher than 37 mass % Pb-Sn microsoldering. As a result of this reserch, it is determined that the low melting point Au-Sn microsoldering is an excellent method for thin copper lead micro connection to the copper pattern routed substrate and the board.