Lead-free cleaning: moving from eutectic to lead-free

The industry is intensively developing solder-paste systems that serve as an alternative to the tin/lead (SnPb) solder paste used. But switching to lead-free paste will increase the need for chemically supported cleaning.

As of july 1, 2006, the weee directive will eliminate the use of lead in solder paste. The industry is intensively developing solder-paste systems that serve as an alternative to the tin/lead (SnPb) solder paste used. But switching to lead-free paste will increase the need for chemically supported cleaning.

As early as the 1950s, electronic circuit failures were documented due mainly to electrochemical migration of solder connections containing silver. Because of the low silver concentration, the dendrites caused by electrochemical migration (EM) cannot be determined via discontinues in resistance measurements (Figure 1). Temporary failure, however, may occur during the measurement period. The high affinity of silver used to form silver hydroxides and sulfides, respectively, is the reason for the increase in EM (Figure 2). The larger quantities of activators, which tend to be highly hygroscopic in character, are required due to increased reflow temperatures. 

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