Low temperature controlled collapse chip attach process.

摘要

A controlled collapse chip connect method of joining an IC chip to a microelectronic circuit card. According to the method an inhomogeneous, anisotropic column (33) of solder is deposited from a Pb/Sn alloy onto solder wettable I/O terminals of the I/C chip (10), without subsequent homogenizing reflow. The solder core has a Pb rich core (35) and an Sn rich cap (37). The matching footprint of the solder wettable I/O terminals on the microelectronic circuit card is substantially free of deposited solder and presents a protected Cu surface to the solder columns, or, at most a surface of Cu and anti-oxidant. The chip is aligned with the corresponding footprints on the microelectronic circuit card, and the solder is reflowed to bond the chip to the microelectronic circuit card.