A method and structure for a 
solder interconnection, using solder balls for making a low temperature 
chip attachment directly to any of the higher levels of packaging substrate is disclosed. After a 
solder ball has been formed using 
standard methods it is reflowed to give the 
solder ball a 
smooth surface. A layer of 
low melting point metal, such as, 
bismuth, 
indium or 
tin, preferably, pure 
tin, is deposited on the top of the solder balls. This structure results in localizing of the eutectic 
alloy, formed upon subsequent low temperature joining cycle, to the top of the high melting 
solder ball even after multiple low temperature reflow cycles. This method does not need 
tinning of the substrate to which the 
chip is to be joined, which makes this method economical. It has also been noticed that whenever temperature is raised slightly above the eutectic temperature, the structure always forms a liquid fillet around the joint with 
copper wires. This liquid fillet formation results in substantial 
thermal fatigue life improvement for reduced stress at interface; and secondly, provides an easy means to remove 
chip for the purpose of chip burn-in, replacement or field repairs.