Fluxless Chip Joining (Soldering) in Vacuum
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Interconnections between circuit components on a printed circuit board are typically formed by the use of a soldering process at temperatures in the range of 200oC to 365oC in normal atmosphere. A major problem which arises in this soldering is the tarnishing (oxidation contamination) of copper. Although flux may be used to offset this problem the use of flux creates other problems. The most serious problem is that of multiple small voids (MSVs) produced by outgassing. These MSVs have a profound impact on the thermal fatigue life of controlled collapse chip connector (C4) joints. A soldering technique which prevents oxidation and subsequent occurrence of MSVs due to fluxing is accomplished by soldering in a vacuum, without flux, in the following manner.